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gerrit-public.fairphone.software / fp2-dev / platform / external / libpng / refs/tags/fp2-sibon-17.07.6 / . / libpng.3
blob: 357d0ec5a8b5be9fab99adacc58f5b21f34f931e [file] [log] [blame]
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]1.TH LIBPNG 3 "December 3, 2015"
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2.SH NAME
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]3libpng \- Portable Network Graphics (PNG) Reference Library 1.6.20
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4.SH SYNOPSIS
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5\fB
6#include <png.h>\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]7
8\fBpng_uint_32 png_access_version_number \fI(void\fP\fB);\fP
9
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]10\fBvoid png_benign_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]11
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]12\fBvoid png_build_grayscale_palette (int \fP\fIbit_depth\fP\fB, png_colorp \fIpalette\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]13
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]14\fBpng_voidp png_calloc (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP
15
16\fBvoid png_chunk_benign_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]17
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]18\fBvoid png_chunk_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP
19
20\fBvoid png_chunk_warning (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fImessage\fP\fB);\fP
21
22\fBvoid png_convert_from_struct_tm (png_timep \fP\fIptime\fP\fB, struct tm FAR * \fIttime\fP\fB);\fP
23
24\fBvoid png_convert_from_time_t (png_timep \fP\fIptime\fP\fB, time_t \fIttime\fP\fB);\fP
25
26\fBpng_charp png_convert_to_rfc1123 (png_structp \fP\fIpng_ptr\fP\fB, png_timep \fIptime\fP\fB);\fP
27
28\fBpng_infop png_create_info_struct (png_structp \fIpng_ptr\fP\fB);\fP
29
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
31
Chris Craikb50c2172013-07-29 15:28:30 -0700[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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]33
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[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
35
Chris Craikb50c2172013-07-29 15:28:30 -0700[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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]37
Chris Craikb50c2172013-07-29 15:28:30 -0700[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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]39
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]40\fBvoid png_destroy_info_struct (png_structp \fP\fIpng_ptr\fP\fB, png_infopp \fIinfo_ptr_ptr\fP\fB);\fP
41
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
44\fBvoid png_destroy_write_struct (png_structpp \fP\fIpng_ptr_ptr\fP\fB, png_infopp \fIinfo_ptr_ptr\fP\fB);\fP
45
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]46\fBvoid png_err (png_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]47
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]48\fBvoid png_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP
49
50\fBvoid png_free (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP
51
52\fBvoid png_free_chunk_list (png_structp \fIpng_ptr\fP\fB);\fP
53
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]54\fBvoid png_free_default (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]55
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[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
57
Chris Craikb50c2172013-07-29 15:28:30 -0700[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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]59
Chris Craikb50c2172013-07-29 15:28:30 -0700[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
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]61
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]62\fBpng_byte png_get_channels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]63
Chris Craikb50c2172013-07-29 15:28:30 -0700[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
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]65
Chris Craikb50c2172013-07-29 15:28:30 -0700[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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]67
Chris Craikb50c2172013-07-29 15:28:30 -0700[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
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]69
Chris Craikb50c2172013-07-29 15:28:30 -0700[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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]71
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]72\fBpng_uint_32 png_get_chunk_cache_max (png_const_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]73
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]74\fBpng_alloc_size_t png_get_chunk_malloc_max (png_const_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]75
Chris Craikb50c2172013-07-29 15:28:30 -0700[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
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]77
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]78\fBpng_uint_32 png_get_compression_buffer_size (png_const_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]79
Chris Craikb50c2172013-07-29 15:28:30 -0700[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
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]81
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]82\fBpng_byte png_get_copyright (png_const_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]83
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]84\fBpng_uint_32 png_get_current_row_number \fI(png_const_structp\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]85
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]86\fBpng_byte png_get_current_pass_number \fI(png_const_structp\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]87
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]88\fBpng_voidp png_get_error_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]89
Chris Craikb50c2172013-07-29 15:28:30 -0700[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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]91
Chris Craikb50c2172013-07-29 15:28:30 -0700[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
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]93
Chris Craikb50c2172013-07-29 15:28:30 -0700[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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]95
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]96\fBpng_byte png_get_header_ver (png_const_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]97
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]98\fBpng_byte png_get_header_version (png_const_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]99
Chris Craikb50c2172013-07-29 15:28:30 -0700[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
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]101
Chris Craikb50c2172013-07-29 15:28:30 -0700[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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]103
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[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
Chris Craikb50c2172013-07-29 15:28:30 -0700[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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]107
Chris Craikb50c2172013-07-29 15:28:30 -0700[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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]109
110\fBpng_int_32 png_get_int_32 (png_bytep \fIbuf\fP\fB);\fP
111
Chris Craikb50c2172013-07-29 15:28:30 -0700[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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]113
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]114\fBpng_uint_32 png_get_io_chunk_type (png_const_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]115
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]116\fBpng_voidp png_get_io_ptr (png_structp \fIpng_ptr\fP\fB);\fP
117
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]118\fBpng_uint_32 png_get_io_state (png_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]119
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]120\fBpng_byte png_get_libpng_ver (png_const_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]121
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]122\fBint png_get_palette_max(png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
123
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]124\fBpng_voidp png_get_mem_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]125
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]126\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
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]127
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]128\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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]129
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]130\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
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]131
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]132\fBfloat png_get_pixel_aspect_ratio (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]133
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]134\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
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]135
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]136\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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]137
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]138\fBpng_uint_32 png_get_pixels_per_inch (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]139
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]140\fBpng_uint_32 png_get_pixels_per_meter (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]141
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]142\fBpng_voidp png_get_progressive_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]143
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]144\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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]145
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]146\fBpng_byte png_get_rgb_to_gray_status (png_const_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]147
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]148\fBpng_uint_32 png_get_rowbytes (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]149
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]150\fBpng_bytepp png_get_rows (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]151
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]152\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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]153
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]154\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
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]155
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]156\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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]157
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]158\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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]159
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]160\fBpng_bytep png_get_signature (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]161
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]162\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
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]163
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]164\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
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]165
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]166\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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]167
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]168\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
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]169
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]170\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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]171
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]172\fB/* This function is really an inline macro. \fI*/
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]173
174\fBpng_uint_16 png_get_uint_16 (png_bytep \fIbuf\fP\fB);\fP
175
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]176\fBpng_uint_32 png_get_uint_31 (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIbuf\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]177
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]178\fB/* This function is really an inline macro. \fI*/
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]179
180\fBpng_uint_32 png_get_uint_32 (png_bytep \fIbuf\fP\fB);\fP
181
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]182\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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]183
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]184\fBpng_voidp png_get_user_chunk_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]185
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]186\fBpng_uint_32 png_get_user_height_max (png_const_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]187
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]188\fBpng_voidp png_get_user_transform_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]189
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]190\fBpng_uint_32 png_get_user_width_max (png_const_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]191
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]192\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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]193
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]194\fBfloat png_get_x_offset_inches (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]195
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]196\fBpng_fixed_point png_get_x_offset_inches_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]197
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]198\fBpng_int_32 png_get_x_offset_microns (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]199
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]200\fBpng_int_32 png_get_x_offset_pixels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]201
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]202\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
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]203
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]204\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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]205
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]206\fBfloat png_get_y_offset_inches (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]207
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]208\fBpng_fixed_point png_get_y_offset_inches_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]209
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]210\fBpng_int_32 png_get_y_offset_microns (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]211
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]212\fBpng_int_32 png_get_y_offset_pixels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]213
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]214\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
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]215
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]216\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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]217
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]218\fBint png_handle_as_unknown (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIchunk_name\fP\fB);\fP
219
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]220\fBint png_image_begin_read_from_file (png_imagep \fP\fIimage\fP\fB, const char \fI*file_name\fP\fB);\fP
221
222\fBint png_image_begin_read_from_stdio (png_imagep \fP\fIimage\fP\fB, FILE* \fIfile\fP\fB);\fP
223
224\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
225
226\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
227
228\fBvoid png_image_free (png_imagep \fIimage\fP\fB);\fP
229
230\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
231
232\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
233
234\fBvoid png_info_init_3 (png_infopp \fP\fIinfo_ptr\fP\fB, png_size_t \fIpng_info_struct_size\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]235
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]236\fBvoid png_init_io (png_structp \fP\fIpng_ptr\fP\fB, FILE \fI*fp\fP\fB);\fP
237
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]238\fBvoid png_longjmp (png_structp \fP\fIpng_ptr\fP\fB, int \fIval\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]239
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]240\fBpng_voidp png_malloc (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]241
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]242\fBpng_voidp png_malloc_default (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]243
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]244\fBpng_voidp png_malloc_warn (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]245
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]246\fBpng_uint_32 png_permit_mng_features (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fImng_features_permitted\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]247
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]248\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
249
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]250\fBpng_size_t png_process_data_pause \fP\fI(png_structp\fP\fB, int \fIsave\fP\fB);\fP
251
252\fBpng_uint_32 png_process_data_skip \fI(png_structp\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]253
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]254\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
255
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]256\fBvoid png_read_end (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
257
