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gerrit-public.fairphone.software / platform / external / libpng / 759c90368697f29ecbec767758fbf742c85aef2f / . / libpng.3
blob: fbda05ebb3b14c7678a7557a038b71e56fafec46 [file] [log] [blame]
Glenn Randers-Pehrson759c9032014-02-01 20:11:48 -0600[diff] [blame^]1.TH LIBPNG 3 "February 2, 2014"
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]2.SH NAME
Glenn Randers-Pehrson759c9032014-02-01 20:11:48 -0600[diff] [blame^]3libpng \- Portable Network Graphics (PNG) Reference Library 1.6.9rc03
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4.SH SYNOPSIS
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5\fB
6#include <png.h>\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]7
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]8\fBpng_uint_32 png_access_version_number \fI(void\fP\fB);\fP
9
Glenn Randers-Pehrson6bc53be2006-06-16 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-Pehrsonbb98bcb2011-01-22 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-Pehrsonbb98bcb2011-01-22 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-Pehrson6bc53be2006-06-16 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-Pehrson4393a9a1999-09-17 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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]19
Glenn Randers-Pehrson4393a9a1999-09-17 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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]21
Glenn Randers-Pehrson4393a9a1999-09-17 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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]23
Glenn Randers-Pehrson4393a9a1999-09-17 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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]25
Glenn Randers-Pehrson4393a9a1999-09-17 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-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]27
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]28\fBpng_infop png_create_info_struct (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]29
Glenn Randers-Pehrson5e5c1e12000-11-10 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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]31
Glenn Randers-Pehrsonbb98bcb2011-01-22 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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]33
Glenn Randers-Pehrson5e5c1e12000-11-10 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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]35
Glenn Randers-Pehrsonbb98bcb2011-01-22 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
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]39
Glenn Randers-Pehrson4393a9a1999-09-17 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-Pehrson4393a9a1999-09-17 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-Pehrson4393a9a1999-09-17 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-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]46\fBvoid png_err (png_structp \fIpng_ptr\fP\fB);\fP
47
Glenn Randers-Pehrson4393a9a1999-09-17 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-Pehrson4393a9a1999-09-17 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-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]52\fBvoid png_free_chunk_list (png_structp \fIpng_ptr\fP\fB);\fP
53
Glenn Randers-Pehrsonbb98bcb2011-01-22 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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]55
Glenn Randers-Pehrsona77ef622000-02-18 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-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]57
John Bowler0a5c9c02011-01-22 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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]59
John Bowler0a5c9c02011-01-22 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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]61
John Bowler0a5c9c02011-01-22 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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]63
John Bowler0a5c9c02011-01-22 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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]65
John Bowler0a5c9c02011-01-22 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-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]67
Glenn Randers-Pehrson871b1d02013-03-02 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-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]69
John Bowler736f40f2011-08-25 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 Bowler736f40f2011-08-25 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 Bowler0a5c9c02011-01-22 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-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]75
John Bowler0a5c9c02011-01-22 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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]77
John Bowler0a5c9c02011-01-22 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-Pehrson800d1e92008-08-20 17:25:21 -0500[diff] [blame]79
John Bowler0a5c9c02011-01-22 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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]81
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]82\fBpng_byte png_get_copyright (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]83
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]84\fBpng_uint_32 png_get_current_row_number \fI(png_const_structp\fP\fB);\fP
85
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]86\fBpng_byte png_get_current_pass_number \fI(png_const_structp\fP\fB);\fP
87
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]88\fBpng_voidp png_get_error_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]89
John Bowler0a5c9c02011-01-22 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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]91
John Bowler0a5c9c02011-01-22 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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]93
John Bowler0a5c9c02011-01-22 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-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]95
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]96\fBpng_byte png_get_header_ver (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]97
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]98\fBpng_byte png_get_header_version (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]99
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]100\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]101
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]102\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-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]103
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]104\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
105
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]106\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]107
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]108\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]109
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]110\fBpng_int_32 png_get_int_32 (png_bytep \fIbuf\fP\fB);\fP
111
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]112\fBpng_byte png_get_interlace_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]113
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]114\fBpng_uint_32 png_get_io_chunk_type (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona63dbed2011-01-22 08:51:19 -0600[diff] [blame]115
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]116\fBpng_voidp png_get_io_ptr (png_structp \fIpng_ptr\fP\fB);\fP
117
Glenn Randers-Pehrsona63dbed2011-01-22 08:51:19 -0600[diff] [blame]118\fBpng_uint_32 png_get_io_state (png_structp \fIpng_ptr\fP\fB);\fP
119
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]120\fBpng_byte png_get_libpng_ver (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]121
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]122\fBpng_voidp png_get_mem_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]123
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]124\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]125
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]126\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]127
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]128\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]129
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]130\fBfloat png_get_pixel_aspect_ratio (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]131
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]132\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-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]133
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]134\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-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]135
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]136\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-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]137
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]138\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]139
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]140\fBpng_voidp png_get_progressive_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]141
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]142\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]143
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]144\fBpng_byte png_get_rgb_to_gray_status (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsone4f124e2012-12-09 19:20:34 -0600[diff] [blame]145
146\fBpng_uint_32 png_get_rowbytes (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
147
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]148\fBpng_bytepp png_get_rows (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]149
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]150\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]151
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]152\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-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]153
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]154\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-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]155
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]156\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-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]157
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]158\fBpng_bytep png_get_signature (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]159
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]160\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-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]161
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]162\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]163
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]164\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]165
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]166\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]167
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]168\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]169
Glenn Randers-Pehrsone4f124e2012-12-09 19:20:34 -0600[diff] [blame]170\fB/* This function is really an inline macro. \fI*/
Glenn Randers-Pehrsonb6bfd402012-12-19 16:06:56 -0600[diff] [blame]171
Glenn Randers-Pehrsone4f124e2012-12-09 19:20:34 -0600[diff] [blame]172\fBpng_uint_16 png_get_uint_16 (png_bytep \fIbuf\fP\fB);\fP
173
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]174\fBpng_uint_32 png_get_uint_31 (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIbuf\fP\fB);\fP
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]175
Glenn Randers-Pehrsone4f124e2012-12-09 19:20:34 -0600[diff] [blame]176\fB/* This function is really an inline macro. \fI*/
Glenn Randers-Pehrsonb6bfd402012-12-19 16:06:56 -0600[diff] [blame]177
Glenn Randers-Pehrsone4f124e2012-12-09 19:20:34 -0600[diff] [blame]178\fBpng_uint_32 png_get_uint_32 (png_bytep \fIbuf\fP\fB);\fP
179
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]180\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-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]181
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]182\fBpng_voidp png_get_user_chunk_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]183
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]184\fBpng_uint_32 png_get_user_height_max (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]185
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]186\fBpng_voidp png_get_user_transform_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]187
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]188\fBpng_uint_32 png_get_user_width_max (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]189
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]190\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]191
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]192\fBfloat png_get_x_offset_inches (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]193
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]194\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-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]195
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]196\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]197
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]198\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]199
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]200\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-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]201
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]202\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]203
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]204\fBfloat png_get_y_offset_inches (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]205
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]206\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-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]207
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]208\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]209
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]210\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]211
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]212\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-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]213
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]214\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]215
Glenn Randers-Pehrsonc1bfe682002-03-06 22:08:00 -0600[diff] [blame]216\fBint png_handle_as_unknown (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIchunk_name\fP\fB);\fP
217
Glenn Randers-Pehrsone0a6c062011-11-07 23:50:05 -0600[diff] [blame]218\fBint png_image_begin_read_from_file (png_imagep \fP\fIimage\fP\fB, const char \fI*file_name\fP\fB);\fP
219
Glenn Randers-Pehrsone0a6c062011-11-07 23:50:05 -0600[diff] [blame]220\fBint png_image_begin_read_from_stdio (png_imagep \fP\fIimage\fP\fB, FILE* \fIfile\fP\fB);\fP
221
Glenn Randers-Pehrsone0a6c062011-11-07 23:50:05 -0600[diff] [blame]222\fBint, png_image_begin_read_from_memory (png_imagep \fP\fIimage\fP\fB, png_const_voidp \fP\fImemory\fP\fB, png_size_t \fIsize\fP\fB);\fP
223
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]224\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-Pehrsone0a6c062011-11-07 23:50:05 -0600[diff] [blame]225
Glenn Randers-Pehrsone0a6c062011-11-07 23:50:05 -0600[diff] [blame]226\fBvoid png_image_free (png_imagep \fIimage\fP\fB);\fP
227
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]228\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-Pehrsoncc02f892012-08-29 14:03:09 -0500[diff] [blame]229
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]230\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-Pehrsone0a6c062011-11-07 23:50:05 -0600[diff] [blame]231
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]232\fBvoid png_info_init_3 (png_infopp \fP\fIinfo_ptr\fP\fB, png_size_t \fIpng_info_struct_size\fP\fB);\fP
233
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]234\fBvoid png_init_io (png_structp \fP\fIpng_ptr\fP\fB, FILE \fI*fp\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]235
Glenn Randers-Pehrsonf98726a2010-02-19 09:54:53 -0600[diff] [blame]236\fBvoid png_longjmp (png_structp \fP\fIpng_ptr\fP\fB, int \fIval\fP\fB);\fP
237
Glenn Randers-Pehrsonbeb572e2006-08-19 13:59:24 -0500[diff] [blame]238\fBpng_voidp png_malloc (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]239
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]240\fBpng_voidp png_malloc_default (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP
241
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]242\fBpng_voidp png_malloc_warn (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP
243
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]244\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-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]245
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]246\fBvoid png_process_data (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fIbuffer\fP\fB, png_size_t \fIbuffer_size\fP\fB);\fP
247
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]248\fBpng_size_t png_process_data_pause \fP\fI(png_structp\fP\fB, int \fIsave\fP\fB);\fP
249
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]250\fBpng_uint_32 png_process_data_skip \fI(png_structp\fP\fB);\fP
251
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]252\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
253
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]254\fBvoid png_read_end (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
255
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]256\fBvoid png_read_image (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fIimage\fP\fB);\fP
257
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]258\fBvoid png_read_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
259
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]260\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-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]261
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]262\fBvoid png_read_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIrow\fP\fB, png_bytep \fIdisplay_row\fP\fB);\fP
263
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]264\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
265
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]266\fBvoid png_read_update_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
267
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]268\fBint png_reset_zstream (png_structp \fIpng_ptr\fP\fB);\fP
269
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]270\fBvoid png_save_int_32 (png_bytep \fP\fIbuf\fP\fB, png_int_32 \fIi\fP\fB);\fP
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]271
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]272\fBvoid png_save_uint_16 (png_bytep \fP\fIbuf\fP\fB, unsigned int \fIi\fP\fB);\fP
273
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]274\fBvoid png_save_uint_32 (png_bytep \fP\fIbuf\fP\fB, png_uint_32 \fIi\fP\fB);\fP
275
Glenn Randers-Pehrsone4f124e2012-12-09 19:20:34 -0600[diff] [blame]276\fBvoid png_set_add_alpha (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIfiller\fP\fB, int \fIflags\fP\fB);\fP
277
Glenn Randers-Pehrsone4f124e2012-12-09 19:20:34 -0600[diff] [blame]278\fBvoid png_set_alpha_mode (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fImode\fP\fB, double \fIoutput_gamma\fP\fB);\fP
279
Glenn Randers-Pehrsone4f124e2012-12-09 19:20:34 -0600[diff] [blame]280\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
281
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]282\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
283
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]284\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
285
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]286\fBvoid png_set_benign_errors (png_structp \fP\fIpng_ptr\fP\fB, int \fIallowed\fP\fB);\fP
287
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]288\fBvoid png_set_bgr (png_structp \fIpng_ptr\fP\fB);\fP
289
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]290\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
291
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]292\fBvoid png_set_check_for_invalid_index(png_structrp \fP\fIpng_ptr\fP\fB, int \fIallowed\fP\fB);\fP
Glenn Randers-Pehrson434801a2012-03-02 22:38:50 -0600[diff] [blame]293
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]294\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
295
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]296\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
297
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]298\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 Bowler736f40f2011-08-25 16:19:44 -0500[diff] [blame]299
300\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
301
Glenn Randers-Pehrson800d1e92008-08-20 17:25:21 -0500[diff] [blame]302\fBvoid png_set_chunk_cache_max (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIuser_chunk_cache_max\fP\fB);\fP
303
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]304\fBvoid png_set_compression_level (png_structp \fP\fIpng_ptr\fP\fB, int \fIlevel\fP\fB);\fP
305
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]306\fBvoid png_set_compression_mem_level (png_structp \fP\fIpng_ptr\fP\fB, int \fImem_level\fP\fB);\fP
307
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]308\fBvoid png_set_compression_method (png_structp \fP\fIpng_ptr\fP\fB, int \fImethod\fP\fB);\fP
309
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]310\fBvoid png_set_compression_strategy (png_structp \fP\fIpng_ptr\fP\fB, int \fIstrategy\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]311
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]312\fBvoid png_set_compression_window_bits (png_structp \fP\fIpng_ptr\fP\fB, int \fIwindow_bits\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]313
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]314\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]315
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]316\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]317
Glenn Randers-Pehrsond08b6bd2011-02-19 15:50:17 -0600[diff] [blame]318\fBvoid png_set_expand (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsonc85f5f62011-02-13 05:56:07 -0600[diff] [blame]319
Glenn Randers-Pehrsond08b6bd2011-02-19 15:50:17 -0600[diff] [blame]320\fBvoid png_set_expand_16 (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]321
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]322\fBvoid png_set_expand_gray_1_2_4_to_8 (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson1ce08362006-03-08 23:35:59 -0600[diff] [blame]323
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]324\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]325
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]326\fBvoid png_set_filter (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fImethod\fP\fB, int \fIfilters\fP\fB);\fP
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]327
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]328\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-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]329
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]330\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
331
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]332\fBvoid png_set_flush (png_structp \fP\fIpng_ptr\fP\fB, int \fInrows\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]333
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]334\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]335
Glenn Randers-Pehrsone4f124e2012-12-09 19:20:34 -0600[diff] [blame]336\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
337
Glenn Randers-Pehrsone4f124e2012-12-09 19:20:34 -0600[diff] [blame]338\fBvoid png_set_gAMA (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fIfile_gamma\fP\fB);\fP
339
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]340\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
341
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]342\fBvoid png_set_gray_1_2_4_to_8 (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]343
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]344\fBvoid png_set_gray_to_rgb (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]345
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]346\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]347
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]348\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-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]349
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]350\fBint png_set_interlace_handling (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]351
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]352\fBvoid png_set_invalid (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fImask\fP\fB);\fP
353
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]354\fBvoid png_set_invert_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]355
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]356\fBvoid png_set_invert_mono (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]357
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]358\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]359
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]360\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-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]361
Glenn Randers-Pehrson1e6ed732009-11-20 22:06:56 -0600[diff] [blame]362\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
363
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]364\fBvoid png_set_chunk_malloc_max (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIuser_chunk_cache_max\fP\fB);\fP
365
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]366\fBvoid png_set_compression_buffer_size (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP
367
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]368\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]369
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]370\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-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]371
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]372\fBvoid png_set_packing (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]373
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]374\fBvoid png_set_packswap (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]375
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]376\fBvoid png_set_palette_to_rgb (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]377
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]378\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]379
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]380\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]381
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]382\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]383
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]384\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]385
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]386\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
387
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]388\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]389
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]390\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]391
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]392\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
393
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]394\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]395
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]396\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
397
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]398\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]399
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]400\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
401
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]402\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]403
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]404\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
405
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]406\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
407
Glenn Randers-Pehrsone4f124e2012-12-09 19:20:34 -0600[diff] [blame]408\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
409
Glenn Randers-Pehrsone4f124e2012-12-09 19:20:34 -0600[diff] [blame]410\fBvoid png_set_scale_16 (png_structp \fIpng_ptr\fP\fB);\fP
411
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]412\fBvoid png_set_shift (png_structp \fP\fIpng_ptr\fP\fB, png_color_8p \fItrue_bits\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]413
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]414\fBvoid png_set_sig_bytes (png_structp \fP\fIpng_ptr\fP\fB, int \fInum_bytes\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]415
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]416\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-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]417
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]418\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]419
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]420\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]421
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]422\fBvoid png_set_strip_16 (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]423
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]424\fBvoid png_set_strip_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]425
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]426\fBvoid png_set_strip_error_numbers (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIstrip_mode\fP\fB);\fP
427
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]428\fBvoid png_set_swap (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]429
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]430\fBvoid png_set_swap_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]431
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]432\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]433
Glenn Randers-Pehrson8eb88332011-04-01 00:16:50 -0500[diff] [blame]434\fBvoid png_set_text_compression_level (png_structp \fP\fIpng_ptr\fP\fB, int \fIlevel\fP\fB);\fP
435
Glenn Randers-Pehrson8eb88332011-04-01 00:16:50 -0500[diff] [blame]436\fBvoid png_set_text_compression_mem_level (png_structp \fP\fIpng_ptr\fP\fB, int \fImem_level\fP\fB);\fP
437
Glenn Randers-Pehrson8eb88332011-04-01 00:16:50 -0500[diff] [blame]438\fBvoid png_set_text_compression_strategy (png_structp \fP\fIpng_ptr\fP\fB, int \fIstrategy\fP\fB);\fP
439
Glenn Randers-Pehrson8eb88332011-04-01 00:16:50 -0500[diff] [blame]440\fBvoid png_set_text_compression_window_bits (png_structp \fP\fIpng_ptr\fP\fB, int \fIwindow_bits\fP\fB);\fP
441
Glenn Randers-Pehrson8eb88332011-04-01 00:16:50 -0500[diff] [blame]442\fBvoid \fP\fIpng_set_text_compression_method\fP\fB, (png_structp \fP\fIpng_ptr\fP\fB, int \fImethod)\fP\fB);\fP
443
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]444\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]445
Glenn Randers-Pehrsonf3c51e42011-01-15 10:25:25 -0600[diff] [blame]446\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-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]447
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]448\fBvoid png_set_tRNS_to_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]449
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]450\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
451
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]452\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-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]453
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]454\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
455
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]456\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]457
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]458\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]459
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]460\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]461
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]462\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-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]463
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]464\fBint png_sig_cmp (png_bytep \fP\fIsig\fP\fB, png_size_t \fP\fIstart\fP\fB, png_size_t \fInum_to_check\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]465
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]466\fBvoid png_start_read_image (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]467
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]468\fBvoid png_warning (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fImessage\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]469
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]470\fBvoid png_write_chunk (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIchunk_name\fP\fB, png_bytep \fP\fIdata\fP\fB, png_size_t \fIlength\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]471
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]472\fBvoid png_write_chunk_data (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIdata\fP\fB, png_size_t \fIlength\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]473
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]474\fBvoid png_write_chunk_end (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]475
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]476\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]477
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]478\fBvoid png_write_end (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]479
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]480\fBvoid png_write_flush (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]481
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]482\fBvoid png_write_image (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fIimage\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]483
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]484\fBvoid png_write_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]485
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]486\fBvoid png_write_info_before_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
487
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]488\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-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]489
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]490\fBvoid png_write_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIrow\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]491
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]492\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-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]493
Glenn Randers-Pehrson6bc53be2006-06-16 07:52:03 -0500[diff] [blame]494\fBvoid png_write_sig (png_structp \fIpng_ptr\fP\fB);\fP
495
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]496.SH DESCRIPTION
497The
498.I libpng
499library supports encoding, decoding, and various manipulations of
500the Portable Network Graphics (PNG) format image files. It uses the
501.IR zlib(3)
502compression library.
Glenn Randers-Pehrson557b2562010-10-17 12:55:04 -0500[diff] [blame]503Following is a copy of the libpng-manual.txt file that accompanies libpng.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]504.SH LIBPNG.TXT
Glenn Randers-Pehrson557b2562010-10-17 12:55:04 -0500[diff] [blame]505libpng-manual.txt - A description on how to use and modify libpng
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]506
Glenn Randers-Pehrson759c9032014-02-01 20:11:48 -0600[diff] [blame^]507 libpng version 1.6.9rc03 - February 2, 2014
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]508 Updated and distributed by Glenn Randers-Pehrson
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]509 <glennrp at users.sourceforge.net>
Glenn Randers-Pehrson759c9032014-02-01 20:11:48 -0600[diff] [blame^]510 Copyright (c) 1998-2014 Glenn Randers-Pehrson
Glenn Randers-Pehrson037023b2009-06-24 10:27:36 -0500[diff] [blame]511
Glenn Randers-Pehrsonbfbf8652009-06-26 21:46:52 -0500[diff] [blame]512 This document is released under the libpng license.
Glenn Randers-Pehrsonc332bbc2009-06-25 13:43:50 -0500[diff] [blame]513 For conditions of distribution and use, see the disclaimer
Glenn Randers-Pehrson037023b2009-06-24 10:27:36 -0500[diff] [blame]514 and license in png.h
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]515
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]516 Based on:
517
Glenn Randers-Pehrson759c9032014-02-01 20:11:48 -0600[diff] [blame^]518 libpng versions 0.97, January 1998, through 1.6.9rc03 - February 2, 2014
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]519 Updated and distributed by Glenn Randers-Pehrson
Glenn Randers-Pehrson759c9032014-02-01 20:11:48 -0600[diff] [blame^]520 Copyright (c) 1998-2014 Glenn Randers-Pehrson
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]521
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]522 libpng 1.0 beta 6 version 0.96 May 28, 1997
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]523 Updated and distributed by Andreas Dilger
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]524 Copyright (c) 1996, 1997 Andreas Dilger
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]525
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]526 libpng 1.0 beta 2 - version 0.88 January 26, 1996
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]527 For conditions of distribution and use, see copyright
528 notice in png.h. Copyright (c) 1995, 1996 Guy Eric
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]529 Schalnat, Group 42, Inc.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]530
531 Updated/rewritten per request in the libpng FAQ
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]532 Copyright (c) 1995, 1996 Frank J. T. Wojcik
533 December 18, 1995 & January 20, 1996
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]534
Glenn Randers-Pehrson6e418422011-12-29 20:57:39 -0600[diff] [blame]535 TABLE OF CONTENTS
536
537 I. Introduction
538 II. Structures
539 III. Reading
540 IV. Writing
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]541 V. Simplified API
542 VI. Modifying/Customizing libpng
543 VII. MNG support
544 VIII. Changes to Libpng from version 0.88
545 IX. Changes to Libpng from version 1.0.x to 1.2.x
546 X. Changes to Libpng from version 1.0.x/1.2.x to 1.4.x
547 XI. Changes to Libpng from version 1.4.x to 1.5.x
548 XII. Changes to Libpng from version 1.5.x to 1.6.x
549 XIII. Detecting libpng
550 XIV. Source code repository
551 XV. Coding style
552 XVI. Y2K Compliance in libpng
Glenn Randers-Pehrson6e418422011-12-29 20:57:39 -0600[diff] [blame]553
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]554.SH I. Introduction
555
556This file describes how to use and modify the PNG reference library
Glenn Randers-Pehrson49f9c242013-04-27 18:03:03 -0500[diff] [blame]557(known as libpng) for your own use. In addition to this
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]558file, example.c is a good starting point for using the library, as
559it is heavily commented and should include everything most people
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]560will need. We assume that libpng is already installed; see the
561INSTALL file for instructions on how to install libpng.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]562
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]563For examples of libpng usage, see the files "example.c", "pngtest.c",
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]564and the files in the "contrib" directory, all of which are included in
565the libpng distribution.
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]566
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]567Libpng was written as a companion to the PNG specification, as a way
568of reducing the amount of time and effort it takes to support the PNG
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]569file format in application programs.
570
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]571The PNG specification (second edition), November 2003, is available as
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]572a W3C Recommendation and as an ISO Standard (ISO/IEC 15948:2004 (E)) at
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]573<http://www.w3.org/TR/2003/REC-PNG-20031110/
574The W3C and ISO documents have identical technical content.
575
576The PNG-1.2 specification is available at
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]577<http://www.libpng.org/pub/png/documents/>. It is technically equivalent
578to the PNG specification (second edition) but has some additional material.
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]579
580The PNG-1.0 specification is available
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]581as RFC 2083 <http://www.libpng.org/pub/png/documents/> and as a
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]582W3C Recommendation <http://www.w3.org/TR/REC.png.html>.
583
584Some additional chunks are described in the special-purpose public chunks
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]585documents at <http://www.libpng.org/pub/png/documents/>.
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]586
587Other information
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]588about PNG, and the latest version of libpng, can be found at the PNG home
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]589page, <http://www.libpng.org/pub/png/>.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]590
591Most users will not have to modify the library significantly; advanced
592users may want to modify it more. All attempts were made to make it as
593complete as possible, while keeping the code easy to understand.
594Currently, this library only supports C. Support for other languages
595is being considered.
596
597Libpng has been designed to handle multiple sessions at one time,
598to be easily modifiable, to be portable to the vast majority of
599machines (ANSI, K&R, 16-, 32-, and 64-bit) available, and to be easy
600to use. The ultimate goal of libpng is to promote the acceptance of
601the PNG file format in whatever way possible. While there is still
602work to be done (see the TODO file), libpng should cover the
603majority of the needs of its users.
604
605Libpng uses zlib for its compression and decompression of PNG files.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]606Further information about zlib, and the latest version of zlib, can
Glenn Randers-Pehrsond56aca72000-11-23 11:51:42 -0600[diff] [blame]607be found at the zlib home page, <http://www.info-zip.org/pub/infozip/zlib/>.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]608The zlib compression utility is a general purpose utility that is
609useful for more than PNG files, and can be used without libpng.
610See the documentation delivered with zlib for more details.
611You can usually find the source files for the zlib utility wherever you
612find the libpng source files.
613
614Libpng is thread safe, provided the threads are using different
615instances of the structures. Each thread should have its own
616png_struct and png_info instances, and thus its own image.
617Libpng does not protect itself against two threads using the
Glenn Randers-Pehrson56f63962008-10-06 10:16:17 -0500[diff] [blame]618same instance of a structure.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]619
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]620.SH II. Structures
621
622There are two main structures that are important to libpng, png_struct
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]623and png_info. Both are internal structures that are no longer exposed
624in the libpng interface (as of libpng 1.5.0).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]625
626The png_info structure is designed to provide information about the
627PNG file. At one time, the fields of png_info were intended to be
628directly accessible to the user. However, this tended to cause problems
629with applications using dynamically loaded libraries, and as a result
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]630a set of interface functions for png_info (the png_get_*() and png_set_*()
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]631functions) was developed, and direct access to the png_info fields was
632deprecated..
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]633
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]634The png_struct structure is the object used by the library to decode a
635single image. As of 1.5.0 this structure is also not exposed.
636
637Almost all libpng APIs require a pointer to a png_struct as the first argument.
638Many (in particular the png_set and png_get APIs) also require a pointer
639to png_info as the second argument. Some application visible macros
640defined in png.h designed for basic data access (reading and writing
Glenn Randers-Pehrsona5e55472011-07-12 10:13:32 -0500[diff] [blame]641integers in the PNG format) don't take a png_info pointer, but it's almost
642always safe to assume that a (png_struct*) has to be passed to call an API
643function.
644
645You can have more than one png_info structure associated with an image,
646as illustrated in pngtest.c, one for information valid prior to the
647IDAT chunks and another (called "end_info" below) for things after them.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]648
649The png.h header file is an invaluable reference for programming with libpng.
650And while I'm on the topic, make sure you include the libpng header file:
651
652#include <png.h>
653
Glenn Randers-Pehrsona5e55472011-07-12 10:13:32 -0500[diff] [blame]654and also (as of libpng-1.5.0) the zlib header file, if you need it:
655
656#include <zlib.h>
657
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]658.SS Types
659
660The png.h header file defines a number of integral types used by the
661APIs. Most of these are fairly obvious; for example types corresponding
662to integers of particular sizes and types for passing color values.
663
664One exception is how non-integral numbers are handled. For application
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]665convenience most APIs that take such numbers have C (double) arguments;
666however, internally PNG, and libpng, use 32 bit signed integers and encode
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]667the value by multiplying by 100,000. As of libpng 1.5.0 a convenience
668macro PNG_FP_1 is defined in png.h along with a type (png_fixed_point)
669which is simply (png_int_32).
670
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]671All APIs that take (double) arguments also have a matching API that
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]672takes the corresponding fixed point integer arguments. The fixed point
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]673API has the same name as the floating point one with "_fixed" appended.
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]674The actual range of values permitted in the APIs is frequently less than
Glenn Randers-Pehrson4dcbf242013-08-06 17:20:06 -0500[diff] [blame]675the full range of (png_fixed_point) (\-21474 to +21474). When APIs require
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]676a non-negative argument the type is recorded as png_uint_32 above. Consult
677the header file and the text below for more information.
678
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]679Special care must be take with sCAL chunk handling because the chunk itself
680uses non-integral values encoded as strings containing decimal floating point
681numbers. See the comments in the header file.
682
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]683.SS Configuration
684
685The main header file function declarations are frequently protected by C
686preprocessing directives of the form:
687
688 #ifdef PNG_feature_SUPPORTED
689 declare-function
690 #endif
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]691 ...
692 #ifdef PNG_feature_SUPPORTED
693 use-function
694 #endif
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]695
696The library can be built without support for these APIs, although a
697standard build will have all implemented APIs. Application programs
698should check the feature macros before using an API for maximum
699portability. From libpng 1.5.0 the feature macros set during the build
700of libpng are recorded in the header file "pnglibconf.h" and this file
701is always included by png.h.
702
Glenn Randers-Pehrsona5e55472011-07-12 10:13:32 -0500[diff] [blame]703If you don't need to change the library configuration from the default, skip to
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]704the next section ("Reading").
705
706Notice that some of the makefiles in the 'scripts' directory and (in 1.5.0) all
707of the build project files in the 'projects' directory simply copy
708scripts/pnglibconf.h.prebuilt to pnglibconf.h. This means that these build
709systems do not permit easy auto-configuration of the library - they only
710support the default configuration.
711
712The easiest way to make minor changes to the libpng configuration when
713auto-configuration is supported is to add definitions to the command line
714using (typically) CPPFLAGS. For example:
715
Glenn Randers-Pehrson4dcbf242013-08-06 17:20:06 -0500[diff] [blame]716CPPFLAGS=\-DPNG_NO_FLOATING_ARITHMETIC
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]717
718will change the internal libpng math implementation for gamma correction and
719other arithmetic calculations to fixed point, avoiding the need for fast
720floating point support. The result can be seen in the generated pnglibconf.h -
721make sure it contains the changed feature macro setting.
722
723If you need to make more extensive configuration changes - more than one or two
Glenn Randers-Pehrson4dcbf242013-08-06 17:20:06 -0500[diff] [blame]724feature macro settings - you can either add \-DPNG_USER_CONFIG to the build
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]725command line and put a list of feature macro settings in pngusr.h or you can set
726DFA_XTRA (a makefile variable) to a file containing the same information in the
727form of 'option' settings.
728
729A. Changing pnglibconf.h
730
731A variety of methods exist to build libpng. Not all of these support
732reconfiguration of pnglibconf.h. To reconfigure pnglibconf.h it must either be
733rebuilt from scripts/pnglibconf.dfa using awk or it must be edited by hand.
734
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]735Hand editing is achieved by copying scripts/pnglibconf.h.prebuilt to
736pnglibconf.h and changing the lines defining the supported features, paying
737very close attention to the 'option' information in scripts/pnglibconf.dfa
738that describes those features and their requirements. This is easy to get
739wrong.
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]740
741B. Configuration using DFA_XTRA
742
743Rebuilding from pnglibconf.dfa is easy if a functioning 'awk', or a later
744variant such as 'nawk' or 'gawk', is available. The configure build will
745automatically find an appropriate awk and build pnglibconf.h.
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]746The scripts/pnglibconf.mak file contains a set of make rules for doing the
747same thing if configure is not used, and many of the makefiles in the scripts
748directory use this approach.
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]749
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]750When rebuilding simply write a new file containing changed options and set
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]751DFA_XTRA to the name of this file. This causes the build to append the new file
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]752to the end of scripts/pnglibconf.dfa. The pngusr.dfa file should contain lines
753of the following forms:
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]754
755everything = off
756
757This turns all optional features off. Include it at the start of pngusr.dfa to
758make it easier to build a minimal configuration. You will need to turn at least
759some features on afterward to enable either reading or writing code, or both.
760
761option feature on
762option feature off
763
764Enable or disable a single feature. This will automatically enable other
765features required by a feature that is turned on or disable other features that
766require a feature which is turned off. Conflicting settings will cause an error
767message to be emitted by awk.
768
769setting feature default value
770
771Changes the default value of setting 'feature' to 'value'. There are a small
772number of settings listed at the top of pnglibconf.h, they are documented in the
773source code. Most of these values have performance implications for the library
774but most of them have no visible effect on the API. Some can also be overridden
775from the API.
776
Glenn Randers-Pehrsona5e55472011-07-12 10:13:32 -0500[diff] [blame]777This method of building a customized pnglibconf.h is illustrated in
778contrib/pngminim/*. See the "$(PNGCONF):" target in the makefile and
779pngusr.dfa in these directories.
780
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]781C. Configuration using PNG_USR_CONFIG
782
Glenn Randers-Pehrson4dcbf242013-08-06 17:20:06 -0500[diff] [blame]783If \-DPNG_USR_CONFIG is added to the CFLAGS when pnglibconf.h is built the file
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]784pngusr.h will automatically be included before the options in
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]785scripts/pnglibconf.dfa are processed. Your pngusr.h file should contain only
786macro definitions turning features on or off or setting settings.
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]787
788Apart from the global setting "everything = off" all the options listed above
789can be set using macros in pngusr.h:
790
791#define PNG_feature_SUPPORTED
792
793is equivalent to:
794
795option feature on
796
797#define PNG_NO_feature
798
799is equivalent to:
800
801option feature off
802
803#define PNG_feature value
804
805is equivalent to:
806
807setting feature default value
808
809Notice that in both cases, pngusr.dfa and pngusr.h, the contents of the
810pngusr file you supply override the contents of scripts/pnglibconf.dfa
811
812If confusing or incomprehensible behavior results it is possible to
813examine the intermediate file pnglibconf.dfn to find the full set of
814dependency information for each setting and option. Simply locate the
815feature in the file and read the C comments that precede it.
816
Glenn Randers-Pehrsona5e55472011-07-12 10:13:32 -0500[diff] [blame]817This method is also illustrated in the contrib/pngminim/* makefiles and
818pngusr.h.
819
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]820.SH III. Reading
821
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]822We'll now walk you through the possible functions to call when reading
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]823in a PNG file sequentially, briefly explaining the syntax and purpose
824of each one. See example.c and png.h for more detail. While
825progressive reading is covered in the next section, you will still
826need some of the functions discussed in this section to read a PNG
827file.
828
829.SS Setup
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]830
831You will want to do the I/O initialization(*) before you get into libpng,
832so if it doesn't work, you don't have much to undo. Of course, you
833will also want to insure that you are, in fact, dealing with a PNG
834file. Libpng provides a simple check to see if a file is a PNG file.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]835To use it, pass in the first 1 to 8 bytes of the file to the function
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]836png_sig_cmp(), and it will return 0 (false) if the bytes match the
837corresponding bytes of the PNG signature, or nonzero (true) otherwise.
838Of course, the more bytes you pass in, the greater the accuracy of the
839prediction.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]840
841If you are intending to keep the file pointer open for use in libpng,
842you must ensure you don't read more than 8 bytes from the beginning
843of the file, and you also have to make a call to png_set_sig_bytes_read()
844with the number of bytes you read from the beginning. Libpng will
845then only check the bytes (if any) that your program didn't read.
846
847(*): If you are not using the standard I/O functions, you will need
848to replace them with custom functions. See the discussion under
849Customizing libpng.
850
851
852 FILE *fp = fopen(file_name, "rb");
853 if (!fp)
854 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]855 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]856 }
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]857
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]858 fread(header, 1, number, fp);
Glenn Randers-Pehrsonc9442291999-01-06 21:50:16 -0600[diff] [blame]859 is_png = !png_sig_cmp(header, 0, number);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]860
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]861 if (!is_png)
862 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]863 return (NOT_PNG);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]864 }
865
866
867Next, png_struct and png_info need to be allocated and initialized. In
868order to ensure that the size of these structures is correct even with a
869dynamically linked libpng, there are functions to initialize and
870allocate the structures. We also pass the library version, optional
871pointers to error handling functions, and a pointer to a data struct for
872use by the error functions, if necessary (the pointer and functions can
873be NULL if the default error handlers are to be used). See the section
874on Changes to Libpng below regarding the old initialization functions.
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]875The structure allocation functions quietly return NULL if they fail to
876create the structure, so your application should check for that.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]877
878 png_structp png_ptr = png_create_read_struct
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]879 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]880 user_error_fn, user_warning_fn);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]881
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]882 if (!png_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]883 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]884
885 png_infop info_ptr = png_create_info_struct(png_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]886
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]887 if (!info_ptr)
888 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]889 png_destroy_read_struct(&png_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]890 (png_infopp)NULL, (png_infopp)NULL);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]891 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]892 }
893
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]894If you want to use your own memory allocation routines,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]895use a libpng that was built with PNG_USER_MEM_SUPPORTED defined, and use
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]896png_create_read_struct_2() instead of png_create_read_struct():
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]897
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]898 png_structp png_ptr = png_create_read_struct_2
Glenn Randers-Pehrson20786be2011-04-20 22:20:40 -0500[diff] [blame]899 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]900 user_error_fn, user_warning_fn, (png_voidp)
901 user_mem_ptr, user_malloc_fn, user_free_fn);
902
903The error handling routines passed to png_create_read_struct()
904and the memory alloc/free routines passed to png_create_struct_2()
905are only necessary if you are not using the libpng supplied error
906handling and memory alloc/free functions.
