Cosmin Truta | a40189c | 2019-04-14 14:10:32 -0400 | [diff] [blame] | 1 | .TH LIBPNG 3 "April 14, 2019" |
Glenn Randers-Pehrson | 0f881d6 | 1998-02-07 10:20:57 -0600 | [diff] [blame] | 2 | .SH NAME |
Cosmin Truta | a40189c | 2019-04-14 14:10:32 -0400 | [diff] [blame] | 3 | libpng \- Portable Network Graphics (PNG) Reference Library 1.6.37 |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4 | |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 5 | .SH SYNOPSIS |
| 6 | \fB#include <png.h>\fP |
| 7 | |
| 8 | \fBpng_uint_32 png_access_version_number (void);\fP |
Glenn Randers-Pehrson | 1ef65b6 | 2000-05-12 06:19:53 -0500 | [diff] [blame] | 9 | |
Glenn Randers-Pehrson | 6bc53be | 2006-06-16 07:52:03 -0500 | [diff] [blame] | 10 | \fBvoid png_benign_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP |
| 11 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 12 | \fBvoid png_build_grayscale_palette (int \fP\fIbit_depth\fP\fB, png_colorp \fIpalette\fP\fB);\fP |
| 13 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 14 | \fBpng_voidp png_calloc (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP |
| 15 | |
Glenn Randers-Pehrson | 6bc53be | 2006-06-16 07:52:03 -0500 | [diff] [blame] | 16 | \fBvoid png_chunk_benign_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP |
| 17 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 18 | \fBvoid png_chunk_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 19 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 20 | \fBvoid png_chunk_warning (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fImessage\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 21 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 22 | \fBvoid png_convert_from_struct_tm (png_timep \fP\fIptime\fP\fB, struct tm FAR * \fIttime\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 23 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 24 | \fBvoid png_convert_from_time_t (png_timep \fP\fIptime\fP\fB, time_t \fIttime\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 25 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 26 | \fBpng_charp png_convert_to_rfc1123 (png_structp \fP\fIpng_ptr\fP\fB, png_timep \fIptime\fP\fB);\fP |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 27 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 28 | \fBpng_infop png_create_info_struct (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 29 | |
Glenn Randers-Pehrson | 5e5c1e1 | 2000-11-10 12:26:19 -0600 | [diff] [blame] | 30 | \fBpng_structp png_create_read_struct (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarn_fn\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 31 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 32 | \fBpng_structp png_create_read_struct_2 (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 33 | |
Glenn Randers-Pehrson | 5e5c1e1 | 2000-11-10 12:26:19 -0600 | [diff] [blame] | 34 | \fBpng_structp png_create_write_struct (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarn_fn\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 35 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 36 | \fBpng_structp png_create_write_struct_2 (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP |
| 37 | |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 38 | \fBvoid png_data_freer (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIfreer\fP\fB, png_uint_32 \fImask\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 39 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 40 | \fBvoid png_destroy_info_struct (png_structp \fP\fIpng_ptr\fP\fB, png_infopp \fIinfo_ptr_ptr\fP\fB);\fP |
| 41 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 42 | \fBvoid png_destroy_read_struct (png_structpp \fP\fIpng_ptr_ptr\fP\fB, png_infopp \fP\fIinfo_ptr_ptr\fP\fB, png_infopp \fIend_info_ptr_ptr\fP\fB);\fP |
| 43 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 44 | \fBvoid png_destroy_write_struct (png_structpp \fP\fIpng_ptr_ptr\fP\fB, png_infopp \fIinfo_ptr_ptr\fP\fB);\fP |
| 45 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 46 | \fBvoid png_err (png_structp \fIpng_ptr\fP\fB);\fP |
| 47 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 48 | \fBvoid png_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP |
| 49 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 50 | \fBvoid png_free (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP |
| 51 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 52 | \fBvoid png_free_chunk_list (png_structp \fIpng_ptr\fP\fB);\fP |
| 53 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 54 | \fBvoid png_free_default (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 55 | |
Glenn Randers-Pehrson | a77ef62 | 2000-02-18 13:48:52 -0600 | [diff] [blame] | 56 | \fBvoid png_free_data (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fInum\fP\fB);\fP |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 57 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 58 | \fBpng_byte png_get_bit_depth (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 59 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 60 | \fBpng_uint_32 png_get_bKGD (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_16p \fI*background\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 61 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 62 | \fBpng_byte png_get_channels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 63 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 64 | \fBpng_uint_32 png_get_cHRM (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, double \fP\fI*white_x\fP\fB, double \fP\fI*white_y\fP\fB, double \fP\fI*red_x\fP\fB, double \fP\fI*red_y\fP\fB, double \fP\fI*green_x\fP\fB, double \fP\fI*green_y\fP\fB, double \fP\fI*blue_x\fP\fB, double \fI*blue_y\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 65 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 66 | \fBpng_uint_32 png_get_cHRM_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*white_x\fP\fB, png_uint_32 \fP\fI*white_y\fP\fB, png_uint_32 \fP\fI*red_x\fP\fB, png_uint_32 \fP\fI*red_y\fP\fB, png_uint_32 \fP\fI*green_x\fP\fB, png_uint_32 \fP\fI*green_y\fP\fB, png_uint_32 \fP\fI*blue_x\fP\fB, png_uint_32 \fI*blue_y\fP\fB);\fP |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 67 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 68 | \fBpng_uint_32 png_get_cHRM_XYZ (png_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, double \fP\fI*red_X\fP\fB, double \fP\fI*red_Y\fP\fB, double \fP\fI*red_Z\fP\fB, double \fP\fI*green_X\fP\fB, double \fP\fI*green_Y\fP\fB, double \fP\fI*green_Z\fP\fB, double \fP\fI*blue_X\fP\fB, double \fP\fI*blue_Y\fP\fB, double \fI*blue_Z\fP\fB);\fP |
Glenn Randers-Pehrson | ad81d71 | 2009-07-30 15:39:00 -0500 | [diff] [blame] | 69 | |
John Bowler | 736f40f | 2011-08-25 16:19:44 -0500 | [diff] [blame] | 70 | \fBpng_uint_32 png_get_cHRM_XYZ_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_fixed_point \fP\fI*int_red_X\fP\fB, png_fixed_point \fP\fI*int_red_Y\fP\fB, png_fixed_point \fP\fI*int_red_Z\fP\fB, png_fixed_point \fP\fI*int_green_X\fP\fB, png_fixed_point \fP\fI*int_green_Y\fP\fB, png_fixed_point \fP\fI*int_green_Z\fP\fB, png_fixed_point \fP\fI*int_blue_X\fP\fB, png_fixed_point \fP\fI*int_blue_Y\fP\fB, png_fixed_point \fI*int_blue_Z\fP\fB);\fP |
| 71 | |
John Bowler | 736f40f | 2011-08-25 16:19:44 -0500 | [diff] [blame] | 72 | \fBpng_uint_32 png_get_chunk_cache_max (png_const_structp \fIpng_ptr\fP\fB);\fP |
| 73 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 74 | \fBpng_alloc_size_t png_get_chunk_malloc_max (png_const_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 75 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 76 | \fBpng_byte png_get_color_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 77 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 78 | \fBpng_uint_32 png_get_compression_buffer_size (png_const_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 800d1e9 | 2008-08-20 17:25:21 -0500 | [diff] [blame] | 79 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 80 | \fBpng_byte png_get_compression_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 81 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 82 | \fBpng_byte png_get_copyright (png_const_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 83 | |
John Bowler | f19abd6 | 2011-01-22 18:29:24 -0600 | [diff] [blame] | 84 | \fBpng_uint_32 png_get_current_row_number \fI(png_const_structp\fP\fB);\fP |
| 85 | |
John Bowler | f19abd6 | 2011-01-22 18:29:24 -0600 | [diff] [blame] | 86 | \fBpng_byte png_get_current_pass_number \fI(png_const_structp\fP\fB);\fP |
| 87 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 88 | \fBpng_voidp png_get_error_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 89 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 90 | \fBpng_byte png_get_filter_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 91 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 92 | \fBpng_uint_32 png_get_gAMA (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, double \fI*file_gamma\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 93 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 94 | \fBpng_uint_32 png_get_gAMA_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fI*int_file_gamma\fP\fB);\fP |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 95 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 96 | \fBpng_byte png_get_header_ver (png_const_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 5379b24 | 1999-11-27 10:22:33 -0600 | [diff] [blame] | 97 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 98 | \fBpng_byte png_get_header_version (png_const_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 99 | |
Glenn Randers-Pehrson | 7c709f0 | 2017-08-02 16:48:11 -0500 | [diff] [blame] | 100 | \fBpng_uint_32 png_get_eXIf (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fI*exif\fP\fB);\fP |
| 101 | |
Glenn Randers-Pehrson | 554d440 | 2017-08-04 15:38:41 -0500 | [diff] [blame] | 102 | \fBpng_uint_32 png_get_eXIf_1 (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_unit_32 \fP\fI*num_exif\fP\fB, png_bytep \fI*exif\fP\fB);\fP |
| 103 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 104 | \fBpng_uint_32 png_get_hIST (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_16p \fI*hist\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 105 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 106 | \fBpng_uint_32 png_get_iCCP (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_charpp \fP\fIname\fP\fB, int \fP\fI*compression_type\fP\fB, png_bytepp \fP\fIprofile\fP\fB, png_uint_32 \fI*proflen\fP\fB);\fP |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 107 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 108 | \fBpng_uint_32 png_get_IHDR (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*width\fP\fB, png_uint_32 \fP\fI*height\fP\fB, int \fP\fI*bit_depth\fP\fB, int \fP\fI*color_type\fP\fB, int \fP\fI*interlace_type\fP\fB, int \fP\fI*compression_type\fP\fB, int \fI*filter_type\fP\fB);\fP |
| 109 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 110 | \fBpng_uint_32 png_get_image_height (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 111 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 112 | \fBpng_uint_32 png_get_image_width (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 113 | |
Glenn Randers-Pehrson | ad81d71 | 2009-07-30 15:39:00 -0500 | [diff] [blame] | 114 | \fBpng_int_32 png_get_int_32 (png_bytep \fIbuf\fP\fB);\fP |
| 115 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 116 | \fBpng_byte png_get_interlace_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 117 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 118 | \fBpng_uint_32 png_get_io_chunk_type (png_const_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a63dbed | 2011-01-22 08:51:19 -0600 | [diff] [blame] | 119 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 120 | \fBpng_voidp png_get_io_ptr (png_structp \fIpng_ptr\fP\fB);\fP |
| 121 | |
Glenn Randers-Pehrson | a63dbed | 2011-01-22 08:51:19 -0600 | [diff] [blame] | 122 | \fBpng_uint_32 png_get_io_state (png_structp \fIpng_ptr\fP\fB);\fP |
| 123 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 124 | \fBpng_byte png_get_libpng_ver (png_const_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 5379b24 | 1999-11-27 10:22:33 -0600 | [diff] [blame] | 125 | |
Glenn Randers-Pehrson | db8704e | 2015-07-13 16:03:37 -0500 | [diff] [blame] | 126 | \fBint png_get_palette_max(png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
| 127 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 128 | \fBpng_voidp png_get_mem_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 129 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 130 | \fBpng_uint_32 png_get_oFFs (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*offset_x\fP\fB, png_uint_32 \fP\fI*offset_y\fP\fB, int \fI*unit_type\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 131 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 132 | \fBpng_uint_32 png_get_pCAL (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fI*purpose\fP\fB, png_int_32 \fP\fI*X0\fP\fB, png_int_32 \fP\fI*X1\fP\fB, int \fP\fI*type\fP\fB, int \fP\fI*nparams\fP\fB, png_charp \fP\fI*units\fP\fB, png_charpp \fI*params\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 133 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 134 | \fBpng_uint_32 png_get_pHYs (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*res_x\fP\fB, png_uint_32 \fP\fI*res_y\fP\fB, int \fI*unit_type\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 135 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 136 | \fBfloat png_get_pixel_aspect_ratio (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 137 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 138 | \fBpng_uint_32 png_get_pHYs_dpi (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*res_x\fP\fB, png_uint_32 \fP\fI*res_y\fP\fB, int \fI*unit_type\fP\fB);\fP |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 139 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 140 | \fBpng_fixed_point png_get_pixel_aspect_ratio_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 141 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 142 | \fBpng_uint_32 png_get_pixels_per_inch (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 143 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 144 | \fBpng_uint_32 png_get_pixels_per_meter (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 145 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 146 | \fBpng_voidp png_get_progressive_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 147 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 148 | \fBpng_uint_32 png_get_PLTE (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_colorp \fP\fI*palette\fP\fB, int \fI*num_palette\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 149 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 150 | \fBpng_byte png_get_rgb_to_gray_status (png_const_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | e4f124e | 2012-12-09 19:20:34 -0600 | [diff] [blame] | 151 | |
| 152 | \fBpng_uint_32 png_get_rowbytes (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
| 153 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 154 | \fBpng_bytepp png_get_rows (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a77ef62 | 2000-02-18 13:48:52 -0600 | [diff] [blame] | 155 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 156 | \fBpng_uint_32 png_get_sBIT (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_8p \fI*sig_bit\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 157 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 158 | \fBvoid png_get_sCAL (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int* \fP\fIunit\fP\fB, double* \fP\fIwidth\fP\fB, double* \fIheight\fP\fB);\fP |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 159 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 160 | \fBvoid png_get_sCAL_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int* \fP\fIunit\fP\fB, png_fixed_pointp \fP\fIwidth\fP\fB, png_fixed_pointp \fIheight\fP\fB);\fP |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 161 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 162 | \fBvoid png_get_sCAL_s (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int* \fP\fIunit\fP\fB, png_charpp \fP\fIwidth\fP\fB, png_charpp \fIheight\fP\fB);\fP |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 163 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 164 | \fBpng_bytep png_get_signature (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 165 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 166 | \fBpng_uint_32 png_get_sPLT (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_spalette_p \fI*splt_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 167 | |
Glenn Randers-Pehrson | 8d0bc0f | 2011-01-25 22:15:58 -0600 | [diff] [blame] | 168 | \fBpng_uint_32 png_get_sRGB (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int \fI*file_srgb_intent\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 169 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 170 | \fBpng_uint_32 png_get_text (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_textp \fP\fI*text_ptr\fP\fB, int \fI*num_text\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 171 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 172 | \fBpng_uint_32 png_get_tIME (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fI*mod_time\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 173 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 174 | \fBpng_uint_32 png_get_tRNS (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fI*trans_alpha\fP\fB, int \fP\fI*num_trans\fP\fB, png_color_16p \fI*trans_color\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 175 | |
Glenn Randers-Pehrson | e4f124e | 2012-12-09 19:20:34 -0600 | [diff] [blame] | 176 | \fB/* This function is really an inline macro. \fI*/ |
Glenn Randers-Pehrson | b6bfd40 | 2012-12-19 16:06:56 -0600 | [diff] [blame] | 177 | |
Glenn Randers-Pehrson | e4f124e | 2012-12-09 19:20:34 -0600 | [diff] [blame] | 178 | \fBpng_uint_16 png_get_uint_16 (png_bytep \fIbuf\fP\fB);\fP |
| 179 | |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 180 | \fBpng_uint_32 png_get_uint_31 (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIbuf\fP\fB);\fP |
Glenn Randers-Pehrson | 7b34df3 | 2006-02-24 06:30:16 -0600 | [diff] [blame] | 181 | |
Glenn Randers-Pehrson | e4f124e | 2012-12-09 19:20:34 -0600 | [diff] [blame] | 182 | \fB/* This function is really an inline macro. \fI*/ |
Glenn Randers-Pehrson | b6bfd40 | 2012-12-19 16:06:56 -0600 | [diff] [blame] | 183 | |
Glenn Randers-Pehrson | e4f124e | 2012-12-09 19:20:34 -0600 | [diff] [blame] | 184 | \fBpng_uint_32 png_get_uint_32 (png_bytep \fIbuf\fP\fB);\fP |
| 185 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 186 | \fBpng_uint_32 png_get_unknown_chunks (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_unknown_chunkpp \fIunknowns\fP\fB);\fP |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 187 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 188 | \fBpng_voidp png_get_user_chunk_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 189 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 190 | \fBpng_uint_32 png_get_user_height_max (png_const_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 272489d | 2004-08-04 06:34:52 -0500 | [diff] [blame] | 191 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 192 | \fBpng_voidp png_get_user_transform_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 193 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 194 | \fBpng_uint_32 png_get_user_width_max (png_const_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 272489d | 2004-08-04 06:34:52 -0500 | [diff] [blame] | 195 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 196 | \fBpng_uint_32 png_get_valid (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fIflag\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 197 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 198 | \fBfloat png_get_x_offset_inches (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 199 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 200 | \fBpng_fixed_point png_get_x_offset_inches_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 201 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 202 | \fBpng_int_32 png_get_x_offset_microns (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 203 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 204 | \fBpng_int_32 png_get_x_offset_pixels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 205 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 206 | \fBpng_uint_32 png_get_x_pixels_per_inch (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 207 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 208 | \fBpng_uint_32 png_get_x_pixels_per_meter (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 209 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 210 | \fBfloat png_get_y_offset_inches (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 211 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 212 | \fBpng_fixed_point png_get_y_offset_inches_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 213 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 214 | \fBpng_int_32 png_get_y_offset_microns (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 215 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 216 | \fBpng_int_32 png_get_y_offset_pixels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 217 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 218 | \fBpng_uint_32 png_get_y_pixels_per_inch (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 219 | |
John Bowler | 0a5c9c0 | 2011-01-22 17:36:34 -0600 | [diff] [blame] | 220 | \fBpng_uint_32 png_get_y_pixels_per_meter (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 221 | |
Glenn Randers-Pehrson | c1bfe68 | 2002-03-06 22:08:00 -0600 | [diff] [blame] | 222 | \fBint png_handle_as_unknown (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIchunk_name\fP\fB);\fP |
| 223 | |
Glenn Randers-Pehrson | e0a6c06 | 2011-11-07 23:50:05 -0600 | [diff] [blame] | 224 | \fBint png_image_begin_read_from_file (png_imagep \fP\fIimage\fP\fB, const char \fI*file_name\fP\fB);\fP |
| 225 | |
Glenn Randers-Pehrson | e0a6c06 | 2011-11-07 23:50:05 -0600 | [diff] [blame] | 226 | \fBint png_image_begin_read_from_stdio (png_imagep \fP\fIimage\fP\fB, FILE* \fIfile\fP\fB);\fP |
| 227 | |
Cosmin Truta | a74aa9a | 2018-06-17 22:37:44 -0400 | [diff] [blame] | 228 | \fBint, png_image_begin_read_from_memory (png_imagep \fP\fIimage\fP\fB, png_const_voidp \fP\fImemory\fP\fB, size_t \fIsize\fP\fB);\fP |
Glenn Randers-Pehrson | e0a6c06 | 2011-11-07 23:50:05 -0600 | [diff] [blame] | 229 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 230 | \fBint png_image_finish_read (png_imagep \fP\fIimage\fP\fB, png_colorp \fP\fIbackground\fP\fB, void \fP\fI*buffer\fP\fB, png_int_32 \fP\fIrow_stride\fP\fB, void \fI*colormap\fP\fB);\fP |
Glenn Randers-Pehrson | e0a6c06 | 2011-11-07 23:50:05 -0600 | [diff] [blame] | 231 | |
Glenn Randers-Pehrson | e0a6c06 | 2011-11-07 23:50:05 -0600 | [diff] [blame] | 232 | \fBvoid png_image_free (png_imagep \fIimage\fP\fB);\fP |
| 233 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 234 | \fBint png_image_write_to_file (png_imagep \fP\fIimage\fP\fB, const char \fP\fI*file\fP\fB, int \fP\fIconvert_to_8bit\fP\fB, const void \fP\fI*buffer\fP\fB, png_int_32 \fP\fIrow_stride\fP\fB, void \fI*colormap\fP\fB);\fP |
Glenn Randers-Pehrson | cc02f89 | 2012-08-29 14:03:09 -0500 | [diff] [blame] | 235 | |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 236 | \fBint png_image_write_to_memory (png_imagep \fP\fIimage\fP\fB, void \fP\fI*memory\fP\fB, png_alloc_size_t * PNG_RESTRICT \fP\fImemory_bytes\fP\fB, int \fP\fIconvert_to_8_bit\fP\fB, const void \fP\fI*buffer\fP\fB, png_int_32 \fP\fIrow_stride\fP\fB, const void \fI*colormap\fP\fB);\fP |
Glenn Randers-Pehrson | d2b8d46 | 2016-01-23 14:01:44 -0600 | [diff] [blame] | 237 | |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 238 | \fBint png_image_write_to_stdio (png_imagep \fP\fIimage\fP\fB, FILE \fP\fI*file\fP\fB, int \fP\fIconvert_to_8_bit\fP\fB, const void \fP\fI*buffer\fP\fB, png_int_32 \fP\fIrow_stride\fP\fB, void \fI*colormap\fP\fB);\fP |
Glenn Randers-Pehrson | e0a6c06 | 2011-11-07 23:50:05 -0600 | [diff] [blame] | 239 | |
Cosmin Truta | a74aa9a | 2018-06-17 22:37:44 -0400 | [diff] [blame] | 240 | \fBvoid png_info_init_3 (png_infopp \fP\fIinfo_ptr\fP\fB, size_t \fIpng_info_struct_size\fP\fB);\fP |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 241 | |
Glenn Randers-Pehrson | 8b6a889 | 2001-05-18 04:54:50 -0500 | [diff] [blame] | 242 | \fBvoid png_init_io (png_structp \fP\fIpng_ptr\fP\fB, FILE \fI*fp\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 243 | |
Glenn Randers-Pehrson | f98726a | 2010-02-19 09:54:53 -0600 | [diff] [blame] | 244 | \fBvoid png_longjmp (png_structp \fP\fIpng_ptr\fP\fB, int \fIval\fP\fB);\fP |
| 245 | |
Glenn Randers-Pehrson | beb572e | 2006-08-19 13:59:24 -0500 | [diff] [blame] | 246 | \fBpng_voidp png_malloc (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP |
Glenn Randers-Pehrson | 8b6a889 | 2001-05-18 04:54:50 -0500 | [diff] [blame] | 247 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 248 | \fBpng_voidp png_malloc_default (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP |
| 249 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 250 | \fBpng_voidp png_malloc_warn (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP |
| 251 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 252 | \fBpng_uint_32 png_permit_mng_features (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fImng_features_permitted\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 253 | |
Cosmin Truta | a74aa9a | 2018-06-17 22:37:44 -0400 | [diff] [blame] | 254 | \fBvoid png_process_data (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fIbuffer\fP\fB, size_t \fIbuffer_size\fP\fB);\fP |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 255 | |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 256 | \fBsize_t png_process_data_pause (png_structp \fP\fIpng_ptr\fP\fB, int \fIsave\fP\fB);\fP |
John Bowler | f19abd6 | 2011-01-22 18:29:24 -0600 | [diff] [blame] | 257 | |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 258 | \fBpng_uint_32 png_process_data_skip (png_structp \fP\fIpng_ptr\fP\fB);\fP |
John Bowler | f19abd6 | 2011-01-22 18:29:24 -0600 | [diff] [blame] | 259 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 260 | \fBvoid png_progressive_combine_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIold_row\fP\fB, png_bytep \fInew_row\fP\fB);\fP |
| 261 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 262 | \fBvoid png_read_end (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
| 263 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 264 | \fBvoid png_read_image (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fIimage\fP\fB);\fP |
| 265 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 266 | \fBvoid png_read_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
| 267 | |
Glenn Randers-Pehrson | 5e5c1e1 | 2000-11-10 12:26:19 -0600 | [diff] [blame] | 268 | \fBvoid png_read_png (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fItransforms\fP\fB, png_voidp \fIparams\fP\fB);\fP |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 269 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 270 | \fBvoid png_read_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIrow\fP\fB, png_bytep \fIdisplay_row\fP\fB);\fP |
| 271 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 272 | \fBvoid png_read_rows (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fP\fIrow\fP\fB, png_bytepp \fP\fIdisplay_row\fP\fB, png_uint_32 \fInum_rows\fP\fB);\fP |
| 273 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 274 | \fBvoid png_read_update_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
| 275 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 276 | \fBint png_reset_zstream (png_structp \fIpng_ptr\fP\fB);\fP |
| 277 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 278 | \fBvoid png_save_int_32 (png_bytep \fP\fIbuf\fP\fB, png_int_32 \fIi\fP\fB);\fP |
Glenn Randers-Pehrson | ad81d71 | 2009-07-30 15:39:00 -0500 | [diff] [blame] | 279 | |
Glenn Randers-Pehrson | 7b34df3 | 2006-02-24 06:30:16 -0600 | [diff] [blame] | 280 | \fBvoid png_save_uint_16 (png_bytep \fP\fIbuf\fP\fB, unsigned int \fIi\fP\fB);\fP |
| 281 | |
Glenn Randers-Pehrson | 7b34df3 | 2006-02-24 06:30:16 -0600 | [diff] [blame] | 282 | \fBvoid png_save_uint_32 (png_bytep \fP\fIbuf\fP\fB, png_uint_32 \fIi\fP\fB);\fP |
| 283 | |
Glenn Randers-Pehrson | e4f124e | 2012-12-09 19:20:34 -0600 | [diff] [blame] | 284 | \fBvoid png_set_add_alpha (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIfiller\fP\fB, int \fIflags\fP\fB);\fP |
| 285 | |
Glenn Randers-Pehrson | e4f124e | 2012-12-09 19:20:34 -0600 | [diff] [blame] | 286 | \fBvoid png_set_alpha_mode (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fImode\fP\fB, double \fIoutput_gamma\fP\fB);\fP |
| 287 | |
Glenn Randers-Pehrson | e4f124e | 2012-12-09 19:20:34 -0600 | [diff] [blame] | 288 | \fBvoid png_set_alpha_mode_fixed (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fImode\fP\fB, png_fixed_point \fIoutput_gamma\fP\fB);\fP |
| 289 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 290 | \fBvoid png_set_background (png_structp \fP\fIpng_ptr\fP\fB, png_color_16p \fP\fIbackground_color\fP\fB, int \fP\fIbackground_gamma_code\fP\fB, int \fP\fIneed_expand\fP\fB, double \fIbackground_gamma\fP\fB);\fP |
| 291 | |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 292 | \fBvoid png_set_background_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_color_16p \fP\fIbackground_color\fP\fB, int \fP\fIbackground_gamma_code\fP\fB, int \fP\fIneed_expand\fP\fB, png_uint_32 \fIbackground_gamma\fP\fB);\fP |
| 293 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 294 | \fBvoid png_set_benign_errors (png_structp \fP\fIpng_ptr\fP\fB, int \fIallowed\fP\fB);\fP |
| 295 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 296 | \fBvoid png_set_bgr (png_structp \fIpng_ptr\fP\fB);\fP |
| 297 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 298 | \fBvoid png_set_bKGD (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_16p \fIbackground\fP\fB);\fP |
| 299 | |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 300 | \fBvoid png_set_check_for_invalid_index (png_structrp \fP\fIpng_ptr\fP\fB, int \fIallowed\fP\fB);\fP |
Glenn Randers-Pehrson | 434801a | 2012-03-02 22:38:50 -0600 | [diff] [blame] | 301 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 302 | \fBvoid png_set_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fP\fIwhite_x\fP\fB, double \fP\fIwhite_y\fP\fB, double \fP\fIred_x\fP\fB, double \fP\fIred_y\fP\fB, double \fP\fIgreen_x\fP\fB, double \fP\fIgreen_y\fP\fB, double \fP\fIblue_x\fP\fB, double \fIblue_y\fP\fB);\fP |
| 303 | |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 304 | \fBvoid png_set_cHRM_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIwhite_x\fP\fB, png_uint_32 \fP\fIwhite_y\fP\fB, png_uint_32 \fP\fIred_x\fP\fB, png_uint_32 \fP\fIred_y\fP\fB, png_uint_32 \fP\fIgreen_x\fP\fB, png_uint_32 \fP\fIgreen_y\fP\fB, png_uint_32 \fP\fIblue_x\fP\fB, png_uint_32 \fIblue_y\fP\fB);\fP |
| 305 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 306 | \fBvoid png_set_cHRM_XYZ (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fP\fIred_X\fP\fB, double \fP\fIred_Y\fP\fB, double \fP\fIred_Z\fP\fB, double \fP\fIgreen_X\fP\fB, double \fP\fIgreen_Y\fP\fB, double \fP\fIgreen_Z\fP\fB, double \fP\fIblue_X\fP\fB, double \fP\fIblue_Y\fP\fB, double \fIblue_Z\fP\fB);\fP |
John Bowler | 736f40f | 2011-08-25 16:19:44 -0500 | [diff] [blame] | 307 | |
| 308 | \fBvoid png_set_cHRM_XYZ_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_fixed_point \fP\fIint_red_X\fP\fB, png_fixed_point \fP\fIint_red_Y\fP\fB, png_fixed_point \fP\fIint_red_Z\fP\fB, png_fixed_point \fP\fIint_green_X\fP\fB, png_fixed_point \fP\fIint_green_Y\fP\fB, png_fixed_point \fP\fIint_green_Z\fP\fB, png_fixed_point \fP\fIint_blue_X\fP\fB, png_fixed_point \fP\fIint_blue_Y\fP\fB, png_fixed_point \fIint_blue_Z\fP\fB);\fP |
| 309 | |
Glenn Randers-Pehrson | 800d1e9 | 2008-08-20 17:25:21 -0500 | [diff] [blame] | 310 | \fBvoid png_set_chunk_cache_max (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIuser_chunk_cache_max\fP\fB);\fP |
| 311 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 312 | \fBvoid png_set_compression_level (png_structp \fP\fIpng_ptr\fP\fB, int \fIlevel\fP\fB);\fP |
| 313 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 314 | \fBvoid png_set_compression_mem_level (png_structp \fP\fIpng_ptr\fP\fB, int \fImem_level\fP\fB);\fP |
| 315 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 316 | \fBvoid png_set_compression_method (png_structp \fP\fIpng_ptr\fP\fB, int \fImethod\fP\fB);\fP |
| 317 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 318 | \fBvoid png_set_compression_strategy (png_structp \fP\fIpng_ptr\fP\fB, int \fIstrategy\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 319 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 320 | \fBvoid png_set_compression_window_bits (png_structp \fP\fIpng_ptr\fP\fB, int \fIwindow_bits\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 321 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 322 | \fBvoid png_set_crc_action (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIcrit_action\fP\fB, int \fIancil_action\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 323 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 324 | \fBvoid png_set_error_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarning_fn\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 325 | |
Glenn Randers-Pehrson | d08b6bd | 2011-02-19 15:50:17 -0600 | [diff] [blame] | 326 | \fBvoid png_set_expand (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | c85f5f6 | 2011-02-13 05:56:07 -0600 | [diff] [blame] | 327 | |
Glenn Randers-Pehrson | d08b6bd | 2011-02-19 15:50:17 -0600 | [diff] [blame] | 328 | \fBvoid png_set_expand_16 (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 329 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 330 | \fBvoid png_set_expand_gray_1_2_4_to_8 (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | 1ce0836 | 2006-03-08 23:35:59 -0600 | [diff] [blame] | 331 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 332 | \fBvoid png_set_filler (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIfiller\fP\fB, int \fIflags\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 333 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 334 | \fBvoid png_set_filter (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fImethod\fP\fB, int \fIfilters\fP\fB);\fP |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 335 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 336 | \fBvoid png_set_filter_heuristics (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIheuristic_method\fP\fB, int \fP\fInum_weights\fP\fB, png_doublep \fP\fIfilter_weights\fP\fB, png_doublep \fIfilter_costs\fP\fB);\fP |
Glenn Randers-Pehrson | f7d1a17 | 1998-06-06 15:31:35 -0500 | [diff] [blame] | 337 | |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 338 | \fBvoid png_set_filter_heuristics_fixed (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIheuristic_method\fP\fB, int \fP\fInum_weights\fP\fB, png_fixed_point_p \fP\fIfilter_weights\fP\fB, png_fixed_point_p \fIfilter_costs\fP\fB);\fP |
| 339 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 340 | \fBvoid png_set_flush (png_structp \fP\fIpng_ptr\fP\fB, int \fInrows\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 341 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 342 | \fBvoid png_set_gamma (png_structp \fP\fIpng_ptr\fP\fB, double \fP\fIscreen_gamma\fP\fB, double \fIdefault_file_gamma\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 343 | |
Glenn Randers-Pehrson | e4f124e | 2012-12-09 19:20:34 -0600 | [diff] [blame] | 344 | \fBvoid png_set_gamma_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIscreen_gamma\fP\fB, png_uint_32 \fIdefault_file_gamma\fP\fB);\fP |
| 345 | |
Glenn Randers-Pehrson | e4f124e | 2012-12-09 19:20:34 -0600 | [diff] [blame] | 346 | \fBvoid png_set_gAMA (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fIfile_gamma\fP\fB);\fP |
| 347 | |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 348 | \fBvoid png_set_gAMA_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fIfile_gamma\fP\fB);\fP |
| 349 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 350 | \fBvoid png_set_gray_1_2_4_to_8 (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 351 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 352 | \fBvoid png_set_gray_to_rgb (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 353 | |
Glenn Randers-Pehrson | 7c709f0 | 2017-08-02 16:48:11 -0500 | [diff] [blame] | 354 | \fBvoid png_set_eXIf (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fIexif\fP\fB);\fP |
| 355 | |
Cosmin Truta | ceb3277 | 2018-08-18 22:47:16 -0400 | [diff] [blame] | 356 | \fBvoid png_set_eXIf_1 (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fInum_exif\fP\fB, png_bytep \fIexif\fP\fB);\fP |
Glenn Randers-Pehrson | 554d440 | 2017-08-04 15:38:41 -0500 | [diff] [blame] | 357 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 358 | \fBvoid png_set_hIST (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_16p \fIhist\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 359 | |
Glenn Randers-Pehrson | 4a5a1ec | 2011-01-15 11:43:28 -0600 | [diff] [blame] | 360 | \fBvoid png_set_iCCP (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_const_charp \fP\fIname\fP\fB, int \fP\fIcompression_type\fP\fB, png_const_bytep \fP\fIprofile\fP\fB, png_uint_32 \fIproflen\fP\fB);\fP |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 361 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 362 | \fBint png_set_interlace_handling (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 363 | |
Glenn Randers-Pehrson | fc4a143 | 2000-05-17 17:39:34 -0500 | [diff] [blame] | 364 | \fBvoid png_set_invalid (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fImask\fP\fB);\fP |
| 365 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 366 | \fBvoid png_set_invert_alpha (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 367 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 368 | \fBvoid png_set_invert_mono (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 369 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 370 | \fBvoid png_set_IHDR (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIwidth\fP\fB, png_uint_32 \fP\fIheight\fP\fB, int \fP\fIbit_depth\fP\fB, int \fP\fIcolor_type\fP\fB, int \fP\fIinterlace_type\fP\fB, int \fP\fIcompression_type\fP\fB, int \fIfilter_type\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 371 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 372 | \fBvoid png_set_keep_unknown_chunks (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIkeep\fP\fB, png_bytep \fP\fIchunk_list\fP\fB, int \fInum_chunks\fP\fB);\fP |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 373 | |
Glenn Randers-Pehrson | 1e6ed73 | 2009-11-20 22:06:56 -0600 | [diff] [blame] | 374 | \fBjmp_buf* png_set_longjmp_fn (png_structp \fP\fIpng_ptr\fP\fB, png_longjmp_ptr \fP\fIlongjmp_fn\fP\fB, size_t \fIjmp_buf_size\fP\fB);\fP |
| 375 | |
Glenn Randers-Pehrson | e3f3c4e | 2010-02-07 18:08:50 -0600 | [diff] [blame] | 376 | \fBvoid png_set_chunk_malloc_max (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIuser_chunk_cache_max\fP\fB);\fP |
| 377 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 378 | \fBvoid png_set_compression_buffer_size (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP |
| 379 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 380 | \fBvoid png_set_mem_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 381 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 382 | \fBvoid png_set_oFFs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIoffset_x\fP\fB, png_uint_32 \fP\fIoffset_y\fP\fB, int \fIunit_type\fP\fB);\fP |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 383 | |
Glenn Randers-Pehrson | db8704e | 2015-07-13 16:03:37 -0500 | [diff] [blame] | 384 | \fBint png_set_option(png_structrp \fP\fIpng_ptr\fP\fB, int \fP\fIoption\fP\fB, int \fIonoff\fP\fB);\fP |
| 385 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 386 | \fBvoid png_set_packing (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 387 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 388 | \fBvoid png_set_packswap (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 389 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 390 | \fBvoid png_set_palette_to_rgb (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 391 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 392 | \fBvoid png_set_pCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fIpurpose\fP\fB, png_int_32 \fP\fIX0\fP\fB, png_int_32 \fP\fIX1\fP\fB, int \fP\fItype\fP\fB, int \fP\fInparams\fP\fB, png_charp \fP\fIunits\fP\fB, png_charpp \fIparams\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 393 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 394 | \fBvoid png_set_pHYs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIres_x\fP\fB, png_uint_32 \fP\fIres_y\fP\fB, int \fIunit_type\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 395 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 396 | \fBvoid png_set_progressive_read_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIprogressive_ptr\fP\fB, png_progressive_info_ptr \fP\fIinfo_fn\fP\fB, png_progressive_row_ptr \fP\fIrow_fn\fP\fB, png_progressive_end_ptr \fIend_fn\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 397 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 398 | \fBvoid png_set_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_colorp \fP\fIpalette\fP\fB, int \fInum_palette\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 399 | |
Glenn Randers-Pehrson | 3cd7cff | 2010-04-16 19:27:08 -0500 | [diff] [blame] | 400 | \fBvoid png_set_quantize (png_structp \fP\fIpng_ptr\fP\fB, png_colorp \fP\fIpalette\fP\fB, int \fP\fInum_palette\fP\fB, int \fP\fImaximum_colors\fP\fB, png_uint_16p \fP\fIhistogram\fP\fB, int \fIfull_quantize\fP\fB);\fP |
| 401 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 402 | \fBvoid png_set_read_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIio_ptr\fP\fB, png_rw_ptr \fIread_data_fn\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 403 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 404 | \fBvoid png_set_read_status_fn (png_structp \fP\fIpng_ptr\fP\fB, png_read_status_ptr \fIread_row_fn\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 405 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 406 | \fBvoid png_set_read_user_chunk_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIuser_chunk_ptr\fP\fB, png_user_chunk_ptr \fIread_user_chunk_fn\fP\fB);\fP |
| 407 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 408 | \fBvoid png_set_read_user_transform_fn (png_structp \fP\fIpng_ptr\fP\fB, png_user_transform_ptr \fIread_user_transform_fn\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 409 | |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 410 | \fBvoid png_set_rgb_to_gray (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIerror_action\fP\fB, double \fP\fIred\fP\fB, double \fIgreen\fP\fB);\fP |
| 411 | |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 412 | \fBvoid png_set_rgb_to_gray_fixed (png_structp \fP\fIpng_ptr\fP\fB, int error_action png_uint_32 \fP\fIred\fP\fB, png_uint_32 \fIgreen\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 413 | |
Glenn Randers-Pehrson | a77ef62 | 2000-02-18 13:48:52 -0600 | [diff] [blame] | 414 | \fBvoid png_set_rows (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytepp \fIrow_pointers\fP\fB);\fP |
| 415 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 416 | \fBvoid png_set_sBIT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_8p \fIsig_bit\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 417 | |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 418 | \fBvoid png_set_sCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIunit\fP\fB, double \fP\fIwidth\fP\fB, double \fIheight\fP\fB);\fP |
| 419 | |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 420 | \fBvoid png_set_sCAL_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIunit\fP\fB, png_fixed_point \fP\fIwidth\fP\fB, png_fixed_point \fIheight\fP\fB);\fP |
| 421 | |
Glenn Randers-Pehrson | e4f124e | 2012-12-09 19:20:34 -0600 | [diff] [blame] | 422 | \fBvoid png_set_sCAL_s (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIunit\fP\fB, png_charp \fP\fIwidth\fP\fB, png_charp \fIheight\fP\fB);\fP |
| 423 | |
Glenn Randers-Pehrson | e4f124e | 2012-12-09 19:20:34 -0600 | [diff] [blame] | 424 | \fBvoid png_set_scale_16 (png_structp \fIpng_ptr\fP\fB);\fP |
| 425 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 426 | \fBvoid png_set_shift (png_structp \fP\fIpng_ptr\fP\fB, png_color_8p \fItrue_bits\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 427 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 428 | \fBvoid png_set_sig_bytes (png_structp \fP\fIpng_ptr\fP\fB, int \fInum_bytes\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 429 | |
Glenn Randers-Pehrson | a77ef62 | 2000-02-18 13:48:52 -0600 | [diff] [blame] | 430 | \fBvoid png_set_sPLT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_spalette_p \fP\fIsplt_ptr\fP\fB, int \fInum_spalettes\fP\fB);\fP |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 431 | |
Glenn Randers-Pehrson | 8d0bc0f | 2011-01-25 22:15:58 -0600 | [diff] [blame] | 432 | \fBvoid png_set_sRGB (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIsrgb_intent\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 433 | |
Glenn Randers-Pehrson | 8d0bc0f | 2011-01-25 22:15:58 -0600 | [diff] [blame] | 434 | \fBvoid png_set_sRGB_gAMA_and_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIsrgb_intent\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 435 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 436 | \fBvoid png_set_strip_16 (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 437 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 438 | \fBvoid png_set_strip_alpha (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 439 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 440 | \fBvoid png_set_strip_error_numbers (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIstrip_mode\fP\fB);\fP |
| 441 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 442 | \fBvoid png_set_swap (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 443 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 444 | \fBvoid png_set_swap_alpha (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 445 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 446 | \fBvoid png_set_text (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_textp \fP\fItext_ptr\fP\fB, int \fInum_text\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 447 | |
Glenn Randers-Pehrson | 8eb8833 | 2011-04-01 00:16:50 -0500 | [diff] [blame] | 448 | \fBvoid png_set_text_compression_level (png_structp \fP\fIpng_ptr\fP\fB, int \fIlevel\fP\fB);\fP |
| 449 | |
Glenn Randers-Pehrson | 8eb8833 | 2011-04-01 00:16:50 -0500 | [diff] [blame] | 450 | \fBvoid png_set_text_compression_mem_level (png_structp \fP\fIpng_ptr\fP\fB, int \fImem_level\fP\fB);\fP |
| 451 | |
Glenn Randers-Pehrson | 8eb8833 | 2011-04-01 00:16:50 -0500 | [diff] [blame] | 452 | \fBvoid png_set_text_compression_strategy (png_structp \fP\fIpng_ptr\fP\fB, int \fIstrategy\fP\fB);\fP |
| 453 | |
Glenn Randers-Pehrson | 8eb8833 | 2011-04-01 00:16:50 -0500 | [diff] [blame] | 454 | \fBvoid png_set_text_compression_window_bits (png_structp \fP\fIpng_ptr\fP\fB, int \fIwindow_bits\fP\fB);\fP |
| 455 | |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 456 | \fBvoid png_set_text_compression_method (png_structp \fP\fIpng_ptr\fP\fB, int \fImethod\fP\fB);\fP |
Glenn Randers-Pehrson | 8eb8833 | 2011-04-01 00:16:50 -0500 | [diff] [blame] | 457 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 458 | \fBvoid png_set_tIME (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fImod_time\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 459 | |
Glenn Randers-Pehrson | f3c51e4 | 2011-01-15 10:25:25 -0600 | [diff] [blame] | 460 | \fBvoid png_set_tRNS (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fItrans_alpha\fP\fB, int \fP\fInum_trans\fP\fB, png_color_16p \fItrans_color\fP\fB);\fP |
Glenn Randers-Pehrson | f7d1a17 | 1998-06-06 15:31:35 -0500 | [diff] [blame] | 461 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 462 | \fBvoid png_set_tRNS_to_alpha (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 463 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 464 | \fBpng_uint_32 png_set_unknown_chunks (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_unknown_chunkp \fP\fIunknowns\fP\fB, int \fP\fInum\fP\fB, int \fIlocation\fP\fB);\fP |
| 465 | |
Glenn Randers-Pehrson | bb98bcb | 2011-01-22 16:27:39 -0600 | [diff] [blame] | 466 | \fBvoid png_set_unknown_chunk_location (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIchunk\fP\fB, int \fIlocation\fP\fB);\fP |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 467 | |
Glenn Randers-Pehrson | 272489d | 2004-08-04 06:34:52 -0500 | [diff] [blame] | 468 | \fBvoid png_set_user_limits (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIuser_width_max\fP\fB, png_uint_32 \fIuser_height_max\fP\fB);\fP |
| 469 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 470 | \fBvoid png_set_user_transform_info (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIuser_transform_ptr\fP\fB, int \fP\fIuser_transform_depth\fP\fB, int \fIuser_transform_channels\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 471 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 472 | \fBvoid png_set_write_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIio_ptr\fP\fB, png_rw_ptr \fP\fIwrite_data_fn\fP\fB, png_flush_ptr \fIoutput_flush_fn\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 473 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 474 | \fBvoid png_set_write_status_fn (png_structp \fP\fIpng_ptr\fP\fB, png_write_status_ptr \fIwrite_row_fn\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 475 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 476 | \fBvoid png_set_write_user_transform_fn (png_structp \fP\fIpng_ptr\fP\fB, png_user_transform_ptr \fIwrite_user_transform_fn\fP\fB);\fP |
Glenn Randers-Pehrson | 08a3343 | 1998-03-07 06:06:55 -0600 | [diff] [blame] | 477 | |
Cosmin Truta | a74aa9a | 2018-06-17 22:37:44 -0400 | [diff] [blame] | 478 | \fBint png_sig_cmp (png_bytep \fP\fIsig\fP\fB, size_t \fP\fIstart\fP\fB, size_t \fInum_to_check\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 479 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 480 | \fBvoid png_start_read_image (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 481 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 482 | \fBvoid png_warning (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fImessage\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 483 | |
Cosmin Truta | a74aa9a | 2018-06-17 22:37:44 -0400 | [diff] [blame] | 484 | \fBvoid png_write_chunk (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIchunk_name\fP\fB, png_bytep \fP\fIdata\fP\fB, size_t \fIlength\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 485 | |
Cosmin Truta | a74aa9a | 2018-06-17 22:37:44 -0400 | [diff] [blame] | 486 | \fBvoid png_write_chunk_data (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIdata\fP\fB, size_t \fIlength\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 487 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 488 | \fBvoid png_write_chunk_end (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 489 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 490 | \fBvoid png_write_chunk_start (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIchunk_name\fP\fB, png_uint_32 \fIlength\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 491 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 492 | \fBvoid png_write_end (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 493 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 494 | \fBvoid png_write_flush (png_structp \fIpng_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 495 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 496 | \fBvoid png_write_image (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fIimage\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 497 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 498 | \fBvoid png_write_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 499 | |
Glenn Randers-Pehrson | 5379b24 | 1999-11-27 10:22:33 -0600 | [diff] [blame] | 500 | \fBvoid png_write_info_before_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP |
| 501 | |
Glenn Randers-Pehrson | 5e5c1e1 | 2000-11-10 12:26:19 -0600 | [diff] [blame] | 502 | \fBvoid png_write_png (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fItransforms\fP\fB, png_voidp \fIparams\fP\fB);\fP |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 503 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 504 | \fBvoid png_write_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIrow\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 505 | |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 506 | \fBvoid png_write_rows (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fP\fIrow\fP\fB, png_uint_32 \fInum_rows\fP\fB);\fP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 507 | |
Glenn Randers-Pehrson | 6bc53be | 2006-06-16 07:52:03 -0500 | [diff] [blame] | 508 | \fBvoid png_write_sig (png_structp \fIpng_ptr\fP\fB);\fP |
| 509 | |
Glenn Randers-Pehrson | 0f881d6 | 1998-02-07 10:20:57 -0600 | [diff] [blame] | 510 | .SH DESCRIPTION |
| 511 | The |
| 512 | .I libpng |
| 513 | library supports encoding, decoding, and various manipulations of |
| 514 | the Portable Network Graphics (PNG) format image files. It uses the |
| 515 | .IR zlib(3) |
| 516 | compression library. |
Glenn Randers-Pehrson | 557b256 | 2010-10-17 12:55:04 -0500 | [diff] [blame] | 517 | Following is a copy of the libpng-manual.txt file that accompanies libpng. |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 518 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 519 | .SH LIBPNG.TXT |
Glenn Randers-Pehrson | 557b256 | 2010-10-17 12:55:04 -0500 | [diff] [blame] | 520 | libpng-manual.txt - A description on how to use and modify libpng |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 521 | |
Cosmin Truta | a40189c | 2019-04-14 14:10:32 -0400 | [diff] [blame] | 522 | Copyright (c) 2018-2019 Cosmin Truta |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 523 | Copyright (c) 1998-2018 Glenn Randers-Pehrson |
Glenn Randers-Pehrson | 037023b | 2009-06-24 10:27:36 -0500 | [diff] [blame] | 524 | |
Glenn Randers-Pehrson | bfbf865 | 2009-06-26 21:46:52 -0500 | [diff] [blame] | 525 | This document is released under the libpng license. |
Glenn Randers-Pehrson | c332bbc | 2009-06-25 13:43:50 -0500 | [diff] [blame] | 526 | For conditions of distribution and use, see the disclaimer |