258\fBvoid png_read_image (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fIimage\fP\fB);\fP
259
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]260\fBvoid png_read_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
261
262\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
263
264\fBvoid png_read_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIrow\fP\fB, png_bytep \fIdisplay_row\fP\fB);\fP
265
266\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
267
268\fBvoid png_read_update_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
269
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]270\fBint png_reset_zstream (png_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]271
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]272\fBvoid png_save_int_32 (png_bytep \fP\fIbuf\fP\fB, png_int_32 \fIi\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]273
274\fBvoid png_save_uint_16 (png_bytep \fP\fIbuf\fP\fB, unsigned int \fIi\fP\fB);\fP
275
276\fBvoid png_save_uint_32 (png_bytep \fP\fIbuf\fP\fB, png_uint_32 \fIi\fP\fB);\fP
277
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]278\fBvoid png_set_add_alpha (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIfiller\fP\fB, int \fIflags\fP\fB);\fP
279
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]280\fBvoid png_set_alpha_mode (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fImode\fP\fB, double \fIoutput_gamma\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]281
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]282\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
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]283
284\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
285
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]286\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
287
288\fBvoid png_set_benign_errors (png_structp \fP\fIpng_ptr\fP\fB, int \fIallowed\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]289
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]290\fBvoid png_set_bgr (png_structp \fIpng_ptr\fP\fB);\fP
291
292\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
293
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]294\fBvoid png_set_check_for_invalid_index(png_structrp \fP\fIpng_ptr\fP\fB, int \fIallowed\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]295
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]296\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
297
298\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
299
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]300\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
301
302\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
303
304\fBvoid png_set_chunk_cache_max (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIuser_chunk_cache_max\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]305
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]306\fBvoid png_set_compression_level (png_structp \fP\fIpng_ptr\fP\fB, int \fIlevel\fP\fB);\fP
307
308\fBvoid png_set_compression_mem_level (png_structp \fP\fIpng_ptr\fP\fB, int \fImem_level\fP\fB);\fP
309
310\fBvoid png_set_compression_method (png_structp \fP\fIpng_ptr\fP\fB, int \fImethod\fP\fB);\fP
311
312\fBvoid png_set_compression_strategy (png_structp \fP\fIpng_ptr\fP\fB, int \fIstrategy\fP\fB);\fP
313
314\fBvoid png_set_compression_window_bits (png_structp \fP\fIpng_ptr\fP\fB, int \fIwindow_bits\fP\fB);\fP
315
316\fBvoid png_set_crc_action (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIcrit_action\fP\fB, int \fIancil_action\fP\fB);\fP
317
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]318\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
319
320\fBvoid png_set_expand (png_structp \fIpng_ptr\fP\fB);\fP
321
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]322\fBvoid png_set_expand_16 (png_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]323
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]324\fBvoid png_set_expand_gray_1_2_4_to_8 (png_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]325
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]326\fBvoid png_set_filler (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIfiller\fP\fB, int \fIflags\fP\fB);\fP
327
328\fBvoid png_set_filter (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fImethod\fP\fB, int \fIfilters\fP\fB);\fP
329
330\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
331
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]332\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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]333
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]334\fBvoid png_set_flush (png_structp \fP\fIpng_ptr\fP\fB, int \fInrows\fP\fB);\fP
335
336\fBvoid png_set_gamma (png_structp \fP\fIpng_ptr\fP\fB, double \fP\fIscreen_gamma\fP\fB, double \fIdefault_file_gamma\fP\fB);\fP
337
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]338\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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]339
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]340\fBvoid png_set_gAMA (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fIfile_gamma\fP\fB);\fP
341
342\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
343
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]344\fBvoid png_set_gray_1_2_4_to_8 (png_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]345
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]346\fBvoid png_set_gray_to_rgb (png_structp \fIpng_ptr\fP\fB);\fP
347
348\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
349
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]350\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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]351
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]352\fBint png_set_interlace_handling (png_structp \fIpng_ptr\fP\fB);\fP
353
354\fBvoid png_set_invalid (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fImask\fP\fB);\fP
355
356\fBvoid png_set_invert_alpha (png_structp \fIpng_ptr\fP\fB);\fP
357
358\fBvoid png_set_invert_mono (png_structp \fIpng_ptr\fP\fB);\fP
359
360\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
361
362\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
363
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]364\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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]365
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]366\fBvoid png_set_chunk_malloc_max (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIuser_chunk_cache_max\fP\fB);\fP
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]367
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]368\fBvoid png_set_compression_buffer_size (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP
369
370\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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]371
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]372\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
373
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]374\fBint png_set_option(png_structrp \fP\fIpng_ptr\fP\fB, int \fP\fIoption\fP\fB, int \fIonoff\fP\fB);\fP
375
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]376\fBvoid png_set_packing (png_structp \fIpng_ptr\fP\fB);\fP
377
378\fBvoid png_set_packswap (png_structp \fIpng_ptr\fP\fB);\fP
379
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]380\fBvoid png_set_palette_to_rgb (png_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]381
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]382\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
383
384\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
385
386\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
387
388\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
389
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]390\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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]391
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]392\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
393
394\fBvoid png_set_read_status_fn (png_structp \fP\fIpng_ptr\fP\fB, png_read_status_ptr \fIread_row_fn\fP\fB);\fP
395
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]396\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
397
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]398\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
399
400\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
401
402\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
403
404\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
405
406\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
407
408\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
409
410\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
411
412\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
413
414\fBvoid png_set_scale_16 (png_structp \fIpng_ptr\fP\fB);\fP
415
416\fBvoid png_set_shift (png_structp \fP\fIpng_ptr\fP\fB, png_color_8p \fItrue_bits\fP\fB);\fP
417
418\fBvoid png_set_sig_bytes (png_structp \fP\fIpng_ptr\fP\fB, int \fInum_bytes\fP\fB);\fP
419
420\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
421
422\fBvoid png_set_sRGB (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIsrgb_intent\fP\fB);\fP
423
424\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
425
426\fBvoid png_set_strip_16 (png_structp \fIpng_ptr\fP\fB);\fP
427
428\fBvoid png_set_strip_alpha (png_structp \fIpng_ptr\fP\fB);\fP
429
430\fBvoid png_set_strip_error_numbers (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIstrip_mode\fP\fB);\fP
431
432\fBvoid png_set_swap (png_structp \fIpng_ptr\fP\fB);\fP
433
434\fBvoid png_set_swap_alpha (png_structp \fIpng_ptr\fP\fB);\fP
435
436\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
437
438\fBvoid png_set_text_compression_level (png_structp \fP\fIpng_ptr\fP\fB, int \fIlevel\fP\fB);\fP
439
440\fBvoid png_set_text_compression_mem_level (png_structp \fP\fIpng_ptr\fP\fB, int \fImem_level\fP\fB);\fP
441
442\fBvoid png_set_text_compression_strategy (png_structp \fP\fIpng_ptr\fP\fB, int \fIstrategy\fP\fB);\fP
443
444\fBvoid png_set_text_compression_window_bits (png_structp \fP\fIpng_ptr\fP\fB, int \fIwindow_bits\fP\fB);\fP
445
446\fBvoid \fP\fIpng_set_text_compression_method\fP\fB, (png_structp \fP\fIpng_ptr\fP\fB, int \fImethod)\fP\fB);\fP
447
448\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
449
450\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
451
452\fBvoid png_set_tRNS_to_alpha (png_structp \fIpng_ptr\fP\fB);\fP
453
454\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
455
456\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
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]457
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]458\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
459
460\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
461
462\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
463
464\fBvoid png_set_write_status_fn (png_structp \fP\fIpng_ptr\fP\fB, png_write_status_ptr \fIwrite_row_fn\fP\fB);\fP
465
466\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
467
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]468\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
469
470\fBvoid png_start_read_image (png_structp \fIpng_ptr\fP\fB);\fP
471
472\fBvoid png_warning (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fImessage\fP\fB);\fP
473
474\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
475
476\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
477
478\fBvoid png_write_chunk_end (png_structp \fIpng_ptr\fP\fB);\fP
479
480\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
481
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]482\fBvoid png_write_end (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
483
484\fBvoid png_write_flush (png_structp \fIpng_ptr\fP\fB);\fP
485
486\fBvoid png_write_image (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fIimage\fP\fB);\fP
487
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]488\fBvoid png_write_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
489
490\fBvoid png_write_info_before_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
491
492\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
493
494\fBvoid png_write_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIrow\fP\fB);\fP
495
496\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
497
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]498\fBvoid png_write_sig (png_structp \fIpng_ptr\fP\fB);\fP
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]499
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]500.SH DESCRIPTION
501The
502.I libpng
503library supports encoding, decoding, and various manipulations of
504the Portable Network Graphics (PNG) format image files. It uses the
505.IR zlib(3)
506compression library.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]507Following is a copy of the libpng-manual.txt file that accompanies libpng.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]508.SH LIBPNG.TXT
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]509libpng-manual.txt - A description on how to use and modify libpng
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]510
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]511 libpng version 1.6.20 - December 3, 2015
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]512 Updated and distributed by Glenn Randers-Pehrson
513 <glennrp at users.sourceforge.net>
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]514 Copyright (c) 1998-2015 Glenn Randers-Pehrson
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]515
516 This document is released under the libpng license.
517 For conditions of distribution and use, see the disclaimer
518 and license in png.h
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]519
520 Based on:
521
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]522 libpng versions 0.97, January 1998, through 1.6.20 - December 3, 2015
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]523 Updated and distributed by Glenn Randers-Pehrson
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]524 Copyright (c) 1998-2015 Glenn Randers-Pehrson
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]525
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]526 libpng 1.0 beta 6 - version 0.96 - May 28, 1997
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]527 Updated and distributed by Andreas Dilger
528 Copyright (c) 1996, 1997 Andreas Dilger
529
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]530 libpng 1.0 beta 2 - version 0.88 - January 26, 1996
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]531 For conditions of distribution and use, see copyright
532 notice in png.h. Copyright (c) 1995, 1996 Guy Eric
533 Schalnat, Group 42, Inc.
534
535 Updated/rewritten per request in the libpng FAQ
536 Copyright (c) 1995, 1996 Frank J. T. Wojcik
537 December 18, 1995 & January 20, 1996
538
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]539 TABLE OF CONTENTS
540
541 I. Introduction
542 II. Structures
543 III. Reading
544 IV. Writing
545 V. Simplified API
546 VI. Modifying/Customizing libpng
547 VII. MNG support
548 VIII. Changes to Libpng from version 0.88
549 IX. Changes to Libpng from version 1.0.x to 1.2.x
550 X. Changes to Libpng from version 1.0.x/1.2.x to 1.4.x
551 XI. Changes to Libpng from version 1.4.x to 1.5.x
552 XII. Changes to Libpng from version 1.5.x to 1.6.x
553 XIII. Detecting libpng
554 XIV. Source code repository
555 XV. Coding style
556 XVI. Y2K Compliance in libpng
557
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]558.SH I. Introduction
559
560This file describes how to use and modify the PNG reference library
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]561(known as libpng) for your own use. In addition to this
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]562file, example.c is a good starting point for using the library, as
563it is heavily commented and should include everything most people
564will need. We assume that libpng is already installed; see the
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]565INSTALL file for instructions on how to configure and install libpng.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]566
567For examples of libpng usage, see the files "example.c", "pngtest.c",
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]568and the files in the "contrib" directory, all of which are included in
569the libpng distribution.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]570
571Libpng was written as a companion to the PNG specification, as a way
572of reducing the amount of time and effort it takes to support the PNG
573file format in application programs.
574
575The PNG specification (second edition), November 2003, is available as
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]576a W3C Recommendation and as an ISO Standard (ISO/IEC 15948:2004 (E)) at
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]577<http://www.w3.org/TR/2003/REC-PNG-20031110/
578The W3C and ISO documents have identical technical content.
579
580The PNG-1.2 specification is available at
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]581<http://png-mng.sourceforge.net/pub/png/spec/1.2/>.
582It is technically equivalent
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]583to the PNG specification (second edition) but has some additional material.
584
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]585The PNG-1.0 specification is available as RFC 2083
586<http://png-mng.sourceforge.net/pub/png/spec/1.0/> and as a
587W3C Recommendation <http://www.w3.org/TR/REC-png-961001>.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]588
589Some additional chunks are described in the special-purpose public chunks
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]590documents at <http://www.libpng.org/pub/png/spec/register/>
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]591
592Other information
593about PNG, and the latest version of libpng, can be found at the PNG home
594page, <http://www.libpng.org/pub/png/>.
595
596Most users will not have to modify the library significantly; advanced
597users may want to modify it more. All attempts were made to make it as
598complete as possible, while keeping the code easy to understand.
599Currently, this library only supports C. Support for other languages
600is being considered.