907
908When libpng encounters an error, it expects to longjmp back
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]909to your routine. Therefore, you will need to call setjmp and pass
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]910your png_jmpbuf(png_ptr). If you read the file from different
John Bowlere6dc85b2011-04-27 14:47:15 -0500[diff] [blame]911routines, you will need to update the longjmp buffer every time you enter
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]912a new routine that will call a png_*() function.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]913
914See your documentation of setjmp/longjmp for your compiler for more
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]915information on setjmp/longjmp. See the discussion on libpng error
916handling in the Customizing Libpng section below for more information
917on the libpng error handling. If an error occurs, and libpng longjmp's
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]918back to your setjmp, you will want to call png_destroy_read_struct() to
919free any memory.
920
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]921 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]922 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]923 png_destroy_read_struct(&png_ptr, &info_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]924 &end_info);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]925 fclose(fp);
926 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]927 }
928
Glenn Randers-Pehrson20786be2011-04-20 22:20:40 -0500[diff] [blame]929Pass (png_infopp)NULL instead of &end_info if you didn't create
930an end_info structure.
931
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]932If you would rather avoid the complexity of setjmp/longjmp issues,
Glenn Randers-Pehrson54ac9a92010-04-02 17:06:22 -0500[diff] [blame]933you can compile libpng with PNG_NO_SETJMP, in which case
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]934errors will result in a call to PNG_ABORT() which defaults to abort().
935
Glenn Randers-Pehrson54ac9a92010-04-02 17:06:22 -0500[diff] [blame]936You can #define PNG_ABORT() to a function that does something
937more useful than abort(), as long as your function does not
938return.
939
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]940Now you need to set up the input code. The default for libpng is to
941use the C function fread(). If you use this, you will need to pass a
942valid FILE * in the function png_init_io(). Be sure that the file is
943opened in binary mode. If you wish to handle reading data in another
944way, you need not call the png_init_io() function, but you must then
945implement the libpng I/O methods discussed in the Customizing Libpng
946section below.
947
948 png_init_io(png_ptr, fp);
949
950If you had previously opened the file and read any of the signature from
951the beginning in order to see if this was a PNG file, you need to let
952libpng know that there are some bytes missing from the start of the file.
953
954 png_set_sig_bytes(png_ptr, number);
955
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]956You can change the zlib compression buffer size to be used while
957reading compressed data with
958
959 png_set_compression_buffer_size(png_ptr, buffer_size);
960
961where the default size is 8192 bytes. Note that the buffer size
962is changed immediately and the buffer is reallocated immediately,
963instead of setting a flag to be acted upon later.
964
Glenn Randers-Pehrson9dd1cdf2011-01-06 21:42:36 -0600[diff] [blame]965If you want CRC errors to be handled in a different manner than
966the default, use
967
968 png_set_crc_action(png_ptr, crit_action, ancil_action);
969
970The values for png_set_crc_action() say how libpng is to handle CRC errors in
971ancillary and critical chunks, and whether to use the data contained
972therein. Note that it is impossible to "discard" data in a critical
973chunk.
974
975Choices for (int) crit_action are
976 PNG_CRC_DEFAULT 0 error/quit
977 PNG_CRC_ERROR_QUIT 1 error/quit
978 PNG_CRC_WARN_USE 3 warn/use data
979 PNG_CRC_QUIET_USE 4 quiet/use data
980 PNG_CRC_NO_CHANGE 5 use the current value
981
982Choices for (int) ancil_action are
983 PNG_CRC_DEFAULT 0 error/quit
984 PNG_CRC_ERROR_QUIT 1 error/quit
985 PNG_CRC_WARN_DISCARD 2 warn/discard data
986 PNG_CRC_WARN_USE 3 warn/use data
987 PNG_CRC_QUIET_USE 4 quiet/use data
988 PNG_CRC_NO_CHANGE 5 use the current value
989
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]990.SS Setting up callback code
991
992You can set up a callback function to handle any unknown chunks in the
993input stream. You must supply the function
994
Glenn Randers-Pehrson81ce8892011-01-24 08:04:37 -0600[diff] [blame]995 read_chunk_callback(png_structp png_ptr,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]996 png_unknown_chunkp chunk);
997 {
998 /* The unknown chunk structure contains your
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]999 chunk data, along with similar data for any other
1000 unknown chunks: */
1001
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1002 png_byte name[5];
1003 png_byte *data;
1004 png_size_t size;
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1005
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1006 /* Note that libpng has already taken care of
1007 the CRC handling */
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1008
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1009 /* put your code here. Search for your chunk in the
1010 unknown chunk structure, process it, and return one
1011 of the following: */
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1012
Glenn Randers-Pehrson4dcbf242013-08-06 17:20:06 -0500[diff] [blame]1013 return (\-n); /* chunk had an error */
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1014 return (0); /* did not recognize */
1015 return (n); /* success */
1016 }
1017
1018(You can give your function another name that you like instead of
1019"read_chunk_callback")
1020
1021To inform libpng about your function, use
1022
1023 png_set_read_user_chunk_fn(png_ptr, user_chunk_ptr,
1024 read_chunk_callback);
1025
1026This names not only the callback function, but also a user pointer that
1027you can retrieve with
1028
1029 png_get_user_chunk_ptr(png_ptr);
1030
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1031If you call the png_set_read_user_chunk_fn() function, then all unknown
John Bowlere15b5372013-03-02 17:59:43 -0600[diff] [blame]1032chunks which the callback does not handle will be saved when read. You can
1033cause them to be discarded by returning '1' ("handled") instead of '0'. This
1034behavior will change in libpng 1.7 and the default handling set by the
1035png_set_keep_unknown_chunks() function, described below, will be used when the
1036callback returns 0. If you want the existing behavior you should set the global
1037default to PNG_HANDLE_CHUNK_IF_SAFE now; this is compatible with all current
1038versions of libpng and with 1.7. Libpng 1.6 issues a warning if you keep the
1039default, or PNG_HANDLE_CHUNK_NEVER, and the callback returns 0.
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1040
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]1041At this point, you can set up a callback function that will be
1042called after each row has been read, which you can use to control
1043a progress meter or the like. It's demonstrated in pngtest.c.
1044You must supply a function
1045
Glenn Randers-Pehrson81ce8892011-01-24 08:04:37 -0600[diff] [blame]1046 void read_row_callback(png_structp png_ptr,
1047 png_uint_32 row, int pass);
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]1048 {
1049 /* put your code here */
1050 }
1051
1052(You can give it another name that you like instead of "read_row_callback")
1053
1054To inform libpng about your function, use
1055
1056 png_set_read_status_fn(png_ptr, read_row_callback);
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1057
John Bowler59010e52011-02-16 06:16:31 -0600[diff] [blame]1058When this function is called the row has already been completely processed and
1059the 'row' and 'pass' refer to the next row to be handled. For the
1060non-interlaced case the row that was just handled is simply one less than the
1061passed in row number, and pass will always be 0. For the interlaced case the
1062same applies unless the row value is 0, in which case the row just handled was
1063the last one from one of the preceding passes. Because interlacing may skip a
Glenn Randers-Pehrson4dcbf242013-08-06 17:20:06 -0500[diff] [blame]1064pass you cannot be sure that the preceding pass is just 'pass\-1', if you really
John Bowler59010e52011-02-16 06:16:31 -0600[diff] [blame]1065need to know what the last pass is record (row,pass) from the callback and use
1066the last recorded value each time.
1067
1068As with the user transform you can find the output row using the
1069PNG_ROW_FROM_PASS_ROW macro.
1070
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1071.SS Unknown-chunk handling
1072
1073Now you get to set the way the library processes unknown chunks in the
1074input PNG stream. Both known and unknown chunks will be read. Normal
1075behavior is that known chunks will be parsed into information in
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1076various info_ptr members while unknown chunks will be discarded. This
1077behavior can be wasteful if your application will never use some known
1078chunk types. To change this, you can call:
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1079
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]1080 png_set_keep_unknown_chunks(png_ptr, keep,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1081 chunk_list, num_chunks);
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]1082
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1083 keep - 0: default unknown chunk handling
1084 1: ignore; do not keep
Glenn Randers-Pehrsond029a752004-08-09 21:50:32 -0500[diff] [blame]1085 2: keep only if safe-to-copy
1086 3: keep even if unsafe-to-copy
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1087
Glenn Randers-Pehrsond029a752004-08-09 21:50:32 -0500[diff] [blame]1088 You can use these definitions:
1089 PNG_HANDLE_CHUNK_AS_DEFAULT 0
1090 PNG_HANDLE_CHUNK_NEVER 1
1091 PNG_HANDLE_CHUNK_IF_SAFE 2
1092 PNG_HANDLE_CHUNK_ALWAYS 3
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1093
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1094 chunk_list - list of chunks affected (a byte string,
1095 five bytes per chunk, NULL or '\0' if
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]1096 num_chunks is positive; ignored if
1097 numchunks <= 0).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1098
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1099 num_chunks - number of chunks affected; if 0, all
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]1100 unknown chunks are affected. If positive,
1101 only the chunks in the list are affected,
1102 and if negative all unknown chunks and
1103 all known chunks except for the IHDR,
1104 PLTE, tRNS, IDAT, and IEND chunks are
1105 affected.
Glenn Randers-Pehrsondff799e2004-08-07 21:42:49 -0500[diff] [blame]1106
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1107Unknown chunks declared in this way will be saved as raw data onto a
1108list of png_unknown_chunk structures. If a chunk that is normally
1109known to libpng is named in the list, it will be handled as unknown,
1110according to the "keep" directive. If a chunk is named in successive
1111instances of png_set_keep_unknown_chunks(), the final instance will
Glenn Randers-Pehrsond029a752004-08-09 21:50:32 -0500[diff] [blame]1112take precedence. The IHDR and IEND chunks should not be named in
1113chunk_list; if they are, libpng will process them normally anyway.
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]1114If you know that your application will never make use of some particular
1115chunks, use PNG_HANDLE_CHUNK_NEVER (or 1) as demonstrated below.
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1116
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1117Here is an example of the usage of png_set_keep_unknown_chunks(),
1118where the private "vpAg" chunk will later be processed by a user chunk
1119callback function:
1120
1121 png_byte vpAg[5]={118, 112, 65, 103, (png_byte) '\0'};
1122
1123 #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
1124 png_byte unused_chunks[]=
1125 {
1126 104, 73, 83, 84, (png_byte) '\0', /* hIST */
1127 105, 84, 88, 116, (png_byte) '\0', /* iTXt */
1128 112, 67, 65, 76, (png_byte) '\0', /* pCAL */
1129 115, 67, 65, 76, (png_byte) '\0', /* sCAL */
1130 115, 80, 76, 84, (png_byte) '\0', /* sPLT */
1131 116, 73, 77, 69, (png_byte) '\0', /* tIME */
1132 };
1133 #endif
1134
1135 ...
1136
1137 #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
John Bowlere15b5372013-03-02 17:59:43 -0600[diff] [blame]1138 /* ignore all unknown chunks
1139 * (use global setting "2" for libpng16 and earlier):
1140 */
1141 png_set_keep_unknown_chunks(read_ptr, 2, NULL, 0);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1142
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1143 /* except for vpAg: */
1144 png_set_keep_unknown_chunks(read_ptr, 2, vpAg, 1);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1145
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1146 /* also ignore unused known chunks: */
1147 png_set_keep_unknown_chunks(read_ptr, 1, unused_chunks,
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]1148 (int)(sizeof unused_chunks)/5);
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1149 #endif
1150
Glenn Randers-Pehrson800d1e92008-08-20 17:25:21 -0500[diff] [blame]1151.SS User limits
1152
1153The PNG specification allows the width and height of an image to be as
Glenn Randers-Pehrson4dcbf242013-08-06 17:20:06 -0500[diff] [blame]1154large as 2^(31\-1 (0x7fffffff), or about 2.147 billion rows and columns.
Glenn Randers-Pehrson800d1e92008-08-20 17:25:21 -0500[diff] [blame]1155Since very few applications really need to process such large images,
1156we have imposed an arbitrary 1-million limit on rows and columns.
1157Larger images will be rejected immediately with a png_error() call. If
Glenn Randers-Pehrson0cb906d2011-06-11 14:22:22 -0500[diff] [blame]1158you wish to change this limit, you can use
Glenn Randers-Pehrson800d1e92008-08-20 17:25:21 -0500[diff] [blame]1159
1160 png_set_user_limits(png_ptr, width_max, height_max);
1161
1162to set your own limits, or use width_max = height_max = 0x7fffffffL
1163to allow all valid dimensions (libpng may reject some very large images
1164anyway because of potential buffer overflow conditions).
1165
1166You should put this statement after you create the PNG structure and
1167before calling png_read_info(), png_read_png(), or png_process_data().
Glenn Randers-Pehrsoncc277082011-06-10 21:17:34 -0500[diff] [blame]1168
1169When writing a PNG datastream, put this statement before calling
1170png_write_info() or png_write_png().
1171
Glenn Randers-Pehrson800d1e92008-08-20 17:25:21 -0500[diff] [blame]1172If you need to retrieve the limits that are being applied, use
1173
1174 width_max = png_get_user_width_max(png_ptr);
1175 height_max = png_get_user_height_max(png_ptr);
1176
1177The PNG specification sets no limit on the number of ancillary chunks
1178allowed in a PNG datastream. You can impose a limit on the total number
1179of sPLT, tEXt, iTXt, zTXt, and unknown chunks that will be stored, with
1180
1181 png_set_chunk_cache_max(png_ptr, user_chunk_cache_max);
1182
1183where 0x7fffffffL means unlimited. You can retrieve this limit with
1184
1185 chunk_cache_max = png_get_chunk_cache_max(png_ptr);
1186
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]1187You can also set a limit on the amount of memory that a compressed chunk
1188other than IDAT can occupy, with
1189
1190 png_set_chunk_malloc_max(png_ptr, user_chunk_malloc_max);
1191
1192and you can retrieve the limit with
1193
1194 chunk_malloc_max = png_get_chunk_malloc_max(png_ptr);
1195
1196Any chunks that would cause either of these limits to be exceeded will
1197be ignored.
1198
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1199.SS Information about your system
1200
1201If you intend to display the PNG or to incorporate it in other image data you
1202need to tell libpng information about your display or drawing surface so that
1203libpng can convert the values in the image to match the display.
1204
Glenn Randers-Pehrson733b1312011-06-15 13:21:01 -0500[diff] [blame]1205From libpng-1.5.4 this information can be set before reading the PNG file
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1206header. In earlier versions png_set_gamma() existed but behaved incorrectly if
1207called before the PNG file header had been read and png_set_alpha_mode() did not
1208exist.
1209
Glenn Randers-Pehrson733b1312011-06-15 13:21:01 -0500[diff] [blame]1210If you need to support versions prior to libpng-1.5.4 test the version number
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]1211as illustrated below using "PNG_LIBPNG_VER >= 10504" and follow the procedures
1212described in the appropriate manual page.
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1213
1214You give libpng the encoding expected by your system expressed as a 'gamma'
1215value. You can also specify a default encoding for the PNG file in
1216case the required information is missing from the file. By default libpng
1217assumes that the PNG data matches your system, to keep this default call:
1218
1219 png_set_gamma(png_ptr, screen_gamma, 1/screen_gamma/*file gamma*/);
1220
1221or you can use the fixed point equivalent:
1222
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]1223 png_set_gamma_fixed(png_ptr, PNG_FP_1*screen_gamma,
1224 PNG_FP_1/screen_gamma);
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1225
Glenn Randers-Pehrson95ba4172011-09-08 12:21:42 -0500[diff] [blame]1226If you don't know the gamma for your system it is probably 2.2 - a good
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1227approximation to the IEC standard for display systems (sRGB). If images are
1228too contrasty or washed out you got the value wrong - check your system
1229documentation!
1230
1231Many systems permit the system gamma to be changed via a lookup table in the
1232display driver, a few systems, including older Macs, change the response by
Glenn Randers-Pehrson733b1312011-06-15 13:21:01 -0500[diff] [blame]1233default. As of 1.5.4 three special values are available to handle common
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1234situations:
1235
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]1236 PNG_DEFAULT_sRGB: Indicates that the system conforms to the
1237 IEC 61966-2-1 standard. This matches almost
1238 all systems.
1239 PNG_GAMMA_MAC_18: Indicates that the system is an older
1240 (pre Mac OS 10.6) Apple Macintosh system with
1241 the default settings.
1242 PNG_GAMMA_LINEAR: Just the fixed point value for 1.0 - indicates
1243 that the system expects data with no gamma
1244 encoding.
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1245
1246You would use the linear (unencoded) value if you need to process the pixel
Glenn Randers-Pehrson4dcbf242013-08-06 17:20:06 -0500[diff] [blame]1247values further because this avoids the need to decode and re-encode each
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1248component value whenever arithmetic is performed. A lot of graphics software
1249uses linear values for this reason, often with higher precision component values
1250to preserve overall accuracy.
1251
1252The second thing you may need to tell libpng about is how your system handles
1253alpha channel information. Some, but not all, PNG files contain an alpha
1254channel. To display these files correctly you need to compose the data onto a
1255suitable background, as described in the PNG specification.
1256
1257Libpng only supports composing onto a single color (using png_set_background;
Glenn Randers-Pehrson95ba4172011-09-08 12:21:42 -0500[diff] [blame]1258see below). Otherwise you must do the composition yourself and, in this case,
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1259you may need to call png_set_alpha_mode:
1260
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]1261 #if PNG_LIBPNG_VER >= 10504
1262 png_set_alpha_mode(png_ptr, mode, screen_gamma);
1263 #else
1264 png_set_gamma(png_ptr, screen_gamma, 1.0/screen_gamma);
1265 #endif
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1266
Glenn Randers-Pehrson95ba4172011-09-08 12:21:42 -0500[diff] [blame]1267The screen_gamma value is the same as the argument to png_set_gamma; however,
1268how it affects the output depends on the mode. png_set_alpha_mode() sets the
1269file gamma default to 1/screen_gamma, so normally you don't need to call
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1270png_set_gamma. If you need different defaults call png_set_gamma() before
1271png_set_alpha_mode() - if you call it after it will override the settings made
1272by png_set_alpha_mode().
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1273
1274The mode is as follows:
1275
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1276 PNG_ALPHA_PNG: The data is encoded according to the PNG specification. Red,
1277green and blue, or gray, components are gamma encoded color
1278values and are not premultiplied by the alpha value. The
1279alpha value is a linear measure of the contribution of the
1280pixel to the corresponding final output pixel.
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1281
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1282You should normally use this format if you intend to perform
1283color correction on the color values; most, maybe all, color
1284correction software has no handling for the alpha channel and,
1285anyway, the math to handle pre-multiplied component values is
1286unnecessarily complex.
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1287
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1288Before you do any arithmetic on the component values you need
1289to remove the gamma encoding and multiply out the alpha
1290channel. See the PNG specification for more detail. It is
1291important to note that when an image with an alpha channel is
1292scaled, linear encoded, pre-multiplied component values must
1293be used!
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1294
1295The remaining modes assume you don't need to do any further color correction or
Glenn Randers-Pehrson95ba4172011-09-08 12:21:42 -0500[diff] [blame]1296that if you do, your color correction software knows all about alpha (it
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1297probably doesn't!)
1298
Glenn Randers-Pehrson95ba4172011-09-08 12:21:42 -0500[diff] [blame]1299 PNG_ALPHA_STANDARD: The data libpng produces
1300is encoded in the standard way
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1301assumed by most correctly written graphics software.
1302The gamma encoding will be removed by libpng and the
1303linear component values will be pre-multiplied by the
1304alpha channel.
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1305
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1306With this format the final image must be re-encoded to
1307match the display gamma before the image is displayed.
1308If your system doesn't do that, yet still seems to
1309perform arithmetic on the pixels without decoding them,
1310it is broken - check out the modes below.
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1311
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1312With PNG_ALPHA_STANDARD libpng always produces linear
1313component values, whatever screen_gamma you supply. The
1314screen_gamma value is, however, used as a default for
1315the file gamma if the PNG file has no gamma information.
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1316
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1317If you call png_set_gamma() after png_set_alpha_mode() you
1318will override the linear encoding. Instead the
1319pre-multiplied pixel values will be gamma encoded but
1320the alpha channel will still be linear. This may
1321actually match the requirements of some broken software,
1322but it is unlikely.
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1323
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1324While linear 8-bit data is often used it has
1325insufficient precision for any image with a reasonable
1326dynamic range. To avoid problems, and if your software
1327supports it, use png_set_expand_16() to force all
1328components to 16 bits.
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1329
Glenn Randers-Pehrson95ba4172011-09-08 12:21:42 -0500[diff] [blame]1330 PNG_ALPHA_OPTIMIZED: This mode is the same
1331as PNG_ALPHA_STANDARD except that
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1332completely opaque pixels are gamma encoded according to
1333the screen_gamma value. Pixels with alpha less than 1.0
1334will still have linear components.
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1335
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1336Use this format if you have control over your
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]1337compositing software and so don't do other arithmetic
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1338(such as scaling) on the data you get from libpng. Your
1339compositing software can simply copy opaque pixels to
1340the output but still has linear values for the
1341non-opaque pixels.
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1342
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1343In normal compositing, where the alpha channel encodes
1344partial pixel coverage (as opposed to broad area
1345translucency), the inaccuracies of the 8-bit
1346representation of non-opaque pixels are irrelevant.
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1347
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1348You can also try this format if your software is broken;
1349it might look better.
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1350
Glenn Randers-Pehrson95ba4172011-09-08 12:21:42 -0500[diff] [blame]1351 PNG_ALPHA_BROKEN: This is PNG_ALPHA_STANDARD;
1352however, all component values,
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1353including the alpha channel are gamma encoded. This is
1354an appropriate format to try if your software, or more
Glenn Randers-Pehrson95ba4172011-09-08 12:21:42 -0500[diff] [blame]1355likely hardware, is totally broken, i.e., if it performs
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1356linear arithmetic directly on gamma encoded values.
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1357
1358In most cases of broken software or hardware the bug in the final display
1359manifests as a subtle halo around composited parts of the image. You may not
1360even perceive this as a halo; the composited part of the image may simply appear
1361separate from the background, as though it had been cut out of paper and pasted
1362on afterward.
1363
1364If you don't have to deal with bugs in software or hardware, or if you can fix
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1365them, there are three recommended ways of using png_set_alpha_mode():
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1366
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1367 png_set_alpha_mode(png_ptr, PNG_ALPHA_PNG,
1368 screen_gamma);
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1369
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1370You can do color correction on the result (libpng does not currently
Glenn Randers-Pehrson95ba4172011-09-08 12:21:42 -0500[diff] [blame]1371support color correction internally). When you handle the alpha channel
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1372you need to undo the gamma encoding and multiply out the alpha.
1373
1374 png_set_alpha_mode(png_ptr, PNG_ALPHA_STANDARD,
1375 screen_gamma);
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1376 png_set_expand_16(png_ptr);
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1377
Glenn Randers-Pehrson95ba4172011-09-08 12:21:42 -0500[diff] [blame]1378If you are using the high level interface, don't call png_set_expand_16();
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1379instead pass PNG_TRANSFORM_EXPAND_16 to the interface.
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1380
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1381With this mode you can't do color correction, but you can do arithmetic,
1382including composition and scaling, on the data without further processing.
1383
1384 png_set_alpha_mode(png_ptr, PNG_ALPHA_OPTIMIZED,
1385 screen_gamma);
1386
1387You can avoid the expansion to 16-bit components with this mode, but you
1388lose the ability to scale the image or perform other linear arithmetic.
1389All you can do is compose the result onto a matching output. Since this
Glenn Randers-Pehrson95ba4172011-09-08 12:21:42 -0500[diff] [blame]1390mode is libpng-specific you also need to write your own composition
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1391software.
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1392
1393If you don't need, or can't handle, the alpha channel you can call
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1394png_set_background() to remove it by compositing against a fixed color. Don't
1395call png_set_strip_alpha() to do this - it will leave spurious pixel values in
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1396transparent parts of this image.
1397
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]1398 png_set_background(png_ptr, &background_color,
1399 PNG_BACKGROUND_GAMMA_SCREEN, 0, 1);
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1400
1401The background_color is an RGB or grayscale value according to the data format
1402libpng will produce for you. Because you don't yet know the format of the PNG
Glenn Randers-Pehrson95ba4172011-09-08 12:21:42 -0500[diff] [blame]1403file, if you call png_set_background at this point you must arrange for the
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1404format produced by libpng to always have 8-bit or 16-bit components and then
1405store the color as an 8-bit or 16-bit color as appropriate. The color contains
1406separate gray and RGB component values, so you can let libpng produce gray or
1407RGB output according to the input format, but low bit depth grayscale images
Glenn Randers-Pehrsonab389792011-07-09 19:35:22 -0500[diff] [blame]1408must always be converted to at least 8-bit format. (Even though low bit depth
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1409grayscale images can't have an alpha channel they can have a transparent
1410color!)
1411
1412You set the transforms you need later, either as flags to the high level
1413interface or libpng API calls for the low level interface. For reference the
Glenn Randers-Pehrson733b1312011-06-15 13:21:01 -0500[diff] [blame]1414settings and API calls required are:
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1415
14168-bit values:
Glenn Randers-Pehrsonfb29e512011-06-17 20:38:24 -0500[diff] [blame]1417 PNG_TRANSFORM_SCALE_16 | PNG_EXPAND
1418 png_set_expand(png_ptr); png_set_scale_16(png_ptr);
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1419
Glenn Randers-Pehrson733b1312011-06-15 13:21:01 -0500[diff] [blame]1420 If you must get exactly the same inaccurate results
1421 produced by default in versions prior to libpng-1.5.4,
Glenn Randers-Pehrsonfb29e512011-06-17 20:38:24 -0500[diff] [blame]1422 use PNG_TRANSFORM_STRIP_16 and png_set_strip_16(png_ptr)
Glenn Randers-Pehrson733b1312011-06-15 13:21:01 -0500[diff] [blame]1423 instead.
1424
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]142516-bit values:
1426 PNG_TRANSFORM_EXPAND_16
1427 png_set_expand_16(png_ptr);
1428
1429In either case palette image data will be expanded to RGB. If you just want
1430color data you can add PNG_TRANSFORM_GRAY_TO_RGB or png_set_gray_to_rgb(png_ptr)
1431to the list.
1432
1433Calling png_set_background before the PNG file header is read will not work
Glenn Randers-Pehrson733b1312011-06-15 13:21:01 -0500[diff] [blame]1434prior to libpng-1.5.4. Because the failure may result in unexpected warnings or
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1435errors it is therefore much safer to call png_set_background after the head has
Glenn Randers-Pehrson733b1312011-06-15 13:21:01 -0500[diff] [blame]1436been read. Unfortunately this means that prior to libpng-1.5.4 it cannot be
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1437used with the high level interface.
1438
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1439.SS The high-level read interface
1440
1441At this point there are two ways to proceed; through the high-level
1442read interface, or through a sequence of low-level read operations.
1443You can use the high-level interface if (a) you are willing to read
1444the entire image into memory, and (b) the input transformations
1445you want to do are limited to the following set:
1446
1447 PNG_TRANSFORM_IDENTITY No transformation
Glenn Randers-Pehrsonfb29e512011-06-17 20:38:24 -0500[diff] [blame]1448 PNG_TRANSFORM_SCALE_16 Strip 16-bit samples to
1449 8-bit accurately
1450 PNG_TRANSFORM_STRIP_16 Chop 16-bit samples to
1451 8-bit less accurately
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1452 PNG_TRANSFORM_STRIP_ALPHA Discard the alpha channel
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1453 PNG_TRANSFORM_PACKING Expand 1, 2 and 4-bit
1454 samples to bytes
1455 PNG_TRANSFORM_PACKSWAP Change order of packed
1456 pixels to LSB first
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1457 PNG_TRANSFORM_EXPAND Perform set_expand()
1458 PNG_TRANSFORM_INVERT_MONO Invert monochrome images
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1459 PNG_TRANSFORM_SHIFT Normalize pixels to the
1460 sBIT depth
1461 PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA
1462 to BGRA
1463 PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA
1464 to AG
1465 PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity
1466 to transparency
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1467 PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples
Glenn Randers-Pehrson99708d52009-06-29 17:30:00 -0500[diff] [blame]1468 PNG_TRANSFORM_GRAY_TO_RGB Expand grayscale samples
1469 to RGB (or GA to RGBA)
John Bowlera9b34192011-05-08 19:46:51 -0500[diff] [blame]1470 PNG_TRANSFORM_EXPAND_16 Expand samples to 16 bits
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1471
1472(This excludes setting a background color, doing gamma transformation,
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]1473quantizing, and setting filler.) If this is the case, simply do this:
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1474
1475 png_read_png(png_ptr, info_ptr, png_transforms, NULL)
1476
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]1477where png_transforms is an integer containing the bitwise OR of some
1478set of transformation flags. This call is equivalent to png_read_info(),
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1479followed the set of transformations indicated by the transform mask,
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1480then png_read_image(), and finally png_read_end().
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1481
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1482(The final parameter of this call is not yet used. Someday it might point
1483to transformation parameters required by some future input transform.)
1484
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]1485You must use png_transforms and not call any png_set_transform() functions
1486when you use png_read_png().
1487
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1488After you have called png_read_png(), you can retrieve the image data
1489with
1490
1491 row_pointers = png_get_rows(png_ptr, info_ptr);
1492
1493where row_pointers is an array of pointers to the pixel data for each row:
1494
1495 png_bytep row_pointers[height];
1496
1497If you know your image size and pixel size ahead of time, you can allocate
1498row_pointers prior to calling png_read_png() with
1499
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]1500 if (height > PNG_UINT_32_MAX/(sizeof (png_byte)))
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]1501 png_error (png_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1502 "Image is too tall to process in memory");
1503
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]1504 if (width > PNG_UINT_32_MAX/pixel_size)
1505 png_error (png_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1506 "Image is too wide to process in memory");
1507
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1508 row_pointers = png_malloc(png_ptr,
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]1509 height*(sizeof (png_bytep)));
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1510
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1511 for (int i=0; i<height, i++)
1512 row_pointers[i]=NULL; /* security precaution */
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1513
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1514 for (int i=0; i<height, i++)
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1515 row_pointers[i]=png_malloc(png_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1516 width*pixel_size);
1517
Glenn Randers-Pehrsond56aca72000-11-23 11:51:42 -0600[diff] [blame]1518 png_set_rows(png_ptr, info_ptr, &row_pointers);
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1519
1520Alternatively you could allocate your image in one big block and define
1521row_pointers[i] to point into the proper places in your block.
1522
1523If you use png_set_rows(), the application is responsible for freeing
1524row_pointers (and row_pointers[i], if they were separately allocated).
1525
1526If you don't allocate row_pointers ahead of time, png_read_png() will
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1527do it, and it'll be free'ed by libpng when you call png_destroy_*().
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1528
1529.SS The low-level read interface
1530
1531If you are going the low-level route, you are now ready to read all
1532the file information up to the actual image data. You do this with a
1533call to png_read_info().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1534
1535 png_read_info(png_ptr, info_ptr);
1536
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1537This will process all chunks up to but not including the image data.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1538
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1539This also copies some of the data from the PNG file into the decode structure
1540for use in later transformations. Important information copied in is:
1541
15421) The PNG file gamma from the gAMA chunk. This overwrites the default value
1543provided by an earlier call to png_set_gamma or png_set_alpha_mode.
1544
Glenn Randers-Pehrson733b1312011-06-15 13:21:01 -0500[diff] [blame]15452) Prior to libpng-1.5.4 the background color from a bKGd chunk. This
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1546damages the information provided by an earlier call to png_set_background
Glenn Randers-Pehrsonab389792011-07-09 19:35:22 -0500[diff] [blame]1547resulting in unexpected behavior. Libpng-1.5.4 no longer does this.
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1548
15493) The number of significant bits in each component value. Libpng uses this to
1550optimize gamma handling by reducing the internal lookup table sizes.
1551
15524) The transparent color information from a tRNS chunk. This can be modified by
1553a later call to png_set_tRNS.
1554
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1555.SS Querying the info structure
1556
1557Functions are used to get the information from the info_ptr once it
1558has been read. Note that these fields may not be completely filled
1559in until png_read_end() has read the chunk data following the image.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1560
1561 png_get_IHDR(png_ptr, info_ptr, &width, &height,
1562 &bit_depth, &color_type, &interlace_type,
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]1563 &compression_type, &filter_method);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1564
1565 width - holds the width of the image
1566 in pixels (up to 2^31).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1567
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1568 height - holds the height of the image
1569 in pixels (up to 2^31).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1570
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1571 bit_depth - holds the bit depth of one of the
1572 image channels. (valid values are
1573 1, 2, 4, 8, 16 and depend also on
1574 the color_type. See also
1575 significant bits (sBIT) below).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1576
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1577 color_type - describes which color/alpha channels
1578 are present.
1579 PNG_COLOR_TYPE_GRAY
1580 (bit depths 1, 2, 4, 8, 16)
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1581 PNG_COLOR_TYPE_GRAY_ALPHA
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1582 (bit depths 8, 16)
1583 PNG_COLOR_TYPE_PALETTE
1584 (bit depths 1, 2, 4, 8)
1585 PNG_COLOR_TYPE_RGB
1586 (bit_depths 8, 16)
1587 PNG_COLOR_TYPE_RGB_ALPHA
1588 (bit_depths 8, 16)
1589
1590 PNG_COLOR_MASK_PALETTE
1591 PNG_COLOR_MASK_COLOR
1592 PNG_COLOR_MASK_ALPHA
1593
Glenn Randers-Pehrson2cb633b2011-01-21 08:31:29 -0600[diff] [blame]1594 interlace_type - (PNG_INTERLACE_NONE or
1595 PNG_INTERLACE_ADAM7)
1596
1597 compression_type - (must be PNG_COMPRESSION_TYPE_BASE
1598 for PNG 1.0)
1599
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]1600 filter_method - (must be PNG_FILTER_TYPE_BASE
1601 for PNG 1.0, and can also be
1602 PNG_INTRAPIXEL_DIFFERENCING if
1603 the PNG datastream is embedded in
1604 a MNG-1.0 datastream)
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1605
1606 Any or all of interlace_type, compression_type, or
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1607 filter_method can be NULL if you are
1608 not interested in their values.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1609
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1610 Note that png_get_IHDR() returns 32-bit data into
1611 the application's width and height variables.
1612 This is an unsafe situation if these are 16-bit
1613 variables. In such situations, the
1614 png_get_image_width() and png_get_image_height()
1615 functions described below are safer.
1616
1617 width = png_get_image_width(png_ptr,
1618 info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1619
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1620 height = png_get_image_height(png_ptr,
1621 info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1622
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1623 bit_depth = png_get_bit_depth(png_ptr,
1624 info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1625
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1626 color_type = png_get_color_type(png_ptr,
1627 info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1628
Glenn Randers-Pehrson2cb633b2011-01-21 08:31:29 -0600[diff] [blame]1629 interlace_type = png_get_interlace_type(png_ptr,
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1630 info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1631
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1632 compression_type = png_get_compression_type(png_ptr,
1633 info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1634
Glenn Randers-Pehrson2cb633b2011-01-21 08:31:29 -0600[diff] [blame]1635 filter_method = png_get_filter_type(png_ptr,
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1636 info_ptr);
1637
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1638 channels = png_get_channels(png_ptr, info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1639
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1640 channels - number of channels of info for the
1641 color type (valid values are 1 (GRAY,
1642 PALETTE), 2 (GRAY_ALPHA), 3 (RGB),
1643 4 (RGB_ALPHA or RGB + filler byte))
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1644
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1645 rowbytes = png_get_rowbytes(png_ptr, info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1646
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1647 rowbytes - number of bytes needed to hold a row
1648
1649 signature = png_get_signature(png_ptr, info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1650
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1651 signature - holds the signature read from the
1652 file (if any). The data is kept in
1653 the same offset it would be if the
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1654 whole signature were read (i.e. if an
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1655 application had already read in 4
1656 bytes of signature before starting
1657 libpng, the remaining 4 bytes would
1658 be in signature[4] through signature[7]
1659 (see png_set_sig_bytes())).
1660
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1661These are also important, but their validity depends on whether the chunk
1662has been read. The png_get_valid(png_ptr, info_ptr, PNG_INFO_<chunk>) and
1663png_get_<chunk>(png_ptr, info_ptr, ...) functions return non-zero if the
1664data has been read, or zero if it is missing. The parameters to the
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]1665png_get_<chunk> are set directly if they are simple data types, or a
1666pointer into the info_ptr is returned for any complex types.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1667
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]1668The colorspace data from gAMA, cHRM, sRGB, iCCP, and sBIT chunks
1669is simply returned to give the application information about how the
1670image was encoded. Libpng itself only does transformations using the file
1671gamma when combining semitransparent pixels with the background color, and,
1672since libpng-1.6.0, when converting between 8-bit sRGB and 16-bit linear pixels
1673within the simplified API. Libpng also uses the file gamma when converting
1674RGB to gray, beginning with libpng-1.0.5, if the application calls
1675png_set_rgb_to_gray()).