Glenn Randers-Pehrson | 037023b | 2009-06-24 10:27:36 -0500 | [diff] [blame] | 527 | and license in png.h |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 528 | |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 529 | Based on: |
| 530 | |
Cosmin Truta | a40189c | 2019-04-14 14:10:32 -0400 | [diff] [blame] | 531 | libpng version 1.6.36, December 2018, through 1.6.37 - April 2019 |
Cosmin Truta | eddf902 | 2018-12-01 09:36:00 -0500 | [diff] [blame] | 532 | Updated and distributed by Cosmin Truta |
Cosmin Truta | a40189c | 2019-04-14 14:10:32 -0400 | [diff] [blame] | 533 | Copyright (c) 2018-2019 Cosmin Truta |
Cosmin Truta | eddf902 | 2018-12-01 09:36:00 -0500 | [diff] [blame] | 534 | |
Cosmin Truta | a40189c | 2019-04-14 14:10:32 -0400 | [diff] [blame] | 535 | libpng versions 0.97, January 1998, through 1.6.35 - July 2018 |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 536 | Updated and distributed by Glenn Randers-Pehrson |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 537 | Copyright (c) 1998-2018 Glenn Randers-Pehrson |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 538 | |
Glenn Randers-Pehrson | 79b7e4e | 2014-06-07 14:45:01 -0500 | [diff] [blame] | 539 | libpng 1.0 beta 6 - version 0.96 - May 28, 1997 |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 540 | Updated and distributed by Andreas Dilger |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 541 | Copyright (c) 1996, 1997 Andreas Dilger |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 542 | |
Glenn Randers-Pehrson | 79b7e4e | 2014-06-07 14:45:01 -0500 | [diff] [blame] | 543 | libpng 1.0 beta 2 - version 0.88 - January 26, 1996 |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 544 | For conditions of distribution and use, see copyright |
| 545 | notice in png.h. Copyright (c) 1995, 1996 Guy Eric |
Glenn Randers-Pehrson | 08a3343 | 1998-03-07 06:06:55 -0600 | [diff] [blame] | 546 | Schalnat, Group 42, Inc. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 547 | |
| 548 | Updated/rewritten per request in the libpng FAQ |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 549 | Copyright (c) 1995, 1996 Frank J. T. Wojcik |
| 550 | December 18, 1995 & January 20, 1996 |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 551 | |
Glenn Randers-Pehrson | 6e41842 | 2011-12-29 20:57:39 -0600 | [diff] [blame] | 552 | TABLE OF CONTENTS |
| 553 | |
| 554 | I. Introduction |
| 555 | II. Structures |
| 556 | III. Reading |
| 557 | IV. Writing |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 558 | V. Simplified API |
| 559 | VI. Modifying/Customizing libpng |
| 560 | VII. MNG support |
| 561 | VIII. Changes to Libpng from version 0.88 |
| 562 | IX. Changes to Libpng from version 1.0.x to 1.2.x |
| 563 | X. Changes to Libpng from version 1.0.x/1.2.x to 1.4.x |
| 564 | XI. Changes to Libpng from version 1.4.x to 1.5.x |
| 565 | XII. Changes to Libpng from version 1.5.x to 1.6.x |
| 566 | XIII. Detecting libpng |
| 567 | XIV. Source code repository |
| 568 | XV. Coding style |
Glenn Randers-Pehrson | 6e41842 | 2011-12-29 20:57:39 -0600 | [diff] [blame] | 569 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 570 | .SH I. Introduction |
| 571 | |
| 572 | This file describes how to use and modify the PNG reference library |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 573 | (known as libpng) for your own use. In addition to this |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 574 | file, example.c is a good starting point for using the library, as |
| 575 | it is heavily commented and should include everything most people |
Glenn Randers-Pehrson | 08a3343 | 1998-03-07 06:06:55 -0600 | [diff] [blame] | 576 | will need. We assume that libpng is already installed; see the |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 577 | INSTALL file for instructions on how to configure and install libpng. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 578 | |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 579 | For examples of libpng usage, see the files "example.c", "pngtest.c", |
Glenn Randers-Pehrson | f210a05 | 2009-11-12 10:02:24 -0600 | [diff] [blame] | 580 | and the files in the "contrib" directory, all of which are included in |
| 581 | the libpng distribution. |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 582 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 583 | Libpng was written as a companion to the PNG specification, as a way |
| 584 | of reducing the amount of time and effort it takes to support the PNG |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 585 | file format in application programs. |
| 586 | |
Glenn Randers-Pehrson | a4981d4 | 2004-08-25 22:00:45 -0500 | [diff] [blame] | 587 | The PNG specification (second edition), November 2003, is available as |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 588 | a W3C Recommendation and as an ISO Standard (ISO/IEC 15948:2004 (E)) at |
Cosmin Truta | eddf902 | 2018-12-01 09:36:00 -0500 | [diff] [blame] | 589 | <https://www.w3.org/TR/2003/REC-PNG-20031110/>. |
Glenn Randers-Pehrson | a4981d4 | 2004-08-25 22:00:45 -0500 | [diff] [blame] | 590 | The W3C and ISO documents have identical technical content. |
| 591 | |
| 592 | The PNG-1.2 specification is available at |
Glenn Randers-Pehrson | 64f8110 | 2017-04-03 15:25:40 -0500 | [diff] [blame] | 593 | <https://png-mng.sourceforge.io/pub/png/spec/1.2/>. |
Glenn Randers-Pehrson | 682f4ba | 2015-08-11 13:04:01 -0500 | [diff] [blame] | 594 | It is technically equivalent |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 595 | to the PNG specification (second edition) but has some additional material. |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 596 | |
Cosmin Truta | eddf902 | 2018-12-01 09:36:00 -0500 | [diff] [blame] | 597 | The PNG-1.0 specification is available as RFC 2083 at |
Glenn Randers-Pehrson | 64f8110 | 2017-04-03 15:25:40 -0500 | [diff] [blame] | 598 | <https://png-mng.sourceforge.io/pub/png/spec/1.0/> and as a |
Cosmin Truta | eddf902 | 2018-12-01 09:36:00 -0500 | [diff] [blame] | 599 | W3C Recommendation at <https://www.w3.org/TR/REC-png-961001>. |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 600 | |
| 601 | Some additional chunks are described in the special-purpose public chunks |
Glenn Randers-Pehrson | a472858 | 2015-08-11 15:34:08 -0500 | [diff] [blame] | 602 | documents at <http://www.libpng.org/pub/png/spec/register/> |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 603 | |
| 604 | Other information |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 605 | about PNG, and the latest version of libpng, can be found at the PNG home |
Glenn Randers-Pehrson | a4981d4 | 2004-08-25 22:00:45 -0500 | [diff] [blame] | 606 | page, <http://www.libpng.org/pub/png/>. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 607 | |
| 608 | Most users will not have to modify the library significantly; advanced |
| 609 | users may want to modify it more. All attempts were made to make it as |
| 610 | complete as possible, while keeping the code easy to understand. |
| 611 | Currently, this library only supports C. Support for other languages |
| 612 | is being considered. |
| 613 | |
| 614 | Libpng has been designed to handle multiple sessions at one time, |
| 615 | to be easily modifiable, to be portable to the vast majority of |
| 616 | machines (ANSI, K&R, 16-, 32-, and 64-bit) available, and to be easy |
| 617 | to use. The ultimate goal of libpng is to promote the acceptance of |
| 618 | the PNG file format in whatever way possible. While there is still |
| 619 | work to be done (see the TODO file), libpng should cover the |
| 620 | majority of the needs of its users. |
| 621 | |
| 622 | Libpng uses zlib for its compression and decompression of PNG files. |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 623 | Further information about zlib, and the latest version of zlib, can |
Viktor Szakats | 95f3c07 | 2017-05-27 13:54:30 +0000 | [diff] [blame] | 624 | be found at the zlib home page, <https://zlib.net/>. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 625 | The zlib compression utility is a general purpose utility that is |
| 626 | useful for more than PNG files, and can be used without libpng. |
| 627 | See the documentation delivered with zlib for more details. |
| 628 | You can usually find the source files for the zlib utility wherever you |
| 629 | find the libpng source files. |
| 630 | |
| 631 | Libpng is thread safe, provided the threads are using different |
| 632 | instances of the structures. Each thread should have its own |
| 633 | png_struct and png_info instances, and thus its own image. |
| 634 | Libpng does not protect itself against two threads using the |
Glenn Randers-Pehrson | 56f6396 | 2008-10-06 10:16:17 -0500 | [diff] [blame] | 635 | same instance of a structure. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 636 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 637 | .SH II. Structures |
| 638 | |
| 639 | There are two main structures that are important to libpng, png_struct |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 640 | and png_info. Both are internal structures that are no longer exposed |
| 641 | in the libpng interface (as of libpng 1.5.0). |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 642 | |
| 643 | The png_info structure is designed to provide information about the |
| 644 | PNG file. At one time, the fields of png_info were intended to be |
| 645 | directly accessible to the user. However, this tended to cause problems |
| 646 | with applications using dynamically loaded libraries, and as a result |
Glenn Randers-Pehrson | 7529457 | 2000-05-06 14:09:57 -0500 | [diff] [blame] | 647 | a set of interface functions for png_info (the png_get_*() and png_set_*() |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 648 | functions) was developed, and direct access to the png_info fields was |
| 649 | deprecated.. |
Glenn Randers-Pehrson | 7529457 | 2000-05-06 14:09:57 -0500 | [diff] [blame] | 650 | |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 651 | The png_struct structure is the object used by the library to decode a |
| 652 | single image. As of 1.5.0 this structure is also not exposed. |
| 653 | |
| 654 | Almost all libpng APIs require a pointer to a png_struct as the first argument. |
| 655 | Many (in particular the png_set and png_get APIs) also require a pointer |
| 656 | to png_info as the second argument. Some application visible macros |
| 657 | defined in png.h designed for basic data access (reading and writing |
Glenn Randers-Pehrson | a5e5547 | 2011-07-12 10:13:32 -0500 | [diff] [blame] | 658 | integers in the PNG format) don't take a png_info pointer, but it's almost |
| 659 | always safe to assume that a (png_struct*) has to be passed to call an API |
| 660 | function. |
| 661 | |
| 662 | You can have more than one png_info structure associated with an image, |
| 663 | as illustrated in pngtest.c, one for information valid prior to the |
| 664 | IDAT chunks and another (called "end_info" below) for things after them. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 665 | |
| 666 | The png.h header file is an invaluable reference for programming with libpng. |
| 667 | And while I'm on the topic, make sure you include the libpng header file: |
| 668 | |
| 669 | #include <png.h> |
| 670 | |
Glenn Randers-Pehrson | a5e5547 | 2011-07-12 10:13:32 -0500 | [diff] [blame] | 671 | and also (as of libpng-1.5.0) the zlib header file, if you need it: |
| 672 | |
| 673 | #include <zlib.h> |
| 674 | |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 675 | .SS Types |
| 676 | |
| 677 | The png.h header file defines a number of integral types used by the |
| 678 | APIs. Most of these are fairly obvious; for example types corresponding |
| 679 | to integers of particular sizes and types for passing color values. |
| 680 | |
| 681 | One exception is how non-integral numbers are handled. For application |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 682 | convenience most APIs that take such numbers have C (double) arguments; |
| 683 | however, internally PNG, and libpng, use 32 bit signed integers and encode |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 684 | the value by multiplying by 100,000. As of libpng 1.5.0 a convenience |
| 685 | macro PNG_FP_1 is defined in png.h along with a type (png_fixed_point) |
| 686 | which is simply (png_int_32). |
| 687 | |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 688 | All APIs that take (double) arguments also have a matching API that |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 689 | takes the corresponding fixed point integer arguments. The fixed point |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 690 | API has the same name as the floating point one with "_fixed" appended. |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 691 | The actual range of values permitted in the APIs is frequently less than |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 692 | the full range of (png_fixed_point) (\-21474 to +21474). When APIs require |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 693 | a non-negative argument the type is recorded as png_uint_32 above. Consult |
| 694 | the header file and the text below for more information. |
| 695 | |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 696 | Special care must be take with sCAL chunk handling because the chunk itself |
| 697 | uses non-integral values encoded as strings containing decimal floating point |
| 698 | numbers. See the comments in the header file. |
| 699 | |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 700 | .SS Configuration |
| 701 | |
| 702 | The main header file function declarations are frequently protected by C |
| 703 | preprocessing directives of the form: |
| 704 | |
| 705 | #ifdef PNG_feature_SUPPORTED |
| 706 | declare-function |
| 707 | #endif |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 708 | ... |
| 709 | #ifdef PNG_feature_SUPPORTED |
| 710 | use-function |
| 711 | #endif |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 712 | |
| 713 | The library can be built without support for these APIs, although a |
| 714 | standard build will have all implemented APIs. Application programs |
| 715 | should check the feature macros before using an API for maximum |
| 716 | portability. From libpng 1.5.0 the feature macros set during the build |
| 717 | of libpng are recorded in the header file "pnglibconf.h" and this file |
| 718 | is always included by png.h. |
| 719 | |
Glenn Randers-Pehrson | a5e5547 | 2011-07-12 10:13:32 -0500 | [diff] [blame] | 720 | If you don't need to change the library configuration from the default, skip to |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 721 | the next section ("Reading"). |
| 722 | |
| 723 | Notice that some of the makefiles in the 'scripts' directory and (in 1.5.0) all |
| 724 | of the build project files in the 'projects' directory simply copy |
| 725 | scripts/pnglibconf.h.prebuilt to pnglibconf.h. This means that these build |
| 726 | systems do not permit easy auto-configuration of the library - they only |
| 727 | support the default configuration. |
| 728 | |
| 729 | The easiest way to make minor changes to the libpng configuration when |
| 730 | auto-configuration is supported is to add definitions to the command line |
| 731 | using (typically) CPPFLAGS. For example: |
| 732 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 733 | CPPFLAGS=\-DPNG_NO_FLOATING_ARITHMETIC |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 734 | |
| 735 | will change the internal libpng math implementation for gamma correction and |
| 736 | other arithmetic calculations to fixed point, avoiding the need for fast |
| 737 | floating point support. The result can be seen in the generated pnglibconf.h - |
| 738 | make sure it contains the changed feature macro setting. |
| 739 | |
| 740 | If you need to make more extensive configuration changes - more than one or two |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 741 | feature macro settings - you can either add \-DPNG_USER_CONFIG to the build |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 742 | command line and put a list of feature macro settings in pngusr.h or you can set |
| 743 | DFA_XTRA (a makefile variable) to a file containing the same information in the |
| 744 | form of 'option' settings. |
| 745 | |
| 746 | A. Changing pnglibconf.h |
| 747 | |
| 748 | A variety of methods exist to build libpng. Not all of these support |
| 749 | reconfiguration of pnglibconf.h. To reconfigure pnglibconf.h it must either be |
| 750 | rebuilt from scripts/pnglibconf.dfa using awk or it must be edited by hand. |
| 751 | |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 752 | Hand editing is achieved by copying scripts/pnglibconf.h.prebuilt to |
| 753 | pnglibconf.h and changing the lines defining the supported features, paying |
| 754 | very close attention to the 'option' information in scripts/pnglibconf.dfa |
| 755 | that describes those features and their requirements. This is easy to get |
| 756 | wrong. |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 757 | |
| 758 | B. Configuration using DFA_XTRA |
| 759 | |
| 760 | Rebuilding from pnglibconf.dfa is easy if a functioning 'awk', or a later |
| 761 | variant such as 'nawk' or 'gawk', is available. The configure build will |
| 762 | automatically find an appropriate awk and build pnglibconf.h. |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 763 | The scripts/pnglibconf.mak file contains a set of make rules for doing the |
| 764 | same thing if configure is not used, and many of the makefiles in the scripts |
| 765 | directory use this approach. |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 766 | |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 767 | When rebuilding simply write a new file containing changed options and set |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 768 | DFA_XTRA to the name of this file. This causes the build to append the new file |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 769 | to the end of scripts/pnglibconf.dfa. The pngusr.dfa file should contain lines |
| 770 | of the following forms: |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 771 | |
| 772 | everything = off |
| 773 | |
| 774 | This turns all optional features off. Include it at the start of pngusr.dfa to |
| 775 | make it easier to build a minimal configuration. You will need to turn at least |
| 776 | some features on afterward to enable either reading or writing code, or both. |
| 777 | |
| 778 | option feature on |
| 779 | option feature off |
| 780 | |
| 781 | Enable or disable a single feature. This will automatically enable other |
| 782 | features required by a feature that is turned on or disable other features that |
| 783 | require a feature which is turned off. Conflicting settings will cause an error |
| 784 | message to be emitted by awk. |
| 785 | |
| 786 | setting feature default value |
| 787 | |
| 788 | Changes the default value of setting 'feature' to 'value'. There are a small |
| 789 | number of settings listed at the top of pnglibconf.h, they are documented in the |
| 790 | source code. Most of these values have performance implications for the library |
| 791 | but most of them have no visible effect on the API. Some can also be overridden |
| 792 | from the API. |
| 793 | |
Glenn Randers-Pehrson | a5e5547 | 2011-07-12 10:13:32 -0500 | [diff] [blame] | 794 | This method of building a customized pnglibconf.h is illustrated in |
| 795 | contrib/pngminim/*. See the "$(PNGCONF):" target in the makefile and |
| 796 | pngusr.dfa in these directories. |
| 797 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 798 | C. Configuration using PNG_USER_CONFIG |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 799 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 800 | If \-DPNG_USER_CONFIG is added to the CPPFLAGS when pnglibconf.h is built, |
| 801 | the file pngusr.h will automatically be included before the options in |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 802 | scripts/pnglibconf.dfa are processed. Your pngusr.h file should contain only |
| 803 | macro definitions turning features on or off or setting settings. |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 804 | |
| 805 | Apart from the global setting "everything = off" all the options listed above |
| 806 | can be set using macros in pngusr.h: |
| 807 | |
| 808 | #define PNG_feature_SUPPORTED |
| 809 | |
| 810 | is equivalent to: |
| 811 | |
| 812 | option feature on |
| 813 | |
| 814 | #define PNG_NO_feature |
| 815 | |
| 816 | is equivalent to: |
| 817 | |
| 818 | option feature off |
| 819 | |
| 820 | #define PNG_feature value |
| 821 | |
| 822 | is equivalent to: |
| 823 | |
| 824 | setting feature default value |
| 825 | |
| 826 | Notice that in both cases, pngusr.dfa and pngusr.h, the contents of the |
| 827 | pngusr file you supply override the contents of scripts/pnglibconf.dfa |
| 828 | |
| 829 | If confusing or incomprehensible behavior results it is possible to |
| 830 | examine the intermediate file pnglibconf.dfn to find the full set of |
| 831 | dependency information for each setting and option. Simply locate the |
| 832 | feature in the file and read the C comments that precede it. |
| 833 | |
Glenn Randers-Pehrson | a5e5547 | 2011-07-12 10:13:32 -0500 | [diff] [blame] | 834 | This method is also illustrated in the contrib/pngminim/* makefiles and |
| 835 | pngusr.h. |
| 836 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 837 | .SH III. Reading |
| 838 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 839 | We'll now walk you through the possible functions to call when reading |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 840 | in a PNG file sequentially, briefly explaining the syntax and purpose |
| 841 | of each one. See example.c and png.h for more detail. While |
| 842 | progressive reading is covered in the next section, you will still |
| 843 | need some of the functions discussed in this section to read a PNG |
| 844 | file. |
| 845 | |
| 846 | .SS Setup |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 847 | |
| 848 | You will want to do the I/O initialization(*) before you get into libpng, |
| 849 | so if it doesn't work, you don't have much to undo. Of course, you |
| 850 | will also want to insure that you are, in fact, dealing with a PNG |
| 851 | file. Libpng provides a simple check to see if a file is a PNG file. |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 852 | To use it, pass in the first 1 to 8 bytes of the file to the function |
Glenn Randers-Pehrson | 6a9c2ce | 2009-03-27 19:30:10 -0500 | [diff] [blame] | 853 | png_sig_cmp(), and it will return 0 (false) if the bytes match the |
| 854 | corresponding bytes of the PNG signature, or nonzero (true) otherwise. |
| 855 | Of course, the more bytes you pass in, the greater the accuracy of the |
| 856 | prediction. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 857 | |
| 858 | If you are intending to keep the file pointer open for use in libpng, |
| 859 | you must ensure you don't read more than 8 bytes from the beginning |
Glenn Randers-Pehrson | 7f85da8 | 2015-03-05 20:50:56 -0600 | [diff] [blame] | 860 | of the file, and you also have to make a call to png_set_sig_bytes() |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 861 | with the number of bytes you read from the beginning. Libpng will |
| 862 | then only check the bytes (if any) that your program didn't read. |
| 863 | |
| 864 | (*): If you are not using the standard I/O functions, you will need |
| 865 | to replace them with custom functions. See the discussion under |
| 866 | Customizing libpng. |
| 867 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 868 | FILE *fp = fopen(file_name, "rb"); |
| 869 | if (!fp) |
| 870 | { |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 871 | return ERROR; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 872 | } |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 873 | |
Glenn Randers-Pehrson | b6c9ac6 | 2015-02-07 08:56:08 -0600 | [diff] [blame] | 874 | if (fread(header, 1, number, fp) != number) |
| 875 | { |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 876 | return ERROR; |
Glenn Randers-Pehrson | b6c9ac6 | 2015-02-07 08:56:08 -0600 | [diff] [blame] | 877 | } |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 878 | |
Glenn Randers-Pehrson | b6c9ac6 | 2015-02-07 08:56:08 -0600 | [diff] [blame] | 879 | is_png = !png_sig_cmp(header, 0, number); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 880 | if (!is_png) |
| 881 | { |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 882 | return NOT_PNG; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 883 | } |
| 884 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 885 | Next, png_struct and png_info need to be allocated and initialized. In |
| 886 | order to ensure that the size of these structures is correct even with a |
| 887 | dynamically linked libpng, there are functions to initialize and |
| 888 | allocate the structures. We also pass the library version, optional |
| 889 | pointers to error handling functions, and a pointer to a data struct for |
| 890 | use by the error functions, if necessary (the pointer and functions can |
| 891 | be NULL if the default error handlers are to be used). See the section |
| 892 | on Changes to Libpng below regarding the old initialization functions. |
Glenn Randers-Pehrson | 104622b | 2000-05-29 08:58:03 -0500 | [diff] [blame] | 893 | The structure allocation functions quietly return NULL if they fail to |
| 894 | create the structure, so your application should check for that. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 895 | |
| 896 | png_structp png_ptr = png_create_read_struct |
Glenn Randers-Pehrson | 61ea3ea | 2014-11-06 06:39:56 -0600 | [diff] [blame] | 897 | (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 898 | user_error_fn, user_warning_fn); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 899 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 900 | if (!png_ptr) |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 901 | return ERROR; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 902 | |
| 903 | png_infop info_ptr = png_create_info_struct(png_ptr); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 904 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 905 | if (!info_ptr) |
| 906 | { |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 907 | png_destroy_read_struct(&png_ptr, |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 908 | (png_infopp)NULL, (png_infopp)NULL); |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 909 | return ERROR; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 910 | } |
| 911 | |
Glenn Randers-Pehrson | f7d1a17 | 1998-06-06 15:31:35 -0500 | [diff] [blame] | 912 | If you want to use your own memory allocation routines, |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 913 | use a libpng that was built with PNG_USER_MEM_SUPPORTED defined, and use |
Glenn Randers-Pehrson | f7d1a17 | 1998-06-06 15:31:35 -0500 | [diff] [blame] | 914 | png_create_read_struct_2() instead of png_create_read_struct(): |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 915 | |
Glenn Randers-Pehrson | f7d1a17 | 1998-06-06 15:31:35 -0500 | [diff] [blame] | 916 | png_structp png_ptr = png_create_read_struct_2 |
Glenn Randers-Pehrson | 61ea3ea | 2014-11-06 06:39:56 -0600 | [diff] [blame] | 917 | (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, |
Glenn Randers-Pehrson | f7d1a17 | 1998-06-06 15:31:35 -0500 | [diff] [blame] | 918 | user_error_fn, user_warning_fn, (png_voidp) |
| 919 | user_mem_ptr, user_malloc_fn, user_free_fn); |
| 920 | |
| 921 | The error handling routines passed to png_create_read_struct() |
| 922 | and the memory alloc/free routines passed to png_create_struct_2() |
| 923 | are only necessary if you are not using the libpng supplied error |
| 924 | handling and memory alloc/free functions. |
| 925 | |
| 926 | When libpng encounters an error, it expects to longjmp back |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 927 | to your routine. Therefore, you will need to call setjmp and pass |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 928 | your png_jmpbuf(png_ptr). If you read the file from different |
John Bowler | e6dc85b | 2011-04-27 14:47:15 -0500 | [diff] [blame] | 929 | routines, you will need to update the longjmp buffer every time you enter |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 930 | a new routine that will call a png_*() function. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 931 | |
| 932 | See your documentation of setjmp/longjmp for your compiler for more |
Glenn Randers-Pehrson | a77ef62 | 2000-02-18 13:48:52 -0600 | [diff] [blame] | 933 | information on setjmp/longjmp. See the discussion on libpng error |
| 934 | handling in the Customizing Libpng section below for more information |
| 935 | on the libpng error handling. If an error occurs, and libpng longjmp's |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 936 | back to your setjmp, you will want to call png_destroy_read_struct() to |
| 937 | free any memory. |
| 938 | |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 939 | if (setjmp(png_jmpbuf(png_ptr))) |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 940 | { |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 941 | png_destroy_read_struct(&png_ptr, &info_ptr, |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 942 | &end_info); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 943 | fclose(fp); |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 944 | return ERROR; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 945 | } |
| 946 | |
Glenn Randers-Pehrson | 20786be | 2011-04-20 22:20:40 -0500 | [diff] [blame] | 947 | Pass (png_infopp)NULL instead of &end_info if you didn't create |
| 948 | an end_info structure. |
| 949 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 950 | If you would rather avoid the complexity of setjmp/longjmp issues, |
Glenn Randers-Pehrson | 54ac9a9 | 2010-04-02 17:06:22 -0500 | [diff] [blame] | 951 | you can compile libpng with PNG_NO_SETJMP, in which case |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 952 | errors will result in a call to PNG_ABORT() which defaults to abort(). |
| 953 | |
Glenn Randers-Pehrson | 54ac9a9 | 2010-04-02 17:06:22 -0500 | [diff] [blame] | 954 | You can #define PNG_ABORT() to a function that does something |
| 955 | more useful than abort(), as long as your function does not |
| 956 | return. |
| 957 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 958 | Now you need to set up the input code. The default for libpng is to |
| 959 | use the C function fread(). If you use this, you will need to pass a |
| 960 | valid FILE * in the function png_init_io(). Be sure that the file is |
| 961 | opened in binary mode. If you wish to handle reading data in another |
| 962 | way, you need not call the png_init_io() function, but you must then |
| 963 | implement the libpng I/O methods discussed in the Customizing Libpng |
| 964 | section below. |
| 965 | |
| 966 | png_init_io(png_ptr, fp); |
| 967 | |
| 968 | If you had previously opened the file and read any of the signature from |
| 969 | the beginning in order to see if this was a PNG file, you need to let |
| 970 | libpng know that there are some bytes missing from the start of the file. |
| 971 | |
| 972 | png_set_sig_bytes(png_ptr, number); |
| 973 | |
Glenn Randers-Pehrson | e3f3c4e | 2010-02-07 18:08:50 -0600 | [diff] [blame] | 974 | You can change the zlib compression buffer size to be used while |
| 975 | reading compressed data with |
| 976 | |
| 977 | png_set_compression_buffer_size(png_ptr, buffer_size); |
| 978 | |
| 979 | where the default size is 8192 bytes. Note that the buffer size |
| 980 | is changed immediately and the buffer is reallocated immediately, |
| 981 | instead of setting a flag to be acted upon later. |
| 982 | |
Glenn Randers-Pehrson | 9dd1cdf | 2011-01-06 21:42:36 -0600 | [diff] [blame] | 983 | If you want CRC errors to be handled in a different manner than |
| 984 | the default, use |
| 985 | |
| 986 | png_set_crc_action(png_ptr, crit_action, ancil_action); |
| 987 | |
| 988 | The values for png_set_crc_action() say how libpng is to handle CRC errors in |
| 989 | ancillary and critical chunks, and whether to use the data contained |
Glenn Randers-Pehrson | 04dab1e | 2016-09-26 10:32:24 -0500 | [diff] [blame] | 990 | therein. Starting with libpng-1.6.26, this also governs how an ADLER32 error |
| 991 | is handled while reading the IDAT chunk. Note that it is impossible to |
| 992 | "discard" data in a critical chunk. |
Glenn Randers-Pehrson | 9dd1cdf | 2011-01-06 21:42:36 -0600 | [diff] [blame] | 993 | |
| 994 | Choices for (int) crit_action are |
| 995 | PNG_CRC_DEFAULT 0 error/quit |
| 996 | PNG_CRC_ERROR_QUIT 1 error/quit |
| 997 | PNG_CRC_WARN_USE 3 warn/use data |
| 998 | PNG_CRC_QUIET_USE 4 quiet/use data |
| 999 | PNG_CRC_NO_CHANGE 5 use the current value |
| 1000 | |
| 1001 | Choices for (int) ancil_action are |
| 1002 | PNG_CRC_DEFAULT 0 error/quit |
| 1003 | PNG_CRC_ERROR_QUIT 1 error/quit |
| 1004 | PNG_CRC_WARN_DISCARD 2 warn/discard data |
| 1005 | PNG_CRC_WARN_USE 3 warn/use data |
| 1006 | PNG_CRC_QUIET_USE 4 quiet/use data |
| 1007 | PNG_CRC_NO_CHANGE 5 use the current value |
| 1008 | |
Glenn Randers-Pehrson | 04dab1e | 2016-09-26 10:32:24 -0500 | [diff] [blame] | 1009 | When the setting for crit_action is PNG_CRC_QUIET_USE, the CRC and ADLER32 |
| 1010 | checksums are not only ignored, but they are not evaluated. |
| 1011 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1012 | .SS Setting up callback code |
| 1013 | |
| 1014 | You can set up a callback function to handle any unknown chunks in the |
| 1015 | input stream. You must supply the function |
| 1016 | |
Glenn Randers-Pehrson | 81ce889 | 2011-01-24 08:04:37 -0600 | [diff] [blame] | 1017 | read_chunk_callback(png_structp png_ptr, |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1018 | png_unknown_chunkp chunk); |
| 1019 | { |
| 1020 | /* The unknown chunk structure contains your |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 1021 | chunk data, along with similar data for any other |
| 1022 | unknown chunks: */ |
| 1023 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1024 | png_byte name[5]; |
| 1025 | png_byte *data; |
Cosmin Truta | a74aa9a | 2018-06-17 22:37:44 -0400 | [diff] [blame] | 1026 | size_t size; |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 1027 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 1028 | /* Note that libpng has already taken care of |
| 1029 | the CRC handling */ |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1030 | |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 1031 | /* put your code here. Search for your chunk in the |
| 1032 | unknown chunk structure, process it, and return one |
| 1033 | of the following: */ |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1034 | |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 1035 | return \-n; /* chunk had an error */ |
| 1036 | return 0; /* did not recognize */ |
| 1037 | return n; /* success */ |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1038 | } |
| 1039 | |
| 1040 | (You can give your function another name that you like instead of |
| 1041 | "read_chunk_callback") |
| 1042 | |
| 1043 | To inform libpng about your function, use |
| 1044 | |
| 1045 | png_set_read_user_chunk_fn(png_ptr, user_chunk_ptr, |
| 1046 | read_chunk_callback); |
| 1047 | |
| 1048 | This names not only the callback function, but also a user pointer that |
| 1049 | you can retrieve with |
| 1050 | |
| 1051 | png_get_user_chunk_ptr(png_ptr); |
| 1052 | |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 1053 | If you call the png_set_read_user_chunk_fn() function, then all unknown |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1054 | chunks which the callback does not handle will be saved when read. You can |
| 1055 | cause them to be discarded by returning '1' ("handled") instead of '0'. This |
| 1056 | behavior will change in libpng 1.7 and the default handling set by the |
| 1057 | png_set_keep_unknown_chunks() function, described below, will be used when the |
| 1058 | callback returns 0. If you want the existing behavior you should set the global |
| 1059 | default to PNG_HANDLE_CHUNK_IF_SAFE now; this is compatible with all current |
| 1060 | versions of libpng and with 1.7. Libpng 1.6 issues a warning if you keep the |
| 1061 | default, or PNG_HANDLE_CHUNK_NEVER, and the callback returns 0. |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 1062 | |
Glenn Randers-Pehrson | 08a3343 | 1998-03-07 06:06:55 -0600 | [diff] [blame] | 1063 | At this point, you can set up a callback function that will be |
| 1064 | called after each row has been read, which you can use to control |
| 1065 | a progress meter or the like. It's demonstrated in pngtest.c. |
| 1066 | You must supply a function |
| 1067 | |
Glenn Randers-Pehrson | 81ce889 | 2011-01-24 08:04:37 -0600 | [diff] [blame] | 1068 | void read_row_callback(png_structp png_ptr, |
| 1069 | png_uint_32 row, int pass); |
Glenn Randers-Pehrson | 08a3343 | 1998-03-07 06:06:55 -0600 | [diff] [blame] | 1070 | { |
| 1071 | /* put your code here */ |
| 1072 | } |
| 1073 | |
| 1074 | (You can give it another name that you like instead of "read_row_callback") |
| 1075 | |
| 1076 | To inform libpng about your function, use |
| 1077 | |
| 1078 | png_set_read_status_fn(png_ptr, read_row_callback); |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 1079 | |
John Bowler | 59010e5 | 2011-02-16 06:16:31 -0600 | [diff] [blame] | 1080 | When this function is called the row has already been completely processed and |
| 1081 | the 'row' and 'pass' refer to the next row to be handled. For the |
| 1082 | non-interlaced case the row that was just handled is simply one less than the |
| 1083 | passed in row number, and pass will always be 0. For the interlaced case the |
| 1084 | same applies unless the row value is 0, in which case the row just handled was |
| 1085 | the last one from one of the preceding passes. Because interlacing may skip a |
Glenn Randers-Pehrson | 4b4a958 | 2016-06-23 10:58:24 -0500 | [diff] [blame] | 1086 | pass you cannot be sure that the preceding pass is just 'pass\-1'; if you really |
John Bowler | 59010e5 | 2011-02-16 06:16:31 -0600 | [diff] [blame] | 1087 | need to know what the last pass is record (row,pass) from the callback and use |
| 1088 | the last recorded value each time. |
| 1089 | |
| 1090 | As with the user transform you can find the output row using the |
| 1091 | PNG_ROW_FROM_PASS_ROW macro. |
| 1092 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1093 | .SS Unknown-chunk handling |
| 1094 | |
| 1095 | Now you get to set the way the library processes unknown chunks in the |
| 1096 | input PNG stream. Both known and unknown chunks will be read. Normal |
| 1097 | behavior is that known chunks will be parsed into information in |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 1098 | various info_ptr members while unknown chunks will be discarded. This |
| 1099 | behavior can be wasteful if your application will never use some known |
| 1100 | chunk types. To change this, you can call: |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1101 | |
Glenn Randers-Pehrson | 272489d | 2004-08-04 06:34:52 -0500 | [diff] [blame] | 1102 | png_set_keep_unknown_chunks(png_ptr, keep, |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1103 | chunk_list, num_chunks); |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 1104 | |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 1105 | keep - 0: default unknown chunk handling |
| 1106 | 1: ignore; do not keep |
Glenn Randers-Pehrson | d029a75 | 2004-08-09 21:50:32 -0500 | [diff] [blame] | 1107 | 2: keep only if safe-to-copy |
| 1108 | 3: keep even if unsafe-to-copy |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1109 | |
Glenn Randers-Pehrson | d029a75 | 2004-08-09 21:50:32 -0500 | [diff] [blame] | 1110 | You can use these definitions: |
| 1111 | PNG_HANDLE_CHUNK_AS_DEFAULT 0 |
| 1112 | PNG_HANDLE_CHUNK_NEVER 1 |
| 1113 | PNG_HANDLE_CHUNK_IF_SAFE 2 |
| 1114 | PNG_HANDLE_CHUNK_ALWAYS 3 |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1115 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1116 | chunk_list - list of chunks affected (a byte string, |
| 1117 | five bytes per chunk, NULL or '\0' if |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 1118 | num_chunks is positive; ignored if |
| 1119 | numchunks <= 0). |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1120 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1121 | num_chunks - number of chunks affected; if 0, all |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 1122 | unknown chunks are affected. If positive, |
| 1123 | only the chunks in the list are affected, |
| 1124 | and if negative all unknown chunks and |
| 1125 | all known chunks except for the IHDR, |
| 1126 | PLTE, tRNS, IDAT, and IEND chunks are |
| 1127 | affected. |
Glenn Randers-Pehrson | dff799e | 2004-08-07 21:42:49 -0500 | [diff] [blame] | 1128 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1129 | Unknown chunks declared in this way will be saved as raw data onto a |
| 1130 | list of png_unknown_chunk structures. If a chunk that is normally |
| 1131 | known to libpng is named in the list, it will be handled as unknown, |
| 1132 | according to the "keep" directive. If a chunk is named in successive |
| 1133 | instances of png_set_keep_unknown_chunks(), the final instance will |
Glenn Randers-Pehrson | d029a75 | 2004-08-09 21:50:32 -0500 | [diff] [blame] | 1134 | take precedence. The IHDR and IEND chunks should not be named in |
| 1135 | chunk_list; if they are, libpng will process them normally anyway. |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 1136 | If you know that your application will never make use of some particular |
| 1137 | chunks, use PNG_HANDLE_CHUNK_NEVER (or 1) as demonstrated below. |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1138 | |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 1139 | Here is an example of the usage of png_set_keep_unknown_chunks(), |
| 1140 | where the private "vpAg" chunk will later be processed by a user chunk |
| 1141 | callback function: |
| 1142 | |
| 1143 | png_byte vpAg[5]={118, 112, 65, 103, (png_byte) '\0'}; |
| 1144 | |
| 1145 | #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED) |
| 1146 | png_byte unused_chunks[]= |
| 1147 | { |
| 1148 | 104, 73, 83, 84, (png_byte) '\0', /* hIST */ |
| 1149 | 105, 84, 88, 116, (png_byte) '\0', /* iTXt */ |
| 1150 | 112, 67, 65, 76, (png_byte) '\0', /* pCAL */ |
| 1151 | 115, 67, 65, 76, (png_byte) '\0', /* sCAL */ |
| 1152 | 115, 80, 76, 84, (png_byte) '\0', /* sPLT */ |
| 1153 | 116, 73, 77, 69, (png_byte) '\0', /* tIME */ |
| 1154 | }; |
| 1155 | #endif |
| 1156 | |
| 1157 | ... |
| 1158 | |
| 1159 | #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED) |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1160 | /* ignore all unknown chunks |
| 1161 | * (use global setting "2" for libpng16 and earlier): |
| 1162 | */ |
| 1163 | png_set_keep_unknown_chunks(read_ptr, 2, NULL, 0); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1164 | |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 1165 | /* except for vpAg: */ |
| 1166 | png_set_keep_unknown_chunks(read_ptr, 2, vpAg, 1); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1167 | |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 1168 | /* also ignore unused known chunks: */ |
| 1169 | png_set_keep_unknown_chunks(read_ptr, 1, unused_chunks, |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1170 | (int)(sizeof unused_chunks)/5); |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 1171 | #endif |
| 1172 | |
Glenn Randers-Pehrson | 800d1e9 | 2008-08-20 17:25:21 -0500 | [diff] [blame] | 1173 | .SS User limits |
| 1174 | |
| 1175 | The PNG specification allows the width and height of an image to be as |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1176 | large as 2^(31\-1 (0x7fffffff), or about 2.147 billion rows and columns. |
Glenn Randers-Pehrson | 8ba4b13 | 2015-08-16 22:49:58 -0500 | [diff] [blame] | 1177 | For safety, libpng imposes a default limit of 1 million rows and columns. |
Glenn Randers-Pehrson | 800d1e9 | 2008-08-20 17:25:21 -0500 | [diff] [blame] | 1178 | Larger images will be rejected immediately with a png_error() call. If |
Glenn Randers-Pehrson | d375ca5 | 2015-02-21 12:29:36 -0600 | [diff] [blame] | 1179 | you wish to change these limits, you can use |
Glenn Randers-Pehrson | 800d1e9 | 2008-08-20 17:25:21 -0500 | [diff] [blame] | 1180 | |
| 1181 | png_set_user_limits(png_ptr, width_max, height_max); |
| 1182 | |
Glenn Randers-Pehrson | f43b5e3 | 2014-12-20 19:10:52 -0600 | [diff] [blame] | 1183 | to set your own limits (libpng may reject some very wide images |
Glenn Randers-Pehrson | 800d1e9 | 2008-08-20 17:25:21 -0500 | [diff] [blame] | 1184 | anyway because of potential buffer overflow conditions). |
| 1185 | |
| 1186 | You should put this statement after you create the PNG structure and |
| 1187 | before calling png_read_info(), png_read_png(), or png_process_data(). |
Glenn Randers-Pehrson | cc27708 | 2011-06-10 21:17:34 -0500 | [diff] [blame] | 1188 | |
| 1189 | When writing a PNG datastream, put this statement before calling |
| 1190 | png_write_info() or png_write_png(). |
| 1191 | |
Glenn Randers-Pehrson | 800d1e9 | 2008-08-20 17:25:21 -0500 | [diff] [blame] | 1192 | If you need to retrieve the limits that are being applied, use |
| 1193 | |
| 1194 | width_max = png_get_user_width_max(png_ptr); |
| 1195 | height_max = png_get_user_height_max(png_ptr); |
| 1196 | |
| 1197 | The PNG specification sets no limit on the number of ancillary chunks |
Glenn Randers-Pehrson | 8ba4b13 | 2015-08-16 22:49:58 -0500 | [diff] [blame] | 1198 | allowed in a PNG datastream. By default, libpng imposes a limit of |
| 1199 | a total of 1000 sPLT, tEXt, iTXt, zTXt, and unknown chunks to be stored. |
| 1200 | If you have set up both info_ptr and end_info_ptr, the limit applies |
| 1201 | separately to each. You can change the limit on the total number of such |
| 1202 | chunks that will be stored, with |
Glenn Randers-Pehrson | 800d1e9 | 2008-08-20 17:25:21 -0500 | [diff] [blame] | 1203 | |
| 1204 | png_set_chunk_cache_max(png_ptr, user_chunk_cache_max); |
| 1205 | |
| 1206 | where 0x7fffffffL means unlimited. You can retrieve this limit with |
| 1207 | |
| 1208 | chunk_cache_max = png_get_chunk_cache_max(png_ptr); |
| 1209 | |
Glenn Randers-Pehrson | 8ba4b13 | 2015-08-16 22:49:58 -0500 | [diff] [blame] | 1210 | Libpng imposes a limit of 8 Megabytes (8,000,000 bytes) on the amount of |
Glenn Randers-Pehrson | 6b53a5e | 2017-08-02 19:58:31 -0500 | [diff] [blame] | 1211 | memory that any chunk other than IDAT can occupy, originally or when |
| 1212 | decompressed (prior to libpng-1.6.32 the limit was only applied to compressed |
| 1213 | chunks after decompression). You can change this limit with |
Glenn Randers-Pehrson | e3f3c4e | 2010-02-07 18:08:50 -0600 | [diff] [blame] | 1214 | |
| 1215 | png_set_chunk_malloc_max(png_ptr, user_chunk_malloc_max); |
| 1216 | |
| 1217 | and you can retrieve the limit with |
| 1218 | |
| 1219 | chunk_malloc_max = png_get_chunk_malloc_max(png_ptr); |
| 1220 | |
| 1221 | Any chunks that would cause either of these limits to be exceeded will |
| 1222 | be ignored. |
| 1223 | |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1224 | .SS Information about your system |
| 1225 | |
| 1226 | If you intend to display the PNG or to incorporate it in other image data you |
| 1227 | need to tell libpng information about your display or drawing surface so that |
| 1228 | libpng can convert the values in the image to match the display. |
| 1229 | |
Glenn Randers-Pehrson | 733b131 | 2011-06-15 13:21:01 -0500 | [diff] [blame] | 1230 | From libpng-1.5.4 this information can be set before reading the PNG file |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1231 | header. In earlier versions png_set_gamma() existed but behaved incorrectly if |
| 1232 | called before the PNG file header had been read and png_set_alpha_mode() did not |
| 1233 | exist. |
| 1234 | |
Glenn Randers-Pehrson | 733b131 | 2011-06-15 13:21:01 -0500 | [diff] [blame] | 1235 | If you need to support versions prior to libpng-1.5.4 test the version number |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 1236 | as illustrated below using "PNG_LIBPNG_VER >= 10504" and follow the procedures |
| 1237 | described in the appropriate manual page. |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1238 | |
| 1239 | You give libpng the encoding expected by your system expressed as a 'gamma' |
| 1240 | value. You can also specify a default encoding for the PNG file in |
| 1241 | case the required information is missing from the file. By default libpng |
| 1242 | assumes that the PNG data matches your system, to keep this default call: |
| 1243 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1244 | png_set_gamma(png_ptr, screen_gamma, output_gamma); |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1245 | |
| 1246 | or you can use the fixed point equivalent: |
| 1247 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 1248 | png_set_gamma_fixed(png_ptr, PNG_FP_1*screen_gamma, |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1249 | PNG_FP_1*output_gamma); |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1250 | |
Glenn Randers-Pehrson | 95ba417 | 2011-09-08 12:21:42 -0500 | [diff] [blame] | 1251 | If you don't know the gamma for your system it is probably 2.2 - a good |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1252 | approximation to the IEC standard for display systems (sRGB). If images are |
| 1253 | too contrasty or washed out you got the value wrong - check your system |
| 1254 | documentation! |
| 1255 | |
| 1256 | Many systems permit the system gamma to be changed via a lookup table in the |
| 1257 | display driver, a few systems, including older Macs, change the response by |
Glenn Randers-Pehrson | 733b131 | 2011-06-15 13:21:01 -0500 | [diff] [blame] | 1258 | default. As of 1.5.4 three special values are available to handle common |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1259 | situations: |
| 1260 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 1261 | PNG_DEFAULT_sRGB: Indicates that the system conforms to the |
| 1262 | IEC 61966-2-1 standard. This matches almost |
| 1263 | all systems. |
| 1264 | PNG_GAMMA_MAC_18: Indicates that the system is an older |
| 1265 | (pre Mac OS 10.6) Apple Macintosh system with |
| 1266 | the default settings. |
| 1267 | PNG_GAMMA_LINEAR: Just the fixed point value for 1.0 - indicates |
| 1268 | that the system expects data with no gamma |
| 1269 | encoding. |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1270 | |
| 1271 | You would use the linear (unencoded) value if you need to process the pixel |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1272 | values further because this avoids the need to decode and re-encode each |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1273 | component value whenever arithmetic is performed. A lot of graphics software |
| 1274 | uses linear values for this reason, often with higher precision component values |
| 1275 | to preserve overall accuracy. |
| 1276 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1277 | |
| 1278 | The output_gamma value expresses how to decode the output values, not how |
| 1279 | they are encoded. The values used correspond to the normal numbers used to |
| 1280 | describe the overall gamma of a computer display system; for example 2.2 for |
| 1281 | an sRGB conformant system. The values are scaled by 100000 in the _fixed |
| 1282 | version of the API (so 220000 for sRGB.) |
| 1283 | |
| 1284 | The inverse of the value is always used to provide a default for the PNG file |
| 1285 | encoding if it has no gAMA chunk and if png_set_gamma() has not been called |
| 1286 | to override the PNG gamma information. |
| 1287 | |
| 1288 | When the ALPHA_OPTIMIZED mode is selected the output gamma is used to encode |
| 1289 | opaque pixels however pixels with lower alpha values are not encoded, |
| 1290 | regardless of the output gamma setting. |
| 1291 | |
| 1292 | When the standard Porter Duff handling is requested with mode 1 the output |
| 1293 | encoding is set to be linear and the output_gamma value is only relevant |
| 1294 | as a default for input data that has no gamma information. The linear output |
| 1295 | encoding will be overridden if png_set_gamma() is called - the results may be |
| 1296 | highly unexpected! |
| 1297 | |
| 1298 | The following numbers are derived from the sRGB standard and the research |
| 1299 | behind it. sRGB is defined to be approximated by a PNG gAMA chunk value of |
| 1300 | 0.45455 (1/2.2) for PNG. The value implicitly includes any viewing |
| 1301 | correction required to take account of any differences in the color |
| 1302 | environment of the original scene and the intended display environment; the |
| 1303 | value expresses how to *decode* the image for display, not how the original |
| 1304 | data was *encoded*. |
| 1305 | |
| 1306 | sRGB provides a peg for the PNG standard by defining a viewing environment. |
| 1307 | sRGB itself, and earlier TV standards, actually use a more complex transform |
| 1308 | (a linear portion then a gamma 2.4 power law) than PNG can express. (PNG is |
| 1309 | limited to simple power laws.) By saying that an image for direct display on |
| 1310 | an sRGB conformant system should be stored with a gAMA chunk value of 45455 |
| 1311 | (11.3.3.2 and 11.3.3.5 of the ISO PNG specification) the PNG specification |
| 1312 | makes it possible to derive values for other display systems and |
| 1313 | environments. |
| 1314 | |
| 1315 | The Mac value is deduced from the sRGB based on an assumption that the actual |
| 1316 | extra viewing correction used in early Mac display systems was implemented as |
| 1317 | a power 1.45 lookup table. |
| 1318 | |
| 1319 | Any system where a programmable lookup table is used or where the behavior of |
| 1320 | the final display device characteristics can be changed requires system |
| 1321 | specific code to obtain the current characteristic. However this can be |
| 1322 | difficult and most PNG gamma correction only requires an approximate value. |
| 1323 | |
| 1324 | By default, if png_set_alpha_mode() is not called, libpng assumes that all |
| 1325 | values are unencoded, linear, values and that the output device also has a |
| 1326 | linear characteristic. This is only very rarely correct - it is invariably |
| 1327 | better to call png_set_alpha_mode() with PNG_DEFAULT_sRGB than rely on the |
| 1328 | default if you don't know what the right answer is! |
| 1329 | |
| 1330 | The special value PNG_GAMMA_MAC_18 indicates an older Mac system (pre Mac OS |
| 1331 | 10.6) which used a correction table to implement a somewhat lower gamma on an |
| 1332 | otherwise sRGB system. |
| 1333 | |
| 1334 | Both these values are reserved (not simple gamma values) in order to allow |
| 1335 | more precise correction internally in the future. |
| 1336 | |