601
602Libpng has been designed to handle multiple sessions at one time,
603to be easily modifiable, to be portable to the vast majority of
604machines (ANSI, K&R, 16-, 32-, and 64-bit) available, and to be easy
605to use. The ultimate goal of libpng is to promote the acceptance of
606the PNG file format in whatever way possible. While there is still
607work to be done (see the TODO file), libpng should cover the
608majority of the needs of its users.
609
610Libpng uses zlib for its compression and decompression of PNG files.
611Further information about zlib, and the latest version of zlib, can
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]612be found at the zlib home page, <http://zlib.net/>.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]613The zlib compression utility is a general purpose utility that is
614useful for more than PNG files, and can be used without libpng.
615See the documentation delivered with zlib for more details.
616You can usually find the source files for the zlib utility wherever you
617find the libpng source files.
618
619Libpng is thread safe, provided the threads are using different
620instances of the structures. Each thread should have its own
621png_struct and png_info instances, and thus its own image.
622Libpng does not protect itself against two threads using the
623same instance of a structure.
624
625.SH II. Structures
626
627There are two main structures that are important to libpng, png_struct
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]628and png_info. Both are internal structures that are no longer exposed
629in the libpng interface (as of libpng 1.5.0).
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]630
631The png_info structure is designed to provide information about the
632PNG file. At one time, the fields of png_info were intended to be
633directly accessible to the user. However, this tended to cause problems
634with applications using dynamically loaded libraries, and as a result
635a set of interface functions for png_info (the png_get_*() and png_set_*()
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]636functions) was developed, and direct access to the png_info fields was
637deprecated..
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]638
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]639The png_struct structure is the object used by the library to decode a
640single image. As of 1.5.0 this structure is also not exposed.
641
642Almost all libpng APIs require a pointer to a png_struct as the first argument.
643Many (in particular the png_set and png_get APIs) also require a pointer
644to png_info as the second argument. Some application visible macros
645defined in png.h designed for basic data access (reading and writing
646integers in the PNG format) don't take a png_info pointer, but it's almost
647always safe to assume that a (png_struct*) has to be passed to call an API
648function.
649
650You can have more than one png_info structure associated with an image,
651as illustrated in pngtest.c, one for information valid prior to the
652IDAT chunks and another (called "end_info" below) for things after them.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]653
654The png.h header file is an invaluable reference for programming with libpng.
655And while I'm on the topic, make sure you include the libpng header file:
656
657#include <png.h>
658
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]659and also (as of libpng-1.5.0) the zlib header file, if you need it:
660
661#include <zlib.h>
662
663.SS Types
664
665The png.h header file defines a number of integral types used by the
666APIs. Most of these are fairly obvious; for example types corresponding
667to integers of particular sizes and types for passing color values.
668
669One exception is how non-integral numbers are handled. For application
670convenience most APIs that take such numbers have C (double) arguments;
671however, internally PNG, and libpng, use 32 bit signed integers and encode
672the value by multiplying by 100,000. As of libpng 1.5.0 a convenience
673macro PNG_FP_1 is defined in png.h along with a type (png_fixed_point)
674which is simply (png_int_32).
675
676All APIs that take (double) arguments also have a matching API that
677takes the corresponding fixed point integer arguments. The fixed point
678API has the same name as the floating point one with "_fixed" appended.
679The actual range of values permitted in the APIs is frequently less than
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]680the full range of (png_fixed_point) (\-21474 to +21474). When APIs require
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]681a non-negative argument the type is recorded as png_uint_32 above. Consult
682the header file and the text below for more information.
683
684Special care must be take with sCAL chunk handling because the chunk itself
685uses non-integral values encoded as strings containing decimal floating point
686numbers. See the comments in the header file.
687
688.SS Configuration
689
690The main header file function declarations are frequently protected by C
691preprocessing directives of the form:
692
693 #ifdef PNG_feature_SUPPORTED
694 declare-function
695 #endif
696 ...
697 #ifdef PNG_feature_SUPPORTED
698 use-function
699 #endif
700
701The library can be built without support for these APIs, although a
702standard build will have all implemented APIs. Application programs
703should check the feature macros before using an API for maximum
704portability. From libpng 1.5.0 the feature macros set during the build
705of libpng are recorded in the header file "pnglibconf.h" and this file
706is always included by png.h.
707
708If you don't need to change the library configuration from the default, skip to
709the next section ("Reading").
710
711Notice that some of the makefiles in the 'scripts' directory and (in 1.5.0) all
712of the build project files in the 'projects' directory simply copy
713scripts/pnglibconf.h.prebuilt to pnglibconf.h. This means that these build
714systems do not permit easy auto-configuration of the library - they only
715support the default configuration.
716
717The easiest way to make minor changes to the libpng configuration when
718auto-configuration is supported is to add definitions to the command line
719using (typically) CPPFLAGS. For example:
720
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]721CPPFLAGS=\-DPNG_NO_FLOATING_ARITHMETIC
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]722
723will change the internal libpng math implementation for gamma correction and
724other arithmetic calculations to fixed point, avoiding the need for fast
725floating point support. The result can be seen in the generated pnglibconf.h -
726make sure it contains the changed feature macro setting.
727
728If you need to make more extensive configuration changes - more than one or two
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]729feature macro settings - you can either add \-DPNG_USER_CONFIG to the build
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]730command line and put a list of feature macro settings in pngusr.h or you can set
731DFA_XTRA (a makefile variable) to a file containing the same information in the
732form of 'option' settings.
733
734A. Changing pnglibconf.h
735
736A variety of methods exist to build libpng. Not all of these support
737reconfiguration of pnglibconf.h. To reconfigure pnglibconf.h it must either be
738rebuilt from scripts/pnglibconf.dfa using awk or it must be edited by hand.
739
740Hand editing is achieved by copying scripts/pnglibconf.h.prebuilt to
741pnglibconf.h and changing the lines defining the supported features, paying
742very close attention to the 'option' information in scripts/pnglibconf.dfa
743that describes those features and their requirements. This is easy to get
744wrong.
745
746B. Configuration using DFA_XTRA
747
748Rebuilding from pnglibconf.dfa is easy if a functioning 'awk', or a later
749variant such as 'nawk' or 'gawk', is available. The configure build will
750automatically find an appropriate awk and build pnglibconf.h.
751The scripts/pnglibconf.mak file contains a set of make rules for doing the
752same thing if configure is not used, and many of the makefiles in the scripts
753directory use this approach.
754
755When rebuilding simply write a new file containing changed options and set
756DFA_XTRA to the name of this file. This causes the build to append the new file
757to the end of scripts/pnglibconf.dfa. The pngusr.dfa file should contain lines
758of the following forms:
759
760everything = off
761
762This turns all optional features off. Include it at the start of pngusr.dfa to
763make it easier to build a minimal configuration. You will need to turn at least
764some features on afterward to enable either reading or writing code, or both.
765
766option feature on
767option feature off
768
769Enable or disable a single feature. This will automatically enable other
770features required by a feature that is turned on or disable other features that
771require a feature which is turned off. Conflicting settings will cause an error
772message to be emitted by awk.
773
774setting feature default value
775
776Changes the default value of setting 'feature' to 'value'. There are a small
777number of settings listed at the top of pnglibconf.h, they are documented in the
778source code. Most of these values have performance implications for the library
779but most of them have no visible effect on the API. Some can also be overridden
780from the API.
781
782This method of building a customized pnglibconf.h is illustrated in
783contrib/pngminim/*. See the "$(PNGCONF):" target in the makefile and
784pngusr.dfa in these directories.
785
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]786C. Configuration using PNG_USER_CONFIG
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]787
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]788If \-DPNG_USER_CONFIG is added to the CPPFLAGS when pnglibconf.h is built,
789the file pngusr.h will automatically be included before the options in
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]790scripts/pnglibconf.dfa are processed. Your pngusr.h file should contain only
791macro definitions turning features on or off or setting settings.
792
793Apart from the global setting "everything = off" all the options listed above
794can be set using macros in pngusr.h:
795
796#define PNG_feature_SUPPORTED
797
798is equivalent to:
799
800option feature on
801
802#define PNG_NO_feature
803
804is equivalent to:
805
806option feature off
807
808#define PNG_feature value
809
810is equivalent to:
811
812setting feature default value
813
814Notice that in both cases, pngusr.dfa and pngusr.h, the contents of the
815pngusr file you supply override the contents of scripts/pnglibconf.dfa
816
817If confusing or incomprehensible behavior results it is possible to
818examine the intermediate file pnglibconf.dfn to find the full set of
819dependency information for each setting and option. Simply locate the
820feature in the file and read the C comments that precede it.
821
822This method is also illustrated in the contrib/pngminim/* makefiles and
823pngusr.h.
824
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]825.SH III. Reading
826
827We'll now walk you through the possible functions to call when reading
828in a PNG file sequentially, briefly explaining the syntax and purpose
829of each one. See example.c and png.h for more detail. While
830progressive reading is covered in the next section, you will still
831need some of the functions discussed in this section to read a PNG
832file.
833
834.SS Setup
835
836You will want to do the I/O initialization(*) before you get into libpng,
837so if it doesn't work, you don't have much to undo. Of course, you
838will also want to insure that you are, in fact, dealing with a PNG
839file. Libpng provides a simple check to see if a file is a PNG file.
840To use it, pass in the first 1 to 8 bytes of the file to the function
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]841png_sig_cmp(), and it will return 0 (false) if the bytes match the
842corresponding bytes of the PNG signature, or nonzero (true) otherwise.
843Of course, the more bytes you pass in, the greater the accuracy of the
844prediction.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]845
846If you are intending to keep the file pointer open for use in libpng,
847you must ensure you don't read more than 8 bytes from the beginning
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]848of the file, and you also have to make a call to png_set_sig_bytes()
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]849with the number of bytes you read from the beginning. Libpng will
850then only check the bytes (if any) that your program didn't read.
851
852(*): If you are not using the standard I/O functions, you will need
853to replace them with custom functions. See the discussion under
854Customizing libpng.
855
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]856 FILE *fp = fopen(file_name, "rb");
857 if (!fp)
858 {
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]859 return (ERROR);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]860 }
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]861
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]862 if (fread(header, 1, number, fp) != number)
863 {
864 return (ERROR);
865 }
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]866
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]867 is_png = !png_sig_cmp(header, 0, number);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]868 if (!is_png)
869 {
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]870 return (NOT_PNG);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]871 }
872
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]873Next, png_struct and png_info need to be allocated and initialized. In
874order to ensure that the size of these structures is correct even with a
875dynamically linked libpng, there are functions to initialize and
876allocate the structures. We also pass the library version, optional
877pointers to error handling functions, and a pointer to a data struct for
878use by the error functions, if necessary (the pointer and functions can
879be NULL if the default error handlers are to be used). See the section
880on Changes to Libpng below regarding the old initialization functions.
881The structure allocation functions quietly return NULL if they fail to
882create the structure, so your application should check for that.