1676
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1677 png_get_PLTE(png_ptr, info_ptr, &palette,
1678 &num_palette);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1679
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1680 palette - the palette for the file
1681 (array of png_color)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1682
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1683 num_palette - number of entries in the palette
1684
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]1685 png_get_gAMA(png_ptr, info_ptr, &file_gamma);
Glenn Randers-Pehrson27742382011-01-27 09:37:34 -0600[diff] [blame]1686 png_get_gAMA_fixed(png_ptr, info_ptr, &int_file_gamma);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1687
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]1688 file_gamma - the gamma at which the file is
1689 written (PNG_INFO_gAMA)
1690
1691 int_file_gamma - 100,000 times the gamma at which the
1692 file is written
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1693
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]1694 png_get_cHRM(png_ptr, info_ptr, &white_x, &white_y, &red_x,
1695 &red_y, &green_x, &green_y, &blue_x, &blue_y)
1696 png_get_cHRM_XYZ(png_ptr, info_ptr, &red_X, &red_Y, &red_Z,
1697 &green_X, &green_Y, &green_Z, &blue_X, &blue_Y,
1698 &blue_Z)
1699 png_get_cHRM_fixed(png_ptr, info_ptr, &int_white_x,
1700 &int_white_y, &int_red_x, &int_red_y,
1701 &int_green_x, &int_green_y, &int_blue_x,
1702 &int_blue_y)
John Bowlerbbd17bd2011-08-25 17:48:18 -0500[diff] [blame]1703 png_get_cHRM_XYZ_fixed(png_ptr, info_ptr, &int_red_X, &int_red_Y,
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]1704 &int_red_Z, &int_green_X, &int_green_Y,
1705 &int_green_Z, &int_blue_X, &int_blue_Y,
1706 &int_blue_Z)
John Bowlerbbd17bd2011-08-25 17:48:18 -0500[diff] [blame]1707
1708 {white,red,green,blue}_{x,y}
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]1709 A color space encoding specified using the
1710 chromaticities of the end points and the
1711 white point. (PNG_INFO_cHRM)
John Bowlerbbd17bd2011-08-25 17:48:18 -0500[diff] [blame]1712
1713 {red,green,blue}_{X,Y,Z}
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]1714 A color space encoding specified using the
1715 encoding end points - the CIE tristimulus
1716 specification of the intended color of the red,
1717 green and blue channels in the PNG RGB data.
1718 The white point is simply the sum of the three
1719 end points. (PNG_INFO_cHRM)
John Bowlerbbd17bd2011-08-25 17:48:18 -0500[diff] [blame]1720
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1721 png_get_sRGB(png_ptr, info_ptr, &srgb_intent);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1722
Glenn Randers-Pehrson27742382011-01-27 09:37:34 -0600[diff] [blame]1723 file_srgb_intent - the rendering intent (PNG_INFO_sRGB)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1724 The presence of the sRGB chunk
1725 means that the pixel data is in the
1726 sRGB color space. This chunk also
1727 implies specific values of gAMA and
1728 cHRM.
1729
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1730 png_get_iCCP(png_ptr, info_ptr, &name,
1731 &compression_type, &profile, &proflen);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1732
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]1733 name - The profile name.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1734
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]1735 compression_type - The compression type; always
1736 PNG_COMPRESSION_TYPE_BASE for PNG 1.0.
1737 You may give NULL to this argument to
1738 ignore it.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1739
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]1740 profile - International Color Consortium color
1741 profile data. May contain NULs.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1742
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]1743 proflen - length of profile data in bytes.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1744
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1745 png_get_sBIT(png_ptr, info_ptr, &sig_bit);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1746
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1747 sig_bit - the number of significant bits for
1748 (PNG_INFO_sBIT) each of the gray,
1749 red, green, and blue channels,
1750 whichever are appropriate for the
1751 given color type (png_color_16)
1752
Glenn Randers-Pehrson866b62a2009-08-08 16:33:14 -0500[diff] [blame]1753 png_get_tRNS(png_ptr, info_ptr, &trans_alpha,
1754 &num_trans, &trans_color);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1755
Glenn Randers-Pehrson866b62a2009-08-08 16:33:14 -0500[diff] [blame]1756 trans_alpha - array of alpha (transparency)
1757 entries for palette (PNG_INFO_tRNS)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1758
Glenn Randers-Pehrsonf3c51e42011-01-15 10:25:25 -0600[diff] [blame]1759 num_trans - number of transparent entries
1760 (PNG_INFO_tRNS)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1761
Glenn Randers-Pehrson56f63962008-10-06 10:16:17 -0500[diff] [blame]1762 trans_color - graylevel or color sample values of
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]1763 the single transparent color for
1764 non-paletted images (PNG_INFO_tRNS)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1765
1766 png_get_hIST(png_ptr, info_ptr, &hist);
1767 (PNG_INFO_hIST)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1768
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1769 hist - histogram of palette (array of
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1770 png_uint_16)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1771
1772 png_get_tIME(png_ptr, info_ptr, &mod_time);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1773
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1774 mod_time - time image was last modified
1775 (PNG_VALID_tIME)
1776
1777 png_get_bKGD(png_ptr, info_ptr, &background);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1778
Glenn Randers-Pehrsonab389792011-07-09 19:35:22 -0500[diff] [blame]1779 background - background color (of type
1780 png_color_16p) (PNG_VALID_bKGD)
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1781 valid 16-bit red, green and blue
1782 values, regardless of color_type
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1783
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]1784 num_comments = png_get_text(png_ptr, info_ptr,
1785 &text_ptr, &num_text);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1786
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]1787 num_comments - number of comments
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1788
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1789 text_ptr - array of png_text holding image
1790 comments
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1791
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1792 text_ptr[i].compression - type of compression used
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1793 on "text" PNG_TEXT_COMPRESSION_NONE
1794 PNG_TEXT_COMPRESSION_zTXt
1795 PNG_ITXT_COMPRESSION_NONE
1796 PNG_ITXT_COMPRESSION_zTXt
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1797
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1798 text_ptr[i].key - keyword for comment. Must contain
1799 1-79 characters.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1800
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1801 text_ptr[i].text - text comments for current
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]1802 keyword. Can be empty.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1803
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1804 text_ptr[i].text_length - length of text string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1805 after decompression, 0 for iTXt
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1806
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1807 text_ptr[i].itxt_length - length of itxt string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1808 after decompression, 0 for tEXt/zTXt
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1809
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1810 text_ptr[i].lang - language of comment (empty
1811 string for unknown).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1812
Glenn Randers-Pehrson73d57cb2002-03-25 18:49:08 -0600[diff] [blame]1813 text_ptr[i].lang_key - keyword in UTF-8
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1814 (empty string for unknown).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1815
Glenn Randers-Pehrson8f5846f2009-10-31 21:31:08 -0500[diff] [blame]1816 Note that the itxt_length, lang, and lang_key
Glenn Randers-Pehrson680da022011-11-21 17:05:41 -0600[diff] [blame]1817 members of the text_ptr structure only exist when the
1818 library is built with iTXt chunk support. Prior to
1819 libpng-1.4.0 the library was built by default without
1820 iTXt support. Also note that when iTXt is supported,
1821 they contain NULL pointers when the "compression"
1822 field contains PNG_TEXT_COMPRESSION_NONE or
1823 PNG_TEXT_COMPRESSION_zTXt.
Glenn Randers-Pehrson8f5846f2009-10-31 21:31:08 -0500[diff] [blame]1824
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1825 num_text - number of comments (same as
1826 num_comments; you can put NULL here
1827 to avoid the duplication)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1828
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1829 Note while png_set_text() will accept text, language,
1830 and translated keywords that can be NULL pointers, the
1831 structure returned by png_get_text will always contain
1832 regular zero-terminated C strings. They might be
1833 empty strings but they will never be NULL pointers.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1834
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1835 num_spalettes = png_get_sPLT(png_ptr, info_ptr,
1836 &palette_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1837
1838 num_spalettes - number of sPLT chunks read.
1839
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1840 palette_ptr - array of palette structures holding
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1841 contents of one or more sPLT chunks
1842 read.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1843
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1844 png_get_oFFs(png_ptr, info_ptr, &offset_x, &offset_y,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1845 &unit_type);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1846
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1847 offset_x - positive offset from the left edge
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]1848 of the screen (can be negative)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1849
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1850 offset_y - positive offset from the top edge
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]1851 of the screen (can be negative)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1852
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1853 unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
1854
1855 png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1856 &unit_type);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1857
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1858 res_x - pixels/unit physical resolution in
1859 x direction
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1860
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1861 res_y - pixels/unit physical resolution in
1862 x direction
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1863
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1864 unit_type - PNG_RESOLUTION_UNKNOWN,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1865 PNG_RESOLUTION_METER
1866
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1867 png_get_sCAL(png_ptr, info_ptr, &unit, &width,
1868 &height)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1869
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1870 unit - physical scale units (an integer)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1871
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1872 width - width of a pixel in physical scale units
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1873
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1874 height - height of a pixel in physical scale units
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1875 (width and height are doubles)
1876
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1877 png_get_sCAL_s(png_ptr, info_ptr, &unit, &width,
1878 &height)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1879
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1880 unit - physical scale units (an integer)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1881
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1882 width - width of a pixel in physical scale units
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]1883 (expressed as a string)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1884
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1885 height - height of a pixel in physical scale units
1886 (width and height are strings like "2.54")
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1887
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1888 num_unknown_chunks = png_get_unknown_chunks(png_ptr,
1889 info_ptr, &unknowns)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1890
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1891 unknowns - array of png_unknown_chunk
1892 structures holding unknown chunks
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1893
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1894 unknowns[i].name - name of unknown chunk
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1895
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1896 unknowns[i].data - data of unknown chunk
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1897
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1898 unknowns[i].size - size of unknown chunk's data
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1899
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1900 unknowns[i].location - position of chunk in file
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1901
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1902 The value of "i" corresponds to the order in which the
1903 chunks were read from the PNG file or inserted with the
1904 png_set_unknown_chunks() function.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1905
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]1906 The value of "location" is a bitwise "or" of
1907
1908 PNG_HAVE_IHDR (0x01)
1909 PNG_HAVE_PLTE (0x02)
1910 PNG_AFTER_IDAT (0x08)
1911
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1912The data from the pHYs chunk can be retrieved in several convenient
1913forms:
1914
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1915 res_x = png_get_x_pixels_per_meter(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1916 info_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1917
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1918 res_y = png_get_y_pixels_per_meter(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1919 info_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1920
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1921 res_x_and_y = png_get_pixels_per_meter(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1922 info_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1923
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1924 res_x = png_get_x_pixels_per_inch(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1925 info_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1926
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1927 res_y = png_get_y_pixels_per_inch(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1928 info_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1929
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1930 res_x_and_y = png_get_pixels_per_inch(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1931 info_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1932
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1933 aspect_ratio = png_get_pixel_aspect_ratio(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1934 info_ptr)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1935
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1936 Each of these returns 0 [signifying "unknown"] if
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1937 the data is not present or if res_x is 0;
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1938 res_x_and_y is 0 if res_x != res_y
1939
1940 Note that because of the way the resolutions are
1941 stored internally, the inch conversions won't
1942 come out to exactly even number. For example,
1943 72 dpi is stored as 0.28346 pixels/meter, and
1944 when this is retrieved it is 71.9988 dpi, so
1945 be sure to round the returned value appropriately
Glenn Randers-Pehrsonc36bb792011-02-12 09:49:07 -0600[diff] [blame]1946 if you want to display a reasonable-looking result.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1947
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1948The data from the oFFs chunk can be retrieved in several convenient
1949forms:
1950
1951 x_offset = png_get_x_offset_microns(png_ptr, info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1952
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1953 y_offset = png_get_y_offset_microns(png_ptr, info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1954
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1955 x_offset = png_get_x_offset_inches(png_ptr, info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1956
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1957 y_offset = png_get_y_offset_inches(png_ptr, info_ptr);
1958
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1959 Each of these returns 0 [signifying "unknown" if both
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1960 x and y are 0] if the data is not present or if the
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1961 chunk is present but the unit is the pixel. The
1962 remark about inexact inch conversions applies here
1963 as well, because a value in inches can't always be
1964 converted to microns and back without some loss
1965 of precision.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1966
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]1967For more information, see the
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1968PNG specification for chunk contents. Be careful with trusting
1969rowbytes, as some of the transformations could increase the space
1970needed to hold a row (expand, filler, gray_to_rgb, etc.).
1971See png_read_update_info(), below.
1972
1973A quick word about text_ptr and num_text. PNG stores comments in
1974keyword/text pairs, one pair per chunk, with no limit on the number
1975of text chunks, and a 2^31 byte limit on their size. While there are
1976suggested keywords, there is no requirement to restrict the use to these
1977strings. It is strongly suggested that keywords and text be sensible
1978to humans (that's the point), so don't use abbreviations. Non-printing
1979symbols are not allowed. See the PNG specification for more details.
1980There is also no requirement to have text after the keyword.
1981
1982Keywords should be limited to 79 Latin-1 characters without leading or
1983trailing spaces, but non-consecutive spaces are allowed within the
1984keyword. It is possible to have the same keyword any number of times.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1985The text_ptr is an array of png_text structures, each holding a
1986pointer to a language string, a pointer to a keyword and a pointer to
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1987a text string. The text string, language code, and translated
1988keyword may be empty or NULL pointers. The keyword/text
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1989pairs are put into the array in the order that they are received.
1990However, some or all of the text chunks may be after the image, so, to
1991make sure you have read all the text chunks, don't mess with these
1992until after you read the stuff after the image. This will be
1993mentioned again below in the discussion that goes with png_read_end().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1994
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1995.SS Input transformations
1996
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1997After you've read the header information, you can set up the library
1998to handle any special transformations of the image data. The various
1999ways to transform the data will be described in the order that they
2000should occur. This is important, as some of these change the color
2001type and/or bit depth of the data, and some others only work on
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2002certain color types and bit depths.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2003
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2004Transformations you request are ignored if they don't have any meaning for a
2005particular input data format. However some transformations can have an effect
2006as a result of a previous transformation. If you specify a contradictory set of
2007transformations, for example both adding and removing the alpha channel, you
2008cannot predict the final result.
2009
2010The color used for the transparency values should be supplied in the same
2011format/depth as the current image data. It is stored in the same format/depth
2012as the image data in a tRNS chunk, so this is what libpng expects for this data.
2013
2014The color used for the background value depends on the need_expand argument as
2015described below.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2016
2017Data will be decoded into the supplied row buffers packed into bytes
2018unless the library has been told to transform it into another format.
2019For example, 4 bit/pixel paletted or grayscale data will be returned
20202 pixels/byte with the leftmost pixel in the high-order bits of the
2021byte, unless png_set_packing() is called. 8-bit RGB data will be stored
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]2022in RGB RGB RGB format unless png_set_filler() or png_set_add_alpha()
2023is called to insert filler bytes, either before or after each RGB triplet.
202416-bit RGB data will be returned RRGGBB RRGGBB, with the most significant
Glenn Randers-Pehrsonfb29e512011-06-17 20:38:24 -0500[diff] [blame]2025byte of the color value first, unless png_set_scale_16() is called to
Glenn Randers-Pehrson16e11662004-11-01 14:13:40 -0600[diff] [blame]2026transform it to regular RGB RGB triplets, or png_set_filler() or
2027png_set_add alpha() is called to insert filler bytes, either before or
2028after each RRGGBB triplet. Similarly, 8-bit or 16-bit grayscale data can
Glenn Randers-Pehrsonfb29e512011-06-17 20:38:24 -0500[diff] [blame]2029be modified with png_set_filler(), png_set_add_alpha(), png_set_strip_16(),
2030or png_set_scale_16().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2031
2032The following code transforms grayscale images of less than 8 to 8 bits,
2033changes paletted images to RGB, and adds a full alpha channel if there is
2034transparency information in a tRNS chunk. This is most useful on
2035grayscale images with bit depths of 2 or 4 or if there is a multiple-image
2036viewing application that wishes to treat all images in the same way.
2037
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2038 if (color_type == PNG_COLOR_TYPE_PALETTE)
2039 png_set_palette_to_rgb(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2040
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2041 if (png_get_valid(png_ptr, info_ptr,
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]2042 PNG_INFO_tRNS)) png_set_tRNS_to_alpha(png_ptr);
2043
Glenn Randers-Pehrsonc36bb792011-02-12 09:49:07 -0600[diff] [blame]2044 if (color_type == PNG_COLOR_TYPE_GRAY &&
2045 bit_depth < 8) png_set_expand_gray_1_2_4_to_8(png_ptr);
2046
2047The first two functions are actually aliases for png_set_expand(), added
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]2048in libpng version 1.0.4, with the function names expanded to improve code
2049readability. In some future version they may actually do different
2050things.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2051
Glenn Randers-Pehrson1ce08362006-03-08 23:35:59 -0600[diff] [blame]2052As of libpng version 1.2.9, png_set_expand_gray_1_2_4_to_8() was
2053added. It expands the sample depth without changing tRNS to alpha.
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]2054
John Bowler63d059a2011-02-12 09:03:44 -0600[diff] [blame]2055As of libpng version 1.5.2, png_set_expand_16() was added. It behaves as
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]2056png_set_expand(); however, the resultant channels have 16 bits rather than 8.
Glenn Randers-Pehrsonc36bb792011-02-12 09:49:07 -0600[diff] [blame]2057Use this when the output color or gray channels are made linear to avoid fairly
John Bowler63d059a2011-02-12 09:03:44 -0600[diff] [blame]2058severe accuracy loss.
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]2059
John Bowler63d059a2011-02-12 09:03:44 -0600[diff] [blame]2060 if (bit_depth < 16)
2061 png_set_expand_16(png_ptr);
Glenn Randers-Pehrson1ce08362006-03-08 23:35:59 -0600[diff] [blame]2062
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2063PNG can have files with 16 bits per channel. If you only can handle
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]20648 bits per channel, this will strip the pixels down to 8-bit.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2065
2066 if (bit_depth == 16)
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]2067#if PNG_LIBPNG_VER >= 10504
Glenn Randers-Pehrsonfb29e512011-06-17 20:38:24 -0500[diff] [blame]2068 png_set_scale_16(png_ptr);
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]2069#else
2070 png_set_strip_16(png_ptr);
2071#endif
2072
2073(The more accurate "png_set_scale_16()" API became available in libpng version
20741.5.4).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2075
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2076If you need to process the alpha channel on the image separately from the image
2077data (for example if you convert it to a bitmap mask) it is possible to have
2078libpng strip the channel leaving just RGB or gray data:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2079
2080 if (color_type & PNG_COLOR_MASK_ALPHA)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2081 png_set_strip_alpha(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2082
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2083If you strip the alpha channel you need to find some other way of dealing with
2084the information. If, instead, you want to convert the image to an opaque
2085version with no alpha channel use png_set_background; see below.
John Bowler63d059a2011-02-12 09:03:44 -0600[diff] [blame]2086
2087As of libpng version 1.5.2, almost all useful expansions are supported, the
Glenn Randers-Pehrsoncd116fa2011-05-17 06:56:50 -0500[diff] [blame]2088major ommissions are conversion of grayscale to indexed images (which can be
2089done trivially in the application) and conversion of indexed to grayscale (which
John Bowler63d059a2011-02-12 09:03:44 -0600[diff] [blame]2090can be done by a trivial manipulation of the palette.)
2091
2092In the following table, the 01 means grayscale with depth<8, 31 means
2093indexed with depth<8, other numerals represent the color type, "T" means
2094the tRNS chunk is present, A means an alpha channel is present, and O
2095means tRNS or alpha is present but all pixels in the image are opaque.
2096
Glenn Randers-Pehrsonc36bb792011-02-12 09:49:07 -0600[diff] [blame]2097 FROM 01 31 0 0T 0O 2 2T 2O 3 3T 3O 4A 4O 6A 6O
John Bowler63d059a2011-02-12 09:03:44 -0600[diff] [blame]2098 TO
2099 01 - [G] - - - - - - - - - - - - -
2100 31 [Q] Q [Q] [Q] [Q] Q Q Q Q Q Q [Q] [Q] Q Q
2101 0 1 G + . . G G G G G G B B GB GB
2102 0T lt Gt t + . Gt G G Gt G G Bt Bt GBt GBt
2103 0O lt Gt t . + Gt Gt G Gt Gt G Bt Bt GBt GBt
2104 2 C P C C C + . . C - - CB CB B B
2105 2T Ct - Ct C C t + t - - - CBt CBt Bt Bt
2106 2O Ct - Ct C C t t + - - - CBt CBt Bt Bt
2107 3 [Q] p [Q] [Q] [Q] Q Q Q + . . [Q] [Q] Q Q
2108 3T [Qt] p [Qt][Q] [Q] Qt Qt Qt t + t [Qt][Qt] Qt Qt
2109 3O [Qt] p [Qt][Q] [Q] Qt Qt Qt t t + [Qt][Qt] Qt Qt
2110 4A lA G A T T GA GT GT GA GT GT + BA G GBA
2111 4O lA GBA A T T GA GT GT GA GT GT BA + GBA G
2112 6A CA PA CA C C A T tT PA P P C CBA + BA
2113 6O CA PBA CA C C A tT T PA P P CBA C BA +
2114
2115Within the matrix,
2116 "+" identifies entries where 'from' and 'to' are the same.
2117 "-" means the transformation is not supported.
2118 "." means nothing is necessary (a tRNS chunk can just be ignored).
2119 "t" means the transformation is obtained by png_set_tRNS.
2120 "A" means the transformation is obtained by png_set_add_alpha().
2121 "X" means the transformation is obtained by png_set_expand().
2122 "1" means the transformation is obtained by
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]2123 png_set_expand_gray_1_2_4_to_8() (and by png_set_expand()
2124 if there is no transparency in the original or the final
2125 format).
John Bowler63d059a2011-02-12 09:03:44 -0600[diff] [blame]2126 "C" means the transformation is obtained by png_set_gray_to_rgb().
Glenn Randers-Pehrsonc36074e2011-05-16 09:08:51 -0500[diff] [blame]2127 "G" means the transformation is obtained by png_set_rgb_to_gray().
John Bowler63d059a2011-02-12 09:03:44 -0600[diff] [blame]2128 "P" means the transformation is obtained by
2129 png_set_expand_palette_to_rgb().
2130 "p" means the transformation is obtained by png_set_packing().
2131 "Q" means the transformation is obtained by png_set_quantize().
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]2132 "T" means the transformation is obtained by
2133 png_set_tRNS_to_alpha().
2134 "B" means the transformation is obtained by
2135 png_set_background(), or png_strip_alpha().
John Bowler63d059a2011-02-12 09:03:44 -0600[diff] [blame]2136
2137When an entry has multiple transforms listed all are required to cause the
2138right overall transformation. When two transforms are separated by a comma
2139either will do the job. When transforms are enclosed in [] the transform should
2140do the job but this is currently unimplemented - a different format will result
2141if the suggested transformations are used.
2142
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2143In PNG files, the alpha channel in an image
2144is the level of opacity. If you need the alpha channel in an image to
2145be the level of transparency instead of opacity, you can invert the
2146alpha channel (or the tRNS chunk data) after it's read, so that 0 is
2147fully opaque and 255 (in 8-bit or paletted images) or 65535 (in 16-bit
2148images) is fully transparent, with
2149
2150 png_set_invert_alpha(png_ptr);
2151
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2152PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
2153they can, resulting in, for example, 8 pixels per byte for 1 bit
2154files. This code expands to 1 pixel per byte without changing the
2155values of the pixels:
2156
2157 if (bit_depth < 8)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2158 png_set_packing(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2159
2160PNG files have possible bit depths of 1, 2, 4, 8, and 16. All pixels
2161stored in a PNG image have been "scaled" or "shifted" up to the next
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]2162higher possible bit depth (e.g. from 5 bits/sample in the range [0,31]
2163to 8 bits/sample in the range [0, 255]). However, it is also possible
2164to convert the PNG pixel data back to the original bit depth of the
2165image. This call reduces the pixels back down to the original bit depth:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2166
Glenn Randers-Pehrson1ea0ff32001-08-07 22:25:59 -0500[diff] [blame]2167 png_color_8p sig_bit;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2168
2169 if (png_get_sBIT(png_ptr, info_ptr, &sig_bit))
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2170 png_set_shift(png_ptr, sig_bit);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2171
2172PNG files store 3-color pixels in red, green, blue order. This code
2173changes the storage of the pixels to blue, green, red:
2174
2175 if (color_type == PNG_COLOR_TYPE_RGB ||
2176 color_type == PNG_COLOR_TYPE_RGB_ALPHA)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2177 png_set_bgr(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2178
Glenn Randers-Pehrson1b8e5672001-08-25 06:46:06 -0500[diff] [blame]2179PNG files store RGB pixels packed into 3 or 6 bytes. This code expands them
2180into 4 or 8 bytes for windowing systems that need them in this format:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2181
Glenn Randers-Pehrson1b8e5672001-08-25 06:46:06 -0500[diff] [blame]2182 if (color_type == PNG_COLOR_TYPE_RGB)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2183 png_set_filler(png_ptr, filler, PNG_FILLER_BEFORE);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2184
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]2185where "filler" is the 8 or 16-bit number to fill with, and the location is
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2186either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether
2187you want the filler before the RGB or after. This transformation
Glenn Randers-Pehrson1b8e5672001-08-25 06:46:06 -0500[diff] [blame]2188does not affect images that already have full alpha channels. To add an
2189opaque alpha channel, use filler=0xff or 0xffff and PNG_FILLER_AFTER which
2190will generate RGBA pixels.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2191
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]2192Note that png_set_filler() does not change the color type. If you want
2193to do that, you can add a true alpha channel with
2194
2195 if (color_type == PNG_COLOR_TYPE_RGB ||
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2196 color_type == PNG_COLOR_TYPE_GRAY)
2197 png_set_add_alpha(png_ptr, filler, PNG_FILLER_AFTER);
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]2198
2199where "filler" contains the alpha value to assign to each pixel.
Glenn Randers-Pehrson16e11662004-11-01 14:13:40 -0600[diff] [blame]2200This function was added in libpng-1.2.7.
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]2201
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2202If you are reading an image with an alpha channel, and you need the
2203data as ARGB instead of the normal PNG format RGBA:
2204
2205 if (color_type == PNG_COLOR_TYPE_RGB_ALPHA)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2206 png_set_swap_alpha(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2207
2208For some uses, you may want a grayscale image to be represented as
2209RGB. This code will do that conversion:
2210
2211 if (color_type == PNG_COLOR_TYPE_GRAY ||
2212 color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2213 png_set_gray_to_rgb(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2214
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2215Conversely, you can convert an RGB or RGBA image to grayscale or grayscale
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2216with alpha.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2217
2218 if (color_type == PNG_COLOR_TYPE_RGB ||
2219 color_type == PNG_COLOR_TYPE_RGB_ALPHA)
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]2220 png_set_rgb_to_gray(png_ptr, error_action,
2221 double red_weight, double green_weight);
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2222
2223 error_action = 1: silently do the conversion
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2224
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2225 error_action = 2: issue a warning if the original
2226 image has any pixel where
2227 red != green or red != blue
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2228
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2229 error_action = 3: issue an error and abort the
2230 conversion if the original
2231 image has any pixel where
2232 red != green or red != blue
2233
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2234 red_weight: weight of red component
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2235
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2236 green_weight: weight of green component
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2237 If either weight is negative, default
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2238 weights are used.
2239
2240In the corresponding fixed point API the red_weight and green_weight values are
2241simply scaled by 100,000:
2242
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]2243 png_set_rgb_to_gray(png_ptr, error_action,
2244 png_fixed_point red_weight,
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2245 png_fixed_point green_weight);
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2246
2247If you have set error_action = 1 or 2, you can
2248later check whether the image really was gray, after processing
2249the image rows, with the png_get_rgb_to_gray_status(png_ptr) function.
2250It will return a png_byte that is zero if the image was gray or
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]22511 if there were any non-gray pixels. Background and sBIT data
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2252will be silently converted to grayscale, using the green channel
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2253data for sBIT, regardless of the error_action setting.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2254
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]2255The default values come from the PNG file cHRM chunk if present; otherwise, the
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2256defaults correspond to the ITU-R recommendation 709, and also the sRGB color
2257space, as recommended in the Charles Poynton's Colour FAQ,
2258<http://www.poynton.com/>, in section 9:
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2259
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2260 <http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC9>
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2261
Glenn Randers-Pehrson6c988972011-07-29 12:31:16 -0500[diff] [blame]2262 Y = 0.2126 * R + 0.7152 * G + 0.0722 * B
2263
2264Previous versions of this document, 1998 through 2002, recommended a slightly
2265different formula:
2266
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2267 Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
2268
Glenn Randers-Pehrson6c988972011-07-29 12:31:16 -0500[diff] [blame]2269Libpng uses an integer approximation:
2270
2271 Y = (6968 * R + 23434 * G + 2366 * B)/32768
2272
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2273The calculation is done in a linear colorspace, if the image gamma
Glenn Randers-Pehrson9962b842011-01-24 00:12:14 -0600[diff] [blame]2274can be determined.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2275
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]2276The png_set_background() function has been described already; it tells libpng to
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2277composite images with alpha or simple transparency against the supplied
2278background color. For compatibility with versions of libpng earlier than
Glenn Randers-Pehrson733b1312011-06-15 13:21:01 -0500[diff] [blame]2279libpng-1.5.4 it is recommended that you call the function after reading the file
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2280header, even if you don't want to use the color in a bKGD chunk, if one exists.
2281
2282If the PNG file contains a bKGD chunk (PNG_INFO_bKGD valid),
2283you may use this color, or supply another color more suitable for
2284the current display (e.g., the background color from a web page). You
2285need to tell libpng how the color is represented, both the format of the
Glenn Randers-Pehrsonab389792011-07-09 19:35:22 -0500[diff] [blame]2286component values in the color (the number of bits) and the gamma encoding of the
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2287color. The function takes two arguments, background_gamma_mode and need_expand
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]2288to convey this information; however, only two combinations are likely to be
Glenn Randers-Pehrsonab389792011-07-09 19:35:22 -0500[diff] [blame]2289useful:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2290
Glenn Randers-Pehrsoncb47e202011-07-10 06:55:14 -0500[diff] [blame]2291 png_color_16 my_background;
2292 png_color_16p image_background;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2293
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]2294 if (png_get_bKGD(png_ptr, info_ptr, &image_background))
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2295 png_set_background(png_ptr, image_background,
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2296 PNG_BACKGROUND_GAMMA_FILE, 1/*needs to be expanded*/, 1);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2297 else
Glenn Randers-Pehrsoncb47e202011-07-10 06:55:14 -0500[diff] [blame]2298 png_set_background(png_ptr, &my_background,
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2299 PNG_BACKGROUND_GAMMA_SCREEN, 0/*do not expand*/, 1);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2300
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2301The second call was described above - my_background is in the format of the
2302final, display, output produced by libpng. Because you now know the format of
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]2303the PNG it is possible to avoid the need to choose either 8-bit or 16-bit
2304output and to retain palette images (the palette colors will be modified
2305appropriately and the tRNS chunk removed.) However, if you are doing this,
2306take great care not to ask for transformations without checking first that
2307they apply!
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2308
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2309In the first call the background color has the original bit depth and color type
2310of the PNG file. So, for palette images the color is supplied as a palette
2311index and for low bit greyscale images the color is a reduced bit value in
2312image_background->gray.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2313
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2314If you didn't call png_set_gamma() before reading the file header, for example
2315if you need your code to remain compatible with older versions of libpng prior
Glenn Randers-Pehrson733b1312011-06-15 13:21:01 -0500[diff] [blame]2316to libpng-1.5.4, this is the place to call it.
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]2317
John Bowlercb0b2962011-05-12 21:48:29 -0500[diff] [blame]2318Do not call it if you called png_set_alpha_mode(); doing so will damage the
2319settings put in place by png_set_alpha_mode(). (If png_set_alpha_mode() is
2320supported then you can certainly do png_set_gamma() before reading the PNG
2321header.)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2322
Glenn Randers-Pehrsonc7822512011-05-07 21:23:43 -0500[diff] [blame]2323This API unconditionally sets the screen and file gamma values, so it will
2324override the value in the PNG file unless it is called before the PNG file
2325reading starts. For this reason you must always call it with the PNG file
2326value when you call it in this position:
2327
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]2328 if (png_get_gAMA(png_ptr, info_ptr, &file_gamma))
2329 png_set_gamma(png_ptr, screen_gamma, file_gamma);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2330
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2331 else
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2332 png_set_gamma(png_ptr, screen_gamma, 0.45455);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2333
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]2334If you need to reduce an RGB file to a paletted file, or if a paletted
2335file has more entries then will fit on your screen, png_set_quantize()
Glenn Randers-Pehrson862cb202010-04-16 22:12:51 -0500[diff] [blame]2336will do that. Note that this is a simple match quantization that merely
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]2337finds the closest color available. This should work fairly well with
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2338optimized palettes, but fairly badly with linear color cubes. If you
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]2339pass a palette that is larger than maximum_colors, the file will
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]2340reduce the number of colors in the palette so it will fit into
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]2341maximum_colors. If there is a histogram, libpng will use it to make
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]2342more intelligent choices when reducing the palette. If there is no
2343histogram, it may not do as good a job.
2344
2345 if (color_type & PNG_COLOR_MASK_COLOR)
2346 {
2347 if (png_get_valid(png_ptr, info_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2348 PNG_INFO_PLTE))
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]2349 {
2350 png_uint_16p histogram = NULL;
2351
2352 png_get_hIST(png_ptr, info_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2353 &histogram);
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]2354 png_set_quantize(png_ptr, palette, num_palette,
2355 max_screen_colors, histogram, 1);
2356 }
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2357
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]2358 else
2359 {
2360 png_color std_color_cube[MAX_SCREEN_COLORS] =
2361 { ... colors ... };
2362
2363 png_set_quantize(png_ptr, std_color_cube,
2364 MAX_SCREEN_COLORS, MAX_SCREEN_COLORS,
2365 NULL,0);
2366 }
2367 }
2368
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2369PNG files describe monochrome as black being zero and white being one.
2370The following code will reverse this (make black be one and white be
2371zero):
2372
Glenn Randers-Pehrson1ea0ff32001-08-07 22:25:59 -0500[diff] [blame]2373 if (bit_depth == 1 && color_type == PNG_COLOR_TYPE_GRAY)
2374 png_set_invert_mono(png_ptr);
2375
2376This function can also be used to invert grayscale and gray-alpha images:
2377
2378 if (color_type == PNG_COLOR_TYPE_GRAY ||
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2379 color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2380 png_set_invert_mono(png_ptr);
2381
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]2382PNG files store 16-bit pixels in network byte order (big-endian,
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2383ie. most significant bits first). This code changes the storage to the
2384other way (little-endian, i.e. least significant bits first, the
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2385way PCs store them):
2386
2387 if (bit_depth == 16)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2388 png_set_swap(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2389
2390If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you
2391need to change the order the pixels are packed into bytes, you can use:
2392
2393 if (bit_depth < 8)
2394 png_set_packswap(png_ptr);
2395
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2396Finally, you can write your own transformation function if none of
2397the existing ones meets your needs. This is done by setting a callback
2398with
2399
2400 png_set_read_user_transform_fn(png_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2401 read_transform_fn);
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2402
2403You must supply the function
2404
Glenn Randers-Pehrson93215672011-02-13 19:42:19 -0600[diff] [blame]2405 void read_transform_fn(png_structp png_ptr, png_row_infop
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2406 row_info, png_bytep data)
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2407
2408See pngtest.c for a working example. Your function will be called
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]2409after all of the other transformations have been processed. Take care with
2410interlaced images if you do the interlace yourself - the width of the row is the
2411width in 'row_info', not the overall image width.
2412
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]2413If supported, libpng provides two information routines that you can use to find
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]2414where you are in processing the image:
2415
2416 png_get_current_pass_number(png_structp png_ptr);
2417 png_get_current_row_number(png_structp png_ptr);
2418
2419Don't try using these outside a transform callback - firstly they are only
2420supported if user transforms are supported, secondly they may well return
2421unexpected results unless the row is actually being processed at the moment they
2422are called.
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2423
John Bowlercd113452011-02-16 06:15:13 -0600[diff] [blame]2424With interlaced
2425images the value returned is the row in the input sub-image image. Use
2426PNG_ROW_FROM_PASS_ROW(row, pass) and PNG_COL_FROM_PASS_COL(col, pass) to
2427find the output pixel (x,y) given an interlaced sub-image pixel (row,col,pass).
2428
2429The discussion of interlace handling above contains more information on how to
2430use these values.
2431
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2432You can also set up a pointer to a user structure for use by your
2433callback function, and you can inform libpng that your transform
2434function will change the number of channels or bit depth with the
2435function
2436
2437 png_set_user_transform_info(png_ptr, user_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2438 user_depth, user_channels);
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2439
2440The user's application, not libpng, is responsible for allocating and
2441freeing any memory required for the user structure.
2442
2443You can retrieve the pointer via the function
2444png_get_user_transform_ptr(). For example:
2445
2446 voidp read_user_transform_ptr =
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2447 png_get_user_transform_ptr(png_ptr);
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2448
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2449The last thing to handle is interlacing; this is covered in detail below,
2450but you must call the function here if you want libpng to handle expansion
2451of the interlaced image.
2452
2453 number_of_passes = png_set_interlace_handling(png_ptr);
2454
2455After setting the transformations, libpng can update your png_info
2456structure to reflect any transformations you've requested with this
Glenn Randers-Pehrson968c2312011-09-26 16:35:22 -0500[diff] [blame]2457call.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2458
2459 png_read_update_info(png_ptr, info_ptr);
2460
Glenn Randers-Pehrson968c2312011-09-26 16:35:22 -0500[diff] [blame]2461This is most useful to update the info structure's rowbytes
2462field so you can use it to allocate your image memory. This function
2463will also update your palette with the correct screen_gamma and
2464background if these have been given with the calls above. You may
2465only call png_read_update_info() once with a particular info_ptr.
2466
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2467After you call png_read_update_info(), you can allocate any
2468memory you need to hold the image. The row data is simply
2469raw byte data for all forms of images. As the actual allocation
2470varies among applications, no example will be given. If you
2471are allocating one large chunk, you will need to build an
2472array of pointers to each row, as it will be needed for some
2473of the functions below.
2474
Glenn Randers-Pehrson968c2312011-09-26 16:35:22 -0500[diff] [blame]2475Remember: Before you call png_read_update_info(), the png_get_*()
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]2476functions return the values corresponding to the original PNG image.