| 1337 | NOTE: the values can be passed to either the fixed or floating |
| 1338 | point APIs, but the floating point API will also accept floating point |
| 1339 | values. |
| 1340 | |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1341 | The second thing you may need to tell libpng about is how your system handles |
| 1342 | alpha channel information. Some, but not all, PNG files contain an alpha |
| 1343 | channel. To display these files correctly you need to compose the data onto a |
| 1344 | suitable background, as described in the PNG specification. |
| 1345 | |
| 1346 | Libpng only supports composing onto a single color (using png_set_background; |
Glenn Randers-Pehrson | 95ba417 | 2011-09-08 12:21:42 -0500 | [diff] [blame] | 1347 | see below). Otherwise you must do the composition yourself and, in this case, |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1348 | you may need to call png_set_alpha_mode: |
| 1349 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 1350 | #if PNG_LIBPNG_VER >= 10504 |
| 1351 | png_set_alpha_mode(png_ptr, mode, screen_gamma); |
| 1352 | #else |
| 1353 | png_set_gamma(png_ptr, screen_gamma, 1.0/screen_gamma); |
| 1354 | #endif |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1355 | |
Glenn Randers-Pehrson | 95ba417 | 2011-09-08 12:21:42 -0500 | [diff] [blame] | 1356 | The screen_gamma value is the same as the argument to png_set_gamma; however, |
| 1357 | how it affects the output depends on the mode. png_set_alpha_mode() sets the |
| 1358 | file gamma default to 1/screen_gamma, so normally you don't need to call |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1359 | png_set_gamma. If you need different defaults call png_set_gamma() before |
| 1360 | png_set_alpha_mode() - if you call it after it will override the settings made |
| 1361 | by png_set_alpha_mode(). |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1362 | |
| 1363 | The mode is as follows: |
| 1364 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1365 | PNG_ALPHA_PNG: The data is encoded according to the PNG |
| 1366 | specification. Red, green and blue, or gray, components are |
| 1367 | gamma encoded color values and are not premultiplied by the |
| 1368 | alpha value. The alpha value is a linear measure of the |
| 1369 | contribution of the pixel to the corresponding final output pixel. |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1370 | |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1371 | You should normally use this format if you intend to perform |
| 1372 | color correction on the color values; most, maybe all, color |
| 1373 | correction software has no handling for the alpha channel and, |
| 1374 | anyway, the math to handle pre-multiplied component values is |
| 1375 | unnecessarily complex. |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1376 | |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1377 | Before you do any arithmetic on the component values you need |
| 1378 | to remove the gamma encoding and multiply out the alpha |
| 1379 | channel. See the PNG specification for more detail. It is |
| 1380 | important to note that when an image with an alpha channel is |
| 1381 | scaled, linear encoded, pre-multiplied component values must |
| 1382 | be used! |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1383 | |
| 1384 | The remaining modes assume you don't need to do any further color correction or |
Glenn Randers-Pehrson | 95ba417 | 2011-09-08 12:21:42 -0500 | [diff] [blame] | 1385 | that if you do, your color correction software knows all about alpha (it |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1386 | probably doesn't!). They 'associate' the alpha with the color information by |
| 1387 | storing color channel values that have been scaled by the alpha. The |
| 1388 | advantage is that the color channels can be resampled (the image can be |
| 1389 | scaled) in this form. The disadvantage is that normal practice is to store |
| 1390 | linear, not (gamma) encoded, values and this requires 16-bit channels for |
| 1391 | still images rather than the 8-bit channels that are just about sufficient if |
| 1392 | gamma encoding is used. In addition all non-transparent pixel values, |
| 1393 | including completely opaque ones, must be gamma encoded to produce the final |
| 1394 | image. These are the 'STANDARD', 'ASSOCIATED' or 'PREMULTIPLIED' modes |
| 1395 | described below (the latter being the two common names for associated alpha |
| 1396 | color channels). Note that PNG files always contain non-associated color |
| 1397 | channels; png_set_alpha_mode() with one of the modes causes the decoder to |
| 1398 | convert the pixels to an associated form before returning them to your |
| 1399 | application. |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1400 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1401 | Since it is not necessary to perform arithmetic on opaque color values so |
| 1402 | long as they are not to be resampled and are in the final color space it is |
| 1403 | possible to optimize the handling of alpha by storing the opaque pixels in |
| 1404 | the PNG format (adjusted for the output color space) while storing partially |
| 1405 | opaque pixels in the standard, linear, format. The accuracy required for |
| 1406 | standard alpha composition is relatively low, because the pixels are |
| 1407 | isolated, therefore typically the accuracy loss in storing 8-bit linear |
| 1408 | values is acceptable. (This is not true if the alpha channel is used to |
| 1409 | simulate transparency over large areas - use 16 bits or the PNG mode in |
| 1410 | this case!) This is the 'OPTIMIZED' mode. For this mode a pixel is |
| 1411 | treated as opaque only if the alpha value is equal to the maximum value. |
| 1412 | |
| 1413 | PNG_ALPHA_STANDARD: The data libpng produces is encoded in the |
| 1414 | standard way assumed by most correctly written graphics software. |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1415 | The gamma encoding will be removed by libpng and the |
| 1416 | linear component values will be pre-multiplied by the |
| 1417 | alpha channel. |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1418 | |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1419 | With this format the final image must be re-encoded to |
| 1420 | match the display gamma before the image is displayed. |
| 1421 | If your system doesn't do that, yet still seems to |
| 1422 | perform arithmetic on the pixels without decoding them, |
| 1423 | it is broken - check out the modes below. |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1424 | |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1425 | With PNG_ALPHA_STANDARD libpng always produces linear |
| 1426 | component values, whatever screen_gamma you supply. The |
| 1427 | screen_gamma value is, however, used as a default for |
| 1428 | the file gamma if the PNG file has no gamma information. |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1429 | |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1430 | If you call png_set_gamma() after png_set_alpha_mode() you |
| 1431 | will override the linear encoding. Instead the |
| 1432 | pre-multiplied pixel values will be gamma encoded but |
| 1433 | the alpha channel will still be linear. This may |
| 1434 | actually match the requirements of some broken software, |
| 1435 | but it is unlikely. |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1436 | |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1437 | While linear 8-bit data is often used it has |
| 1438 | insufficient precision for any image with a reasonable |
| 1439 | dynamic range. To avoid problems, and if your software |
| 1440 | supports it, use png_set_expand_16() to force all |
| 1441 | components to 16 bits. |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1442 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1443 | PNG_ALPHA_OPTIMIZED: This mode is the same as PNG_ALPHA_STANDARD |
| 1444 | except that completely opaque pixels are gamma encoded according to |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1445 | the screen_gamma value. Pixels with alpha less than 1.0 |
| 1446 | will still have linear components. |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1447 | |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1448 | Use this format if you have control over your |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 1449 | compositing software and so don't do other arithmetic |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1450 | (such as scaling) on the data you get from libpng. Your |
| 1451 | compositing software can simply copy opaque pixels to |
| 1452 | the output but still has linear values for the |
| 1453 | non-opaque pixels. |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1454 | |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1455 | In normal compositing, where the alpha channel encodes |
| 1456 | partial pixel coverage (as opposed to broad area |
| 1457 | translucency), the inaccuracies of the 8-bit |
| 1458 | representation of non-opaque pixels are irrelevant. |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1459 | |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1460 | You can also try this format if your software is broken; |
| 1461 | it might look better. |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1462 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1463 | PNG_ALPHA_BROKEN: This is PNG_ALPHA_STANDARD; however, all component |
| 1464 | values, including the alpha channel are gamma encoded. This is |
| 1465 | broken because, in practice, no implementation that uses this choice |
| 1466 | correctly undoes the encoding before handling alpha composition. Use this |
| 1467 | choice only if other serious errors in the software or hardware you use |
| 1468 | mandate it. In most cases of broken software or hardware the bug in the |
| 1469 | final display manifests as a subtle halo around composited parts of the |
| 1470 | image. You may not even perceive this as a halo; the composited part of |
| 1471 | the image may simply appear separate from the background, as though it had |
| 1472 | been cut out of paper and pasted on afterward. |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1473 | |
| 1474 | If you don't have to deal with bugs in software or hardware, or if you can fix |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1475 | them, there are three recommended ways of using png_set_alpha_mode(): |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1476 | |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1477 | png_set_alpha_mode(png_ptr, PNG_ALPHA_PNG, |
| 1478 | screen_gamma); |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1479 | |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1480 | You can do color correction on the result (libpng does not currently |
Glenn Randers-Pehrson | 95ba417 | 2011-09-08 12:21:42 -0500 | [diff] [blame] | 1481 | support color correction internally). When you handle the alpha channel |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1482 | you need to undo the gamma encoding and multiply out the alpha. |
| 1483 | |
| 1484 | png_set_alpha_mode(png_ptr, PNG_ALPHA_STANDARD, |
| 1485 | screen_gamma); |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1486 | png_set_expand_16(png_ptr); |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1487 | |
Glenn Randers-Pehrson | 95ba417 | 2011-09-08 12:21:42 -0500 | [diff] [blame] | 1488 | If you are using the high level interface, don't call png_set_expand_16(); |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1489 | instead pass PNG_TRANSFORM_EXPAND_16 to the interface. |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1490 | |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1491 | With this mode you can't do color correction, but you can do arithmetic, |
| 1492 | including composition and scaling, on the data without further processing. |
| 1493 | |
| 1494 | png_set_alpha_mode(png_ptr, PNG_ALPHA_OPTIMIZED, |
| 1495 | screen_gamma); |
| 1496 | |
| 1497 | You can avoid the expansion to 16-bit components with this mode, but you |
| 1498 | lose the ability to scale the image or perform other linear arithmetic. |
| 1499 | All you can do is compose the result onto a matching output. Since this |
Glenn Randers-Pehrson | 95ba417 | 2011-09-08 12:21:42 -0500 | [diff] [blame] | 1500 | mode is libpng-specific you also need to write your own composition |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1501 | software. |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1502 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1503 | The following are examples of calls to png_set_alpha_mode to achieve the |
| 1504 | required overall gamma correction and, where necessary, alpha |
| 1505 | premultiplication. |
| 1506 | |
| 1507 | png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_DEFAULT_sRGB); |
| 1508 | |
Glenn Randers-Pehrson | e4c8312 | 2017-09-23 21:23:59 -0500 | [diff] [blame] | 1509 | Choices for the alpha_mode are |
| 1510 | |
| 1511 | PNG_ALPHA_PNG 0 /* according to the PNG standard */ |
| 1512 | PNG_ALPHA_STANDARD 1 /* according to Porter/Duff */ |
| 1513 | PNG_ALPHA_ASSOCIATED 1 /* as above; this is the normal practice */ |
| 1514 | PNG_ALPHA_PREMULTIPLIED 1 /* as above */ |
| 1515 | PNG_ALPHA_OPTIMIZED 2 /* 'PNG' for opaque pixels, else 'STANDARD' */ |
| 1516 | PNG_ALPHA_BROKEN 3 /* the alpha channel is gamma encoded */ |
| 1517 | |
| 1518 | PNG_ALPHA_PNG is the default libpng handling of the alpha channel. It is not |
| 1519 | pre-multiplied into the color components. In addition the call states |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1520 | that the output is for a sRGB system and causes all PNG files without gAMA |
| 1521 | chunks to be assumed to be encoded using sRGB. |
| 1522 | |
| 1523 | png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_GAMMA_MAC); |
| 1524 | |
| 1525 | In this case the output is assumed to be something like an sRGB conformant |
Unknown | f23b41d | 2017-11-03 00:52:06 -0400 | [diff] [blame] | 1526 | display preceded by a power-law lookup table of power 1.45. This is how |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1527 | early Mac systems behaved. |
| 1528 | |
| 1529 | png_set_alpha_mode(pp, PNG_ALPHA_STANDARD, PNG_GAMMA_LINEAR); |
| 1530 | |
| 1531 | This is the classic Jim Blinn approach and will work in academic |
| 1532 | environments where everything is done by the book. It has the shortcoming |
| 1533 | of assuming that input PNG data with no gamma information is linear - this |
Glenn Randers-Pehrson | e4c8312 | 2017-09-23 21:23:59 -0500 | [diff] [blame] | 1534 | is unlikely to be correct unless the PNG files were generated locally. |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1535 | Most of the time the output precision will be so low as to show |
| 1536 | significant banding in dark areas of the image. |
| 1537 | |
| 1538 | png_set_expand_16(pp); |
| 1539 | png_set_alpha_mode(pp, PNG_ALPHA_STANDARD, PNG_DEFAULT_sRGB); |
| 1540 | |
| 1541 | This is a somewhat more realistic Jim Blinn inspired approach. PNG files |
| 1542 | are assumed to have the sRGB encoding if not marked with a gamma value and |
| 1543 | the output is always 16 bits per component. This permits accurate scaling |
| 1544 | and processing of the data. If you know that your input PNG files were |
| 1545 | generated locally you might need to replace PNG_DEFAULT_sRGB with the |
| 1546 | correct value for your system. |
| 1547 | |
| 1548 | png_set_alpha_mode(pp, PNG_ALPHA_OPTIMIZED, PNG_DEFAULT_sRGB); |
| 1549 | |
| 1550 | If you just need to composite the PNG image onto an existing background |
| 1551 | and if you control the code that does this you can use the optimization |
| 1552 | setting. In this case you just copy completely opaque pixels to the |
| 1553 | output. For pixels that are not completely transparent (you just skip |
| 1554 | those) you do the composition math using png_composite or png_composite_16 |
| 1555 | below then encode the resultant 8-bit or 16-bit values to match the output |
| 1556 | encoding. |
| 1557 | |
| 1558 | Other cases |
| 1559 | |
| 1560 | If neither the PNG nor the standard linear encoding work for you because |
| 1561 | of the software or hardware you use then you have a big problem. The PNG |
| 1562 | case will probably result in halos around the image. The linear encoding |
| 1563 | will probably result in a washed out, too bright, image (it's actually too |
| 1564 | contrasty.) Try the ALPHA_OPTIMIZED mode above - this will probably |
| 1565 | substantially reduce the halos. Alternatively try: |
| 1566 | |
| 1567 | png_set_alpha_mode(pp, PNG_ALPHA_BROKEN, PNG_DEFAULT_sRGB); |
| 1568 | |
| 1569 | This option will also reduce the halos, but there will be slight dark |
| 1570 | halos round the opaque parts of the image where the background is light. |
| 1571 | In the OPTIMIZED mode the halos will be light halos where the background |
| 1572 | is dark. Take your pick - the halos are unavoidable unless you can get |
| 1573 | your hardware/software fixed! (The OPTIMIZED approach is slightly |
| 1574 | faster.) |
| 1575 | |
| 1576 | When the default gamma of PNG files doesn't match the output gamma. |
| 1577 | If you have PNG files with no gamma information png_set_alpha_mode allows |
Unknown | f23b41d | 2017-11-03 00:52:06 -0400 | [diff] [blame] | 1578 | you to provide a default gamma, but it also sets the output gamma to the |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1579 | matching value. If you know your PNG files have a gamma that doesn't |
| 1580 | match the output you can take advantage of the fact that |
| 1581 | png_set_alpha_mode always sets the output gamma but only sets the PNG |
| 1582 | default if it is not already set: |
| 1583 | |
| 1584 | png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_DEFAULT_sRGB); |
| 1585 | png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_GAMMA_MAC); |
| 1586 | |
| 1587 | The first call sets both the default and the output gamma values, the |
| 1588 | second call overrides the output gamma without changing the default. This |
| 1589 | is easier than achieving the same effect with png_set_gamma. You must use |
| 1590 | PNG_ALPHA_PNG for the first call - internal checking in png_set_alpha will |
| 1591 | fire if more than one call to png_set_alpha_mode and png_set_background is |
| 1592 | made in the same read operation, however multiple calls with PNG_ALPHA_PNG |
| 1593 | are ignored. |
| 1594 | |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1595 | If you don't need, or can't handle, the alpha channel you can call |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1596 | png_set_background() to remove it by compositing against a fixed color. Don't |
| 1597 | call png_set_strip_alpha() to do this - it will leave spurious pixel values in |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1598 | transparent parts of this image. |
| 1599 | |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 1600 | png_set_background(png_ptr, &background_color, |
| 1601 | PNG_BACKGROUND_GAMMA_SCREEN, 0, 1); |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1602 | |
| 1603 | The background_color is an RGB or grayscale value according to the data format |
| 1604 | libpng will produce for you. Because you don't yet know the format of the PNG |
Glenn Randers-Pehrson | 95ba417 | 2011-09-08 12:21:42 -0500 | [diff] [blame] | 1605 | file, if you call png_set_background at this point you must arrange for the |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1606 | format produced by libpng to always have 8-bit or 16-bit components and then |
| 1607 | store the color as an 8-bit or 16-bit color as appropriate. The color contains |
| 1608 | separate gray and RGB component values, so you can let libpng produce gray or |
| 1609 | RGB output according to the input format, but low bit depth grayscale images |
Glenn Randers-Pehrson | ab38979 | 2011-07-09 19:35:22 -0500 | [diff] [blame] | 1610 | must always be converted to at least 8-bit format. (Even though low bit depth |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1611 | grayscale images can't have an alpha channel they can have a transparent |
| 1612 | color!) |
| 1613 | |
| 1614 | You set the transforms you need later, either as flags to the high level |
| 1615 | interface or libpng API calls for the low level interface. For reference the |
Glenn Randers-Pehrson | 733b131 | 2011-06-15 13:21:01 -0500 | [diff] [blame] | 1616 | settings and API calls required are: |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1617 | |
| 1618 | 8-bit values: |
Glenn Randers-Pehrson | fb29e51 | 2011-06-17 20:38:24 -0500 | [diff] [blame] | 1619 | PNG_TRANSFORM_SCALE_16 | PNG_EXPAND |
| 1620 | png_set_expand(png_ptr); png_set_scale_16(png_ptr); |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1621 | |
Glenn Randers-Pehrson | 733b131 | 2011-06-15 13:21:01 -0500 | [diff] [blame] | 1622 | If you must get exactly the same inaccurate results |
| 1623 | produced by default in versions prior to libpng-1.5.4, |
Glenn Randers-Pehrson | fb29e51 | 2011-06-17 20:38:24 -0500 | [diff] [blame] | 1624 | use PNG_TRANSFORM_STRIP_16 and png_set_strip_16(png_ptr) |
Glenn Randers-Pehrson | 733b131 | 2011-06-15 13:21:01 -0500 | [diff] [blame] | 1625 | instead. |
| 1626 | |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1627 | 16-bit values: |
| 1628 | PNG_TRANSFORM_EXPAND_16 |
| 1629 | png_set_expand_16(png_ptr); |
| 1630 | |
| 1631 | In either case palette image data will be expanded to RGB. If you just want |
| 1632 | color data you can add PNG_TRANSFORM_GRAY_TO_RGB or png_set_gray_to_rgb(png_ptr) |
| 1633 | to the list. |
| 1634 | |
| 1635 | Calling png_set_background before the PNG file header is read will not work |
Glenn Randers-Pehrson | 733b131 | 2011-06-15 13:21:01 -0500 | [diff] [blame] | 1636 | prior to libpng-1.5.4. Because the failure may result in unexpected warnings or |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1637 | errors it is therefore much safer to call png_set_background after the head has |
Glenn Randers-Pehrson | 733b131 | 2011-06-15 13:21:01 -0500 | [diff] [blame] | 1638 | been read. Unfortunately this means that prior to libpng-1.5.4 it cannot be |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1639 | used with the high level interface. |
| 1640 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1641 | .SS The high-level read interface |
| 1642 | |
| 1643 | At this point there are two ways to proceed; through the high-level |
| 1644 | read interface, or through a sequence of low-level read operations. |
| 1645 | You can use the high-level interface if (a) you are willing to read |
| 1646 | the entire image into memory, and (b) the input transformations |
| 1647 | you want to do are limited to the following set: |
| 1648 | |
| 1649 | PNG_TRANSFORM_IDENTITY No transformation |
Glenn Randers-Pehrson | fb29e51 | 2011-06-17 20:38:24 -0500 | [diff] [blame] | 1650 | PNG_TRANSFORM_SCALE_16 Strip 16-bit samples to |
| 1651 | 8-bit accurately |
| 1652 | PNG_TRANSFORM_STRIP_16 Chop 16-bit samples to |
| 1653 | 8-bit less accurately |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1654 | PNG_TRANSFORM_STRIP_ALPHA Discard the alpha channel |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 1655 | PNG_TRANSFORM_PACKING Expand 1, 2 and 4-bit |
| 1656 | samples to bytes |
| 1657 | PNG_TRANSFORM_PACKSWAP Change order of packed |
| 1658 | pixels to LSB first |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1659 | PNG_TRANSFORM_EXPAND Perform set_expand() |
| 1660 | PNG_TRANSFORM_INVERT_MONO Invert monochrome images |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 1661 | PNG_TRANSFORM_SHIFT Normalize pixels to the |
| 1662 | sBIT depth |
| 1663 | PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA |
| 1664 | to BGRA |
| 1665 | PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA |
| 1666 | to AG |
| 1667 | PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity |
| 1668 | to transparency |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1669 | PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples |
Glenn Randers-Pehrson | 99708d5 | 2009-06-29 17:30:00 -0500 | [diff] [blame] | 1670 | PNG_TRANSFORM_GRAY_TO_RGB Expand grayscale samples |
| 1671 | to RGB (or GA to RGBA) |
John Bowler | a9b3419 | 2011-05-08 19:46:51 -0500 | [diff] [blame] | 1672 | PNG_TRANSFORM_EXPAND_16 Expand samples to 16 bits |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1673 | |
| 1674 | (This excludes setting a background color, doing gamma transformation, |
Glenn Randers-Pehrson | 3cd7cff | 2010-04-16 19:27:08 -0500 | [diff] [blame] | 1675 | quantizing, and setting filler.) If this is the case, simply do this: |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1676 | |
| 1677 | png_read_png(png_ptr, info_ptr, png_transforms, NULL) |
| 1678 | |
Glenn Randers-Pehrson | f210a05 | 2009-11-12 10:02:24 -0600 | [diff] [blame] | 1679 | where png_transforms is an integer containing the bitwise OR of some |
| 1680 | set of transformation flags. This call is equivalent to png_read_info(), |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1681 | followed the set of transformations indicated by the transform mask, |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 1682 | then png_read_image(), and finally png_read_end(). |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1683 | |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 1684 | (The final parameter of this call is not yet used. Someday it might point |
| 1685 | to transformation parameters required by some future input transform.) |
| 1686 | |
Glenn Randers-Pehrson | a4981d4 | 2004-08-25 22:00:45 -0500 | [diff] [blame] | 1687 | You must use png_transforms and not call any png_set_transform() functions |
| 1688 | when you use png_read_png(). |
| 1689 | |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 1690 | After you have called png_read_png(), you can retrieve the image data |
| 1691 | with |
| 1692 | |
| 1693 | row_pointers = png_get_rows(png_ptr, info_ptr); |
| 1694 | |
| 1695 | where row_pointers is an array of pointers to the pixel data for each row: |
| 1696 | |
| 1697 | png_bytep row_pointers[height]; |
| 1698 | |
| 1699 | If you know your image size and pixel size ahead of time, you can allocate |
| 1700 | row_pointers prior to calling png_read_png() with |
| 1701 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1702 | if (height > PNG_UINT_32_MAX/(sizeof (png_byte))) |
Glenn Randers-Pehrson | 5fea36f | 2004-07-28 08:20:44 -0500 | [diff] [blame] | 1703 | png_error (png_ptr, |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1704 | "Image is too tall to process in memory"); |
| 1705 | |
Glenn Randers-Pehrson | 5fea36f | 2004-07-28 08:20:44 -0500 | [diff] [blame] | 1706 | if (width > PNG_UINT_32_MAX/pixel_size) |
| 1707 | png_error (png_ptr, |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1708 | "Image is too wide to process in memory"); |
| 1709 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 1710 | row_pointers = png_malloc(png_ptr, |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1711 | height*(sizeof (png_bytep))); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1712 | |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 1713 | for (int i=0; i<height, i++) |
| 1714 | row_pointers[i]=NULL; /* security precaution */ |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1715 | |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 1716 | for (int i=0; i<height, i++) |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 1717 | row_pointers[i]=png_malloc(png_ptr, |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1718 | width*pixel_size); |
| 1719 | |
Glenn Randers-Pehrson | d56aca7 | 2000-11-23 11:51:42 -0600 | [diff] [blame] | 1720 | png_set_rows(png_ptr, info_ptr, &row_pointers); |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 1721 | |
| 1722 | Alternatively you could allocate your image in one big block and define |
Glenn Randers-Pehrson | 53f22ae | 2017-04-22 15:21:58 -0500 | [diff] [blame] | 1723 | row_pointers[i] to point into the proper places in your block, but first |
| 1724 | be sure that your platform is able to allocate such a large buffer: |
| 1725 | |
| 1726 | /* Guard against integer overflow */ |
| 1727 | if (height > PNG_SIZE_MAX/(width*pixel_size)) { |
| 1728 | png_error(png_ptr,"image_data buffer would be too large"); |
| 1729 | } |
| 1730 | |
| 1731 | png_bytep buffer=png_malloc(png_ptr,height*width*pixel_size); |
| 1732 | |
| 1733 | for (int i=0; i<height, i++) |
| 1734 | row_pointers[i]=buffer+i*width*pixel_size; |
| 1735 | |
| 1736 | png_set_rows(png_ptr, info_ptr, &row_pointers); |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 1737 | |
| 1738 | If you use png_set_rows(), the application is responsible for freeing |
| 1739 | row_pointers (and row_pointers[i], if they were separately allocated). |
| 1740 | |
| 1741 | If you don't allocate row_pointers ahead of time, png_read_png() will |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1742 | do it, and it'll be free'ed by libpng when you call png_destroy_*(). |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1743 | |
| 1744 | .SS The low-level read interface |
| 1745 | |
| 1746 | If you are going the low-level route, you are now ready to read all |
| 1747 | the file information up to the actual image data. You do this with a |
| 1748 | call to png_read_info(). |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1749 | |
| 1750 | png_read_info(png_ptr, info_ptr); |
| 1751 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1752 | This will process all chunks up to but not including the image data. |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 1753 | |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1754 | This also copies some of the data from the PNG file into the decode structure |
| 1755 | for use in later transformations. Important information copied in is: |
| 1756 | |
| 1757 | 1) The PNG file gamma from the gAMA chunk. This overwrites the default value |
| 1758 | provided by an earlier call to png_set_gamma or png_set_alpha_mode. |
| 1759 | |
Glenn Randers-Pehrson | 733b131 | 2011-06-15 13:21:01 -0500 | [diff] [blame] | 1760 | 2) Prior to libpng-1.5.4 the background color from a bKGd chunk. This |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1761 | damages the information provided by an earlier call to png_set_background |
Glenn Randers-Pehrson | ab38979 | 2011-07-09 19:35:22 -0500 | [diff] [blame] | 1762 | resulting in unexpected behavior. Libpng-1.5.4 no longer does this. |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 1763 | |
| 1764 | 3) The number of significant bits in each component value. Libpng uses this to |
| 1765 | optimize gamma handling by reducing the internal lookup table sizes. |
| 1766 | |
| 1767 | 4) The transparent color information from a tRNS chunk. This can be modified by |
| 1768 | a later call to png_set_tRNS. |
| 1769 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 1770 | .SS Querying the info structure |
| 1771 | |
| 1772 | Functions are used to get the information from the info_ptr once it |
| 1773 | has been read. Note that these fields may not be completely filled |
| 1774 | in until png_read_end() has read the chunk data following the image. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1775 | |
| 1776 | png_get_IHDR(png_ptr, info_ptr, &width, &height, |
| 1777 | &bit_depth, &color_type, &interlace_type, |
Glenn Randers-Pehrson | 408b421 | 2000-12-18 09:33:57 -0600 | [diff] [blame] | 1778 | &compression_type, &filter_method); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1779 | |
| 1780 | width - holds the width of the image |
| 1781 | in pixels (up to 2^31). |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1782 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1783 | height - holds the height of the image |
| 1784 | in pixels (up to 2^31). |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1785 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1786 | bit_depth - holds the bit depth of one of the |
| 1787 | image channels. (valid values are |
| 1788 | 1, 2, 4, 8, 16 and depend also on |
| 1789 | the color_type. See also |
| 1790 | significant bits (sBIT) below). |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1791 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1792 | color_type - describes which color/alpha channels |
| 1793 | are present. |
| 1794 | PNG_COLOR_TYPE_GRAY |
| 1795 | (bit depths 1, 2, 4, 8, 16) |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 1796 | PNG_COLOR_TYPE_GRAY_ALPHA |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1797 | (bit depths 8, 16) |
| 1798 | PNG_COLOR_TYPE_PALETTE |
| 1799 | (bit depths 1, 2, 4, 8) |
| 1800 | PNG_COLOR_TYPE_RGB |
| 1801 | (bit_depths 8, 16) |
| 1802 | PNG_COLOR_TYPE_RGB_ALPHA |
| 1803 | (bit_depths 8, 16) |
| 1804 | |
| 1805 | PNG_COLOR_MASK_PALETTE |
| 1806 | PNG_COLOR_MASK_COLOR |
| 1807 | PNG_COLOR_MASK_ALPHA |
| 1808 | |
Glenn Randers-Pehrson | 2cb633b | 2011-01-21 08:31:29 -0600 | [diff] [blame] | 1809 | interlace_type - (PNG_INTERLACE_NONE or |
| 1810 | PNG_INTERLACE_ADAM7) |
| 1811 | |
| 1812 | compression_type - (must be PNG_COMPRESSION_TYPE_BASE |
| 1813 | for PNG 1.0) |
| 1814 | |
Glenn Randers-Pehrson | 408b421 | 2000-12-18 09:33:57 -0600 | [diff] [blame] | 1815 | filter_method - (must be PNG_FILTER_TYPE_BASE |
| 1816 | for PNG 1.0, and can also be |
| 1817 | PNG_INTRAPIXEL_DIFFERENCING if |
| 1818 | the PNG datastream is embedded in |
| 1819 | a MNG-1.0 datastream) |
Glenn Randers-Pehrson | 0bfb58f | 2009-09-30 23:07:22 -0500 | [diff] [blame] | 1820 | |
Glenn Randers-Pehrson | 60a7506 | 2015-02-18 12:24:46 -0600 | [diff] [blame] | 1821 | Any of width, height, color_type, bit_depth, |
| 1822 | interlace_type, compression_type, or filter_method can |
| 1823 | be NULL if you are not interested in their values. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1824 | |
Glenn Randers-Pehrson | 0bfb58f | 2009-09-30 23:07:22 -0500 | [diff] [blame] | 1825 | Note that png_get_IHDR() returns 32-bit data into |
| 1826 | the application's width and height variables. |
Glenn Randers-Pehrson | 60a7506 | 2015-02-18 12:24:46 -0600 | [diff] [blame] | 1827 | This is an unsafe situation if these are not png_uint_32 |
Glenn Randers-Pehrson | 0bfb58f | 2009-09-30 23:07:22 -0500 | [diff] [blame] | 1828 | variables. In such situations, the |
| 1829 | png_get_image_width() and png_get_image_height() |
| 1830 | functions described below are safer. |
| 1831 | |
| 1832 | width = png_get_image_width(png_ptr, |
| 1833 | info_ptr); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1834 | |
Glenn Randers-Pehrson | 0bfb58f | 2009-09-30 23:07:22 -0500 | [diff] [blame] | 1835 | height = png_get_image_height(png_ptr, |
| 1836 | info_ptr); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1837 | |
Glenn Randers-Pehrson | 0bfb58f | 2009-09-30 23:07:22 -0500 | [diff] [blame] | 1838 | bit_depth = png_get_bit_depth(png_ptr, |
| 1839 | info_ptr); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1840 | |
Glenn Randers-Pehrson | 0bfb58f | 2009-09-30 23:07:22 -0500 | [diff] [blame] | 1841 | color_type = png_get_color_type(png_ptr, |
| 1842 | info_ptr); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1843 | |
Glenn Randers-Pehrson | 2cb633b | 2011-01-21 08:31:29 -0600 | [diff] [blame] | 1844 | interlace_type = png_get_interlace_type(png_ptr, |
Glenn Randers-Pehrson | 0bfb58f | 2009-09-30 23:07:22 -0500 | [diff] [blame] | 1845 | info_ptr); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1846 | |
Glenn Randers-Pehrson | 0bfb58f | 2009-09-30 23:07:22 -0500 | [diff] [blame] | 1847 | compression_type = png_get_compression_type(png_ptr, |
| 1848 | info_ptr); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1849 | |
Glenn Randers-Pehrson | 2cb633b | 2011-01-21 08:31:29 -0600 | [diff] [blame] | 1850 | filter_method = png_get_filter_type(png_ptr, |
Glenn Randers-Pehrson | 0bfb58f | 2009-09-30 23:07:22 -0500 | [diff] [blame] | 1851 | info_ptr); |
| 1852 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1853 | channels = png_get_channels(png_ptr, info_ptr); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1854 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1855 | channels - number of channels of info for the |
| 1856 | color type (valid values are 1 (GRAY, |
| 1857 | PALETTE), 2 (GRAY_ALPHA), 3 (RGB), |
| 1858 | 4 (RGB_ALPHA or RGB + filler byte)) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1859 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1860 | rowbytes = png_get_rowbytes(png_ptr, info_ptr); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1861 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1862 | rowbytes - number of bytes needed to hold a row |
Glenn Randers-Pehrson | b5c16f8 | 2017-07-03 11:11:44 -0500 | [diff] [blame] | 1863 | This value, the bit_depth, color_type, |
| 1864 | and the number of channels can change |
| 1865 | if you use transforms such as |
| 1866 | png_set_expand(). See |
| 1867 | png_read_update_info(), below. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1868 | |
| 1869 | signature = png_get_signature(png_ptr, info_ptr); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1870 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1871 | signature - holds the signature read from the |
| 1872 | file (if any). The data is kept in |
| 1873 | the same offset it would be if the |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 1874 | whole signature were read (i.e. if an |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1875 | application had already read in 4 |
| 1876 | bytes of signature before starting |
| 1877 | libpng, the remaining 4 bytes would |
| 1878 | be in signature[4] through signature[7] |
| 1879 | (see png_set_sig_bytes())). |
| 1880 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1881 | These are also important, but their validity depends on whether the chunk |
| 1882 | has been read. The png_get_valid(png_ptr, info_ptr, PNG_INFO_<chunk>) and |
| 1883 | png_get_<chunk>(png_ptr, info_ptr, ...) functions return non-zero if the |
| 1884 | data has been read, or zero if it is missing. The parameters to the |
Glenn Randers-Pehrson | f210a05 | 2009-11-12 10:02:24 -0600 | [diff] [blame] | 1885 | png_get_<chunk> are set directly if they are simple data types, or a |
| 1886 | pointer into the info_ptr is returned for any complex types. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1887 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 1888 | The colorspace data from gAMA, cHRM, sRGB, iCCP, and sBIT chunks |
| 1889 | is simply returned to give the application information about how the |
| 1890 | image was encoded. Libpng itself only does transformations using the file |
| 1891 | gamma when combining semitransparent pixels with the background color, and, |
| 1892 | since libpng-1.6.0, when converting between 8-bit sRGB and 16-bit linear pixels |
| 1893 | within the simplified API. Libpng also uses the file gamma when converting |
| 1894 | RGB to gray, beginning with libpng-1.0.5, if the application calls |
| 1895 | png_set_rgb_to_gray()). |
| 1896 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1897 | png_get_PLTE(png_ptr, info_ptr, &palette, |
| 1898 | &num_palette); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1899 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1900 | palette - the palette for the file |
| 1901 | (array of png_color) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1902 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1903 | num_palette - number of entries in the palette |
| 1904 | |
Glenn Randers-Pehrson | 8d0bc0f | 2011-01-25 22:15:58 -0600 | [diff] [blame] | 1905 | png_get_gAMA(png_ptr, info_ptr, &file_gamma); |
Glenn Randers-Pehrson | 2774238 | 2011-01-27 09:37:34 -0600 | [diff] [blame] | 1906 | png_get_gAMA_fixed(png_ptr, info_ptr, &int_file_gamma); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1907 | |
Glenn Randers-Pehrson | 8d0bc0f | 2011-01-25 22:15:58 -0600 | [diff] [blame] | 1908 | file_gamma - the gamma at which the file is |
| 1909 | written (PNG_INFO_gAMA) |
| 1910 | |
| 1911 | int_file_gamma - 100,000 times the gamma at which the |
| 1912 | file is written |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1913 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 1914 | png_get_cHRM(png_ptr, info_ptr, &white_x, &white_y, &red_x, |
| 1915 | &red_y, &green_x, &green_y, &blue_x, &blue_y) |
| 1916 | png_get_cHRM_XYZ(png_ptr, info_ptr, &red_X, &red_Y, &red_Z, |
| 1917 | &green_X, &green_Y, &green_Z, &blue_X, &blue_Y, |
| 1918 | &blue_Z) |
| 1919 | png_get_cHRM_fixed(png_ptr, info_ptr, &int_white_x, |
| 1920 | &int_white_y, &int_red_x, &int_red_y, |
| 1921 | &int_green_x, &int_green_y, &int_blue_x, |
| 1922 | &int_blue_y) |
John Bowler | bbd17bd | 2011-08-25 17:48:18 -0500 | [diff] [blame] | 1923 | png_get_cHRM_XYZ_fixed(png_ptr, info_ptr, &int_red_X, &int_red_Y, |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 1924 | &int_red_Z, &int_green_X, &int_green_Y, |
| 1925 | &int_green_Z, &int_blue_X, &int_blue_Y, |
| 1926 | &int_blue_Z) |
John Bowler | bbd17bd | 2011-08-25 17:48:18 -0500 | [diff] [blame] | 1927 | |
| 1928 | {white,red,green,blue}_{x,y} |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 1929 | A color space encoding specified using the |
| 1930 | chromaticities of the end points and the |
| 1931 | white point. (PNG_INFO_cHRM) |
John Bowler | bbd17bd | 2011-08-25 17:48:18 -0500 | [diff] [blame] | 1932 | |
| 1933 | {red,green,blue}_{X,Y,Z} |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 1934 | A color space encoding specified using the |
| 1935 | encoding end points - the CIE tristimulus |
| 1936 | specification of the intended color of the red, |
| 1937 | green and blue channels in the PNG RGB data. |
| 1938 | The white point is simply the sum of the three |
| 1939 | end points. (PNG_INFO_cHRM) |
John Bowler | bbd17bd | 2011-08-25 17:48:18 -0500 | [diff] [blame] | 1940 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1941 | png_get_sRGB(png_ptr, info_ptr, &srgb_intent); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1942 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 1943 | srgb_intent - the rendering intent (PNG_INFO_sRGB) |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1944 | The presence of the sRGB chunk |
| 1945 | means that the pixel data is in the |
| 1946 | sRGB color space. This chunk also |
| 1947 | implies specific values of gAMA and |
| 1948 | cHRM. |
| 1949 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 1950 | png_get_iCCP(png_ptr, info_ptr, &name, |
| 1951 | &compression_type, &profile, &proflen); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1952 | |
Glenn Randers-Pehrson | 4a5a1ec | 2011-01-15 11:43:28 -0600 | [diff] [blame] | 1953 | name - The profile name. |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1954 | |
Glenn Randers-Pehrson | 4a5a1ec | 2011-01-15 11:43:28 -0600 | [diff] [blame] | 1955 | compression_type - The compression type; always |
| 1956 | PNG_COMPRESSION_TYPE_BASE for PNG 1.0. |
| 1957 | You may give NULL to this argument to |
| 1958 | ignore it. |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1959 | |
Glenn Randers-Pehrson | 4a5a1ec | 2011-01-15 11:43:28 -0600 | [diff] [blame] | 1960 | profile - International Color Consortium color |
| 1961 | profile data. May contain NULs. |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1962 | |
Glenn Randers-Pehrson | 4a5a1ec | 2011-01-15 11:43:28 -0600 | [diff] [blame] | 1963 | proflen - length of profile data in bytes. |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 1964 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1965 | png_get_sBIT(png_ptr, info_ptr, &sig_bit); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1966 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1967 | sig_bit - the number of significant bits for |
| 1968 | (PNG_INFO_sBIT) each of the gray, |
| 1969 | red, green, and blue channels, |
| 1970 | whichever are appropriate for the |
| 1971 | given color type (png_color_16) |
| 1972 | |
Glenn Randers-Pehrson | 866b62a | 2009-08-08 16:33:14 -0500 | [diff] [blame] | 1973 | png_get_tRNS(png_ptr, info_ptr, &trans_alpha, |
| 1974 | &num_trans, &trans_color); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1975 | |
Glenn Randers-Pehrson | 866b62a | 2009-08-08 16:33:14 -0500 | [diff] [blame] | 1976 | trans_alpha - array of alpha (transparency) |
| 1977 | entries for palette (PNG_INFO_tRNS) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1978 | |
Glenn Randers-Pehrson | f3c51e4 | 2011-01-15 10:25:25 -0600 | [diff] [blame] | 1979 | num_trans - number of transparent entries |
| 1980 | (PNG_INFO_tRNS) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1981 | |
Glenn Randers-Pehrson | 56f6396 | 2008-10-06 10:16:17 -0500 | [diff] [blame] | 1982 | trans_color - graylevel or color sample values of |
Glenn Randers-Pehrson | 3d5a520 | 2000-07-01 15:37:28 -0500 | [diff] [blame] | 1983 | the single transparent color for |
| 1984 | non-paletted images (PNG_INFO_tRNS) |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1985 | |
Glenn Randers-Pehrson | 6f89dff | 2017-08-03 10:27:09 -0500 | [diff] [blame] | 1986 | png_get_eXIf_1(png_ptr, info_ptr, &num_exif, &exif); |
Glenn Randers-Pehrson | 68cb0aa | 2017-07-13 11:19:53 -0500 | [diff] [blame] | 1987 | (PNG_INFO_eXIf) |
| 1988 | |
| 1989 | exif - Exif profile (array of png_byte) |
| 1990 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1991 | png_get_hIST(png_ptr, info_ptr, &hist); |
| 1992 | (PNG_INFO_hIST) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1993 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1994 | hist - histogram of palette (array of |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 1995 | png_uint_16) |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1996 | |
| 1997 | png_get_tIME(png_ptr, info_ptr, &mod_time); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 1998 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 1999 | mod_time - time image was last modified |
| 2000 | (PNG_VALID_tIME) |
| 2001 | |
| 2002 | png_get_bKGD(png_ptr, info_ptr, &background); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2003 | |
Glenn Randers-Pehrson | ab38979 | 2011-07-09 19:35:22 -0500 | [diff] [blame] | 2004 | background - background color (of type |
| 2005 | png_color_16p) (PNG_VALID_bKGD) |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 2006 | valid 16-bit red, green and blue |
| 2007 | values, regardless of color_type |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2008 | |
Glenn Randers-Pehrson | a77ef62 | 2000-02-18 13:48:52 -0600 | [diff] [blame] | 2009 | num_comments = png_get_text(png_ptr, info_ptr, |
| 2010 | &text_ptr, &num_text); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2011 | |
Glenn Randers-Pehrson | a77ef62 | 2000-02-18 13:48:52 -0600 | [diff] [blame] | 2012 | num_comments - number of comments |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2013 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2014 | text_ptr - array of png_text holding image |
| 2015 | comments |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2016 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2017 | text_ptr[i].compression - type of compression used |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 2018 | on "text" PNG_TEXT_COMPRESSION_NONE |
| 2019 | PNG_TEXT_COMPRESSION_zTXt |
| 2020 | PNG_ITXT_COMPRESSION_NONE |
| 2021 | PNG_ITXT_COMPRESSION_zTXt |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2022 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2023 | text_ptr[i].key - keyword for comment. Must contain |
| 2024 | 1-79 characters. |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2025 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2026 | text_ptr[i].text - text comments for current |
Glenn Randers-Pehrson | 1ef65b6 | 2000-05-12 06:19:53 -0500 | [diff] [blame] | 2027 | keyword. Can be empty. |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2028 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2029 | text_ptr[i].text_length - length of text string, |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 2030 | after decompression, 0 for iTXt |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2031 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2032 | text_ptr[i].itxt_length - length of itxt string, |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 2033 | after decompression, 0 for tEXt/zTXt |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2034 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2035 | text_ptr[i].lang - language of comment (empty |
| 2036 | string for unknown). |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2037 | |
Glenn Randers-Pehrson | 73d57cb | 2002-03-25 18:49:08 -0600 | [diff] [blame] | 2038 | text_ptr[i].lang_key - keyword in UTF-8 |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2039 | (empty string for unknown). |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2040 | |
Glenn Randers-Pehrson | 8f5846f | 2009-10-31 21:31:08 -0500 | [diff] [blame] | 2041 | Note that the itxt_length, lang, and lang_key |
Glenn Randers-Pehrson | 680da02 | 2011-11-21 17:05:41 -0600 | [diff] [blame] | 2042 | members of the text_ptr structure only exist when the |
| 2043 | library is built with iTXt chunk support. Prior to |
| 2044 | libpng-1.4.0 the library was built by default without |
| 2045 | iTXt support. Also note that when iTXt is supported, |
| 2046 | they contain NULL pointers when the "compression" |
| 2047 | field contains PNG_TEXT_COMPRESSION_NONE or |
| 2048 | PNG_TEXT_COMPRESSION_zTXt. |
Glenn Randers-Pehrson | 8f5846f | 2009-10-31 21:31:08 -0500 | [diff] [blame] | 2049 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2050 | num_text - number of comments (same as |
| 2051 | num_comments; you can put NULL here |
| 2052 | to avoid the duplication) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2053 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2054 | Note while png_set_text() will accept text, language, |
| 2055 | and translated keywords that can be NULL pointers, the |
| 2056 | structure returned by png_get_text will always contain |
| 2057 | regular zero-terminated C strings. They might be |
| 2058 | empty strings but they will never be NULL pointers. |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2059 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2060 | num_spalettes = png_get_sPLT(png_ptr, info_ptr, |
| 2061 | &palette_ptr); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2062 | |
| 2063 | num_spalettes - number of sPLT chunks read. |
| 2064 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2065 | palette_ptr - array of palette structures holding |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2066 | contents of one or more sPLT chunks |
| 2067 | read. |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 2068 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2069 | png_get_oFFs(png_ptr, info_ptr, &offset_x, &offset_y, |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2070 | &unit_type); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2071 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2072 | offset_x - positive offset from the left edge |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 2073 | of the screen (can be negative) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2074 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2075 | offset_y - positive offset from the top edge |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 2076 | of the screen (can be negative) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2077 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2078 | unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER |
| 2079 | |
| 2080 | png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y, |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2081 | &unit_type); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2082 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2083 | res_x - pixels/unit physical resolution in |
| 2084 | x direction |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2085 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2086 | res_y - pixels/unit physical resolution in |
| 2087 | x direction |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2088 | |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 2089 | unit_type - PNG_RESOLUTION_UNKNOWN, |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2090 | PNG_RESOLUTION_METER |
| 2091 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2092 | png_get_sCAL(png_ptr, info_ptr, &unit, &width, |
| 2093 | &height) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2094 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2095 | unit - physical scale units (an integer) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2096 | |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 2097 | width - width of a pixel in physical scale units |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2098 | |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 2099 | height - height of a pixel in physical scale units |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2100 | (width and height are doubles) |
| 2101 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2102 | png_get_sCAL_s(png_ptr, info_ptr, &unit, &width, |
| 2103 | &height) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2104 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2105 | unit - physical scale units (an integer) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2106 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2107 | width - width of a pixel in physical scale units |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 2108 | (expressed as a string) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2109 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2110 | height - height of a pixel in physical scale units |
| 2111 | (width and height are strings like "2.54") |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 2112 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2113 | num_unknown_chunks = png_get_unknown_chunks(png_ptr, |
| 2114 | info_ptr, &unknowns) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2115 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2116 | unknowns - array of png_unknown_chunk |
| 2117 | structures holding unknown chunks |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2118 | |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 2119 | unknowns[i].name - name of unknown chunk |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2120 | |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 2121 | unknowns[i].data - data of unknown chunk |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2122 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2123 | unknowns[i].size - size of unknown chunk's data |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2124 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 2125 | unknowns[i].location - position of chunk in file |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 2126 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2127 | The value of "i" corresponds to the order in which the |