883
884 png_structp png_ptr = png_create_read_struct
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]885 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]886 user_error_fn, user_warning_fn);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]887
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]888 if (!png_ptr)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]889 return (ERROR);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]890
891 png_infop info_ptr = png_create_info_struct(png_ptr);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]892
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]893 if (!info_ptr)
894 {
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]895 png_destroy_read_struct(&png_ptr,
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]896 (png_infopp)NULL, (png_infopp)NULL);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]897 return (ERROR);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]898 }
899
900If you want to use your own memory allocation routines,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]901use a libpng that was built with PNG_USER_MEM_SUPPORTED defined, and use
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]902png_create_read_struct_2() instead of png_create_read_struct():
903
904 png_structp png_ptr = png_create_read_struct_2
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]905 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]906 user_error_fn, user_warning_fn, (png_voidp)
907 user_mem_ptr, user_malloc_fn, user_free_fn);
908
909The error handling routines passed to png_create_read_struct()
910and the memory alloc/free routines passed to png_create_struct_2()
911are only necessary if you are not using the libpng supplied error
912handling and memory alloc/free functions.
913
914When libpng encounters an error, it expects to longjmp back
915to your routine. Therefore, you will need to call setjmp and pass
916your png_jmpbuf(png_ptr). If you read the file from different
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]917routines, you will need to update the longjmp buffer every time you enter
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]918a new routine that will call a png_*() function.
919
920See your documentation of setjmp/longjmp for your compiler for more
921information on setjmp/longjmp. See the discussion on libpng error
922handling in the Customizing Libpng section below for more information
923on the libpng error handling. If an error occurs, and libpng longjmp's
924back to your setjmp, you will want to call png_destroy_read_struct() to
925free any memory.
926
927 if (setjmp(png_jmpbuf(png_ptr)))
928 {
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]929 png_destroy_read_struct(&png_ptr, &info_ptr,
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]930 &end_info);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]931 fclose(fp);
932 return (ERROR);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]933 }
934
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]935Pass (png_infopp)NULL instead of &end_info if you didn't create
936an end_info structure.
937
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]938If you would rather avoid the complexity of setjmp/longjmp issues,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]939you can compile libpng with PNG_NO_SETJMP, in which case
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]940errors will result in a call to PNG_ABORT() which defaults to abort().
941
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]942You can #define PNG_ABORT() to a function that does something
943more useful than abort(), as long as your function does not
944return.
945
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]946Now you need to set up the input code. The default for libpng is to
947use the C function fread(). If you use this, you will need to pass a
948valid FILE * in the function png_init_io(). Be sure that the file is
949opened in binary mode. If you wish to handle reading data in another
950way, you need not call the png_init_io() function, but you must then
951implement the libpng I/O methods discussed in the Customizing Libpng
952section below.
953
954 png_init_io(png_ptr, fp);
955
956If you had previously opened the file and read any of the signature from
957the beginning in order to see if this was a PNG file, you need to let
958libpng know that there are some bytes missing from the start of the file.
959
960 png_set_sig_bytes(png_ptr, number);
961
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]962You can change the zlib compression buffer size to be used while
963reading compressed data with
964
965 png_set_compression_buffer_size(png_ptr, buffer_size);
966
967where the default size is 8192 bytes. Note that the buffer size
968is changed immediately and the buffer is reallocated immediately,
969instead of setting a flag to be acted upon later.
970
971If you want CRC errors to be handled in a different manner than
972the default, use
973
974 png_set_crc_action(png_ptr, crit_action, ancil_action);
975
976The values for png_set_crc_action() say how libpng is to handle CRC errors in
977ancillary and critical chunks, and whether to use the data contained
978therein. Note that it is impossible to "discard" data in a critical
979chunk.
980
981Choices for (int) crit_action are
982 PNG_CRC_DEFAULT 0 error/quit
983 PNG_CRC_ERROR_QUIT 1 error/quit
984 PNG_CRC_WARN_USE 3 warn/use data
985 PNG_CRC_QUIET_USE 4 quiet/use data
986 PNG_CRC_NO_CHANGE 5 use the current value
987
988Choices for (int) ancil_action are
989 PNG_CRC_DEFAULT 0 error/quit
990 PNG_CRC_ERROR_QUIT 1 error/quit
991 PNG_CRC_WARN_DISCARD 2 warn/discard data
992 PNG_CRC_WARN_USE 3 warn/use data
993 PNG_CRC_QUIET_USE 4 quiet/use data
994 PNG_CRC_NO_CHANGE 5 use the current value
995
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]996.SS Setting up callback code
997
998You can set up a callback function to handle any unknown chunks in the
999input stream. You must supply the function
1000
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1001 read_chunk_callback(png_structp png_ptr,
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1002 png_unknown_chunkp chunk);
1003 {
1004 /* The unknown chunk structure contains your
1005 chunk data, along with similar data for any other
1006 unknown chunks: */
1007
1008 png_byte name[5];
1009 png_byte *data;
1010 png_size_t size;
1011
1012 /* Note that libpng has already taken care of
1013 the CRC handling */
1014
1015 /* put your code here. Search for your chunk in the
1016 unknown chunk structure, process it, and return one
1017 of the following: */
1018
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]1019 return (\-n); /* chunk had an error */
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1020 return (0); /* did not recognize */
1021 return (n); /* success */
1022 }
1023
1024(You can give your function another name that you like instead of
1025"read_chunk_callback")
1026
1027To inform libpng about your function, use
1028
1029 png_set_read_user_chunk_fn(png_ptr, user_chunk_ptr,
1030 read_chunk_callback);
1031
1032This names not only the callback function, but also a user pointer that
1033you can retrieve with
1034
1035 png_get_user_chunk_ptr(png_ptr);
1036
1037If you call the png_set_read_user_chunk_fn() function, then all unknown
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1038chunks which the callback does not handle will be saved when read. You can
1039cause them to be discarded by returning '1' ("handled") instead of '0'. This
1040behavior will change in libpng 1.7 and the default handling set by the
1041png_set_keep_unknown_chunks() function, described below, will be used when the
1042callback returns 0. If you want the existing behavior you should set the global
1043default to PNG_HANDLE_CHUNK_IF_SAFE now; this is compatible with all current
1044versions of libpng and with 1.7. Libpng 1.6 issues a warning if you keep the
1045default, or PNG_HANDLE_CHUNK_NEVER, and the callback returns 0.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1046
1047At this point, you can set up a callback function that will be
1048called after each row has been read, which you can use to control
1049a progress meter or the like. It's demonstrated in pngtest.c.
1050You must supply a function
1051
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1052 void read_row_callback(png_structp png_ptr,
1053 png_uint_32 row, int pass);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1054 {
1055 /* put your code here */
1056 }
1057
1058(You can give it another name that you like instead of "read_row_callback")
1059
1060To inform libpng about your function, use
1061
1062 png_set_read_status_fn(png_ptr, read_row_callback);
1063
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1064When this function is called the row has already been completely processed and
1065the 'row' and 'pass' refer to the next row to be handled. For the
1066non-interlaced case the row that was just handled is simply one less than the
1067passed in row number, and pass will always be 0. For the interlaced case the
1068same applies unless the row value is 0, in which case the row just handled was
1069the last one from one of the preceding passes. Because interlacing may skip a
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]1070pass you cannot be sure that the preceding pass is just 'pass\-1', if you really
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1071need to know what the last pass is record (row,pass) from the callback and use
1072the last recorded value each time.
1073
1074As with the user transform you can find the output row using the
1075PNG_ROW_FROM_PASS_ROW macro.
1076
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1077.SS Unknown-chunk handling
1078
1079Now you get to set the way the library processes unknown chunks in the
1080input PNG stream. Both known and unknown chunks will be read. Normal
1081behavior is that known chunks will be parsed into information in
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]1082various info_ptr members while unknown chunks will be discarded. This
1083behavior can be wasteful if your application will never use some known
1084chunk types. To change this, you can call:
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1085
1086 png_set_keep_unknown_chunks(png_ptr, keep,
1087 chunk_list, num_chunks);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1088
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1089 keep - 0: default unknown chunk handling
1090 1: ignore; do not keep
1091 2: keep only if safe-to-copy
1092 3: keep even if unsafe-to-copy
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1093
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1094 You can use these definitions:
1095 PNG_HANDLE_CHUNK_AS_DEFAULT 0
1096 PNG_HANDLE_CHUNK_NEVER 1
1097 PNG_HANDLE_CHUNK_IF_SAFE 2
1098 PNG_HANDLE_CHUNK_ALWAYS 3
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1099
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1100 chunk_list - list of chunks affected (a byte string,
1101 five bytes per chunk, NULL or '\0' if
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1102 num_chunks is positive; ignored if
1103 numchunks <= 0).
1104
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1105 num_chunks - number of chunks affected; if 0, all
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1106 unknown chunks are affected. If positive,
1107 only the chunks in the list are affected,
1108 and if negative all unknown chunks and
1109 all known chunks except for the IHDR,
1110 PLTE, tRNS, IDAT, and IEND chunks are
1111 affected.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1112
1113Unknown chunks declared in this way will be saved as raw data onto a
1114list of png_unknown_chunk structures. If a chunk that is normally
1115known to libpng is named in the list, it will be handled as unknown,
1116according to the "keep" directive. If a chunk is named in successive
1117instances of png_set_keep_unknown_chunks(), the final instance will
1118take precedence. The IHDR and IEND chunks should not be named in
1119chunk_list; if they are, libpng will process them normally anyway.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1120If you know that your application will never make use of some particular
1121chunks, use PNG_HANDLE_CHUNK_NEVER (or 1) as demonstrated below.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1122
1123Here is an example of the usage of png_set_keep_unknown_chunks(),
1124where the private "vpAg" chunk will later be processed by a user chunk
1125callback function:
1126
1127 png_byte vpAg[5]={118, 112, 65, 103, (png_byte) '\0'};
1128
1129 #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
1130 png_byte unused_chunks[]=
1131 {
1132 104, 73, 83, 84, (png_byte) '\0', /* hIST */
1133 105, 84, 88, 116, (png_byte) '\0', /* iTXt */
1134 112, 67, 65, 76, (png_byte) '\0', /* pCAL */
1135 115, 67, 65, 76, (png_byte) '\0', /* sCAL */
1136 115, 80, 76, 84, (png_byte) '\0', /* sPLT */
1137 116, 73, 77, 69, (png_byte) '\0', /* tIME */
1138 };
1139 #endif
1140
1141 ...
1142
1143 #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1144 /* ignore all unknown chunks
1145 * (use global setting "2" for libpng16 and earlier):
1146 */
1147 png_set_keep_unknown_chunks(read_ptr, 2, NULL, 0);
1148
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1149 /* except for vpAg: */
1150 png_set_keep_unknown_chunks(read_ptr, 2, vpAg, 1);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1151
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1152 /* also ignore unused known chunks: */
1153 png_set_keep_unknown_chunks(read_ptr, 1, unused_chunks,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1154 (int)(sizeof unused_chunks)/5);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1155 #endif
1156
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]1157.SS User limits
1158
1159The PNG specification allows the width and height of an image to be as
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]1160large as 2^(31\-1 (0x7fffffff), or about 2.147 billion rows and columns.