2477After you call png_read_update_info the values refer to the image
2478that libpng will output. Consequently you must call all the png_set_
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2479functions before you call png_read_update_info(). This is particularly
2480important for png_set_interlace_handling() - if you are going to call
2481png_read_update_info() you must call png_set_interlace_handling() before
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]2482it unless you want to receive interlaced output.
2483
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2484.SS Reading image data
2485
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2486After you've allocated memory, you can read the image data.
2487The simplest way to do this is in one function call. If you are
2488allocating enough memory to hold the whole image, you can just
2489call png_read_image() and libpng will read in all the image data
2490and put it in the memory area supplied. You will need to pass in
2491an array of pointers to each row.
2492
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]2493This function automatically handles interlacing, so you don't
2494need to call png_set_interlace_handling() (unless you call
2495png_read_update_info()) or call this function multiple times, or any
2496of that other stuff necessary with png_read_rows().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2497
2498 png_read_image(png_ptr, row_pointers);
2499
2500where row_pointers is:
2501
2502 png_bytep row_pointers[height];
2503
2504You can point to void or char or whatever you use for pixels.
2505
2506If you don't want to read in the whole image at once, you can
2507use png_read_rows() instead. If there is no interlacing (check
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2508interlace_type == PNG_INTERLACE_NONE), this is simple:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2509
2510 png_read_rows(png_ptr, row_pointers, NULL,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2511 number_of_rows);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2512
2513where row_pointers is the same as in the png_read_image() call.
2514
2515If you are doing this just one row at a time, you can do this with
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2516a single row_pointer instead of an array of row_pointers:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2517
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2518 png_bytep row_pointer = row;
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2519 png_read_row(png_ptr, row_pointer, NULL);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2520
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2521If the file is interlaced (interlace_type != 0 in the IHDR chunk), things
2522get somewhat harder. The only current (PNG Specification version 1.2)
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2523interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7);
2524a somewhat complicated 2D interlace scheme, known as Adam7, that
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2525breaks down an image into seven smaller images of varying size, based
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2526on an 8x8 grid. This number is defined (from libpng 1.5) as
2527PNG_INTERLACE_ADAM7_PASSES in png.h
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2528
2529libpng can fill out those images or it can give them to you "as is".
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2530It is almost always better to have libpng handle the interlacing for you.
2531If you want the images filled out, there are two ways to do that. The one
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2532mentioned in the PNG specification is to expand each pixel to cover
2533those pixels that have not been read yet (the "rectangle" method).
2534This results in a blocky image for the first pass, which gradually
2535smooths out as more pixels are read. The other method is the "sparkle"
2536method, where pixels are drawn only in their final locations, with the
2537rest of the image remaining whatever colors they were initialized to
2538before the start of the read. The first method usually looks better,
2539but tends to be slower, as there are more pixels to put in the rows.
2540
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2541If, as is likely, you want libpng to expand the images, call this before
2542calling png_start_read_image() or png_read_update_info():
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2543
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2544 if (interlace_type == PNG_INTERLACE_ADAM7)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2545 number_of_passes
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2546 = png_set_interlace_handling(png_ptr);
2547
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2548This will return the number of passes needed. Currently, this is seven,
2549but may change if another interlace type is added. This function can be
2550called even if the file is not interlaced, where it will return one pass.
2551You then need to read the whole image 'number_of_passes' times. Each time
2552will distribute the pixels from the current pass to the correct place in
2553the output image, so you need to supply the same rows to png_read_rows in
2554each pass.
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]2555
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2556If you are not going to display the image after each pass, but are
2557going to wait until the entire image is read in, use the sparkle
2558effect. This effect is faster and the end result of either method
2559is exactly the same. If you are planning on displaying the image
2560after each pass, the "rectangle" effect is generally considered the
2561better looking one.
2562
2563If you only want the "sparkle" effect, just call png_read_rows() as
2564normal, with the third parameter NULL. Make sure you make pass over
2565the image number_of_passes times, and you don't change the data in the
2566rows between calls. You can change the locations of the data, just
2567not the data. Each pass only writes the pixels appropriate for that
2568pass, and assumes the data from previous passes is still valid.
2569
2570 png_read_rows(png_ptr, row_pointers, NULL,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2571 number_of_rows);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2572
2573If you only want the first effect (the rectangles), do the same as
2574before except pass the row buffer in the third parameter, and leave
2575the second parameter NULL.
2576
2577 png_read_rows(png_ptr, NULL, row_pointers,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2578 number_of_rows);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2579
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2580If you don't want libpng to handle the interlacing details, just call
2581png_read_rows() PNG_INTERLACE_ADAM7_PASSES times to read in all the images.
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]2582Each of the images is a valid image by itself; however, you will almost
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2583certainly need to distribute the pixels from each sub-image to the
2584correct place. This is where everything gets very tricky.
2585
2586If you want to retrieve the separate images you must pass the correct
2587number of rows to each successive call of png_read_rows(). The calculation
2588gets pretty complicated for small images, where some sub-images may
2589not even exist because either their width or height ends up zero.
2590libpng provides two macros to help you in 1.5 and later versions:
2591
2592 png_uint_32 width = PNG_PASS_COLS(image_width, pass_number);
2593 png_uint_32 height = PNG_PASS_ROWS(image_height, pass_number);
2594
2595Respectively these tell you the width and height of the sub-image
2596corresponding to the numbered pass. 'pass' is in in the range 0 to 6 -
2597this can be confusing because the specification refers to the same passes
2598as 1 to 7! Be careful, you must check both the width and height before
2599calling png_read_rows() and not call it for that pass if either is zero.
2600
2601You can, of course, read each sub-image row by row. If you want to
2602produce optimal code to make a pixel-by-pixel transformation of an
2603interlaced image this is the best approach; read each row of each pass,
2604transform it, and write it out to a new interlaced image.
2605
2606If you want to de-interlace the image yourself libpng provides further
2607macros to help that tell you where to place the pixels in the output image.
2608Because the interlacing scheme is rectangular - sub-image pixels are always
2609arranged on a rectangular grid - all you need to know for each pass is the
2610starting column and row in the output image of the first pixel plus the
2611spacing between each pixel. As of libpng 1.5 there are four macros to
2612retrieve this information:
2613
2614 png_uint_32 x = PNG_PASS_START_COL(pass);
2615 png_uint_32 y = PNG_PASS_START_ROW(pass);
2616 png_uint_32 xStep = 1U << PNG_PASS_COL_SHIFT(pass);
2617 png_uint_32 yStep = 1U << PNG_PASS_ROW_SHIFT(pass);
2618
2619These allow you to write the obvious loop:
2620
2621 png_uint_32 input_y = 0;
2622 png_uint_32 output_y = PNG_PASS_START_ROW(pass);
2623
2624 while (output_y < output_image_height)
2625 {
2626 png_uint_32 input_x = 0;
2627 png_uint_32 output_x = PNG_PASS_START_COL(pass);
2628
2629 while (output_x < output_image_width)
2630 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2631 image[output_y][output_x] =
2632 subimage[pass][input_y][input_x++];
2633
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2634 output_x += xStep;
2635 }
2636
2637 ++input_y;
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2638 output_y += yStep;
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2639 }
2640
2641Notice that the steps between successive output rows and columns are
2642returned as shifts. This is possible because the pixels in the subimages
2643are always a power of 2 apart - 1, 2, 4 or 8 pixels - in the original
2644image. In practice you may need to directly calculate the output coordinate
2645given an input coordinate. libpng provides two further macros for this
2646purpose:
2647
2648 png_uint_32 output_x = PNG_COL_FROM_PASS_COL(input_x, pass);
2649 png_uint_32 output_y = PNG_ROW_FROM_PASS_ROW(input_y, pass);
2650
2651Finally a pair of macros are provided to tell you if a particular image
2652row or column appears in a given pass:
2653
2654 int col_in_pass = PNG_COL_IN_INTERLACE_PASS(output_x, pass);
2655 int row_in_pass = PNG_ROW_IN_INTERLACE_PASS(output_y, pass);
2656
2657Bear in mind that you will probably also need to check the width and height
2658of the pass in addition to the above to be sure the pass even exists!
2659
2660With any luck you are convinced by now that you don't want to do your own
2661interlace handling. In reality normally the only good reason for doing this
2662is if you are processing PNG files on a pixel-by-pixel basis and don't want
2663to load the whole file into memory when it is interlaced.
2664
2665libpng includes a test program, pngvalid, that illustrates reading and
2666writing of interlaced images. If you can't get interlacing to work in your
Glenn Randers-Pehrson95ba4172011-09-08 12:21:42 -0500[diff] [blame]2667code and don't want to leave it to libpng (the recommended approach), see
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2668how pngvalid.c does it.
2669
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2670.SS Finishing a sequential read
2671
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]2672After you are finished reading the image through the
2673low-level interface, you can finish reading the file. If you are
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2674interested in comments or time, which may be stored either before or
2675after the image data, you should pass the separate png_info struct if
2676you want to keep the comments from before and after the image
Glenn Randers-Pehrson20786be2011-04-20 22:20:40 -0500[diff] [blame]2677separate.
2678
2679 png_infop end_info = png_create_info_struct(png_ptr);
2680
2681 if (!end_info)
2682 {
2683 png_destroy_read_struct(&png_ptr, &info_ptr,
2684 (png_infopp)NULL);
2685 return (ERROR);
2686 }
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2687
2688 png_read_end(png_ptr, end_info);
2689
Glenn Randers-Pehrson20786be2011-04-20 22:20:40 -0500[diff] [blame]2690If you are not interested, you should still call png_read_end()
2691but you can pass NULL, avoiding the need to create an end_info structure.
2692
2693 png_read_end(png_ptr, (png_infop)NULL);
2694
Glenn Randers-Pehrson99778e12011-04-20 17:43:52 -0500[diff] [blame]2695If you don't call png_read_end(), then your file pointer will be
2696left pointing to the first chunk after the last IDAT, which is probably
2697not what you want if you expect to read something beyond the end of
2698the PNG datastream.
2699
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2700When you are done, you can free all memory allocated by libpng like this:
2701
2702 png_destroy_read_struct(&png_ptr, &info_ptr,
2703 &end_info);
2704
Glenn Randers-Pehrson20786be2011-04-20 22:20:40 -0500[diff] [blame]2705or, if you didn't create an end_info structure,
2706
2707 png_destroy_read_struct(&png_ptr, &info_ptr,
2708 (png_infopp)NULL);
2709
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2710It is also possible to individually free the info_ptr members that
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2711point to libpng-allocated storage with the following function:
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2712
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2713 png_free_data(png_ptr, info_ptr, mask, seq)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2714
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2715 mask - identifies data to be freed, a mask
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]2716 containing the bitwise OR of one or
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2717 more of
2718 PNG_FREE_PLTE, PNG_FREE_TRNS,
2719 PNG_FREE_HIST, PNG_FREE_ICCP,
2720 PNG_FREE_PCAL, PNG_FREE_ROWS,
2721 PNG_FREE_SCAL, PNG_FREE_SPLT,
2722 PNG_FREE_TEXT, PNG_FREE_UNKN,
2723 or simply PNG_FREE_ALL
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2724
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2725 seq - sequence number of item to be freed
Glenn Randers-Pehrson4dcbf242013-08-06 17:20:06 -0500[diff] [blame]2726 (\-1 for all items)
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2727
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2728This function may be safely called when the relevant storage has
Glenn Randers-Pehrson68ea2432000-04-01 21:10:05 -0600[diff] [blame]2729already been freed, or has not yet been allocated, or was allocated
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]2730by the user and not by libpng, and will in those cases do nothing.
2731The "seq" parameter is ignored if only one item of the selected data
Glenn Randers-Pehrson4dcbf242013-08-06 17:20:06 -0500[diff] [blame]2732type, such as PLTE, is allowed. If "seq" is not \-1, and multiple items
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]2733are allowed for the data type identified in the mask, such as text or
2734sPLT, only the n'th item in the structure is freed, where n is "seq".
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2735
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2736The default behavior is only to free data that was allocated internally
2737by libpng. This can be changed, so that libpng will not free the data,
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2738or so that it will free data that was allocated by the user with png_malloc()
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]2739or png_calloc() and passed in via a png_set_*() function, with
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2740
2741 png_data_freer(png_ptr, info_ptr, freer, mask)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2742
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2743 freer - one of
2744 PNG_DESTROY_WILL_FREE_DATA
2745 PNG_SET_WILL_FREE_DATA
2746 PNG_USER_WILL_FREE_DATA
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2747
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2748 mask - which data elements are affected
2749 same choices as in png_free_data()
2750
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2751This function only affects data that has already been allocated.
2752You can call this function after reading the PNG data but before calling
2753any png_set_*() functions, to control whether the user or the png_set_*()
2754function is responsible for freeing any existing data that might be present,
2755and again after the png_set_*() functions to control whether the user
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2756or png_destroy_*() is supposed to free the data. When the user assumes
2757responsibility for libpng-allocated data, the application must use
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2758png_free() to free it, and when the user transfers responsibility to libpng
2759for data that the user has allocated, the user must have used png_malloc()
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]2760or png_calloc() to allocate it.
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2761
2762If you allocated your row_pointers in a single block, as suggested above in
2763the description of the high level read interface, you must not transfer
2764responsibility for freeing it to the png_set_rows or png_read_destroy function,
2765because they would also try to free the individual row_pointers[i].
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2766
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2767If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword
2768separately, do not transfer responsibility for freeing text_ptr to libpng,
2769because when libpng fills a png_text structure it combines these members with
2770the key member, and png_free_data() will free only text_ptr.key. Similarly,
2771if you transfer responsibility for free'ing text_ptr from libpng to your
2772application, your application must not separately free those members.
2773
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2774The png_free_data() function will turn off the "valid" flag for anything
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]2775it frees. If you need to turn the flag off for a chunk that was freed by
2776your application instead of by libpng, you can use
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2777
2778 png_set_invalid(png_ptr, info_ptr, mask);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2779
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2780 mask - identifies the chunks to be made invalid,
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]2781 containing the bitwise OR of one or
Glenn Randers-Pehrsond56aca72000-11-23 11:51:42 -0600[diff] [blame]2782 more of
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2783 PNG_INFO_gAMA, PNG_INFO_sBIT,
2784 PNG_INFO_cHRM, PNG_INFO_PLTE,
2785 PNG_INFO_tRNS, PNG_INFO_bKGD,
2786 PNG_INFO_hIST, PNG_INFO_pHYs,
2787 PNG_INFO_oFFs, PNG_INFO_tIME,
2788 PNG_INFO_pCAL, PNG_INFO_sRGB,
2789 PNG_INFO_iCCP, PNG_INFO_sPLT,
2790 PNG_INFO_sCAL, PNG_INFO_IDAT
2791
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2792For a more compact example of reading a PNG image, see the file example.c.
2793
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2794.SS Reading PNG files progressively
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2795
Glenn Randers-Pehrsonb23afad2013-07-10 19:30:59 -0500[diff] [blame]2796The progressive reader is slightly different from the non-progressive
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2797reader. Instead of calling png_read_info(), png_read_rows(), and
2798png_read_end(), you make one call to png_process_data(), which calls
2799callbacks when it has the info, a row, or the end of the image. You
2800set up these callbacks with png_set_progressive_read_fn(). You don't
2801have to worry about the input/output functions of libpng, as you are
2802giving the library the data directly in png_process_data(). I will
2803assume that you have read the section on reading PNG files above,
2804so I will only highlight the differences (although I will show
2805all of the code).
2806
2807png_structp png_ptr;
2808png_infop info_ptr;
2809
2810 /* An example code fragment of how you would
2811 initialize the progressive reader in your
2812 application. */
2813 int
2814 initialize_png_reader()
2815 {
2816 png_ptr = png_create_read_struct
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]2817 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2818 user_error_fn, user_warning_fn);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2819
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2820 if (!png_ptr)
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2821 return (ERROR);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2822
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2823 info_ptr = png_create_info_struct(png_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2824
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2825 if (!info_ptr)
2826 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2827 png_destroy_read_struct(&png_ptr,
2828 (png_infopp)NULL, (png_infopp)NULL);
2829 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2830 }
2831
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2832 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2833 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2834 png_destroy_read_struct(&png_ptr, &info_ptr,
2835 (png_infopp)NULL);
2836 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2837 }
2838
2839 /* This one's new. You can provide functions
2840 to be called when the header info is valid,
2841 when each row is completed, and when the image
2842 is finished. If you aren't using all functions,
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2843 you can specify NULL parameters. Even when all
2844 three functions are NULL, you need to call
2845 png_set_progressive_read_fn(). You can use
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2846 any struct as the user_ptr (cast to a void pointer
2847 for the function call), and retrieve the pointer
2848 from inside the callbacks using the function
2849
2850 png_get_progressive_ptr(png_ptr);
2851
2852 which will return a void pointer, which you have
2853 to cast appropriately.
2854 */
2855 png_set_progressive_read_fn(png_ptr, (void *)user_ptr,
2856 info_callback, row_callback, end_callback);
2857
2858 return 0;
2859 }
2860
2861 /* A code fragment that you call as you receive blocks
2862 of data */
2863 int
2864 process_data(png_bytep buffer, png_uint_32 length)
2865 {
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2866 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2867 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2868 png_destroy_read_struct(&png_ptr, &info_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2869 (png_infopp)NULL);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2870 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2871 }
2872
2873 /* This one's new also. Simply give it a chunk
2874 of data from the file stream (in order, of
2875 course). On machines with segmented memory
2876 models machines, don't give it any more than
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2877 64K. The library seems to run fine with sizes
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2878 of 4K. Although you can give it much less if
2879 necessary (I assume you can give it chunks of
2880 1 byte, I haven't tried less then 256 bytes
2881 yet). When this function returns, you may
2882 want to display any rows that were generated
2883 in the row callback if you don't already do
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2884 so there.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2885 */
2886 png_process_data(png_ptr, info_ptr, buffer, length);
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]2887
2888 /* At this point you can call png_process_data_skip if
2889 you want to handle data the library will skip yourself;
2890 it simply returns the number of bytes to skip (and stops
2891 libpng skipping that number of bytes on the next
2892 png_process_data call).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2893 return 0;
2894 }
2895
2896 /* This function is called (as set by
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2897 png_set_progressive_read_fn() above) when enough data
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2898 has been supplied so all of the header has been
2899 read.
2900 */
2901 void
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2902 info_callback(png_structp png_ptr, png_infop info)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2903 {
2904 /* Do any setup here, including setting any of
2905 the transformations mentioned in the Reading
2906 PNG files section. For now, you _must_ call
2907 either png_start_read_image() or
2908 png_read_update_info() after all the
2909 transformations are set (even if you don't set
2910 any). You may start getting rows before
2911 png_process_data() returns, so this is your
2912 last chance to prepare for that.
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2913
2914 This is where you turn on interlace handling,
2915 assuming you don't want to do it yourself.
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]2916
2917 If you need to you can stop the processing of
2918 your original input data at this point by calling
2919 png_process_data_pause. This returns the number
2920 of unprocessed bytes from the last png_process_data
2921 call - it is up to you to ensure that the next call
2922 sees these bytes again. If you don't want to bother
2923 with this you can get libpng to cache the unread
2924 bytes by setting the 'save' parameter (see png.h) but
2925 then libpng will have to copy the data internally.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2926 */
2927 }
2928
2929 /* This function is called when each row of image
2930 data is complete */
2931 void
2932 row_callback(png_structp png_ptr, png_bytep new_row,
Glenn Randers-Pehrsone68f5a32001-05-14 09:20:53 -0500[diff] [blame]2933 png_uint_32 row_num, int pass)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2934 {
2935 /* If the image is interlaced, and you turned
2936 on the interlace handler, this function will
2937 be called for every row in every pass. Some
2938 of these rows will not be changed from the
2939 previous pass. When the row is not changed,
2940 the new_row variable will be NULL. The rows
2941 and passes are called in order, so you don't
2942 really need the row_num and pass, but I'm
2943 supplying them because it may make your life
2944 easier.
2945
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2946 If you did not turn on interlace handling then
2947 the callback is called for each row of each
2948 sub-image when the image is interlaced. In this
2949 case 'row_num' is the row in the sub-image, not
2950 the row in the output image as it is in all other
2951 cases.
2952
2953 For the non-NULL rows of interlaced images when
2954 you have switched on libpng interlace handling,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2955 you must call png_progressive_combine_row()
2956 passing in the row and the old row. You can
2957 call this function for NULL rows (it will just
2958 return) and for non-interlaced images (it just
2959 does the memcpy for you) if it will make the
2960 code easier. Thus, you can just do this for
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2961 all cases if you switch on interlace handling;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2962 */
2963
2964 png_progressive_combine_row(png_ptr, old_row,
2965 new_row);
2966
2967 /* where old_row is what was displayed for
Glenn Randers-Pehrson345bc271998-06-14 14:43:31 -0500[diff] [blame]2968 previously for the row. Note that the first
2969 pass (pass == 0, really) will completely cover
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2970 the old row, so the rows do not have to be
2971 initialized. After the first pass (and only
2972 for interlaced images), you will have to pass
2973 the current row, and the function will combine
2974 the old row and the new row.
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]2975
2976 You can also call png_process_data_pause in this
2977 callback - see above.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2978 */
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2979 }
2980
2981 void
2982 end_callback(png_structp png_ptr, png_infop info)
2983 {
2984 /* This function is called after the whole image
2985 has been read, including any chunks after the
2986 image (up to and including the IEND). You
2987 will usually have the same info chunk as you
2988 had in the header, although some data may have
2989 been added to the comments and time fields.
2990
2991 Most people won't do much here, perhaps setting
2992 a flag that marks the image as finished.
2993 */
2994 }
2995
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]2996
2997
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2998.SH IV. Writing
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2999
3000Much of this is very similar to reading. However, everything of
3001importance is repeated here, so you won't have to constantly look
3002back up in the reading section to understand writing.
3003
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3004.SS Setup
3005
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3006You will want to do the I/O initialization before you get into libpng,
3007so if it doesn't work, you don't have anything to undo. If you are not
3008using the standard I/O functions, you will need to replace them with
3009custom writing functions. See the discussion under Customizing libpng.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3010
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3011 FILE *fp = fopen(file_name, "wb");
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3012
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3013 if (!fp)
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]3014 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3015
3016Next, png_struct and png_info need to be allocated and initialized.
3017As these can be both relatively large, you may not want to store these
3018on the stack, unless you have stack space to spare. Of course, you
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3019will want to check if they return NULL. If you are also reading,
3020you won't want to name your read structure and your write structure
3021both "png_ptr"; you can call them anything you like, such as
3022"read_ptr" and "write_ptr". Look at pngtest.c, for example.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3023
3024 png_structp png_ptr = png_create_write_struct
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]3025 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3026 user_error_fn, user_warning_fn);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3027
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3028 if (!png_ptr)
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]3029 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3030
3031 png_infop info_ptr = png_create_info_struct(png_ptr);
3032 if (!info_ptr)
3033 {
3034 png_destroy_write_struct(&png_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3035 (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]3036 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3037 }
3038
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]3039If you want to use your own memory allocation routines,
3040define PNG_USER_MEM_SUPPORTED and use
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3041png_create_write_struct_2() instead of png_create_write_struct():
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]3042
3043 png_structp png_ptr = png_create_write_struct_2
3044 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
3045 user_error_fn, user_warning_fn, (png_voidp)
3046 user_mem_ptr, user_malloc_fn, user_free_fn);
3047
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3048After you have these structures, you will need to set up the
3049error handling. When libpng encounters an error, it expects to
3050longjmp() back to your routine. Therefore, you will need to call
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3051setjmp() and pass the png_jmpbuf(png_ptr). If you
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3052write the file from different routines, you will need to update
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3053the png_jmpbuf(png_ptr) every time you enter a new routine that will
3054call a png_*() function. See your documentation of setjmp/longjmp
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3055for your compiler for more information on setjmp/longjmp. See
3056the discussion on libpng error handling in the Customizing Libpng
3057section below for more information on the libpng error handling.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3058
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3059 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3060 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3061 png_destroy_write_struct(&png_ptr, &info_ptr);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]3062 fclose(fp);
3063 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3064 }
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3065 ...
3066 return;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3067
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3068If you would rather avoid the complexity of setjmp/longjmp issues,
Glenn Randers-Pehrson54ac9a92010-04-02 17:06:22 -0500[diff] [blame]3069you can compile libpng with PNG_NO_SETJMP, in which case
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3070errors will result in a call to PNG_ABORT() which defaults to abort().
3071
Glenn Randers-Pehrson54ac9a92010-04-02 17:06:22 -0500[diff] [blame]3072You can #define PNG_ABORT() to a function that does something
3073more useful than abort(), as long as your function does not
3074return.
3075
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]3076Checking for invalid palette index on write was added at libpng
30771.5.10. If a pixel contains an invalid (out-of-range) index libpng issues
3078a benign error. This is enabled by default because this condition is an
3079error according to the PNG specification, Clause 11.3.2, but the error can
3080be ignored in each png_ptr with
3081
3082 png_set_check_for_invalid_index(png_ptr, 0);
3083
3084If the error is ignored, or if png_benign_error() treats it as a warning,
3085any invalid pixels are written as-is by the encoder, resulting in an
3086invalid PNG datastream as output. In this case the application is
3087responsible for ensuring that the pixel indexes are in range when it writes
3088a PLTE chunk with fewer entries than the bit depth would allow.
3089
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3090Now you need to set up the output code. The default for libpng is to
3091use the C function fwrite(). If you use this, you will need to pass a
3092valid FILE * in the function png_init_io(). Be sure that the file is
3093opened in binary mode. Again, if you wish to handle writing data in
3094another way, see the discussion on libpng I/O handling in the Customizing
3095Libpng section below.
3096
3097 png_init_io(png_ptr, fp);
3098
Glenn Randers-Pehrsond60b8fa2006-04-20 21:31:14 -0500[diff] [blame]3099If you are embedding your PNG into a datastream such as MNG, and don't
3100want libpng to write the 8-byte signature, or if you have already
3101written the signature in your application, use
3102
3103 png_set_sig_bytes(png_ptr, 8);
3104
3105to inform libpng that it should not write a signature.
3106
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3107.SS Write callbacks
3108
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3109At this point, you can set up a callback function that will be
3110called after each row has been written, which you can use to control
3111a progress meter or the like. It's demonstrated in pngtest.c.
3112You must supply a function
3113
Glenn Randers-Pehrson81ce8892011-01-24 08:04:37 -0600[diff] [blame]3114 void write_row_callback(png_structp png_ptr, png_uint_32 row,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3115 int pass);
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3116 {
3117 /* put your code here */
3118 }
3119
3120(You can give it another name that you like instead of "write_row_callback")
3121
3122To inform libpng about your function, use
3123
3124 png_set_write_status_fn(png_ptr, write_row_callback);
3125
John Bowler59010e52011-02-16 06:16:31 -0600[diff] [blame]3126When this function is called the row has already been completely processed and
3127it has also been written out. The 'row' and 'pass' refer to the next row to be
3128handled. For the
3129non-interlaced case the row that was just handled is simply one less than the
3130passed in row number, and pass will always be 0. For the interlaced case the
3131same applies unless the row value is 0, in which case the row just handled was
3132the last one from one of the preceding passes. Because interlacing may skip a
Glenn Randers-Pehrson4dcbf242013-08-06 17:20:06 -0500[diff] [blame]3133pass you cannot be sure that the preceding pass is just 'pass\-1', if you really
John Bowler59010e52011-02-16 06:16:31 -0600[diff] [blame]3134need to know what the last pass is record (row,pass) from the callback and use
3135the last recorded value each time.
3136
3137As with the user transform you can find the output row using the
3138PNG_ROW_FROM_PASS_ROW macro.
3139
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3140You now have the option of modifying how the compression library will
3141run. The following functions are mainly for testing, but may be useful
3142in some cases, like if you need to write PNG files extremely fast and
3143are willing to give up some compression, or if you want to get the
3144maximum possible compression at the expense of slower writing. If you
3145have no special needs in this area, let the library do what it wants by
3146not calling this function at all, as it has been tuned to deliver a good
3147speed/compression ratio. The second parameter to png_set_filter() is
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]3148the filter method, for which the only valid values are 0 (as of the
3149July 1999 PNG specification, version 1.2) or 64 (if you are writing
3150a PNG datastream that is to be embedded in a MNG datastream). The third
3151parameter is a flag that indicates which filter type(s) are to be tested
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3152for each scanline. See the PNG specification for details on the specific
3153filter types.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3154
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3155
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3156 /* turn on or off filtering, and/or choose
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3157 specific filters. You can use either a single
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]3158 PNG_FILTER_VALUE_NAME or the bitwise OR of one
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3159 or more PNG_FILTER_NAME masks.
3160 */
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3161 png_set_filter(png_ptr, 0,
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3162 PNG_FILTER_NONE | PNG_FILTER_VALUE_NONE |
3163 PNG_FILTER_SUB | PNG_FILTER_VALUE_SUB |
3164 PNG_FILTER_UP | PNG_FILTER_VALUE_UP |
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]3165 PNG_FILTER_AVG | PNG_FILTER_VALUE_AVG |
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3166 PNG_FILTER_PAETH | PNG_FILTER_VALUE_PAETH|
3167 PNG_ALL_FILTERS);
3168
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]3169If an application wants to start and stop using particular filters during
3170compression, it should start out with all of the filters (to ensure that
3171the previous row of pixels will be stored in case it's needed later),
3172and then add and remove them after the start of compression.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3173
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]3174If you are writing a PNG datastream that is to be embedded in a MNG
3175datastream, the second parameter can be either 0 or 64.
3176
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]3177The png_set_compression_*() functions interface to the zlib compression
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3178library, and should mostly be ignored unless you really know what you are
3179doing. The only generally useful call is png_set_compression_level()
3180which changes how much time zlib spends on trying to compress the image
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3181data. See the Compression Library (zlib.h and algorithm.txt, distributed
3182with zlib) for details on the compression levels.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3183
Glenn Randers-Pehrson38734ee2011-03-03 06:23:31 -0600[diff] [blame]3184 #include zlib.h
3185
Glenn Randers-Pehrsona45f47c2011-04-01 15:31:26 -0500[diff] [blame]3186 /* Set the zlib compression level */
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3187 png_set_compression_level(png_ptr,
3188 Z_BEST_COMPRESSION);
3189
Glenn Randers-Pehrsona45f47c2011-04-01 15:31:26 -0500[diff] [blame]3190 /* Set other zlib parameters for compressing IDAT */
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3191 png_set_compression_mem_level(png_ptr, 8);
3192 png_set_compression_strategy(png_ptr,
3193 Z_DEFAULT_STRATEGY);
3194 png_set_compression_window_bits(png_ptr, 15);
3195 png_set_compression_method(png_ptr, 8);
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3196 png_set_compression_buffer_size(png_ptr, 8192)
3197
Glenn Randers-Pehrsona45f47c2011-04-01 15:31:26 -0500[diff] [blame]3198 /* Set zlib parameters for text compression
3199 * If you don't call these, the parameters
3200 * fall back on those defined for IDAT chunks
3201 */
Glenn Randers-Pehrson8eb88332011-04-01 00:16:50 -0500[diff] [blame]3202 png_set_text_compression_mem_level(png_ptr, 8);
3203 png_set_text_compression_strategy(png_ptr,
3204 Z_DEFAULT_STRATEGY);
3205 png_set_text_compression_window_bits(png_ptr, 15);
3206 png_set_text_compression_method(png_ptr, 8);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3207
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3208.SS Setting the contents of info for output
3209
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3210You now need to fill in the png_info structure with all the data you
3211wish to write before the actual image. Note that the only thing you
3212are allowed to write after the image is the text chunks and the time
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3213chunk (as of PNG Specification 1.2, anyway). See png_write_end() and
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3214the latest PNG specification for more information on that. If you
3215wish to write them before the image, fill them in now, and flag that
3216data as being valid. If you want to wait until after the data, don't
3217fill them until png_write_end(). For all the fields in png_info and
3218their data types, see png.h. For explanations of what the fields
3219contain, see the PNG specification.
3220
3221Some of the more important parts of the png_info are:
3222
3223 png_set_IHDR(png_ptr, info_ptr, width, height,
3224 bit_depth, color_type, interlace_type,
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]3225 compression_type, filter_method)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3226
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3227 width - holds the width of the image
3228 in pixels (up to 2^31).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3229
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3230 height - holds the height of the image
3231 in pixels (up to 2^31).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3232
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3233 bit_depth - holds the bit depth of one of the
3234 image channels.
3235 (valid values are 1, 2, 4, 8, 16
3236 and depend also on the
3237 color_type. See also significant
3238 bits (sBIT) below).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3239
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3240 color_type - describes which color/alpha
3241 channels are present.
3242 PNG_COLOR_TYPE_GRAY
3243 (bit depths 1, 2, 4, 8, 16)
3244 PNG_COLOR_TYPE_GRAY_ALPHA
3245 (bit depths 8, 16)
3246 PNG_COLOR_TYPE_PALETTE
3247 (bit depths 1, 2, 4, 8)
3248 PNG_COLOR_TYPE_RGB
3249 (bit_depths 8, 16)
3250 PNG_COLOR_TYPE_RGB_ALPHA
3251 (bit_depths 8, 16)
3252
3253 PNG_COLOR_MASK_PALETTE
3254 PNG_COLOR_MASK_COLOR
3255 PNG_COLOR_MASK_ALPHA
3256
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3257 interlace_type - PNG_INTERLACE_NONE or
3258 PNG_INTERLACE_ADAM7
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3259
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3260 compression_type - (must be
3261 PNG_COMPRESSION_TYPE_DEFAULT)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3262
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]3263 filter_method - (must be PNG_FILTER_TYPE_DEFAULT
3264 or, if you are writing a PNG to
3265 be embedded in a MNG datastream,
3266 can also be
3267 PNG_INTRAPIXEL_DIFFERENCING)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3268
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]3269If you call png_set_IHDR(), the call must appear before any of the
Glenn Randers-Pehrsond60c8862009-06-15 21:56:14 -0500[diff] [blame]3270other png_set_*() functions, because they might require access to some of
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]3271the IHDR settings. The remaining png_set_*() functions can be called
3272in any order.
3273
Glenn Randers-Pehrsonb5444a12009-06-08 08:36:19 -0500[diff] [blame]3274If you wish, you can reset the compression_type, interlace_type, or
3275filter_method later by calling png_set_IHDR() again; if you do this, the
3276width, height, bit_depth, and color_type must be the same in each call.
Glenn Randers-Pehrson424c9852009-06-02 13:45:15 -0500[diff] [blame]3277
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3278 png_set_PLTE(png_ptr, info_ptr, palette,
3279 num_palette);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3280
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3281 palette - the palette for the file
3282 (array of png_color)
3283 num_palette - number of entries in the palette
3284
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]3285 png_set_gAMA(png_ptr, info_ptr, file_gamma);
3286 png_set_gAMA_fixed(png_ptr, info_ptr, int_file_gamma);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3287
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]3288 file_gamma - the gamma at which the image was
3289 created (PNG_INFO_gAMA)
3290
3291 int_file_gamma - 100,000 times the gamma at which
3292 the image was created
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3293
John Bowlerbbd17bd2011-08-25 17:48:18 -0500[diff] [blame]3294 png_set_cHRM(png_ptr, info_ptr, white_x, white_y, red_x, red_y,
3295 green_x, green_y, blue_x, blue_y)
3296 png_set_cHRM_XYZ(png_ptr, info_ptr, red_X, red_Y, red_Z, green_X,
3297 green_Y, green_Z, blue_X, blue_Y, blue_Z)
3298 png_set_cHRM_fixed(png_ptr, info_ptr, int_white_x, int_white_y,
3299 int_red_x, int_red_y, int_green_x, int_green_y,
3300 int_blue_x, int_blue_y)
3301 png_set_cHRM_XYZ_fixed(png_ptr, info_ptr, int_red_X, int_red_Y,
3302 int_red_Z, int_green_X, int_green_Y, int_green_Z,
3303 int_blue_X, int_blue_Y, int_blue_Z)
3304
3305 {white,red,green,blue}_{x,y}
3306 A color space encoding specified using the chromaticities
3307 of the end points and the white point.
3308
3309 {red,green,blue}_{X,Y,Z}
3310 A color space encoding specified using the encoding end
3311 points - the CIE tristimulus specification of the intended
3312 color of the red, green and blue channels in the PNG RGB
3313 data. The white point is simply the sum of the three end
3314 points.
3315
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3316 png_set_sRGB(png_ptr, info_ptr, srgb_intent);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3317
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3318 srgb_intent - the rendering intent
3319 (PNG_INFO_sRGB) The presence of
3320 the sRGB chunk means that the pixel
3321 data is in the sRGB color space.
3322 This chunk also implies specific
3323 values of gAMA and cHRM. Rendering
3324 intent is the CSS-1 property that
3325 has been defined by the International
3326 Color Consortium
3327 (http://www.color.org).
3328 It can be one of
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]3329 PNG_sRGB_INTENT_SATURATION,
3330 PNG_sRGB_INTENT_PERCEPTUAL,
3331 PNG_sRGB_INTENT_ABSOLUTE, or
3332 PNG_sRGB_INTENT_RELATIVE.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3333
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3334
3335 png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr,
3336 srgb_intent);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3337
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3338 srgb_intent - the rendering intent
3339 (PNG_INFO_sRGB) The presence of the
3340 sRGB chunk means that the pixel
3341 data is in the sRGB color space.
3342 This function also causes gAMA and
3343 cHRM chunks with the specific values
3344 that are consistent with sRGB to be
3345 written.