| 2128 | chunks were read from the PNG file or inserted with the |
| 2129 | png_set_unknown_chunks() function. |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2130 | |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 2131 | The value of "location" is a bitwise "or" of |
| 2132 | |
| 2133 | PNG_HAVE_IHDR (0x01) |
| 2134 | PNG_HAVE_PLTE (0x02) |
| 2135 | PNG_AFTER_IDAT (0x08) |
| 2136 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2137 | The data from the pHYs chunk can be retrieved in several convenient |
| 2138 | forms: |
| 2139 | |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 2140 | res_x = png_get_x_pixels_per_meter(png_ptr, |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2141 | info_ptr) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2142 | |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 2143 | res_y = png_get_y_pixels_per_meter(png_ptr, |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2144 | info_ptr) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2145 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2146 | res_x_and_y = png_get_pixels_per_meter(png_ptr, |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2147 | info_ptr) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2148 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2149 | res_x = png_get_x_pixels_per_inch(png_ptr, |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2150 | info_ptr) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2151 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2152 | res_y = png_get_y_pixels_per_inch(png_ptr, |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2153 | info_ptr) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2154 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2155 | res_x_and_y = png_get_pixels_per_inch(png_ptr, |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2156 | info_ptr) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2157 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2158 | aspect_ratio = png_get_pixel_aspect_ratio(png_ptr, |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2159 | info_ptr) |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2160 | |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2161 | Each of these returns 0 [signifying "unknown"] if |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2162 | the data is not present or if res_x is 0; |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2163 | res_x_and_y is 0 if res_x != res_y |
| 2164 | |
| 2165 | Note that because of the way the resolutions are |
| 2166 | stored internally, the inch conversions won't |
| 2167 | come out to exactly even number. For example, |
| 2168 | 72 dpi is stored as 0.28346 pixels/meter, and |
| 2169 | when this is retrieved it is 71.9988 dpi, so |
| 2170 | be sure to round the returned value appropriately |
Glenn Randers-Pehrson | c36bb79 | 2011-02-12 09:49:07 -0600 | [diff] [blame] | 2171 | if you want to display a reasonable-looking result. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2172 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2173 | The data from the oFFs chunk can be retrieved in several convenient |
| 2174 | forms: |
| 2175 | |
| 2176 | x_offset = png_get_x_offset_microns(png_ptr, info_ptr); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2177 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2178 | y_offset = png_get_y_offset_microns(png_ptr, info_ptr); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2179 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2180 | x_offset = png_get_x_offset_inches(png_ptr, info_ptr); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2181 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2182 | y_offset = png_get_y_offset_inches(png_ptr, info_ptr); |
| 2183 | |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2184 | Each of these returns 0 [signifying "unknown" if both |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2185 | x and y are 0] if the data is not present or if the |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2186 | chunk is present but the unit is the pixel. The |
| 2187 | remark about inexact inch conversions applies here |
| 2188 | as well, because a value in inches can't always be |
| 2189 | converted to microns and back without some loss |
| 2190 | of precision. |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2191 | |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2192 | For more information, see the |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2193 | PNG specification for chunk contents. Be careful with trusting |
| 2194 | rowbytes, as some of the transformations could increase the space |
| 2195 | needed to hold a row (expand, filler, gray_to_rgb, etc.). |
| 2196 | See png_read_update_info(), below. |
| 2197 | |
| 2198 | A quick word about text_ptr and num_text. PNG stores comments in |
| 2199 | keyword/text pairs, one pair per chunk, with no limit on the number |
| 2200 | of text chunks, and a 2^31 byte limit on their size. While there are |
| 2201 | suggested keywords, there is no requirement to restrict the use to these |
| 2202 | strings. It is strongly suggested that keywords and text be sensible |
| 2203 | to humans (that's the point), so don't use abbreviations. Non-printing |
| 2204 | symbols are not allowed. See the PNG specification for more details. |
| 2205 | There is also no requirement to have text after the keyword. |
| 2206 | |
| 2207 | Keywords should be limited to 79 Latin-1 characters without leading or |
| 2208 | trailing spaces, but non-consecutive spaces are allowed within the |
| 2209 | keyword. It is possible to have the same keyword any number of times. |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 2210 | The text_ptr is an array of png_text structures, each holding a |
| 2211 | pointer to a language string, a pointer to a keyword and a pointer to |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2212 | a text string. The text string, language code, and translated |
| 2213 | keyword may be empty or NULL pointers. The keyword/text |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 2214 | pairs are put into the array in the order that they are received. |
| 2215 | However, some or all of the text chunks may be after the image, so, to |
| 2216 | make sure you have read all the text chunks, don't mess with these |
| 2217 | until after you read the stuff after the image. This will be |
| 2218 | mentioned again below in the discussion that goes with png_read_end(). |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2219 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 2220 | .SS Input transformations |
| 2221 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2222 | After you've read the header information, you can set up the library |
| 2223 | to handle any special transformations of the image data. The various |
| 2224 | ways to transform the data will be described in the order that they |
| 2225 | should occur. This is important, as some of these change the color |
| 2226 | type and/or bit depth of the data, and some others only work on |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2227 | certain color types and bit depths. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2228 | |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2229 | Transformations you request are ignored if they don't have any meaning for a |
| 2230 | particular input data format. However some transformations can have an effect |
| 2231 | as a result of a previous transformation. If you specify a contradictory set of |
| 2232 | transformations, for example both adding and removing the alpha channel, you |
| 2233 | cannot predict the final result. |
| 2234 | |
| 2235 | The color used for the transparency values should be supplied in the same |
| 2236 | format/depth as the current image data. It is stored in the same format/depth |
| 2237 | as the image data in a tRNS chunk, so this is what libpng expects for this data. |
| 2238 | |
| 2239 | The color used for the background value depends on the need_expand argument as |
| 2240 | described below. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2241 | |
| 2242 | Data will be decoded into the supplied row buffers packed into bytes |
| 2243 | unless the library has been told to transform it into another format. |
| 2244 | For example, 4 bit/pixel paletted or grayscale data will be returned |
Glenn Randers-Pehrson | efe4e5d | 2015-09-23 22:08:04 -0500 | [diff] [blame] | 2245 | 2 pixels/byte with the leftmost pixel in the high-order bits of the byte, |
| 2246 | unless png_set_packing() is called. 8-bit RGB data will be stored |
Glenn Randers-Pehrson | 01a0e80 | 2015-09-24 22:39:53 -0500 | [diff] [blame] | 2247 | in RGB RGB RGB format unless png_set_filler() or png_set_add_alpha() |
Glenn Randers-Pehrson | 5b77916 | 2004-09-04 13:25:08 -0500 | [diff] [blame] | 2248 | is called to insert filler bytes, either before or after each RGB triplet. |
Glenn Randers-Pehrson | efe4e5d | 2015-09-23 22:08:04 -0500 | [diff] [blame] | 2249 | |
Glenn Randers-Pehrson | 5b77916 | 2004-09-04 13:25:08 -0500 | [diff] [blame] | 2250 | 16-bit RGB data will be returned RRGGBB RRGGBB, with the most significant |
Glenn Randers-Pehrson | fb29e51 | 2011-06-17 20:38:24 -0500 | [diff] [blame] | 2251 | byte of the color value first, unless png_set_scale_16() is called to |
Glenn Randers-Pehrson | 01a0e80 | 2015-09-24 22:39:53 -0500 | [diff] [blame] | 2252 | transform it to regular RGB RGB triplets, or png_set_filler() or |
| 2253 | png_set_add alpha() is called to insert two filler bytes, either before |
| 2254 | or after each RRGGBB triplet. Similarly, 8-bit or 16-bit grayscale data can |
| 2255 | be modified with png_set_filler(), png_set_add_alpha(), png_set_strip_16(), |
| 2256 | or png_set_scale_16(). |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2257 | |
| 2258 | The following code transforms grayscale images of less than 8 to 8 bits, |
| 2259 | changes paletted images to RGB, and adds a full alpha channel if there is |
| 2260 | transparency information in a tRNS chunk. This is most useful on |
| 2261 | grayscale images with bit depths of 2 or 4 or if there is a multiple-image |
| 2262 | viewing application that wishes to treat all images in the same way. |
| 2263 | |
Glenn Randers-Pehrson | 228bd39 | 2000-04-23 23:14:02 -0500 | [diff] [blame] | 2264 | if (color_type == PNG_COLOR_TYPE_PALETTE) |
| 2265 | png_set_palette_to_rgb(png_ptr); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2266 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2267 | if (png_get_valid(png_ptr, info_ptr, |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 2268 | PNG_INFO_tRNS)) png_set_tRNS_to_alpha(png_ptr); |
| 2269 | |
Glenn Randers-Pehrson | c36bb79 | 2011-02-12 09:49:07 -0600 | [diff] [blame] | 2270 | if (color_type == PNG_COLOR_TYPE_GRAY && |
| 2271 | bit_depth < 8) png_set_expand_gray_1_2_4_to_8(png_ptr); |
| 2272 | |
| 2273 | The first two functions are actually aliases for png_set_expand(), added |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 2274 | in libpng version 1.0.4, with the function names expanded to improve code |
| 2275 | readability. In some future version they may actually do different |
| 2276 | things. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2277 | |
Glenn Randers-Pehrson | 1ce0836 | 2006-03-08 23:35:59 -0600 | [diff] [blame] | 2278 | As of libpng version 1.2.9, png_set_expand_gray_1_2_4_to_8() was |
| 2279 | added. It expands the sample depth without changing tRNS to alpha. |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 2280 | |
John Bowler | 63d059a | 2011-02-12 09:03:44 -0600 | [diff] [blame] | 2281 | As of libpng version 1.5.2, png_set_expand_16() was added. It behaves as |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 2282 | png_set_expand(); however, the resultant channels have 16 bits rather than 8. |
Glenn Randers-Pehrson | c36bb79 | 2011-02-12 09:49:07 -0600 | [diff] [blame] | 2283 | Use this when the output color or gray channels are made linear to avoid fairly |
John Bowler | 63d059a | 2011-02-12 09:03:44 -0600 | [diff] [blame] | 2284 | severe accuracy loss. |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 2285 | |
John Bowler | 63d059a | 2011-02-12 09:03:44 -0600 | [diff] [blame] | 2286 | if (bit_depth < 16) |
| 2287 | png_set_expand_16(png_ptr); |
Glenn Randers-Pehrson | 1ce0836 | 2006-03-08 23:35:59 -0600 | [diff] [blame] | 2288 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2289 | PNG can have files with 16 bits per channel. If you only can handle |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 2290 | 8 bits per channel, this will strip the pixels down to 8-bit. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2291 | |
| 2292 | if (bit_depth == 16) |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 2293 | #if PNG_LIBPNG_VER >= 10504 |
Glenn Randers-Pehrson | fb29e51 | 2011-06-17 20:38:24 -0500 | [diff] [blame] | 2294 | png_set_scale_16(png_ptr); |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 2295 | #else |
| 2296 | png_set_strip_16(png_ptr); |
| 2297 | #endif |
| 2298 | |
| 2299 | (The more accurate "png_set_scale_16()" API became available in libpng version |
| 2300 | 1.5.4). |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2301 | |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2302 | If you need to process the alpha channel on the image separately from the image |
| 2303 | data (for example if you convert it to a bitmap mask) it is possible to have |
| 2304 | libpng strip the channel leaving just RGB or gray data: |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2305 | |
| 2306 | if (color_type & PNG_COLOR_MASK_ALPHA) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2307 | png_set_strip_alpha(png_ptr); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2308 | |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2309 | If you strip the alpha channel you need to find some other way of dealing with |
| 2310 | the information. If, instead, you want to convert the image to an opaque |
| 2311 | version with no alpha channel use png_set_background; see below. |
John Bowler | 63d059a | 2011-02-12 09:03:44 -0600 | [diff] [blame] | 2312 | |
| 2313 | As of libpng version 1.5.2, almost all useful expansions are supported, the |
Glenn Randers-Pehrson | cd116fa | 2011-05-17 06:56:50 -0500 | [diff] [blame] | 2314 | major ommissions are conversion of grayscale to indexed images (which can be |
| 2315 | done trivially in the application) and conversion of indexed to grayscale (which |
John Bowler | 63d059a | 2011-02-12 09:03:44 -0600 | [diff] [blame] | 2316 | can be done by a trivial manipulation of the palette.) |
| 2317 | |
| 2318 | In the following table, the 01 means grayscale with depth<8, 31 means |
| 2319 | indexed with depth<8, other numerals represent the color type, "T" means |
| 2320 | the tRNS chunk is present, A means an alpha channel is present, and O |
| 2321 | means tRNS or alpha is present but all pixels in the image are opaque. |
| 2322 | |
Glenn Randers-Pehrson | c36bb79 | 2011-02-12 09:49:07 -0600 | [diff] [blame] | 2323 | FROM 01 31 0 0T 0O 2 2T 2O 3 3T 3O 4A 4O 6A 6O |
John Bowler | 63d059a | 2011-02-12 09:03:44 -0600 | [diff] [blame] | 2324 | TO |
| 2325 | 01 - [G] - - - - - - - - - - - - - |
| 2326 | 31 [Q] Q [Q] [Q] [Q] Q Q Q Q Q Q [Q] [Q] Q Q |
| 2327 | 0 1 G + . . G G G G G G B B GB GB |
| 2328 | 0T lt Gt t + . Gt G G Gt G G Bt Bt GBt GBt |
| 2329 | 0O lt Gt t . + Gt Gt G Gt Gt G Bt Bt GBt GBt |
| 2330 | 2 C P C C C + . . C - - CB CB B B |
| 2331 | 2T Ct - Ct C C t + t - - - CBt CBt Bt Bt |
| 2332 | 2O Ct - Ct C C t t + - - - CBt CBt Bt Bt |
| 2333 | 3 [Q] p [Q] [Q] [Q] Q Q Q + . . [Q] [Q] Q Q |
| 2334 | 3T [Qt] p [Qt][Q] [Q] Qt Qt Qt t + t [Qt][Qt] Qt Qt |
| 2335 | 3O [Qt] p [Qt][Q] [Q] Qt Qt Qt t t + [Qt][Qt] Qt Qt |
| 2336 | 4A lA G A T T GA GT GT GA GT GT + BA G GBA |
| 2337 | 4O lA GBA A T T GA GT GT GA GT GT BA + GBA G |
| 2338 | 6A CA PA CA C C A T tT PA P P C CBA + BA |
| 2339 | 6O CA PBA CA C C A tT T PA P P CBA C BA + |
| 2340 | |
| 2341 | Within the matrix, |
| 2342 | "+" identifies entries where 'from' and 'to' are the same. |
| 2343 | "-" means the transformation is not supported. |
| 2344 | "." means nothing is necessary (a tRNS chunk can just be ignored). |
| 2345 | "t" means the transformation is obtained by png_set_tRNS. |
Glenn Randers-Pehrson | 01a0e80 | 2015-09-24 22:39:53 -0500 | [diff] [blame] | 2346 | "A" means the transformation is obtained by png_set_add_alpha(). |
John Bowler | 63d059a | 2011-02-12 09:03:44 -0600 | [diff] [blame] | 2347 | "X" means the transformation is obtained by png_set_expand(). |
| 2348 | "1" means the transformation is obtained by |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 2349 | png_set_expand_gray_1_2_4_to_8() (and by png_set_expand() |
| 2350 | if there is no transparency in the original or the final |
| 2351 | format). |
John Bowler | 63d059a | 2011-02-12 09:03:44 -0600 | [diff] [blame] | 2352 | "C" means the transformation is obtained by png_set_gray_to_rgb(). |
Glenn Randers-Pehrson | c36074e | 2011-05-16 09:08:51 -0500 | [diff] [blame] | 2353 | "G" means the transformation is obtained by png_set_rgb_to_gray(). |
John Bowler | 63d059a | 2011-02-12 09:03:44 -0600 | [diff] [blame] | 2354 | "P" means the transformation is obtained by |
| 2355 | png_set_expand_palette_to_rgb(). |
| 2356 | "p" means the transformation is obtained by png_set_packing(). |
| 2357 | "Q" means the transformation is obtained by png_set_quantize(). |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 2358 | "T" means the transformation is obtained by |
| 2359 | png_set_tRNS_to_alpha(). |
| 2360 | "B" means the transformation is obtained by |
| 2361 | png_set_background(), or png_strip_alpha(). |
John Bowler | 63d059a | 2011-02-12 09:03:44 -0600 | [diff] [blame] | 2362 | |
| 2363 | When an entry has multiple transforms listed all are required to cause the |
| 2364 | right overall transformation. When two transforms are separated by a comma |
| 2365 | either will do the job. When transforms are enclosed in [] the transform should |
| 2366 | do the job but this is currently unimplemented - a different format will result |
| 2367 | if the suggested transformations are used. |
| 2368 | |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 2369 | In PNG files, the alpha channel in an image |
| 2370 | is the level of opacity. If you need the alpha channel in an image to |
| 2371 | be the level of transparency instead of opacity, you can invert the |
| 2372 | alpha channel (or the tRNS chunk data) after it's read, so that 0 is |
| 2373 | fully opaque and 255 (in 8-bit or paletted images) or 65535 (in 16-bit |
| 2374 | images) is fully transparent, with |
| 2375 | |
| 2376 | png_set_invert_alpha(png_ptr); |
| 2377 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2378 | PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as |
| 2379 | they can, resulting in, for example, 8 pixels per byte for 1 bit |
| 2380 | files. This code expands to 1 pixel per byte without changing the |
| 2381 | values of the pixels: |
| 2382 | |
| 2383 | if (bit_depth < 8) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2384 | png_set_packing(png_ptr); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2385 | |
| 2386 | PNG files have possible bit depths of 1, 2, 4, 8, and 16. All pixels |
| 2387 | stored in a PNG image have been "scaled" or "shifted" up to the next |
Glenn Randers-Pehrson | f210a05 | 2009-11-12 10:02:24 -0600 | [diff] [blame] | 2388 | higher possible bit depth (e.g. from 5 bits/sample in the range [0,31] |
| 2389 | to 8 bits/sample in the range [0, 255]). However, it is also possible |
| 2390 | to convert the PNG pixel data back to the original bit depth of the |
| 2391 | image. This call reduces the pixels back down to the original bit depth: |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2392 | |
Glenn Randers-Pehrson | 1ea0ff3 | 2001-08-07 22:25:59 -0500 | [diff] [blame] | 2393 | png_color_8p sig_bit; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2394 | |
| 2395 | if (png_get_sBIT(png_ptr, info_ptr, &sig_bit)) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2396 | png_set_shift(png_ptr, sig_bit); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2397 | |
| 2398 | PNG files store 3-color pixels in red, green, blue order. This code |
| 2399 | changes the storage of the pixels to blue, green, red: |
| 2400 | |
| 2401 | if (color_type == PNG_COLOR_TYPE_RGB || |
| 2402 | color_type == PNG_COLOR_TYPE_RGB_ALPHA) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2403 | png_set_bgr(png_ptr); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2404 | |
Glenn Randers-Pehrson | 1b8e567 | 2001-08-25 06:46:06 -0500 | [diff] [blame] | 2405 | PNG files store RGB pixels packed into 3 or 6 bytes. This code expands them |
| 2406 | into 4 or 8 bytes for windowing systems that need them in this format: |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2407 | |
Glenn Randers-Pehrson | 1b8e567 | 2001-08-25 06:46:06 -0500 | [diff] [blame] | 2408 | if (color_type == PNG_COLOR_TYPE_RGB) |
Glenn Randers-Pehrson | 01a0e80 | 2015-09-24 22:39:53 -0500 | [diff] [blame] | 2409 | png_set_filler(png_ptr, filler, PNG_FILLER_BEFORE); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2410 | |
Glenn Randers-Pehrson | efe4e5d | 2015-09-23 22:08:04 -0500 | [diff] [blame] | 2411 | where "filler" is the 8-bit or 16-bit number to fill with, and the location |
| 2412 | is either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether |
Glenn Randers-Pehrson | 01a0e80 | 2015-09-24 22:39:53 -0500 | [diff] [blame] | 2413 | you want the filler before the RGB or after. When filling an 8-bit pixel, |
| 2414 | the least significant 8 bits of the number are used, if a 16-bit number is |
| 2415 | supplied. This transformation does not affect images that already have full |
| 2416 | alpha channels. To add an opaque alpha channel, use filler=0xffff and |
| 2417 | PNG_FILLER_AFTER which will generate RGBA pixels. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2418 | |
Glenn Randers-Pehrson | 01a0e80 | 2015-09-24 22:39:53 -0500 | [diff] [blame] | 2419 | Note that png_set_filler() does not change the color type. If you want |
Glenn Randers-Pehrson | 5b77916 | 2004-09-04 13:25:08 -0500 | [diff] [blame] | 2420 | to do that, you can add a true alpha channel with |
| 2421 | |
| 2422 | if (color_type == PNG_COLOR_TYPE_RGB || |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2423 | color_type == PNG_COLOR_TYPE_GRAY) |
Glenn Randers-Pehrson | 01a0e80 | 2015-09-24 22:39:53 -0500 | [diff] [blame] | 2424 | png_set_add_alpha(png_ptr, filler, PNG_FILLER_AFTER); |
Glenn Randers-Pehrson | 5b77916 | 2004-09-04 13:25:08 -0500 | [diff] [blame] | 2425 | |
| 2426 | where "filler" contains the alpha value to assign to each pixel. |
Glenn Randers-Pehrson | 01a0e80 | 2015-09-24 22:39:53 -0500 | [diff] [blame] | 2427 | The png_set_add_alpha() function was added in libpng-1.2.7. |
Glenn Randers-Pehrson | 5b77916 | 2004-09-04 13:25:08 -0500 | [diff] [blame] | 2428 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2429 | If you are reading an image with an alpha channel, and you need the |
| 2430 | data as ARGB instead of the normal PNG format RGBA: |
| 2431 | |
| 2432 | if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2433 | png_set_swap_alpha(png_ptr); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2434 | |
| 2435 | For some uses, you may want a grayscale image to be represented as |
| 2436 | RGB. This code will do that conversion: |
| 2437 | |
| 2438 | if (color_type == PNG_COLOR_TYPE_GRAY || |
| 2439 | color_type == PNG_COLOR_TYPE_GRAY_ALPHA) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2440 | png_set_gray_to_rgb(png_ptr); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2441 | |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 2442 | Conversely, you can convert an RGB or RGBA image to grayscale or grayscale |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 2443 | with alpha. |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 2444 | |
| 2445 | if (color_type == PNG_COLOR_TYPE_RGB || |
| 2446 | color_type == PNG_COLOR_TYPE_RGB_ALPHA) |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 2447 | png_set_rgb_to_gray(png_ptr, error_action, |
| 2448 | double red_weight, double green_weight); |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 2449 | |
| 2450 | error_action = 1: silently do the conversion |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2451 | |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 2452 | error_action = 2: issue a warning if the original |
| 2453 | image has any pixel where |
| 2454 | red != green or red != blue |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2455 | |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 2456 | error_action = 3: issue an error and abort the |
| 2457 | conversion if the original |
| 2458 | image has any pixel where |
| 2459 | red != green or red != blue |
| 2460 | |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2461 | red_weight: weight of red component |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2462 | |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2463 | green_weight: weight of green component |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 2464 | If either weight is negative, default |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2465 | weights are used. |
| 2466 | |
| 2467 | In the corresponding fixed point API the red_weight and green_weight values are |
| 2468 | simply scaled by 100,000: |
| 2469 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 2470 | png_set_rgb_to_gray(png_ptr, error_action, |
| 2471 | png_fixed_point red_weight, |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2472 | png_fixed_point green_weight); |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 2473 | |
| 2474 | If you have set error_action = 1 or 2, you can |
| 2475 | later check whether the image really was gray, after processing |
| 2476 | the image rows, with the png_get_rgb_to_gray_status(png_ptr) function. |
| 2477 | It will return a png_byte that is zero if the image was gray or |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2478 | 1 if there were any non-gray pixels. Background and sBIT data |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 2479 | will be silently converted to grayscale, using the green channel |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2480 | data for sBIT, regardless of the error_action setting. |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 2481 | |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 2482 | The default values come from the PNG file cHRM chunk if present; otherwise, the |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2483 | defaults correspond to the ITU-R recommendation 709, and also the sRGB color |
| 2484 | space, as recommended in the Charles Poynton's Colour FAQ, |
Glenn Randers-Pehrson | a472858 | 2015-08-11 15:34:08 -0500 | [diff] [blame] | 2485 | Copyright (c) 2006-11-28 Charles Poynton, in section 9: |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 2486 | |
Glenn Randers-Pehrson | a472858 | 2015-08-11 15:34:08 -0500 | [diff] [blame] | 2487 | <http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC9> |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 2488 | |
Glenn Randers-Pehrson | 6c98897 | 2011-07-29 12:31:16 -0500 | [diff] [blame] | 2489 | Y = 0.2126 * R + 0.7152 * G + 0.0722 * B |
| 2490 | |
| 2491 | Previous versions of this document, 1998 through 2002, recommended a slightly |
| 2492 | different formula: |
| 2493 | |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 2494 | Y = 0.212671 * R + 0.715160 * G + 0.072169 * B |
| 2495 | |
Glenn Randers-Pehrson | 6c98897 | 2011-07-29 12:31:16 -0500 | [diff] [blame] | 2496 | Libpng uses an integer approximation: |
| 2497 | |
| 2498 | Y = (6968 * R + 23434 * G + 2366 * B)/32768 |
| 2499 | |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 2500 | The calculation is done in a linear colorspace, if the image gamma |
Glenn Randers-Pehrson | 9962b84 | 2011-01-24 00:12:14 -0600 | [diff] [blame] | 2501 | can be determined. |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 2502 | |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 2503 | The png_set_background() function has been described already; it tells libpng to |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2504 | composite images with alpha or simple transparency against the supplied |
| 2505 | background color. For compatibility with versions of libpng earlier than |
Glenn Randers-Pehrson | 733b131 | 2011-06-15 13:21:01 -0500 | [diff] [blame] | 2506 | libpng-1.5.4 it is recommended that you call the function after reading the file |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2507 | header, even if you don't want to use the color in a bKGD chunk, if one exists. |
| 2508 | |
| 2509 | If the PNG file contains a bKGD chunk (PNG_INFO_bKGD valid), |
| 2510 | you may use this color, or supply another color more suitable for |
| 2511 | the current display (e.g., the background color from a web page). You |
| 2512 | need to tell libpng how the color is represented, both the format of the |
Glenn Randers-Pehrson | ab38979 | 2011-07-09 19:35:22 -0500 | [diff] [blame] | 2513 | component values in the color (the number of bits) and the gamma encoding of the |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2514 | color. The function takes two arguments, background_gamma_mode and need_expand |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 2515 | to convey this information; however, only two combinations are likely to be |
Glenn Randers-Pehrson | ab38979 | 2011-07-09 19:35:22 -0500 | [diff] [blame] | 2516 | useful: |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2517 | |
Glenn Randers-Pehrson | cb47e20 | 2011-07-10 06:55:14 -0500 | [diff] [blame] | 2518 | png_color_16 my_background; |
| 2519 | png_color_16p image_background; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2520 | |
Glenn Randers-Pehrson | d0dce40 | 1998-05-09 10:02:29 -0500 | [diff] [blame] | 2521 | if (png_get_bKGD(png_ptr, info_ptr, &image_background)) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2522 | png_set_background(png_ptr, image_background, |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2523 | PNG_BACKGROUND_GAMMA_FILE, 1/*needs to be expanded*/, 1); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2524 | else |
Glenn Randers-Pehrson | cb47e20 | 2011-07-10 06:55:14 -0500 | [diff] [blame] | 2525 | png_set_background(png_ptr, &my_background, |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2526 | PNG_BACKGROUND_GAMMA_SCREEN, 0/*do not expand*/, 1); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2527 | |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2528 | The second call was described above - my_background is in the format of the |
| 2529 | final, display, output produced by libpng. Because you now know the format of |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 2530 | the PNG it is possible to avoid the need to choose either 8-bit or 16-bit |
| 2531 | output and to retain palette images (the palette colors will be modified |
| 2532 | appropriately and the tRNS chunk removed.) However, if you are doing this, |
| 2533 | take great care not to ask for transformations without checking first that |
| 2534 | they apply! |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2535 | |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2536 | In the first call the background color has the original bit depth and color type |
| 2537 | of the PNG file. So, for palette images the color is supplied as a palette |
| 2538 | index and for low bit greyscale images the color is a reduced bit value in |
| 2539 | image_background->gray. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2540 | |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2541 | If you didn't call png_set_gamma() before reading the file header, for example |
| 2542 | if you need your code to remain compatible with older versions of libpng prior |
Glenn Randers-Pehrson | 733b131 | 2011-06-15 13:21:01 -0500 | [diff] [blame] | 2543 | to libpng-1.5.4, this is the place to call it. |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 2544 | |
John Bowler | cb0b296 | 2011-05-12 21:48:29 -0500 | [diff] [blame] | 2545 | Do not call it if you called png_set_alpha_mode(); doing so will damage the |
| 2546 | settings put in place by png_set_alpha_mode(). (If png_set_alpha_mode() is |
| 2547 | supported then you can certainly do png_set_gamma() before reading the PNG |
| 2548 | header.) |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2549 | |
Glenn Randers-Pehrson | c782251 | 2011-05-07 21:23:43 -0500 | [diff] [blame] | 2550 | This API unconditionally sets the screen and file gamma values, so it will |
| 2551 | override the value in the PNG file unless it is called before the PNG file |
| 2552 | reading starts. For this reason you must always call it with the PNG file |
| 2553 | value when you call it in this position: |
| 2554 | |
Glenn Randers-Pehrson | 8d0bc0f | 2011-01-25 22:15:58 -0600 | [diff] [blame] | 2555 | if (png_get_gAMA(png_ptr, info_ptr, &file_gamma)) |
| 2556 | png_set_gamma(png_ptr, screen_gamma, file_gamma); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2557 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2558 | else |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 2559 | png_set_gamma(png_ptr, screen_gamma, 0.45455); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2560 | |
Glenn Randers-Pehrson | 3cd7cff | 2010-04-16 19:27:08 -0500 | [diff] [blame] | 2561 | If you need to reduce an RGB file to a paletted file, or if a paletted |
Glenn Randers-Pehrson | 3645008 | 2015-03-09 09:13:58 -0500 | [diff] [blame] | 2562 | file has more entries than will fit on your screen, png_set_quantize() |
Glenn Randers-Pehrson | 862cb20 | 2010-04-16 22:12:51 -0500 | [diff] [blame] | 2563 | will do that. Note that this is a simple match quantization that merely |
Glenn Randers-Pehrson | 3cd7cff | 2010-04-16 19:27:08 -0500 | [diff] [blame] | 2564 | finds the closest color available. This should work fairly well with |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2565 | optimized palettes, but fairly badly with linear color cubes. If you |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 2566 | pass a palette that is larger than maximum_colors, the file will |
Glenn Randers-Pehrson | 3cd7cff | 2010-04-16 19:27:08 -0500 | [diff] [blame] | 2567 | reduce the number of colors in the palette so it will fit into |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 2568 | maximum_colors. If there is a histogram, libpng will use it to make |
Glenn Randers-Pehrson | 3cd7cff | 2010-04-16 19:27:08 -0500 | [diff] [blame] | 2569 | more intelligent choices when reducing the palette. If there is no |
| 2570 | histogram, it may not do as good a job. |
| 2571 | |
| 2572 | if (color_type & PNG_COLOR_MASK_COLOR) |
| 2573 | { |
| 2574 | if (png_get_valid(png_ptr, info_ptr, |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2575 | PNG_INFO_PLTE)) |
Glenn Randers-Pehrson | 3cd7cff | 2010-04-16 19:27:08 -0500 | [diff] [blame] | 2576 | { |
| 2577 | png_uint_16p histogram = NULL; |
| 2578 | |
| 2579 | png_get_hIST(png_ptr, info_ptr, |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2580 | &histogram); |
Glenn Randers-Pehrson | 3cd7cff | 2010-04-16 19:27:08 -0500 | [diff] [blame] | 2581 | png_set_quantize(png_ptr, palette, num_palette, |
| 2582 | max_screen_colors, histogram, 1); |
| 2583 | } |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2584 | |
Glenn Randers-Pehrson | 3cd7cff | 2010-04-16 19:27:08 -0500 | [diff] [blame] | 2585 | else |
| 2586 | { |
| 2587 | png_color std_color_cube[MAX_SCREEN_COLORS] = |
| 2588 | { ... colors ... }; |
| 2589 | |
| 2590 | png_set_quantize(png_ptr, std_color_cube, |
| 2591 | MAX_SCREEN_COLORS, MAX_SCREEN_COLORS, |
| 2592 | NULL,0); |
| 2593 | } |
| 2594 | } |
| 2595 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2596 | PNG files describe monochrome as black being zero and white being one. |
| 2597 | The following code will reverse this (make black be one and white be |
| 2598 | zero): |
| 2599 | |
Glenn Randers-Pehrson | 1ea0ff3 | 2001-08-07 22:25:59 -0500 | [diff] [blame] | 2600 | if (bit_depth == 1 && color_type == PNG_COLOR_TYPE_GRAY) |
| 2601 | png_set_invert_mono(png_ptr); |
| 2602 | |
| 2603 | This function can also be used to invert grayscale and gray-alpha images: |
| 2604 | |
| 2605 | if (color_type == PNG_COLOR_TYPE_GRAY || |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2606 | color_type == PNG_COLOR_TYPE_GRAY_ALPHA) |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2607 | png_set_invert_mono(png_ptr); |
| 2608 | |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 2609 | PNG files store 16-bit pixels in network byte order (big-endian, |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 2610 | ie. most significant bits first). This code changes the storage to the |
| 2611 | other way (little-endian, i.e. least significant bits first, the |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2612 | way PCs store them): |
| 2613 | |
| 2614 | if (bit_depth == 16) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2615 | png_set_swap(png_ptr); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2616 | |
| 2617 | If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you |
| 2618 | need to change the order the pixels are packed into bytes, you can use: |
| 2619 | |
| 2620 | if (bit_depth < 8) |
| 2621 | png_set_packswap(png_ptr); |
| 2622 | |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 2623 | Finally, you can write your own transformation function if none of |
| 2624 | the existing ones meets your needs. This is done by setting a callback |
| 2625 | with |
| 2626 | |
| 2627 | png_set_read_user_transform_fn(png_ptr, |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2628 | read_transform_fn); |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 2629 | |
| 2630 | You must supply the function |
| 2631 | |
Glenn Randers-Pehrson | 9321567 | 2011-02-13 19:42:19 -0600 | [diff] [blame] | 2632 | void read_transform_fn(png_structp png_ptr, png_row_infop |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2633 | row_info, png_bytep data) |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 2634 | |
| 2635 | See pngtest.c for a working example. Your function will be called |
John Bowler | f19abd6 | 2011-01-22 18:29:24 -0600 | [diff] [blame] | 2636 | after all of the other transformations have been processed. Take care with |
| 2637 | interlaced images if you do the interlace yourself - the width of the row is the |
| 2638 | width in 'row_info', not the overall image width. |
| 2639 | |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 2640 | If supported, libpng provides two information routines that you can use to find |
John Bowler | f19abd6 | 2011-01-22 18:29:24 -0600 | [diff] [blame] | 2641 | where you are in processing the image: |
| 2642 | |
| 2643 | png_get_current_pass_number(png_structp png_ptr); |
| 2644 | png_get_current_row_number(png_structp png_ptr); |
| 2645 | |
| 2646 | Don't try using these outside a transform callback - firstly they are only |
| 2647 | supported if user transforms are supported, secondly they may well return |
| 2648 | unexpected results unless the row is actually being processed at the moment they |
| 2649 | are called. |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 2650 | |
John Bowler | cd11345 | 2011-02-16 06:15:13 -0600 | [diff] [blame] | 2651 | With interlaced |
| 2652 | images the value returned is the row in the input sub-image image. Use |
| 2653 | PNG_ROW_FROM_PASS_ROW(row, pass) and PNG_COL_FROM_PASS_COL(col, pass) to |
| 2654 | find the output pixel (x,y) given an interlaced sub-image pixel (row,col,pass). |
| 2655 | |
| 2656 | The discussion of interlace handling above contains more information on how to |
| 2657 | use these values. |
| 2658 | |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 2659 | You can also set up a pointer to a user structure for use by your |
| 2660 | callback function, and you can inform libpng that your transform |
| 2661 | function will change the number of channels or bit depth with the |
| 2662 | function |
| 2663 | |
| 2664 | png_set_user_transform_info(png_ptr, user_ptr, |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2665 | user_depth, user_channels); |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 2666 | |
| 2667 | The user's application, not libpng, is responsible for allocating and |
| 2668 | freeing any memory required for the user structure. |
| 2669 | |
| 2670 | You can retrieve the pointer via the function |
| 2671 | png_get_user_transform_ptr(). For example: |
| 2672 | |
| 2673 | voidp read_user_transform_ptr = |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2674 | png_get_user_transform_ptr(png_ptr); |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 2675 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2676 | The last thing to handle is interlacing; this is covered in detail below, |
| 2677 | but you must call the function here if you want libpng to handle expansion |
| 2678 | of the interlaced image. |
| 2679 | |
| 2680 | number_of_passes = png_set_interlace_handling(png_ptr); |
| 2681 | |
| 2682 | After setting the transformations, libpng can update your png_info |
| 2683 | structure to reflect any transformations you've requested with this |
Glenn Randers-Pehrson | 968c231 | 2011-09-26 16:35:22 -0500 | [diff] [blame] | 2684 | call. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2685 | |
| 2686 | png_read_update_info(png_ptr, info_ptr); |
| 2687 | |
Glenn Randers-Pehrson | 968c231 | 2011-09-26 16:35:22 -0500 | [diff] [blame] | 2688 | This is most useful to update the info structure's rowbytes |
| 2689 | field so you can use it to allocate your image memory. This function |
| 2690 | will also update your palette with the correct screen_gamma and |
| 2691 | background if these have been given with the calls above. You may |
| 2692 | only call png_read_update_info() once with a particular info_ptr. |
| 2693 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2694 | After you call png_read_update_info(), you can allocate any |
| 2695 | memory you need to hold the image. The row data is simply |
| 2696 | raw byte data for all forms of images. As the actual allocation |
| 2697 | varies among applications, no example will be given. If you |
| 2698 | are allocating one large chunk, you will need to build an |
| 2699 | array of pointers to each row, as it will be needed for some |
| 2700 | of the functions below. |
| 2701 | |
Glenn Randers-Pehrson | 53f22ae | 2017-04-22 15:21:58 -0500 | [diff] [blame] | 2702 | Be sure that your platform can allocate the buffer that you'll need. |
| 2703 | libpng internally checks for oversize width, but you'll need to |
| 2704 | do your own check for number_of_rows*width*pixel_size if you are using |
| 2705 | a multiple-row buffer: |
| 2706 | |
| 2707 | /* Guard against integer overflow */ |
| 2708 | if (number_of_rows > PNG_SIZE_MAX/(width*pixel_size)) { |
| 2709 | png_error(png_ptr,"image_data buffer would be too large"); |
| 2710 | } |
| 2711 | |
Glenn Randers-Pehrson | 968c231 | 2011-09-26 16:35:22 -0500 | [diff] [blame] | 2712 | Remember: Before you call png_read_update_info(), the png_get_*() |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 2713 | functions return the values corresponding to the original PNG image. |
| 2714 | After you call png_read_update_info the values refer to the image |
| 2715 | that libpng will output. Consequently you must call all the png_set_ |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2716 | functions before you call png_read_update_info(). This is particularly |
| 2717 | important for png_set_interlace_handling() - if you are going to call |
| 2718 | png_read_update_info() you must call png_set_interlace_handling() before |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 2719 | it unless you want to receive interlaced output. |
| 2720 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 2721 | .SS Reading image data |
| 2722 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2723 | After you've allocated memory, you can read the image data. |
| 2724 | The simplest way to do this is in one function call. If you are |
| 2725 | allocating enough memory to hold the whole image, you can just |
| 2726 | call png_read_image() and libpng will read in all the image data |
| 2727 | and put it in the memory area supplied. You will need to pass in |
| 2728 | an array of pointers to each row. |
| 2729 | |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 2730 | This function automatically handles interlacing, so you don't |
| 2731 | need to call png_set_interlace_handling() (unless you call |
| 2732 | png_read_update_info()) or call this function multiple times, or any |
| 2733 | of that other stuff necessary with png_read_rows(). |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2734 | |
| 2735 | png_read_image(png_ptr, row_pointers); |
| 2736 | |
| 2737 | where row_pointers is: |
| 2738 | |
| 2739 | png_bytep row_pointers[height]; |
| 2740 | |
| 2741 | You can point to void or char or whatever you use for pixels. |
| 2742 | |
| 2743 | If you don't want to read in the whole image at once, you can |
| 2744 | use png_read_rows() instead. If there is no interlacing (check |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 2745 | interlace_type == PNG_INTERLACE_NONE), this is simple: |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2746 | |
| 2747 | png_read_rows(png_ptr, row_pointers, NULL, |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2748 | number_of_rows); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2749 | |
| 2750 | where row_pointers is the same as in the png_read_image() call. |
| 2751 | |
| 2752 | If you are doing this just one row at a time, you can do this with |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 2753 | a single row_pointer instead of an array of row_pointers: |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2754 | |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 2755 | png_bytep row_pointer = row; |
Glenn Randers-Pehrson | 228bd39 | 2000-04-23 23:14:02 -0500 | [diff] [blame] | 2756 | png_read_row(png_ptr, row_pointer, NULL); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2757 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 2758 | If the file is interlaced (interlace_type != 0 in the IHDR chunk), things |
| 2759 | get somewhat harder. The only current (PNG Specification version 1.2) |
Glenn Randers-Pehrson | 6e97410 | 2010-12-19 16:44:22 -0600 | [diff] [blame] | 2760 | interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7); |
| 2761 | a somewhat complicated 2D interlace scheme, known as Adam7, that |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2762 | breaks down an image into seven smaller images of varying size, based |
Glenn Randers-Pehrson | 6e97410 | 2010-12-19 16:44:22 -0600 | [diff] [blame] | 2763 | on an 8x8 grid. This number is defined (from libpng 1.5) as |
| 2764 | PNG_INTERLACE_ADAM7_PASSES in png.h |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2765 | |
| 2766 | libpng can fill out those images or it can give them to you "as is". |
Glenn Randers-Pehrson | 6e97410 | 2010-12-19 16:44:22 -0600 | [diff] [blame] | 2767 | It is almost always better to have libpng handle the interlacing for you. |
| 2768 | If you want the images filled out, there are two ways to do that. The one |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2769 | mentioned in the PNG specification is to expand each pixel to cover |
| 2770 | those pixels that have not been read yet (the "rectangle" method). |
| 2771 | This results in a blocky image for the first pass, which gradually |
| 2772 | smooths out as more pixels are read. The other method is the "sparkle" |
| 2773 | method, where pixels are drawn only in their final locations, with the |
| 2774 | rest of the image remaining whatever colors they were initialized to |
| 2775 | before the start of the read. The first method usually looks better, |
| 2776 | but tends to be slower, as there are more pixels to put in the rows. |
| 2777 | |
Glenn Randers-Pehrson | 6e97410 | 2010-12-19 16:44:22 -0600 | [diff] [blame] | 2778 | If, as is likely, you want libpng to expand the images, call this before |
| 2779 | calling png_start_read_image() or png_read_update_info(): |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2780 | |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 2781 | if (interlace_type == PNG_INTERLACE_ADAM7) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2782 | number_of_passes |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2783 | = png_set_interlace_handling(png_ptr); |
| 2784 | |
Glenn Randers-Pehrson | 6e97410 | 2010-12-19 16:44:22 -0600 | [diff] [blame] | 2785 | This will return the number of passes needed. Currently, this is seven, |
| 2786 | but may change if another interlace type is added. This function can be |
| 2787 | called even if the file is not interlaced, where it will return one pass. |
| 2788 | You then need to read the whole image 'number_of_passes' times. Each time |
| 2789 | will distribute the pixels from the current pass to the correct place in |
| 2790 | the output image, so you need to supply the same rows to png_read_rows in |
| 2791 | each pass. |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 2792 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2793 | If you are not going to display the image after each pass, but are |
| 2794 | going to wait until the entire image is read in, use the sparkle |
| 2795 | effect. This effect is faster and the end result of either method |
| 2796 | is exactly the same. If you are planning on displaying the image |
| 2797 | after each pass, the "rectangle" effect is generally considered the |
| 2798 | better looking one. |
| 2799 | |
Glenn Randers-Pehrson | 66f796e | 2016-07-04 08:31:04 -0500 | [diff] [blame] | 2800 | If you only want the "sparkle" effect, just call png_read_row() or |
| 2801 | png_read_rows() as |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2802 | normal, with the third parameter NULL. Make sure you make pass over |
| 2803 | the image number_of_passes times, and you don't change the data in the |
| 2804 | rows between calls. You can change the locations of the data, just |
| 2805 | not the data. Each pass only writes the pixels appropriate for that |
| 2806 | pass, and assumes the data from previous passes is still valid. |
| 2807 | |
| 2808 | png_read_rows(png_ptr, row_pointers, NULL, |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2809 | number_of_rows); |
Glenn Randers-Pehrson | 66f796e | 2016-07-04 08:31:04 -0500 | [diff] [blame] | 2810 | or |
| 2811 | png_read_row(png_ptr, row_pointers, NULL); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2812 | |
| 2813 | If you only want the first effect (the rectangles), do the same as |
| 2814 | before except pass the row buffer in the third parameter, and leave |
| 2815 | the second parameter NULL. |
| 2816 | |
| 2817 | png_read_rows(png_ptr, NULL, row_pointers, |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2818 | number_of_rows); |
Glenn Randers-Pehrson | 66f796e | 2016-07-04 08:31:04 -0500 | [diff] [blame] | 2819 | or |
| 2820 | png_read_row(png_ptr, NULL, row_pointers); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2821 | |
Glenn Randers-Pehrson | 6e97410 | 2010-12-19 16:44:22 -0600 | [diff] [blame] | 2822 | If you don't want libpng to handle the interlacing details, just call |
| 2823 | png_read_rows() PNG_INTERLACE_ADAM7_PASSES times to read in all the images. |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 2824 | Each of the images is a valid image by itself; however, you will almost |
Glenn Randers-Pehrson | 6e97410 | 2010-12-19 16:44:22 -0600 | [diff] [blame] | 2825 | certainly need to distribute the pixels from each sub-image to the |
| 2826 | correct place. This is where everything gets very tricky. |
| 2827 | |
| 2828 | If you want to retrieve the separate images you must pass the correct |
| 2829 | number of rows to each successive call of png_read_rows(). The calculation |
| 2830 | gets pretty complicated for small images, where some sub-images may |
| 2831 | not even exist because either their width or height ends up zero. |
| 2832 | libpng provides two macros to help you in 1.5 and later versions: |
| 2833 | |
| 2834 | png_uint_32 width = PNG_PASS_COLS(image_width, pass_number); |
| 2835 | png_uint_32 height = PNG_PASS_ROWS(image_height, pass_number); |
| 2836 | |
| 2837 | Respectively these tell you the width and height of the sub-image |
| 2838 | corresponding to the numbered pass. 'pass' is in in the range 0 to 6 - |
| 2839 | this can be confusing because the specification refers to the same passes |
| 2840 | as 1 to 7! Be careful, you must check both the width and height before |
| 2841 | calling png_read_rows() and not call it for that pass if either is zero. |
| 2842 | |
| 2843 | You can, of course, read each sub-image row by row. If you want to |
| 2844 | produce optimal code to make a pixel-by-pixel transformation of an |
| 2845 | interlaced image this is the best approach; read each row of each pass, |
| 2846 | transform it, and write it out to a new interlaced image. |
| 2847 | |
| 2848 | If you want to de-interlace the image yourself libpng provides further |
| 2849 | macros to help that tell you where to place the pixels in the output image. |
| 2850 | Because the interlacing scheme is rectangular - sub-image pixels are always |
| 2851 | arranged on a rectangular grid - all you need to know for each pass is the |
| 2852 | starting column and row in the output image of the first pixel plus the |
| 2853 | spacing between each pixel. As of libpng 1.5 there are four macros to |
| 2854 | retrieve this information: |
| 2855 | |
| 2856 | png_uint_32 x = PNG_PASS_START_COL(pass); |
| 2857 | png_uint_32 y = PNG_PASS_START_ROW(pass); |
| 2858 | png_uint_32 xStep = 1U << PNG_PASS_COL_SHIFT(pass); |
| 2859 | png_uint_32 yStep = 1U << PNG_PASS_ROW_SHIFT(pass); |
| 2860 | |
| 2861 | These allow you to write the obvious loop: |
| 2862 | |
| 2863 | png_uint_32 input_y = 0; |
| 2864 | png_uint_32 output_y = PNG_PASS_START_ROW(pass); |
| 2865 | |
| 2866 | while (output_y < output_image_height) |
| 2867 | { |
| 2868 | png_uint_32 input_x = 0; |
| 2869 | png_uint_32 output_x = PNG_PASS_START_COL(pass); |
| 2870 | |
| 2871 | while (output_x < output_image_width) |
| 2872 | { |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2873 | image[output_y][output_x] = |
| 2874 | subimage[pass][input_y][input_x++]; |
| 2875 | |
Glenn Randers-Pehrson | 6e97410 | 2010-12-19 16:44:22 -0600 | [diff] [blame] | 2876 | output_x += xStep; |
| 2877 | } |
| 2878 | |
| 2879 | ++input_y; |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2880 | output_y += yStep; |
Glenn Randers-Pehrson | 6e97410 | 2010-12-19 16:44:22 -0600 | [diff] [blame] | 2881 | } |
| 2882 | |
| 2883 | Notice that the steps between successive output rows and columns are |
| 2884 | returned as shifts. This is possible because the pixels in the subimages |
| 2885 | are always a power of 2 apart - 1, 2, 4 or 8 pixels - in the original |