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]1161For safety, libpng imposes a default limit of 1 million rows and columns.
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]1162Larger images will be rejected immediately with a png_error() call. If
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]1163you wish to change these limits, you can use
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]1164
1165 png_set_user_limits(png_ptr, width_max, height_max);
1166
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]1167to set your own limits (libpng may reject some very wide images
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]1168anyway because of potential buffer overflow conditions).
1169
1170You should put this statement after you create the PNG structure and
1171before calling png_read_info(), png_read_png(), or png_process_data().
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1172
1173When writing a PNG datastream, put this statement before calling
1174png_write_info() or png_write_png().
1175
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]1176If you need to retrieve the limits that are being applied, use
1177
1178 width_max = png_get_user_width_max(png_ptr);
1179 height_max = png_get_user_height_max(png_ptr);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1180
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]1181The PNG specification sets no limit on the number of ancillary chunks
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]1182allowed in a PNG datastream. By default, libpng imposes a limit of
1183a total of 1000 sPLT, tEXt, iTXt, zTXt, and unknown chunks to be stored.
1184If you have set up both info_ptr and end_info_ptr, the limit applies
1185separately to each. You can change the limit on the total number of such
1186chunks that will be stored, with
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]1187
1188 png_set_chunk_cache_max(png_ptr, user_chunk_cache_max);
1189
1190where 0x7fffffffL means unlimited. You can retrieve this limit with
1191
1192 chunk_cache_max = png_get_chunk_cache_max(png_ptr);
1193
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]1194Libpng imposes a limit of 8 Megabytes (8,000,000 bytes) on the amount of
1195memory that a compressed chunk other than IDAT can occupy, when decompressed.
1196You can change this limit with
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1197
1198 png_set_chunk_malloc_max(png_ptr, user_chunk_malloc_max);
1199
1200and you can retrieve the limit with
1201
1202 chunk_malloc_max = png_get_chunk_malloc_max(png_ptr);
1203
1204Any chunks that would cause either of these limits to be exceeded will
1205be ignored.
1206
1207.SS Information about your system
1208
1209If you intend to display the PNG or to incorporate it in other image data you
1210need to tell libpng information about your display or drawing surface so that
1211libpng can convert the values in the image to match the display.
1212
1213From libpng-1.5.4 this information can be set before reading the PNG file
1214header. In earlier versions png_set_gamma() existed but behaved incorrectly if
1215called before the PNG file header had been read and png_set_alpha_mode() did not
1216exist.
1217
1218If you need to support versions prior to libpng-1.5.4 test the version number
1219as illustrated below using "PNG_LIBPNG_VER >= 10504" and follow the procedures
1220described in the appropriate manual page.
1221
1222You give libpng the encoding expected by your system expressed as a 'gamma'
1223value. You can also specify a default encoding for the PNG file in
1224case the required information is missing from the file. By default libpng
1225assumes that the PNG data matches your system, to keep this default call:
1226
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]1227 png_set_gamma(png_ptr, screen_gamma, output_gamma);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1228
1229or you can use the fixed point equivalent:
1230
1231 png_set_gamma_fixed(png_ptr, PNG_FP_1*screen_gamma,
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]1232 PNG_FP_1*output_gamma);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1233
1234If you don't know the gamma for your system it is probably 2.2 - a good
1235approximation to the IEC standard for display systems (sRGB). If images are
1236too contrasty or washed out you got the value wrong - check your system
1237documentation!
1238
1239Many systems permit the system gamma to be changed via a lookup table in the
1240display driver, a few systems, including older Macs, change the response by
1241default. As of 1.5.4 three special values are available to handle common
1242situations:
1243
1244 PNG_DEFAULT_sRGB: Indicates that the system conforms to the
1245 IEC 61966-2-1 standard. This matches almost
1246 all systems.
1247 PNG_GAMMA_MAC_18: Indicates that the system is an older
1248 (pre Mac OS 10.6) Apple Macintosh system with
1249 the default settings.
1250 PNG_GAMMA_LINEAR: Just the fixed point value for 1.0 - indicates
1251 that the system expects data with no gamma
1252 encoding.
1253
1254You would use the linear (unencoded) value if you need to process the pixel
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]1255values further because this avoids the need to decode and re-encode each
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1256component value whenever arithmetic is performed. A lot of graphics software
1257uses linear values for this reason, often with higher precision component values
1258to preserve overall accuracy.
1259
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]1260
1261The output_gamma value expresses how to decode the output values, not how
1262they are encoded. The values used correspond to the normal numbers used to
1263describe the overall gamma of a computer display system; for example 2.2 for
1264an sRGB conformant system. The values are scaled by 100000 in the _fixed
1265version of the API (so 220000 for sRGB.)
1266
1267The inverse of the value is always used to provide a default for the PNG file
1268encoding if it has no gAMA chunk and if png_set_gamma() has not been called
1269to override the PNG gamma information.
1270
1271When the ALPHA_OPTIMIZED mode is selected the output gamma is used to encode
1272opaque pixels however pixels with lower alpha values are not encoded,
1273regardless of the output gamma setting.
1274
1275When the standard Porter Duff handling is requested with mode 1 the output
1276encoding is set to be linear and the output_gamma value is only relevant
1277as a default for input data that has no gamma information. The linear output
1278encoding will be overridden if png_set_gamma() is called - the results may be
1279highly unexpected!
1280
1281The following numbers are derived from the sRGB standard and the research
1282behind it. sRGB is defined to be approximated by a PNG gAMA chunk value of
12830.45455 (1/2.2) for PNG. The value implicitly includes any viewing
1284correction required to take account of any differences in the color
1285environment of the original scene and the intended display environment; the
1286value expresses how to *decode* the image for display, not how the original
1287data was *encoded*.
1288
1289sRGB provides a peg for the PNG standard by defining a viewing environment.
1290sRGB itself, and earlier TV standards, actually use a more complex transform
1291(a linear portion then a gamma 2.4 power law) than PNG can express. (PNG is
1292limited to simple power laws.) By saying that an image for direct display on
1293an sRGB conformant system should be stored with a gAMA chunk value of 45455
1294(11.3.3.2 and 11.3.3.5 of the ISO PNG specification) the PNG specification
1295makes it possible to derive values for other display systems and
1296environments.
1297
1298The Mac value is deduced from the sRGB based on an assumption that the actual
1299extra viewing correction used in early Mac display systems was implemented as
1300a power 1.45 lookup table.
1301
1302Any system where a programmable lookup table is used or where the behavior of
1303the final display device characteristics can be changed requires system
1304specific code to obtain the current characteristic. However this can be
1305difficult and most PNG gamma correction only requires an approximate value.
1306
1307By default, if png_set_alpha_mode() is not called, libpng assumes that all
1308values are unencoded, linear, values and that the output device also has a
1309linear characteristic. This is only very rarely correct - it is invariably
1310better to call png_set_alpha_mode() with PNG_DEFAULT_sRGB than rely on the
1311default if you don't know what the right answer is!
1312
1313The special value PNG_GAMMA_MAC_18 indicates an older Mac system (pre Mac OS
131410.6) which used a correction table to implement a somewhat lower gamma on an
1315otherwise sRGB system.
1316
1317Both these values are reserved (not simple gamma values) in order to allow
1318more precise correction internally in the future.
1319
1320NOTE: the values can be passed to either the fixed or floating
1321point APIs, but the floating point API will also accept floating point
1322values.
1323
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1324The second thing you may need to tell libpng about is how your system handles
1325alpha channel information. Some, but not all, PNG files contain an alpha
1326channel. To display these files correctly you need to compose the data onto a
1327suitable background, as described in the PNG specification.
1328
1329Libpng only supports composing onto a single color (using png_set_background;
1330see below). Otherwise you must do the composition yourself and, in this case,
1331you may need to call png_set_alpha_mode:
1332
1333 #if PNG_LIBPNG_VER >= 10504
1334 png_set_alpha_mode(png_ptr, mode, screen_gamma);
1335 #else
1336 png_set_gamma(png_ptr, screen_gamma, 1.0/screen_gamma);
1337 #endif
1338
1339The screen_gamma value is the same as the argument to png_set_gamma; however,
1340how it affects the output depends on the mode. png_set_alpha_mode() sets the
1341file gamma default to 1/screen_gamma, so normally you don't need to call
1342png_set_gamma. If you need different defaults call png_set_gamma() before
1343png_set_alpha_mode() - if you call it after it will override the settings made
1344by png_set_alpha_mode().
1345
1346The mode is as follows:
1347
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]1348 PNG_ALPHA_PNG: The data is encoded according to the PNG
1349specification. Red, green and blue, or gray, components are
1350gamma encoded color values and are not premultiplied by the
1351alpha value. The alpha value is a linear measure of the
1352contribution of the pixel to the corresponding final output pixel.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1353
1354You should normally use this format if you intend to perform
1355color correction on the color values; most, maybe all, color
1356correction software has no handling for the alpha channel and,
1357anyway, the math to handle pre-multiplied component values is
1358unnecessarily complex.
1359
1360Before you do any arithmetic on the component values you need
1361to remove the gamma encoding and multiply out the alpha
1362channel. See the PNG specification for more detail. It is
1363important to note that when an image with an alpha channel is
1364scaled, linear encoded, pre-multiplied component values must
1365be used!
1366
1367The remaining modes assume you don't need to do any further color correction or
1368that if you do, your color correction software knows all about alpha (it
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]1369probably doesn't!). They 'associate' the alpha with the color information by
1370storing color channel values that have been scaled by the alpha. The
1371advantage is that the color channels can be resampled (the image can be
1372scaled) in this form. The disadvantage is that normal practice is to store
1373linear, not (gamma) encoded, values and this requires 16-bit channels for
1374still images rather than the 8-bit channels that are just about sufficient if
1375gamma encoding is used. In addition all non-transparent pixel values,
1376including completely opaque ones, must be gamma encoded to produce the final
1377image. These are the 'STANDARD', 'ASSOCIATED' or 'PREMULTIPLIED' modes
1378described below (the latter being the two common names for associated alpha
1379color channels). Note that PNG files always contain non-associated color
1380channels; png_set_alpha_mode() with one of the modes causes the decoder to
1381convert the pixels to an associated form before returning them to your
1382application.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1383
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]1384Since it is not necessary to perform arithmetic on opaque color values so
1385long as they are not to be resampled and are in the final color space it is
1386possible to optimize the handling of alpha by storing the opaque pixels in
1387the PNG format (adjusted for the output color space) while storing partially
1388opaque pixels in the standard, linear, format. The accuracy required for
1389standard alpha composition is relatively low, because the pixels are
1390isolated, therefore typically the accuracy loss in storing 8-bit linear
1391values is acceptable. (This is not true if the alpha channel is used to
1392simulate transparency over large areas - use 16 bits or the PNG mode in
1393this case!) This is the 'OPTIMIZED' mode. For this mode a pixel is
1394treated as opaque only if the alpha value is equal to the maximum value.