3346
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3347 png_set_iCCP(png_ptr, info_ptr, name, compression_type,
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]3348 profile, proflen);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3349
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]3350 name - The profile name.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3351
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]3352 compression_type - The compression type; always
3353 PNG_COMPRESSION_TYPE_BASE for PNG 1.0.
3354 You may give NULL to this argument to
3355 ignore it.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3356
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]3357 profile - International Color Consortium color
3358 profile data. May contain NULs.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3359
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]3360 proflen - length of profile data in bytes.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3361
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3362 png_set_sBIT(png_ptr, info_ptr, sig_bit);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3363
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3364 sig_bit - the number of significant bits for
3365 (PNG_INFO_sBIT) each of the gray, red,
3366 green, and blue channels, whichever are
3367 appropriate for the given color type
3368 (png_color_16)
3369
Glenn Randers-Pehrson866b62a2009-08-08 16:33:14 -0500[diff] [blame]3370 png_set_tRNS(png_ptr, info_ptr, trans_alpha,
3371 num_trans, trans_color);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3372
Glenn Randers-Pehrson866b62a2009-08-08 16:33:14 -0500[diff] [blame]3373 trans_alpha - array of alpha (transparency)
3374 entries for palette (PNG_INFO_tRNS)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3375
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]3376 num_trans - number of transparent entries
3377 (PNG_INFO_tRNS)
3378
Glenn Randers-Pehrsonb5444a12009-06-08 08:36:19 -0500[diff] [blame]3379 trans_color - graylevel or color sample values
3380 (in order red, green, blue) of the
3381 single transparent color for
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]3382 non-paletted images (PNG_INFO_tRNS)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3383
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3384 png_set_hIST(png_ptr, info_ptr, hist);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3385
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3386 hist - histogram of palette (array of
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]3387 png_uint_16) (PNG_INFO_hIST)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3388
3389 png_set_tIME(png_ptr, info_ptr, mod_time);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3390
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3391 mod_time - time image was last modified
3392 (PNG_VALID_tIME)
3393
3394 png_set_bKGD(png_ptr, info_ptr, background);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3395
Glenn Randers-Pehrsonab389792011-07-09 19:35:22 -0500[diff] [blame]3396 background - background color (of type
3397 png_color_16p) (PNG_VALID_bKGD)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3398
3399 png_set_text(png_ptr, info_ptr, text_ptr, num_text);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3400
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3401 text_ptr - array of png_text holding image
3402 comments
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3403
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3404 text_ptr[i].compression - type of compression used
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3405 on "text" PNG_TEXT_COMPRESSION_NONE
3406 PNG_TEXT_COMPRESSION_zTXt
3407 PNG_ITXT_COMPRESSION_NONE
3408 PNG_ITXT_COMPRESSION_zTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3409 text_ptr[i].key - keyword for comment. Must contain
3410 1-79 characters.
3411 text_ptr[i].text - text comments for current
3412 keyword. Can be NULL or empty.
3413 text_ptr[i].text_length - length of text string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3414 after decompression, 0 for iTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3415 text_ptr[i].itxt_length - length of itxt string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3416 after decompression, 0 for tEXt/zTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3417 text_ptr[i].lang - language of comment (NULL or
3418 empty for unknown).
3419 text_ptr[i].translated_keyword - keyword in UTF-8 (NULL
3420 or empty for unknown).
Glenn Randers-Pehrson680da022011-11-21 17:05:41 -0600[diff] [blame]3421
Glenn Randers-Pehrson8f5846f2009-10-31 21:31:08 -0500[diff] [blame]3422 Note that the itxt_length, lang, and lang_key
Glenn Randers-Pehrson680da022011-11-21 17:05:41 -0600[diff] [blame]3423 members of the text_ptr structure only exist when the
3424 library is built with iTXt chunk support. Prior to
3425 libpng-1.4.0 the library was built by default without
3426 iTXt support. Also note that when iTXt is supported,
3427 they contain NULL pointers when the "compression"
3428 field contains PNG_TEXT_COMPRESSION_NONE or
3429 PNG_TEXT_COMPRESSION_zTXt.
Glenn Randers-Pehrson8f5846f2009-10-31 21:31:08 -0500[diff] [blame]3430
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3431 num_text - number of comments
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3432
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3433 png_set_sPLT(png_ptr, info_ptr, &palette_ptr,
3434 num_spalettes);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3435
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3436 palette_ptr - array of png_sPLT_struct structures
3437 to be added to the list of palettes
3438 in the info structure.
3439 num_spalettes - number of palette structures to be
3440 added.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3441
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3442 png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y,
3443 unit_type);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3444
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3445 offset_x - positive offset from the left
3446 edge of the screen
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3447
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3448 offset_y - positive offset from the top
3449 edge of the screen
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3450
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3451 unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
3452
3453 png_set_pHYs(png_ptr, info_ptr, res_x, res_y,
3454 unit_type);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3455
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3456 res_x - pixels/unit physical resolution
3457 in x direction
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3458
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3459 res_y - pixels/unit physical resolution
3460 in y direction
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3461
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3462 unit_type - PNG_RESOLUTION_UNKNOWN,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3463 PNG_RESOLUTION_METER
3464
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3465 png_set_sCAL(png_ptr, info_ptr, unit, width, height)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3466
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3467 unit - physical scale units (an integer)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3468
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3469 width - width of a pixel in physical scale units
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3470
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3471 height - height of a pixel in physical scale units
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3472 (width and height are doubles)
3473
3474 png_set_sCAL_s(png_ptr, info_ptr, unit, width, height)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3475
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3476 unit - physical scale units (an integer)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3477
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3478 width - width of a pixel in physical scale units
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]3479 expressed as a string
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3480
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3481 height - height of a pixel in physical scale units
3482 (width and height are strings like "2.54")
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3483
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3484 png_set_unknown_chunks(png_ptr, info_ptr, &unknowns,
3485 num_unknowns)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3486
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3487 unknowns - array of png_unknown_chunk
3488 structures holding unknown chunks
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3489 unknowns[i].name - name of unknown chunk
3490 unknowns[i].data - data of unknown chunk
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3491 unknowns[i].size - size of unknown chunk's data
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3492 unknowns[i].location - position to write chunk in file
3493 0: do not write chunk
3494 PNG_HAVE_IHDR: before PLTE
3495 PNG_HAVE_PLTE: before IDAT
3496 PNG_AFTER_IDAT: after IDAT
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3497
3498The "location" member is set automatically according to
3499what part of the output file has already been written.
3500You can change its value after calling png_set_unknown_chunks()
3501as demonstrated in pngtest.c. Within each of the "locations",
3502the chunks are sequenced according to their position in the
3503structure (that is, the value of "i", which is the order in which
3504the chunk was either read from the input file or defined with
3505png_set_unknown_chunks).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3506
3507A quick word about text and num_text. text is an array of png_text
3508structures. num_text is the number of valid structures in the array.
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3509Each png_text structure holds a language code, a keyword, a text value,
3510and a compression type.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3511
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3512The compression types have the same valid numbers as the compression
3513types of the image data. Currently, the only valid number is zero.
3514However, you can store text either compressed or uncompressed, unlike
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3515images, which always have to be compressed. So if you don't want the
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3516text compressed, set the compression type to PNG_TEXT_COMPRESSION_NONE.
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3517Because tEXt and zTXt chunks don't have a language field, if you
3518specify PNG_TEXT_COMPRESSION_NONE or PNG_TEXT_COMPRESSION_zTXt
3519any language code or translated keyword will not be written out.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3520
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]3521Until text gets around a few hundred bytes, it is not worth compressing it.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3522After the text has been written out to the file, the compression type
3523is set to PNG_TEXT_COMPRESSION_NONE_WR or PNG_TEXT_COMPRESSION_zTXt_WR,
3524so that it isn't written out again at the end (in case you are calling
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3525png_write_end() with the same struct).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3526
3527The keywords that are given in the PNG Specification are:
3528
3529 Title Short (one line) title or
3530 caption for image
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3531
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3532 Author Name of image's creator
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3533
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3534 Description Description of image (possibly long)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3535
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3536 Copyright Copyright notice
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3537
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3538 Creation Time Time of original image creation
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3539 (usually RFC 1123 format, see below)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3540
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3541 Software Software used to create the image
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3542
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3543 Disclaimer Legal disclaimer
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3544
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3545 Warning Warning of nature of content
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3546
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3547 Source Device used to create the image
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3548
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3549 Comment Miscellaneous comment; conversion
3550 from other image format
3551
3552The keyword-text pairs work like this. Keywords should be short
3553simple descriptions of what the comment is about. Some typical
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3554keywords are found in the PNG specification, as is some recommendations
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3555on keywords. You can repeat keywords in a file. You can even write
3556some text before the image and some after. For example, you may want
3557to put a description of the image before the image, but leave the
3558disclaimer until after, so viewers working over modem connections
3559don't have to wait for the disclaimer to go over the modem before
3560they start seeing the image. Finally, keywords should be full
3561words, not abbreviations. Keywords and text are in the ISO 8859-1
3562(Latin-1) character set (a superset of regular ASCII) and can not
3563contain NUL characters, and should not contain control or other
3564unprintable characters. To make the comments widely readable, stick
3565with basic ASCII, and avoid machine specific character set extensions
3566like the IBM-PC character set. The keyword must be present, but
3567you can leave off the text string on non-compressed pairs.
3568Compressed pairs must have a text string, as only the text string
3569is compressed anyway, so the compression would be meaningless.
3570
3571PNG supports modification time via the png_time structure. Two
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3572conversion routines are provided, png_convert_from_time_t() for
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3573time_t and png_convert_from_struct_tm() for struct tm. The
3574time_t routine uses gmtime(). You don't have to use either of
3575these, but if you wish to fill in the png_time structure directly,
3576you should provide the time in universal time (GMT) if possible
3577instead of your local time. Note that the year number is the full
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3578year (e.g. 1998, rather than 98 - PNG is year 2000 compliant!), and
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3579that months start with 1.
3580
3581If you want to store the time of the original image creation, you should
3582use a plain tEXt chunk with the "Creation Time" keyword. This is
3583necessary because the "creation time" of a PNG image is somewhat vague,
3584depending on whether you mean the PNG file, the time the image was
3585created in a non-PNG format, a still photo from which the image was
3586scanned, or possibly the subject matter itself. In order to facilitate
3587machine-readable dates, it is recommended that the "Creation Time"
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3588tEXt chunk use RFC 1123 format dates (e.g. "22 May 1997 18:07:10 GMT"),
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3589although this isn't a requirement. Unlike the tIME chunk, the
3590"Creation Time" tEXt chunk is not expected to be automatically changed
3591by the software. To facilitate the use of RFC 1123 dates, a function
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]3592png_convert_to_rfc1123_buffer(png_ptr, buffer, png_timep) is provided to
3593convert from PNG time to an RFC 1123 format string. The caller must provide
3594a writeable buffer of at least 29 bytes.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3595
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3596.SS Writing unknown chunks
3597
Glenn Randers-Pehrson49f9c242013-04-27 18:03:03 -0500[diff] [blame]3598You can use the png_set_unknown_chunks function to queue up private chunks
3599for writing. You give it a chunk name, location, raw data, and a size. You
3600also must use png_set_keep_unknown_chunks() to ensure that libpng will
3601handle them. That's all there is to it. The chunks will be written by the
3602next following png_write_info_before_PLTE, png_write_info, or png_write_end
3603function, depending upon the specified location. Any chunks previously
3604read into the info structure's unknown-chunk list will also be written out
3605in a sequence that satisfies the PNG specification's ordering rules.
3606
3607Here is an example of writing two private chunks, prVt and miNE:
3608
3609 #ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
3610 /* Set unknown chunk data */
Glenn Randers-Pehrson61946e02013-04-28 20:48:37 -0500[diff] [blame]3611 png_unknown_chunk unk_chunk[2];
3612 strcpy((char *) unk_chunk[0].name, "prVt";
3613 unk_chunk[0].data = (unsigned char *) "PRIVATE DATA";
3614 unk_chunk[0].size = strlen(unk_chunk[0].data)+1;
3615 unk_chunk[0].location = PNG_HAVE_IHDR;
3616 strcpy((char *) unk_chunk[1].name, "miNE";
3617 unk_chunk[1].data = (unsigned char *) "MY CHUNK DATA";
3618 unk_chunk[1].size = strlen(unk_chunk[0].data)+1;
3619 unk_chunk[1].location = PNG_AFTER_IDAT;
3620 png_set_unknown_chunks(write_ptr, write_info_ptr,
3621 unk_chunk, 2);
3622 /* Needed because miNE is not safe-to-copy */
3623 png_set_keep_unknown_chunks(png, PNG_HANDLE_CHUNK_ALWAYS,
3624 (png_bytep) "miNE", 1);
3625 # if PNG_LIBPNG_VER < 10600
3626 /* Deal with unknown chunk location bug in 1.5.x and earlier */
3627 png_set_unknown_chunk_location(png, info, 0, PNG_HAVE_IHDR);
3628 png_set_unknown_chunk_location(png, info, 1, PNG_AFTER_IDAT);
3629 # endif
3630 # if PNG_LIBPNG_VER < 10500
3631 /* PNG_AFTER_IDAT writes two copies of the chunk prior to libpng-1.5.0,
3632 * one before IDAT and another after IDAT, so don't use it; only use
3633 * PNG_HAVE_IHDR location. This call resets the location previously
3634 * set by assignment and png_set_unknown_chunk_location() for chunk 1.
3635 */
3636 png_set_unknown_chunk_location(png, info, 1, PNG_HAVE_IHDR);
3637 # endif
Glenn Randers-Pehrson49f9c242013-04-27 18:03:03 -0500[diff] [blame]3638 #endif
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3639
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3640.SS The high-level write interface
3641
3642At this point there are two ways to proceed; through the high-level
3643write interface, or through a sequence of low-level write operations.
3644You can use the high-level interface if your image data is present
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3645in the info structure. All defined output
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]3646transformations are permitted, enabled by the following masks.
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3647
3648 PNG_TRANSFORM_IDENTITY No transformation
3649 PNG_TRANSFORM_PACKING Pack 1, 2 and 4-bit samples
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3650 PNG_TRANSFORM_PACKSWAP Change order of packed
3651 pixels to LSB first
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3652 PNG_TRANSFORM_INVERT_MONO Invert monochrome images
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3653 PNG_TRANSFORM_SHIFT Normalize pixels to the
3654 sBIT depth
3655 PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA
3656 to BGRA
3657 PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA
3658 to AG
3659 PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity
3660 to transparency
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3661 PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples
Glenn Randers-Pehrson1eb14e92008-12-10 07:14:45 -0600[diff] [blame]3662 PNG_TRANSFORM_STRIP_FILLER Strip out filler
3663 bytes (deprecated).
3664 PNG_TRANSFORM_STRIP_FILLER_BEFORE Strip out leading
3665 filler bytes
3666 PNG_TRANSFORM_STRIP_FILLER_AFTER Strip out trailing
3667 filler bytes
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3668
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3669If you have valid image data in the info structure (you can use
3670png_set_rows() to put image data in the info structure), simply do this:
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3671
3672 png_write_png(png_ptr, info_ptr, png_transforms, NULL)
3673
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]3674where png_transforms is an integer containing the bitwise OR of some set of
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3675transformation flags. This call is equivalent to png_write_info(),
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3676followed the set of transformations indicated by the transform mask,
3677then png_write_image(), and finally png_write_end().
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3678
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3679(The final parameter of this call is not yet used. Someday it might point
3680to transformation parameters required by some future output transform.)
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3681
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]3682You must use png_transforms and not call any png_set_transform() functions
3683when you use png_write_png().
3684
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3685.SS The low-level write interface
3686
3687If you are going the low-level route instead, you are now ready to
3688write all the file information up to the actual image data. You do
3689this with a call to png_write_info().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3690
3691 png_write_info(png_ptr, info_ptr);
3692
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3693Note that there is one transformation you may need to do before
3694png_write_info(). In PNG files, the alpha channel in an image is the
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3695level of opacity. If your data is supplied as a level of transparency,
3696you can invert the alpha channel before you write it, so that 0 is
3697fully transparent and 255 (in 8-bit or paletted images) or 65535
3698(in 16-bit images) is fully opaque, with
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3699
3700 png_set_invert_alpha(png_ptr);
3701
3702This must appear before png_write_info() instead of later with the
3703other transformations because in the case of paletted images the tRNS
3704chunk data has to be inverted before the tRNS chunk is written. If
3705your image is not a paletted image, the tRNS data (which in such cases
3706represents a single color to be rendered as transparent) won't need to
3707be changed, and you can safely do this transformation after your
3708png_write_info() call.
3709
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]3710If you need to write a private chunk that you want to appear before
3711the PLTE chunk when PLTE is present, you can write the PNG info in
3712two steps, and insert code to write your own chunk between them:
3713
3714 png_write_info_before_PLTE(png_ptr, info_ptr);
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3715 png_set_unknown_chunks(png_ptr, info_ptr, ...);
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]3716 png_write_info(png_ptr, info_ptr);
3717
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3718After you've written the file information, you can set up the library
3719to handle any special transformations of the image data. The various
3720ways to transform the data will be described in the order that they
3721should occur. This is important, as some of these change the color
3722type and/or bit depth of the data, and some others only work on
3723certain color types and bit depths. Even though each transformation
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3724checks to see if it has data that it can do something with, you should
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3725make sure to only enable a transformation if it will be valid for the
3726data. For example, don't swap red and blue on grayscale data.
3727
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]3728PNG files store RGB pixels packed into 3 or 6 bytes. This code tells
Glenn Randers-Pehrson68ea2432000-04-01 21:10:05 -0600[diff] [blame]3729the library to strip input data that has 4 or 8 bytes per pixel down
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3730to 3 or 6 bytes (or strip 2 or 4-byte grayscale+filler data to 1 or 2
3731bytes per pixel).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3732
3733 png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
3734
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3735where the 0 is unused, and the location is either PNG_FILLER_BEFORE or
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3736PNG_FILLER_AFTER, depending upon whether the filler byte in the pixel
3737is stored XRGB or RGBX.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3738
3739PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
3740they can, resulting in, for example, 8 pixels per byte for 1 bit files.
3741If the data is supplied at 1 pixel per byte, use this code, which will
3742correctly pack the pixels into a single byte:
3743
3744 png_set_packing(png_ptr);
3745
3746PNG files reduce possible bit depths to 1, 2, 4, 8, and 16. If your
3747data is of another bit depth, you can write an sBIT chunk into the
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3748file so that decoders can recover the original data if desired.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3749
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3750 /* Set the true bit depth of the image data */
3751 if (color_type & PNG_COLOR_MASK_COLOR)
3752 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3753 sig_bit.red = true_bit_depth;
3754 sig_bit.green = true_bit_depth;
3755 sig_bit.blue = true_bit_depth;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3756 }
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3757
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3758 else
3759 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3760 sig_bit.gray = true_bit_depth;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3761 }
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3762
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3763 if (color_type & PNG_COLOR_MASK_ALPHA)
3764 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3765 sig_bit.alpha = true_bit_depth;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3766 }
3767
3768 png_set_sBIT(png_ptr, info_ptr, &sig_bit);
3769
3770If the data is stored in the row buffer in a bit depth other than
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3771one supported by PNG (e.g. 3 bit data in the range 0-7 for a 4-bit PNG),
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3772this will scale the values to appear to be the correct bit depth as
3773is required by PNG.
3774
3775 png_set_shift(png_ptr, &sig_bit);
3776
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]3777PNG files store 16-bit pixels in network byte order (big-endian,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3778ie. most significant bits first). This code would be used if they are
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3779supplied the other way (little-endian, i.e. least significant bits
3780first, the way PCs store them):
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3781
3782 if (bit_depth > 8)
3783 png_set_swap(png_ptr);
3784
3785If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you
3786need to change the order the pixels are packed into bytes, you can use:
3787
3788 if (bit_depth < 8)
3789 png_set_packswap(png_ptr);
3790
3791PNG files store 3 color pixels in red, green, blue order. This code
3792would be used if they are supplied as blue, green, red:
3793
3794 png_set_bgr(png_ptr);
3795
3796PNG files describe monochrome as black being zero and white being
3797one. This code would be used if the pixels are supplied with this reversed
3798(black being one and white being zero):
3799
3800 png_set_invert_mono(png_ptr);
3801
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3802Finally, you can write your own transformation function if none of
3803the existing ones meets your needs. This is done by setting a callback
3804with
3805
3806 png_set_write_user_transform_fn(png_ptr,
3807 write_transform_fn);
3808
3809You must supply the function
3810
Glenn Randers-Pehrson93215672011-02-13 19:42:19 -0600[diff] [blame]3811 void write_transform_fn(png_structp png_ptr, png_row_infop
3812 row_info, png_bytep data)
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3813
3814See pngtest.c for a working example. Your function will be called
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]3815before any of the other transformations are processed. If supported
3816libpng also supplies an information routine that may be called from
3817your callback:
3818
3819 png_get_current_row_number(png_ptr);
John Bowlercd113452011-02-16 06:15:13 -0600[diff] [blame]3820 png_get_current_pass_number(png_ptr);
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]3821
John Bowlercd113452011-02-16 06:15:13 -0600[diff] [blame]3822This returns the current row passed to the transform. With interlaced
3823images the value returned is the row in the input sub-image image. Use
3824PNG_ROW_FROM_PASS_ROW(row, pass) and PNG_COL_FROM_PASS_COL(col, pass) to
3825find the output pixel (x,y) given an interlaced sub-image pixel (row,col,pass).
3826
3827The discussion of interlace handling above contains more information on how to
3828use these values.
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3829
3830You can also set up a pointer to a user structure for use by your
3831callback function.
3832
3833 png_set_user_transform_info(png_ptr, user_ptr, 0, 0);
3834
3835The user_channels and user_depth parameters of this function are ignored
3836when writing; you can set them to zero as shown.
3837
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3838You can retrieve the pointer via the function png_get_user_transform_ptr().
3839For example:
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3840
3841 voidp write_user_transform_ptr =
3842 png_get_user_transform_ptr(png_ptr);
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3843
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3844It is possible to have libpng flush any pending output, either manually,
3845or automatically after a certain number of lines have been written. To
3846flush the output stream a single time call:
3847
3848 png_write_flush(png_ptr);
3849
3850and to have libpng flush the output stream periodically after a certain
3851number of scanlines have been written, call:
3852
3853 png_set_flush(png_ptr, nrows);
3854
3855Note that the distance between rows is from the last time png_write_flush()
3856was called, or the first row of the image if it has never been called.
3857So if you write 50 lines, and then png_set_flush 25, it will flush the
3858output on the next scanline, and every 25 lines thereafter, unless
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3859png_write_flush() is called before 25 more lines have been written.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3860If nrows is too small (less than about 10 lines for a 640 pixel wide
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3861RGB image) the image compression may decrease noticeably (although this
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3862may be acceptable for real-time applications). Infrequent flushing will
3863only degrade the compression performance by a few percent over images
3864that do not use flushing.
3865
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3866.SS Writing the image data
3867
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3868That's it for the transformations. Now you can write the image data.
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3869The simplest way to do this is in one function call. If you have the
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3870whole image in memory, you can just call png_write_image() and libpng
3871will write the image. You will need to pass in an array of pointers to
3872each row. This function automatically handles interlacing, so you don't
3873need to call png_set_interlace_handling() or call this function multiple
3874times, or any of that other stuff necessary with png_write_rows().
3875
3876 png_write_image(png_ptr, row_pointers);
3877
3878where row_pointers is:
3879
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]3880 png_byte *row_pointers[height];
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3881
3882You can point to void or char or whatever you use for pixels.
3883
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]3884If you don't want to write the whole image at once, you can
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3885use png_write_rows() instead. If the file is not interlaced,
3886this is simple:
3887
3888 png_write_rows(png_ptr, row_pointers,
3889 number_of_rows);
3890
3891row_pointers is the same as in the png_write_image() call.
3892
3893If you are just writing one row at a time, you can do this with
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3894a single row_pointer instead of an array of row_pointers:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3895
3896 png_bytep row_pointer = row;
3897
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3898 png_write_row(png_ptr, row_pointer);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3899
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3900When the file is interlaced, things can get a good deal more complicated.
3901The only currently (as of the PNG Specification version 1.2, dated July
39021999) defined interlacing scheme for PNG files is the "Adam7" interlace
3903scheme, that breaks down an image into seven smaller images of varying
3904size. libpng will build these images for you, or you can do them
3905yourself. If you want to build them yourself, see the PNG specification
3906for details of which pixels to write when.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3907
3908If you don't want libpng to handle the interlacing details, just
3909use png_set_interlace_handling() and call png_write_rows() the
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]3910correct number of times to write all the sub-images
3911(png_set_interlace_handling() returns the number of sub-images.)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3912
3913If you want libpng to build the sub-images, call this before you start
3914writing any rows:
3915
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]3916 number_of_passes = png_set_interlace_handling(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3917
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3918This will return the number of passes needed. Currently, this is seven,
3919but may change if another interlace type is added.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3920
3921Then write the complete image number_of_passes times.
3922
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]3923 png_write_rows(png_ptr, row_pointers, number_of_rows);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3924
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]3925Think carefully before you write an interlaced image. Typically code that
3926reads such images reads all the image data into memory, uncompressed, before
3927doing any processing. Only code that can display an image on the fly can
3928take advantage of the interlacing and even then the image has to be exactly
3929the correct size for the output device, because scaling an image requires
3930adjacent pixels and these are not available until all the passes have been
3931read.
3932
3933If you do write an interlaced image you will hardly ever need to handle
3934the interlacing yourself. Call png_set_interlace_handling() and use the
3935approach described above.
3936
3937The only time it is conceivable that you will really need to write an
3938interlaced image pass-by-pass is when you have read one pass by pass and
3939made some pixel-by-pixel transformation to it, as described in the read
3940code above. In this case use the PNG_PASS_ROWS and PNG_PASS_COLS macros
3941to determine the size of each sub-image in turn and simply write the rows
3942you obtained from the read code.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3943
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3944.SS Finishing a sequential write
3945
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3946After you are finished writing the image, you should finish writing
3947the file. If you are interested in writing comments or time, you should
3948pass an appropriately filled png_info pointer. If you are not interested,
3949you can pass NULL.
3950
3951 png_write_end(png_ptr, info_ptr);
3952
3953When you are done, you can free all memory used by libpng like this:
3954
3955 png_destroy_write_struct(&png_ptr, &info_ptr);
3956
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3957It is also possible to individually free the info_ptr members that
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]3958point to libpng-allocated storage with the following function:
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3959
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3960 png_free_data(png_ptr, info_ptr, mask, seq)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3961
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3962 mask - identifies data to be freed, a mask
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]3963 containing the bitwise OR of one or
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3964 more of
3965 PNG_FREE_PLTE, PNG_FREE_TRNS,
3966 PNG_FREE_HIST, PNG_FREE_ICCP,
3967 PNG_FREE_PCAL, PNG_FREE_ROWS,
3968 PNG_FREE_SCAL, PNG_FREE_SPLT,
3969 PNG_FREE_TEXT, PNG_FREE_UNKN,
3970 or simply PNG_FREE_ALL
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3971
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3972 seq - sequence number of item to be freed
Glenn Randers-Pehrson4dcbf242013-08-06 17:20:06 -0500[diff] [blame]3973 (\-1 for all items)
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3974
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]3975This function may be safely called when the relevant storage has
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3976already been freed, or has not yet been allocated, or was allocated
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3977by the user and not by libpng, and will in those cases do nothing.
3978The "seq" parameter is ignored if only one item of the selected data
Glenn Randers-Pehrson4dcbf242013-08-06 17:20:06 -0500[diff] [blame]3979type, such as PLTE, is allowed. If "seq" is not \-1, and multiple items
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3980are allowed for the data type identified in the mask, such as text or
3981sPLT, only the n'th item in the structure is freed, where n is "seq".
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3982
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3983If you allocated data such as a palette that you passed in to libpng
3984with png_set_*, you must not free it until just before the call to
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]3985png_destroy_write_struct().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3986
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3987The default behavior is only to free data that was allocated internally
3988by libpng. This can be changed, so that libpng will not free the data,
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3989or so that it will free data that was allocated by the user with png_malloc()
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]3990or png_calloc() and passed in via a png_set_*() function, with
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3991
3992 png_data_freer(png_ptr, info_ptr, freer, mask)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3993
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3994 freer - one of
3995 PNG_DESTROY_WILL_FREE_DATA
3996 PNG_SET_WILL_FREE_DATA
3997 PNG_USER_WILL_FREE_DATA
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3998
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3999 mask - which data elements are affected
4000 same choices as in png_free_data()
4001
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]4002For example, to transfer responsibility for some data from a read structure
4003to a write structure, you could use
4004
4005 png_data_freer(read_ptr, read_info_ptr,
4006 PNG_USER_WILL_FREE_DATA,
4007 PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4008
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]4009 png_data_freer(write_ptr, write_info_ptr,
4010 PNG_DESTROY_WILL_FREE_DATA,
4011 PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST)
4012
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4013thereby briefly reassigning responsibility for freeing to the user but
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]4014immediately afterwards reassigning it once more to the write_destroy
4015function. Having done this, it would then be safe to destroy the read
4016structure and continue to use the PLTE, tRNS, and hIST data in the write
4017structure.
4018
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]4019This function only affects data that has already been allocated.
4020You can call this function before calling after the png_set_*() functions
4021to control whether the user or png_destroy_*() is supposed to free the data.
4022When the user assumes responsibility for libpng-allocated data, the
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]4023application must use
4024png_free() to free it, and when the user transfers responsibility to libpng
4025for data that the user has allocated, the user must have used png_malloc()
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4026or png_calloc() to allocate it.
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]4027
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]4028If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword
4029separately, do not transfer responsibility for freeing text_ptr to libpng,
4030because when libpng fills a png_text structure it combines these members with
4031the key member, and png_free_data() will free only text_ptr.key. Similarly,
4032if you transfer responsibility for free'ing text_ptr from libpng to your
4033application, your application must not separately free those members.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4034For a more compact example of writing a PNG image, see the file example.c.
4035
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4036.SH V. Simplified API
4037
4038The simplified API, which became available in libpng-1.6.0, hides the details
4039of both libpng and the PNG file format itself.
4040It allows PNG files to be read into a very limited number of
4041in-memory bitmap formats or to be written from the same formats. If these
Glenn Randers-Pehrson4dcbf242013-08-06 17:20:06 -0500[diff] [blame]4042formats do not accommodate your needs then you can, and should, use the more
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4043sophisticated APIs above - these support a wide variety of in-memory formats
4044and a wide variety of sophisticated transformations to those formats as well
4045as a wide variety of APIs to manipulate ancilliary information.
4046
4047To read a PNG file using the simplified API:
4048
4049 1) Declare a 'png_image' structure (see below) on the
4050 stack and memset() it to all zero.
4051
4052 2) Call the appropriate png_image_begin_read... function.
4053
4054 3) Set the png_image 'format' member to the required
4055 format and allocate a buffer for the image.
4056
4057 4) Call png_image_finish_read to read the image into
4058 your buffer.
4059
4060There are no restrictions on the format of the PNG input itself; all valid
4061color types, bit depths, and interlace methods are acceptable, and the
4062input image is transformed as necessary to the requested in-memory format
4063during the png_image_finish_read() step.
4064
4065To write a PNG file using the simplified API:
4066
4067 1) Declare a 'png_image' structure on the stack and memset()
4068 it to all zero.
4069
4070 2) Initialize the members of the structure that describe the
4071 image, setting the 'format' member to the format of the
4072 image in memory.
4073
4074 3) Call the appropriate png_image_write... function with a
4075 pointer to the image to write the PNG data.
4076
4077png_image is a structure that describes the in-memory format of an image
4078when it is being read or define the in-memory format of an image that you
4079need to write. The "png_image" structure contains the following members:
4080
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4081 png_uint_32 version Set to PNG_IMAGE_VERSION
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4082 png_uint_32 width Image width in pixels (columns)
4083 png_uint_32 height Image height in pixels (rows)
4084 png_uint_32 format Image format as defined below
4085 png_uint_32 flags A bit mask containing informational flags
4086 png_controlp opaque Initialize to NULL, free with png_image_free
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4087 png_uint_32 colormap_entries; Number of entries in the color-map
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4088 png_uint_32 warning_or_error;
4089 char message[64];
4090
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4091In the event of an error or warning the following field warning_or_error
4092field will be set to a non-zero value and the 'message' field will contain
4093a '\0' terminated string with the libpng error or warning message. If both
4094warnings and an error were encountered, only the error is recorded. If there
4095are multiple warnings, only the first one is recorded.
4096
4097The upper 30 bits of this value are reserved; the low two bits contain
4098a two bit code such that a value more than 1 indicates a failure in the API
4099just called:
4100
4101 0 - no warning or error
4102 1 - warning
4103 2 - error
4104 3 - error preceded by warning
4105
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4106The pixels (samples) of the image have one to four channels whose components
4107have original values in the range 0 to 1.0:
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4108
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4109 1: A single gray or luminance channel (G).
4110 2: A gray/luminance channel and an alpha channel (GA).
4111 3: Three red, green, blue color channels (RGB).
4112 4: Three color channels and an alpha channel (RGBA).
4113
4114The channels are encoded in one of two ways:
4115
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4116 a) As a small integer, value 0..255, contained in a single byte. For the
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4117alpha channel the original value is simply value/255. For the color or
4118luminance channels the value is encoded according to the sRGB specification
4119and matches the 8-bit format expected by typical display devices.
4120
4121The color/gray channels are not scaled (pre-multiplied) by the alpha
4122channel and are suitable for passing to color management software.
4123
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4124 b) As a value in the range 0..65535, contained in a 2-byte integer. All
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4125channels can be converted to the original value by dividing by 65535; all
4126channels are linear. Color channels use the RGB encoding (RGB end-points) of
4127the sRGB specification. This encoding is identified by the
4128PNG_FORMAT_FLAG_LINEAR flag below.
4129
4130When an alpha channel is present it is expected to denote pixel coverage
4131of the color or luminance channels and is returned as an associated alpha
4132channel: the color/gray channels are scaled (pre-multiplied) by the alpha
4133value.
4134
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4135When a color-mapped image is used as a result of calling
4136png_image_read_colormap or png_image_write_colormap the channels are encoded
4137in the color-map and the descriptions above apply to the color-map entries.
4138The image data is encoded as small integers, value 0..255, that index the
4139entries in the color-map. One integer (one byte) is stored for each pixel.
4140
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4141PNG_FORMAT_*
4142
4143The #defines to be used in png_image::format. Each #define identifies a
4144particular layout of channel data and, if present, alpha values. There are
4145separate defines for each of the two channel encodings.
4146
4147A format is built up using single bit flag values. Not all combinations are
4148valid: use the bit flag values below for testing a format returned by the
4149read APIs, but set formats from the derived values.
4150
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4151When reading or writing color-mapped images the format should be set to the
4152format of the entries in the color-map then png_image_{read,write}_colormap
4153called to read or write the color-map and set the format correctly for the
4154image data. Do not set the PNG_FORMAT_FLAG_COLORMAP bit directly!
4155
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4156NOTE: libpng can be built with particular features disabled, if you see
4157compiler errors because the definition of one of the following flags has been
4158compiled out it is because libpng does not have the required support. It is
4159possible, however, for the libpng configuration to enable the format on just
4160read or just write; in that case you may see an error at run time. You can
4161guard against this by checking for the definition of:
4162
4163 PNG_SIMPLIFIED_{READ,WRITE}_{BGR,AFIRST}_SUPPORTED
4164
4165 PNG_FORMAT_FLAG_ALPHA 0x01 format with an alpha channel
4166 PNG_FORMAT_FLAG_COLOR 0x02 color format: otherwise grayscale
4167 PNG_FORMAT_FLAG_LINEAR 0x04 png_uint_16 channels else png_byte
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4168 PNG_FORMAT_FLAG_COLORMAP 0x08 libpng use only
4169 PNG_FORMAT_FLAG_BGR 0x10 BGR colors, else order is RGB
4170 PNG_FORMAT_FLAG_AFIRST 0x20 alpha channel comes first
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4171
4172Supported formats are as follows. Future versions of libpng may support more
4173formats; for compatibility with older versions simply check if the format
4174macro is defined using #ifdef. These defines describe the in-memory layout
4175of the components of the pixels of the image.
4176
4177First the single byte formats:
4178
4179 PNG_FORMAT_GRAY 0
4180 PNG_FORMAT_GA PNG_FORMAT_FLAG_ALPHA
4181 PNG_FORMAT_AG (PNG_FORMAT_GA|PNG_FORMAT_FLAG_AFIRST)
4182 PNG_FORMAT_RGB PNG_FORMAT_FLAG_COLOR
4183 PNG_FORMAT_BGR (PNG_FORMAT_FLAG_COLOR|PNG_FORMAT_FLAG_BGR)
4184 PNG_FORMAT_RGBA (PNG_FORMAT_RGB|PNG_FORMAT_FLAG_ALPHA)
4185 PNG_FORMAT_ARGB (PNG_FORMAT_RGBA|PNG_FORMAT_FLAG_AFIRST)
4186 PNG_FORMAT_BGRA (PNG_FORMAT_BGR|PNG_FORMAT_FLAG_ALPHA)
4187 PNG_FORMAT_ABGR (PNG_FORMAT_BGRA|PNG_FORMAT_FLAG_AFIRST)
4188
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4189Then the linear 2-byte formats. When naming these "Y" is used to
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4190indicate a luminance (gray) channel. The component order within the pixel
4191is always the same - there is no provision for swapping the order of the
4192components in the linear format.
4193
4194 PNG_FORMAT_LINEAR_Y PNG_FORMAT_FLAG_LINEAR
4195 PNG_FORMAT_LINEAR_Y_ALPHA
4196 (PNG_FORMAT_FLAG_LINEAR|PNG_FORMAT_FLAG_ALPHA)
4197 PNG_FORMAT_LINEAR_RGB
4198 (PNG_FORMAT_FLAG_LINEAR|PNG_FORMAT_FLAG_COLOR)
4199 PNG_FORMAT_LINEAR_RGB_ALPHA
4200 (PNG_FORMAT_FLAG_LINEAR|PNG_FORMAT_FLAG_COLOR|
4201 PNG_FORMAT_FLAG_ALPHA)
4202
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4203Color-mapped formats are obtained by calling png_image_{read,write}_colormap,
4204as appropriate after setting png_image::format to the format of the color-map
4205to be read or written. Applications may check the value of
4206PNG_FORMAT_FLAG_COLORMAP to see if they have called the colormap API. The
4207format of the color-map may be extracted using the following macro.