| 2886 | image. In practice you may need to directly calculate the output coordinate |
| 2887 | given an input coordinate. libpng provides two further macros for this |
| 2888 | purpose: |
| 2889 | |
| 2890 | png_uint_32 output_x = PNG_COL_FROM_PASS_COL(input_x, pass); |
| 2891 | png_uint_32 output_y = PNG_ROW_FROM_PASS_ROW(input_y, pass); |
| 2892 | |
| 2893 | Finally a pair of macros are provided to tell you if a particular image |
| 2894 | row or column appears in a given pass: |
| 2895 | |
| 2896 | int col_in_pass = PNG_COL_IN_INTERLACE_PASS(output_x, pass); |
| 2897 | int row_in_pass = PNG_ROW_IN_INTERLACE_PASS(output_y, pass); |
| 2898 | |
| 2899 | Bear in mind that you will probably also need to check the width and height |
| 2900 | of the pass in addition to the above to be sure the pass even exists! |
| 2901 | |
| 2902 | With any luck you are convinced by now that you don't want to do your own |
| 2903 | interlace handling. In reality normally the only good reason for doing this |
| 2904 | is if you are processing PNG files on a pixel-by-pixel basis and don't want |
| 2905 | to load the whole file into memory when it is interlaced. |
| 2906 | |
| 2907 | libpng includes a test program, pngvalid, that illustrates reading and |
| 2908 | writing of interlaced images. If you can't get interlacing to work in your |
Glenn Randers-Pehrson | 95ba417 | 2011-09-08 12:21:42 -0500 | [diff] [blame] | 2909 | code and don't want to leave it to libpng (the recommended approach), see |
Glenn Randers-Pehrson | 6e97410 | 2010-12-19 16:44:22 -0600 | [diff] [blame] | 2910 | how pngvalid.c does it. |
| 2911 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 2912 | .SS Finishing a sequential read |
| 2913 | |
Glenn Randers-Pehrson | 9c3ab68 | 2006-02-20 22:09:05 -0600 | [diff] [blame] | 2914 | After you are finished reading the image through the |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 2915 | low-level interface, you can finish reading the file. |
| 2916 | |
| 2917 | If you want to use a different crc action for handling CRC errors in |
| 2918 | chunks after the image data, you can call png_set_crc_action() |
| 2919 | again at this point. |
| 2920 | |
| 2921 | If you are interested in comments or time, which may be stored either |
| 2922 | before or after the image data, you should pass the separate png_info |
| 2923 | struct if you want to keep the comments from before and after the image |
Glenn Randers-Pehrson | 20786be | 2011-04-20 22:20:40 -0500 | [diff] [blame] | 2924 | separate. |
| 2925 | |
| 2926 | png_infop end_info = png_create_info_struct(png_ptr); |
| 2927 | |
| 2928 | if (!end_info) |
| 2929 | { |
| 2930 | png_destroy_read_struct(&png_ptr, &info_ptr, |
| 2931 | (png_infopp)NULL); |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 2932 | return ERROR; |
Glenn Randers-Pehrson | 20786be | 2011-04-20 22:20:40 -0500 | [diff] [blame] | 2933 | } |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2934 | |
| 2935 | png_read_end(png_ptr, end_info); |
| 2936 | |
Glenn Randers-Pehrson | 20786be | 2011-04-20 22:20:40 -0500 | [diff] [blame] | 2937 | If you are not interested, you should still call png_read_end() |
| 2938 | but you can pass NULL, avoiding the need to create an end_info structure. |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 2939 | If you do this, libpng will not process any chunks after IDAT other than |
| 2940 | skipping over them and perhaps (depending on whether you have called |
| 2941 | png_set_crc_action) checking their CRCs while looking for the IEND chunk. |
Glenn Randers-Pehrson | 20786be | 2011-04-20 22:20:40 -0500 | [diff] [blame] | 2942 | |
| 2943 | png_read_end(png_ptr, (png_infop)NULL); |
| 2944 | |
Glenn Randers-Pehrson | 99778e1 | 2011-04-20 17:43:52 -0500 | [diff] [blame] | 2945 | If you don't call png_read_end(), then your file pointer will be |
| 2946 | left pointing to the first chunk after the last IDAT, which is probably |
| 2947 | not what you want if you expect to read something beyond the end of |
| 2948 | the PNG datastream. |
| 2949 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 2950 | When you are done, you can free all memory allocated by libpng like this: |
| 2951 | |
| 2952 | png_destroy_read_struct(&png_ptr, &info_ptr, |
| 2953 | &end_info); |
| 2954 | |
Glenn Randers-Pehrson | 20786be | 2011-04-20 22:20:40 -0500 | [diff] [blame] | 2955 | or, if you didn't create an end_info structure, |
| 2956 | |
| 2957 | png_destroy_read_struct(&png_ptr, &info_ptr, |
| 2958 | (png_infopp)NULL); |
| 2959 | |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 2960 | It is also possible to individually free the info_ptr members that |
Glenn Randers-Pehrson | fc4a143 | 2000-05-17 17:39:34 -0500 | [diff] [blame] | 2961 | point to libpng-allocated storage with the following function: |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 2962 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2963 | png_free_data(png_ptr, info_ptr, mask, seq) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2964 | |
Glenn Randers-Pehrson | 1ef65b6 | 2000-05-12 06:19:53 -0500 | [diff] [blame] | 2965 | mask - identifies data to be freed, a mask |
Glenn Randers-Pehrson | ebd7f9a | 2006-10-19 09:37:56 -0500 | [diff] [blame] | 2966 | containing the bitwise OR of one or |
Glenn Randers-Pehrson | 1ef65b6 | 2000-05-12 06:19:53 -0500 | [diff] [blame] | 2967 | more of |
| 2968 | PNG_FREE_PLTE, PNG_FREE_TRNS, |
| 2969 | PNG_FREE_HIST, PNG_FREE_ICCP, |
| 2970 | PNG_FREE_PCAL, PNG_FREE_ROWS, |
| 2971 | PNG_FREE_SCAL, PNG_FREE_SPLT, |
| 2972 | PNG_FREE_TEXT, PNG_FREE_UNKN, |
| 2973 | or simply PNG_FREE_ALL |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2974 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 2975 | seq - sequence number of item to be freed |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 2976 | (\-1 for all items) |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 2977 | |
Glenn Randers-Pehrson | fc4a143 | 2000-05-17 17:39:34 -0500 | [diff] [blame] | 2978 | This function may be safely called when the relevant storage has |
Glenn Randers-Pehrson | 68ea243 | 2000-04-01 21:10:05 -0600 | [diff] [blame] | 2979 | already been freed, or has not yet been allocated, or was allocated |
Glenn Randers-Pehrson | f210a05 | 2009-11-12 10:02:24 -0600 | [diff] [blame] | 2980 | by the user and not by libpng, and will in those cases do nothing. |
| 2981 | The "seq" parameter is ignored if only one item of the selected data |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 2982 | type, such as PLTE, is allowed. If "seq" is not \-1, and multiple items |
Glenn Randers-Pehrson | f210a05 | 2009-11-12 10:02:24 -0600 | [diff] [blame] | 2983 | are allowed for the data type identified in the mask, such as text or |
| 2984 | sPLT, only the n'th item in the structure is freed, where n is "seq". |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 2985 | |
Glenn Randers-Pehrson | 38e6e77 | 2000-04-09 19:06:13 -0500 | [diff] [blame] | 2986 | The default behavior is only to free data that was allocated internally |
| 2987 | by libpng. This can be changed, so that libpng will not free the data, |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 2988 | or so that it will free data that was allocated by the user with png_malloc() |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 2989 | or png_calloc() and passed in via a png_set_*() function, with |
Glenn Randers-Pehrson | 38e6e77 | 2000-04-09 19:06:13 -0500 | [diff] [blame] | 2990 | |
| 2991 | png_data_freer(png_ptr, info_ptr, freer, mask) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2992 | |
Glenn Randers-Pehrson | 1ef65b6 | 2000-05-12 06:19:53 -0500 | [diff] [blame] | 2993 | freer - one of |
| 2994 | PNG_DESTROY_WILL_FREE_DATA |
| 2995 | PNG_SET_WILL_FREE_DATA |
| 2996 | PNG_USER_WILL_FREE_DATA |
Glenn Randers-Pehrson | 38e6e77 | 2000-04-09 19:06:13 -0500 | [diff] [blame] | 2997 | |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 2998 | mask - which data elements are affected |
| 2999 | same choices as in png_free_data() |
| 3000 | |
Glenn Randers-Pehrson | 38e6e77 | 2000-04-09 19:06:13 -0500 | [diff] [blame] | 3001 | This function only affects data that has already been allocated. |
| 3002 | You can call this function after reading the PNG data but before calling |
| 3003 | any png_set_*() functions, to control whether the user or the png_set_*() |
| 3004 | function is responsible for freeing any existing data that might be present, |
| 3005 | and again after the png_set_*() functions to control whether the user |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 3006 | or png_destroy_*() is supposed to free the data. When the user assumes |
| 3007 | responsibility for libpng-allocated data, the application must use |
Glenn Randers-Pehrson | 1ef65b6 | 2000-05-12 06:19:53 -0500 | [diff] [blame] | 3008 | png_free() to free it, and when the user transfers responsibility to libpng |
| 3009 | for data that the user has allocated, the user must have used png_malloc() |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 3010 | or png_calloc() to allocate it. |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 3011 | |
| 3012 | If you allocated your row_pointers in a single block, as suggested above in |
| 3013 | the description of the high level read interface, you must not transfer |
| 3014 | responsibility for freeing it to the png_set_rows or png_read_destroy function, |
| 3015 | because they would also try to free the individual row_pointers[i]. |
Glenn Randers-Pehrson | 38e6e77 | 2000-04-09 19:06:13 -0500 | [diff] [blame] | 3016 | |
Glenn Randers-Pehrson | 1ef65b6 | 2000-05-12 06:19:53 -0500 | [diff] [blame] | 3017 | If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword |
| 3018 | separately, do not transfer responsibility for freeing text_ptr to libpng, |
| 3019 | because when libpng fills a png_text structure it combines these members with |
| 3020 | the key member, and png_free_data() will free only text_ptr.key. Similarly, |
| 3021 | if you transfer responsibility for free'ing text_ptr from libpng to your |
| 3022 | application, your application must not separately free those members. |
| 3023 | |
Glenn Randers-Pehrson | fc4a143 | 2000-05-17 17:39:34 -0500 | [diff] [blame] | 3024 | The png_free_data() function will turn off the "valid" flag for anything |
Glenn Randers-Pehrson | f210a05 | 2009-11-12 10:02:24 -0600 | [diff] [blame] | 3025 | it frees. If you need to turn the flag off for a chunk that was freed by |
| 3026 | your application instead of by libpng, you can use |
Glenn Randers-Pehrson | fc4a143 | 2000-05-17 17:39:34 -0500 | [diff] [blame] | 3027 | |
| 3028 | png_set_invalid(png_ptr, info_ptr, mask); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3029 | |
Glenn Randers-Pehrson | fc4a143 | 2000-05-17 17:39:34 -0500 | [diff] [blame] | 3030 | mask - identifies the chunks to be made invalid, |
Glenn Randers-Pehrson | ebd7f9a | 2006-10-19 09:37:56 -0500 | [diff] [blame] | 3031 | containing the bitwise OR of one or |
Glenn Randers-Pehrson | d56aca7 | 2000-11-23 11:51:42 -0600 | [diff] [blame] | 3032 | more of |
Glenn Randers-Pehrson | fc4a143 | 2000-05-17 17:39:34 -0500 | [diff] [blame] | 3033 | PNG_INFO_gAMA, PNG_INFO_sBIT, |
| 3034 | PNG_INFO_cHRM, PNG_INFO_PLTE, |
| 3035 | PNG_INFO_tRNS, PNG_INFO_bKGD, |
Glenn Randers-Pehrson | 68cb0aa | 2017-07-13 11:19:53 -0500 | [diff] [blame] | 3036 | PNG_INFO_eXIf, |
Glenn Randers-Pehrson | fc4a143 | 2000-05-17 17:39:34 -0500 | [diff] [blame] | 3037 | PNG_INFO_hIST, PNG_INFO_pHYs, |
| 3038 | PNG_INFO_oFFs, PNG_INFO_tIME, |
| 3039 | PNG_INFO_pCAL, PNG_INFO_sRGB, |
| 3040 | PNG_INFO_iCCP, PNG_INFO_sPLT, |
| 3041 | PNG_INFO_sCAL, PNG_INFO_IDAT |
| 3042 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3043 | For a more compact example of reading a PNG image, see the file example.c. |
| 3044 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3045 | .SS Reading PNG files progressively |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3046 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 3047 | The progressive reader is slightly different from the non-progressive |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3048 | reader. Instead of calling png_read_info(), png_read_rows(), and |
| 3049 | png_read_end(), you make one call to png_process_data(), which calls |
| 3050 | callbacks when it has the info, a row, or the end of the image. You |
| 3051 | set up these callbacks with png_set_progressive_read_fn(). You don't |
| 3052 | have to worry about the input/output functions of libpng, as you are |
| 3053 | giving the library the data directly in png_process_data(). I will |
| 3054 | assume that you have read the section on reading PNG files above, |
| 3055 | so I will only highlight the differences (although I will show |
| 3056 | all of the code). |
| 3057 | |
| 3058 | png_structp png_ptr; |
| 3059 | png_infop info_ptr; |
| 3060 | |
| 3061 | /* An example code fragment of how you would |
| 3062 | initialize the progressive reader in your |
| 3063 | application. */ |
| 3064 | int |
| 3065 | initialize_png_reader() |
| 3066 | { |
| 3067 | png_ptr = png_create_read_struct |
Glenn Randers-Pehrson | 61ea3ea | 2014-11-06 06:39:56 -0600 | [diff] [blame] | 3068 | (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3069 | user_error_fn, user_warning_fn); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3070 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3071 | if (!png_ptr) |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 3072 | return ERROR; |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3073 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3074 | info_ptr = png_create_info_struct(png_ptr); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3075 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3076 | if (!info_ptr) |
| 3077 | { |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3078 | png_destroy_read_struct(&png_ptr, |
| 3079 | (png_infopp)NULL, (png_infopp)NULL); |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 3080 | return ERROR; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3081 | } |
| 3082 | |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 3083 | if (setjmp(png_jmpbuf(png_ptr))) |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3084 | { |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3085 | png_destroy_read_struct(&png_ptr, &info_ptr, |
| 3086 | (png_infopp)NULL); |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 3087 | return ERROR; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3088 | } |
| 3089 | |
| 3090 | /* This one's new. You can provide functions |
| 3091 | to be called when the header info is valid, |
| 3092 | when each row is completed, and when the image |
| 3093 | is finished. If you aren't using all functions, |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 3094 | you can specify NULL parameters. Even when all |
| 3095 | three functions are NULL, you need to call |
| 3096 | png_set_progressive_read_fn(). You can use |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3097 | any struct as the user_ptr (cast to a void pointer |
| 3098 | for the function call), and retrieve the pointer |
| 3099 | from inside the callbacks using the function |
| 3100 | |
| 3101 | png_get_progressive_ptr(png_ptr); |
| 3102 | |
| 3103 | which will return a void pointer, which you have |
| 3104 | to cast appropriately. |
| 3105 | */ |
| 3106 | png_set_progressive_read_fn(png_ptr, (void *)user_ptr, |
| 3107 | info_callback, row_callback, end_callback); |
| 3108 | |
| 3109 | return 0; |
| 3110 | } |
| 3111 | |
| 3112 | /* A code fragment that you call as you receive blocks |
| 3113 | of data */ |
| 3114 | int |
| 3115 | process_data(png_bytep buffer, png_uint_32 length) |
| 3116 | { |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 3117 | if (setjmp(png_jmpbuf(png_ptr))) |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3118 | { |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3119 | png_destroy_read_struct(&png_ptr, &info_ptr, |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3120 | (png_infopp)NULL); |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 3121 | return ERROR; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3122 | } |
| 3123 | |
| 3124 | /* This one's new also. Simply give it a chunk |
| 3125 | of data from the file stream (in order, of |
| 3126 | course). On machines with segmented memory |
| 3127 | models machines, don't give it any more than |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 3128 | 64K. The library seems to run fine with sizes |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3129 | of 4K. Although you can give it much less if |
| 3130 | necessary (I assume you can give it chunks of |
Glenn Randers-Pehrson | bbe2be3 | 2015-03-07 13:13:11 -0600 | [diff] [blame] | 3131 | 1 byte, I haven't tried less than 256 bytes |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3132 | yet). When this function returns, you may |
| 3133 | want to display any rows that were generated |
| 3134 | in the row callback if you don't already do |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 3135 | so there. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3136 | */ |
| 3137 | png_process_data(png_ptr, info_ptr, buffer, length); |
John Bowler | f19abd6 | 2011-01-22 18:29:24 -0600 | [diff] [blame] | 3138 | |
| 3139 | /* At this point you can call png_process_data_skip if |
| 3140 | you want to handle data the library will skip yourself; |
| 3141 | it simply returns the number of bytes to skip (and stops |
| 3142 | libpng skipping that number of bytes on the next |
| 3143 | png_process_data call). |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3144 | return 0; |
| 3145 | } |
| 3146 | |
| 3147 | /* This function is called (as set by |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 3148 | png_set_progressive_read_fn() above) when enough data |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3149 | has been supplied so all of the header has been |
| 3150 | read. |
| 3151 | */ |
| 3152 | void |
Glenn Randers-Pehrson | 08a3343 | 1998-03-07 06:06:55 -0600 | [diff] [blame] | 3153 | info_callback(png_structp png_ptr, png_infop info) |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3154 | { |
| 3155 | /* Do any setup here, including setting any of |
| 3156 | the transformations mentioned in the Reading |
| 3157 | PNG files section. For now, you _must_ call |
| 3158 | either png_start_read_image() or |
| 3159 | png_read_update_info() after all the |
| 3160 | transformations are set (even if you don't set |
| 3161 | any). You may start getting rows before |
| 3162 | png_process_data() returns, so this is your |
| 3163 | last chance to prepare for that. |
Glenn Randers-Pehrson | 6e97410 | 2010-12-19 16:44:22 -0600 | [diff] [blame] | 3164 | |
| 3165 | This is where you turn on interlace handling, |
| 3166 | assuming you don't want to do it yourself. |
John Bowler | f19abd6 | 2011-01-22 18:29:24 -0600 | [diff] [blame] | 3167 | |
| 3168 | If you need to you can stop the processing of |
| 3169 | your original input data at this point by calling |
| 3170 | png_process_data_pause. This returns the number |
| 3171 | of unprocessed bytes from the last png_process_data |
| 3172 | call - it is up to you to ensure that the next call |
| 3173 | sees these bytes again. If you don't want to bother |
| 3174 | with this you can get libpng to cache the unread |
| 3175 | bytes by setting the 'save' parameter (see png.h) but |
| 3176 | then libpng will have to copy the data internally. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3177 | */ |
| 3178 | } |
| 3179 | |
| 3180 | /* This function is called when each row of image |
| 3181 | data is complete */ |
| 3182 | void |
| 3183 | row_callback(png_structp png_ptr, png_bytep new_row, |
Glenn Randers-Pehrson | e68f5a3 | 2001-05-14 09:20:53 -0500 | [diff] [blame] | 3184 | png_uint_32 row_num, int pass) |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3185 | { |
| 3186 | /* If the image is interlaced, and you turned |
| 3187 | on the interlace handler, this function will |
| 3188 | be called for every row in every pass. Some |
| 3189 | of these rows will not be changed from the |
| 3190 | previous pass. When the row is not changed, |
| 3191 | the new_row variable will be NULL. The rows |
| 3192 | and passes are called in order, so you don't |
| 3193 | really need the row_num and pass, but I'm |
| 3194 | supplying them because it may make your life |
| 3195 | easier. |
| 3196 | |
Glenn Randers-Pehrson | 6e97410 | 2010-12-19 16:44:22 -0600 | [diff] [blame] | 3197 | If you did not turn on interlace handling then |
| 3198 | the callback is called for each row of each |
| 3199 | sub-image when the image is interlaced. In this |
| 3200 | case 'row_num' is the row in the sub-image, not |
| 3201 | the row in the output image as it is in all other |
| 3202 | cases. |
| 3203 | |
| 3204 | For the non-NULL rows of interlaced images when |
| 3205 | you have switched on libpng interlace handling, |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3206 | you must call png_progressive_combine_row() |
| 3207 | passing in the row and the old row. You can |
| 3208 | call this function for NULL rows (it will just |
| 3209 | return) and for non-interlaced images (it just |
| 3210 | does the memcpy for you) if it will make the |
| 3211 | code easier. Thus, you can just do this for |
Glenn Randers-Pehrson | 6e97410 | 2010-12-19 16:44:22 -0600 | [diff] [blame] | 3212 | all cases if you switch on interlace handling; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3213 | */ |
| 3214 | |
| 3215 | png_progressive_combine_row(png_ptr, old_row, |
| 3216 | new_row); |
| 3217 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 3218 | /* where old_row is what was displayed |
Glenn Randers-Pehrson | 345bc27 | 1998-06-14 14:43:31 -0500 | [diff] [blame] | 3219 | previously for the row. Note that the first |
| 3220 | pass (pass == 0, really) will completely cover |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3221 | the old row, so the rows do not have to be |
| 3222 | initialized. After the first pass (and only |
| 3223 | for interlaced images), you will have to pass |
| 3224 | the current row, and the function will combine |
| 3225 | the old row and the new row. |
John Bowler | f19abd6 | 2011-01-22 18:29:24 -0600 | [diff] [blame] | 3226 | |
| 3227 | You can also call png_process_data_pause in this |
| 3228 | callback - see above. |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 3229 | */ |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3230 | } |
| 3231 | |
| 3232 | void |
| 3233 | end_callback(png_structp png_ptr, png_infop info) |
| 3234 | { |
| 3235 | /* This function is called after the whole image |
| 3236 | has been read, including any chunks after the |
| 3237 | image (up to and including the IEND). You |
| 3238 | will usually have the same info chunk as you |
| 3239 | had in the header, although some data may have |
| 3240 | been added to the comments and time fields. |
| 3241 | |
| 3242 | Most people won't do much here, perhaps setting |
| 3243 | a flag that marks the image as finished. |
| 3244 | */ |
| 3245 | } |
| 3246 | |
Glenn Randers-Pehrson | 896239b | 1998-04-21 15:03:57 -0500 | [diff] [blame] | 3247 | |
| 3248 | |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 3249 | .SH IV. Writing |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3250 | |
| 3251 | Much of this is very similar to reading. However, everything of |
| 3252 | importance is repeated here, so you won't have to constantly look |
| 3253 | back up in the reading section to understand writing. |
| 3254 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3255 | .SS Setup |
| 3256 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3257 | You will want to do the I/O initialization before you get into libpng, |
| 3258 | so if it doesn't work, you don't have anything to undo. If you are not |
| 3259 | using the standard I/O functions, you will need to replace them with |
| 3260 | custom writing functions. See the discussion under Customizing libpng. |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 3261 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3262 | FILE *fp = fopen(file_name, "wb"); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3263 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3264 | if (!fp) |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 3265 | return ERROR; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3266 | |
| 3267 | Next, png_struct and png_info need to be allocated and initialized. |
| 3268 | As these can be both relatively large, you may not want to store these |
| 3269 | on the stack, unless you have stack space to spare. Of course, you |
Glenn Randers-Pehrson | 08a3343 | 1998-03-07 06:06:55 -0600 | [diff] [blame] | 3270 | will want to check if they return NULL. If you are also reading, |
| 3271 | you won't want to name your read structure and your write structure |
| 3272 | both "png_ptr"; you can call them anything you like, such as |
| 3273 | "read_ptr" and "write_ptr". Look at pngtest.c, for example. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3274 | |
| 3275 | png_structp png_ptr = png_create_write_struct |
Glenn Randers-Pehrson | 61ea3ea | 2014-11-06 06:39:56 -0600 | [diff] [blame] | 3276 | (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3277 | user_error_fn, user_warning_fn); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3278 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3279 | if (!png_ptr) |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 3280 | return ERROR; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3281 | |
| 3282 | png_infop info_ptr = png_create_info_struct(png_ptr); |
| 3283 | if (!info_ptr) |
| 3284 | { |
| 3285 | png_destroy_write_struct(&png_ptr, |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3286 | (png_infopp)NULL); |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 3287 | return ERROR; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3288 | } |
| 3289 | |
Glenn Randers-Pehrson | f7d1a17 | 1998-06-06 15:31:35 -0500 | [diff] [blame] | 3290 | If you want to use your own memory allocation routines, |
| 3291 | define PNG_USER_MEM_SUPPORTED and use |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 3292 | png_create_write_struct_2() instead of png_create_write_struct(): |
Glenn Randers-Pehrson | f7d1a17 | 1998-06-06 15:31:35 -0500 | [diff] [blame] | 3293 | |
| 3294 | png_structp png_ptr = png_create_write_struct_2 |
Glenn Randers-Pehrson | 61ea3ea | 2014-11-06 06:39:56 -0600 | [diff] [blame] | 3295 | (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, |
Glenn Randers-Pehrson | f7d1a17 | 1998-06-06 15:31:35 -0500 | [diff] [blame] | 3296 | user_error_fn, user_warning_fn, (png_voidp) |
| 3297 | user_mem_ptr, user_malloc_fn, user_free_fn); |
| 3298 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3299 | After you have these structures, you will need to set up the |
| 3300 | error handling. When libpng encounters an error, it expects to |
| 3301 | longjmp() back to your routine. Therefore, you will need to call |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 3302 | setjmp() and pass the png_jmpbuf(png_ptr). If you |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3303 | write the file from different routines, you will need to update |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 3304 | the png_jmpbuf(png_ptr) every time you enter a new routine that will |
| 3305 | call a png_*() function. See your documentation of setjmp/longjmp |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3306 | for your compiler for more information on setjmp/longjmp. See |
| 3307 | the discussion on libpng error handling in the Customizing Libpng |
| 3308 | section below for more information on the libpng error handling. |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 3309 | |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 3310 | if (setjmp(png_jmpbuf(png_ptr))) |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 3311 | { |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3312 | png_destroy_write_struct(&png_ptr, &info_ptr); |
Glenn Randers-Pehrson | 104622b | 2000-05-29 08:58:03 -0500 | [diff] [blame] | 3313 | fclose(fp); |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 3314 | return ERROR; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3315 | } |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 3316 | ... |
| 3317 | return; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3318 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3319 | If you would rather avoid the complexity of setjmp/longjmp issues, |
Glenn Randers-Pehrson | 54ac9a9 | 2010-04-02 17:06:22 -0500 | [diff] [blame] | 3320 | you can compile libpng with PNG_NO_SETJMP, in which case |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3321 | errors will result in a call to PNG_ABORT() which defaults to abort(). |
| 3322 | |
Glenn Randers-Pehrson | 54ac9a9 | 2010-04-02 17:06:22 -0500 | [diff] [blame] | 3323 | You can #define PNG_ABORT() to a function that does something |
| 3324 | more useful than abort(), as long as your function does not |
| 3325 | return. |
| 3326 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 3327 | Checking for invalid palette index on write was added at libpng |
| 3328 | 1.5.10. If a pixel contains an invalid (out-of-range) index libpng issues |
| 3329 | a benign error. This is enabled by default because this condition is an |
| 3330 | error according to the PNG specification, Clause 11.3.2, but the error can |
| 3331 | be ignored in each png_ptr with |
| 3332 | |
| 3333 | png_set_check_for_invalid_index(png_ptr, 0); |
| 3334 | |
| 3335 | If the error is ignored, or if png_benign_error() treats it as a warning, |
| 3336 | any invalid pixels are written as-is by the encoder, resulting in an |
| 3337 | invalid PNG datastream as output. In this case the application is |
| 3338 | responsible for ensuring that the pixel indexes are in range when it writes |
| 3339 | a PLTE chunk with fewer entries than the bit depth would allow. |
| 3340 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3341 | Now you need to set up the output code. The default for libpng is to |
| 3342 | use the C function fwrite(). If you use this, you will need to pass a |
| 3343 | valid FILE * in the function png_init_io(). Be sure that the file is |
| 3344 | opened in binary mode. Again, if you wish to handle writing data in |
| 3345 | another way, see the discussion on libpng I/O handling in the Customizing |
| 3346 | Libpng section below. |
| 3347 | |
| 3348 | png_init_io(png_ptr, fp); |
| 3349 | |
Glenn Randers-Pehrson | d60b8fa | 2006-04-20 21:31:14 -0500 | [diff] [blame] | 3350 | If you are embedding your PNG into a datastream such as MNG, and don't |
| 3351 | want libpng to write the 8-byte signature, or if you have already |
| 3352 | written the signature in your application, use |
| 3353 | |
| 3354 | png_set_sig_bytes(png_ptr, 8); |
| 3355 | |
| 3356 | to inform libpng that it should not write a signature. |
| 3357 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3358 | .SS Write callbacks |
| 3359 | |
Glenn Randers-Pehrson | 08a3343 | 1998-03-07 06:06:55 -0600 | [diff] [blame] | 3360 | At this point, you can set up a callback function that will be |
| 3361 | called after each row has been written, which you can use to control |
| 3362 | a progress meter or the like. It's demonstrated in pngtest.c. |
| 3363 | You must supply a function |
| 3364 | |
Glenn Randers-Pehrson | 81ce889 | 2011-01-24 08:04:37 -0600 | [diff] [blame] | 3365 | void write_row_callback(png_structp png_ptr, png_uint_32 row, |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 3366 | int pass); |
Glenn Randers-Pehrson | 08a3343 | 1998-03-07 06:06:55 -0600 | [diff] [blame] | 3367 | { |
| 3368 | /* put your code here */ |
| 3369 | } |
| 3370 | |
| 3371 | (You can give it another name that you like instead of "write_row_callback") |
| 3372 | |
| 3373 | To inform libpng about your function, use |
| 3374 | |
| 3375 | png_set_write_status_fn(png_ptr, write_row_callback); |
| 3376 | |
John Bowler | 59010e5 | 2011-02-16 06:16:31 -0600 | [diff] [blame] | 3377 | When this function is called the row has already been completely processed and |
| 3378 | it has also been written out. The 'row' and 'pass' refer to the next row to be |
| 3379 | handled. For the |
| 3380 | non-interlaced case the row that was just handled is simply one less than the |
| 3381 | passed in row number, and pass will always be 0. For the interlaced case the |
| 3382 | same applies unless the row value is 0, in which case the row just handled was |
| 3383 | the last one from one of the preceding passes. Because interlacing may skip a |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 3384 | pass you cannot be sure that the preceding pass is just 'pass\-1', if you really |
John Bowler | 59010e5 | 2011-02-16 06:16:31 -0600 | [diff] [blame] | 3385 | need to know what the last pass is record (row,pass) from the callback and use |
| 3386 | the last recorded value each time. |
| 3387 | |
| 3388 | As with the user transform you can find the output row using the |
| 3389 | PNG_ROW_FROM_PASS_ROW macro. |
| 3390 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3391 | You now have the option of modifying how the compression library will |
| 3392 | run. The following functions are mainly for testing, but may be useful |
| 3393 | in some cases, like if you need to write PNG files extremely fast and |
| 3394 | are willing to give up some compression, or if you want to get the |
| 3395 | maximum possible compression at the expense of slower writing. If you |
| 3396 | have no special needs in this area, let the library do what it wants by |
| 3397 | not calling this function at all, as it has been tuned to deliver a good |
| 3398 | speed/compression ratio. The second parameter to png_set_filter() is |
Glenn Randers-Pehrson | 408b421 | 2000-12-18 09:33:57 -0600 | [diff] [blame] | 3399 | the filter method, for which the only valid values are 0 (as of the |
| 3400 | July 1999 PNG specification, version 1.2) or 64 (if you are writing |
| 3401 | a PNG datastream that is to be embedded in a MNG datastream). The third |
| 3402 | parameter is a flag that indicates which filter type(s) are to be tested |
Glenn Randers-Pehrson | f210a05 | 2009-11-12 10:02:24 -0600 | [diff] [blame] | 3403 | for each scanline. See the PNG specification for details on the specific |
| 3404 | filter types. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3405 | |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 3406 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3407 | /* turn on or off filtering, and/or choose |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 3408 | specific filters. You can use either a single |
Glenn Randers-Pehrson | ebd7f9a | 2006-10-19 09:37:56 -0500 | [diff] [blame] | 3409 | PNG_FILTER_VALUE_NAME or the bitwise OR of one |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3410 | or more PNG_FILTER_NAME masks. |
| 3411 | */ |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3412 | png_set_filter(png_ptr, 0, |
Glenn Randers-Pehrson | 228bd39 | 2000-04-23 23:14:02 -0500 | [diff] [blame] | 3413 | PNG_FILTER_NONE | PNG_FILTER_VALUE_NONE | |
| 3414 | PNG_FILTER_SUB | PNG_FILTER_VALUE_SUB | |
| 3415 | PNG_FILTER_UP | PNG_FILTER_VALUE_UP | |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 3416 | PNG_FILTER_AVG | PNG_FILTER_VALUE_AVG | |
Glenn Randers-Pehrson | 228bd39 | 2000-04-23 23:14:02 -0500 | [diff] [blame] | 3417 | PNG_FILTER_PAETH | PNG_FILTER_VALUE_PAETH| |
Glenn Randers-Pehrson | fa551df | 2016-04-11 08:23:16 -0500 | [diff] [blame] | 3418 | PNG_ALL_FILTERS | PNG_FAST_FILTERS); |
Glenn Randers-Pehrson | 228bd39 | 2000-04-23 23:14:02 -0500 | [diff] [blame] | 3419 | |
Glenn Randers-Pehrson | 6e97410 | 2010-12-19 16:44:22 -0600 | [diff] [blame] | 3420 | If an application wants to start and stop using particular filters during |
| 3421 | compression, it should start out with all of the filters (to ensure that |
| 3422 | the previous row of pixels will be stored in case it's needed later), |
| 3423 | and then add and remove them after the start of compression. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3424 | |
Glenn Randers-Pehrson | 408b421 | 2000-12-18 09:33:57 -0600 | [diff] [blame] | 3425 | If you are writing a PNG datastream that is to be embedded in a MNG |
| 3426 | datastream, the second parameter can be either 0 or 64. |
| 3427 | |
Glenn Randers-Pehrson | a77ef62 | 2000-02-18 13:48:52 -0600 | [diff] [blame] | 3428 | The png_set_compression_*() functions interface to the zlib compression |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3429 | library, and should mostly be ignored unless you really know what you are |
| 3430 | doing. The only generally useful call is png_set_compression_level() |
| 3431 | which changes how much time zlib spends on trying to compress the image |
Glenn Randers-Pehrson | 228bd39 | 2000-04-23 23:14:02 -0500 | [diff] [blame] | 3432 | data. See the Compression Library (zlib.h and algorithm.txt, distributed |
| 3433 | with zlib) for details on the compression levels. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3434 | |
Glenn Randers-Pehrson | 38734ee | 2011-03-03 06:23:31 -0600 | [diff] [blame] | 3435 | #include zlib.h |
| 3436 | |
Glenn Randers-Pehrson | a45f47c | 2011-04-01 15:31:26 -0500 | [diff] [blame] | 3437 | /* Set the zlib compression level */ |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3438 | png_set_compression_level(png_ptr, |
| 3439 | Z_BEST_COMPRESSION); |
| 3440 | |
Glenn Randers-Pehrson | a45f47c | 2011-04-01 15:31:26 -0500 | [diff] [blame] | 3441 | /* Set other zlib parameters for compressing IDAT */ |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3442 | png_set_compression_mem_level(png_ptr, 8); |
| 3443 | png_set_compression_strategy(png_ptr, |
| 3444 | Z_DEFAULT_STRATEGY); |
| 3445 | png_set_compression_window_bits(png_ptr, 15); |
| 3446 | png_set_compression_method(png_ptr, 8); |
Glenn Randers-Pehrson | 228bd39 | 2000-04-23 23:14:02 -0500 | [diff] [blame] | 3447 | png_set_compression_buffer_size(png_ptr, 8192) |
| 3448 | |
Glenn Randers-Pehrson | a45f47c | 2011-04-01 15:31:26 -0500 | [diff] [blame] | 3449 | /* Set zlib parameters for text compression |
| 3450 | * If you don't call these, the parameters |
| 3451 | * fall back on those defined for IDAT chunks |
| 3452 | */ |
Glenn Randers-Pehrson | 8eb8833 | 2011-04-01 00:16:50 -0500 | [diff] [blame] | 3453 | png_set_text_compression_mem_level(png_ptr, 8); |
| 3454 | png_set_text_compression_strategy(png_ptr, |
| 3455 | Z_DEFAULT_STRATEGY); |
| 3456 | png_set_text_compression_window_bits(png_ptr, 15); |
| 3457 | png_set_text_compression_method(png_ptr, 8); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3458 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3459 | .SS Setting the contents of info for output |
| 3460 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3461 | You now need to fill in the png_info structure with all the data you |
| 3462 | wish to write before the actual image. Note that the only thing you |
| 3463 | are allowed to write after the image is the text chunks and the time |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 3464 | chunk (as of PNG Specification 1.2, anyway). See png_write_end() and |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3465 | the latest PNG specification for more information on that. If you |
| 3466 | wish to write them before the image, fill them in now, and flag that |
| 3467 | data as being valid. If you want to wait until after the data, don't |
| 3468 | fill them until png_write_end(). For all the fields in png_info and |
| 3469 | their data types, see png.h. For explanations of what the fields |
| 3470 | contain, see the PNG specification. |
| 3471 | |
| 3472 | Some of the more important parts of the png_info are: |
| 3473 | |
| 3474 | png_set_IHDR(png_ptr, info_ptr, width, height, |
| 3475 | bit_depth, color_type, interlace_type, |
Glenn Randers-Pehrson | 408b421 | 2000-12-18 09:33:57 -0600 | [diff] [blame] | 3476 | compression_type, filter_method) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3477 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3478 | width - holds the width of the image |
| 3479 | in pixels (up to 2^31). |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3480 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3481 | height - holds the height of the image |
| 3482 | in pixels (up to 2^31). |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3483 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3484 | bit_depth - holds the bit depth of one of the |
| 3485 | image channels. |
| 3486 | (valid values are 1, 2, 4, 8, 16 |
| 3487 | and depend also on the |
| 3488 | color_type. See also significant |
| 3489 | bits (sBIT) below). |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3490 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3491 | color_type - describes which color/alpha |
| 3492 | channels are present. |
| 3493 | PNG_COLOR_TYPE_GRAY |
| 3494 | (bit depths 1, 2, 4, 8, 16) |
| 3495 | PNG_COLOR_TYPE_GRAY_ALPHA |
| 3496 | (bit depths 8, 16) |
| 3497 | PNG_COLOR_TYPE_PALETTE |
| 3498 | (bit depths 1, 2, 4, 8) |
| 3499 | PNG_COLOR_TYPE_RGB |
| 3500 | (bit_depths 8, 16) |
| 3501 | PNG_COLOR_TYPE_RGB_ALPHA |
| 3502 | (bit_depths 8, 16) |
| 3503 | |
| 3504 | PNG_COLOR_MASK_PALETTE |
| 3505 | PNG_COLOR_MASK_COLOR |
| 3506 | PNG_COLOR_MASK_ALPHA |
| 3507 | |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 3508 | interlace_type - PNG_INTERLACE_NONE or |
| 3509 | PNG_INTERLACE_ADAM7 |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3510 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3511 | compression_type - (must be |
| 3512 | PNG_COMPRESSION_TYPE_DEFAULT) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3513 | |
Glenn Randers-Pehrson | 408b421 | 2000-12-18 09:33:57 -0600 | [diff] [blame] | 3514 | filter_method - (must be PNG_FILTER_TYPE_DEFAULT |
| 3515 | or, if you are writing a PNG to |
| 3516 | be embedded in a MNG datastream, |
| 3517 | can also be |
| 3518 | PNG_INTRAPIXEL_DIFFERENCING) |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3519 | |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 3520 | If you call png_set_IHDR(), the call must appear before any of the |
Glenn Randers-Pehrson | d60c886 | 2009-06-15 21:56:14 -0500 | [diff] [blame] | 3521 | other png_set_*() functions, because they might require access to some of |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 3522 | the IHDR settings. The remaining png_set_*() functions can be called |
| 3523 | in any order. |
| 3524 | |
Glenn Randers-Pehrson | b5444a1 | 2009-06-08 08:36:19 -0500 | [diff] [blame] | 3525 | If you wish, you can reset the compression_type, interlace_type, or |
| 3526 | filter_method later by calling png_set_IHDR() again; if you do this, the |
| 3527 | width, height, bit_depth, and color_type must be the same in each call. |
Glenn Randers-Pehrson | 424c985 | 2009-06-02 13:45:15 -0500 | [diff] [blame] | 3528 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3529 | png_set_PLTE(png_ptr, info_ptr, palette, |
| 3530 | num_palette); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3531 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3532 | palette - the palette for the file |
| 3533 | (array of png_color) |
| 3534 | num_palette - number of entries in the palette |
| 3535 | |
Glenn Randers-Pehrson | 5b6a6f9 | 2015-12-02 19:50:48 -0600 | [diff] [blame] | 3536 | |
Glenn Randers-Pehrson | 8d0bc0f | 2011-01-25 22:15:58 -0600 | [diff] [blame] | 3537 | png_set_gAMA(png_ptr, info_ptr, file_gamma); |
| 3538 | png_set_gAMA_fixed(png_ptr, info_ptr, int_file_gamma); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3539 | |
Glenn Randers-Pehrson | 8d0bc0f | 2011-01-25 22:15:58 -0600 | [diff] [blame] | 3540 | file_gamma - the gamma at which the image was |
| 3541 | created (PNG_INFO_gAMA) |
| 3542 | |
| 3543 | int_file_gamma - 100,000 times the gamma at which |
| 3544 | the image was created |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3545 | |
John Bowler | bbd17bd | 2011-08-25 17:48:18 -0500 | [diff] [blame] | 3546 | png_set_cHRM(png_ptr, info_ptr, white_x, white_y, red_x, red_y, |
| 3547 | green_x, green_y, blue_x, blue_y) |
| 3548 | png_set_cHRM_XYZ(png_ptr, info_ptr, red_X, red_Y, red_Z, green_X, |
| 3549 | green_Y, green_Z, blue_X, blue_Y, blue_Z) |
| 3550 | png_set_cHRM_fixed(png_ptr, info_ptr, int_white_x, int_white_y, |
| 3551 | int_red_x, int_red_y, int_green_x, int_green_y, |
| 3552 | int_blue_x, int_blue_y) |
| 3553 | png_set_cHRM_XYZ_fixed(png_ptr, info_ptr, int_red_X, int_red_Y, |
| 3554 | int_red_Z, int_green_X, int_green_Y, int_green_Z, |
| 3555 | int_blue_X, int_blue_Y, int_blue_Z) |
| 3556 | |
| 3557 | {white,red,green,blue}_{x,y} |
| 3558 | A color space encoding specified using the chromaticities |
| 3559 | of the end points and the white point. |
| 3560 | |
| 3561 | {red,green,blue}_{X,Y,Z} |
| 3562 | A color space encoding specified using the encoding end |
| 3563 | points - the CIE tristimulus specification of the intended |
| 3564 | color of the red, green and blue channels in the PNG RGB |
| 3565 | data. The white point is simply the sum of the three end |
| 3566 | points. |
| 3567 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3568 | png_set_sRGB(png_ptr, info_ptr, srgb_intent); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3569 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3570 | srgb_intent - the rendering intent |
| 3571 | (PNG_INFO_sRGB) The presence of |
| 3572 | the sRGB chunk means that the pixel |
| 3573 | data is in the sRGB color space. |
| 3574 | This chunk also implies specific |
| 3575 | values of gAMA and cHRM. Rendering |
| 3576 | intent is the CSS-1 property that |
| 3577 | has been defined by the International |
| 3578 | Color Consortium |
| 3579 | (http://www.color.org). |
| 3580 | It can be one of |
Glenn Randers-Pehrson | 5379b24 | 1999-11-27 10:22:33 -0600 | [diff] [blame] | 3581 | PNG_sRGB_INTENT_SATURATION, |
| 3582 | PNG_sRGB_INTENT_PERCEPTUAL, |
| 3583 | PNG_sRGB_INTENT_ABSOLUTE, or |
| 3584 | PNG_sRGB_INTENT_RELATIVE. |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 3585 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3586 | |
| 3587 | png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr, |
| 3588 | srgb_intent); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3589 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3590 | srgb_intent - the rendering intent |
| 3591 | (PNG_INFO_sRGB) The presence of the |
| 3592 | sRGB chunk means that the pixel |
| 3593 | data is in the sRGB color space. |
| 3594 | This function also causes gAMA and |
| 3595 | cHRM chunks with the specific values |
| 3596 | that are consistent with sRGB to be |
| 3597 | written. |
| 3598 | |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 3599 | png_set_iCCP(png_ptr, info_ptr, name, compression_type, |
Glenn Randers-Pehrson | 4a5a1ec | 2011-01-15 11:43:28 -0600 | [diff] [blame] | 3600 | profile, proflen); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3601 | |
Glenn Randers-Pehrson | 4a5a1ec | 2011-01-15 11:43:28 -0600 | [diff] [blame] | 3602 | name - The profile name. |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3603 | |
Glenn Randers-Pehrson | 4a5a1ec | 2011-01-15 11:43:28 -0600 | [diff] [blame] | 3604 | compression_type - The compression type; always |
| 3605 | PNG_COMPRESSION_TYPE_BASE for PNG 1.0. |
| 3606 | You may give NULL to this argument to |
| 3607 | ignore it. |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3608 | |
Glenn Randers-Pehrson | 4a5a1ec | 2011-01-15 11:43:28 -0600 | [diff] [blame] | 3609 | profile - International Color Consortium color |
| 3610 | profile data. May contain NULs. |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3611 | |
Glenn Randers-Pehrson | 4a5a1ec | 2011-01-15 11:43:28 -0600 | [diff] [blame] | 3612 | proflen - length of profile data in bytes. |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 3613 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3614 | png_set_sBIT(png_ptr, info_ptr, sig_bit); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3615 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3616 | sig_bit - the number of significant bits for |
| 3617 | (PNG_INFO_sBIT) each of the gray, red, |
| 3618 | green, and blue channels, whichever are |
| 3619 | appropriate for the given color type |
| 3620 | (png_color_16) |
| 3621 | |
Glenn Randers-Pehrson | 866b62a | 2009-08-08 16:33:14 -0500 | [diff] [blame] | 3622 | png_set_tRNS(png_ptr, info_ptr, trans_alpha, |
| 3623 | num_trans, trans_color); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3624 | |
Glenn Randers-Pehrson | 866b62a | 2009-08-08 16:33:14 -0500 | [diff] [blame] | 3625 | trans_alpha - array of alpha (transparency) |
| 3626 | entries for palette (PNG_INFO_tRNS) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3627 | |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 3628 | num_trans - number of transparent entries |
| 3629 | (PNG_INFO_tRNS) |
| 3630 | |
Glenn Randers-Pehrson | b5444a1 | 2009-06-08 08:36:19 -0500 | [diff] [blame] | 3631 | trans_color - graylevel or color sample values |
| 3632 | (in order red, green, blue) of the |
| 3633 | single transparent color for |
Glenn Randers-Pehrson | 3d5a520 | 2000-07-01 15:37:28 -0500 | [diff] [blame] | 3634 | non-paletted images (PNG_INFO_tRNS) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3635 | |
Glenn Randers-Pehrson | 6f89dff | 2017-08-03 10:27:09 -0500 | [diff] [blame] | 3636 | png_set_eXIf_1(png_ptr, info_ptr, num_exif, exif); |
Glenn Randers-Pehrson | 7c709f0 | 2017-08-02 16:48:11 -0500 | [diff] [blame] | 3637 | |
Glenn Randers-Pehrson | f8de55d | 2017-08-02 06:54:10 -0500 | [diff] [blame] | 3638 | exif - Exif profile (array of |
Glenn Randers-Pehrson | 68cb0aa | 2017-07-13 11:19:53 -0500 | [diff] [blame] | 3639 | png_byte) (PNG_INFO_eXIf) |
| 3640 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3641 | png_set_hIST(png_ptr, info_ptr, hist); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3642 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3643 | hist - histogram of palette (array of |
Glenn Randers-Pehrson | 8d0bc0f | 2011-01-25 22:15:58 -0600 | [diff] [blame] | 3644 | png_uint_16) (PNG_INFO_hIST) |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3645 | |
| 3646 | png_set_tIME(png_ptr, info_ptr, mod_time); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3647 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3648 | mod_time - time image was last modified |
| 3649 | (PNG_VALID_tIME) |
| 3650 | |
| 3651 | png_set_bKGD(png_ptr, info_ptr, background); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3652 | |
Glenn Randers-Pehrson | ab38979 | 2011-07-09 19:35:22 -0500 | [diff] [blame] | 3653 | background - background color (of type |
| 3654 | png_color_16p) (PNG_VALID_bKGD) |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3655 | |
| 3656 | png_set_text(png_ptr, info_ptr, text_ptr, num_text); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3657 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3658 | text_ptr - array of png_text holding image |
| 3659 | comments |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3660 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 3661 | text_ptr[i].compression - type of compression used |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3662 | on "text" PNG_TEXT_COMPRESSION_NONE |
| 3663 | PNG_TEXT_COMPRESSION_zTXt |
| 3664 | PNG_ITXT_COMPRESSION_NONE |
| 3665 | PNG_ITXT_COMPRESSION_zTXt |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 3666 | text_ptr[i].key - keyword for comment. Must contain |
| 3667 | 1-79 characters. |
| 3668 | text_ptr[i].text - text comments for current |
| 3669 | keyword. Can be NULL or empty. |
| 3670 | text_ptr[i].text_length - length of text string, |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3671 | after decompression, 0 for iTXt |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 3672 | text_ptr[i].itxt_length - length of itxt string, |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3673 | after decompression, 0 for tEXt/zTXt |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 3674 | text_ptr[i].lang - language of comment (NULL or |
| 3675 | empty for unknown). |
| 3676 | text_ptr[i].translated_keyword - keyword in UTF-8 (NULL |
| 3677 | or empty for unknown). |
Glenn Randers-Pehrson | 680da02 | 2011-11-21 17:05:41 -0600 | [diff] [blame] | 3678 | |
Glenn Randers-Pehrson | 8f5846f | 2009-10-31 21:31:08 -0500 | [diff] [blame] | 3679 | Note that the itxt_length, lang, and lang_key |
Glenn Randers-Pehrson | 680da02 | 2011-11-21 17:05:41 -0600 | [diff] [blame] | 3680 | members of the text_ptr structure only exist when the |
| 3681 | library is built with iTXt chunk support. Prior to |
| 3682 | libpng-1.4.0 the library was built by default without |
| 3683 | iTXt support. Also note that when iTXt is supported, |
| 3684 | they contain NULL pointers when the "compression" |
| 3685 | field contains PNG_TEXT_COMPRESSION_NONE or |
| 3686 | PNG_TEXT_COMPRESSION_zTXt. |
Glenn Randers-Pehrson | 8f5846f | 2009-10-31 21:31:08 -0500 | [diff] [blame] | 3687 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3688 | num_text - number of comments |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3689 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 3690 | png_set_sPLT(png_ptr, info_ptr, &palette_ptr, |
| 3691 | num_spalettes); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3692 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 3693 | palette_ptr - array of png_sPLT_struct structures |
| 3694 | to be added to the list of palettes |
| 3695 | in the info structure. |
| 3696 | num_spalettes - number of palette structures to be |
| 3697 | added. |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 3698 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3699 | png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y, |
| 3700 | unit_type); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3701 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3702 | offset_x - positive offset from the left |
| 3703 | edge of the screen |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3704 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3705 | offset_y - positive offset from the top |
| 3706 | edge of the screen |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3707 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3708 | unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER |
| 3709 | |
| 3710 | png_set_pHYs(png_ptr, info_ptr, res_x, res_y, |
| 3711 | unit_type); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3712 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3713 | res_x - pixels/unit physical resolution |
| 3714 | in x direction |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3715 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3716 | res_y - pixels/unit physical resolution |
| 3717 | in y direction |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3718 | |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 3719 | unit_type - PNG_RESOLUTION_UNKNOWN, |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3720 | PNG_RESOLUTION_METER |