1395
1396 PNG_ALPHA_STANDARD: The data libpng produces is encoded in the
1397standard way assumed by most correctly written graphics software.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1398The gamma encoding will be removed by libpng and the
1399linear component values will be pre-multiplied by the
1400alpha channel.
1401
1402With this format the final image must be re-encoded to
1403match the display gamma before the image is displayed.
1404If your system doesn't do that, yet still seems to
1405perform arithmetic on the pixels without decoding them,
1406it is broken - check out the modes below.
1407
1408With PNG_ALPHA_STANDARD libpng always produces linear
1409component values, whatever screen_gamma you supply. The
1410screen_gamma value is, however, used as a default for
1411the file gamma if the PNG file has no gamma information.
1412
1413If you call png_set_gamma() after png_set_alpha_mode() you
1414will override the linear encoding. Instead the
1415pre-multiplied pixel values will be gamma encoded but
1416the alpha channel will still be linear. This may
1417actually match the requirements of some broken software,
1418but it is unlikely.
1419
1420While linear 8-bit data is often used it has
1421insufficient precision for any image with a reasonable
1422dynamic range. To avoid problems, and if your software
1423supports it, use png_set_expand_16() to force all
1424components to 16 bits.
1425
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]1426 PNG_ALPHA_OPTIMIZED: This mode is the same as PNG_ALPHA_STANDARD
1427except that completely opaque pixels are gamma encoded according to
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1428the screen_gamma value. Pixels with alpha less than 1.0
1429will still have linear components.
1430
1431Use this format if you have control over your
1432compositing software and so don't do other arithmetic
1433(such as scaling) on the data you get from libpng. Your
1434compositing software can simply copy opaque pixels to
1435the output but still has linear values for the
1436non-opaque pixels.
1437
1438In normal compositing, where the alpha channel encodes
1439partial pixel coverage (as opposed to broad area
1440translucency), the inaccuracies of the 8-bit
1441representation of non-opaque pixels are irrelevant.
1442
1443You can also try this format if your software is broken;
1444it might look better.
1445
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]1446 PNG_ALPHA_BROKEN: This is PNG_ALPHA_STANDARD; however, all component
1447values, including the alpha channel are gamma encoded. This is
1448broken because, in practice, no implementation that uses this choice
1449correctly undoes the encoding before handling alpha composition. Use this
1450choice only if other serious errors in the software or hardware you use
1451mandate it. In most cases of broken software or hardware the bug in the
1452final display manifests as a subtle halo around composited parts of the
1453image. You may not even perceive this as a halo; the composited part of
1454the image may simply appear separate from the background, as though it had
1455been cut out of paper and pasted on afterward.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1456
1457If you don't have to deal with bugs in software or hardware, or if you can fix
1458them, there are three recommended ways of using png_set_alpha_mode():
1459
1460 png_set_alpha_mode(png_ptr, PNG_ALPHA_PNG,
1461 screen_gamma);
1462
1463You can do color correction on the result (libpng does not currently
1464support color correction internally). When you handle the alpha channel
1465you need to undo the gamma encoding and multiply out the alpha.
1466
1467 png_set_alpha_mode(png_ptr, PNG_ALPHA_STANDARD,
1468 screen_gamma);
1469 png_set_expand_16(png_ptr);
1470
1471If you are using the high level interface, don't call png_set_expand_16();
1472instead pass PNG_TRANSFORM_EXPAND_16 to the interface.
1473
1474With this mode you can't do color correction, but you can do arithmetic,
1475including composition and scaling, on the data without further processing.
1476
1477 png_set_alpha_mode(png_ptr, PNG_ALPHA_OPTIMIZED,
1478 screen_gamma);
1479
1480You can avoid the expansion to 16-bit components with this mode, but you
1481lose the ability to scale the image or perform other linear arithmetic.
1482All you can do is compose the result onto a matching output. Since this
1483mode is libpng-specific you also need to write your own composition
1484software.
1485
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]1486The following are examples of calls to png_set_alpha_mode to achieve the
1487required overall gamma correction and, where necessary, alpha
1488premultiplication.
1489
1490 png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_DEFAULT_sRGB);
1491
1492This is the default libpng handling of the alpha channel - it is not
1493pre-multiplied into the color components. In addition the call states
1494that the output is for a sRGB system and causes all PNG files without gAMA
1495chunks to be assumed to be encoded using sRGB.
1496
1497 png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_GAMMA_MAC);
1498
1499In this case the output is assumed to be something like an sRGB conformant
1500display preceeded by a power-law lookup table of power 1.45. This is how
1501early Mac systems behaved.
1502
1503 png_set_alpha_mode(pp, PNG_ALPHA_STANDARD, PNG_GAMMA_LINEAR);
1504
1505This is the classic Jim Blinn approach and will work in academic
1506environments where everything is done by the book. It has the shortcoming
1507of assuming that input PNG data with no gamma information is linear - this
1508is unlikely to be correct unless the PNG files where generated locally.
1509Most of the time the output precision will be so low as to show
1510significant banding in dark areas of the image.
1511
1512 png_set_expand_16(pp);
1513 png_set_alpha_mode(pp, PNG_ALPHA_STANDARD, PNG_DEFAULT_sRGB);
1514
1515This is a somewhat more realistic Jim Blinn inspired approach. PNG files
1516are assumed to have the sRGB encoding if not marked with a gamma value and
1517the output is always 16 bits per component. This permits accurate scaling
1518and processing of the data. If you know that your input PNG files were
1519generated locally you might need to replace PNG_DEFAULT_sRGB with the
1520correct value for your system.
1521
1522 png_set_alpha_mode(pp, PNG_ALPHA_OPTIMIZED, PNG_DEFAULT_sRGB);
1523
1524If you just need to composite the PNG image onto an existing background
1525and if you control the code that does this you can use the optimization
1526setting. In this case you just copy completely opaque pixels to the
1527output. For pixels that are not completely transparent (you just skip
1528those) you do the composition math using png_composite or png_composite_16
1529below then encode the resultant 8-bit or 16-bit values to match the output
1530encoding.
1531
1532 Other cases
1533
1534If neither the PNG nor the standard linear encoding work for you because
1535of the software or hardware you use then you have a big problem. The PNG
1536case will probably result in halos around the image. The linear encoding
1537will probably result in a washed out, too bright, image (it's actually too
1538contrasty.) Try the ALPHA_OPTIMIZED mode above - this will probably
1539substantially reduce the halos. Alternatively try:
1540
1541 png_set_alpha_mode(pp, PNG_ALPHA_BROKEN, PNG_DEFAULT_sRGB);
1542
1543This option will also reduce the halos, but there will be slight dark
1544halos round the opaque parts of the image where the background is light.
1545In the OPTIMIZED mode the halos will be light halos where the background
1546is dark. Take your pick - the halos are unavoidable unless you can get
1547your hardware/software fixed! (The OPTIMIZED approach is slightly
1548faster.)
1549
1550When the default gamma of PNG files doesn't match the output gamma.
1551If you have PNG files with no gamma information png_set_alpha_mode allows
1552you to provide a default gamma, but it also sets the ouput gamma to the
1553matching value. If you know your PNG files have a gamma that doesn't
1554match the output you can take advantage of the fact that
1555png_set_alpha_mode always sets the output gamma but only sets the PNG
1556default if it is not already set:
1557
1558 png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_DEFAULT_sRGB);
1559 png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_GAMMA_MAC);
1560
1561The first call sets both the default and the output gamma values, the
1562second call overrides the output gamma without changing the default. This
1563is easier than achieving the same effect with png_set_gamma. You must use
1564PNG_ALPHA_PNG for the first call - internal checking in png_set_alpha will
1565fire if more than one call to png_set_alpha_mode and png_set_background is
1566made in the same read operation, however multiple calls with PNG_ALPHA_PNG
1567are ignored.
1568
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1569If you don't need, or can't handle, the alpha channel you can call
1570png_set_background() to remove it by compositing against a fixed color. Don't
1571call png_set_strip_alpha() to do this - it will leave spurious pixel values in
1572transparent parts of this image.
1573
1574 png_set_background(png_ptr, &background_color,
1575 PNG_BACKGROUND_GAMMA_SCREEN, 0, 1);
1576
1577The background_color is an RGB or grayscale value according to the data format
1578libpng will produce for you. Because you don't yet know the format of the PNG
1579file, if you call png_set_background at this point you must arrange for the
1580format produced by libpng to always have 8-bit or 16-bit components and then
1581store the color as an 8-bit or 16-bit color as appropriate. The color contains
1582separate gray and RGB component values, so you can let libpng produce gray or
1583RGB output according to the input format, but low bit depth grayscale images
1584must always be converted to at least 8-bit format. (Even though low bit depth
1585grayscale images can't have an alpha channel they can have a transparent
1586color!)
1587
1588You set the transforms you need later, either as flags to the high level
1589interface or libpng API calls for the low level interface. For reference the
1590settings and API calls required are:
1591
15928-bit values:
1593 PNG_TRANSFORM_SCALE_16 | PNG_EXPAND
1594 png_set_expand(png_ptr); png_set_scale_16(png_ptr);
1595
1596 If you must get exactly the same inaccurate results
1597 produced by default in versions prior to libpng-1.5.4,
1598 use PNG_TRANSFORM_STRIP_16 and png_set_strip_16(png_ptr)
1599 instead.
1600
160116-bit values:
1602 PNG_TRANSFORM_EXPAND_16
1603 png_set_expand_16(png_ptr);
1604
1605In either case palette image data will be expanded to RGB. If you just want
1606color data you can add PNG_TRANSFORM_GRAY_TO_RGB or png_set_gray_to_rgb(png_ptr)
1607to the list.
1608
1609Calling png_set_background before the PNG file header is read will not work
1610prior to libpng-1.5.4. Because the failure may result in unexpected warnings or
1611errors it is therefore much safer to call png_set_background after the head has
1612been read. Unfortunately this means that prior to libpng-1.5.4 it cannot be
1613used with the high level interface.
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]1614
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1615.SS The high-level read interface
1616
1617At this point there are two ways to proceed; through the high-level
1618read interface, or through a sequence of low-level read operations.