4208
4209 PNG_FORMAT_OF_COLORMAP(fmt) ((fmt) & ~PNG_FORMAT_FLAG_COLORMAP)
4210
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4211PNG_IMAGE macros
4212
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4213These are convenience macros to derive information from a png_image
4214structure. The PNG_IMAGE_SAMPLE_ macros return values appropriate to the
4215actual image sample values - either the entries in the color-map or the
4216pixels in the image. The PNG_IMAGE_PIXEL_ macros return corresponding values
4217for the pixels and will always return 1 after a call to
4218png_image_{read,write}_colormap. The remaining macros return information
4219about the rows in the image and the complete image.
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4220
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4221NOTE: All the macros that take a png_image::format parameter are compile time
4222constants if the format parameter is, itself, a constant. Therefore these
4223macros can be used in array declarations and case labels where required.
4224Similarly the macros are also pre-processor constants (sizeof is not used) so
4225they can be used in #if tests.
4226
4227First the information about the samples.
4228
4229 PNG_IMAGE_SAMPLE_CHANNELS(fmt)
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4230 Returns the total number of channels in a given format: 1..4
4231
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4232 PNG_IMAGE_SAMPLE_COMPONENT_SIZE(fmt)
4233 Returns the size in bytes of a single component of a pixel or color-map
4234 entry (as appropriate) in the image.
4235
4236 PNG_IMAGE_SAMPLE_SIZE(fmt)
4237 This is the size of the sample data for one sample. If the image is
4238 color-mapped it is the size of one color-map entry (and image pixels are
4239 one byte in size), otherwise it is the size of one image pixel.
4240
4241 PNG_IMAGE_COLORMAP_SIZE(fmt)
4242 The size of the color-map required by the format; this is the size of the
4243 color-map buffer passed to the png_image_{read,write}_colormap APIs, it is
4244 a fixed number determined by the format so can easily be allocated on the
4245 stack if necessary.
4246
4247#define PNG_IMAGE_MAXIMUM_COLORMAP_COMPONENTS(fmt)\
4248 (PNG_IMAGE_SAMPLE_CHANNELS(fmt) * 256)
4249 /* The maximum size of the color-map required by the format expressed in a
4250 * count of components. This can be used to compile-time allocate a
4251 * color-map:
4252 *
4253 * png_uint_16 colormap[PNG_IMAGE_MAXIMUM_COLORMAP_COMPONENTS(linear_fmt)];
4254 *
4255 * png_byte colormap[PNG_IMAGE_MAXIMUM_COLORMAP_COMPONENTS(sRGB_fmt)];
4256 *
4257 * Alternatively use the PNG_IMAGE_COLORMAP_SIZE macro below to use the
4258 * information from one of the png_image_begin_read_ APIs and dynamically
4259 * allocate the required memory.
4260 */
4261
4262
4263Corresponding information about the pixels
4264
4265 PNG_IMAGE_PIXEL_(test,fmt)
4266
4267 PNG_IMAGE_PIXEL_CHANNELS(fmt)
4268 The number of separate channels (components) in a pixel; 1 for a
4269 color-mapped image.
4270
4271 PNG_IMAGE_PIXEL_COMPONENT_SIZE(fmt)\
4272 The size, in bytes, of each component in a pixel; 1 for a color-mapped
4273 image.
John Bowler6f237b62012-03-02 13:13:15 -0600[diff] [blame]4274
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4275 PNG_IMAGE_PIXEL_SIZE(fmt)
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4276 The size, in bytes, of a complete pixel; 1 for a color-mapped image.
4277
4278Information about the whole row, or whole image
4279
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4280 PNG_IMAGE_ROW_STRIDE(image)
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4281 Returns the total number of components in a single row of the image; this
4282 is the minimum 'row stride', the minimum count of components between each
4283 row. For a color-mapped image this is the minimum number of bytes in a
4284 row.
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4285
4286 PNG_IMAGE_BUFFER_SIZE(image, row_stride)
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4287 Returns the size, in bytes, of an image buffer given a png_image and a row
4288 stride - the number of components to leave space for in each row.
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4289
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4290 PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB == 0x01
4291 This indicates the the RGB values of the in-memory bitmap do not
4292 correspond to the red, green and blue end-points defined by sRGB.
John Bowler6f237b62012-03-02 13:13:15 -0600[diff] [blame]4293
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4294 PNG_IMAGE_FLAG_COLORMAP == 0x02
4295 The PNG is color-mapped. If this flag is set png_image_read_colormap
4296 can be used without further loss of image information. If it is not set
4297 png_image_read_colormap will cause significant loss if the image has any
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4298
4299READ APIs
4300
4301 The png_image passed to the read APIs must have been initialized by setting
4302 the png_controlp field 'opaque' to NULL (or, better, memset the whole thing.)
4303
4304 int png_image_begin_read_from_file( png_imagep image,
4305 const char *file_name)
4306
4307 The named file is opened for read and the image header
4308 is filled in from the PNG header in the file.
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4309
4310 int png_image_begin_read_from_stdio (png_imagep image,
4311 FILE* file)
4312
4313 The PNG header is read from the stdio FILE object.
4314
4315 int png_image_begin_read_from_memory(png_imagep image,
4316 png_const_voidp memory, png_size_t size)
4317
4318 The PNG header is read from the given memory buffer.
4319
4320 int png_image_finish_read(png_imagep image,
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4321 png_colorp background, void *buffer,
4322 png_int_32 row_stride, void *colormap));
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4323
4324 Finish reading the image into the supplied buffer and
4325 clean up the png_image structure.
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4326
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4327 row_stride is the step, in png_byte or png_uint_16 units
4328 as appropriate, between adjacent rows. A positive stride
4329 indicates that the top-most row is first in the buffer -
4330 the normal top-down arrangement. A negative stride
4331 indicates that the bottom-most row is first in the buffer.
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4332
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4333 background need only be supplied if an alpha channel must
4334 be removed from a png_byte format and the removal is to be
4335 done by compositing on a solid color; otherwise it may be
4336 NULL and any composition will be done directly onto the
4337 buffer. The value is an sRGB color to use for the
4338 background, for grayscale output the green channel is used.
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4339
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4340 For linear output removing the alpha channel is always done
4341 by compositing on black.
4342
4343 void png_image_free(png_imagep image)
4344
4345 Free any data allocated by libpng in image->opaque,
4346 setting the pointer to NULL. May be called at any time
4347 after the structure is initialized.
4348
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4349When the simplified API needs to convert between sRGB and linear colorspaces,
4350the actual sRGB transfer curve defined in the sRGB specification (see the
4351article at http://en.wikipedia.org/wiki/SRGB) is used, not the gamma=1/2.2
4352approximation used elsewhere in libpng.
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4353
4354WRITE APIS
4355
4356For write you must initialize a png_image structure to describe the image to
4357be written:
4358
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4359 version: must be set to PNG_IMAGE_VERSION
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4360 opaque: must be initialized to NULL
4361 width: image width in pixels
4362 height: image height in rows
4363 format: the format of the data you wish to write
4364 flags: set to 0 unless one of the defined flags applies; set
4365 PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB for color format images
4366 where the RGB values do not correspond to the colors in sRGB.
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4367 colormap_entries: set to the number of entries in the color-map (0 to 256)
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4368
4369 int png_image_write_to_file, (png_imagep image,
4370 const char *file, int convert_to_8bit, const void *buffer,
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4371 png_int_32 row_stride, const void *colormap));
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4372
4373 Write the image to the named file.
4374
4375 int png_image_write_to_stdio(png_imagep image, FILE *file,
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4376 int convert_to_8_bit, const void *buffer,
4377 png_int_32 row_stride, const void *colormap)
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4378
4379 Write the image to the given (FILE*).
4380
4381With all write APIs if image is in one of the linear formats with
4382(png_uint_16) data then setting convert_to_8_bit will cause the output to be
4383a (png_byte) PNG gamma encoded according to the sRGB specification, otherwise
4384a 16-bit linear encoded PNG file is written.
4385
4386With all APIs row_stride is handled as in the read APIs - it is the spacing
4387from one row to the next in component sized units (float) and if negative
4388indicates a bottom-up row layout in the buffer.
4389
4390Note that the write API does not support interlacing, sub-8-bit pixels,
4391and indexed (paletted) images.
4392
4393.SH VI. Modifying/Customizing libpng
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4394
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]4395There are two issues here. The first is changing how libpng does
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4396standard things like memory allocation, input/output, and error handling.
4397The second deals with more complicated things like adding new chunks,
4398adding new transformations, and generally changing how libpng works.
Glenn Randers-Pehrson231e6872001-01-12 15:13:06 -0600[diff] [blame]4399Both of those are compile-time issues; that is, they are generally
4400determined at the time the code is written, and there is rarely a need
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]4401to provide the user with a means of changing them.
Glenn Randers-Pehrson231e6872001-01-12 15:13:06 -0600[diff] [blame]4402
4403Memory allocation, input/output, and error handling
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4404
4405All of the memory allocation, input/output, and error handling in libpng
Glenn Randers-Pehrson231e6872001-01-12 15:13:06 -0600[diff] [blame]4406goes through callbacks that are user-settable. The default routines are
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4407in pngmem.c, pngrio.c, pngwio.c, and pngerror.c, respectively. To change
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]4408these functions, call the appropriate png_set_*_fn() function.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4409
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]4410Memory allocation is done through the functions png_malloc(), png_calloc(),
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4411and png_free(). The png_malloc() and png_free() functions currently just
4412call the standard C functions and png_calloc() calls png_malloc() and then
4413clears the newly allocated memory to zero; note that png_calloc(png_ptr, size)
4414is not the same as the calloc(number, size) function provided by stdlib.h.
4415There is limited support for certain systems with segmented memory
4416architectures and the types of pointers declared by png.h match this; you
4417will have to use appropriate pointers in your application. Since it is
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]4418unlikely that the method of handling memory allocation on a platform
4419will change between applications, these functions must be modified in
4420the library at compile time. If you prefer to use a different method
4421of allocating and freeing data, you can use png_create_read_struct_2() or
4422png_create_write_struct_2() to register your own functions as described
4423above. These functions also provide a void pointer that can be retrieved
4424via
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]4425
4426 mem_ptr=png_get_mem_ptr(png_ptr);
4427
4428Your replacement memory functions must have prototypes as follows:
4429
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]4430 png_voidp malloc_fn(png_structp png_ptr,
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]4431 png_alloc_size_t size);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4432
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]4433 void free_fn(png_structp png_ptr, png_voidp ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4434
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]4435Your malloc_fn() must return NULL in case of failure. The png_malloc()
4436function will normally call png_error() if it receives a NULL from the
4437system memory allocator or from your replacement malloc_fn().
Glenn Randers-Pehrson82ae3832001-04-20 10:32:10 -0500[diff] [blame]4438
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]4439Your free_fn() will never be called with a NULL ptr, since libpng's
4440png_free() checks for NULL before calling free_fn().
4441
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4442Input/Output in libpng is done through png_read() and png_write(),
4443which currently just call fread() and fwrite(). The FILE * is stored in
4444png_struct and is initialized via png_init_io(). If you wish to change
4445the method of I/O, the library supplies callbacks that you can set
4446through the function png_set_read_fn() and png_set_write_fn() at run
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]4447time, instead of calling the png_init_io() function. These functions
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4448also provide a void pointer that can be retrieved via the function
4449png_get_io_ptr(). For example:
4450
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]4451 png_set_read_fn(png_structp read_ptr,
4452 voidp read_io_ptr, png_rw_ptr read_data_fn)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4453
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]4454 png_set_write_fn(png_structp write_ptr,
4455 voidp write_io_ptr, png_rw_ptr write_data_fn,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4456 png_flush_ptr output_flush_fn);
4457
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]4458 voidp read_io_ptr = png_get_io_ptr(read_ptr);
4459 voidp write_io_ptr = png_get_io_ptr(write_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4460
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]4461The replacement I/O functions must have prototypes as follows:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4462
4463 void user_read_data(png_structp png_ptr,
Glenn Randers-Pehrson837a3d12002-05-10 20:19:58 -0500[diff] [blame]4464 png_bytep data, png_size_t length);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4465
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4466 void user_write_data(png_structp png_ptr,
Glenn Randers-Pehrson837a3d12002-05-10 20:19:58 -0500[diff] [blame]4467 png_bytep data, png_size_t length);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4468
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4469 void user_flush_data(png_structp png_ptr);
4470
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]4471The user_read_data() function is responsible for detecting and
4472handling end-of-data errors.
4473
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4474Supplying NULL for the read, write, or flush functions sets them back
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]4475to using the default C stream functions, which expect the io_ptr to
4476point to a standard *FILE structure. It is probably a mistake
4477to use NULL for one of write_data_fn and output_flush_fn but not both
4478of them, unless you have built libpng with PNG_NO_WRITE_FLUSH defined.
4479It is an error to read from a write stream, and vice versa.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4480
4481Error handling in libpng is done through png_error() and png_warning().
4482Errors handled through png_error() are fatal, meaning that png_error()
4483should never return to its caller. Currently, this is handled via
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4484setjmp() and longjmp() (unless you have compiled libpng with
Glenn Randers-Pehrson54ac9a92010-04-02 17:06:22 -0500[diff] [blame]4485PNG_NO_SETJMP, in which case it is handled via PNG_ABORT()),
Glenn Randers-Pehrson60988072010-04-13 22:11:06 -0500[diff] [blame]4486but you could change this to do things like exit() if you should wish,
Glenn Randers-Pehrson54ac9a92010-04-02 17:06:22 -0500[diff] [blame]4487as long as your function does not return.
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4488
4489On non-fatal errors, png_warning() is called
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4490to print a warning message, and then control returns to the calling code.
4491By default png_error() and png_warning() print a message on stderr via
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]4492fprintf() unless the library is compiled with PNG_NO_CONSOLE_IO defined
4493(because you don't want the messages) or PNG_NO_STDIO defined (because
4494fprintf() isn't available). If you wish to change the behavior of the error
4495functions, you will need to set up your own message callbacks. These
4496functions are normally supplied at the time that the png_struct is created.
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4497It is also possible to redirect errors and warnings to your own replacement
4498functions after png_create_*_struct() has been called by calling:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4499
4500 png_set_error_fn(png_structp png_ptr,
4501 png_voidp error_ptr, png_error_ptr error_fn,
4502 png_error_ptr warning_fn);
4503
4504 png_voidp error_ptr = png_get_error_ptr(png_ptr);
4505
4506If NULL is supplied for either error_fn or warning_fn, then the libpng
4507default function will be used, calling fprintf() and/or longjmp() if a
4508problem is encountered. The replacement error functions should have
4509parameters as follows:
4510
4511 void user_error_fn(png_structp png_ptr,
4512 png_const_charp error_msg);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4513
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4514 void user_warning_fn(png_structp png_ptr,
4515 png_const_charp warning_msg);
4516
4517The motivation behind using setjmp() and longjmp() is the C++ throw and
4518catch exception handling methods. This makes the code much easier to write,
4519as there is no need to check every return code of every function call.
4520However, there are some uncertainties about the status of local variables
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]4521after a longjmp, so the user may want to be careful about doing anything
4522after setjmp returns non-zero besides returning itself. Consult your
4523compiler documentation for more details. For an alternative approach, you
Glenn Randers-Pehrsona5e55472011-07-12 10:13:32 -0500[diff] [blame]4524may wish to use the "cexcept" facility (see http://cexcept.sourceforge.net),
4525which is illustrated in pngvalid.c and in contrib/visupng.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4526
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4527Beginning in libpng-1.4.0, the png_set_benign_errors() API became available.
4528You can use this to handle certain errors (normally handled as errors)
4529as warnings.
4530
4531 png_set_benign_errors (png_ptr, int allowed);
4532
Glenn Randers-Pehrsond5dd93f2013-07-02 09:20:36 -0500[diff] [blame]4533 allowed: 0: treat png_benign_error() as an error.
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4534 1: treat png_benign_error() as a warning.
4535
Glenn Randers-Pehrsond5dd93f2013-07-02 09:20:36 -0500[diff] [blame]4536As of libpng-1.6.0, the default condition is to treat benign errors as
4537warnings while reading and as errors while writing.
4538
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4539.SS Custom chunks
4540
4541If you need to read or write custom chunks, you may need to get deeper
4542into the libpng code. The library now has mechanisms for storing
4543and writing chunks of unknown type; you can even declare callbacks
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]4544for custom chunks. However, this may not be good enough if the
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4545library code itself needs to know about interactions between your
4546chunk and existing `intrinsic' chunks.
4547
4548If you need to write a new intrinsic chunk, first read the PNG
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]4549specification. Acquire a first level of understanding of how it works.
4550Pay particular attention to the sections that describe chunk names,
4551and look at how other chunks were designed, so you can do things
4552similarly. Second, check out the sections of libpng that read and
4553write chunks. Try to find a chunk that is similar to yours and use
4554it as a template. More details can be found in the comments inside
Glenn Randers-Pehrsona5e55472011-07-12 10:13:32 -0500[diff] [blame]4555the code. It is best to handle private or unknown chunks in a generic method,
4556via callback functions, instead of by modifying libpng functions. This
4557is illustrated in pngtest.c, which uses a callback function to handle a
4558private "vpAg" chunk and the new "sTER" chunk, which are both unknown to
4559libpng.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4560
4561If you wish to write your own transformation for the data, look through
4562the part of the code that does the transformations, and check out some of
4563the simpler ones to get an idea of how they work. Try to find a similar
4564transformation to the one you want to add and copy off of it. More details
4565can be found in the comments inside the code itself.
4566
Glenn Randers-Pehrson593fc042011-05-12 22:18:23 -0500[diff] [blame]4567.SS Configuring for 16-bit platforms
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4568
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4569You will want to look into zconf.h to tell zlib (and thus libpng) that
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4570it cannot allocate more then 64K at a time. Even if you can, the memory
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]4571won't be accessible. So limit zlib and libpng to 64K by defining MAXSEG_64K.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4572
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4573.SS Configuring for DOS
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4574
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4575For DOS users who only have access to the lower 640K, you will
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4576have to limit zlib's memory usage via a png_set_compression_mem_level()
4577call. See zlib.h or zconf.h in the zlib library for more information.
4578
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4579.SS Configuring for Medium Model
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4580
4581Libpng's support for medium model has been tested on most of the popular
4582compilers. Make sure MAXSEG_64K gets defined, USE_FAR_KEYWORD gets
4583defined, and FAR gets defined to far in pngconf.h, and you should be
4584all set. Everything in the library (except for zlib's structure) is
4585expecting far data. You must use the typedefs with the p or pp on
4586the end for pointers (or at least look at them and be careful). Make
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]4587note that the rows of data are defined as png_bytepp, which is
4588an "unsigned char far * far *".
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4589
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4590.SS Configuring for gui/windowing platforms:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4591
4592You will need to write new error and warning functions that use the GUI
4593interface, as described previously, and set them to be the error and
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]4594warning functions at the time that png_create_*_struct() is called,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4595in order to have them available during the structure initialization.
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]4596They can be changed later via png_set_error_fn(). On some compilers,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4597you may also have to change the memory allocators (png_malloc, etc.).
4598
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4599.SS Configuring for compiler xxx:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4600
Glenn Randers-Pehrsonbeb572e2006-08-19 13:59:24 -0500[diff] [blame]4601All includes for libpng are in pngconf.h. If you need to add, change
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]4602or delete an include, this is the place to do it.
4603The includes that are not needed outside libpng are placed in pngpriv.h,
4604which is only used by the routines inside libpng itself.
4605The files in libpng proper only include pngpriv.h and png.h, which
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]4606%14%in turn includes pngconf.h.
4607in turn includes pngconf.h and, as of libpng-1.5.0, pnglibconf.h.
4608As of libpng-1.5.0, pngpriv.h also includes three other private header
4609files, pngstruct.h, pnginfo.h, and pngdebug.h, which contain material
4610that previously appeared in the public headers.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4611
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4612.SS Configuring zlib:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4613
4614There are special functions to configure the compression. Perhaps the
4615most useful one changes the compression level, which currently uses
4616input compression values in the range 0 - 9. The library normally
4617uses the default compression level (Z_DEFAULT_COMPRESSION = 6). Tests
4618have shown that for a large majority of images, compression values in
4619the range 3-6 compress nearly as well as higher levels, and do so much
4620faster. For online applications it may be desirable to have maximum speed
4621(Z_BEST_SPEED = 1). With versions of zlib after v0.99, you can also
4622specify no compression (Z_NO_COMPRESSION = 0), but this would create
4623files larger than just storing the raw bitmap. You can specify the
4624compression level by calling:
4625
Glenn Randers-Pehrson38734ee2011-03-03 06:23:31 -0600[diff] [blame]4626 #include zlib.h
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4627 png_set_compression_level(png_ptr, level);
4628
4629Another useful one is to reduce the memory level used by the library.
4630The memory level defaults to 8, but it can be lowered if you are
4631short on memory (running DOS, for example, where you only have 640K).
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]4632Note that the memory level does have an effect on compression; among
4633other things, lower levels will result in sections of incompressible
4634data being emitted in smaller stored blocks, with a correspondingly
4635larger relative overhead of up to 15% in the worst case.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4636
Glenn Randers-Pehrson38734ee2011-03-03 06:23:31 -0600[diff] [blame]4637 #include zlib.h
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4638 png_set_compression_mem_level(png_ptr, level);
4639
4640The other functions are for configuring zlib. They are not recommended
4641for normal use and may result in writing an invalid PNG file. See
4642zlib.h for more information on what these mean.
4643
Glenn Randers-Pehrson38734ee2011-03-03 06:23:31 -0600[diff] [blame]4644 #include zlib.h
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4645 png_set_compression_strategy(png_ptr,
4646 strategy);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4647
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4648 png_set_compression_window_bits(png_ptr,
4649 window_bits);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4650
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4651 png_set_compression_method(png_ptr, method);
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]4652
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4653 png_set_compression_buffer_size(png_ptr, size);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4654
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]4655As of libpng version 1.5.4, additional APIs became
4656available to set these separately for non-IDAT
4657compressed chunks such as zTXt, iTXt, and iCCP:
4658
4659 #include zlib.h
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4660 #if PNG_LIBPNG_VER >= 10504
Glenn Randers-Pehrson7a287242011-07-26 12:03:11 -0500[diff] [blame]4661 png_set_text_compression_level(png_ptr, level);
4662
4663 png_set_text_compression_mem_level(png_ptr, level);
4664
4665 png_set_text_compression_strategy(png_ptr,
4666 strategy);
4667
4668 png_set_text_compression_window_bits(png_ptr,
4669 window_bits);
4670
4671 png_set_text_compression_method(png_ptr, method);
4672 #endif
4673
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4674.SS Controlling row filtering
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4675
4676If you want to control whether libpng uses filtering or not, which
4677filters are used, and how it goes about picking row filters, you
4678can call one of these functions. The selection and configuration
4679of row filters can have a significant impact on the size and
4680encoding speed and a somewhat lesser impact on the decoding speed
4681of an image. Filtering is enabled by default for RGB and grayscale
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4682images (with and without alpha), but not for paletted images nor
4683for any images with bit depths less than 8 bits/pixel.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4684
4685The 'method' parameter sets the main filtering method, which is
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]4686currently only '0' in the PNG 1.2 specification. The 'filters'
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4687parameter sets which filter(s), if any, should be used for each
4688scanline. Possible values are PNG_ALL_FILTERS and PNG_NO_FILTERS
4689to turn filtering on and off, respectively.
4690
4691Individual filter types are PNG_FILTER_NONE, PNG_FILTER_SUB,
4692PNG_FILTER_UP, PNG_FILTER_AVG, PNG_FILTER_PAETH, which can be bitwise
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]4693ORed together with '|' to specify one or more filters to use.
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]4694These filters are described in more detail in the PNG specification.
4695If you intend to change the filter type during the course of writing
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4696the image, you should start with flags set for all of the filters
4697you intend to use so that libpng can initialize its internal
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]4698structures appropriately for all of the filter types. (Note that this
4699means the first row must always be adaptively filtered, because libpng
4700currently does not allocate the filter buffers until png_write_row()
4701is called for the first time.)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4702
4703 filters = PNG_FILTER_NONE | PNG_FILTER_SUB
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4704 PNG_FILTER_UP | PNG_FILTER_AVG |
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4705 PNG_FILTER_PAETH | PNG_ALL_FILTERS;
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4706
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4707 png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE,
4708 filters);
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]4709 The second parameter can also be
4710 PNG_INTRAPIXEL_DIFFERENCING if you are
4711 writing a PNG to be embedded in a MNG
4712 datastream. This parameter must be the
4713 same as the value of filter_method used
4714 in png_set_IHDR().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4715
4716It is also possible to influence how libpng chooses from among the
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]4717available filters. This is done in one or both of two ways - by
4718telling it how important it is to keep the same filter for successive
4719rows, and by telling it the relative computational costs of the filters.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4720
4721 double weights[3] = {1.5, 1.3, 1.1},
4722 costs[PNG_FILTER_VALUE_LAST] =
4723 {1.0, 1.3, 1.3, 1.5, 1.7};
4724
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]4725 png_set_filter_heuristics(png_ptr,
4726 PNG_FILTER_HEURISTIC_WEIGHTED, 3,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4727 weights, costs);
4728
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4729The weights are multiplying factors that indicate to libpng that the
4730row filter should be the same for successive rows unless another row filter
4731is that many times better than the previous filter. In the above example,
4732if the previous 3 filters were SUB, SUB, NONE, the SUB filter could have a
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4733"sum of absolute differences" 1.5 x 1.3 times higher than other filters
4734and still be chosen, while the NONE filter could have a sum 1.1 times
4735higher than other filters and still be chosen. Unspecified weights are
4736taken to be 1.0, and the specified weights should probably be declining
4737like those above in order to emphasize recent filters over older filters.
4738
4739The filter costs specify for each filter type a relative decoding cost
4740to be considered when selecting row filters. This means that filters
4741with higher costs are less likely to be chosen over filters with lower
4742costs, unless their "sum of absolute differences" is that much smaller.
4743The costs do not necessarily reflect the exact computational speeds of
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]4744the various filters, since this would unduly influence the final image
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4745size.
4746
4747Note that the numbers above were invented purely for this example and
4748are given only to help explain the function usage. Little testing has
4749been done to find optimum values for either the costs or the weights.
4750
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4751.SS Removing unwanted object code
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4752
4753There are a bunch of #define's in pngconf.h that control what parts of
4754libpng are compiled. All the defines end in _SUPPORTED. If you are
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]4755never going to use a capability, you can change the #define to #undef
4756before recompiling libpng and save yourself code and data space, or
4757you can turn off individual capabilities with defines that begin with
4758PNG_NO_.
4759
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4760In libpng-1.5.0 and later, the #define's are in pnglibconf.h instead.
4761
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]4762You can also turn all of the transforms and ancillary chunk capabilities
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4763off en masse with compiler directives that define
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]4764PNG_NO_READ[or WRITE]_TRANSFORMS, or PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS,
4765or all four,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4766along with directives to turn on any of the capabilities that you do
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]4767want. The PNG_NO_READ[or WRITE]_TRANSFORMS directives disable the extra
4768transformations but still leave the library fully capable of reading
4769and writing PNG files with all known public chunks. Use of the
4770PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS directive produces a library
4771that is incapable of reading or writing ancillary chunks. If you are
4772not using the progressive reading capability, you can turn that off
4773with PNG_NO_PROGRESSIVE_READ (don't confuse this with the INTERLACING
4774capability, which you'll still have).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4775
4776All the reading and writing specific code are in separate files, so the
4777linker should only grab the files it needs. However, if you want to
4778make sure, or if you are building a stand alone library, all the
Glenn Randers-Pehrsona5e55472011-07-12 10:13:32 -0500[diff] [blame]4779reading files start with "pngr" and all the writing files start with "pngw".
4780The files that don't match either (like png.c, pngtrans.c, etc.)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4781are used for both reading and writing, and always need to be included.
4782The progressive reader is in pngpread.c
4783
4784If you are creating or distributing a dynamically linked library (a .so
4785or DLL file), you should not remove or disable any parts of the library,
4786as this will cause applications linked with different versions of the
4787library to fail if they call functions not available in your library.
4788The size of the library itself should not be an issue, because only
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4789those sections that are actually used will be loaded into memory.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4790
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4791.SS Requesting debug printout
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4792
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4793The macro definition PNG_DEBUG can be used to request debugging
4794printout. Set it to an integer value in the range 0 to 3. Higher
4795numbers result in increasing amounts of debugging information. The
4796information is printed to the "stderr" file, unless another file
4797name is specified in the PNG_DEBUG_FILE macro definition.
4798
4799When PNG_DEBUG > 0, the following functions (macros) become available:
4800
4801 png_debug(level, message)
4802 png_debug1(level, message, p1)
4803 png_debug2(level, message, p1, p2)
4804
4805in which "level" is compared to PNG_DEBUG to decide whether to print
4806the message, "message" is the formatted string to be printed,
4807and p1 and p2 are parameters that are to be embedded in the string
4808according to printf-style formatting directives. For example,
4809
Glenn Randers-Pehrsonbbc29a82013-06-18 12:55:37 -0500[diff] [blame]4810 png_debug1(2, "foo=%d", foo);
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4811
4812is expanded to
4813
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4814 if (PNG_DEBUG > 2)
Glenn Randers-Pehrsonbbc29a82013-06-18 12:55:37 -0500[diff] [blame]4815 fprintf(PNG_DEBUG_FILE, "foo=%d\en", foo);
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4816
4817When PNG_DEBUG is defined but is zero, the macros aren't defined, but you
4818can still use PNG_DEBUG to control your own debugging:
4819
4820 #ifdef PNG_DEBUG
4821 fprintf(stderr, ...
4822 #endif
4823
4824When PNG_DEBUG = 1, the macros are defined, but only png_debug statements
4825having level = 0 will be printed. There aren't any such statements in
4826this version of libpng, but if you insert some they will be printed.
4827
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4828.SS Prepending a prefix to exported symbols
4829
4830Starting with libpng-1.6.0, you can configure libpng (when using the
4831"configure" script) to prefix all exported symbols by means of the
Glenn Randers-Pehrson4dcbf242013-08-06 17:20:06 -0500[diff] [blame]4832configuration option "\-\-with\-libpng\-prefix=FOO_", where FOO_ can be any
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]4833string beginning with a letter and containing only uppercase
4834and lowercase letters, digits, and the underscore (i.e., a C language
4835identifier). This creates a set of macros in pnglibconf.h, so this is
4836transparent to applications; their function calls get transformed by
4837the macros to use the modified names.
4838
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4839.SH VII. MNG support
Glenn Randers-Pehrson2ad31ae2000-12-15 08:54:42 -0600[diff] [blame]4840
4841The MNG specification (available at http://www.libpng.org/pub/mng) allows
4842certain extensions to PNG for PNG images that are embedded in MNG datastreams.
4843Libpng can support some of these extensions. To enable them, use the
4844png_permit_mng_features() function:
4845
4846 feature_set = png_permit_mng_features(png_ptr, mask)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4847
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]4848 mask is a png_uint_32 containing the bitwise OR of the
Glenn Randers-Pehrson2ad31ae2000-12-15 08:54:42 -0600[diff] [blame]4849 features you want to enable. These include
4850 PNG_FLAG_MNG_EMPTY_PLTE
4851 PNG_FLAG_MNG_FILTER_64
4852 PNG_ALL_MNG_FEATURES
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4853
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]4854 feature_set is a png_uint_32 that is the bitwise AND of
Glenn Randers-Pehrson2ad31ae2000-12-15 08:54:42 -0600[diff] [blame]4855 your mask with the set of MNG features that is
4856 supported by the version of libpng that you are using.
4857
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]4858It is an error to use this function when reading or writing a standalone
4859PNG file with the PNG 8-byte signature. The PNG datastream must be wrapped
Glenn Randers-Pehrsonf05f8032000-12-23 14:27:39 -0600[diff] [blame]4860in a MNG datastream. As a minimum, it must have the MNG 8-byte signature
4861and the MHDR and MEND chunks. Libpng does not provide support for these
4862or any other MNG chunks; your application must provide its own support for
4863them. You may wish to consider using libmng (available at
4864http://www.libmng.com) instead.
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]4865
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4866.SH VIII. Changes to Libpng from version 0.88
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4867
4868It should be noted that versions of libpng later than 0.96 are not
4869distributed by the original libpng author, Guy Schalnat, nor by
4870Andreas Dilger, who had taken over from Guy during 1996 and 1997, and
4871distributed versions 0.89 through 0.96, but rather by another member
4872of the original PNG Group, Glenn Randers-Pehrson. Guy and Andreas are
4873still alive and well, but they have moved on to other things.
4874
4875The old libpng functions png_read_init(), png_write_init(),
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]4876png_info_init(), png_read_destroy(), and png_write_destroy() have been
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]4877moved to PNG_INTERNAL in version 0.95 to discourage their use. These
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4878functions will be removed from libpng version 1.4.0.
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]4879
4880The preferred method of creating and initializing the libpng structures is
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4881via the png_create_read_struct(), png_create_write_struct(), and
4882png_create_info_struct() because they isolate the size of the structures
4883from the application, allow version error checking, and also allow the
4884use of custom error handling routines during the initialization, which
4885the old functions do not. The functions png_read_destroy() and
4886png_write_destroy() do not actually free the memory that libpng
4887allocated for these structs, but just reset the data structures, so they
4888can be used instead of png_destroy_read_struct() and
4889png_destroy_write_struct() if you feel there is too much system overhead
4890allocating and freeing the png_struct for each image read.
4891
4892Setting the error callbacks via png_set_message_fn() before
4893png_read_init() as was suggested in libpng-0.88 is no longer supported
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4894because this caused applications that do not use custom error functions
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4895to fail if the png_ptr was not initialized to zero. It is still possible
4896to set the error callbacks AFTER png_read_init(), or to change them with
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]4897png_set_error_fn(), which is essentially the same function, but with a new
4898name to force compilation errors with applications that try to use the old
4899method.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4900
Glenn Randers-Pehrson759c9032014-02-01 20:11:48 -0600[diff] [blame^]4901Support for the sCAL, iCCP, iTXt, and sPLT chunks was added at libpng-1.0.6;
4902however, iTXt support was not enabled by default.
4903
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]4904Starting with version 1.0.7, you can find out which version of the library
4905you are using at run-time:
4906
4907 png_uint_32 libpng_vn = png_access_version_number();
4908
4909The number libpng_vn is constructed from the major version, minor
4910version with leading zero, and release number with leading zero,
4911(e.g., libpng_vn for version 1.0.7 is 10007).
4912
Glenn Randers-Pehrson95ba4172011-09-08 12:21:42 -0500[diff] [blame]4913Note that this function does not take a png_ptr, so you can call it
4914before you've created one.
4915
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]4916You can also check which version of png.h you used when compiling your
4917application:
4918
4919 png_uint_32 application_vn = PNG_LIBPNG_VER;
4920
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]4921.SH IX. Changes to Libpng from version 1.0.x to 1.2.x
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]4922
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4923Support for user memory management was enabled by default. To
4924accomplish this, the functions png_create_read_struct_2(),
4925png_create_write_struct_2(), png_set_mem_fn(), png_get_mem_ptr(),
4926png_malloc_default(), and png_free_default() were added.
4927
Glenn Randers-Pehrsond6ea40a2009-11-02 07:32:00 -0600[diff] [blame]4928Support for the iTXt chunk has been enabled by default as of
4929version 1.2.41.
4930
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4931Support for certain MNG features was enabled.
4932
4933Support for numbered error messages was added. However, we never got
4934around to actually numbering the error messages. The function
4935png_set_strip_error_numbers() was added (Note: the prototype for this
4936function was inadvertently removed from png.h in PNG_NO_ASSEMBLER_CODE
4937builds of libpng-1.2.15. It was restored in libpng-1.2.36).
4938
4939The png_malloc_warn() function was added at libpng-1.2.3. This issues
4940a png_warning and returns NULL instead of aborting when it fails to
4941acquire the requested memory allocation.
4942
4943Support for setting user limits on image width and height was enabled
4944by default. The functions png_set_user_limits(), png_get_user_width_max(),
4945and png_get_user_height_max() were added at libpng-1.2.6.
4946
4947The png_set_add_alpha() function was added at libpng-1.2.7.
4948
4949The function png_set_expand_gray_1_2_4_to_8() was added at libpng-1.2.9.
4950Unlike png_set_gray_1_2_4_to_8(), the new function does not expand the
4951tRNS chunk to alpha. The png_set_gray_1_2_4_to_8() function is
4952deprecated.
4953
4954A number of macro definitions in support of runtime selection of
4955assembler code features (especially Intel MMX code support) were
4956added at libpng-1.2.0:
4957
4958 PNG_ASM_FLAG_MMX_SUPPORT_COMPILED
4959 PNG_ASM_FLAG_MMX_SUPPORT_IN_CPU
4960 PNG_ASM_FLAG_MMX_READ_COMBINE_ROW
4961 PNG_ASM_FLAG_MMX_READ_INTERLACE
4962 PNG_ASM_FLAG_MMX_READ_FILTER_SUB
4963 PNG_ASM_FLAG_MMX_READ_FILTER_UP
4964 PNG_ASM_FLAG_MMX_READ_FILTER_AVG
4965 PNG_ASM_FLAG_MMX_READ_FILTER_PAETH
4966 PNG_ASM_FLAGS_INITIALIZED
4967 PNG_MMX_READ_FLAGS
4968 PNG_MMX_FLAGS
4969 PNG_MMX_WRITE_FLAGS
4970 PNG_MMX_FLAGS
4971
4972We added the following functions in support of runtime
4973selection of assembler code features:
4974
4975 png_get_mmx_flagmask()
4976 png_set_mmx_thresholds()
4977 png_get_asm_flags()
4978 png_get_mmx_bitdepth_threshold()
4979 png_get_mmx_rowbytes_threshold()
4980 png_set_asm_flags()
4981
4982We replaced all of these functions with simple stubs in libpng-1.2.20,
4983when the Intel assembler code was removed due to a licensing issue.