| 3721 | |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 3722 | png_set_sCAL(png_ptr, info_ptr, unit, width, height) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3723 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 3724 | unit - physical scale units (an integer) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3725 | |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 3726 | width - width of a pixel in physical scale units |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3727 | |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 3728 | height - height of a pixel in physical scale units |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 3729 | (width and height are doubles) |
| 3730 | |
| 3731 | png_set_sCAL_s(png_ptr, info_ptr, unit, width, height) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3732 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 3733 | unit - physical scale units (an integer) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3734 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 3735 | width - width of a pixel in physical scale units |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 3736 | expressed as a string |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3737 | |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 3738 | height - height of a pixel in physical scale units |
| 3739 | (width and height are strings like "2.54") |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 3740 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 3741 | png_set_unknown_chunks(png_ptr, info_ptr, &unknowns, |
| 3742 | num_unknowns) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3743 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 3744 | unknowns - array of png_unknown_chunk |
| 3745 | structures holding unknown chunks |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 3746 | unknowns[i].name - name of unknown chunk |
| 3747 | unknowns[i].data - data of unknown chunk |
Glenn Randers-Pehrson | 4accabb | 2000-04-14 14:20:47 -0500 | [diff] [blame] | 3748 | unknowns[i].size - size of unknown chunk's data |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3749 | unknowns[i].location - position to write chunk in file |
| 3750 | 0: do not write chunk |
| 3751 | PNG_HAVE_IHDR: before PLTE |
| 3752 | PNG_HAVE_PLTE: before IDAT |
| 3753 | PNG_AFTER_IDAT: after IDAT |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 3754 | |
| 3755 | The "location" member is set automatically according to |
| 3756 | what part of the output file has already been written. |
| 3757 | You can change its value after calling png_set_unknown_chunks() |
| 3758 | as demonstrated in pngtest.c. Within each of the "locations", |
| 3759 | the chunks are sequenced according to their position in the |
| 3760 | structure (that is, the value of "i", which is the order in which |
| 3761 | the chunk was either read from the input file or defined with |
| 3762 | png_set_unknown_chunks). |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3763 | |
| 3764 | A quick word about text and num_text. text is an array of png_text |
| 3765 | structures. num_text is the number of valid structures in the array. |
Glenn Randers-Pehrson | 228bd39 | 2000-04-23 23:14:02 -0500 | [diff] [blame] | 3766 | Each png_text structure holds a language code, a keyword, a text value, |
| 3767 | and a compression type. |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 3768 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3769 | The compression types have the same valid numbers as the compression |
| 3770 | types of the image data. Currently, the only valid number is zero. |
| 3771 | However, you can store text either compressed or uncompressed, unlike |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 3772 | images, which always have to be compressed. So if you don't want the |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3773 | text compressed, set the compression type to PNG_TEXT_COMPRESSION_NONE. |
Glenn Randers-Pehrson | 228bd39 | 2000-04-23 23:14:02 -0500 | [diff] [blame] | 3774 | Because tEXt and zTXt chunks don't have a language field, if you |
| 3775 | specify PNG_TEXT_COMPRESSION_NONE or PNG_TEXT_COMPRESSION_zTXt |
| 3776 | any language code or translated keyword will not be written out. |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 3777 | |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 3778 | Until text gets around a few hundred bytes, it is not worth compressing it. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3779 | After the text has been written out to the file, the compression type |
| 3780 | is set to PNG_TEXT_COMPRESSION_NONE_WR or PNG_TEXT_COMPRESSION_zTXt_WR, |
| 3781 | so that it isn't written out again at the end (in case you are calling |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3782 | png_write_end() with the same struct). |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3783 | |
| 3784 | The keywords that are given in the PNG Specification are: |
| 3785 | |
| 3786 | Title Short (one line) title or |
| 3787 | caption for image |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3788 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3789 | Author Name of image's creator |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3790 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3791 | Description Description of image (possibly long) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3792 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3793 | Copyright Copyright notice |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3794 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3795 | Creation Time Time of original image creation |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 3796 | (usually RFC 1123 format, see below) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3797 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3798 | Software Software used to create the image |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3799 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3800 | Disclaimer Legal disclaimer |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3801 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3802 | Warning Warning of nature of content |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3803 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3804 | Source Device used to create the image |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 3805 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3806 | Comment Miscellaneous comment; conversion |
| 3807 | from other image format |
| 3808 | |
| 3809 | The keyword-text pairs work like this. Keywords should be short |
| 3810 | simple descriptions of what the comment is about. Some typical |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 3811 | keywords are found in the PNG specification, as is some recommendations |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3812 | on keywords. You can repeat keywords in a file. You can even write |
| 3813 | some text before the image and some after. For example, you may want |
| 3814 | to put a description of the image before the image, but leave the |
| 3815 | disclaimer until after, so viewers working over modem connections |
| 3816 | don't have to wait for the disclaimer to go over the modem before |
| 3817 | they start seeing the image. Finally, keywords should be full |
| 3818 | words, not abbreviations. Keywords and text are in the ISO 8859-1 |
| 3819 | (Latin-1) character set (a superset of regular ASCII) and can not |
| 3820 | contain NUL characters, and should not contain control or other |
| 3821 | unprintable characters. To make the comments widely readable, stick |
| 3822 | with basic ASCII, and avoid machine specific character set extensions |
| 3823 | like the IBM-PC character set. The keyword must be present, but |
| 3824 | you can leave off the text string on non-compressed pairs. |
| 3825 | Compressed pairs must have a text string, as only the text string |
| 3826 | is compressed anyway, so the compression would be meaningless. |
| 3827 | |
| 3828 | PNG supports modification time via the png_time structure. Two |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 3829 | conversion routines are provided, png_convert_from_time_t() for |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3830 | time_t and png_convert_from_struct_tm() for struct tm. The |
| 3831 | time_t routine uses gmtime(). You don't have to use either of |
| 3832 | these, but if you wish to fill in the png_time structure directly, |
| 3833 | you should provide the time in universal time (GMT) if possible |
| 3834 | instead of your local time. Note that the year number is the full |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 3835 | year (e.g. 1998, rather than 98 - PNG is year 2000 compliant!), and |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3836 | that months start with 1. |
| 3837 | |
| 3838 | If you want to store the time of the original image creation, you should |
| 3839 | use a plain tEXt chunk with the "Creation Time" keyword. This is |
| 3840 | necessary because the "creation time" of a PNG image is somewhat vague, |
| 3841 | depending on whether you mean the PNG file, the time the image was |
| 3842 | created in a non-PNG format, a still photo from which the image was |
| 3843 | scanned, or possibly the subject matter itself. In order to facilitate |
| 3844 | machine-readable dates, it is recommended that the "Creation Time" |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 3845 | tEXt chunk use RFC 1123 format dates (e.g. "22 May 1997 18:07:10 GMT"), |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3846 | although this isn't a requirement. Unlike the tIME chunk, the |
| 3847 | "Creation Time" tEXt chunk is not expected to be automatically changed |
| 3848 | by the software. To facilitate the use of RFC 1123 dates, a function |
Glenn Randers-Pehrson | f7a7bb0 | 2014-10-17 09:06:25 -0500 | [diff] [blame] | 3849 | png_convert_to_rfc1123_buffer(buffer, png_timep) is provided to |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 3850 | convert from PNG time to an RFC 1123 format string. The caller must provide |
| 3851 | a writeable buffer of at least 29 bytes. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3852 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3853 | .SS Writing unknown chunks |
| 3854 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 3855 | You can use the png_set_unknown_chunks function to queue up private chunks |
| 3856 | for writing. You give it a chunk name, location, raw data, and a size. You |
| 3857 | also must use png_set_keep_unknown_chunks() to ensure that libpng will |
| 3858 | handle them. That's all there is to it. The chunks will be written by the |
| 3859 | next following png_write_info_before_PLTE, png_write_info, or png_write_end |
| 3860 | function, depending upon the specified location. Any chunks previously |
| 3861 | read into the info structure's unknown-chunk list will also be written out |
| 3862 | in a sequence that satisfies the PNG specification's ordering rules. |
| 3863 | |
| 3864 | Here is an example of writing two private chunks, prVt and miNE: |
| 3865 | |
| 3866 | #ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED |
| 3867 | /* Set unknown chunk data */ |
| 3868 | png_unknown_chunk unk_chunk[2]; |
| 3869 | strcpy((char *) unk_chunk[0].name, "prVt"; |
| 3870 | unk_chunk[0].data = (unsigned char *) "PRIVATE DATA"; |
| 3871 | unk_chunk[0].size = strlen(unk_chunk[0].data)+1; |
| 3872 | unk_chunk[0].location = PNG_HAVE_IHDR; |
| 3873 | strcpy((char *) unk_chunk[1].name, "miNE"; |
| 3874 | unk_chunk[1].data = (unsigned char *) "MY CHUNK DATA"; |
| 3875 | unk_chunk[1].size = strlen(unk_chunk[0].data)+1; |
| 3876 | unk_chunk[1].location = PNG_AFTER_IDAT; |
| 3877 | png_set_unknown_chunks(write_ptr, write_info_ptr, |
| 3878 | unk_chunk, 2); |
| 3879 | /* Needed because miNE is not safe-to-copy */ |
| 3880 | png_set_keep_unknown_chunks(png, PNG_HANDLE_CHUNK_ALWAYS, |
| 3881 | (png_bytep) "miNE", 1); |
| 3882 | # if PNG_LIBPNG_VER < 10600 |
| 3883 | /* Deal with unknown chunk location bug in 1.5.x and earlier */ |
| 3884 | png_set_unknown_chunk_location(png, info, 0, PNG_HAVE_IHDR); |
| 3885 | png_set_unknown_chunk_location(png, info, 1, PNG_AFTER_IDAT); |
| 3886 | # endif |
| 3887 | # if PNG_LIBPNG_VER < 10500 |
| 3888 | /* PNG_AFTER_IDAT writes two copies of the chunk prior to libpng-1.5.0, |
| 3889 | * one before IDAT and another after IDAT, so don't use it; only use |
| 3890 | * PNG_HAVE_IHDR location. This call resets the location previously |
| 3891 | * set by assignment and png_set_unknown_chunk_location() for chunk 1. |
| 3892 | */ |
| 3893 | png_set_unknown_chunk_location(png, info, 1, PNG_HAVE_IHDR); |
| 3894 | # endif |
| 3895 | #endif |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 3896 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3897 | .SS The high-level write interface |
| 3898 | |
| 3899 | At this point there are two ways to proceed; through the high-level |
| 3900 | write interface, or through a sequence of low-level write operations. |
| 3901 | You can use the high-level interface if your image data is present |
Glenn Randers-Pehrson | 38e6e77 | 2000-04-09 19:06:13 -0500 | [diff] [blame] | 3902 | in the info structure. All defined output |
Glenn Randers-Pehrson | a77ef62 | 2000-02-18 13:48:52 -0600 | [diff] [blame] | 3903 | transformations are permitted, enabled by the following masks. |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3904 | |
| 3905 | PNG_TRANSFORM_IDENTITY No transformation |
| 3906 | PNG_TRANSFORM_PACKING Pack 1, 2 and 4-bit samples |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 3907 | PNG_TRANSFORM_PACKSWAP Change order of packed |
| 3908 | pixels to LSB first |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3909 | PNG_TRANSFORM_INVERT_MONO Invert monochrome images |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 3910 | PNG_TRANSFORM_SHIFT Normalize pixels to the |
| 3911 | sBIT depth |
| 3912 | PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA |
| 3913 | to BGRA |
| 3914 | PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA |
| 3915 | to AG |
| 3916 | PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity |
| 3917 | to transparency |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3918 | PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples |
Glenn Randers-Pehrson | 1eb14e9 | 2008-12-10 07:14:45 -0600 | [diff] [blame] | 3919 | PNG_TRANSFORM_STRIP_FILLER Strip out filler |
| 3920 | bytes (deprecated). |
| 3921 | PNG_TRANSFORM_STRIP_FILLER_BEFORE Strip out leading |
| 3922 | filler bytes |
| 3923 | PNG_TRANSFORM_STRIP_FILLER_AFTER Strip out trailing |
| 3924 | filler bytes |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3925 | |
Glenn Randers-Pehrson | 1ef65b6 | 2000-05-12 06:19:53 -0500 | [diff] [blame] | 3926 | If you have valid image data in the info structure (you can use |
| 3927 | png_set_rows() to put image data in the info structure), simply do this: |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3928 | |
| 3929 | png_write_png(png_ptr, info_ptr, png_transforms, NULL) |
| 3930 | |
Glenn Randers-Pehrson | ebd7f9a | 2006-10-19 09:37:56 -0500 | [diff] [blame] | 3931 | where png_transforms is an integer containing the bitwise OR of some set of |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3932 | transformation flags. This call is equivalent to png_write_info(), |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 3933 | followed the set of transformations indicated by the transform mask, |
| 3934 | then png_write_image(), and finally png_write_end(). |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3935 | |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 3936 | (The final parameter of this call is not yet used. Someday it might point |
| 3937 | to transformation parameters required by some future output transform.) |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3938 | |
Glenn Randers-Pehrson | a4981d4 | 2004-08-25 22:00:45 -0500 | [diff] [blame] | 3939 | You must use png_transforms and not call any png_set_transform() functions |
| 3940 | when you use png_write_png(). |
| 3941 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3942 | .SS The low-level write interface |
| 3943 | |
| 3944 | If you are going the low-level route instead, you are now ready to |
| 3945 | write all the file information up to the actual image data. You do |
| 3946 | this with a call to png_write_info(). |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3947 | |
| 3948 | png_write_info(png_ptr, info_ptr); |
| 3949 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3950 | Note that there is one transformation you may need to do before |
| 3951 | png_write_info(). In PNG files, the alpha channel in an image is the |
Glenn Randers-Pehrson | f210a05 | 2009-11-12 10:02:24 -0600 | [diff] [blame] | 3952 | level of opacity. If your data is supplied as a level of transparency, |
| 3953 | you can invert the alpha channel before you write it, so that 0 is |
| 3954 | fully transparent and 255 (in 8-bit or paletted images) or 65535 |
| 3955 | (in 16-bit images) is fully opaque, with |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 3956 | |
| 3957 | png_set_invert_alpha(png_ptr); |
| 3958 | |
| 3959 | This must appear before png_write_info() instead of later with the |
| 3960 | other transformations because in the case of paletted images the tRNS |
| 3961 | chunk data has to be inverted before the tRNS chunk is written. If |
| 3962 | your image is not a paletted image, the tRNS data (which in such cases |
| 3963 | represents a single color to be rendered as transparent) won't need to |
| 3964 | be changed, and you can safely do this transformation after your |
| 3965 | png_write_info() call. |
| 3966 | |
Glenn Randers-Pehrson | 5379b24 | 1999-11-27 10:22:33 -0600 | [diff] [blame] | 3967 | If you need to write a private chunk that you want to appear before |
| 3968 | the PLTE chunk when PLTE is present, you can write the PNG info in |
| 3969 | two steps, and insert code to write your own chunk between them: |
| 3970 | |
| 3971 | png_write_info_before_PLTE(png_ptr, info_ptr); |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 3972 | png_set_unknown_chunks(png_ptr, info_ptr, ...); |
Glenn Randers-Pehrson | 5379b24 | 1999-11-27 10:22:33 -0600 | [diff] [blame] | 3973 | png_write_info(png_ptr, info_ptr); |
| 3974 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3975 | After you've written the file information, you can set up the library |
| 3976 | to handle any special transformations of the image data. The various |
| 3977 | ways to transform the data will be described in the order that they |
| 3978 | should occur. This is important, as some of these change the color |
| 3979 | type and/or bit depth of the data, and some others only work on |
| 3980 | certain color types and bit depths. Even though each transformation |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 3981 | checks to see if it has data that it can do something with, you should |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3982 | make sure to only enable a transformation if it will be valid for the |
| 3983 | data. For example, don't swap red and blue on grayscale data. |
| 3984 | |
Glenn Randers-Pehrson | 896239b | 1998-04-21 15:03:57 -0500 | [diff] [blame] | 3985 | PNG files store RGB pixels packed into 3 or 6 bytes. This code tells |
Glenn Randers-Pehrson | 68ea243 | 2000-04-01 21:10:05 -0600 | [diff] [blame] | 3986 | the library to strip input data that has 4 or 8 bytes per pixel down |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 3987 | to 3 or 6 bytes (or strip 2 or 4-byte grayscale+filler data to 1 or 2 |
| 3988 | bytes per pixel). |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3989 | |
| 3990 | png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE); |
| 3991 | |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 3992 | where the 0 is unused, and the location is either PNG_FILLER_BEFORE or |
Glenn Randers-Pehrson | 228bd39 | 2000-04-23 23:14:02 -0500 | [diff] [blame] | 3993 | PNG_FILLER_AFTER, depending upon whether the filler byte in the pixel |
| 3994 | is stored XRGB or RGBX. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 3995 | |
| 3996 | PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as |
| 3997 | they can, resulting in, for example, 8 pixels per byte for 1 bit files. |
| 3998 | If the data is supplied at 1 pixel per byte, use this code, which will |
| 3999 | correctly pack the pixels into a single byte: |
| 4000 | |
| 4001 | png_set_packing(png_ptr); |
| 4002 | |
| 4003 | PNG files reduce possible bit depths to 1, 2, 4, 8, and 16. If your |
| 4004 | data is of another bit depth, you can write an sBIT chunk into the |
Glenn Randers-Pehrson | 228bd39 | 2000-04-23 23:14:02 -0500 | [diff] [blame] | 4005 | file so that decoders can recover the original data if desired. |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 4006 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4007 | /* Set the true bit depth of the image data */ |
| 4008 | if (color_type & PNG_COLOR_MASK_COLOR) |
| 4009 | { |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 4010 | sig_bit.red = true_bit_depth; |
| 4011 | sig_bit.green = true_bit_depth; |
| 4012 | sig_bit.blue = true_bit_depth; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4013 | } |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 4014 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4015 | else |
| 4016 | { |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 4017 | sig_bit.gray = true_bit_depth; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4018 | } |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 4019 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4020 | if (color_type & PNG_COLOR_MASK_ALPHA) |
| 4021 | { |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 4022 | sig_bit.alpha = true_bit_depth; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4023 | } |
| 4024 | |
| 4025 | png_set_sBIT(png_ptr, info_ptr, &sig_bit); |
| 4026 | |
| 4027 | If the data is stored in the row buffer in a bit depth other than |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 4028 | one supported by PNG (e.g. 3 bit data in the range 0-7 for a 4-bit PNG), |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4029 | this will scale the values to appear to be the correct bit depth as |
| 4030 | is required by PNG. |
| 4031 | |
| 4032 | png_set_shift(png_ptr, &sig_bit); |
| 4033 | |
Glenn Randers-Pehrson | 593fc04 | 2011-05-12 22:18:23 -0500 | [diff] [blame] | 4034 | PNG files store 16-bit pixels in network byte order (big-endian, |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4035 | ie. most significant bits first). This code would be used if they are |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 4036 | supplied the other way (little-endian, i.e. least significant bits |
| 4037 | first, the way PCs store them): |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4038 | |
| 4039 | if (bit_depth > 8) |
| 4040 | png_set_swap(png_ptr); |
| 4041 | |
| 4042 | If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you |
| 4043 | need to change the order the pixels are packed into bytes, you can use: |
| 4044 | |
| 4045 | if (bit_depth < 8) |
| 4046 | png_set_packswap(png_ptr); |
| 4047 | |
| 4048 | PNG files store 3 color pixels in red, green, blue order. This code |
| 4049 | would be used if they are supplied as blue, green, red: |
| 4050 | |
| 4051 | png_set_bgr(png_ptr); |
| 4052 | |
| 4053 | PNG files describe monochrome as black being zero and white being |
| 4054 | one. This code would be used if the pixels are supplied with this reversed |
| 4055 | (black being one and white being zero): |
| 4056 | |
| 4057 | png_set_invert_mono(png_ptr); |
| 4058 | |
Glenn Randers-Pehrson | 08a3343 | 1998-03-07 06:06:55 -0600 | [diff] [blame] | 4059 | Finally, you can write your own transformation function if none of |
| 4060 | the existing ones meets your needs. This is done by setting a callback |
| 4061 | with |
| 4062 | |
| 4063 | png_set_write_user_transform_fn(png_ptr, |
| 4064 | write_transform_fn); |
| 4065 | |
| 4066 | You must supply the function |
| 4067 | |
Glenn Randers-Pehrson | 9321567 | 2011-02-13 19:42:19 -0600 | [diff] [blame] | 4068 | void write_transform_fn(png_structp png_ptr, png_row_infop |
| 4069 | row_info, png_bytep data) |
Glenn Randers-Pehrson | 08a3343 | 1998-03-07 06:06:55 -0600 | [diff] [blame] | 4070 | |
| 4071 | See pngtest.c for a working example. Your function will be called |
John Bowler | f19abd6 | 2011-01-22 18:29:24 -0600 | [diff] [blame] | 4072 | before any of the other transformations are processed. If supported |
| 4073 | libpng also supplies an information routine that may be called from |
| 4074 | your callback: |
| 4075 | |
| 4076 | png_get_current_row_number(png_ptr); |
John Bowler | cd11345 | 2011-02-16 06:15:13 -0600 | [diff] [blame] | 4077 | png_get_current_pass_number(png_ptr); |
John Bowler | f19abd6 | 2011-01-22 18:29:24 -0600 | [diff] [blame] | 4078 | |
John Bowler | cd11345 | 2011-02-16 06:15:13 -0600 | [diff] [blame] | 4079 | This returns the current row passed to the transform. With interlaced |
| 4080 | images the value returned is the row in the input sub-image image. Use |
| 4081 | PNG_ROW_FROM_PASS_ROW(row, pass) and PNG_COL_FROM_PASS_COL(col, pass) to |
| 4082 | find the output pixel (x,y) given an interlaced sub-image pixel (row,col,pass). |
| 4083 | |
| 4084 | The discussion of interlace handling above contains more information on how to |
| 4085 | use these values. |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 4086 | |
| 4087 | You can also set up a pointer to a user structure for use by your |
| 4088 | callback function. |
| 4089 | |
| 4090 | png_set_user_transform_info(png_ptr, user_ptr, 0, 0); |
| 4091 | |
| 4092 | The user_channels and user_depth parameters of this function are ignored |
| 4093 | when writing; you can set them to zero as shown. |
| 4094 | |
Glenn Randers-Pehrson | 228bd39 | 2000-04-23 23:14:02 -0500 | [diff] [blame] | 4095 | You can retrieve the pointer via the function png_get_user_transform_ptr(). |
| 4096 | For example: |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 4097 | |
| 4098 | voidp write_user_transform_ptr = |
| 4099 | png_get_user_transform_ptr(png_ptr); |
Glenn Randers-Pehrson | 08a3343 | 1998-03-07 06:06:55 -0600 | [diff] [blame] | 4100 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4101 | It is possible to have libpng flush any pending output, either manually, |
| 4102 | or automatically after a certain number of lines have been written. To |
| 4103 | flush the output stream a single time call: |
| 4104 | |
| 4105 | png_write_flush(png_ptr); |
| 4106 | |
| 4107 | and to have libpng flush the output stream periodically after a certain |
| 4108 | number of scanlines have been written, call: |
| 4109 | |
| 4110 | png_set_flush(png_ptr, nrows); |
| 4111 | |
| 4112 | Note that the distance between rows is from the last time png_write_flush() |
| 4113 | was called, or the first row of the image if it has never been called. |
| 4114 | So if you write 50 lines, and then png_set_flush 25, it will flush the |
| 4115 | output on the next scanline, and every 25 lines thereafter, unless |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 4116 | png_write_flush() is called before 25 more lines have been written. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4117 | If nrows is too small (less than about 10 lines for a 640 pixel wide |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 4118 | RGB image) the image compression may decrease noticeably (although this |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4119 | may be acceptable for real-time applications). Infrequent flushing will |
| 4120 | only degrade the compression performance by a few percent over images |
| 4121 | that do not use flushing. |
| 4122 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 4123 | .SS Writing the image data |
| 4124 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4125 | That's it for the transformations. Now you can write the image data. |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 4126 | The simplest way to do this is in one function call. If you have the |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4127 | whole image in memory, you can just call png_write_image() and libpng |
| 4128 | will write the image. You will need to pass in an array of pointers to |
| 4129 | each row. This function automatically handles interlacing, so you don't |
| 4130 | need to call png_set_interlace_handling() or call this function multiple |
| 4131 | times, or any of that other stuff necessary with png_write_rows(). |
| 4132 | |
| 4133 | png_write_image(png_ptr, row_pointers); |
| 4134 | |
| 4135 | where row_pointers is: |
| 4136 | |
Glenn Randers-Pehrson | 896239b | 1998-04-21 15:03:57 -0500 | [diff] [blame] | 4137 | png_byte *row_pointers[height]; |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4138 | |
| 4139 | You can point to void or char or whatever you use for pixels. |
| 4140 | |
Glenn Randers-Pehrson | 896239b | 1998-04-21 15:03:57 -0500 | [diff] [blame] | 4141 | If you don't want to write the whole image at once, you can |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4142 | use png_write_rows() instead. If the file is not interlaced, |
| 4143 | this is simple: |
| 4144 | |
| 4145 | png_write_rows(png_ptr, row_pointers, |
| 4146 | number_of_rows); |
| 4147 | |
| 4148 | row_pointers is the same as in the png_write_image() call. |
| 4149 | |
| 4150 | If you are just writing one row at a time, you can do this with |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 4151 | a single row_pointer instead of an array of row_pointers: |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4152 | |
| 4153 | png_bytep row_pointer = row; |
| 4154 | |
Glenn Randers-Pehrson | 520a764 | 2000-03-21 05:13:06 -0600 | [diff] [blame] | 4155 | png_write_row(png_ptr, row_pointer); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4156 | |
Glenn Randers-Pehrson | f210a05 | 2009-11-12 10:02:24 -0600 | [diff] [blame] | 4157 | When the file is interlaced, things can get a good deal more complicated. |
| 4158 | The only currently (as of the PNG Specification version 1.2, dated July |
| 4159 | 1999) defined interlacing scheme for PNG files is the "Adam7" interlace |
| 4160 | scheme, that breaks down an image into seven smaller images of varying |
| 4161 | size. libpng will build these images for you, or you can do them |
| 4162 | yourself. If you want to build them yourself, see the PNG specification |
| 4163 | for details of which pixels to write when. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4164 | |
| 4165 | If you don't want libpng to handle the interlacing details, just |
| 4166 | use png_set_interlace_handling() and call png_write_rows() the |
Glenn Randers-Pehrson | 6e97410 | 2010-12-19 16:44:22 -0600 | [diff] [blame] | 4167 | correct number of times to write all the sub-images |
| 4168 | (png_set_interlace_handling() returns the number of sub-images.) |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4169 | |
| 4170 | If you want libpng to build the sub-images, call this before you start |
| 4171 | writing any rows: |
| 4172 | |
Glenn Randers-Pehrson | 6e97410 | 2010-12-19 16:44:22 -0600 | [diff] [blame] | 4173 | number_of_passes = png_set_interlace_handling(png_ptr); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4174 | |
Glenn Randers-Pehrson | f210a05 | 2009-11-12 10:02:24 -0600 | [diff] [blame] | 4175 | This will return the number of passes needed. Currently, this is seven, |
| 4176 | but may change if another interlace type is added. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4177 | |
| 4178 | Then write the complete image number_of_passes times. |
| 4179 | |
Glenn Randers-Pehrson | 6e97410 | 2010-12-19 16:44:22 -0600 | [diff] [blame] | 4180 | png_write_rows(png_ptr, row_pointers, number_of_rows); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4181 | |
Glenn Randers-Pehrson | 6e97410 | 2010-12-19 16:44:22 -0600 | [diff] [blame] | 4182 | Think carefully before you write an interlaced image. Typically code that |
| 4183 | reads such images reads all the image data into memory, uncompressed, before |
| 4184 | doing any processing. Only code that can display an image on the fly can |
| 4185 | take advantage of the interlacing and even then the image has to be exactly |
| 4186 | the correct size for the output device, because scaling an image requires |
| 4187 | adjacent pixels and these are not available until all the passes have been |
| 4188 | read. |
| 4189 | |
| 4190 | If you do write an interlaced image you will hardly ever need to handle |
| 4191 | the interlacing yourself. Call png_set_interlace_handling() and use the |
| 4192 | approach described above. |
| 4193 | |
| 4194 | The only time it is conceivable that you will really need to write an |
| 4195 | interlaced image pass-by-pass is when you have read one pass by pass and |
| 4196 | made some pixel-by-pixel transformation to it, as described in the read |
| 4197 | code above. In this case use the PNG_PASS_ROWS and PNG_PASS_COLS macros |
| 4198 | to determine the size of each sub-image in turn and simply write the rows |
| 4199 | you obtained from the read code. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4200 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 4201 | .SS Finishing a sequential write |
| 4202 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4203 | After you are finished writing the image, you should finish writing |
| 4204 | the file. If you are interested in writing comments or time, you should |
| 4205 | pass an appropriately filled png_info pointer. If you are not interested, |
| 4206 | you can pass NULL. |
| 4207 | |
| 4208 | png_write_end(png_ptr, info_ptr); |
| 4209 | |
| 4210 | When you are done, you can free all memory used by libpng like this: |
| 4211 | |
| 4212 | png_destroy_write_struct(&png_ptr, &info_ptr); |
| 4213 | |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 4214 | It is also possible to individually free the info_ptr members that |
Glenn Randers-Pehrson | fc4a143 | 2000-05-17 17:39:34 -0500 | [diff] [blame] | 4215 | point to libpng-allocated storage with the following function: |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 4216 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 4217 | png_free_data(png_ptr, info_ptr, mask, seq) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 4218 | |
Glenn Randers-Pehrson | 1ef65b6 | 2000-05-12 06:19:53 -0500 | [diff] [blame] | 4219 | mask - identifies data to be freed, a mask |
Glenn Randers-Pehrson | ebd7f9a | 2006-10-19 09:37:56 -0500 | [diff] [blame] | 4220 | containing the bitwise OR of one or |
Glenn Randers-Pehrson | 1ef65b6 | 2000-05-12 06:19:53 -0500 | [diff] [blame] | 4221 | more of |
| 4222 | PNG_FREE_PLTE, PNG_FREE_TRNS, |
| 4223 | PNG_FREE_HIST, PNG_FREE_ICCP, |
| 4224 | PNG_FREE_PCAL, PNG_FREE_ROWS, |
| 4225 | PNG_FREE_SCAL, PNG_FREE_SPLT, |
| 4226 | PNG_FREE_TEXT, PNG_FREE_UNKN, |
| 4227 | or simply PNG_FREE_ALL |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 4228 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 4229 | seq - sequence number of item to be freed |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 4230 | (\-1 for all items) |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 4231 | |
Glenn Randers-Pehrson | fc4a143 | 2000-05-17 17:39:34 -0500 | [diff] [blame] | 4232 | This function may be safely called when the relevant storage has |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 4233 | already been freed, or has not yet been allocated, or was allocated |
Glenn Randers-Pehrson | f210a05 | 2009-11-12 10:02:24 -0600 | [diff] [blame] | 4234 | by the user and not by libpng, and will in those cases do nothing. |
| 4235 | The "seq" parameter is ignored if only one item of the selected data |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 4236 | type, such as PLTE, is allowed. If "seq" is not \-1, and multiple items |
Glenn Randers-Pehrson | f210a05 | 2009-11-12 10:02:24 -0600 | [diff] [blame] | 4237 | are allowed for the data type identified in the mask, such as text or |
| 4238 | sPLT, only the n'th item in the structure is freed, where n is "seq". |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 4239 | |
Glenn Randers-Pehrson | f210a05 | 2009-11-12 10:02:24 -0600 | [diff] [blame] | 4240 | If you allocated data such as a palette that you passed in to libpng |
| 4241 | with png_set_*, you must not free it until just before the call to |
Glenn Randers-Pehrson | a77ef62 | 2000-02-18 13:48:52 -0600 | [diff] [blame] | 4242 | png_destroy_write_struct(). |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4243 | |
Glenn Randers-Pehrson | 38e6e77 | 2000-04-09 19:06:13 -0500 | [diff] [blame] | 4244 | The default behavior is only to free data that was allocated internally |
| 4245 | by libpng. This can be changed, so that libpng will not free the data, |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 4246 | or so that it will free data that was allocated by the user with png_malloc() |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4247 | or png_calloc() and passed in via a png_set_*() function, with |
Glenn Randers-Pehrson | 38e6e77 | 2000-04-09 19:06:13 -0500 | [diff] [blame] | 4248 | |
| 4249 | png_data_freer(png_ptr, info_ptr, freer, mask) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 4250 | |
Glenn Randers-Pehrson | 1ef65b6 | 2000-05-12 06:19:53 -0500 | [diff] [blame] | 4251 | freer - one of |
| 4252 | PNG_DESTROY_WILL_FREE_DATA |
| 4253 | PNG_SET_WILL_FREE_DATA |
| 4254 | PNG_USER_WILL_FREE_DATA |
Glenn Randers-Pehrson | 38e6e77 | 2000-04-09 19:06:13 -0500 | [diff] [blame] | 4255 | |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 4256 | mask - which data elements are affected |
| 4257 | same choices as in png_free_data() |
| 4258 | |
Glenn Randers-Pehrson | 38e6e77 | 2000-04-09 19:06:13 -0500 | [diff] [blame] | 4259 | For example, to transfer responsibility for some data from a read structure |
| 4260 | to a write structure, you could use |
| 4261 | |
| 4262 | png_data_freer(read_ptr, read_info_ptr, |
| 4263 | PNG_USER_WILL_FREE_DATA, |
| 4264 | PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 4265 | |
Glenn Randers-Pehrson | 38e6e77 | 2000-04-09 19:06:13 -0500 | [diff] [blame] | 4266 | png_data_freer(write_ptr, write_info_ptr, |
| 4267 | PNG_DESTROY_WILL_FREE_DATA, |
| 4268 | PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST) |
| 4269 | |
Glenn Randers-Pehrson | 228bd39 | 2000-04-23 23:14:02 -0500 | [diff] [blame] | 4270 | thereby briefly reassigning responsibility for freeing to the user but |
Glenn Randers-Pehrson | 38e6e77 | 2000-04-09 19:06:13 -0500 | [diff] [blame] | 4271 | immediately afterwards reassigning it once more to the write_destroy |
| 4272 | function. Having done this, it would then be safe to destroy the read |
| 4273 | structure and continue to use the PLTE, tRNS, and hIST data in the write |
| 4274 | structure. |
| 4275 | |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 4276 | This function only affects data that has already been allocated. |
| 4277 | You can call this function before calling after the png_set_*() functions |
| 4278 | to control whether the user or png_destroy_*() is supposed to free the data. |
| 4279 | When the user assumes responsibility for libpng-allocated data, the |
Glenn Randers-Pehrson | 1ef65b6 | 2000-05-12 06:19:53 -0500 | [diff] [blame] | 4280 | application must use |
| 4281 | png_free() to free it, and when the user transfers responsibility to libpng |
| 4282 | for data that the user has allocated, the user must have used png_malloc() |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4283 | or png_calloc() to allocate it. |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 4284 | |
Glenn Randers-Pehrson | 1ef65b6 | 2000-05-12 06:19:53 -0500 | [diff] [blame] | 4285 | If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword |
| 4286 | separately, do not transfer responsibility for freeing text_ptr to libpng, |
| 4287 | because when libpng fills a png_text structure it combines these members with |
| 4288 | the key member, and png_free_data() will free only text_ptr.key. Similarly, |
| 4289 | if you transfer responsibility for free'ing text_ptr from libpng to your |
| 4290 | application, your application must not separately free those members. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4291 | For a more compact example of writing a PNG image, see the file example.c. |
| 4292 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4293 | .SH V. Simplified API |
| 4294 | |
| 4295 | The simplified API, which became available in libpng-1.6.0, hides the details |
| 4296 | of both libpng and the PNG file format itself. |
| 4297 | It allows PNG files to be read into a very limited number of |
| 4298 | in-memory bitmap formats or to be written from the same formats. If these |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 4299 | formats do not accommodate your needs then you can, and should, use the more |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4300 | sophisticated APIs above - these support a wide variety of in-memory formats |
| 4301 | and a wide variety of sophisticated transformations to those formats as well |
Unknown | f23b41d | 2017-11-03 00:52:06 -0400 | [diff] [blame] | 4302 | as a wide variety of APIs to manipulate ancillary information. |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4303 | |
| 4304 | To read a PNG file using the simplified API: |
| 4305 | |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4306 | 1) Declare a 'png_image' structure (see below) on the stack, set the |
| 4307 | version field to PNG_IMAGE_VERSION and the 'opaque' pointer to NULL |
| 4308 | (this is REQUIRED, your program may crash if you don't do it.) |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4309 | |
| 4310 | 2) Call the appropriate png_image_begin_read... function. |
| 4311 | |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4312 | 3) Set the png_image 'format' member to the required sample format. |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4313 | |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4314 | 4) Allocate a buffer for the image and, if required, the color-map. |
| 4315 | |
| 4316 | 5) Call png_image_finish_read to read the image and, if required, the |
| 4317 | color-map into your buffers. |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4318 | |
| 4319 | There are no restrictions on the format of the PNG input itself; all valid |
| 4320 | color types, bit depths, and interlace methods are acceptable, and the |
| 4321 | input image is transformed as necessary to the requested in-memory format |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4322 | during the png_image_finish_read() step. The only caveat is that if you |
| 4323 | request a color-mapped image from a PNG that is full-color or makes |
| 4324 | complex use of an alpha channel the transformation is extremely lossy and the |
| 4325 | result may look terrible. |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4326 | |
| 4327 | To write a PNG file using the simplified API: |
| 4328 | |
| 4329 | 1) Declare a 'png_image' structure on the stack and memset() |
| 4330 | it to all zero. |
| 4331 | |
| 4332 | 2) Initialize the members of the structure that describe the |
| 4333 | image, setting the 'format' member to the format of the |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4334 | image samples. |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4335 | |
| 4336 | 3) Call the appropriate png_image_write... function with a |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4337 | pointer to the image and, if necessary, the color-map to write |
| 4338 | the PNG data. |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4339 | |
| 4340 | png_image is a structure that describes the in-memory format of an image |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4341 | when it is being read or defines the in-memory format of an image that you |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4342 | need to write. The "png_image" structure contains the following members: |
| 4343 | |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4344 | png_controlp opaque Initialize to NULL, free with png_image_free |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4345 | png_uint_32 version Set to PNG_IMAGE_VERSION |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4346 | png_uint_32 width Image width in pixels (columns) |
| 4347 | png_uint_32 height Image height in pixels (rows) |
| 4348 | png_uint_32 format Image format as defined below |
| 4349 | png_uint_32 flags A bit mask containing informational flags |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4350 | png_uint_32 colormap_entries; Number of entries in the color-map |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4351 | png_uint_32 warning_or_error; |
| 4352 | char message[64]; |
| 4353 | |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4354 | In the event of an error or warning the "warning_or_error" |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4355 | field will be set to a non-zero value and the 'message' field will contain |
| 4356 | a '\0' terminated string with the libpng error or warning message. If both |
| 4357 | warnings and an error were encountered, only the error is recorded. If there |
| 4358 | are multiple warnings, only the first one is recorded. |
| 4359 | |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4360 | The upper 30 bits of the "warning_or_error" value are reserved; the low two |
| 4361 | bits contain a two bit code such that a value more than 1 indicates a failure |
| 4362 | in the API just called: |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4363 | |
| 4364 | 0 - no warning or error |
| 4365 | 1 - warning |
| 4366 | 2 - error |
| 4367 | 3 - error preceded by warning |
| 4368 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4369 | The pixels (samples) of the image have one to four channels whose components |
| 4370 | have original values in the range 0 to 1.0: |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4371 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4372 | 1: A single gray or luminance channel (G). |
| 4373 | 2: A gray/luminance channel and an alpha channel (GA). |
| 4374 | 3: Three red, green, blue color channels (RGB). |
| 4375 | 4: Three color channels and an alpha channel (RGBA). |
| 4376 | |
| 4377 | The channels are encoded in one of two ways: |
| 4378 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4379 | a) As a small integer, value 0..255, contained in a single byte. For the |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4380 | alpha channel the original value is simply value/255. For the color or |
| 4381 | luminance channels the value is encoded according to the sRGB specification |
| 4382 | and matches the 8-bit format expected by typical display devices. |
| 4383 | |
| 4384 | The color/gray channels are not scaled (pre-multiplied) by the alpha |
| 4385 | channel and are suitable for passing to color management software. |
| 4386 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 4387 | b) As a value in the range 0..65535, contained in a 2-byte integer, in |
| 4388 | the native byte order of the platform on which the application is running. |
| 4389 | All channels can be converted to the original value by dividing by 65535; all |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4390 | channels are linear. Color channels use the RGB encoding (RGB end-points) of |
| 4391 | the sRGB specification. This encoding is identified by the |
| 4392 | PNG_FORMAT_FLAG_LINEAR flag below. |
| 4393 | |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4394 | When the simplified API needs to convert between sRGB and linear colorspaces, |
| 4395 | the actual sRGB transfer curve defined in the sRGB specification (see the |
Glenn Randers-Pehrson | 64f8110 | 2017-04-03 15:25:40 -0500 | [diff] [blame] | 4396 | article at https://en.wikipedia.org/wiki/SRGB) is used, not the gamma=1/2.2 |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4397 | approximation used elsewhere in libpng. |
| 4398 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4399 | When an alpha channel is present it is expected to denote pixel coverage |
| 4400 | of the color or luminance channels and is returned as an associated alpha |
| 4401 | channel: the color/gray channels are scaled (pre-multiplied) by the alpha |
| 4402 | value. |
| 4403 | |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4404 | The samples are either contained directly in the image data, between 1 and 8 |
| 4405 | bytes per pixel according to the encoding, or are held in a color-map indexed |
| 4406 | by bytes in the image data. In the case of a color-map the color-map entries |
| 4407 | are individual samples, encoded as above, and the image data has one byte per |
| 4408 | pixel to select the relevant sample from the color-map. |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4409 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4410 | PNG_FORMAT_* |
| 4411 | |
| 4412 | The #defines to be used in png_image::format. Each #define identifies a |
| 4413 | particular layout of channel data and, if present, alpha values. There are |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4414 | separate defines for each of the two component encodings. |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4415 | |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4416 | A format is built up using single bit flag values. All combinations are |
| 4417 | valid. Formats can be built up from the flag values or you can use one of |
| 4418 | the predefined values below. When testing formats always use the FORMAT_FLAG |
| 4419 | macros to test for individual features - future versions of the library may |
| 4420 | add new flags. |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4421 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4422 | When reading or writing color-mapped images the format should be set to the |
| 4423 | format of the entries in the color-map then png_image_{read,write}_colormap |
| 4424 | called to read or write the color-map and set the format correctly for the |
| 4425 | image data. Do not set the PNG_FORMAT_FLAG_COLORMAP bit directly! |
| 4426 | |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4427 | NOTE: libpng can be built with particular features disabled. If you see |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4428 | compiler errors because the definition of one of the following flags has been |
| 4429 | compiled out it is because libpng does not have the required support. It is |
| 4430 | possible, however, for the libpng configuration to enable the format on just |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4431 | read or just write; in that case you may see an error at run time. |
| 4432 | You can guard against this by checking for the definition of the |
| 4433 | appropriate "_SUPPORTED" macro, one of: |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4434 | |
| 4435 | PNG_SIMPLIFIED_{READ,WRITE}_{BGR,AFIRST}_SUPPORTED |
| 4436 | |
Glenn Randers-Pehrson | 262c396 | 2015-07-25 08:30:12 -0500 | [diff] [blame] | 4437 | PNG_FORMAT_FLAG_ALPHA format with an alpha channel |
| 4438 | PNG_FORMAT_FLAG_COLOR color format: otherwise grayscale |
| 4439 | PNG_FORMAT_FLAG_LINEAR 2-byte channels else 1-byte |
| 4440 | PNG_FORMAT_FLAG_COLORMAP image data is color-mapped |
| 4441 | PNG_FORMAT_FLAG_BGR BGR colors, else order is RGB |
| 4442 | PNG_FORMAT_FLAG_AFIRST alpha channel comes first |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4443 | |
| 4444 | Supported formats are as follows. Future versions of libpng may support more |
| 4445 | formats; for compatibility with older versions simply check if the format |
| 4446 | macro is defined using #ifdef. These defines describe the in-memory layout |
| 4447 | of the components of the pixels of the image. |
| 4448 | |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4449 | First the single byte (sRGB) formats: |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4450 | |
Glenn Randers-Pehrson | 262c396 | 2015-07-25 08:30:12 -0500 | [diff] [blame] | 4451 | PNG_FORMAT_GRAY |
| 4452 | PNG_FORMAT_GA |
| 4453 | PNG_FORMAT_AG |
| 4454 | PNG_FORMAT_RGB |
| 4455 | PNG_FORMAT_BGR |
| 4456 | PNG_FORMAT_RGBA |
| 4457 | PNG_FORMAT_ARGB |
| 4458 | PNG_FORMAT_BGRA |
| 4459 | PNG_FORMAT_ABGR |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4460 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4461 | Then the linear 2-byte formats. When naming these "Y" is used to |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4462 | indicate a luminance (gray) channel. The component order within the pixel |
| 4463 | is always the same - there is no provision for swapping the order of the |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 4464 | components in the linear format. The components are 16-bit integers in |
| 4465 | the native byte order for your platform, and there is no provision for |
| 4466 | swapping the bytes to a different endian condition. |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4467 | |
Glenn Randers-Pehrson | 262c396 | 2015-07-25 08:30:12 -0500 | [diff] [blame] | 4468 | PNG_FORMAT_LINEAR_Y |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4469 | PNG_FORMAT_LINEAR_Y_ALPHA |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4470 | PNG_FORMAT_LINEAR_RGB |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4471 | PNG_FORMAT_LINEAR_RGB_ALPHA |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4472 | |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4473 | With color-mapped formats the image data is one byte for each pixel. The byte |
| 4474 | is an index into the color-map which is formatted as above. To obtain a |
| 4475 | color-mapped format it is sufficient just to add the PNG_FOMAT_FLAG_COLORMAP |
| 4476 | to one of the above definitions, or you can use one of the definitions below. |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4477 | |
Glenn Randers-Pehrson | 262c396 | 2015-07-25 08:30:12 -0500 | [diff] [blame] | 4478 | PNG_FORMAT_RGB_COLORMAP |
| 4479 | PNG_FORMAT_BGR_COLORMAP |
| 4480 | PNG_FORMAT_RGBA_COLORMAP |
| 4481 | PNG_FORMAT_ARGB_COLORMAP |
| 4482 | PNG_FORMAT_BGRA_COLORMAP |
| 4483 | PNG_FORMAT_ABGR_COLORMAP |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4484 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4485 | PNG_IMAGE macros |
| 4486 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4487 | These are convenience macros to derive information from a png_image |
| 4488 | structure. The PNG_IMAGE_SAMPLE_ macros return values appropriate to the |
| 4489 | actual image sample values - either the entries in the color-map or the |
| 4490 | pixels in the image. The PNG_IMAGE_PIXEL_ macros return corresponding values |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4491 | for the pixels and will always return 1 for color-mapped formats. The |
| 4492 | remaining macros return information about the rows in the image and the |