1619You can use the high-level interface if (a) you are willing to read
1620the entire image into memory, and (b) the input transformations
1621you want to do are limited to the following set:
1622
1623 PNG_TRANSFORM_IDENTITY No transformation
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1624 PNG_TRANSFORM_SCALE_16 Strip 16-bit samples to
1625 8-bit accurately
1626 PNG_TRANSFORM_STRIP_16 Chop 16-bit samples to
1627 8-bit less accurately
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1628 PNG_TRANSFORM_STRIP_ALPHA Discard the alpha channel
1629 PNG_TRANSFORM_PACKING Expand 1, 2 and 4-bit
1630 samples to bytes
1631 PNG_TRANSFORM_PACKSWAP Change order of packed
1632 pixels to LSB first
1633 PNG_TRANSFORM_EXPAND Perform set_expand()
1634 PNG_TRANSFORM_INVERT_MONO Invert monochrome images
1635 PNG_TRANSFORM_SHIFT Normalize pixels to the
1636 sBIT depth
1637 PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA
1638 to BGRA
1639 PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA
1640 to AG
1641 PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity
1642 to transparency
1643 PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]1644 PNG_TRANSFORM_GRAY_TO_RGB Expand grayscale samples
1645 to RGB (or GA to RGBA)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1646 PNG_TRANSFORM_EXPAND_16 Expand samples to 16 bits
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1647
1648(This excludes setting a background color, doing gamma transformation,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1649quantizing, and setting filler.) If this is the case, simply do this:
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1650
1651 png_read_png(png_ptr, info_ptr, png_transforms, NULL)
1652
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]1653where png_transforms is an integer containing the bitwise OR of some
1654set of transformation flags. This call is equivalent to png_read_info(),
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1655followed the set of transformations indicated by the transform mask,
1656then png_read_image(), and finally png_read_end().
1657
1658(The final parameter of this call is not yet used. Someday it might point
1659to transformation parameters required by some future input transform.)
1660
1661You must use png_transforms and not call any png_set_transform() functions
1662when you use png_read_png().
1663
1664After you have called png_read_png(), you can retrieve the image data
1665with
1666
1667 row_pointers = png_get_rows(png_ptr, info_ptr);
1668
1669where row_pointers is an array of pointers to the pixel data for each row:
1670
1671 png_bytep row_pointers[height];
1672
1673If you know your image size and pixel size ahead of time, you can allocate
1674row_pointers prior to calling png_read_png() with
1675
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1676 if (height > PNG_UINT_32_MAX/(sizeof (png_byte)))
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1677 png_error (png_ptr,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1678 "Image is too tall to process in memory");
1679
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1680 if (width > PNG_UINT_32_MAX/pixel_size)
1681 png_error (png_ptr,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1682 "Image is too wide to process in memory");
1683
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1684 row_pointers = png_malloc(png_ptr,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1685 height*(sizeof (png_bytep)));
1686
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1687 for (int i=0; i<height, i++)
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]1688 row_pointers[i]=NULL; /* security precaution */
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1689
The Android Open Source Project4215dd12009-03-09 11:52:12 -0700[diff] [blame]1690 for (int i=0; i<height, i++)
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1691 row_pointers[i]=png_malloc(png_ptr,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1692 width*pixel_size);
1693
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1694 png_set_rows(png_ptr, info_ptr, &row_pointers);
1695
1696Alternatively you could allocate your image in one big block and define
1697row_pointers[i] to point into the proper places in your block.
1698
1699If you use png_set_rows(), the application is responsible for freeing
1700row_pointers (and row_pointers[i], if they were separately allocated).
1701
1702If you don't allocate row_pointers ahead of time, png_read_png() will
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1703do it, and it'll be free'ed by libpng when you call png_destroy_*().
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1704
1705.SS The low-level read interface
1706
1707If you are going the low-level route, you are now ready to read all
1708the file information up to the actual image data. You do this with a
1709call to png_read_info().
1710
1711 png_read_info(png_ptr, info_ptr);
1712
1713This will process all chunks up to but not including the image data.
1714
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1715This also copies some of the data from the PNG file into the decode structure
1716for use in later transformations. Important information copied in is:
1717
17181) The PNG file gamma from the gAMA chunk. This overwrites the default value
1719provided by an earlier call to png_set_gamma or png_set_alpha_mode.
1720
17212) Prior to libpng-1.5.4 the background color from a bKGd chunk. This
1722damages the information provided by an earlier call to png_set_background
1723resulting in unexpected behavior. Libpng-1.5.4 no longer does this.
1724
17253) The number of significant bits in each component value. Libpng uses this to
1726optimize gamma handling by reducing the internal lookup table sizes.
1727
17284) The transparent color information from a tRNS chunk. This can be modified by
1729a later call to png_set_tRNS.
1730
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1731.SS Querying the info structure
1732
1733Functions are used to get the information from the info_ptr once it
1734has been read. Note that these fields may not be completely filled
1735in until png_read_end() has read the chunk data following the image.
1736
1737 png_get_IHDR(png_ptr, info_ptr, &width, &height,
1738 &bit_depth, &color_type, &interlace_type,
1739 &compression_type, &filter_method);
1740
1741 width - holds the width of the image
1742 in pixels (up to 2^31).
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1743
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1744 height - holds the height of the image
1745 in pixels (up to 2^31).
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1746
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1747 bit_depth - holds the bit depth of one of the
1748 image channels. (valid values are
1749 1, 2, 4, 8, 16 and depend also on
1750 the color_type. See also
1751 significant bits (sBIT) below).
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1752
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1753 color_type - describes which color/alpha channels
1754 are present.
1755 PNG_COLOR_TYPE_GRAY
1756 (bit depths 1, 2, 4, 8, 16)
1757 PNG_COLOR_TYPE_GRAY_ALPHA
1758 (bit depths 8, 16)
1759 PNG_COLOR_TYPE_PALETTE
1760 (bit depths 1, 2, 4, 8)
1761 PNG_COLOR_TYPE_RGB
1762 (bit_depths 8, 16)
1763 PNG_COLOR_TYPE_RGB_ALPHA
1764 (bit_depths 8, 16)
1765
1766 PNG_COLOR_MASK_PALETTE
1767 PNG_COLOR_MASK_COLOR
1768 PNG_COLOR_MASK_ALPHA
1769
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1770 interlace_type - (PNG_INTERLACE_NONE or
1771 PNG_INTERLACE_ADAM7)
1772
1773 compression_type - (must be PNG_COMPRESSION_TYPE_BASE
1774 for PNG 1.0)
1775
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1776 filter_method - (must be PNG_FILTER_TYPE_BASE
1777 for PNG 1.0, and can also be
1778 PNG_INTRAPIXEL_DIFFERENCING if
1779 the PNG datastream is embedded in
1780 a MNG-1.0 datastream)
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]1781
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]1782 Any of width, height, color_type, bit_depth,
1783 interlace_type, compression_type, or filter_method can
1784 be NULL if you are not interested in their values.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1785
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]1786 Note that png_get_IHDR() returns 32-bit data into
1787 the application's width and height variables.
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]1788 This is an unsafe situation if these are not png_uint_32
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]1789 variables. In such situations, the
1790 png_get_image_width() and png_get_image_height()
1791 functions described below are safer.
1792
1793 width = png_get_image_width(png_ptr,
1794 info_ptr);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1795
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]1796 height = png_get_image_height(png_ptr,
1797 info_ptr);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1798
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]1799 bit_depth = png_get_bit_depth(png_ptr,
1800 info_ptr);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1801
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]1802 color_type = png_get_color_type(png_ptr,
1803 info_ptr);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1804
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]1805 interlace_type = png_get_interlace_type(png_ptr,
1806 info_ptr);
1807
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1808 compression_type = png_get_compression_type(png_ptr,
1809 info_ptr);
1810
1811 filter_method = png_get_filter_type(png_ptr,
1812 info_ptr);
1813
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1814 channels = png_get_channels(png_ptr, info_ptr);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1815
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1816 channels - number of channels of info for the
1817 color type (valid values are 1 (GRAY,
1818 PALETTE), 2 (GRAY_ALPHA), 3 (RGB),
1819 4 (RGB_ALPHA or RGB + filler byte))
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1820
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1821 rowbytes = png_get_rowbytes(png_ptr, info_ptr);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1822
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1823 rowbytes - number of bytes needed to hold a row
1824
1825 signature = png_get_signature(png_ptr, info_ptr);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1826
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1827 signature - holds the signature read from the
1828 file (if any). The data is kept in
1829 the same offset it would be if the
1830 whole signature were read (i.e. if an
1831 application had already read in 4
1832 bytes of signature before starting
1833 libpng, the remaining 4 bytes would
1834 be in signature[4] through signature[7]
1835 (see png_set_sig_bytes())).
1836
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1837These are also important, but their validity depends on whether the chunk
1838has been read. The png_get_valid(png_ptr, info_ptr, PNG_INFO_<chunk>) and
1839png_get_<chunk>(png_ptr, info_ptr, ...) functions return non-zero if the
1840data has been read, or zero if it is missing. The parameters to the
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]1841png_get_<chunk> are set directly if they are simple data types, or a
1842pointer into the info_ptr is returned for any complex types.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1843
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1844The colorspace data from gAMA, cHRM, sRGB, iCCP, and sBIT chunks
1845is simply returned to give the application information about how the
1846image was encoded. Libpng itself only does transformations using the file
1847gamma when combining semitransparent pixels with the background color, and,
1848since libpng-1.6.0, when converting between 8-bit sRGB and 16-bit linear pixels
1849within the simplified API. Libpng also uses the file gamma when converting
1850RGB to gray, beginning with libpng-1.0.5, if the application calls
1851png_set_rgb_to_gray()).
1852
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1853 png_get_PLTE(png_ptr, info_ptr, &palette,
1854 &num_palette);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1855
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1856 palette - the palette for the file
1857 (array of png_color)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1858
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1859 num_palette - number of entries in the palette
1860
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1861 png_get_gAMA(png_ptr, info_ptr, &file_gamma);
1862 png_get_gAMA_fixed(png_ptr, info_ptr, &int_file_gamma);
1863
1864 file_gamma - the gamma at which the file is
1865 written (PNG_INFO_gAMA)
1866
1867 int_file_gamma - 100,000 times the gamma at which the
1868 file is written
1869
1870 png_get_cHRM(png_ptr, info_ptr, &white_x, &white_y, &red_x,
1871 &red_y, &green_x, &green_y, &blue_x, &blue_y)
1872 png_get_cHRM_XYZ(png_ptr, info_ptr, &red_X, &red_Y, &red_Z,
1873 &green_X, &green_Y, &green_Z, &blue_X, &blue_Y,
1874 &blue_Z)
1875 png_get_cHRM_fixed(png_ptr, info_ptr, &int_white_x,
1876 &int_white_y, &int_red_x, &int_red_y,
1877 &int_green_x, &int_green_y, &int_blue_x,
1878 &int_blue_y)
1879 png_get_cHRM_XYZ_fixed(png_ptr, info_ptr, &int_red_X, &int_red_Y,
1880 &int_red_Z, &int_green_X, &int_green_Y,
1881 &int_green_Z, &int_blue_X, &int_blue_Y,
1882 &int_blue_Z)
1883
1884 {white,red,green,blue}_{x,y}
1885 A color space encoding specified using the
1886 chromaticities of the end points and the
1887 white point. (PNG_INFO_cHRM)
1888
1889 {red,green,blue}_{X,Y,Z}
1890 A color space encoding specified using the
1891 encoding end points - the CIE tristimulus
1892 specification of the intended color of the red,
1893 green and blue channels in the PNG RGB data.