4984
Glenn Randers-Pehrson3d893a02009-08-31 13:32:46 -0500[diff] [blame]4985These macros are deprecated:
4986
4987 PNG_READ_TRANSFORMS_NOT_SUPPORTED
4988 PNG_PROGRESSIVE_READ_NOT_SUPPORTED
4989 PNG_NO_SEQUENTIAL_READ_SUPPORTED
4990 PNG_WRITE_TRANSFORMS_NOT_SUPPORTED
4991 PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED
4992 PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED
4993
4994They have been replaced, respectively, by:
4995
4996 PNG_NO_READ_TRANSFORMS
4997 PNG_NO_PROGRESSIVE_READ
4998 PNG_NO_SEQUENTIAL_READ
4999 PNG_NO_WRITE_TRANSFORMS
5000 PNG_NO_READ_ANCILLARY_CHUNKS
5001 PNG_NO_WRITE_ANCILLARY_CHUNKS
5002
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]5003PNG_MAX_UINT was replaced with PNG_UINT_31_MAX. It has been
5004deprecated since libpng-1.0.16 and libpng-1.2.6.
5005
5006The function
5007 png_check_sig(sig, num)
5008was replaced with
5009 !png_sig_cmp(sig, 0, num)
5010It has been deprecated since libpng-0.90.
5011
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]5012The function
5013 png_set_gray_1_2_4_to_8()
5014which also expands tRNS to alpha was replaced with
5015 png_set_expand_gray_1_2_4_to_8()
5016which does not. It has been deprecated since libpng-1.0.18 and 1.2.9.
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]5017
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]5018.SH X. Changes to Libpng from version 1.0.x/1.2.x to 1.4.x
Glenn Randers-Pehrsond740c842009-11-04 19:01:54 -0600[diff] [blame]5019
5020Private libpng prototypes and macro definitions were moved from
5021png.h and pngconf.h into a new pngpriv.h header file.
5022
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]5023Functions png_set_benign_errors(), png_benign_error(), and
5024png_chunk_benign_error() were added.
5025
5026Support for setting the maximum amount of memory that the application
5027will allocate for reading chunks was added, as a security measure.
5028The functions png_set_chunk_cache_max() and png_get_chunk_cache_max()
5029were added to the library.
5030
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]5031We implemented support for I/O states by adding png_ptr member io_state
5032and functions png_get_io_chunk_name() and png_get_io_state() in pngget.c
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]5033
Glenn Randers-Pehrson5df7edb2009-10-29 23:32:44 -0500[diff] [blame]5034We added PNG_TRANSFORM_GRAY_TO_RGB to the available high-level
5035input transforms.
5036
Glenn Randers-Pehrson5df7edb2009-10-29 23:32:44 -0500[diff] [blame]5037Checking for and reporting of errors in the IHDR chunk is more thorough.
5038
Glenn Randers-Pehrson45af8192009-12-30 08:37:29 -0600[diff] [blame]5039Support for global arrays was removed, to improve thread safety.
5040
5041Some obsolete/deprecated macros and functions have been removed.
5042
5043Typecasted NULL definitions such as
5044 #define png_voidp_NULL (png_voidp)NULL
5045were eliminated. If you used these in your application, just use
5046NULL instead.
5047
5048The png_struct and info_struct members "trans" and "trans_values" were
5049changed to "trans_alpha" and "trans_color", respectively.
5050
5051The obsolete, unused pnggccrd.c and pngvcrd.c files and related makefiles
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]5052were removed.
Glenn Randers-Pehrson45af8192009-12-30 08:37:29 -0600[diff] [blame]5053
5054The PNG_1_0_X and PNG_1_2_X macros were eliminated.
5055
Glenn Randers-Pehrson5df7edb2009-10-29 23:32:44 -0500[diff] [blame]5056The PNG_LEGACY_SUPPORTED macro was eliminated.
5057
5058Many WIN32_WCE #ifdefs were removed.
5059
5060The functions png_read_init(info_ptr), png_write_init(info_ptr),
5061png_info_init(info_ptr), png_read_destroy(), and png_write_destroy()
5062have been removed. They have been deprecated since libpng-0.95.
5063
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]5064The png_permit_empty_plte() was removed. It has been deprecated
5065since libpng-1.0.9. Use png_permit_mng_features() instead.
5066
5067We removed the obsolete stub functions png_get_mmx_flagmask(),
5068png_set_mmx_thresholds(), png_get_asm_flags(),
5069png_get_mmx_bitdepth_threshold(), png_get_mmx_rowbytes_threshold(),
5070png_set_asm_flags(), and png_mmx_supported()
5071
Glenn Randers-Pehrson45af8192009-12-30 08:37:29 -0600[diff] [blame]5072We removed the obsolete png_check_sig(), png_memcpy_check(), and
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]5073png_memset_check() functions. Instead use !png_sig_cmp(), memcpy(),
5074and memset(), respectively.
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]5075
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]5076The function png_set_gray_1_2_4_to_8() was removed. It has been
5077deprecated since libpng-1.0.18 and 1.2.9, when it was replaced with
5078png_set_expand_gray_1_2_4_to_8() because the former function also
Glenn Randers-Pehrsonc36bb792011-02-12 09:49:07 -0600[diff] [blame]5079expanded any tRNS chunk to an alpha channel.
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]5080
Glenn Randers-Pehrson5b40b012010-11-25 07:16:29 -0600[diff] [blame]5081Macros for png_get_uint_16, png_get_uint_32, and png_get_int_32
5082were added and are used by default instead of the corresponding
5083functions. Unfortunately,
Glenn Randers-Pehrsonc36bb792011-02-12 09:49:07 -0600[diff] [blame]5084from libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the
Glenn Randers-Pehrson5b40b012010-11-25 07:16:29 -0600[diff] [blame]5085function) incorrectly returned a value of type png_uint_32.
5086
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]5087We changed the prototype for png_malloc() from
5088 png_malloc(png_structp png_ptr, png_uint_32 size)
5089to
5090 png_malloc(png_structp png_ptr, png_alloc_size_t size)
5091
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]5092This also applies to the prototype for the user replacement malloc_fn().
5093
Glenn Randers-Pehrson45af8192009-12-30 08:37:29 -0600[diff] [blame]5094The png_calloc() function was added and is used in place of
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]5095of "png_malloc(); memset();" except in the case in png_read_png()
Glenn Randers-Pehrson45af8192009-12-30 08:37:29 -0600[diff] [blame]5096where the array consists of pointers; in this case a "for" loop is used
5097after the png_malloc() to set the pointers to NULL, to give robust.
5098behavior in case the application runs out of memory part-way through
5099the process.
5100
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]5101We changed the prototypes of png_get_compression_buffer_size() and
5102png_set_compression_buffer_size() to work with png_size_t instead of
5103png_uint_32.
5104
Glenn Randers-Pehrson45af8192009-12-30 08:37:29 -0600[diff] [blame]5105Support for numbered error messages was removed by default, since we
5106never got around to actually numbering the error messages. The function
5107png_set_strip_error_numbers() was removed from the library by default.
5108
5109The png_zalloc() and png_zfree() functions are no longer exported.
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]5110The png_zalloc() function no longer zeroes out the memory that it
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5111allocates. Applications that called png_zalloc(png_ptr, number, size)
5112can call png_calloc(png_ptr, number*size) instead, and can call
5113png_free() instead of png_zfree().
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]5114
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]5115Support for dithering was disabled by default in libpng-1.4.0, because
Glenn Randers-Pehrson9f1cd702011-04-16 19:40:23 -0500[diff] [blame]5116it has not been well tested and doesn't actually "dither".
5117The code was not
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]5118removed, however, and could be enabled by building libpng with
5119PNG_READ_DITHER_SUPPORTED defined. In libpng-1.4.2, this support
Glenn Randers-Pehrson4dcbf242013-08-06 17:20:06 -0500[diff] [blame]5120was re-enabled, but the function was renamed png_set_quantize() to
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]5121reflect more accurately what it actually does. At the same time,
5122the PNG_DITHER_[RED,GREEN_BLUE]_BITS macros were also renamed to
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]5123PNG_QUANTIZE_[RED,GREEN,BLUE]_BITS, and PNG_READ_DITHER_SUPPORTED
5124was renamed to PNG_READ_QUANTIZE_SUPPORTED.
Glenn Randers-Pehrson60988072010-04-13 22:11:06 -0500[diff] [blame]5125
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]5126We removed the trailing '.' from the warning and error messages.
5127
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]5128.SH XI. Changes to Libpng from version 1.4.x to 1.5.x
Glenn Randers-Pehrson5b40b012010-11-25 07:16:29 -0600[diff] [blame]5129
Glenn Randers-Pehrsonc36bb792011-02-12 09:49:07 -0600[diff] [blame]5130From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the
Glenn Randers-Pehrson5b40b012010-11-25 07:16:29 -0600[diff] [blame]5131function) incorrectly returned a value of type png_uint_32.
Glenn Randers-Pehrson41633d32014-01-10 08:12:26 -0600[diff] [blame]5132The incorrect macro was removed from libpng-1.4.5.
Glenn Randers-Pehrson5b40b012010-11-25 07:16:29 -0600[diff] [blame]5133
Glenn Randers-Pehrsonb6f0a642013-12-11 22:49:52 -0600[diff] [blame]5134Checking for invalid palette index on write was added at libpng
51351.5.10. If a pixel contains an invalid (out-of-range) index libpng issues
5136a benign error. This is enabled by default because this condition is an
5137error according to the PNG specification, Clause 11.3.2, but the error can
5138be ignored in each png_ptr with
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5139
5140 png_set_check_for_invalid_index(png_ptr, allowed);
5141
5142 allowed - one of
5143 0: disable benign error (accept the
5144 invalid data without warning).
5145 1: enable benign error (treat the
5146 invalid data as an error or a
5147 warning).
5148
5149If the error is ignored, or if png_benign_error() treats it as a warning,
5150any invalid pixels are decoded as opaque black by the decoder and written
5151as-is by the encoder.
5152
5153Retrieving the maximum palette index found was added at libpng-1.5.15.
5154This statement must appear after png_read_png() or png_read_image() while
5155reading, and after png_write_png() or png_write_image() while writing.
5156
5157 int max_palette = png_get_palette_max(png_ptr, info_ptr);
5158
Glenn Randers-Pehrson4dcbf242013-08-06 17:20:06 -0500[diff] [blame]5159This will return the maximum palette index found in the image, or "\-1" if
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5160the palette was not checked, or "0" if no palette was found. Note that this
5161does not account for any palette index used by ancillary chunks such as the
5162bKGD chunk; you must check those separately to determine the maximum
5163palette index actually used.
5164
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5165A. Changes that affect users of libpng
5166
5167There are no substantial API changes between the non-deprecated parts of
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5168the 1.4.5 API and the 1.5.0 API; however, the ability to directly access
Glenn Randers-Pehrson5a956a72011-12-22 14:23:37 -0600[diff] [blame]5169members of the main libpng control structures, png_struct and png_info,
5170deprecated in earlier versions of libpng, has been completely removed from
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5171libpng 1.5.
5172
Glenn Randers-Pehrson5a956a72011-12-22 14:23:37 -0600[diff] [blame]5173We no longer include zlib.h in png.h. The include statement has been moved
5174to pngstruct.h, where it is not accessible by applications. Applications that
5175need access to information in zlib.h will need to add the '#include "zlib.h"'
5176directive. It does not matter whether this is placed prior to or after
Glenn Randers-Pehrson00879b12011-01-15 19:25:34 -0600[diff] [blame]5177the '"#include png.h"' directive.
5178
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5179The png_sprintf(), png_strcpy(), and png_strncpy() macros are no longer used
5180and were removed.
5181
5182We moved the png_strlen(), png_memcpy(), png_memset(), and png_memcmp()
5183macros into a private header file (pngpriv.h) that is not accessible to
5184applications.
Glenn Randers-Pehrson00879b12011-01-15 19:25:34 -0600[diff] [blame]5185
Glenn Randers-Pehrson9d23b402011-01-08 10:42:01 -0600[diff] [blame]5186In png_get_iCCP, the type of "profile" was changed from png_charpp
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]5187to png_bytepp, and in png_set_iCCP, from png_charp to png_const_bytep.
Glenn Randers-Pehrson9d23b402011-01-08 10:42:01 -0600[diff] [blame]5188
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5189There are changes of form in png.h, including new and changed macros to
Glenn Randers-Pehrson95ba4172011-09-08 12:21:42 -0500[diff] [blame]5190declare parts of the API. Some API functions with arguments that are
5191pointers to data not modified within the function have been corrected to
5192declare these arguments with PNG_CONST.
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5193
5194Much of the internal use of C macros to control the library build has also
5195changed and some of this is visible in the exported header files, in
5196particular the use of macros to control data and API elements visible
5197during application compilation may require significant revision to
5198application code. (It is extremely rare for an application to do this.)
5199
5200Any program that compiled against libpng 1.4 and did not use deprecated
5201features or access internal library structures should compile and work
Glenn Randers-Pehrsond08b6bd2011-02-19 15:50:17 -0600[diff] [blame]5202against libpng 1.5, except for the change in the prototype for
5203png_get_iCCP() and png_set_iCCP() API functions mentioned above.
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5204
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]5205libpng 1.5.0 adds PNG_ PASS macros to help in the reading and writing of
5206interlaced images. The macros return the number of rows and columns in
5207each pass and information that can be used to de-interlace and (if
5208absolutely necessary) interlace an image.
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5209
5210libpng 1.5.0 adds an API png_longjmp(png_ptr, value). This API calls
Glenn Randers-Pehrsond08b6bd2011-02-19 15:50:17 -0600[diff] [blame]5211the application-provided png_longjmp_ptr on the internal, but application
Glenn Randers-Pehrson33ced442011-04-27 14:58:06 -0500[diff] [blame]5212initialized, longjmp buffer. It is provided as a convenience to avoid
5213the need to use the png_jmpbuf macro, which had the unnecessary side
5214effect of resetting the internal png_longjmp_ptr value.
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5215
5216libpng 1.5.0 includes a complete fixed point API. By default this is
5217present along with the corresponding floating point API. In general the
5218fixed point API is faster and smaller than the floating point one because
5219the PNG file format used fixed point, not floating point. This applies
5220even if the library uses floating point in internal calculations. A new
5221macro, PNG_FLOATING_ARITHMETIC_SUPPORTED, reveals whether the library
5222uses floating point arithmetic (the default) or fixed point arithmetic
5223internally for performance critical calculations such as gamma correction.
Glenn Randers-Pehrson00879b12011-01-15 19:25:34 -0600[diff] [blame]5224In some cases, the gamma calculations may produce slightly different
5225results. This has changed the results in png_rgb_to_gray and in alpha
5226composition (png_set_background for example). This applies even if the
5227original image was already linear (gamma == 1.0) and, therefore, it is
5228not necessary to linearize the image. This is because libpng has *not*
5229been changed to optimize that case correctly, yet.
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5230
5231Fixed point support for the sCAL chunk comes with an important caveat;
5232the sCAL specification uses a decimal encoding of floating point values
5233and the accuracy of PNG fixed point values is insufficient for
5234representation of these values. Consequently a "string" API
5235(png_get_sCAL_s and png_set_sCAL_s) is the only reliable way of reading
5236arbitrary sCAL chunks in the absence of either the floating point API or
Glenn Randers-Pehrson759c9032014-02-01 20:11:48 -0600[diff] [blame^]5237internal floating point calculations. Starting with libpng-1.5.0, both
5238of these functions are present when PNG_sCAL_SUPPORTED is defined. Prior
5239to libpng-1.5.0, their presence also depended upon PNG_FIXED_POINT_SUPPORTED
5240being defined and PNG_FLOATING_POINT_SUPPORTED not being defined.
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5241
5242Applications no longer need to include the optional distribution header
5243file pngusr.h or define the corresponding macros during application
5244build in order to see the correct variant of the libpng API. From 1.5.0
5245application code can check for the corresponding _SUPPORTED macro:
5246
5247#ifdef PNG_INCH_CONVERSIONS_SUPPORTED
5248 /* code that uses the inch conversion APIs. */
5249#endif
5250
5251This macro will only be defined if the inch conversion functions have been
5252compiled into libpng. The full set of macros, and whether or not support
5253has been compiled in, are available in the header file pnglibconf.h.
5254This header file is specific to the libpng build. Notice that prior to
52551.5.0 the _SUPPORTED macros would always have the default definition unless
5256reset by pngusr.h or by explicit settings on the compiler command line.
5257These settings may produce compiler warnings or errors in 1.5.0 because
5258of macro redefinition.
5259
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5260Applications can now choose whether to use these macros or to call the
5261corresponding function by defining PNG_USE_READ_MACROS or
5262PNG_NO_USE_READ_MACROS before including png.h. Notice that this is
Glenn Randers-Pehrson52083f92013-08-17 15:44:37 -0500[diff] [blame]5263only supported from 1.5.0; defining PNG_NO_USE_READ_MACROS prior to 1.5.0
Glenn Randers-Pehrson95ba4172011-09-08 12:21:42 -0500[diff] [blame]5264will lead to a link failure.
Glenn Randers-Pehrson59fa3e92011-01-06 07:07:06 -0600[diff] [blame]5265
Glenn Randers-Pehrson733b1312011-06-15 13:21:01 -0500[diff] [blame]5266Prior to libpng-1.5.4, the zlib compressor used the same set of parameters
Glenn Randers-Pehrson8eb88332011-04-01 00:16:50 -0500[diff] [blame]5267when compressing the IDAT data and textual data such as zTXt and iCCP.
Glenn Randers-Pehrson733b1312011-06-15 13:21:01 -0500[diff] [blame]5268In libpng-1.5.4 we reinitialized the zlib stream for each type of data.
Glenn Randers-Pehrson8eb88332011-04-01 00:16:50 -0500[diff] [blame]5269We added five png_set_text_*() functions for setting the parameters to
5270use with textual data.
5271
Glenn Randers-Pehrson733b1312011-06-15 13:21:01 -0500[diff] [blame]5272Prior to libpng-1.5.4, the PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
John Bowlerb2bee332011-06-10 23:24:58 -0500[diff] [blame]5273option was off by default, and slightly inaccurate scaling occurred.
Glenn Randers-Pehrsonfb29e512011-06-17 20:38:24 -0500[diff] [blame]5274This option can no longer be turned off, and the choice of accurate
5275or inaccurate 16-to-8 scaling is by using the new png_set_scale_16_to_8()
5276API for accurate scaling or the old png_set_strip_16_to_8() API for simple
Glenn Randers-Pehrson41633d32014-01-10 08:12:26 -0600[diff] [blame]5277chopping. In libpng-1.5.4, the PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
5278macro became PNG_READ_SCALE_16_TO_8_SUPPORTED, and the PNG_READ_16_TO_8
5279macro became PNG_READ_STRIP_16_TO_8_SUPPORTED, to enable the two
5280png_set_*_16_to_8() functions separately.
Glenn Randers-Pehrson0cb906d2011-06-11 14:22:22 -0500[diff] [blame]5281
Glenn Randers-Pehrson733b1312011-06-15 13:21:01 -0500[diff] [blame]5282Prior to libpng-1.5.4, the png_set_user_limits() function could only be
Glenn Randers-Pehrson0cb906d2011-06-11 14:22:22 -0500[diff] [blame]5283used to reduce the width and height limits from the value of
5284PNG_USER_WIDTH_MAX and PNG_USER_HEIGHT_MAX, although this document said
5285that it could be used to override them. Now this function will reduce or
5286increase the limits.
John Bowlerb2bee332011-06-10 23:24:58 -0500[diff] [blame]5287
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5288Starting in libpng-1.5.10, the user limits can be set en masse with the
5289configuration option PNG_SAFE_LIMITS_SUPPORTED. If this option is enabled,
5290a set of "safe" limits is applied in pngpriv.h. These can be overridden by
5291application calls to png_set_user_limits(), png_set_user_chunk_cache_max(),
5292and/or png_set_user_malloc_max() that increase or decrease the limits. Also,
5293in libpng-1.5.10 the default width and height limits were increased
5294from 1,000,000 to 0x7ffffff (i.e., made unlimited). Therefore, the
5295limits are now
5296 default safe
5297 png_user_width_max 0x7fffffff 1,000,000
5298 png_user_height_max 0x7fffffff 1,000,000
5299 png_user_chunk_cache_max 0 (unlimited) 128
5300 png_user_chunk_malloc_max 0 (unlimited) 8,000,000
5301
Glenn Randers-Pehrson52083f92013-08-17 15:44:37 -0500[diff] [blame]5302The png_set_option() function (and the "options" member of the png struct) was
5303added to libpng-1.5.15.
5304
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5305B. Changes to the build and configuration of libpng
5306
5307Details of internal changes to the library code can be found in the CHANGES
Glenn Randers-Pehrsona5e55472011-07-12 10:13:32 -0500[diff] [blame]5308file and in the GIT repository logs. These will be of no concern to the vast
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5309majority of library users or builders; however, the few who configure libpng
Glenn Randers-Pehrsona5e55472011-07-12 10:13:32 -0500[diff] [blame]5310to a non-default feature set may need to change how this is done.
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5311
5312There should be no need for library builders to alter build scripts if
5313these use the distributed build support - configure or the makefiles -
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5314however, users of the makefiles may care to update their build scripts
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5315to build pnglibconf.h where the corresponding makefile does not do so.
5316
5317Building libpng with a non-default configuration has changed completely.
5318The old method using pngusr.h should still work correctly even though the
Glenn Randers-Pehrsona5e55472011-07-12 10:13:32 -0500[diff] [blame]5319way pngusr.h is used in the build has been changed; however, library
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5320builders will probably want to examine the changes to take advantage of
5321new capabilities and to simplify their build system.
5322
5323B.1 Specific changes to library configuration capabilities
5324
5325The library now supports a complete fixed point implementation and can
Glenn Randers-Pehrsona5e55472011-07-12 10:13:32 -0500[diff] [blame]5326thus be used on systems that have no floating point support or very
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5327limited or slow support. Previously gamma correction, an essential part
5328of complete PNG support, required reasonably fast floating point.
5329
5330As part of this the choice of internal implementation has been made
5331independent of the choice of fixed versus floating point APIs and all the
5332missing fixed point APIs have been implemented.
5333
5334The exact mechanism used to control attributes of API functions has
5335changed. A single set of operating system independent macro definitions
5336is used and operating system specific directives are defined in
5337pnglibconf.h
5338
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]5339As part of this the mechanism used to choose procedure call standards on
5340those systems that allow a choice has been changed. At present this only
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5341affects certain Microsoft (DOS, Windows) and IBM (OS/2) operating systems
Glenn Randers-Pehrsona5e55472011-07-12 10:13:32 -0500[diff] [blame]5342running on Intel processors. As before, PNGAPI is defined where required
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5343to control the exported API functions; however, two new macros, PNGCBAPI
5344and PNGCAPI, are used instead for callback functions (PNGCBAPI) and
5345(PNGCAPI) for functions that must match a C library prototype (currently
5346only png_longjmp_ptr, which must match the C longjmp function.) The new
5347approach is documented in pngconf.h
5348
Glenn Randers-Pehrsona5e55472011-07-12 10:13:32 -0500[diff] [blame]5349Despite these changes, libpng 1.5.0 only supports the native C function
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5350calling standard on those platforms tested so far (__cdecl on Microsoft
5351Windows). This is because the support requirements for alternative
5352calling conventions seem to no longer exist. Developers who find it
5353necessary to set PNG_API_RULE to 1 should advise the mailing list
5354(png-mng-implement) of this and library builders who use Openwatcom and
5355therefore set PNG_API_RULE to 2 should also contact the mailing list.
5356
5357A new test program, pngvalid, is provided in addition to pngtest.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]5358pngvalid validates the arithmetic accuracy of the gamma correction
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5359calculations and includes a number of validations of the file format.
5360A subset of the full range of tests is run when "make check" is done
5361(in the 'configure' build.) pngvalid also allows total allocated memory
5362usage to be evaluated and performs additional memory overwrite validation.
5363
5364Many changes to individual feature macros have been made. The following
5365are the changes most likely to be noticed by library builders who
5366configure libpng:
5367
53681) All feature macros now have consistent naming:
5369
5370#define PNG_NO_feature turns the feature off
5371#define PNG_feature_SUPPORTED turns the feature on
5372
5373pnglibconf.h contains one line for each feature macro which is either:
5374
5375#define PNG_feature_SUPPORTED
5376
5377if the feature is supported or:
5378
5379/*#undef PNG_feature_SUPPORTED*/
5380
5381if it is not. Library code consistently checks for the 'SUPPORTED' macro.
Glenn Randers-Pehrsond0797f52011-07-12 10:28:02 -0500[diff] [blame]5382It does not, and libpng applications should not, check for the 'NO' macro
5383which will not normally be defined even if the feature is not supported.
5384The 'NO' macros are only used internally for setting or not setting the
5385corresponding 'SUPPORTED' macros.
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5386
5387Compatibility with the old names is provided as follows:
5388
5389PNG_INCH_CONVERSIONS turns on PNG_INCH_CONVERSIONS_SUPPORTED
5390
5391And the following definitions disable the corresponding feature:
5392
5393PNG_SETJMP_NOT_SUPPORTED disables SETJMP
5394PNG_READ_TRANSFORMS_NOT_SUPPORTED disables READ_TRANSFORMS
5395PNG_NO_READ_COMPOSITED_NODIV disables READ_COMPOSITE_NODIV
5396PNG_WRITE_TRANSFORMS_NOT_SUPPORTED disables WRITE_TRANSFORMS
5397PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED disables READ_ANCILLARY_CHUNKS
5398PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED disables WRITE_ANCILLARY_CHUNKS
5399
5400Library builders should remove use of the above, inconsistent, names.
5401
54022) Warning and error message formatting was previously conditional on
5403the STDIO feature. The library has been changed to use the
5404CONSOLE_IO feature instead. This means that if CONSOLE_IO is disabled
5405the library no longer uses the printf(3) functions, even though the
5406default read/write implementations use (FILE) style stdio.h functions.
5407
54083) Three feature macros now control the fixed/floating point decisions:
5409
5410PNG_FLOATING_POINT_SUPPORTED enables the floating point APIs
5411
5412PNG_FIXED_POINT_SUPPORTED enables the fixed point APIs; however, in
5413practice these are normally required internally anyway (because the PNG
5414file format is fixed point), therefore in most cases PNG_NO_FIXED_POINT
5415merely stops the function from being exported.
5416
5417PNG_FLOATING_ARITHMETIC_SUPPORTED chooses between the internal floating
5418point implementation or the fixed point one. Typically the fixed point
5419implementation is larger and slower than the floating point implementation
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5420on a system that supports floating point; however, it may be faster on a
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5421system which lacks floating point hardware and therefore uses a software
5422emulation.
5423
54244) Added PNG_{READ,WRITE}_INT_FUNCTIONS_SUPPORTED. This allows the
5425functions to read and write ints to be disabled independently of
5426PNG_USE_READ_MACROS, which allows libpng to be built with the functions
5427even though the default is to use the macros - this allows applications
5428to choose at app buildtime whether or not to use macros (previously
5429impossible because the functions weren't in the default build.)
5430
5431B.2 Changes to the configuration mechanism
5432
5433Prior to libpng-1.5.0 library builders who needed to configure libpng
5434had either to modify the exported pngconf.h header file to add system
5435specific configuration or had to write feature selection macros into
5436pngusr.h and cause this to be included into pngconf.h by defining
5437PNG_USER_CONFIG. The latter mechanism had the disadvantage that an
5438application built without PNG_USER_CONFIG defined would see the
5439unmodified, default, libpng API and thus would probably fail to link.
5440
5441These mechanisms still work in the configure build and in any makefile
Glenn Randers-Pehrsona5e55472011-07-12 10:13:32 -0500[diff] [blame]5442build that builds pnglibconf.h, although the feature selection macros
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]5443have changed somewhat as described above. In 1.5.0, however, pngusr.h is
5444processed only once, when the exported header file pnglibconf.h is built.
Glenn Randers-Pehrsona5e55472011-07-12 10:13:32 -0500[diff] [blame]5445pngconf.h no longer includes pngusr.h, therefore pngusr.h is ignored after the
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5446build of pnglibconf.h and it is never included in an application build.
5447
5448The rarely used alternative of adding a list of feature macros to the
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5449CFLAGS setting in the build also still works; however, the macros will be
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5450copied to pnglibconf.h and this may produce macro redefinition warnings
5451when the individual C files are compiled.
5452
5453All configuration now only works if pnglibconf.h is built from
5454scripts/pnglibconf.dfa. This requires the program awk. Brian Kernighan
5455(the original author of awk) maintains C source code of that awk and this
5456and all known later implementations (often called by subtly different
5457names - nawk and gawk for example) are adequate to build pnglibconf.h.
5458The Sun Microsystems (now Oracle) program 'awk' is an earlier version
Glenn Randers-Pehrsona5e55472011-07-12 10:13:32 -0500[diff] [blame]5459and does not work; this may also apply to other systems that have a
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5460functioning awk called 'nawk'.
5461
5462Configuration options are now documented in scripts/pnglibconf.dfa. This
5463file also includes dependency information that ensures a configuration is
5464consistent; that is, if a feature is switched off dependent features are
5465also removed. As a recommended alternative to using feature macros in
5466pngusr.h a system builder may also define equivalent options in pngusr.dfa
5467(or, indeed, any file) and add that to the configuration by setting
5468DFA_XTRA to the file name. The makefiles in contrib/pngminim illustrate
5469how to do this, and a case where pngusr.h is still required.
5470
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]5471.SH XII. Changes to Libpng from version 1.5.x to 1.6.x
5472
5473A "simplified API" has been added (see documentation in png.h and a simple
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5474example in contrib/examples/pngtopng.c). The new publicly visible API
5475includes the following:
5476
5477 macros:
5478 PNG_FORMAT_*
5479 PNG_IMAGE_*
5480 structures:
5481 png_control
5482 png_image
5483 read functions
5484 png_image_begin_read_from_file()
5485 png_image_begin_read_from_stdio()
5486 png_image_begin_read_from_memory()
5487 png_image_finish_read()
5488 png_image_free()
5489 write functions
5490 png_image_write_to_file()
5491 png_image_write_to_stdio()
5492
5493Starting with libpng-1.6.0, you can configure libpng to prefix all exported
5494symbols, using the PNG_PREFIX macro.
Glenn Randers-Pehrson5bffd6c2012-01-31 22:21:32 -0600[diff] [blame]5495
Glenn Randers-Pehrson5a956a72011-12-22 14:23:37 -0600[diff] [blame]5496We no longer include string.h in png.h. The include statement has been moved
5497to pngpriv.h, where it is not accessible by applications. Applications that
Glenn Randers-Pehrson49f9c242013-04-27 18:03:03 -0500[diff] [blame]5498need access to information in string.h must add an '#include <string.h>'
Glenn Randers-Pehrson5a956a72011-12-22 14:23:37 -0600[diff] [blame]5499directive. It does not matter whether this is placed prior to or after
Glenn Randers-Pehrson61946e02013-04-28 20:48:37 -0500[diff] [blame]5500the '#include "png.h"' directive.
Glenn Randers-Pehrson5a956a72011-12-22 14:23:37 -0600[diff] [blame]5501
5502The following API are now DEPRECATED:
5503 png_info_init_3()
5504 png_convert_to_rfc1123() which has been replaced
5505 with png_convert_to_rfc1123_buffer()
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5506 png_data_freer()
Glenn Randers-Pehrson5a956a72011-12-22 14:23:37 -0600[diff] [blame]5507 png_malloc_default()
5508 png_free_default()
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5509 png_reset_zstream()
Glenn Randers-Pehrson5a956a72011-12-22 14:23:37 -0600[diff] [blame]5510
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5511The following have been removed:
Glenn Randers-Pehrson5a956a72011-12-22 14:23:37 -0600[diff] [blame]5512 png_get_io_chunk_name(), which has been replaced
5513 with png_get_io_chunk_type(). The new
5514 function returns a 32-bit integer instead of
5515 a string.
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5516 The png_sizeof(), png_strlen(), png_memcpy(), png_memcmp(), and
5517 png_memset() macros are no longer used in the libpng sources and
5518 have been removed. These had already been made invisible to applications
5519 (i.e., defined in the private pngpriv.h header file) since libpng-1.5.0.
5520
5521The signatures of many exported functions were changed, such that
5522 png_structp became png_structrp or png_const_structrp
5523 png_infop became png_inforp or png_const_inforp
5524where "rp" indicates a "restricted pointer".
5525
5526Error detection in some chunks has improved; in particular the iCCP chunk
5527reader now does pretty complete validation of the basic format. Some bad
Glenn Randers-Pehrsone9a8fb82013-10-26 11:29:36 -0500[diff] [blame]5528profiles that were previously accepted are now accepted with a warning or
5529rejected, depending upon the png_set_benign_errors() setting, in particular the
5530very old broken Microsoft/HP 3144-byte sRGB profile. The PNG spec requirement
5531that only grayscale profiles may appear in images with color type 0 or 4 and
5532that even if the image only contains gray pixels, only RGB profiles may appear
Glenn Randers-Pehrson2e0c5f02013-03-31 22:55:55 -0500[diff] [blame]5533in images with color type 2, 3, or 6, is now enforced. The sRGB chunk
5534is allowed to appear in images with any color type.
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5535
Glenn Randers-Pehrson2b87a542013-07-14 18:34:13 -0500[diff] [blame]5536Prior to libpng-1.6.0 a warning would be issued if the iTXt chunk contained
5537an empty language field or an empty translated keyword. Both of these
5538are allowed by the PNG specification, so these warnings are no longer issued.
5539
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5540The library now issues an error if the application attempts to set a
Glenn Randers-Pehrsone9a8fb82013-10-26 11:29:36 -0500[diff] [blame]5541transform after it calls png_read_update_info() or if it attempts to call
5542both png_read_update_info() and png_start_read_image() or to call either
5543of them more than once.
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5544
Glenn Randers-Pehrsond5dd93f2013-07-02 09:20:36 -0500[diff] [blame]5545The default condition for benign_errors is now to treat benign errors as
5546warnings while reading and as errors while writing.
5547
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5548The library now issues a warning if both background processing and RGB to
5549gray are used when gamma correction happens. As with previous versions of
5550the library the results are numerically very incorrect in this case.
5551
5552There are some minor arithmetic changes in some transforms such as
5553png_set_background(), that might be detected by certain regression tests.
5554
5555Unknown chunk handling has been improved internally, without any API change.
5556This adds more correct option control of the unknown handling, corrects
5557a pre-existing bug where the per-chunk 'keep' setting is ignored, and makes
5558it possible to skip IDAT chunks in the sequential reader.
5559
5560The machine-generated configure files are no longer included in branches
5561libpng16 and later of the GIT repository. They continue to be included
5562in the tarball releases, however.
Glenn Randers-Pehrson80647772013-02-04 19:50:56 -0600[diff] [blame]5563
Glenn Randers-Pehrson30145f22013-11-24 13:33:07 -0600[diff] [blame]5564Libpng-1.6.0 through 1.6.2 used the CMF bytes at the beginning of the IDAT
5565stream to set the size of the sliding window for reading instead of using the
5566default 32-kbyte sliding window size. It was discovered that there are
5567hundreds of PNG files in the wild that have incorrect CMF bytes that caused
5568libpng to issue a "too far back" error and reject the file. Libpng-1.6.3 and
5569later calculate their own safe CMF from the image dimensions, provide a way
5570to revert to the libpng-1.5.x behavior (ignoring the CMF bytes and using a
Glenn Randers-Pehrson52083f92013-08-17 15:44:37 -0500[diff] [blame]557132-kbyte sliding window), by using
5572
5573 png_set_option(png_ptr, PNG_MAXIMUM_INFLATE_WINDOW,
5574 PNG_OPTION_ON);
5575
Glenn Randers-Pehrson30145f22013-11-24 13:33:07 -0600[diff] [blame]5576and provide a tool (contrib/tools/pngfix) for optimizing the CMF bytes
Glenn Randers-Pehrson4cf24652013-05-08 22:04:02 -0500[diff] [blame]5577correctly.
Glenn Randers-Pehrsonff141eb2013-05-08 19:46:10 -0500[diff] [blame]5578
5579Libpng-1.6.0 and libpng-1.6.1 wrote uncompressed iTXt chunks with the wrong
5580length, which resulted in PNG files that cannot be read beyond the bad iTXt
5581chunk. This error was fixed in libpng-1.6.3, and a tool (called
5582contrib/tools/png-fix-itxt) has been added to the libpng distribution.