| 4493 | complete image. |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4494 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4495 | NOTE: All the macros that take a png_image::format parameter are compile time |
| 4496 | constants if the format parameter is, itself, a constant. Therefore these |
| 4497 | macros can be used in array declarations and case labels where required. |
| 4498 | Similarly the macros are also pre-processor constants (sizeof is not used) so |
| 4499 | they can be used in #if tests. |
| 4500 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4501 | PNG_IMAGE_SAMPLE_CHANNELS(fmt) |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4502 | Returns the total number of channels in a given format: 1..4 |
| 4503 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4504 | PNG_IMAGE_SAMPLE_COMPONENT_SIZE(fmt) |
| 4505 | Returns the size in bytes of a single component of a pixel or color-map |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4506 | entry (as appropriate) in the image: 1 or 2. |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4507 | |
| 4508 | PNG_IMAGE_SAMPLE_SIZE(fmt) |
| 4509 | This is the size of the sample data for one sample. If the image is |
| 4510 | color-mapped it is the size of one color-map entry (and image pixels are |
| 4511 | one byte in size), otherwise it is the size of one image pixel. |
| 4512 | |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4513 | PNG_IMAGE_MAXIMUM_COLORMAP_COMPONENTS(fmt) |
| 4514 | The maximum size of the color-map required by the format expressed in a |
| 4515 | count of components. This can be used to compile-time allocate a |
| 4516 | color-map: |
| 4517 | |
| 4518 | png_uint_16 colormap[PNG_IMAGE_MAXIMUM_COLORMAP_COMPONENTS(linear_fmt)]; |
| 4519 | |
| 4520 | png_byte colormap[PNG_IMAGE_MAXIMUM_COLORMAP_COMPONENTS(sRGB_fmt)]; |
| 4521 | |
| 4522 | Alternatively use the PNG_IMAGE_COLORMAP_SIZE macro below to use the |
| 4523 | information from one of the png_image_begin_read_ APIs and dynamically |
| 4524 | allocate the required memory. |
| 4525 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4526 | PNG_IMAGE_COLORMAP_SIZE(fmt) |
| 4527 | The size of the color-map required by the format; this is the size of the |
Glenn Randers-Pehrson | 262c396 | 2015-07-25 08:30:12 -0500 | [diff] [blame] | 4528 | color-map buffer passed to the png_image_{read,write}_colormap APIs. It is |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4529 | a fixed number determined by the format so can easily be allocated on the |
| 4530 | stack if necessary. |
| 4531 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4532 | Corresponding information about the pixels |
| 4533 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4534 | PNG_IMAGE_PIXEL_CHANNELS(fmt) |
| 4535 | The number of separate channels (components) in a pixel; 1 for a |
| 4536 | color-mapped image. |
| 4537 | |
| 4538 | PNG_IMAGE_PIXEL_COMPONENT_SIZE(fmt)\ |
| 4539 | The size, in bytes, of each component in a pixel; 1 for a color-mapped |
| 4540 | image. |
John Bowler | 6f237b6 | 2012-03-02 13:13:15 -0600 | [diff] [blame] | 4541 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4542 | PNG_IMAGE_PIXEL_SIZE(fmt) |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4543 | The size, in bytes, of a complete pixel; 1 for a color-mapped image. |
| 4544 | |
| 4545 | Information about the whole row, or whole image |
| 4546 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4547 | PNG_IMAGE_ROW_STRIDE(image) |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4548 | Returns the total number of components in a single row of the image; this |
| 4549 | is the minimum 'row stride', the minimum count of components between each |
| 4550 | row. For a color-mapped image this is the minimum number of bytes in a |
| 4551 | row. |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4552 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 4553 | If you need the stride measured in bytes, row_stride_bytes is |
| 4554 | PNG_IMAGE_ROW_STRIDE(image) * PNG_IMAGE_PIXEL_COMPONENT_SIZE(fmt) |
| 4555 | plus any padding bytes that your application might need, for example |
| 4556 | to start the next row on a 4-byte boundary. |
| 4557 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4558 | PNG_IMAGE_BUFFER_SIZE(image, row_stride) |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4559 | Return the size, in bytes, of an image buffer given a png_image and a row |
| 4560 | stride - the number of components to leave space for in each row. |
| 4561 | |
| 4562 | PNG_IMAGE_SIZE(image) |
| 4563 | Return the size, in bytes, of the image in memory given just a png_image; |
| 4564 | the row stride is the minimum stride required for the image. |
| 4565 | |
| 4566 | PNG_IMAGE_COLORMAP_SIZE(image) |
| 4567 | Return the size, in bytes, of the color-map of this image. If the image |
| 4568 | format is not a color-map format this will return a size sufficient for |
| 4569 | 256 entries in the given format; check PNG_FORMAT_FLAG_COLORMAP if |
| 4570 | you don't want to allocate a color-map in this case. |
| 4571 | |
| 4572 | PNG_IMAGE_FLAG_* |
| 4573 | |
| 4574 | Flags containing additional information about the image are held in |
| 4575 | the 'flags' field of png_image. |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4576 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4577 | PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB == 0x01 |
luz.paz | a294c1b | 2018-06-05 00:39:11 -0400 | [diff] [blame] | 4578 | This indicates that the RGB values of the in-memory bitmap do not |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4579 | correspond to the red, green and blue end-points defined by sRGB. |
John Bowler | 6f237b6 | 2012-03-02 13:13:15 -0600 | [diff] [blame] | 4580 | |
Glenn Randers-Pehrson | e10b7e7 | 2015-07-25 08:01:34 -0500 | [diff] [blame] | 4581 | PNG_IMAGE_FLAG_FAST == 0x02 |
| 4582 | On write emphasise speed over compression; the resultant PNG file will be |
| 4583 | larger but will be produced significantly faster, particular for large |
| 4584 | images. Do not use this option for images which will be distributed, only |
| 4585 | used it when producing intermediate files that will be read back in |
| 4586 | repeatedly. For a typical 24-bit image the option will double the read |
| 4587 | speed at the cost of increasing the image size by 25%, however for many |
| 4588 | more compressible images the PNG file can be 10 times larger with only a |
| 4589 | slight speed gain. |
| 4590 | |
| 4591 | PNG_IMAGE_FLAG_16BIT_sRGB == 0x04 |
| 4592 | On read if the image is a 16-bit per component image and there is no gAMA |
| 4593 | or sRGB chunk assume that the components are sRGB encoded. Notice that |
| 4594 | images output by the simplified API always have gamma information; setting |
| 4595 | this flag only affects the interpretation of 16-bit images from an |
| 4596 | external source. It is recommended that the application expose this flag |
| 4597 | to the user; the user can normally easily recognize the difference between |
| 4598 | linear and sRGB encoding. This flag has no effect on write - the data |
| 4599 | passed to the write APIs must have the correct encoding (as defined |
| 4600 | above.) |
| 4601 | |
| 4602 | If the flag is not set (the default) input 16-bit per component data is |
| 4603 | assumed to be linear. |
| 4604 | |
| 4605 | NOTE: the flag can only be set after the png_image_begin_read_ call, |
| 4606 | because that call initializes the 'flags' field. |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4607 | |
| 4608 | READ APIs |
| 4609 | |
| 4610 | The png_image passed to the read APIs must have been initialized by setting |
| 4611 | the png_controlp field 'opaque' to NULL (or, better, memset the whole thing.) |
| 4612 | |
| 4613 | int png_image_begin_read_from_file( png_imagep image, |
| 4614 | const char *file_name) |
| 4615 | |
| 4616 | The named file is opened for read and the image header |
| 4617 | is filled in from the PNG header in the file. |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4618 | |
| 4619 | int png_image_begin_read_from_stdio (png_imagep image, |
| 4620 | FILE* file) |
| 4621 | |
| 4622 | The PNG header is read from the stdio FILE object. |
| 4623 | |
| 4624 | int png_image_begin_read_from_memory(png_imagep image, |
Cosmin Truta | a74aa9a | 2018-06-17 22:37:44 -0400 | [diff] [blame] | 4625 | png_const_voidp memory, size_t size) |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4626 | |
| 4627 | The PNG header is read from the given memory buffer. |
| 4628 | |
| 4629 | int png_image_finish_read(png_imagep image, |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4630 | png_colorp background, void *buffer, |
| 4631 | png_int_32 row_stride, void *colormap)); |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4632 | |
| 4633 | Finish reading the image into the supplied buffer and |
| 4634 | clean up the png_image structure. |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4635 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4636 | row_stride is the step, in png_byte or png_uint_16 units |
| 4637 | as appropriate, between adjacent rows. A positive stride |
| 4638 | indicates that the top-most row is first in the buffer - |
| 4639 | the normal top-down arrangement. A negative stride |
| 4640 | indicates that the bottom-most row is first in the buffer. |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4641 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4642 | background need only be supplied if an alpha channel must |
| 4643 | be removed from a png_byte format and the removal is to be |
| 4644 | done by compositing on a solid color; otherwise it may be |
| 4645 | NULL and any composition will be done directly onto the |
| 4646 | buffer. The value is an sRGB color to use for the |
| 4647 | background, for grayscale output the green channel is used. |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4648 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4649 | For linear output removing the alpha channel is always done |
| 4650 | by compositing on black. |
| 4651 | |
| 4652 | void png_image_free(png_imagep image) |
| 4653 | |
| 4654 | Free any data allocated by libpng in image->opaque, |
| 4655 | setting the pointer to NULL. May be called at any time |
| 4656 | after the structure is initialized. |
| 4657 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4658 | When the simplified API needs to convert between sRGB and linear colorspaces, |
| 4659 | the actual sRGB transfer curve defined in the sRGB specification (see the |
Glenn Randers-Pehrson | 64f8110 | 2017-04-03 15:25:40 -0500 | [diff] [blame] | 4660 | article at https://en.wikipedia.org/wiki/SRGB) is used, not the gamma=1/2.2 |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4661 | approximation used elsewhere in libpng. |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4662 | |
| 4663 | WRITE APIS |
| 4664 | |
| 4665 | For write you must initialize a png_image structure to describe the image to |
| 4666 | be written: |
| 4667 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4668 | version: must be set to PNG_IMAGE_VERSION |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4669 | opaque: must be initialized to NULL |
| 4670 | width: image width in pixels |
| 4671 | height: image height in rows |
| 4672 | format: the format of the data you wish to write |
| 4673 | flags: set to 0 unless one of the defined flags applies; set |
| 4674 | PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB for color format images |
| 4675 | where the RGB values do not correspond to the colors in sRGB. |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4676 | colormap_entries: set to the number of entries in the color-map (0 to 256) |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4677 | |
| 4678 | int png_image_write_to_file, (png_imagep image, |
| 4679 | const char *file, int convert_to_8bit, const void *buffer, |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4680 | png_int_32 row_stride, const void *colormap)); |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4681 | |
| 4682 | Write the image to the named file. |
| 4683 | |
Glenn Randers-Pehrson | d2b8d46 | 2016-01-23 14:01:44 -0600 | [diff] [blame] | 4684 | int png_image_write_to_memory (png_imagep image, void *memory, |
| 4685 | png_alloc_size_t * PNG_RESTRICT memory_bytes, |
| 4686 | int convert_to_8_bit, const void *buffer, ptrdiff_t row_stride, |
| 4687 | const void *colormap)); |
| 4688 | |
| 4689 | Write the image to memory. |
| 4690 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4691 | int png_image_write_to_stdio(png_imagep image, FILE *file, |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4692 | int convert_to_8_bit, const void *buffer, |
| 4693 | png_int_32 row_stride, const void *colormap) |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4694 | |
| 4695 | Write the image to the given (FILE*). |
| 4696 | |
| 4697 | With all write APIs if image is in one of the linear formats with |
| 4698 | (png_uint_16) data then setting convert_to_8_bit will cause the output to be |
| 4699 | a (png_byte) PNG gamma encoded according to the sRGB specification, otherwise |
| 4700 | a 16-bit linear encoded PNG file is written. |
| 4701 | |
| 4702 | With all APIs row_stride is handled as in the read APIs - it is the spacing |
| 4703 | from one row to the next in component sized units (float) and if negative |
Glenn Randers-Pehrson | 279dc3f | 2015-05-06 17:02:47 -0500 | [diff] [blame] | 4704 | indicates a bottom-up row layout in the buffer. If you pass zero, libpng will |
| 4705 | calculate the row_stride for you from the width and number of channels. |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4706 | |
| 4707 | Note that the write API does not support interlacing, sub-8-bit pixels, |
Glenn Randers-Pehrson | 279dc3f | 2015-05-06 17:02:47 -0500 | [diff] [blame] | 4708 | indexed (paletted) images, or most ancillary chunks. |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 4709 | |
| 4710 | .SH VI. Modifying/Customizing libpng |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4711 | |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 4712 | There are two issues here. The first is changing how libpng does |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4713 | standard things like memory allocation, input/output, and error handling. |
| 4714 | The second deals with more complicated things like adding new chunks, |
| 4715 | adding new transformations, and generally changing how libpng works. |
Glenn Randers-Pehrson | 231e687 | 2001-01-12 15:13:06 -0600 | [diff] [blame] | 4716 | Both of those are compile-time issues; that is, they are generally |
| 4717 | determined at the time the code is written, and there is rarely a need |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 4718 | to provide the user with a means of changing them. |
Glenn Randers-Pehrson | 231e687 | 2001-01-12 15:13:06 -0600 | [diff] [blame] | 4719 | |
| 4720 | Memory allocation, input/output, and error handling |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4721 | |
| 4722 | All of the memory allocation, input/output, and error handling in libpng |
Glenn Randers-Pehrson | 231e687 | 2001-01-12 15:13:06 -0600 | [diff] [blame] | 4723 | goes through callbacks that are user-settable. The default routines are |
Glenn Randers-Pehrson | 228bd39 | 2000-04-23 23:14:02 -0500 | [diff] [blame] | 4724 | in pngmem.c, pngrio.c, pngwio.c, and pngerror.c, respectively. To change |
Glenn Randers-Pehrson | a77ef62 | 2000-02-18 13:48:52 -0600 | [diff] [blame] | 4725 | these functions, call the appropriate png_set_*_fn() function. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4726 | |
Glenn Randers-Pehrson | f210a05 | 2009-11-12 10:02:24 -0600 | [diff] [blame] | 4727 | Memory allocation is done through the functions png_malloc(), png_calloc(), |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4728 | and png_free(). The png_malloc() and png_free() functions currently just |
| 4729 | call the standard C functions and png_calloc() calls png_malloc() and then |
| 4730 | clears the newly allocated memory to zero; note that png_calloc(png_ptr, size) |
| 4731 | is not the same as the calloc(number, size) function provided by stdlib.h. |
| 4732 | There is limited support for certain systems with segmented memory |
| 4733 | architectures and the types of pointers declared by png.h match this; you |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 4734 | will have to use appropriate pointers in your application. If you prefer |
| 4735 | to use a different method of allocating and freeing data, you can use |
| 4736 | png_create_read_struct_2() or png_create_write_struct_2() to register your |
| 4737 | own functions as described above. These functions also provide a void |
| 4738 | pointer that can be retrieved via |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 4739 | |
| 4740 | mem_ptr=png_get_mem_ptr(png_ptr); |
| 4741 | |
| 4742 | Your replacement memory functions must have prototypes as follows: |
| 4743 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 4744 | png_voidp malloc_fn(png_structp png_ptr, |
Glenn Randers-Pehrson | e3f3c4e | 2010-02-07 18:08:50 -0600 | [diff] [blame] | 4745 | png_alloc_size_t size); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 4746 | |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 4747 | void free_fn(png_structp png_ptr, png_voidp ptr); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4748 | |
Glenn Randers-Pehrson | 5fea36f | 2004-07-28 08:20:44 -0500 | [diff] [blame] | 4749 | Your malloc_fn() must return NULL in case of failure. The png_malloc() |
| 4750 | function will normally call png_error() if it receives a NULL from the |
| 4751 | system memory allocator or from your replacement malloc_fn(). |
Glenn Randers-Pehrson | 82ae383 | 2001-04-20 10:32:10 -0500 | [diff] [blame] | 4752 | |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 4753 | Your free_fn() will never be called with a NULL ptr, since libpng's |
| 4754 | png_free() checks for NULL before calling free_fn(). |
| 4755 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4756 | Input/Output in libpng is done through png_read() and png_write(), |
| 4757 | which currently just call fread() and fwrite(). The FILE * is stored in |
| 4758 | png_struct and is initialized via png_init_io(). If you wish to change |
| 4759 | the method of I/O, the library supplies callbacks that you can set |
| 4760 | through the function png_set_read_fn() and png_set_write_fn() at run |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 4761 | time, instead of calling the png_init_io() function. These functions |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4762 | also provide a void pointer that can be retrieved via the function |
| 4763 | png_get_io_ptr(). For example: |
| 4764 | |
Glenn Randers-Pehrson | f7d1a17 | 1998-06-06 15:31:35 -0500 | [diff] [blame] | 4765 | png_set_read_fn(png_structp read_ptr, |
| 4766 | voidp read_io_ptr, png_rw_ptr read_data_fn) |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4767 | |
Glenn Randers-Pehrson | f7d1a17 | 1998-06-06 15:31:35 -0500 | [diff] [blame] | 4768 | png_set_write_fn(png_structp write_ptr, |
| 4769 | voidp write_io_ptr, png_rw_ptr write_data_fn, |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4770 | png_flush_ptr output_flush_fn); |
| 4771 | |
Glenn Randers-Pehrson | f7d1a17 | 1998-06-06 15:31:35 -0500 | [diff] [blame] | 4772 | voidp read_io_ptr = png_get_io_ptr(read_ptr); |
| 4773 | voidp write_io_ptr = png_get_io_ptr(write_ptr); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4774 | |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 4775 | The replacement I/O functions must have prototypes as follows: |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4776 | |
| 4777 | void user_read_data(png_structp png_ptr, |
Cosmin Truta | a74aa9a | 2018-06-17 22:37:44 -0400 | [diff] [blame] | 4778 | png_bytep data, size_t length); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 4779 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4780 | void user_write_data(png_structp png_ptr, |
Cosmin Truta | a74aa9a | 2018-06-17 22:37:44 -0400 | [diff] [blame] | 4781 | png_bytep data, size_t length); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 4782 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4783 | void user_flush_data(png_structp png_ptr); |
| 4784 | |
Glenn Randers-Pehrson | ebd7f9a | 2006-10-19 09:37:56 -0500 | [diff] [blame] | 4785 | The user_read_data() function is responsible for detecting and |
| 4786 | handling end-of-data errors. |
| 4787 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4788 | Supplying NULL for the read, write, or flush functions sets them back |
Glenn Randers-Pehrson | 8fb550c | 2009-03-21 08:15:32 -0500 | [diff] [blame] | 4789 | to using the default C stream functions, which expect the io_ptr to |
| 4790 | point to a standard *FILE structure. It is probably a mistake |
| 4791 | to use NULL for one of write_data_fn and output_flush_fn but not both |
| 4792 | of them, unless you have built libpng with PNG_NO_WRITE_FLUSH defined. |
| 4793 | It is an error to read from a write stream, and vice versa. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4794 | |
| 4795 | Error handling in libpng is done through png_error() and png_warning(). |
| 4796 | Errors handled through png_error() are fatal, meaning that png_error() |
| 4797 | should never return to its caller. Currently, this is handled via |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 4798 | setjmp() and longjmp() (unless you have compiled libpng with |
Glenn Randers-Pehrson | 54ac9a9 | 2010-04-02 17:06:22 -0500 | [diff] [blame] | 4799 | PNG_NO_SETJMP, in which case it is handled via PNG_ABORT()), |
Glenn Randers-Pehrson | 6098807 | 2010-04-13 22:11:06 -0500 | [diff] [blame] | 4800 | but you could change this to do things like exit() if you should wish, |
Glenn Randers-Pehrson | 54ac9a9 | 2010-04-02 17:06:22 -0500 | [diff] [blame] | 4801 | as long as your function does not return. |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 4802 | |
| 4803 | On non-fatal errors, png_warning() is called |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4804 | to print a warning message, and then control returns to the calling code. |
| 4805 | By default png_error() and png_warning() print a message on stderr via |
Glenn Randers-Pehrson | 38e6e77 | 2000-04-09 19:06:13 -0500 | [diff] [blame] | 4806 | fprintf() unless the library is compiled with PNG_NO_CONSOLE_IO defined |
| 4807 | (because you don't want the messages) or PNG_NO_STDIO defined (because |
| 4808 | fprintf() isn't available). If you wish to change the behavior of the error |
| 4809 | functions, you will need to set up your own message callbacks. These |
| 4810 | functions are normally supplied at the time that the png_struct is created. |
Glenn Randers-Pehrson | 228bd39 | 2000-04-23 23:14:02 -0500 | [diff] [blame] | 4811 | It is also possible to redirect errors and warnings to your own replacement |
| 4812 | functions after png_create_*_struct() has been called by calling: |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4813 | |
| 4814 | png_set_error_fn(png_structp png_ptr, |
| 4815 | png_voidp error_ptr, png_error_ptr error_fn, |
| 4816 | png_error_ptr warning_fn); |
| 4817 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4818 | If NULL is supplied for either error_fn or warning_fn, then the libpng |
| 4819 | default function will be used, calling fprintf() and/or longjmp() if a |
| 4820 | problem is encountered. The replacement error functions should have |
| 4821 | parameters as follows: |
| 4822 | |
| 4823 | void user_error_fn(png_structp png_ptr, |
| 4824 | png_const_charp error_msg); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 4825 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4826 | void user_warning_fn(png_structp png_ptr, |
| 4827 | png_const_charp warning_msg); |
| 4828 | |
Glenn Randers-Pehrson | 92fcd25 | 2017-03-28 12:47:49 -0500 | [diff] [blame] | 4829 | Then, within your user_error_fn or user_warning_fn, you can retrieve |
| 4830 | the error_ptr if you need it, by calling |
Glenn Randers-Pehrson | 9b0170d | 2017-03-28 12:38:47 -0500 | [diff] [blame] | 4831 | |
| 4832 | png_voidp error_ptr = png_get_error_ptr(png_ptr); |
| 4833 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4834 | The motivation behind using setjmp() and longjmp() is the C++ throw and |
| 4835 | catch exception handling methods. This makes the code much easier to write, |
| 4836 | as there is no need to check every return code of every function call. |
| 4837 | However, there are some uncertainties about the status of local variables |
Glenn Randers-Pehrson | f210a05 | 2009-11-12 10:02:24 -0600 | [diff] [blame] | 4838 | after a longjmp, so the user may want to be careful about doing anything |
| 4839 | after setjmp returns non-zero besides returning itself. Consult your |
| 4840 | compiler documentation for more details. For an alternative approach, you |
Glenn Randers-Pehrson | 64f8110 | 2017-04-03 15:25:40 -0500 | [diff] [blame] | 4841 | may wish to use the "cexcept" facility (see https://cexcept.sourceforge.io/), |
Glenn Randers-Pehrson | a5e5547 | 2011-07-12 10:13:32 -0500 | [diff] [blame] | 4842 | which is illustrated in pngvalid.c and in contrib/visupng. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4843 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4844 | Beginning in libpng-1.4.0, the png_set_benign_errors() API became available. |
| 4845 | You can use this to handle certain errors (normally handled as errors) |
| 4846 | as warnings. |
| 4847 | |
| 4848 | png_set_benign_errors (png_ptr, int allowed); |
| 4849 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 4850 | allowed: 0: treat png_benign_error() as an error. |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4851 | 1: treat png_benign_error() as a warning. |
| 4852 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 4853 | As of libpng-1.6.0, the default condition is to treat benign errors as |
| 4854 | warnings while reading and as errors while writing. |
| 4855 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 4856 | .SS Custom chunks |
| 4857 | |
| 4858 | If you need to read or write custom chunks, you may need to get deeper |
| 4859 | into the libpng code. The library now has mechanisms for storing |
| 4860 | and writing chunks of unknown type; you can even declare callbacks |
Glenn Randers-Pehrson | 9c3ab68 | 2006-02-20 22:09:05 -0600 | [diff] [blame] | 4861 | for custom chunks. However, this may not be good enough if the |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 4862 | library code itself needs to know about interactions between your |
| 4863 | chunk and existing `intrinsic' chunks. |
| 4864 | |
| 4865 | If you need to write a new intrinsic chunk, first read the PNG |
Glenn Randers-Pehrson | f210a05 | 2009-11-12 10:02:24 -0600 | [diff] [blame] | 4866 | specification. Acquire a first level of understanding of how it works. |
| 4867 | Pay particular attention to the sections that describe chunk names, |
| 4868 | and look at how other chunks were designed, so you can do things |
| 4869 | similarly. Second, check out the sections of libpng that read and |
| 4870 | write chunks. Try to find a chunk that is similar to yours and use |
| 4871 | it as a template. More details can be found in the comments inside |
Glenn Randers-Pehrson | a5e5547 | 2011-07-12 10:13:32 -0500 | [diff] [blame] | 4872 | the code. It is best to handle private or unknown chunks in a generic method, |
| 4873 | via callback functions, instead of by modifying libpng functions. This |
| 4874 | is illustrated in pngtest.c, which uses a callback function to handle a |
| 4875 | private "vpAg" chunk and the new "sTER" chunk, which are both unknown to |
| 4876 | libpng. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4877 | |
| 4878 | If you wish to write your own transformation for the data, look through |
| 4879 | the part of the code that does the transformations, and check out some of |
| 4880 | the simpler ones to get an idea of how they work. Try to find a similar |
| 4881 | transformation to the one you want to add and copy off of it. More details |
| 4882 | can be found in the comments inside the code itself. |
| 4883 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 4884 | .SS Configuring for gui/windowing platforms: |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4885 | |
| 4886 | You will need to write new error and warning functions that use the GUI |
| 4887 | interface, as described previously, and set them to be the error and |
Glenn Randers-Pehrson | a77ef62 | 2000-02-18 13:48:52 -0600 | [diff] [blame] | 4888 | warning functions at the time that png_create_*_struct() is called, |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4889 | in order to have them available during the structure initialization. |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 4890 | They can be changed later via png_set_error_fn(). On some compilers, |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4891 | you may also have to change the memory allocators (png_malloc, etc.). |
| 4892 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 4893 | .SS Configuring zlib: |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4894 | |
| 4895 | There are special functions to configure the compression. Perhaps the |
| 4896 | most useful one changes the compression level, which currently uses |
| 4897 | input compression values in the range 0 - 9. The library normally |
| 4898 | uses the default compression level (Z_DEFAULT_COMPRESSION = 6). Tests |
| 4899 | have shown that for a large majority of images, compression values in |
| 4900 | the range 3-6 compress nearly as well as higher levels, and do so much |
| 4901 | faster. For online applications it may be desirable to have maximum speed |
| 4902 | (Z_BEST_SPEED = 1). With versions of zlib after v0.99, you can also |
| 4903 | specify no compression (Z_NO_COMPRESSION = 0), but this would create |
| 4904 | files larger than just storing the raw bitmap. You can specify the |
| 4905 | compression level by calling: |
| 4906 | |
Glenn Randers-Pehrson | 38734ee | 2011-03-03 06:23:31 -0600 | [diff] [blame] | 4907 | #include zlib.h |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4908 | png_set_compression_level(png_ptr, level); |
| 4909 | |
| 4910 | Another useful one is to reduce the memory level used by the library. |
| 4911 | The memory level defaults to 8, but it can be lowered if you are |
| 4912 | short on memory (running DOS, for example, where you only have 640K). |
Glenn Randers-Pehrson | 4fb046a | 2002-04-15 09:25:51 -0500 | [diff] [blame] | 4913 | Note that the memory level does have an effect on compression; among |
| 4914 | other things, lower levels will result in sections of incompressible |
| 4915 | data being emitted in smaller stored blocks, with a correspondingly |
| 4916 | larger relative overhead of up to 15% in the worst case. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4917 | |
Glenn Randers-Pehrson | 38734ee | 2011-03-03 06:23:31 -0600 | [diff] [blame] | 4918 | #include zlib.h |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4919 | png_set_compression_mem_level(png_ptr, level); |
| 4920 | |
| 4921 | The other functions are for configuring zlib. They are not recommended |
| 4922 | for normal use and may result in writing an invalid PNG file. See |
| 4923 | zlib.h for more information on what these mean. |
| 4924 | |
Glenn Randers-Pehrson | 38734ee | 2011-03-03 06:23:31 -0600 | [diff] [blame] | 4925 | #include zlib.h |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4926 | png_set_compression_strategy(png_ptr, |
| 4927 | strategy); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 4928 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4929 | png_set_compression_window_bits(png_ptr, |
| 4930 | window_bits); |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 4931 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4932 | png_set_compression_method(png_ptr, method); |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 4933 | |
Glenn Randers-Pehrson | 6b570f1 | 2014-03-25 10:31:12 -0500 | [diff] [blame] | 4934 | This controls the size of the IDAT chunks (default 8192): |
| 4935 | |
Glenn Randers-Pehrson | 228bd39 | 2000-04-23 23:14:02 -0500 | [diff] [blame] | 4936 | png_set_compression_buffer_size(png_ptr, size); |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4937 | |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 4938 | As of libpng version 1.5.4, additional APIs became |
| 4939 | available to set these separately for non-IDAT |
| 4940 | compressed chunks such as zTXt, iTXt, and iCCP: |
| 4941 | |
| 4942 | #include zlib.h |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 4943 | #if PNG_LIBPNG_VER >= 10504 |
Glenn Randers-Pehrson | 7a28724 | 2011-07-26 12:03:11 -0500 | [diff] [blame] | 4944 | png_set_text_compression_level(png_ptr, level); |
| 4945 | |
| 4946 | png_set_text_compression_mem_level(png_ptr, level); |
| 4947 | |
| 4948 | png_set_text_compression_strategy(png_ptr, |
| 4949 | strategy); |
| 4950 | |
| 4951 | png_set_text_compression_window_bits(png_ptr, |
| 4952 | window_bits); |
| 4953 | |
| 4954 | png_set_text_compression_method(png_ptr, method); |
| 4955 | #endif |
| 4956 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 4957 | .SS Controlling row filtering |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4958 | |
| 4959 | If you want to control whether libpng uses filtering or not, which |
| 4960 | filters are used, and how it goes about picking row filters, you |
| 4961 | can call one of these functions. The selection and configuration |
| 4962 | of row filters can have a significant impact on the size and |
| 4963 | encoding speed and a somewhat lesser impact on the decoding speed |
| 4964 | of an image. Filtering is enabled by default for RGB and grayscale |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 4965 | images (with and without alpha), but not for paletted images nor |
| 4966 | for any images with bit depths less than 8 bits/pixel. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4967 | |
| 4968 | The 'method' parameter sets the main filtering method, which is |
Glenn Randers-Pehrson | 4393a9a | 1999-09-17 12:27:26 -0500 | [diff] [blame] | 4969 | currently only '0' in the PNG 1.2 specification. The 'filters' |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4970 | parameter sets which filter(s), if any, should be used for each |
Glenn Randers-Pehrson | fa551df | 2016-04-11 08:23:16 -0500 | [diff] [blame] | 4971 | scanline. Possible values are PNG_ALL_FILTERS, PNG_NO_FILTERS, |
| 4972 | or PNG_FAST_FILTERS to turn filtering on and off, or to turn on |
| 4973 | just the fast-decoding subset of filters, respectively. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4974 | |
| 4975 | Individual filter types are PNG_FILTER_NONE, PNG_FILTER_SUB, |
| 4976 | PNG_FILTER_UP, PNG_FILTER_AVG, PNG_FILTER_PAETH, which can be bitwise |
Glenn Randers-Pehrson | 6942d53 | 2000-05-01 09:31:54 -0500 | [diff] [blame] | 4977 | ORed together with '|' to specify one or more filters to use. |
Glenn Randers-Pehrson | 4fb046a | 2002-04-15 09:25:51 -0500 | [diff] [blame] | 4978 | These filters are described in more detail in the PNG specification. |
| 4979 | If you intend to change the filter type during the course of writing |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4980 | the image, you should start with flags set for all of the filters |
| 4981 | you intend to use so that libpng can initialize its internal |
Glenn Randers-Pehrson | 4fb046a | 2002-04-15 09:25:51 -0500 | [diff] [blame] | 4982 | structures appropriately for all of the filter types. (Note that this |
| 4983 | means the first row must always be adaptively filtered, because libpng |
| 4984 | currently does not allocate the filter buffers until png_write_row() |
| 4985 | is called for the first time.) |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4986 | |
Glenn Randers-Pehrson | fa551df | 2016-04-11 08:23:16 -0500 | [diff] [blame] | 4987 | filters = PNG_NO_FILTERS; |
| 4988 | filters = PNG_ALL_FILTERS; |
| 4989 | filters = PNG_FAST_FILTERS; |
| 4990 | |
| 4991 | or |
| 4992 | |
| 4993 | filters = PNG_FILTER_NONE | PNG_FILTER_SUB | |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 4994 | PNG_FILTER_UP | PNG_FILTER_AVG | |
Glenn Randers-Pehrson | fa551df | 2016-04-11 08:23:16 -0500 | [diff] [blame] | 4995 | PNG_FILTER_PAETH; |
Glenn Randers-Pehrson | 228bd39 | 2000-04-23 23:14:02 -0500 | [diff] [blame] | 4996 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 4997 | png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, |
| 4998 | filters); |
Glenn Randers-Pehrson | fa551df | 2016-04-11 08:23:16 -0500 | [diff] [blame] | 4999 | |
Glenn Randers-Pehrson | 1909560 | 2001-03-14 07:08:39 -0600 | [diff] [blame] | 5000 | The second parameter can also be |
| 5001 | PNG_INTRAPIXEL_DIFFERENCING if you are |
| 5002 | writing a PNG to be embedded in a MNG |
| 5003 | datastream. This parameter must be the |
| 5004 | same as the value of filter_method used |
| 5005 | in png_set_IHDR(). |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 5006 | |
Glenn Randers-Pehrson | 61c32d9 | 2000-02-04 23:40:16 -0600 | [diff] [blame] | 5007 | .SS Requesting debug printout |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 5008 | |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 5009 | The macro definition PNG_DEBUG can be used to request debugging |
| 5010 | printout. Set it to an integer value in the range 0 to 3. Higher |
| 5011 | numbers result in increasing amounts of debugging information. The |
| 5012 | information is printed to the "stderr" file, unless another file |
| 5013 | name is specified in the PNG_DEBUG_FILE macro definition. |
| 5014 | |
| 5015 | When PNG_DEBUG > 0, the following functions (macros) become available: |
| 5016 | |
| 5017 | png_debug(level, message) |
| 5018 | png_debug1(level, message, p1) |
| 5019 | png_debug2(level, message, p1, p2) |
| 5020 | |
| 5021 | in which "level" is compared to PNG_DEBUG to decide whether to print |
| 5022 | the message, "message" is the formatted string to be printed, |
| 5023 | and p1 and p2 are parameters that are to be embedded in the string |
| 5024 | according to printf-style formatting directives. For example, |
| 5025 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5026 | png_debug1(2, "foo=%d", foo); |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 5027 | |
| 5028 | is expanded to |
| 5029 | |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 5030 | if (PNG_DEBUG > 2) |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5031 | fprintf(PNG_DEBUG_FILE, "foo=%d\en", foo); |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 5032 | |
| 5033 | When PNG_DEBUG is defined but is zero, the macros aren't defined, but you |
| 5034 | can still use PNG_DEBUG to control your own debugging: |
| 5035 | |
| 5036 | #ifdef PNG_DEBUG |
| 5037 | fprintf(stderr, ... |
| 5038 | #endif |
| 5039 | |
| 5040 | When PNG_DEBUG = 1, the macros are defined, but only png_debug statements |
| 5041 | having level = 0 will be printed. There aren't any such statements in |
| 5042 | this version of libpng, but if you insert some they will be printed. |
| 5043 | |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 5044 | .SH VII. MNG support |
Glenn Randers-Pehrson | 2ad31ae | 2000-12-15 08:54:42 -0600 | [diff] [blame] | 5045 | |
| 5046 | The MNG specification (available at http://www.libpng.org/pub/mng) allows |
| 5047 | certain extensions to PNG for PNG images that are embedded in MNG datastreams. |
| 5048 | Libpng can support some of these extensions. To enable them, use the |
| 5049 | png_permit_mng_features() function: |
| 5050 | |
| 5051 | feature_set = png_permit_mng_features(png_ptr, mask) |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 5052 | |
Glenn Randers-Pehrson | ebd7f9a | 2006-10-19 09:37:56 -0500 | [diff] [blame] | 5053 | mask is a png_uint_32 containing the bitwise OR of the |
Glenn Randers-Pehrson | 2ad31ae | 2000-12-15 08:54:42 -0600 | [diff] [blame] | 5054 | features you want to enable. These include |
| 5055 | PNG_FLAG_MNG_EMPTY_PLTE |
| 5056 | PNG_FLAG_MNG_FILTER_64 |
| 5057 | PNG_ALL_MNG_FEATURES |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 5058 | |
Glenn Randers-Pehrson | ebd7f9a | 2006-10-19 09:37:56 -0500 | [diff] [blame] | 5059 | feature_set is a png_uint_32 that is the bitwise AND of |
Glenn Randers-Pehrson | 2ad31ae | 2000-12-15 08:54:42 -0600 | [diff] [blame] | 5060 | your mask with the set of MNG features that is |
| 5061 | supported by the version of libpng that you are using. |
| 5062 | |
Glenn Randers-Pehrson | 408b421 | 2000-12-18 09:33:57 -0600 | [diff] [blame] | 5063 | It is an error to use this function when reading or writing a standalone |
| 5064 | PNG file with the PNG 8-byte signature. The PNG datastream must be wrapped |
Glenn Randers-Pehrson | f05f803 | 2000-12-23 14:27:39 -0600 | [diff] [blame] | 5065 | in a MNG datastream. As a minimum, it must have the MNG 8-byte signature |
| 5066 | and the MHDR and MEND chunks. Libpng does not provide support for these |
| 5067 | or any other MNG chunks; your application must provide its own support for |
| 5068 | them. You may wish to consider using libmng (available at |
Glenn Randers-Pehrson | 64f8110 | 2017-04-03 15:25:40 -0500 | [diff] [blame] | 5069 | https://www.libmng.com/) instead. |
Glenn Randers-Pehrson | 408b421 | 2000-12-18 09:33:57 -0600 | [diff] [blame] | 5070 | |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 5071 | .SH VIII. Changes to Libpng from version 0.88 |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 5072 | |
| 5073 | It should be noted that versions of libpng later than 0.96 are not |
| 5074 | distributed by the original libpng author, Guy Schalnat, nor by |
| 5075 | Andreas Dilger, who had taken over from Guy during 1996 and 1997, and |
| 5076 | distributed versions 0.89 through 0.96, but rather by another member |
| 5077 | of the original PNG Group, Glenn Randers-Pehrson. Guy and Andreas are |
| 5078 | still alive and well, but they have moved on to other things. |
| 5079 | |
| 5080 | The old libpng functions png_read_init(), png_write_init(), |
Glenn Randers-Pehrson | 8b6a889 | 2001-05-18 04:54:50 -0500 | [diff] [blame] | 5081 | png_info_init(), png_read_destroy(), and png_write_destroy() have been |
Glenn Randers-Pehrson | 7529457 | 2000-05-06 14:09:57 -0500 | [diff] [blame] | 5082 | moved to PNG_INTERNAL in version 0.95 to discourage their use. These |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 5083 | functions will be removed from libpng version 1.4.0. |
Glenn Randers-Pehrson | 7529457 | 2000-05-06 14:09:57 -0500 | [diff] [blame] | 5084 | |
| 5085 | The preferred method of creating and initializing the libpng structures is |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 5086 | via the png_create_read_struct(), png_create_write_struct(), and |
| 5087 | png_create_info_struct() because they isolate the size of the structures |
| 5088 | from the application, allow version error checking, and also allow the |
| 5089 | use of custom error handling routines during the initialization, which |
| 5090 | the old functions do not. The functions png_read_destroy() and |
| 5091 | png_write_destroy() do not actually free the memory that libpng |
| 5092 | allocated for these structs, but just reset the data structures, so they |
| 5093 | can be used instead of png_destroy_read_struct() and |
| 5094 | png_destroy_write_struct() if you feel there is too much system overhead |
| 5095 | allocating and freeing the png_struct for each image read. |
| 5096 | |
| 5097 | Setting the error callbacks via png_set_message_fn() before |
| 5098 | png_read_init() as was suggested in libpng-0.88 is no longer supported |
Glenn Randers-Pehrson | 5c6aeb2 | 1998-12-29 11:47:59 -0600 | [diff] [blame] | 5099 | because this caused applications that do not use custom error functions |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 5100 | to fail if the png_ptr was not initialized to zero. It is still possible |
| 5101 | to set the error callbacks AFTER png_read_init(), or to change them with |
Glenn Randers-Pehrson | 7529457 | 2000-05-06 14:09:57 -0500 | [diff] [blame] | 5102 | png_set_error_fn(), which is essentially the same function, but with a new |
| 5103 | name to force compilation errors with applications that try to use the old |
| 5104 | method. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 5105 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5106 | Support for the sCAL, iCCP, iTXt, and sPLT chunks was added at libpng-1.0.6; |
| 5107 | however, iTXt support was not enabled by default. |
| 5108 | |
Glenn Randers-Pehrson | 1ef65b6 | 2000-05-12 06:19:53 -0500 | [diff] [blame] | 5109 | Starting with version 1.0.7, you can find out which version of the library |
| 5110 | you are using at run-time: |
| 5111 | |
| 5112 | png_uint_32 libpng_vn = png_access_version_number(); |
| 5113 | |
| 5114 | The number libpng_vn is constructed from the major version, minor |
| 5115 | version with leading zero, and release number with leading zero, |
| 5116 | (e.g., libpng_vn for version 1.0.7 is 10007). |
| 5117 | |
Glenn Randers-Pehrson | 95ba417 | 2011-09-08 12:21:42 -0500 | [diff] [blame] | 5118 | Note that this function does not take a png_ptr, so you can call it |
| 5119 | before you've created one. |
| 5120 | |
Glenn Randers-Pehrson | 1ef65b6 | 2000-05-12 06:19:53 -0500 | [diff] [blame] | 5121 | You can also check which version of png.h you used when compiling your |
| 5122 | application: |
| 5123 | |
| 5124 | png_uint_32 application_vn = PNG_LIBPNG_VER; |
| 5125 | |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 5126 | .SH IX. Changes to Libpng from version 1.0.x to 1.2.x |
Glenn Randers-Pehrson | 87544ac | 1999-01-13 22:06:39 -0600 | [diff] [blame] | 5127 | |
Glenn Randers-Pehrson | 6a9c2ce | 2009-03-27 19:30:10 -0500 | [diff] [blame] | 5128 | Support for user memory management was enabled by default. To |
| 5129 | accomplish this, the functions png_create_read_struct_2(), |
| 5130 | png_create_write_struct_2(), png_set_mem_fn(), png_get_mem_ptr(), |
| 5131 | png_malloc_default(), and png_free_default() were added. |
| 5132 | |
Glenn Randers-Pehrson | d6ea40a | 2009-11-02 07:32:00 -0600 | [diff] [blame] | 5133 | Support for the iTXt chunk has been enabled by default as of |
| 5134 | version 1.2.41. |
| 5135 | |
Glenn Randers-Pehrson | 6a9c2ce | 2009-03-27 19:30:10 -0500 | [diff] [blame] | 5136 | Support for certain MNG features was enabled. |
| 5137 | |
| 5138 | Support for numbered error messages was added. However, we never got |
| 5139 | around to actually numbering the error messages. The function |
| 5140 | png_set_strip_error_numbers() was added (Note: the prototype for this |
| 5141 | function was inadvertently removed from png.h in PNG_NO_ASSEMBLER_CODE |
| 5142 | builds of libpng-1.2.15. It was restored in libpng-1.2.36). |
| 5143 | |
| 5144 | The png_malloc_warn() function was added at libpng-1.2.3. This issues |
| 5145 | a png_warning and returns NULL instead of aborting when it fails to |
| 5146 | acquire the requested memory allocation. |
| 5147 | |
| 5148 | Support for setting user limits on image width and height was enabled |
| 5149 | by default. The functions png_set_user_limits(), png_get_user_width_max(), |
| 5150 | and png_get_user_height_max() were added at libpng-1.2.6. |
| 5151 | |
| 5152 | The png_set_add_alpha() function was added at libpng-1.2.7. |
| 5153 | |
| 5154 | The function png_set_expand_gray_1_2_4_to_8() was added at libpng-1.2.9. |
| 5155 | Unlike png_set_gray_1_2_4_to_8(), the new function does not expand the |
| 5156 | tRNS chunk to alpha. The png_set_gray_1_2_4_to_8() function is |
| 5157 | deprecated. |
| 5158 | |
| 5159 | A number of macro definitions in support of runtime selection of |
| 5160 | assembler code features (especially Intel MMX code support) were |
| 5161 | added at libpng-1.2.0: |
| 5162 | |
| 5163 | PNG_ASM_FLAG_MMX_SUPPORT_COMPILED |
| 5164 | PNG_ASM_FLAG_MMX_SUPPORT_IN_CPU |
| 5165 | PNG_ASM_FLAG_MMX_READ_COMBINE_ROW |
| 5166 | PNG_ASM_FLAG_MMX_READ_INTERLACE |
| 5167 | PNG_ASM_FLAG_MMX_READ_FILTER_SUB |
| 5168 | PNG_ASM_FLAG_MMX_READ_FILTER_UP |
| 5169 | PNG_ASM_FLAG_MMX_READ_FILTER_AVG |
| 5170 | PNG_ASM_FLAG_MMX_READ_FILTER_PAETH |
| 5171 | PNG_ASM_FLAGS_INITIALIZED |
| 5172 | PNG_MMX_READ_FLAGS |
| 5173 | PNG_MMX_FLAGS |
| 5174 | PNG_MMX_WRITE_FLAGS |
| 5175 | PNG_MMX_FLAGS |
| 5176 | |
| 5177 | We added the following functions in support of runtime |
| 5178 | selection of assembler code features: |
| 5179 | |
| 5180 | png_get_mmx_flagmask() |
| 5181 | png_set_mmx_thresholds() |
| 5182 | png_get_asm_flags() |
| 5183 | png_get_mmx_bitdepth_threshold() |
| 5184 | png_get_mmx_rowbytes_threshold() |
| 5185 | png_set_asm_flags() |
| 5186 | |
| 5187 | We replaced all of these functions with simple stubs in libpng-1.2.20, |
| 5188 | when the Intel assembler code was removed due to a licensing issue. |
| 5189 | |
Glenn Randers-Pehrson | 3d893a0 | 2009-08-31 13:32:46 -0500 | [diff] [blame] | 5190 | These macros are deprecated: |
| 5191 | |
| 5192 | PNG_READ_TRANSFORMS_NOT_SUPPORTED |
| 5193 | PNG_PROGRESSIVE_READ_NOT_SUPPORTED |
| 5194 | PNG_NO_SEQUENTIAL_READ_SUPPORTED |
| 5195 | PNG_WRITE_TRANSFORMS_NOT_SUPPORTED |
| 5196 | PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED |
| 5197 | PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED |
| 5198 | |
| 5199 | They have been replaced, respectively, by: |
| 5200 | |
| 5201 | PNG_NO_READ_TRANSFORMS |
| 5202 | PNG_NO_PROGRESSIVE_READ |
| 5203 | PNG_NO_SEQUENTIAL_READ |
| 5204 | PNG_NO_WRITE_TRANSFORMS |
| 5205 | PNG_NO_READ_ANCILLARY_CHUNKS |
| 5206 | PNG_NO_WRITE_ANCILLARY_CHUNKS |
| 5207 | |
Glenn Randers-Pehrson | 6a9c2ce | 2009-03-27 19:30:10 -0500 | [diff] [blame] | 5208 | PNG_MAX_UINT was replaced with PNG_UINT_31_MAX. It has been |
| 5209 | deprecated since libpng-1.0.16 and libpng-1.2.6. |
| 5210 | |
| 5211 | The function |
| 5212 | png_check_sig(sig, num) |
| 5213 | was replaced with |
| 5214 | !png_sig_cmp(sig, 0, num) |
| 5215 | It has been deprecated since libpng-0.90. |
| 5216 | |
Glenn Randers-Pehrson | 6a9c2ce | 2009-03-27 19:30:10 -0500 | [diff] [blame] | 5217 | The function |
| 5218 | png_set_gray_1_2_4_to_8() |
| 5219 | which also expands tRNS to alpha was replaced with |
| 5220 | png_set_expand_gray_1_2_4_to_8() |
| 5221 | which does not. It has been deprecated since libpng-1.0.18 and 1.2.9. |
Glenn Randers-Pehrson | e3f3c4e | 2010-02-07 18:08:50 -0600 | [diff] [blame] | 5222 | |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 5223 | .SH X. Changes to Libpng from version 1.0.x/1.2.x to 1.4.x |
Glenn Randers-Pehrson | d740c84 | 2009-11-04 19:01:54 -0600 | [diff] [blame] | 5224 | |
| 5225 | Private libpng prototypes and macro definitions were moved from |
| 5226 | png.h and pngconf.h into a new pngpriv.h header file. |
| 5227 | |
Glenn Randers-Pehrson | 6a9c2ce | 2009-03-27 19:30:10 -0500 | [diff] [blame] | 5228 | Functions png_set_benign_errors(), png_benign_error(), and |
| 5229 | png_chunk_benign_error() were added. |
| 5230 | |
| 5231 | Support for setting the maximum amount of memory that the application |
| 5232 | will allocate for reading chunks was added, as a security measure. |
| 5233 | The functions png_set_chunk_cache_max() and png_get_chunk_cache_max() |
| 5234 | were added to the library. |
| 5235 | |
Glenn Randers-Pehrson | f210a05 | 2009-11-12 10:02:24 -0600 | [diff] [blame] | 5236 | We implemented support for I/O states by adding png_ptr member io_state |
| 5237 | and functions png_get_io_chunk_name() and png_get_io_state() in pngget.c |
Glenn Randers-Pehrson | 6a9c2ce | 2009-03-27 19:30:10 -0500 | [diff] [blame] | 5238 | |
Glenn Randers-Pehrson | 5df7edb | 2009-10-29 23:32:44 -0500 | [diff] [blame] | 5239 | We added PNG_TRANSFORM_GRAY_TO_RGB to the available high-level |
| 5240 | input transforms. |
| 5241 | |
Glenn Randers-Pehrson | 5df7edb | 2009-10-29 23:32:44 -0500 | [diff] [blame] | 5242 | Checking for and reporting of errors in the IHDR chunk is more thorough. |
| 5243 | |
Glenn Randers-Pehrson | 45af819 | 2009-12-30 08:37:29 -0600 | [diff] [blame] | 5244 | Support for global arrays was removed, to improve thread safety. |
| 5245 | |
| 5246 | Some obsolete/deprecated macros and functions have been removed. |
| 5247 | |
| 5248 | Typecasted NULL definitions such as |
| 5249 | #define png_voidp_NULL (png_voidp)NULL |
| 5250 | were eliminated. If you used these in your application, just use |
| 5251 | NULL instead. |
| 5252 | |
| 5253 | The png_struct and info_struct members "trans" and "trans_values" were |
| 5254 | changed to "trans_alpha" and "trans_color", respectively. |
| 5255 | |
| 5256 | The obsolete, unused pnggccrd.c and pngvcrd.c files and related makefiles |
Glenn Randers-Pehrson | e3f3c4e | 2010-02-07 18:08:50 -0600 | [diff] [blame] | 5257 | were removed. |
Glenn Randers-Pehrson | 45af819 | 2009-12-30 08:37:29 -0600 | [diff] [blame] | 5258 | |
| 5259 | The PNG_1_0_X and PNG_1_2_X macros were eliminated. |
| 5260 | |
Glenn Randers-Pehrson | 5df7edb | 2009-10-29 23:32:44 -0500 | [diff] [blame] | 5261 | The PNG_LEGACY_SUPPORTED macro was eliminated. |
| 5262 | |
| 5263 | Many WIN32_WCE #ifdefs were removed. |
| 5264 | |
| 5265 | The functions png_read_init(info_ptr), png_write_init(info_ptr), |
| 5266 | png_info_init(info_ptr), png_read_destroy(), and png_write_destroy() |
| 5267 | have been removed. They have been deprecated since libpng-0.95. |
| 5268 | |
Glenn Randers-Pehrson | 6a9c2ce | 2009-03-27 19:30:10 -0500 | [diff] [blame] | 5269 | The png_permit_empty_plte() was removed. It has been deprecated |
| 5270 | since libpng-1.0.9. Use png_permit_mng_features() instead. |
| 5271 | |
| 5272 | We removed the obsolete stub functions png_get_mmx_flagmask(), |
| 5273 | png_set_mmx_thresholds(), png_get_asm_flags(), |
| 5274 | png_get_mmx_bitdepth_threshold(), png_get_mmx_rowbytes_threshold(), |
| 5275 | png_set_asm_flags(), and png_mmx_supported() |
| 5276 | |
Glenn Randers-Pehrson | 45af819 | 2009-12-30 08:37:29 -0600 | [diff] [blame] | 5277 | We removed the obsolete png_check_sig(), png_memcpy_check(), and |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 5278 | png_memset_check() functions. Instead use !png_sig_cmp(), memcpy(), |
| 5279 | and memset(), respectively. |
Glenn Randers-Pehrson | 6a9c2ce | 2009-03-27 19:30:10 -0500 | [diff] [blame] | 5280 | |
Glenn Randers-Pehrson | e3f3c4e | 2010-02-07 18:08:50 -0600 | [diff] [blame] | 5281 | The function png_set_gray_1_2_4_to_8() was removed. It has been |
| 5282 | deprecated since libpng-1.0.18 and 1.2.9, when it was replaced with |
| 5283 | png_set_expand_gray_1_2_4_to_8() because the former function also |
Glenn Randers-Pehrson | c36bb79 | 2011-02-12 09:49:07 -0600 | [diff] [blame] | 5284 | expanded any tRNS chunk to an alpha channel. |
Glenn Randers-Pehrson | e3f3c4e | 2010-02-07 18:08:50 -0600 | [diff] [blame] | 5285 | |
Glenn Randers-Pehrson | 5b40b01 | 2010-11-25 07:16:29 -0600 | [diff] [blame] | 5286 | Macros for png_get_uint_16, png_get_uint_32, and png_get_int_32 |
| 5287 | were added and are used by default instead of the corresponding |
| 5288 | functions. Unfortunately, |
Glenn Randers-Pehrson | c36bb79 | 2011-02-12 09:49:07 -0600 | [diff] [blame] | 5289 | from libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the |