5583
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]5584.SH XIII. Detecting libpng
Glenn Randers-Pehrson424c9852009-06-02 13:45:15 -0500[diff] [blame]5585
5586The png_get_io_ptr() function has been present since libpng-0.88, has never
5587changed, and is unaffected by conditional compilation macros. It is the
5588best choice for use in configure scripts for detecting the presence of any
Glenn Randers-Pehrson99708d52009-06-29 17:30:00 -0500[diff] [blame]5589libpng version since 0.88. In an autoconf "configure.in" you could use
5590
5591 AC_CHECK_LIB(png, png_get_io_ptr, ...
Glenn Randers-Pehrson424c9852009-06-02 13:45:15 -0500[diff] [blame]5592
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]5593.SH XV. Source code repository
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5594
5595Since about February 2009, version 1.2.34, libpng has been under "git" source
5596control. The git repository was built from old libpng-x.y.z.tar.gz files
5597going back to version 0.70. You can access the git repository (read only)
5598at
5599
Glenn Randers-Pehrsone2d8e112013-04-11 18:53:51 -0500[diff] [blame]5600 git://git.code.sf.net/p/libpng/code
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5601
Glenn Randers-Pehrsone2d8e112013-04-11 18:53:51 -0500[diff] [blame]5602or you can browse it with a web browser by selecting the "code" button at
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5603
Glenn Randers-Pehrsone2d8e112013-04-11 18:53:51 -0500[diff] [blame]5604 https://sourceforge.net/projects/libpng
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5605
5606Patches can be sent to glennrp at users.sourceforge.net or to
5607png-mng-implement at lists.sourceforge.net or you can upload them to
5608the libpng bug tracker at
5609
5610 http://libpng.sourceforge.net
5611
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]5612We also accept patches built from the tar or zip distributions, and
5613simple verbal discriptions of bug fixes, reported either to the
Glenn Randers-Pehrsona5e55472011-07-12 10:13:32 -0500[diff] [blame]5614SourceForge bug tracker, to the png-mng-implement at lists.sf.net
5615mailing list, or directly to glennrp.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]5616
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]5617.SH XV. Coding style
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5618
5619Our coding style is similar to the "Allman" style, with curly
5620braces on separate lines:
5621
5622 if (condition)
5623 {
5624 action;
5625 }
5626
5627 else if (another condition)
5628 {
5629 another action;
5630 }
5631
5632The braces can be omitted from simple one-line actions:
5633
5634 if (condition)
5635 return (0);
5636
5637We use 3-space indentation, except for continued statements which
5638are usually indented the same as the first line of the statement
5639plus four more spaces.
5640
Glenn Randers-Pehrson5ade7ed2009-09-30 15:11:49 -0500[diff] [blame]5641For macro definitions we use 2-space indentation, always leaving the "#"
5642in the first column.
5643
5644 #ifndef PNG_NO_FEATURE
5645 # ifndef PNG_FEATURE_SUPPORTED
5646 # define PNG_FEATURE_SUPPORTED
5647 # endif
5648 #endif
5649
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5650Comments appear with the leading "/*" at the same indentation as
5651the statement that follows the comment:
5652
5653 /* Single-line comment */
5654 statement;
5655
Glenn Randers-Pehrsone4c706a2010-03-06 14:51:54 -0600[diff] [blame]5656 /* This is a multiple-line
5657 * comment.
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5658 */
5659 statement;
5660
Glenn Randers-Pehrsone4c706a2010-03-06 14:51:54 -0600[diff] [blame]5661Very short comments can be placed after the end of the statement
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5662to which they pertain:
5663
5664 statement; /* comment */
5665
5666We don't use C++ style ("//") comments. We have, however,
5667used them in the past in some now-abandoned MMX assembler
5668code.
5669
Glenn Randers-Pehrsonb5444a12009-06-08 08:36:19 -0500[diff] [blame]5670Functions and their curly braces are not indented, and
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5671exported functions are marked with PNGAPI:
5672
5673 /* This is a public function that is visible to
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5674 * application programmers. It does thus-and-so.
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5675 */
5676 void PNGAPI
5677 png_exported_function(png_ptr, png_info, foo)
5678 {
5679 body;
5680 }
5681
Glenn Randers-Pehrson416976f2009-07-27 22:16:09 -0500[diff] [blame]5682The prototypes for all exported functions appear in png.h,
5683above the comment that says
5684
5685 /* Maintainer: Put new public prototypes here ... */
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5686
5687We mark all non-exported functions with "/* PRIVATE */"":
5688
5689 void /* PRIVATE */
5690 png_non_exported_function(png_ptr, png_info, foo)
5691 {
5692 body;
5693 }
5694
Glenn Randers-Pehrson416976f2009-07-27 22:16:09 -0500[diff] [blame]5695The prototypes for non-exported functions (except for those in
Glenn Randers-Pehrson5df7edb2009-10-29 23:32:44 -0500[diff] [blame]5696pngtest) appear in
5697pngpriv.h
Glenn Randers-Pehrson416976f2009-07-27 22:16:09 -0500[diff] [blame]5698above the comment that says
5699
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5700 /* Maintainer: Put new private prototypes here ^ */
5701
5702We put a space after the "sizeof" operator and we omit the
5703optional parentheses around its argument when the argument
5704is an expression, not a type name, and we always enclose the
5705sizeof operator, with its argument, in parentheses:
5706
5707 (sizeof (png_uint_32))
5708 (sizeof array)
5709
5710Prior to libpng-1.6.0 we used a "png_sizeof()" macro, formatted as
5711though it were a function.
Glenn Randers-Pehrsonece07cf2012-08-10 18:08:02 -0500[diff] [blame]5712
Glenn Randers-Pehrsoncbbe9a52011-01-29 16:12:11 -0600[diff] [blame]5713To avoid polluting the global namespace, the names of all exported
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5714functions and variables begin with "png_", and all publicly visible C
5715preprocessor macros begin with "PNG". We request that applications that
Glenn Randers-Pehrsoncbbe9a52011-01-29 16:12:11 -0600[diff] [blame]5716use libpng *not* begin any of their own symbols with either of these strings.
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5717
5718We put a space after each comma and after each semicolon
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5719in "for" statements, and we put spaces before and after each
Glenn Randers-Pehrsone4c706a2010-03-06 14:51:54 -0600[diff] [blame]5720C binary operator and after "for" or "while", and before
5721"?". We don't put a space between a typecast and the expression
5722being cast, nor do we put one between a function name and the
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5723left parenthesis that follows it:
5724
Glenn Randers-Pehrson7191f6e2013-08-13 18:54:34 -0500[diff] [blame]5725 for (i = 2; i > 0; \-\-i)
Glenn Randers-Pehrson67f3b482009-09-23 11:36:28 -0500[diff] [blame]5726 y[i] = a(x) + (int)b;
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5727
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5728We prefer #ifdef and #ifndef to #if defined() and #if !defined()
5729when there is only one macro being tested. We always use parentheses
5730with "defined".
Glenn Randers-Pehrsond60c8862009-06-15 21:56:14 -0500[diff] [blame]5731
Glenn Randers-Pehrson8db19982011-10-27 16:17:24 -0500[diff] [blame]5732We prefer to express integers that are used as bit masks in hex format,
5733with an even number of lower-case hex digits (e.g., 0x00, 0xff, 0x0100).
5734
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5735We prefer to use underscores in variable names rather than camelCase, except
5736for a few type names that we inherit from zlib.h.
5737
Glenn Randers-Pehrson67f3b482009-09-23 11:36:28 -0500[diff] [blame]5738We do not use the TAB character for indentation in the C sources.
5739
Glenn Randers-Pehrson62ca98e2009-12-20 15:14:57 -0600[diff] [blame]5740Lines do not exceed 80 characters.
5741
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]5742Other rules can be inferred by inspecting the libpng source.
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5743
Glenn Randers-Pehrson0501c1c2012-01-11 14:00:52 -0600[diff] [blame]5744.SH XVI. Y2K Compliance in libpng
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5745
Glenn Randers-Pehrson759c9032014-02-01 20:11:48 -0600[diff] [blame^]5746February 2, 2014
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5747
5748Since the PNG Development group is an ad-hoc body, we can't make
5749an official declaration.
5750
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]5751This is your unofficial assurance that libpng from version 0.71 and
Glenn Randers-Pehrson759c9032014-02-01 20:11:48 -0600[diff] [blame^]5752upward through 1.6.9rc03 are Y2K compliant. It is my belief that earlier
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]5753versions were also Y2K compliant.
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5754
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5755Libpng only has two year fields. One is a 2-byte unsigned integer
5756that will hold years up to 65535. The other, which is deprecated,
5757holds the date in text format, and will hold years up to 9999.
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5758
5759The integer is
5760 "png_uint_16 year" in png_time_struct.
5761
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5762The string is
5763 "char time_buffer[29]" in png_struct. This is no longer used
5764in libpng-1.6.x and will be removed from libpng-1.7.0.
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5765
5766There are seven time-related functions:
5767
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]5768 png_convert_to_rfc_1123() in png.c
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5769 (formerly png_convert_to_rfc_1152() in error)
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]5770 png_convert_from_struct_tm() in pngwrite.c, called
5771 in pngwrite.c
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5772 png_convert_from_time_t() in pngwrite.c
5773 png_get_tIME() in pngget.c
5774 png_handle_tIME() in pngrutil.c, called in pngread.c
5775 png_set_tIME() in pngset.c
5776 png_write_tIME() in pngwutil.c, called in pngwrite.c
5777
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]5778All appear to handle dates properly in a Y2K environment. The
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5779png_convert_from_time_t() function calls gmtime() to convert from system
5780clock time, which returns (year - 1900), which we properly convert to
5781the full 4-digit year. There is a possibility that applications using
5782libpng are not passing 4-digit years into the png_convert_to_rfc_1123()
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]5783function, or that they are incorrectly passing only a 2-digit year
5784instead of "year - 1900" into the png_convert_from_struct_tm() function,
5785but this is not under our control. The libpng documentation has always
5786stated that it works with 4-digit years, and the APIs have been
5787documented as such.
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5788
5789The tIME chunk itself is also Y2K compliant. It uses a 2-byte unsigned
5790integer to hold the year, and can hold years as large as 65535.
5791
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]5792zlib, upon which libpng depends, is also Y2K compliant. It contains
5793no date-related code.
5794
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5795
5796 Glenn Randers-Pehrson
5797 libpng maintainer
5798 PNG Development Group
5799
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5800.SH NOTE
5801
5802Note about libpng version numbers:
5803
5804Due to various miscommunications, unforeseen code incompatibilities
5805and occasional factors outside the authors' control, version numbering
5806on the library has not always been consistent and straightforward.
5807The following table summarizes matters since version 0.89c, which was
5808the first widely used release:
5809
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]5810 source png.h png.h shared-lib
5811 version string int version
5812 ------- ------ ----- ----------
5813 0.89c ("beta 3") 0.89 89 1.0.89
5814 0.90 ("beta 4") 0.90 90 0.90
5815 0.95 ("beta 5") 0.95 95 0.95
5816 0.96 ("beta 6") 0.96 96 0.96
5817 0.97b ("beta 7") 1.00.97 97 1.0.1
5818 0.97c 0.97 97 2.0.97
5819 0.98 0.98 98 2.0.98
5820 0.99 0.99 98 2.0.99
5821 0.99a-m 0.99 99 2.0.99
5822 1.00 1.00 100 2.1.0
5823 1.0.0 1.0.0 100 2.1.0
5824 1.0.0 (from here on, the 100 2.1.0
5825 1.0.1 png.h string is 10001 2.1.0
5826 1.0.1a-e identical to the 10002 from here on, the
5827 1.0.2 source version) 10002 shared library is 2.V
5828 1.0.2a-b 10003 where V is the source
5829 1.0.1 10001 code version except as
5830 1.0.1a-e 10002 2.1.0.1a-e noted.
5831 1.0.2 10002 2.1.0.2
5832 1.0.2a-b 10003 2.1.0.2a-b
5833 1.0.3 10003 2.1.0.3
5834 1.0.3a-d 10004 2.1.0.3a-d
5835 1.0.4 10004 2.1.0.4
5836 1.0.4a-f 10005 2.1.0.4a-f
5837 1.0.5 (+ 2 patches) 10005 2.1.0.5
5838 1.0.5a-d 10006 2.1.0.5a-d
5839 1.0.5e-r 10100 2.1.0.5e-r
5840 1.0.5s-v 10006 2.1.0.5s-v
5841 1.0.6 (+ 3 patches) 10006 2.1.0.6
5842 1.0.6d-g 10007 2.1.0.6d-g
5843 1.0.6h 10007 10.6h
5844 1.0.6i 10007 10.6i
5845 1.0.6j 10007 2.1.0.6j
Glenn Randers-Pehrson25467032011-01-28 11:58:40 -0600[diff] [blame]5846 1.0.7beta11-14 DLLNUM 10007 2.1.0.7beta11-14
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]5847 1.0.7beta15-18 1 10007 2.1.0.7beta15-18
5848 1.0.7rc1-2 1 10007 2.1.0.7rc1-2
5849 1.0.7 1 10007 2.1.0.7
5850 1.0.8beta1-4 1 10008 2.1.0.8beta1-4
5851 1.0.8rc1 1 10008 2.1.0.8rc1
5852 1.0.8 1 10008 2.1.0.8
5853 1.0.9beta1-6 1 10009 2.1.0.9beta1-6
5854 1.0.9rc1 1 10009 2.1.0.9rc1
5855 1.0.9beta7-10 1 10009 2.1.0.9beta7-10
5856 1.0.9rc2 1 10009 2.1.0.9rc2
5857 1.0.9 1 10009 2.1.0.9
Glenn Randers-Pehrsone1644472001-03-23 05:06:56 -0600[diff] [blame]5858 1.0.10beta1 1 10010 2.1.0.10beta1
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]5859 1.0.10rc1 1 10010 2.1.0.10rc1
Glenn Randers-Pehrson13cfbac2001-03-30 06:42:28 -0600[diff] [blame]5860 1.0.10 1 10010 2.1.0.10
Glenn Randers-Pehrsone1eff582001-04-14 20:15:41 -0500[diff] [blame]5861 1.0.11beta1-3 1 10011 2.1.0.11beta1-3
Glenn Randers-Pehrson82ae3832001-04-20 10:32:10 -0500[diff] [blame]5862 1.0.11rc1 1 10011 2.1.0.11rc1
Glenn Randers-Pehrson32835392001-04-27 08:29:32 -0500[diff] [blame]5863 1.0.11 1 10011 2.1.0.11
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame]5864 1.0.12beta1-2 2 10012 2.1.0.12beta1-2
5865 1.0.12rc1 2 10012 2.1.0.12rc1
5866 1.0.12 2 10012 2.1.0.12
5867 1.1.0a-f - 10100 2.1.1.0a-f abandoned
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]5868 1.2.0beta1-2 2 10200 2.1.2.0beta1-2
Glenn Randers-Pehrson5a0be342001-10-18 20:55:13 -0500[diff] [blame]5869 1.2.0beta3-5 3 10200 3.1.2.0beta3-5
5870 1.2.0rc1 3 10200 3.1.2.0rc1
5871 1.2.0 3 10200 3.1.2.0
Glenn Randers-Pehrson5cded0b2001-11-07 07:10:08 -0600[diff] [blame]5872 1.2.1beta-4 3 10201 3.1.2.1beta1-4
Glenn Randers-Pehrsondb3b88d2001-12-04 06:30:43 -0600[diff] [blame]5873 1.2.1rc1-2 3 10201 3.1.2.1rc1-2
5874 1.2.1 3 10201 3.1.2.1
Glenn Randers-Pehrson25228ab2002-03-31 07:33:55 -0600[diff] [blame]5875 1.2.2beta1-6 12 10202 12.so.0.1.2.2beta1-6
Glenn Randers-Pehrsonfcbd7872002-04-07 16:35:38 -0500[diff] [blame]5876 1.0.13beta1 10 10013 10.so.0.1.0.13beta1
5877 1.0.13rc1 10 10013 10.so.0.1.0.13rc1
5878 1.2.2rc1 12 10202 12.so.0.1.2.2rc1
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]5879 1.0.13 10 10013 10.so.0.1.0.13
5880 1.2.2 12 10202 12.so.0.1.2.2
Glenn Randers-Pehrson22f28962002-05-13 18:17:09 -0500[diff] [blame]5881 1.2.3rc1-6 12 10203 12.so.0.1.2.3rc1-6
5882 1.2.3 12 10203 12.so.0.1.2.3
Glenn Randers-Pehrsond020e9d2002-06-28 09:34:00 -0500[diff] [blame]5883 1.2.4beta1-3 13 10204 12.so.0.1.2.4beta1-3
Glenn Randers-Pehrson2ae022d2002-07-01 22:23:46 -0500[diff] [blame]5884 1.2.4rc1 13 10204 12.so.0.1.2.4rc1
Glenn Randers-Pehrson484a8a12002-07-07 19:15:20 -0500[diff] [blame]5885 1.0.14 10 10014 10.so.0.1.0.14
5886 1.2.4 13 10204 12.so.0.1.2.4
Glenn Randers-Pehrson5b5dcf82004-07-17 22:45:44 -0500[diff] [blame]5887 1.2.5beta1-2 13 10205 12.so.0.1.2.5beta1-2
5888 1.0.15rc1 10 10015 10.so.0.1.0.15rc1
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]5889 1.0.15 10 10015 10.so.0.1.0.15
5890 1.2.5 13 10205 12.so.0.1.2.5
5891 1.2.6beta1-4 13 10206 12.so.0.1.2.6beta1-4
Glenn Randers-Pehrson37f116a2004-08-15 07:15:39 -0500[diff] [blame]5892 1.2.6rc1-5 13 10206 12.so.0.1.2.6rc1-5
5893 1.0.16 10 10016 10.so.0.1.0.16
5894 1.2.6 13 10206 12.so.0.1.2.6
Glenn Randers-Pehrson67864af2004-08-28 23:30:07 -0500[diff] [blame]5895 1.2.7beta1-2 13 10207 12.so.0.1.2.7beta1-2
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]5896 1.0.17rc1 10 10017 12.so.0.1.0.17rc1
5897 1.2.7rc1 13 10207 12.so.0.1.2.7rc1
Glenn Randers-Pehrson250dfe12004-09-11 21:19:54 -0500[diff] [blame]5898 1.0.17 10 10017 12.so.0.1.0.17
5899 1.2.7 13 10207 12.so.0.1.2.7
Glenn Randers-Pehrson40936072004-11-20 11:18:40 -0600[diff] [blame]5900 1.2.8beta1-5 13 10208 12.so.0.1.2.8beta1-5
Glenn Randers-Pehrson584b96e2004-11-29 15:08:00 -0600[diff] [blame]5901 1.0.18rc1-5 10 10018 12.so.0.1.0.18rc1-5
5902 1.2.8rc1-5 13 10208 12.so.0.1.2.8rc1-5
Glenn Randers-Pehrson917648e2004-12-02 18:14:51 -0600[diff] [blame]5903 1.0.18 10 10018 12.so.0.1.0.18
5904 1.2.8 13 10208 12.so.0.1.2.8
Glenn Randers-Pehrsone6474622006-03-04 16:50:47 -0600[diff] [blame]5905 1.2.9beta1-3 13 10209 12.so.0.1.2.9beta1-3
Glenn Randers-Pehrson4deeb792006-03-22 16:21:59 -0600[diff] [blame]5906 1.2.9beta4-11 13 10209 12.so.0.9[.0]
Glenn Randers-Pehrson3a512032006-03-31 05:29:33 -0600[diff] [blame]5907 1.2.9rc1 13 10209 12.so.0.9[.0]
Glenn Randers-Pehrsona7d0c942006-04-14 06:22:52 -0500[diff] [blame]5908 1.2.9 13 10209 12.so.0.9[.0]
Glenn Randers-Pehrsond60b8fa2006-04-20 21:31:14 -0500[diff] [blame]5909 1.2.10beta1-7 13 10210 12.so.0.10[.0]
Glenn Randers-Pehrson17218292006-04-20 07:20:46 -0500[diff] [blame]5910 1.2.10rc1-2 13 10210 12.so.0.10[.0]
Glenn Randers-Pehrson86dc9812006-05-10 07:27:44 -0500[diff] [blame]5911 1.2.10 13 10210 12.so.0.10[.0]
Glenn Randers-Pehrson6bc53be2006-06-16 07:52:03 -0500[diff] [blame]5912 1.4.0beta1-6 14 10400 14.so.0.0[.0]
Glenn Randers-Pehrsond60c8862009-06-15 21:56:14 -0500[diff] [blame]5913 1.2.11beta1-4 13 10210 12.so.0.11[.0]
Glenn Randers-Pehrson3424ee72006-07-12 13:33:47 -0500[diff] [blame]5914 1.4.0beta7-8 14 10400 14.so.0.0[.0]
Glenn Randers-Pehrson701dbaa2006-11-17 09:36:54 -0600[diff] [blame]5915 1.2.11 13 10211 12.so.0.11[.0]
5916 1.2.12 13 10212 12.so.0.12[.0]
5917 1.4.0beta9-14 14 10400 14.so.0.0[.0]
5918 1.2.13 13 10213 12.so.0.13[.0]
Glenn Randers-Pehrson97a9b482008-10-25 20:03:28 -0500[diff] [blame]5919 1.4.0beta15-36 14 10400 14.so.0.0[.0]
Glenn Randers-Pehrsonfa028102009-10-10 06:15:21 -0500[diff] [blame]5920 1.4.0beta37-87 14 10400 14.so.14.0[.0]
Glenn Randers-Pehrson733da8c2009-10-30 00:00:15 -0500[diff] [blame]5921 1.4.0rc01 14 10400 14.so.14.0[.0]
Glenn Randers-Pehrson62ca98e2009-12-20 15:14:57 -0600[diff] [blame]5922 1.4.0beta88-109 14 10400 14.so.14.0[.0]
Glenn Randers-Pehrson67a83db2010-01-01 18:26:18 -0600[diff] [blame]5923 1.4.0rc02-08 14 10400 14.so.14.0[.0]
Glenn Randers-Pehrsondbcfb712009-12-25 14:24:18 -0600[diff] [blame]5924 1.4.0 14 10400 14.so.14.0[.0]
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]5925 1.4.1beta01-03 14 10401 14.so.14.1[.0]
5926 1.4.1rc01 14 10401 14.so.14.1[.0]
Glenn Randers-Pehrson7a5be532010-02-14 07:16:19 -0600[diff] [blame]5927 1.4.1beta04-12 14 10401 14.so.14.1[.0]
Glenn Randers-Pehrsonaaf377c2010-03-08 11:20:30 -0600[diff] [blame]5928 1.4.1 14 10401 14.so.14.1[.0]
Glenn Randers-Pehrson5b3d5542010-06-18 21:55:53 -0500[diff] [blame]5929 1.4.2 14 10402 14.so.14.2[.0]
5930 1.4.3 14 10403 14.so.14.3[.0]
Glenn Randers-Pehrson2776d5e2010-11-21 15:18:02 -0600[diff] [blame]5931 1.4.4 14 10404 14.so.14.4[.0]
Glenn Randers-Pehrsonfd20a5a2010-12-27 08:53:08 -0600[diff] [blame]5932 1.5.0beta01-58 15 10500 15.so.15.0[.0]
Glenn Randers-Pehrson64b863c2011-01-04 09:57:06 -0600[diff] [blame]5933 1.5.0rc01-07 15 10500 15.so.15.0[.0]
Glenn Randers-Pehrsonf5ea1b72011-01-06 06:42:51 -0600[diff] [blame]5934 1.5.0 15 10500 15.so.15.0[.0]
Glenn Randers-Pehrsonef123cc2011-01-28 15:20:34 -0600[diff] [blame]5935 1.5.1beta01-11 15 10501 15.so.15.1[.0]
Glenn Randers-Pehrson3d3aae12011-02-02 22:58:27 -0600[diff] [blame]5936 1.5.1rc01-02 15 10501 15.so.15.1[.0]
5937 1.5.1 15 10501 15.so.15.1[.0]
Glenn Randers-Pehrsonf3dd1cc2011-03-18 22:02:20 -0500[diff] [blame]5938 1.5.2beta01-03 15 10502 15.so.15.2[.0]
Glenn Randers-Pehrson77fd0832011-03-24 08:59:48 -0500[diff] [blame]5939 1.5.2rc01-03 15 10502 15.so.15.2[.0]
Glenn Randers-Pehrsondcc35052011-03-31 11:23:49 -0500[diff] [blame]5940 1.5.2 15 10502 15.so.15.2[.0]
Glenn Randers-Pehrson36edbb52011-06-03 07:15:04 -0500[diff] [blame]5941 1.5.3beta01-10 15 10503 15.so.15.3[.0]
Glenn Randers-Pehrsonfb278732011-06-10 20:43:39 -0500[diff] [blame]5942 1.5.3rc01-02 15 10503 15.so.15.3[.0]
Glenn Randers-Pehrson413138a2011-06-13 22:07:37 -0500[diff] [blame]5943 1.5.3beta11 15 10503 15.so.15.3[.0]
5944 1.5.3 [omitted]
Glenn Randers-Pehrson9daf91e2011-06-22 23:10:36 -0500[diff] [blame]5945 1.5.4beta01-08 15 10504 15.so.15.4[.0]
Glenn Randers-Pehrson78bb9da2011-06-30 18:59:45 -0500[diff] [blame]5946 1.5.4rc01 15 10504 15.so.15.4[.0]
Glenn Randers-Pehrsond404b6d2011-07-07 06:24:57 -0500[diff] [blame]5947 1.5.4 15 10504 15.so.15.4[.0]
Glenn Randers-Pehrson3c2ae602011-09-09 06:02:09 -0500[diff] [blame]5948 1.5.5beta01-08 15 10505 15.so.15.5[.0]
5949 1.5.5rc01 15 10505 15.so.15.5[.0]
Glenn Randers-Pehrson3e2263a2011-09-22 08:40:32 -0500[diff] [blame]5950 1.5.5 15 10505 15.so.15.5[.0]
Glenn Randers-Pehrson93254f62011-10-26 08:36:21 -0500[diff] [blame]5951 1.5.6beta01-07 15 10506 15.so.15.6[.0]
Glenn Randers-Pehrsonbc6726b2011-11-02 22:43:00 -0500[diff] [blame]5952 1.5.6rc01-03 15 10506 15.so.15.6[.0]
5953 1.5.6 15 10506 15.so.15.6[.0]
Glenn Randers-Pehrson36251d32011-11-17 21:14:34 -0600[diff] [blame]5954 1.5.7beta01-05 15 10507 15.so.15.7[.0]
Glenn Randers-Pehrsonb74fb4e2011-12-21 08:37:46 -0600[diff] [blame]5955 1.5.7rc01-03 15 10507 15.so.15.7[.0]
5956 1.5.7 15 10507 15.so.15.7[.0]
Glenn Randers-Pehrson871b1d02013-03-02 14:58:22 -0600[diff] [blame]5957 1.6.0beta01-40 16 10600 16.so.16.0[.0]
5958 1.6.0rc01-08 16 10600 16.so.16.0[.0]
5959 1.6.0 16 10600 16.so.16.0[.0]
Glenn Randers-Pehrson3a83aa32013-03-29 06:56:45 -0500[diff] [blame]5960 1.6.1beta01-09 16 10601 16.so.16.1[.0]
Glenn Randers-Pehrson4e6e2162013-03-21 07:27:01 -0500[diff] [blame]5961 1.6.1rc01 16 10601 16.so.16.1[.0]
Glenn Randers-Pehrson50878052013-03-27 20:31:36 -0500[diff] [blame]5962 1.6.1 16 10601 16.so.16.1[.0]
Glenn Randers-Pehrson0794df42013-04-18 06:23:26 -0500[diff] [blame]5963 1.6.2beta01 16 10602 16.so.16.2[.0]
Glenn Randers-Pehrson0ee34652013-04-23 22:17:03 -0500[diff] [blame]5964 1.6.2rc01-06 16 10602 16.so.16.2[.0]
Glenn Randers-Pehrson809355b2013-04-25 07:24:46 -0500[diff] [blame]5965 1.6.2 16 10602 16.so.16.2[.0]
Glenn Randers-Pehrsonb23afad2013-07-10 19:30:59 -0500[diff] [blame]5966 1.6.3beta01-11 16 10603 16.so.16.3[.0]
5967 1.6.3rc01 16 10603 16.so.16.3[.0]
Glenn Randers-Pehrson847e9ef2013-07-17 19:03:02 -0500[diff] [blame]5968 1.6.3 16 10603 16.so.16.3[.0]
Glenn Randers-Pehrsond42dc542013-09-05 15:11:27 -0500[diff] [blame]5969 1.6.4beta01-02 16 10604 16.so.16.4[.0]
5970 1.6.4rc01 16 10604 16.so.16.4[.0]
Glenn Randers-Pehrson209d3eb2013-09-11 21:28:37 -0500[diff] [blame]5971 1.6.4 16 10604 16.so.16.4[.0]
Glenn Randers-Pehrson53ae7dc2013-09-14 07:18:49 -0500[diff] [blame]5972 1.6.5 16 10605 16.so.16.5[.0]
Glenn Randers-Pehrson39145942013-09-16 10:33:47 -0500[diff] [blame]5973 1.6.6 16 10606 16.so.16.6[.0]
Glenn Randers-Pehrsond2d09e52013-11-02 15:41:20 -0500[diff] [blame]5974 1.6.7beta01-04 16 10607 16.so.16.7[.0]
Glenn Randers-Pehrson6a3805c2013-11-14 13:16:21 -0600[diff] [blame]5975 1.6.7rc01-02 16 10607 16.so.16.7[.0]
5976 1.6.7 16 10607 16.so.16.7[.0]
Glenn Randers-Pehrsonb6f0a642013-12-11 22:49:52 -0600[diff] [blame]5977 1.6.8beta01-02 16 10608 16.so.16.8[.0]
Glenn Randers-Pehrsonbe3977d2013-12-19 09:04:52 -0600[diff] [blame]5978 1.6.8rc01-02 16 10608 16.so.16.8[.0]
5979 1.6.8 16 10608 16.so.16.8[.0]
Glenn Randers-Pehrson759c9032014-02-01 20:11:48 -0600[diff] [blame^]5980 1.6.9beta01-04 16 10609 16.so.16.9[.0]
5981 1.6.9rc01-02 16 10609 16.so.16.9[.0]
5982 1.6.9 16 10609 16.so.16.9[.0]
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5983
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]5984Henceforth the source version will match the shared-library minor
5985and patch numbers; the shared-library major version number will be
5986used for changes in backward compatibility, as it is intended. The
5987PNG_PNGLIB_VER macro, which is not used within libpng but is available
5988for applications, is an unsigned integer of the form xyyzz corresponding
5989to the source version x.y.z (leading zeros in y and z). Beta versions
Glenn Randers-Pehrsone1644472001-03-23 05:06:56 -0600[diff] [blame]5990were given the previous public release number plus a letter, until
5991version 1.0.6j; from then on they were given the upcoming public
5992release number plus "betaNN" or "rcN".
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]5993
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5994.SH "SEE ALSO"
Glenn Randers-Pehrson4e763f12010-03-03 10:45:50 -0600[diff] [blame]5995.BR "png"(5), " libpngpf"(3), " zlib"(3), " deflate"(5), " " and " zlib"(5)
Glenn Randers-Pehrson7fb32a82010-03-03 09:47:49 -0600[diff] [blame]5996
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]5997.LP
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5998.IR libpng :
5999.IP
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]6000http://libpng.sourceforge.net (follow the [DOWNLOAD] link)
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]6001http://www.libpng.org/pub/png
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]6002
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]6003.LP
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]6004.IR zlib :
6005.IP
6006(generally) at the same location as
6007.I libpng
6008or at
6009.br
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]6010ftp://ftp.info-zip.org/pub/infozip/zlib
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]6011
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]6012.LP
6013.IR PNG specification: RFC 2083
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]6014.IP
6015(generally) at the same location as
6016.I libpng
6017or at
6018.br
6019ftp://ds.internic.net/rfc/rfc2083.txt
6020.br
6021or (as a W3C Recommendation) at
6022.br
6023http://www.w3.org/TR/REC-png.html
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]6024
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]6025.LP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]6026In the case of any inconsistency between the PNG specification
6027and this library, the specification takes precedence.
6028
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]6029.SH AUTHORS
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]6030This man page: Glenn Randers-Pehrson
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]6031<glennrp at users.sourceforge.net>
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]6032
6033The contributing authors would like to thank all those who helped
6034with testing, bug fixes, and patience. This wouldn't have been
6035possible without all of you.
6036
6037Thanks to Frank J. T. Wojcik for helping with the documentation.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]6038
Glenn Randers-Pehrson759c9032014-02-01 20:11:48 -0600[diff] [blame^]6039Libpng version 1.6.9rc03 - February 2, 2014:
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]6040Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]6041Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]6042
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]6043Supported by the PNG development group
6044.br
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]6045png-mng-implement at lists.sf.net
6046(subscription required; visit
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]6047png-mng-implement at lists.sourceforge.net (subscription required; visit
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]6048https://lists.sourceforge.net/lists/listinfo/png-mng-implement
6049to subscribe).
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]6050
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]6051.SH COPYRIGHT NOTICE, DISCLAIMER, and LICENSE:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]6052
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]6053(This copy of the libpng notices is provided for your convenience. In case of
6054any discrepancy between this copy and the notices in the file png.h that is
6055included in the libpng distribution, the latter shall prevail.)
6056
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]6057If you modify libpng you may insert additional notices immediately following
6058this sentence.
6059
Glenn Randers-Pehrsonbfbf8652009-06-26 21:46:52 -0500[diff] [blame]6060This code is released under the libpng license.
Glenn Randers-Pehrson037023b2009-06-24 10:27:36 -0500[diff] [blame]6061
Glenn Randers-Pehrson759c9032014-02-01 20:11:48 -0600[diff] [blame^]6062libpng versions 1.2.6, August 15, 2004, through 1.6.9rc03, February 2, 2014, are
Glenn Randers-Pehrsona7dbcba2007-05-15 16:16:34 -0500[diff] [blame]6063Copyright (c) 2004,2006-2007 Glenn Randers-Pehrson, and are
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]6064distributed according to the same disclaimer and license as libpng-1.2.5
Glenn Randers-Pehrsond029a752004-08-09 21:50:32 -0500[diff] [blame]6065with the following individual added to the list of Contributing Authors
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]6066
6067 Cosmin Truta
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]6068
6069libpng versions 1.0.7, July 1, 2000, through 1.2.5 - October 3, 2002, are
Glenn Randers-Pehrsonc6de22d2002-02-23 18:55:25 -0600[diff] [blame]6070Copyright (c) 2000-2002 Glenn Randers-Pehrson, and are
Glenn Randers-Pehrson32fc5ce2000-07-24 06:34:14 -0500[diff] [blame]6071distributed according to the same disclaimer and license as libpng-1.0.6
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]6072with the following individuals added to the list of Contributing Authors
6073
6074 Simon-Pierre Cadieux
6075 Eric S. Raymond
6076 Gilles Vollant
6077
6078and with the following additions to the disclaimer:
6079
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]6080 There is no warranty against interference with your
6081 enjoyment of the library or against infringement.
6082 There is no warranty that our efforts or the library
6083 will fulfill any of your particular purposes or needs.
6084 This library is provided with all faults, and the entire
6085 risk of satisfactory quality, performance, accuracy, and
6086 effort is with the user.
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]6087
6088libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
6089Copyright (c) 1998, 1999 Glenn Randers-Pehrson
6090Distributed according to the same disclaimer and license as libpng-0.96,
6091with the following individuals added to the list of Contributing Authors:
6092
6093 Tom Lane
6094 Glenn Randers-Pehrson
6095 Willem van Schaik
6096
6097libpng versions 0.89, June 1996, through 0.96, May 1997, are
Glenn Randers-Pehrson54a066a1999-09-19 06:04:18 -0500[diff] [blame]6098Copyright (c) 1996, 1997 Andreas Dilger
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]6099Distributed according to the same disclaimer and license as libpng-0.88,
6100with the following individuals added to the list of Contributing Authors:
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]6101
6102 John Bowler
6103 Kevin Bracey
6104 Sam Bushell
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]6105 Magnus Holmgren
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]6106 Greg Roelofs
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]6107 Tom Tanner
6108
6109libpng versions 0.5, May 1995, through 0.88, January 1996, are
6110Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
6111
6112For the purposes of this copyright and license, "Contributing Authors"
6113is defined as the following set of individuals:
6114
6115 Andreas Dilger
6116 Dave Martindale
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]6117 Guy Eric Schalnat
6118 Paul Schmidt
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]6119 Tim Wegner
Glenn Randers-Pehrsonc9442291999-01-06 21:50:16 -0600[diff] [blame]6120
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]6121The PNG Reference Library is supplied "AS IS". The Contributing Authors
6122and Group 42, Inc. disclaim all warranties, expressed or implied,
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]6123including, without limitation, the warranties of merchantability and of
6124fitness for any purpose. The Contributing Authors and Group 42, Inc.
6125assume no liability for direct, indirect, incidental, special, exemplary,
6126or consequential damages, which may result from the use of the PNG
6127Reference Library, even if advised of the possibility of such damage.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]6128
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]6129Permission is hereby granted to use, copy, modify, and distribute this
6130source code, or portions hereof, for any purpose, without fee, subject
6131to the following restrictions:
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]6132
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]61331. The origin of this source code must not be misrepresented.
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]6134
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]61352. Altered versions must be plainly marked as such and
6136 must not be misrepresented as being the original source.
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]6137
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]61383. This Copyright notice may not be removed or altered from
6139 any source or altered source distribution.
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]6140
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]6141The Contributing Authors and Group 42, Inc. specifically permit, without
6142fee, and encourage the use of this source code as a component to
6143supporting the PNG file format in commercial products. If you use this
6144source code in a product, acknowledgment is not required but would be
6145appreciated.
6146
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]6147
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]6148A "png_get_copyright" function is available, for convenient use in "about"
6149boxes and the like:
6150
6151 printf("%s",png_get_copyright(NULL));
6152
6153Also, the PNG logo (in PNG format, of course) is supplied in the
Glenn Randers-Pehrsona4d54bd2000-07-14 08:15:12 -0500[diff] [blame]6154files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31).
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]6155
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]6156Libpng is OSI Certified Open Source Software. OSI Certified Open Source is a
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]6157certification mark of the Open Source Initiative.
6158
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]6159Glenn Randers-Pehrson
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]6160glennrp at users.sourceforge.net
Glenn Randers-Pehrson759c9032014-02-01 20:11:48 -0600[diff] [blame^]6161February 2, 2014
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]6162
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]6163.\" end of man page
6164