Glenn Randers-Pehrson | 5b40b01 | 2010-11-25 07:16:29 -0600 | [diff] [blame] | 5290 | function) incorrectly returned a value of type png_uint_32. |
| 5291 | |
Glenn Randers-Pehrson | 6a9c2ce | 2009-03-27 19:30:10 -0500 | [diff] [blame] | 5292 | We changed the prototype for png_malloc() from |
| 5293 | png_malloc(png_structp png_ptr, png_uint_32 size) |
| 5294 | to |
| 5295 | png_malloc(png_structp png_ptr, png_alloc_size_t size) |
| 5296 | |
Glenn Randers-Pehrson | e3f3c4e | 2010-02-07 18:08:50 -0600 | [diff] [blame] | 5297 | This also applies to the prototype for the user replacement malloc_fn(). |
| 5298 | |
Glenn Randers-Pehrson | 45af819 | 2009-12-30 08:37:29 -0600 | [diff] [blame] | 5299 | The png_calloc() function was added and is used in place of |
Glenn Randers-Pehrson | 2be8b64 | 2010-07-29 19:09:18 -0500 | [diff] [blame] | 5300 | of "png_malloc(); memset();" except in the case in png_read_png() |
Glenn Randers-Pehrson | 45af819 | 2009-12-30 08:37:29 -0600 | [diff] [blame] | 5301 | where the array consists of pointers; in this case a "for" loop is used |
| 5302 | after the png_malloc() to set the pointers to NULL, to give robust. |
| 5303 | behavior in case the application runs out of memory part-way through |
| 5304 | the process. |
| 5305 | |
Glenn Randers-Pehrson | 6a9c2ce | 2009-03-27 19:30:10 -0500 | [diff] [blame] | 5306 | We changed the prototypes of png_get_compression_buffer_size() and |
Cosmin Truta | a74aa9a | 2018-06-17 22:37:44 -0400 | [diff] [blame] | 5307 | png_set_compression_buffer_size() to work with size_t instead of |
Glenn Randers-Pehrson | 6a9c2ce | 2009-03-27 19:30:10 -0500 | [diff] [blame] | 5308 | png_uint_32. |
| 5309 | |
Glenn Randers-Pehrson | 45af819 | 2009-12-30 08:37:29 -0600 | [diff] [blame] | 5310 | Support for numbered error messages was removed by default, since we |
| 5311 | never got around to actually numbering the error messages. The function |
| 5312 | png_set_strip_error_numbers() was removed from the library by default. |
| 5313 | |
| 5314 | The png_zalloc() and png_zfree() functions are no longer exported. |
Glenn Randers-Pehrson | 6a9c2ce | 2009-03-27 19:30:10 -0500 | [diff] [blame] | 5315 | The png_zalloc() function no longer zeroes out the memory that it |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 5316 | allocates. Applications that called png_zalloc(png_ptr, number, size) |
| 5317 | can call png_calloc(png_ptr, number*size) instead, and can call |
| 5318 | png_free() instead of png_zfree(). |
Glenn Randers-Pehrson | 6a9c2ce | 2009-03-27 19:30:10 -0500 | [diff] [blame] | 5319 | |
Glenn Randers-Pehrson | 3cd7cff | 2010-04-16 19:27:08 -0500 | [diff] [blame] | 5320 | Support for dithering was disabled by default in libpng-1.4.0, because |
Glenn Randers-Pehrson | 9f1cd70 | 2011-04-16 19:40:23 -0500 | [diff] [blame] | 5321 | it has not been well tested and doesn't actually "dither". |
| 5322 | The code was not |
Glenn Randers-Pehrson | 3cd7cff | 2010-04-16 19:27:08 -0500 | [diff] [blame] | 5323 | removed, however, and could be enabled by building libpng with |
| 5324 | PNG_READ_DITHER_SUPPORTED defined. In libpng-1.4.2, this support |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5325 | was re-enabled, but the function was renamed png_set_quantize() to |
Glenn Randers-Pehrson | 3cd7cff | 2010-04-16 19:27:08 -0500 | [diff] [blame] | 5326 | reflect more accurately what it actually does. At the same time, |
| 5327 | the PNG_DITHER_[RED,GREEN_BLUE]_BITS macros were also renamed to |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 5328 | PNG_QUANTIZE_[RED,GREEN,BLUE]_BITS, and PNG_READ_DITHER_SUPPORTED |
| 5329 | was renamed to PNG_READ_QUANTIZE_SUPPORTED. |
Glenn Randers-Pehrson | 6098807 | 2010-04-13 22:11:06 -0500 | [diff] [blame] | 5330 | |
Glenn Randers-Pehrson | 6a9c2ce | 2009-03-27 19:30:10 -0500 | [diff] [blame] | 5331 | We removed the trailing '.' from the warning and error messages. |
| 5332 | |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 5333 | .SH XI. Changes to Libpng from version 1.4.x to 1.5.x |
Glenn Randers-Pehrson | 5b40b01 | 2010-11-25 07:16:29 -0600 | [diff] [blame] | 5334 | |
Glenn Randers-Pehrson | c36bb79 | 2011-02-12 09:49:07 -0600 | [diff] [blame] | 5335 | From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the |
Glenn Randers-Pehrson | 5b40b01 | 2010-11-25 07:16:29 -0600 | [diff] [blame] | 5336 | function) incorrectly returned a value of type png_uint_32. |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5337 | The incorrect macro was removed from libpng-1.4.5. |
Glenn Randers-Pehrson | 5b40b01 | 2010-11-25 07:16:29 -0600 | [diff] [blame] | 5338 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5339 | Checking for invalid palette index on write was added at libpng |
| 5340 | 1.5.10. If a pixel contains an invalid (out-of-range) index libpng issues |
| 5341 | a benign error. This is enabled by default because this condition is an |
| 5342 | error according to the PNG specification, Clause 11.3.2, but the error can |
| 5343 | be ignored in each png_ptr with |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 5344 | |
| 5345 | png_set_check_for_invalid_index(png_ptr, allowed); |
| 5346 | |
| 5347 | allowed - one of |
| 5348 | 0: disable benign error (accept the |
| 5349 | invalid data without warning). |
| 5350 | 1: enable benign error (treat the |
| 5351 | invalid data as an error or a |
| 5352 | warning). |
| 5353 | |
| 5354 | If the error is ignored, or if png_benign_error() treats it as a warning, |
| 5355 | any invalid pixels are decoded as opaque black by the decoder and written |
| 5356 | as-is by the encoder. |
| 5357 | |
| 5358 | Retrieving the maximum palette index found was added at libpng-1.5.15. |
| 5359 | This statement must appear after png_read_png() or png_read_image() while |
| 5360 | reading, and after png_write_png() or png_write_image() while writing. |
| 5361 | |
| 5362 | int max_palette = png_get_palette_max(png_ptr, info_ptr); |
| 5363 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5364 | This will return the maximum palette index found in the image, or "\-1" if |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 5365 | the palette was not checked, or "0" if no palette was found. Note that this |
| 5366 | does not account for any palette index used by ancillary chunks such as the |
| 5367 | bKGD chunk; you must check those separately to determine the maximum |
| 5368 | palette index actually used. |
| 5369 | |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 5370 | There are no substantial API changes between the non-deprecated parts of |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 5371 | the 1.4.5 API and the 1.5.0 API; however, the ability to directly access |
Glenn Randers-Pehrson | 5a956a7 | 2011-12-22 14:23:37 -0600 | [diff] [blame] | 5372 | members of the main libpng control structures, png_struct and png_info, |
| 5373 | deprecated in earlier versions of libpng, has been completely removed from |
Glenn Randers-Pehrson | 05591ab | 2016-01-30 10:08:47 -0600 | [diff] [blame] | 5374 | libpng 1.5, and new private "pngstruct.h", "pnginfo.h", and "pngdebug.h" |
| 5375 | header files were created. |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 5376 | |
Glenn Randers-Pehrson | 5a956a7 | 2011-12-22 14:23:37 -0600 | [diff] [blame] | 5377 | We no longer include zlib.h in png.h. The include statement has been moved |
| 5378 | to pngstruct.h, where it is not accessible by applications. Applications that |
| 5379 | need access to information in zlib.h will need to add the '#include "zlib.h"' |
| 5380 | directive. It does not matter whether this is placed prior to or after |
Glenn Randers-Pehrson | 00879b1 | 2011-01-15 19:25:34 -0600 | [diff] [blame] | 5381 | the '"#include png.h"' directive. |
| 5382 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 5383 | The png_sprintf(), png_strcpy(), and png_strncpy() macros are no longer used |
| 5384 | and were removed. |
| 5385 | |
| 5386 | We moved the png_strlen(), png_memcpy(), png_memset(), and png_memcmp() |
| 5387 | macros into a private header file (pngpriv.h) that is not accessible to |
| 5388 | applications. |
Glenn Randers-Pehrson | 00879b1 | 2011-01-15 19:25:34 -0600 | [diff] [blame] | 5389 | |
Glenn Randers-Pehrson | 9d23b40 | 2011-01-08 10:42:01 -0600 | [diff] [blame] | 5390 | In png_get_iCCP, the type of "profile" was changed from png_charpp |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 5391 | to png_bytepp, and in png_set_iCCP, from png_charp to png_const_bytep. |
Glenn Randers-Pehrson | 9d23b40 | 2011-01-08 10:42:01 -0600 | [diff] [blame] | 5392 | |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 5393 | There are changes of form in png.h, including new and changed macros to |
Glenn Randers-Pehrson | 95ba417 | 2011-09-08 12:21:42 -0500 | [diff] [blame] | 5394 | declare parts of the API. Some API functions with arguments that are |
| 5395 | pointers to data not modified within the function have been corrected to |
Cosmin Truta | 1ef8882 | 2018-08-18 21:01:02 -0400 | [diff] [blame] | 5396 | declare these arguments with const. |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 5397 | |
| 5398 | Much of the internal use of C macros to control the library build has also |
| 5399 | changed and some of this is visible in the exported header files, in |
| 5400 | particular the use of macros to control data and API elements visible |
| 5401 | during application compilation may require significant revision to |
| 5402 | application code. (It is extremely rare for an application to do this.) |
| 5403 | |
| 5404 | Any program that compiled against libpng 1.4 and did not use deprecated |
| 5405 | features or access internal library structures should compile and work |
Glenn Randers-Pehrson | d08b6bd | 2011-02-19 15:50:17 -0600 | [diff] [blame] | 5406 | against libpng 1.5, except for the change in the prototype for |
| 5407 | png_get_iCCP() and png_set_iCCP() API functions mentioned above. |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 5408 | |
Glenn Randers-Pehrson | 6e97410 | 2010-12-19 16:44:22 -0600 | [diff] [blame] | 5409 | libpng 1.5.0 adds PNG_ PASS macros to help in the reading and writing of |
| 5410 | interlaced images. The macros return the number of rows and columns in |
| 5411 | each pass and information that can be used to de-interlace and (if |
| 5412 | absolutely necessary) interlace an image. |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 5413 | |
| 5414 | libpng 1.5.0 adds an API png_longjmp(png_ptr, value). This API calls |
Glenn Randers-Pehrson | d08b6bd | 2011-02-19 15:50:17 -0600 | [diff] [blame] | 5415 | the application-provided png_longjmp_ptr on the internal, but application |
Glenn Randers-Pehrson | 33ced44 | 2011-04-27 14:58:06 -0500 | [diff] [blame] | 5416 | initialized, longjmp buffer. It is provided as a convenience to avoid |
| 5417 | the need to use the png_jmpbuf macro, which had the unnecessary side |
| 5418 | effect of resetting the internal png_longjmp_ptr value. |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 5419 | |
| 5420 | libpng 1.5.0 includes a complete fixed point API. By default this is |
| 5421 | present along with the corresponding floating point API. In general the |
| 5422 | fixed point API is faster and smaller than the floating point one because |
| 5423 | the PNG file format used fixed point, not floating point. This applies |
| 5424 | even if the library uses floating point in internal calculations. A new |
| 5425 | macro, PNG_FLOATING_ARITHMETIC_SUPPORTED, reveals whether the library |
| 5426 | uses floating point arithmetic (the default) or fixed point arithmetic |
| 5427 | internally for performance critical calculations such as gamma correction. |
Glenn Randers-Pehrson | 00879b1 | 2011-01-15 19:25:34 -0600 | [diff] [blame] | 5428 | In some cases, the gamma calculations may produce slightly different |
| 5429 | results. This has changed the results in png_rgb_to_gray and in alpha |
| 5430 | composition (png_set_background for example). This applies even if the |
| 5431 | original image was already linear (gamma == 1.0) and, therefore, it is |
| 5432 | not necessary to linearize the image. This is because libpng has *not* |
| 5433 | been changed to optimize that case correctly, yet. |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 5434 | |
| 5435 | Fixed point support for the sCAL chunk comes with an important caveat; |
| 5436 | the sCAL specification uses a decimal encoding of floating point values |
| 5437 | and the accuracy of PNG fixed point values is insufficient for |
| 5438 | representation of these values. Consequently a "string" API |
| 5439 | (png_get_sCAL_s and png_set_sCAL_s) is the only reliable way of reading |
| 5440 | arbitrary sCAL chunks in the absence of either the floating point API or |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5441 | internal floating point calculations. Starting with libpng-1.5.0, both |
| 5442 | of these functions are present when PNG_sCAL_SUPPORTED is defined. Prior |
| 5443 | to libpng-1.5.0, their presence also depended upon PNG_FIXED_POINT_SUPPORTED |
| 5444 | being defined and PNG_FLOATING_POINT_SUPPORTED not being defined. |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 5445 | |
| 5446 | Applications no longer need to include the optional distribution header |
| 5447 | file pngusr.h or define the corresponding macros during application |
| 5448 | build in order to see the correct variant of the libpng API. From 1.5.0 |
| 5449 | application code can check for the corresponding _SUPPORTED macro: |
| 5450 | |
| 5451 | #ifdef PNG_INCH_CONVERSIONS_SUPPORTED |
| 5452 | /* code that uses the inch conversion APIs. */ |
| 5453 | #endif |
| 5454 | |
| 5455 | This macro will only be defined if the inch conversion functions have been |
| 5456 | compiled into libpng. The full set of macros, and whether or not support |
| 5457 | has been compiled in, are available in the header file pnglibconf.h. |
| 5458 | This header file is specific to the libpng build. Notice that prior to |
| 5459 | 1.5.0 the _SUPPORTED macros would always have the default definition unless |
| 5460 | reset by pngusr.h or by explicit settings on the compiler command line. |
| 5461 | These settings may produce compiler warnings or errors in 1.5.0 because |
| 5462 | of macro redefinition. |
| 5463 | |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 5464 | Applications can now choose whether to use these macros or to call the |
| 5465 | corresponding function by defining PNG_USE_READ_MACROS or |
| 5466 | PNG_NO_USE_READ_MACROS before including png.h. Notice that this is |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5467 | only supported from 1.5.0; defining PNG_NO_USE_READ_MACROS prior to 1.5.0 |
Glenn Randers-Pehrson | 95ba417 | 2011-09-08 12:21:42 -0500 | [diff] [blame] | 5468 | will lead to a link failure. |
Glenn Randers-Pehrson | 59fa3e9 | 2011-01-06 07:07:06 -0600 | [diff] [blame] | 5469 | |
Glenn Randers-Pehrson | 733b131 | 2011-06-15 13:21:01 -0500 | [diff] [blame] | 5470 | Prior to libpng-1.5.4, the zlib compressor used the same set of parameters |
Glenn Randers-Pehrson | 8eb8833 | 2011-04-01 00:16:50 -0500 | [diff] [blame] | 5471 | when compressing the IDAT data and textual data such as zTXt and iCCP. |
Glenn Randers-Pehrson | 733b131 | 2011-06-15 13:21:01 -0500 | [diff] [blame] | 5472 | In libpng-1.5.4 we reinitialized the zlib stream for each type of data. |
Glenn Randers-Pehrson | 8eb8833 | 2011-04-01 00:16:50 -0500 | [diff] [blame] | 5473 | We added five png_set_text_*() functions for setting the parameters to |
| 5474 | use with textual data. |
| 5475 | |
Glenn Randers-Pehrson | 733b131 | 2011-06-15 13:21:01 -0500 | [diff] [blame] | 5476 | Prior to libpng-1.5.4, the PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED |
John Bowler | b2bee33 | 2011-06-10 23:24:58 -0500 | [diff] [blame] | 5477 | option was off by default, and slightly inaccurate scaling occurred. |
Glenn Randers-Pehrson | fb29e51 | 2011-06-17 20:38:24 -0500 | [diff] [blame] | 5478 | This option can no longer be turned off, and the choice of accurate |
| 5479 | or inaccurate 16-to-8 scaling is by using the new png_set_scale_16_to_8() |
| 5480 | API for accurate scaling or the old png_set_strip_16_to_8() API for simple |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5481 | chopping. In libpng-1.5.4, the PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED |
| 5482 | macro became PNG_READ_SCALE_16_TO_8_SUPPORTED, and the PNG_READ_16_TO_8 |
| 5483 | macro became PNG_READ_STRIP_16_TO_8_SUPPORTED, to enable the two |
| 5484 | png_set_*_16_to_8() functions separately. |
Glenn Randers-Pehrson | 0cb906d | 2011-06-11 14:22:22 -0500 | [diff] [blame] | 5485 | |
Glenn Randers-Pehrson | 733b131 | 2011-06-15 13:21:01 -0500 | [diff] [blame] | 5486 | Prior to libpng-1.5.4, the png_set_user_limits() function could only be |
Glenn Randers-Pehrson | 0cb906d | 2011-06-11 14:22:22 -0500 | [diff] [blame] | 5487 | used to reduce the width and height limits from the value of |
| 5488 | PNG_USER_WIDTH_MAX and PNG_USER_HEIGHT_MAX, although this document said |
| 5489 | that it could be used to override them. Now this function will reduce or |
| 5490 | increase the limits. |
John Bowler | b2bee33 | 2011-06-10 23:24:58 -0500 | [diff] [blame] | 5491 | |
Glenn Randers-Pehrson | 60d8ae1 | 2017-04-22 15:44:55 -0500 | [diff] [blame] | 5492 | Starting in libpng-1.5.22, default user limits were established. These |
| 5493 | can be overridden by application calls to png_set_user_limits(), |
| 5494 | png_set_user_chunk_cache_max(), and/or png_set_user_malloc_max(). |
| 5495 | The limits are now |
| 5496 | max possible default |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 5497 | png_user_width_max 0x7fffffff 1,000,000 |
| 5498 | png_user_height_max 0x7fffffff 1,000,000 |
Glenn Randers-Pehrson | 60d8ae1 | 2017-04-22 15:44:55 -0500 | [diff] [blame] | 5499 | png_user_chunk_cache_max 0 (unlimited) 1000 |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 5500 | png_user_chunk_malloc_max 0 (unlimited) 8,000,000 |
| 5501 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5502 | The png_set_option() function (and the "options" member of the png struct) was |
Glenn Randers-Pehrson | efe4e5d | 2015-09-23 22:08:04 -0500 | [diff] [blame] | 5503 | added to libpng-1.5.15, with option PNG_ARM_NEON. |
| 5504 | |
Glenn Randers-Pehrson | 2ca2a0b | 2014-03-16 21:47:52 -0500 | [diff] [blame] | 5505 | The library now supports a complete fixed point implementation and can |
| 5506 | thus be used on systems that have no floating point support or very |
| 5507 | limited or slow support. Previously gamma correction, an essential part |
| 5508 | of complete PNG support, required reasonably fast floating point. |
| 5509 | |
| 5510 | As part of this the choice of internal implementation has been made |
| 5511 | independent of the choice of fixed versus floating point APIs and all the |
| 5512 | missing fixed point APIs have been implemented. |
| 5513 | |
| 5514 | The exact mechanism used to control attributes of API functions has |
| 5515 | changed, as described in the INSTALL file. |
| 5516 | |
Glenn Randers-Pehrson | c2a15d0 | 2014-03-16 19:53:29 -0500 | [diff] [blame] | 5517 | A new test program, pngvalid, is provided in addition to pngtest. |
| 5518 | pngvalid validates the arithmetic accuracy of the gamma correction |
| 5519 | calculations and includes a number of validations of the file format. |
| 5520 | A subset of the full range of tests is run when "make check" is done |
| 5521 | (in the 'configure' build.) pngvalid also allows total allocated memory |
| 5522 | usage to be evaluated and performs additional memory overwrite validation. |
| 5523 | |
| 5524 | Many changes to individual feature macros have been made. The following |
| 5525 | are the changes most likely to be noticed by library builders who |
| 5526 | configure libpng: |
| 5527 | |
| 5528 | 1) All feature macros now have consistent naming: |
| 5529 | |
| 5530 | #define PNG_NO_feature turns the feature off |
| 5531 | #define PNG_feature_SUPPORTED turns the feature on |
| 5532 | |
| 5533 | pnglibconf.h contains one line for each feature macro which is either: |
| 5534 | |
| 5535 | #define PNG_feature_SUPPORTED |
| 5536 | |
| 5537 | if the feature is supported or: |
| 5538 | |
| 5539 | /*#undef PNG_feature_SUPPORTED*/ |
| 5540 | |
| 5541 | if it is not. Library code consistently checks for the 'SUPPORTED' macro. |
| 5542 | It does not, and libpng applications should not, check for the 'NO' macro |
| 5543 | which will not normally be defined even if the feature is not supported. |
| 5544 | The 'NO' macros are only used internally for setting or not setting the |
| 5545 | corresponding 'SUPPORTED' macros. |
| 5546 | |
| 5547 | Compatibility with the old names is provided as follows: |
| 5548 | |
| 5549 | PNG_INCH_CONVERSIONS turns on PNG_INCH_CONVERSIONS_SUPPORTED |
| 5550 | |
| 5551 | And the following definitions disable the corresponding feature: |
| 5552 | |
| 5553 | PNG_SETJMP_NOT_SUPPORTED disables SETJMP |
| 5554 | PNG_READ_TRANSFORMS_NOT_SUPPORTED disables READ_TRANSFORMS |
| 5555 | PNG_NO_READ_COMPOSITED_NODIV disables READ_COMPOSITE_NODIV |
| 5556 | PNG_WRITE_TRANSFORMS_NOT_SUPPORTED disables WRITE_TRANSFORMS |
| 5557 | PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED disables READ_ANCILLARY_CHUNKS |
| 5558 | PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED disables WRITE_ANCILLARY_CHUNKS |
| 5559 | |
| 5560 | Library builders should remove use of the above, inconsistent, names. |
| 5561 | |
| 5562 | 2) Warning and error message formatting was previously conditional on |
| 5563 | the STDIO feature. The library has been changed to use the |
| 5564 | CONSOLE_IO feature instead. This means that if CONSOLE_IO is disabled |
| 5565 | the library no longer uses the printf(3) functions, even though the |
| 5566 | default read/write implementations use (FILE) style stdio.h functions. |
| 5567 | |
| 5568 | 3) Three feature macros now control the fixed/floating point decisions: |
| 5569 | |
| 5570 | PNG_FLOATING_POINT_SUPPORTED enables the floating point APIs |
| 5571 | |
| 5572 | PNG_FIXED_POINT_SUPPORTED enables the fixed point APIs; however, in |
| 5573 | practice these are normally required internally anyway (because the PNG |
| 5574 | file format is fixed point), therefore in most cases PNG_NO_FIXED_POINT |
| 5575 | merely stops the function from being exported. |
| 5576 | |
| 5577 | PNG_FLOATING_ARITHMETIC_SUPPORTED chooses between the internal floating |
| 5578 | point implementation or the fixed point one. Typically the fixed point |
| 5579 | implementation is larger and slower than the floating point implementation |
| 5580 | on a system that supports floating point; however, it may be faster on a |
| 5581 | system which lacks floating point hardware and therefore uses a software |
| 5582 | emulation. |
| 5583 | |
| 5584 | 4) Added PNG_{READ,WRITE}_INT_FUNCTIONS_SUPPORTED. This allows the |
| 5585 | functions to read and write ints to be disabled independently of |
| 5586 | PNG_USE_READ_MACROS, which allows libpng to be built with the functions |
| 5587 | even though the default is to use the macros - this allows applications |
| 5588 | to choose at app buildtime whether or not to use macros (previously |
| 5589 | impossible because the functions weren't in the default build.) |
| 5590 | |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 5591 | .SH XII. Changes to Libpng from version 1.5.x to 1.6.x |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 5592 | |
| 5593 | A "simplified API" has been added (see documentation in png.h and a simple |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 5594 | example in contrib/examples/pngtopng.c). The new publicly visible API |
| 5595 | includes the following: |
| 5596 | |
| 5597 | macros: |
| 5598 | PNG_FORMAT_* |
| 5599 | PNG_IMAGE_* |
| 5600 | structures: |
| 5601 | png_control |
| 5602 | png_image |
| 5603 | read functions |
| 5604 | png_image_begin_read_from_file() |
| 5605 | png_image_begin_read_from_stdio() |
| 5606 | png_image_begin_read_from_memory() |
| 5607 | png_image_finish_read() |
| 5608 | png_image_free() |
| 5609 | write functions |
| 5610 | png_image_write_to_file() |
Glenn Randers-Pehrson | d2b8d46 | 2016-01-23 14:01:44 -0600 | [diff] [blame] | 5611 | png_image_write_to_memory() |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 5612 | png_image_write_to_stdio() |
| 5613 | |
| 5614 | Starting with libpng-1.6.0, you can configure libpng to prefix all exported |
| 5615 | symbols, using the PNG_PREFIX macro. |
Glenn Randers-Pehrson | 5bffd6c | 2012-01-31 22:21:32 -0600 | [diff] [blame] | 5616 | |
Glenn Randers-Pehrson | 5a956a7 | 2011-12-22 14:23:37 -0600 | [diff] [blame] | 5617 | We no longer include string.h in png.h. The include statement has been moved |
| 5618 | to pngpriv.h, where it is not accessible by applications. Applications that |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5619 | need access to information in string.h must add an '#include <string.h>' |
Glenn Randers-Pehrson | 5a956a7 | 2011-12-22 14:23:37 -0600 | [diff] [blame] | 5620 | directive. It does not matter whether this is placed prior to or after |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5621 | the '#include "png.h"' directive. |
Glenn Randers-Pehrson | 5a956a7 | 2011-12-22 14:23:37 -0600 | [diff] [blame] | 5622 | |
| 5623 | The following API are now DEPRECATED: |
| 5624 | png_info_init_3() |
| 5625 | png_convert_to_rfc1123() which has been replaced |
| 5626 | with png_convert_to_rfc1123_buffer() |
| 5627 | png_malloc_default() |
| 5628 | png_free_default() |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 5629 | png_reset_zstream() |
Glenn Randers-Pehrson | 5a956a7 | 2011-12-22 14:23:37 -0600 | [diff] [blame] | 5630 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5631 | The following have been removed: |
Glenn Randers-Pehrson | 5a956a7 | 2011-12-22 14:23:37 -0600 | [diff] [blame] | 5632 | png_get_io_chunk_name(), which has been replaced |
| 5633 | with png_get_io_chunk_type(). The new |
| 5634 | function returns a 32-bit integer instead of |
| 5635 | a string. |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 5636 | The png_sizeof(), png_strlen(), png_memcpy(), png_memcmp(), and |
| 5637 | png_memset() macros are no longer used in the libpng sources and |
| 5638 | have been removed. These had already been made invisible to applications |
| 5639 | (i.e., defined in the private pngpriv.h header file) since libpng-1.5.0. |
| 5640 | |
| 5641 | The signatures of many exported functions were changed, such that |
| 5642 | png_structp became png_structrp or png_const_structrp |
| 5643 | png_infop became png_inforp or png_const_inforp |
| 5644 | where "rp" indicates a "restricted pointer". |
| 5645 | |
Glenn Randers-Pehrson | b9ba8d6 | 2015-08-16 23:32:04 -0500 | [diff] [blame] | 5646 | Dropped support for 16-bit platforms. The support for FAR/far types has |
| 5647 | been eliminated and the definition of png_alloc_size_t is now controlled |
| 5648 | by a flag so that 'small size_t' systems can select it if necessary. |
Glenn Randers-Pehrson | 3645008 | 2015-03-09 09:13:58 -0500 | [diff] [blame] | 5649 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 5650 | Error detection in some chunks has improved; in particular the iCCP chunk |
| 5651 | reader now does pretty complete validation of the basic format. Some bad |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5652 | profiles that were previously accepted are now accepted with a warning or |
Glenn Randers-Pehrson | f43b5e3 | 2014-12-20 19:10:52 -0600 | [diff] [blame] | 5653 | rejected, depending upon the png_set_benign_errors() setting, in particular |
| 5654 | the very old broken Microsoft/HP 3144-byte sRGB profile. Starting with |
Glenn Randers-Pehrson | e95ce2c | 2014-05-07 12:07:12 -0500 | [diff] [blame] | 5655 | libpng-1.6.11, recognizing and checking sRGB profiles can be avoided by |
| 5656 | means of |
| 5657 | |
Glenn Randers-Pehrson | 91319c6 | 2014-07-04 11:46:17 -0500 | [diff] [blame] | 5658 | #if defined(PNG_SKIP_sRGB_CHECK_PROFILE) && \ |
| 5659 | defined(PNG_SET_OPTION_SUPPORTED) |
Glenn Randers-Pehrson | e429c66 | 2014-06-11 20:35:18 -0500 | [diff] [blame] | 5660 | png_set_option(png_ptr, PNG_SKIP_sRGB_CHECK_PROFILE, |
Glenn Randers-Pehrson | 5808e7b | 2014-05-19 18:10:56 -0500 | [diff] [blame] | 5661 | PNG_OPTION_ON); |
| 5662 | #endif |
Glenn Randers-Pehrson | e95ce2c | 2014-05-07 12:07:12 -0500 | [diff] [blame] | 5663 | |
Glenn Randers-Pehrson | 60a7506 | 2015-02-18 12:24:46 -0600 | [diff] [blame] | 5664 | It's not a good idea to do this if you are using the "simplified API", |
Glenn Randers-Pehrson | f43b5e3 | 2014-12-20 19:10:52 -0600 | [diff] [blame] | 5665 | which needs to be able to recognize sRGB profiles conveyed via the iCCP |
Glenn Randers-Pehrson | d1c5f48 | 2014-05-09 21:06:27 -0500 | [diff] [blame] | 5666 | chunk. |
| 5667 | |
Glenn Randers-Pehrson | e95ce2c | 2014-05-07 12:07:12 -0500 | [diff] [blame] | 5668 | The PNG spec requirement that only grayscale profiles may appear in images |
| 5669 | with color type 0 or 4 and that even if the image only contains gray pixels, |
| 5670 | only RGB profiles may appear in images with color type 2, 3, or 6, is now |
| 5671 | enforced. The sRGB chunk is allowed to appear in images with any color type |
Glenn Randers-Pehrson | 91319c6 | 2014-07-04 11:46:17 -0500 | [diff] [blame] | 5672 | and is interpreted by libpng to convey a one-tracer-curve gray profile or a |
| 5673 | three-tracer-curve RGB profile as appropriate. |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5674 | |
Glenn Randers-Pehrson | 092b8d7 | 2016-01-04 08:15:11 -0600 | [diff] [blame] | 5675 | Libpng 1.5.x erroneously used /MD for Debug DLL builds; if you used the debug |
| 5676 | builds in your app and you changed your app to use /MD you will need to |
| 5677 | change it back to /MDd for libpng 1.6.x. |
| 5678 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5679 | Prior to libpng-1.6.0 a warning would be issued if the iTXt chunk contained |
| 5680 | an empty language field or an empty translated keyword. Both of these |
| 5681 | are allowed by the PNG specification, so these warnings are no longer issued. |
| 5682 | |
| 5683 | The library now issues an error if the application attempts to set a |
| 5684 | transform after it calls png_read_update_info() or if it attempts to call |
| 5685 | both png_read_update_info() and png_start_read_image() or to call either |
| 5686 | of them more than once. |
| 5687 | |
| 5688 | The default condition for benign_errors is now to treat benign errors as |
| 5689 | warnings while reading and as errors while writing. |
Glenn Randers-Pehrson | d5dd93f | 2013-07-02 09:20:36 -0500 | [diff] [blame] | 5690 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 5691 | The library now issues a warning if both background processing and RGB to |
| 5692 | gray are used when gamma correction happens. As with previous versions of |
| 5693 | the library the results are numerically very incorrect in this case. |
| 5694 | |
| 5695 | There are some minor arithmetic changes in some transforms such as |
| 5696 | png_set_background(), that might be detected by certain regression tests. |
| 5697 | |
| 5698 | Unknown chunk handling has been improved internally, without any API change. |
| 5699 | This adds more correct option control of the unknown handling, corrects |
| 5700 | a pre-existing bug where the per-chunk 'keep' setting is ignored, and makes |
| 5701 | it possible to skip IDAT chunks in the sequential reader. |
| 5702 | |
| 5703 | The machine-generated configure files are no longer included in branches |
| 5704 | libpng16 and later of the GIT repository. They continue to be included |
| 5705 | in the tarball releases, however. |
Glenn Randers-Pehrson | 8064777 | 2013-02-04 19:50:56 -0600 | [diff] [blame] | 5706 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5707 | Libpng-1.6.0 through 1.6.2 used the CMF bytes at the beginning of the IDAT |
| 5708 | stream to set the size of the sliding window for reading instead of using the |
| 5709 | default 32-kbyte sliding window size. It was discovered that there are |
| 5710 | hundreds of PNG files in the wild that have incorrect CMF bytes that caused |
Glenn Randers-Pehrson | 72855fb | 2014-04-13 21:27:25 -0500 | [diff] [blame] | 5711 | zlib to issue the "invalid distance too far back" error and reject the file. |
| 5712 | Libpng-1.6.3 and later calculate their own safe CMF from the image dimensions, |
| 5713 | provide a way to revert to the libpng-1.5.x behavior (ignoring the CMF bytes |
| 5714 | and using a 32-kbyte sliding window), by using |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5715 | |
| 5716 | png_set_option(png_ptr, PNG_MAXIMUM_INFLATE_WINDOW, |
| 5717 | PNG_OPTION_ON); |
| 5718 | |
Glenn Randers-Pehrson | 72855fb | 2014-04-13 21:27:25 -0500 | [diff] [blame] | 5719 | and provide a tool (contrib/tools/pngfix) for rewriting a PNG file while |
| 5720 | optimizing the CMF bytes in its IDAT chunk correctly. |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5721 | |
| 5722 | Libpng-1.6.0 and libpng-1.6.1 wrote uncompressed iTXt chunks with the wrong |
| 5723 | length, which resulted in PNG files that cannot be read beyond the bad iTXt |
| 5724 | chunk. This error was fixed in libpng-1.6.3, and a tool (called |
| 5725 | contrib/tools/png-fix-itxt) has been added to the libpng distribution. |
| 5726 | |
Glenn Randers-Pehrson | 2d06983 | 2015-05-06 20:31:21 -0500 | [diff] [blame] | 5727 | Starting with libpng-1.6.17, the PNG_SAFE_LIMITS macro was eliminated |
| 5728 | and safe limits are used by default (users who need larger limits |
| 5729 | can still override them at compile time or run time, as described above). |
| 5730 | |
| 5731 | The new limits are |
| 5732 | default spec limit |
| 5733 | png_user_width_max 1,000,000 2,147,483,647 |
| 5734 | png_user_height_max 1,000,000 2,147,483,647 |
| 5735 | png_user_chunk_cache_max 128 unlimited |
| 5736 | png_user_chunk_malloc_max 8,000,000 unlimited |
| 5737 | |
| 5738 | Starting with libpng-1.6.18, a PNG_RELEASE_BUILD macro was added, which allows |
| 5739 | library builders to control compilation for an installed system (a release build). |
| 5740 | It can be set for testing debug or beta builds to ensure that they will compile |
| 5741 | when the build type is switched to RC or STABLE. In essence this overrides the |
| 5742 | PNG_LIBPNG_BUILD_BASE_TYPE definition which is not directly user controllable. |
| 5743 | |
Glenn Randers-Pehrson | a901eb3 | 2015-10-30 07:57:49 -0500 | [diff] [blame] | 5744 | Starting with libpng-1.6.19, attempting to set an over-length PLTE chunk |
Glenn Randers-Pehrson | 81f4466 | 2015-10-29 09:26:41 -0500 | [diff] [blame] | 5745 | is an error. Previously this requirement of the PNG specification was not |
Glenn Randers-Pehrson | b00d986 | 2015-10-31 08:55:50 -0500 | [diff] [blame] | 5746 | enforced, and the palette was always limited to 256 entries. An over-length |
| 5747 | PLTE chunk found in an input PNG is silently truncated. |
Glenn Randers-Pehrson | 81f4466 | 2015-10-29 09:26:41 -0500 | [diff] [blame] | 5748 | |
Glenn Randers-Pehrson | 68cb0aa | 2017-07-13 11:19:53 -0500 | [diff] [blame] | 5749 | Starting with libpng-1.6.31, the eXIf chunk is supported. Libpng does not |
| 5750 | attempt to decode the Exif profile; it simply returns a byte array |
| 5751 | containing the profile to the calling application which must do its own |
| 5752 | decoding. |
| 5753 | |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 5754 | .SH XIII. Detecting libpng |
Glenn Randers-Pehrson | 424c985 | 2009-06-02 13:45:15 -0500 | [diff] [blame] | 5755 | |
| 5756 | The png_get_io_ptr() function has been present since libpng-0.88, has never |
| 5757 | changed, and is unaffected by conditional compilation macros. It is the |
| 5758 | best choice for use in configure scripts for detecting the presence of any |
Glenn Randers-Pehrson | 99708d5 | 2009-06-29 17:30:00 -0500 | [diff] [blame] | 5759 | libpng version since 0.88. In an autoconf "configure.in" you could use |
| 5760 | |
| 5761 | AC_CHECK_LIB(png, png_get_io_ptr, ... |
Glenn Randers-Pehrson | 424c985 | 2009-06-02 13:45:15 -0500 | [diff] [blame] | 5762 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 5763 | .SH XV. Source code repository |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 5764 | |
| 5765 | Since about February 2009, version 1.2.34, libpng has been under "git" source |
| 5766 | control. The git repository was built from old libpng-x.y.z.tar.gz files |
| 5767 | going back to version 0.70. You can access the git repository (read only) |
| 5768 | at |
| 5769 | |
Glenn Randers-Pehrson | 774922d | 2017-05-27 12:33:48 -0500 | [diff] [blame] | 5770 | https://github.com/glennrp/libpng or |
| 5771 | https://git.code.sf.net/p/libpng/code.git |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 5772 | |
Glenn Randers-Pehrson | 774922d | 2017-05-27 12:33:48 -0500 | [diff] [blame] | 5773 | or you can browse it with a web browser at |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 5774 | |
Glenn Randers-Pehrson | 774922d | 2017-05-27 12:33:48 -0500 | [diff] [blame] | 5775 | https://github.com/glennrp/libpng or |
| 5776 | https://sourceforge.net/p/libpng/code/ci/libpng16/tree/ |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 5777 | |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 5778 | Patches can be sent to png-mng-implement at lists.sourceforge.net or |
| 5779 | uploaded to the libpng bug tracker at |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 5780 | |
Glenn Randers-Pehrson | 64f8110 | 2017-04-03 15:25:40 -0500 | [diff] [blame] | 5781 | https://libpng.sourceforge.io/ |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 5782 | |
Glenn Randers-Pehrson | 11629b1 | 2017-05-27 13:12:37 -0500 | [diff] [blame] | 5783 | or as a "pull request" to |
| 5784 | |
| 5785 | https://github.com/glennrp/libpng/pulls |
| 5786 | |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 5787 | We also accept patches built from the tar or zip distributions, and |
luz.paz | eb91c0e | 2018-02-09 06:57:29 -0500 | [diff] [blame] | 5788 | simple verbal descriptions of bug fixes, reported either to the |
Glenn Randers-Pehrson | a5e5547 | 2011-07-12 10:13:32 -0500 | [diff] [blame] | 5789 | SourceForge bug tracker, to the png-mng-implement at lists.sf.net |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 5790 | mailing list, as github issues. |
Glenn Randers-Pehrson | 7bc2501 | 2011-01-21 23:29:09 -0600 | [diff] [blame] | 5791 | |
Glenn Randers-Pehrson | 0501c1c | 2012-01-11 14:00:52 -0600 | [diff] [blame] | 5792 | .SH XV. Coding style |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 5793 | |
Glenn Randers-Pehrson | c4b3718 | 2014-04-06 08:59:57 -0500 | [diff] [blame] | 5794 | Our coding style is similar to the "Allman" style |
Glenn Randers-Pehrson | 64f8110 | 2017-04-03 15:25:40 -0500 | [diff] [blame] | 5795 | (See https://en.wikipedia.org/wiki/Indent_style#Allman_style), with curly |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 5796 | braces on separate lines: |
| 5797 | |
| 5798 | if (condition) |
| 5799 | { |
| 5800 | action; |
| 5801 | } |
| 5802 | |
| 5803 | else if (another condition) |
| 5804 | { |
| 5805 | another action; |
| 5806 | } |
| 5807 | |
| 5808 | The braces can be omitted from simple one-line actions: |
| 5809 | |
| 5810 | if (condition) |
Cosmin Truta | 46aedd8 | 2018-07-15 23:58:00 -0400 | [diff] [blame] | 5811 | return 0; |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 5812 | |
| 5813 | We use 3-space indentation, except for continued statements which |
| 5814 | are usually indented the same as the first line of the statement |
| 5815 | plus four more spaces. |
| 5816 | |
Glenn Randers-Pehrson | 5ade7ed | 2009-09-30 15:11:49 -0500 | [diff] [blame] | 5817 | For macro definitions we use 2-space indentation, always leaving the "#" |
| 5818 | in the first column. |
| 5819 | |
| 5820 | #ifndef PNG_NO_FEATURE |
| 5821 | # ifndef PNG_FEATURE_SUPPORTED |
| 5822 | # define PNG_FEATURE_SUPPORTED |
| 5823 | # endif |
| 5824 | #endif |
| 5825 | |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 5826 | Comments appear with the leading "/*" at the same indentation as |
| 5827 | the statement that follows the comment: |
| 5828 | |
| 5829 | /* Single-line comment */ |
| 5830 | statement; |
| 5831 | |
Glenn Randers-Pehrson | e4c706a | 2010-03-06 14:51:54 -0600 | [diff] [blame] | 5832 | /* This is a multiple-line |
| 5833 | * comment. |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 5834 | */ |
| 5835 | statement; |
| 5836 | |
Glenn Randers-Pehrson | e4c706a | 2010-03-06 14:51:54 -0600 | [diff] [blame] | 5837 | Very short comments can be placed after the end of the statement |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 5838 | to which they pertain: |
| 5839 | |
| 5840 | statement; /* comment */ |
| 5841 | |
| 5842 | We don't use C++ style ("//") comments. We have, however, |
| 5843 | used them in the past in some now-abandoned MMX assembler |
| 5844 | code. |
| 5845 | |
Glenn Randers-Pehrson | 4df37bf | 2014-03-06 12:35:04 -0600 | [diff] [blame] | 5846 | Functions and their curly braces are not indented, and |
| 5847 | exported functions are marked with PNGAPI: |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 5848 | |
| 5849 | /* This is a public function that is visible to |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 5850 | * application programmers. It does thus-and-so. |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 5851 | */ |
| 5852 | void PNGAPI |
| 5853 | png_exported_function(png_ptr, png_info, foo) |
| 5854 | { |
| 5855 | body; |
| 5856 | } |
| 5857 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5858 | The return type and decorations are placed on a separate line |
| 5859 | ahead of the function name, as illustrated above. |
| 5860 | |
Glenn Randers-Pehrson | 416976f | 2009-07-27 22:16:09 -0500 | [diff] [blame] | 5861 | The prototypes for all exported functions appear in png.h, |
| 5862 | above the comment that says |
| 5863 | |
| 5864 | /* Maintainer: Put new public prototypes here ... */ |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 5865 | |
| 5866 | We mark all non-exported functions with "/* PRIVATE */"": |
| 5867 | |
| 5868 | void /* PRIVATE */ |
| 5869 | png_non_exported_function(png_ptr, png_info, foo) |
| 5870 | { |
| 5871 | body; |
| 5872 | } |
| 5873 | |
Glenn Randers-Pehrson | 416976f | 2009-07-27 22:16:09 -0500 | [diff] [blame] | 5874 | The prototypes for non-exported functions (except for those in |
Glenn Randers-Pehrson | 36b246a | 2014-09-27 08:59:52 -0500 | [diff] [blame] | 5875 | pngtest) appear in pngpriv.h above the comment that says |
Glenn Randers-Pehrson | 416976f | 2009-07-27 22:16:09 -0500 | [diff] [blame] | 5876 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 5877 | /* Maintainer: Put new private prototypes here ^ */ |
| 5878 | |
Glenn Randers-Pehrson | 36b246a | 2014-09-27 08:59:52 -0500 | [diff] [blame] | 5879 | To avoid polluting the global namespace, the names of all exported |
| 5880 | functions and variables begin with "png_", and all publicly visible C |
| 5881 | preprocessor macros begin with "PNG". We request that applications that |
| 5882 | use libpng *not* begin any of their own symbols with either of these strings. |
| 5883 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 5884 | We put a space after the "sizeof" operator and we omit the |
| 5885 | optional parentheses around its argument when the argument |
| 5886 | is an expression, not a type name, and we always enclose the |
| 5887 | sizeof operator, with its argument, in parentheses: |
| 5888 | |
| 5889 | (sizeof (png_uint_32)) |
| 5890 | (sizeof array) |
| 5891 | |
| 5892 | Prior to libpng-1.6.0 we used a "png_sizeof()" macro, formatted as |
| 5893 | though it were a function. |
Glenn Randers-Pehrson | ece07cf | 2012-08-10 18:08:02 -0500 | [diff] [blame] | 5894 | |
Glenn Randers-Pehrson | 36b246a | 2014-09-27 08:59:52 -0500 | [diff] [blame] | 5895 | Control keywords if, for, while, and switch are always followed by a space |
Glenn Randers-Pehrson | 64f8110 | 2017-04-03 15:25:40 -0500 | [diff] [blame] | 5896 | to distinguish them from function calls, which have no trailing space. |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 5897 | |
| 5898 | We put a space after each comma and after each semicolon |
Glenn Randers-Pehrson | 49a56e7 | 2010-12-06 20:06:01 -0600 | [diff] [blame] | 5899 | in "for" statements, and we put spaces before and after each |
Glenn Randers-Pehrson | e4c706a | 2010-03-06 14:51:54 -0600 | [diff] [blame] | 5900 | C binary operator and after "for" or "while", and before |
| 5901 | "?". We don't put a space between a typecast and the expression |
| 5902 | being cast, nor do we put one between a function name and the |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 5903 | left parenthesis that follows it: |
| 5904 | |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5905 | for (i = 2; i > 0; \-\-i) |
Glenn Randers-Pehrson | 67f3b48 | 2009-09-23 11:36:28 -0500 | [diff] [blame] | 5906 | y[i] = a(x) + (int)b; |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 5907 | |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 5908 | We prefer #ifdef and #ifndef to #if defined() and #if !defined() |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5909 | when there is only one macro being tested. We always use parentheses |
| 5910 | with "defined". |
Glenn Randers-Pehrson | d60c886 | 2009-06-15 21:56:14 -0500 | [diff] [blame] | 5911 | |
Glenn Randers-Pehrson | 8ba4b13 | 2015-08-16 22:49:58 -0500 | [diff] [blame] | 5912 | We express integer constants that are used as bit masks in hex format, |
| 5913 | with an even number of lower-case hex digits, and to make them unsigned |
| 5914 | (e.g., 0x00U, 0xffU, 0x0100U) and long if they are greater than 0x7fff |
| 5915 | (e.g., 0xffffUL). |
Glenn Randers-Pehrson | 8db1998 | 2011-10-27 16:17:24 -0500 | [diff] [blame] | 5916 | |
Glenn Randers-Pehrson | 8ba4b13 | 2015-08-16 22:49:58 -0500 | [diff] [blame] | 5917 | We prefer to use underscores rather than camelCase in names, except |
Glenn Randers-Pehrson | 871b1d0 | 2013-03-02 14:58:22 -0600 | [diff] [blame] | 5918 | for a few type names that we inherit from zlib.h. |
| 5919 | |
Glenn Randers-Pehrson | 0c44081 | 2016-10-19 19:07:25 -0500 | [diff] [blame] | 5920 | We prefer "if (something != 0)" and "if (something == 0)" over |
| 5921 | "if (something)" and if "(!something)", respectively, and for pointers |
Glenn Randers-Pehrson | 64f8110 | 2017-04-03 15:25:40 -0500 | [diff] [blame] | 5922 | we prefer "if (some_pointer != NULL)" or "if (some_pointer == NULL)". |
Glenn Randers-Pehrson | 7017c40 | 2014-03-16 20:29:11 -0500 | [diff] [blame] | 5923 | |
Glenn Randers-Pehrson | 67f3b48 | 2009-09-23 11:36:28 -0500 | [diff] [blame] | 5924 | We do not use the TAB character for indentation in the C sources. |
| 5925 | |
Glenn Randers-Pehrson | 62ca98e | 2009-12-20 15:14:57 -0600 | [diff] [blame] | 5926 | Lines do not exceed 80 characters. |
| 5927 | |
Glenn Randers-Pehrson | f210a05 | 2009-11-12 10:02:24 -0600 | [diff] [blame] | 5928 | Other rules can be inferred by inspecting the libpng source. |
Glenn Randers-Pehrson | 7654682 | 2009-05-16 07:25:42 -0500 | [diff] [blame] | 5929 | |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 5930 | .SH NOTE |
| 5931 | |
| 5932 | Note about libpng version numbers: |
| 5933 | |
| 5934 | Due to various miscommunications, unforeseen code incompatibilities |
| 5935 | and occasional factors outside the authors' control, version numbering |
| 5936 | on the library has not always been consistent and straightforward. |
| 5937 | The following table summarizes matters since version 0.89c, which was |
| 5938 | the first widely used release: |
| 5939 | |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 5940 | source png.h png.h shared-lib |
| 5941 | version string int version |
| 5942 | ------- ------ ----- ---------- |
Glenn Randers-Pehrson | fc84508 | 2015-11-03 08:24:56 -0600 | [diff] [blame] | 5943 | 0.89c "1.0 beta 3" 0.89 89 1.0.89 |
| 5944 | 0.90 "1.0 beta 4" 0.90 90 0.90 [should have been 2.0.90] |
| 5945 | 0.95 "1.0 beta 5" 0.95 95 0.95 [should have been 2.0.95] |
| 5946 | 0.96 "1.0 beta 6" 0.96 96 0.96 [should have been 2.0.96] |
| 5947 | 0.97b "1.00.97 beta 7" 1.00.97 97 1.0.1 [should have been 2.0.97] |
| 5948 | 0.97c 0.97 97 2.0.97 |
| 5949 | 0.98 0.98 98 2.0.98 |
| 5950 | 0.99 0.99 98 2.0.99 |
| 5951 | 0.99a-m 0.99 99 2.0.99 |
| 5952 | 1.00 1.00 100 2.1.0 [100 should be 10000] |
| 5953 | 1.0.0 (from here on, the 100 2.1.0 [100 should be 10000] |
| 5954 | 1.0.1 png.h string is 10001 2.1.0 |
| 5955 | 1.0.1a-e identical to the 10002 from here on, the shared library |
| 5956 | 1.0.2 source version) 10002 is 2.V where V is the source code |
| 5957 | 1.0.2a-b 10003 version, except as noted. |
| 5958 | 1.0.3 10003 |
| 5959 | 1.0.3a-d 10004 |
| 5960 | 1.0.4 10004 |
| 5961 | 1.0.4a-f 10005 |
| 5962 | 1.0.5 (+ 2 patches) 10005 |
| 5963 | 1.0.5a-d 10006 |
| 5964 | 1.0.5e-r 10100 (not source compatible) |
| 5965 | 1.0.5s-v 10006 (not binary compatible) |
| 5966 | 1.0.6 (+ 3 patches) 10006 (still binary incompatible) |
| 5967 | 1.0.6d-f 10007 (still binary incompatible) |
| 5968 | 1.0.6g 10007 |
| 5969 | 1.0.6h 10007 10.6h (testing xy.z so-numbering) |
| 5970 | 1.0.6i 10007 10.6i |
| 5971 | 1.0.6j 10007 2.1.0.6j (incompatible with 1.0.0) |
| 5972 | 1.0.7beta11-14 DLLNUM 10007 2.1.0.7beta11-14 (binary compatible) |
| 5973 | 1.0.7beta15-18 1 10007 2.1.0.7beta15-18 (binary compatible) |
| 5974 | 1.0.7rc1-2 1 10007 2.1.0.7rc1-2 (binary compatible) |
| 5975 | 1.0.7 1 10007 (still compatible) |
| 5976 | ... |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 5977 | 1.0.69 10 10069 10.so.0.69[.0] |
Glenn Randers-Pehrson | fc84508 | 2015-11-03 08:24:56 -0600 | [diff] [blame] | 5978 | ... |
Glenn Randers-Pehrson | 345fc37 | 2017-09-28 17:50:17 -0500 | [diff] [blame] | 5979 | 1.2.59 13 10259 12.so.0.59[.0] |
Glenn Randers-Pehrson | 0e30044 | 2015-11-03 08:41:03 -0600 | [diff] [blame] | 5980 | ... |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 5981 | 1.4.20 14 10420 14.so.0.20[.0] |
| 5982 | ... |
Glenn Randers-Pehrson | 345fc37 | 2017-09-28 17:50:17 -0500 | [diff] [blame] | 5983 | 1.5.30 15 10530 15.so.15.30[.0] |
Glenn Randers-Pehrson | 0e30044 | 2015-11-03 08:41:03 -0600 | [diff] [blame] | 5984 | ... |
Glenn Randers-Pehrson | 2227793 | 2017-09-29 10:50:48 -0500 | [diff] [blame] | 5985 | 1.6.35 16 10635 16.so.16.35[.0] |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 5986 | |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 5987 | Henceforth the source version will match the shared-library minor and |
| 5988 | patch numbers; the shared-library major version number will be used for |
| 5989 | changes in backward compatibility, as it is intended. |
| 5990 | The PNG_PNGLIB_VER macro, which is not used within libpng but is |
| 5991 | available for applications, is an unsigned integer of the form XYYZZ |
| 5992 | corresponding to the source version X.Y.Z (leading zeros in Y and Z). |
| 5993 | Beta versions were given the previous public release number plus a |
| 5994 | letter, until version 1.0.6j; from then on they were given the upcoming |
| 5995 | public release number plus "betaNN" or "rcNN". |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 5996 | |
Glenn Randers-Pehrson | 0f881d6 | 1998-02-07 10:20:57 -0600 | [diff] [blame] | 5997 | .SH "SEE ALSO" |
Glenn Randers-Pehrson | fc84508 | 2015-11-03 08:24:56 -0600 | [diff] [blame] | 5998 | .IR libpngpf(3) ", " png(5) |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 5999 | .LP |
Glenn Randers-Pehrson | 0f881d6 | 1998-02-07 10:20:57 -0600 | [diff] [blame] | 6000 | .IR libpng : |
| 6001 | .IP |
Viktor Szakats | 054be18 | 2017-04-03 21:23:09 +0000 | [diff] [blame] | 6002 | https://libpng.sourceforge.io/ (follow the [DOWNLOAD] link) |
Glenn Randers-Pehrson | 5e5c1e1 | 2000-11-10 12:26:19 -0600 | [diff] [blame] | 6003 | http://www.libpng.org/pub/png |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 6004 | |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 6005 | .LP |
Glenn Randers-Pehrson | 0f881d6 | 1998-02-07 10:20:57 -0600 | [diff] [blame] | 6006 | .IR zlib : |
| 6007 | .IP |
| 6008 | (generally) at the same location as |
| 6009 | .I libpng |
| 6010 | or at |
| 6011 | .br |
Viktor Szakats | 95f3c07 | 2017-05-27 13:54:30 +0000 | [diff] [blame] | 6012 | https://zlib.net/ |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 6013 | |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 6014 | .LP |
| 6015 | .IR PNG specification: RFC 2083 |
Glenn Randers-Pehrson | 0f881d6 | 1998-02-07 10:20:57 -0600 | [diff] [blame] | 6016 | .IP |
| 6017 | (generally) at the same location as |
| 6018 | .I libpng |
| 6019 | or at |
| 6020 | .br |
Viktor Szakats | 054be18 | 2017-04-03 21:23:09 +0000 | [diff] [blame] | 6021 | https://www.ietf.org/rfc/rfc2083.txt |
Glenn Randers-Pehrson | 0f881d6 | 1998-02-07 10:20:57 -0600 | [diff] [blame] | 6022 | .br |
| 6023 | or (as a W3C Recommendation) at |
| 6024 | .br |
Viktor Szakats | 054be18 | 2017-04-03 21:23:09 +0000 | [diff] [blame] | 6025 | https://www.w3.org/TR/REC-png.html |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 6026 | |
Glenn Randers-Pehrson | cbe52d8 | 1998-02-28 07:00:24 -0600 | [diff] [blame] | 6027 | .LP |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 6028 | In the case of any inconsistency between the PNG specification |
| 6029 | and this library, the specification takes precedence. |
| 6030 | |
Glenn Randers-Pehrson | 0f881d6 | 1998-02-07 10:20:57 -0600 | [diff] [blame] | 6031 | .SH AUTHORS |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 6032 | This man page: |
| 6033 | Initially created by Glenn Randers-Pehrson. |
| 6034 | Maintained by Cosmin Truta. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 6035 | |
| 6036 | The contributing authors would like to thank all those who helped |
| 6037 | with testing, bug fixes, and patience. This wouldn't have been |
| 6038 | possible without all of you. |
| 6039 | |
| 6040 | Thanks to Frank J. T. Wojcik for helping with the documentation. |
Glenn Randers-Pehrson | 166c5a3 | 1999-12-10 09:43:02 -0600 | [diff] [blame] | 6041 | |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 6042 | Libpng: |
Glenn Randers-Pehrson | 0f881d6 | 1998-02-07 10:20:57 -0600 | [diff] [blame] | 6043 | Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc. |
Cosmin Truta | 8440326 | 2018-07-29 00:33:12 -0400 | [diff] [blame] | 6044 | Maintained by Cosmin Truta. |
Glenn Randers-Pehrson | a357b99 | 1998-02-08 20:56:40 -0600 | [diff] [blame] | 6045 | |
Glenn Randers-Pehrson | 0f881d6 | 1998-02-07 10:20:57 -0600 | [diff] [blame] | 6046 | Supported by the PNG development group |
| 6047 | .br |
Glenn Randers-Pehrson | 7b34df3 | 2006-02-24 06:30:16 -0600 | [diff] [blame] | 6048 | png-mng-implement at lists.sourceforge.net (subscription required; visit |
Glenn Randers-Pehrson | 9c3ab68 | 2006-02-20 22:09:05 -0600 | [diff] [blame] | 6049 | https://lists.sourceforge.net/lists/listinfo/png-mng-implement |
| 6050 | to subscribe). |
Glenn Randers-Pehrson | 0f881d6 | 1998-02-07 10:20:57 -0600 | [diff] [blame] | 6051 | |
Glenn Randers-Pehrson | 0f881d6 | 1998-02-07 10:20:57 -0600 | [diff] [blame] | 6052 | .\" end of man page |