1894 The white point is simply the sum of the three
1895 end points. (PNG_INFO_cHRM)
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1896
1897 png_get_sRGB(png_ptr, info_ptr, &srgb_intent);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1898
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]1899 srgb_intent - the rendering intent (PNG_INFO_sRGB)
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1900 The presence of the sRGB chunk
1901 means that the pixel data is in the
1902 sRGB color space. This chunk also
1903 implies specific values of gAMA and
1904 cHRM.
1905
1906 png_get_iCCP(png_ptr, info_ptr, &name,
1907 &compression_type, &profile, &proflen);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1908
1909 name - The profile name.
1910
1911 compression_type - The compression type; always
1912 PNG_COMPRESSION_TYPE_BASE for PNG 1.0.
1913 You may give NULL to this argument to
1914 ignore it.
1915
1916 profile - International Color Consortium color
1917 profile data. May contain NULs.
1918
1919 proflen - length of profile data in bytes.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1920
1921 png_get_sBIT(png_ptr, info_ptr, &sig_bit);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1922
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1923 sig_bit - the number of significant bits for
1924 (PNG_INFO_sBIT) each of the gray,
1925 red, green, and blue channels,
1926 whichever are appropriate for the
1927 given color type (png_color_16)
1928
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1929 png_get_tRNS(png_ptr, info_ptr, &trans_alpha,
1930 &num_trans, &trans_color);
1931
1932 trans_alpha - array of alpha (transparency)
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]1933 entries for palette (PNG_INFO_tRNS)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1934
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1935 num_trans - number of transparent entries
1936 (PNG_INFO_tRNS)
1937
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1938 trans_color - graylevel or color sample values of
1939 the single transparent color for
1940 non-paletted images (PNG_INFO_tRNS)
1941
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1942 png_get_hIST(png_ptr, info_ptr, &hist);
1943 (PNG_INFO_hIST)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1944
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1945 hist - histogram of palette (array of
1946 png_uint_16)
1947
1948 png_get_tIME(png_ptr, info_ptr, &mod_time);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1949
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1950 mod_time - time image was last modified
1951 (PNG_VALID_tIME)
1952
1953 png_get_bKGD(png_ptr, info_ptr, &background);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1954
1955 background - background color (of type
1956 png_color_16p) (PNG_VALID_bKGD)
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1957 valid 16-bit red, green and blue
1958 values, regardless of color_type
1959
1960 num_comments = png_get_text(png_ptr, info_ptr,
1961 &text_ptr, &num_text);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1962
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1963 num_comments - number of comments
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1964
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1965 text_ptr - array of png_text holding image
1966 comments
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1967
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1968 text_ptr[i].compression - type of compression used
1969 on "text" PNG_TEXT_COMPRESSION_NONE
1970 PNG_TEXT_COMPRESSION_zTXt
1971 PNG_ITXT_COMPRESSION_NONE
1972 PNG_ITXT_COMPRESSION_zTXt
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1973
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1974 text_ptr[i].key - keyword for comment. Must contain
1975 1-79 characters.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1976
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1977 text_ptr[i].text - text comments for current
1978 keyword. Can be empty.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1979
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1980 text_ptr[i].text_length - length of text string,
1981 after decompression, 0 for iTXt
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1982
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1983 text_ptr[i].itxt_length - length of itxt string,
1984 after decompression, 0 for tEXt/zTXt
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1985
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1986 text_ptr[i].lang - language of comment (empty
1987 string for unknown).
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1988
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]1989 text_ptr[i].lang_key - keyword in UTF-8
1990 (empty string for unknown).
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1991
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]1992 Note that the itxt_length, lang, and lang_key
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]1993 members of the text_ptr structure only exist when the
1994 library is built with iTXt chunk support. Prior to
1995 libpng-1.4.0 the library was built by default without
1996 iTXt support. Also note that when iTXt is supported,
1997 they contain NULL pointers when the "compression"
1998 field contains PNG_TEXT_COMPRESSION_NONE or
1999 PNG_TEXT_COMPRESSION_zTXt.
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]2000
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2001 num_text - number of comments (same as
2002 num_comments; you can put NULL here
2003 to avoid the duplication)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2004
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2005 Note while png_set_text() will accept text, language,
2006 and translated keywords that can be NULL pointers, the
2007 structure returned by png_get_text will always contain
2008 regular zero-terminated C strings. They might be
2009 empty strings but they will never be NULL pointers.
2010
2011 num_spalettes = png_get_sPLT(png_ptr, info_ptr,
2012 &palette_ptr);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2013
2014 num_spalettes - number of sPLT chunks read.
2015
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2016 palette_ptr - array of palette structures holding
2017 contents of one or more sPLT chunks
2018 read.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2019
2020 png_get_oFFs(png_ptr, info_ptr, &offset_x, &offset_y,
2021 &unit_type);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2022
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2023 offset_x - positive offset from the left edge
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2024 of the screen (can be negative)
2025
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2026 offset_y - positive offset from the top edge
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2027 of the screen (can be negative)
2028
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2029 unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
2030
2031 png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y,
2032 &unit_type);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2033
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2034 res_x - pixels/unit physical resolution in
2035 x direction
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2036
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2037 res_y - pixels/unit physical resolution in
2038 x direction
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2039
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2040 unit_type - PNG_RESOLUTION_UNKNOWN,
2041 PNG_RESOLUTION_METER
2042
2043 png_get_sCAL(png_ptr, info_ptr, &unit, &width,
2044 &height)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2045
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2046 unit - physical scale units (an integer)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2047
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2048 width - width of a pixel in physical scale units
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2049
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2050 height - height of a pixel in physical scale units
2051 (width and height are doubles)
2052
2053 png_get_sCAL_s(png_ptr, info_ptr, &unit, &width,
2054 &height)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2055
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2056 unit - physical scale units (an integer)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2057
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2058 width - width of a pixel in physical scale units
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2059 (expressed as a string)
2060
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2061 height - height of a pixel in physical scale units
2062 (width and height are strings like "2.54")
2063
2064 num_unknown_chunks = png_get_unknown_chunks(png_ptr,
2065 info_ptr, &unknowns)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2066
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2067 unknowns - array of png_unknown_chunk
2068 structures holding unknown chunks
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2069
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2070 unknowns[i].name - name of unknown chunk
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2071
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2072 unknowns[i].data - data of unknown chunk
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2073
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2074 unknowns[i].size - size of unknown chunk's data
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2075
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2076 unknowns[i].location - position of chunk in file
2077
2078 The value of "i" corresponds to the order in which the
2079 chunks were read from the PNG file or inserted with the
2080 png_set_unknown_chunks() function.
2081
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2082 The value of "location" is a bitwise "or" of
2083
2084 PNG_HAVE_IHDR (0x01)
2085 PNG_HAVE_PLTE (0x02)
2086 PNG_AFTER_IDAT (0x08)
2087
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2088The data from the pHYs chunk can be retrieved in several convenient
2089forms:
2090
2091 res_x = png_get_x_pixels_per_meter(png_ptr,
2092 info_ptr)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2093
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2094 res_y = png_get_y_pixels_per_meter(png_ptr,
2095 info_ptr)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2096
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2097 res_x_and_y = png_get_pixels_per_meter(png_ptr,
2098 info_ptr)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2099
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2100 res_x = png_get_x_pixels_per_inch(png_ptr,
2101 info_ptr)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2102
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2103 res_y = png_get_y_pixels_per_inch(png_ptr,
2104 info_ptr)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2105
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2106 res_x_and_y = png_get_pixels_per_inch(png_ptr,
2107 info_ptr)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2108
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2109 aspect_ratio = png_get_pixel_aspect_ratio(png_ptr,
2110 info_ptr)
2111
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2112 Each of these returns 0 [signifying "unknown"] if
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2113 the data is not present or if res_x is 0;
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2114 res_x_and_y is 0 if res_x != res_y
2115
2116 Note that because of the way the resolutions are
2117 stored internally, the inch conversions won't
2118 come out to exactly even number. For example,
2119 72 dpi is stored as 0.28346 pixels/meter, and
2120 when this is retrieved it is 71.9988 dpi, so
2121 be sure to round the returned value appropriately
2122 if you want to display a reasonable-looking result.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2123
2124The data from the oFFs chunk can be retrieved in several convenient
2125forms:
2126
2127 x_offset = png_get_x_offset_microns(png_ptr, info_ptr);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2128
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2129 y_offset = png_get_y_offset_microns(png_ptr, info_ptr);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2130
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2131 x_offset = png_get_x_offset_inches(png_ptr, info_ptr);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2132
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2133 y_offset = png_get_y_offset_inches(png_ptr, info_ptr);
2134
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2135 Each of these returns 0 [signifying "unknown" if both
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2136 x and y are 0] if the data is not present or if the
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2137 chunk is present but the unit is the pixel. The
2138 remark about inexact inch conversions applies here
2139 as well, because a value in inches can't always be
2140 converted to microns and back without some loss
2141 of precision.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2142
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2143For more information, see the
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2144PNG specification for chunk contents. Be careful with trusting
2145rowbytes, as some of the transformations could increase the space
2146needed to hold a row (expand, filler, gray_to_rgb, etc.).
2147See png_read_update_info(), below.
2148
2149A quick word about text_ptr and num_text. PNG stores comments in
2150keyword/text pairs, one pair per chunk, with no limit on the number
2151of text chunks, and a 2^31 byte limit on their size. While there are
2152suggested keywords, there is no requirement to restrict the use to these
2153strings. It is strongly suggested that keywords and text be sensible
2154to humans (that's the point), so don't use abbreviations. Non-printing
2155symbols are not allowed. See the PNG specification for more details.
2156There is also no requirement to have text after the keyword.
2157
2158Keywords should be limited to 79 Latin-1 characters without leading or
2159trailing spaces, but non-consecutive spaces are allowed within the
2160keyword. It is possible to have the same keyword any number of times.
2161The text_ptr is an array of png_text structures, each holding a
2162pointer to a language string, a pointer to a keyword and a pointer to
2163a text string. The text string, language code, and translated
2164keyword may be empty or NULL pointers. The keyword/text
2165pairs are put into the array in the order that they are received.
2166However, some or all of the text chunks may be after the image, so, to
2167make sure you have read all the text chunks, don't mess with these
2168until after you read the stuff after the image. This will be
2169mentioned again below in the discussion that goes with png_read_end().
2170
2171.SS Input transformations
2172
2173After you've read the header information, you can set up the library
2174to handle any special transformations of the image data. The various
2175ways to transform the data will be described in the order that they
2176should occur. This is important, as some of these change the color
2177type and/or bit depth of the data, and some others only work on
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2178certain color types and bit depths.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2179
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2180Transformations you request are ignored if they don't have any meaning for a
2181particular input data format. However some transformations can have an effect
2182as a result of a previous transformation. If you specify a contradictory set of
2183transformations, for example both adding and removing the alpha channel, you
2184cannot predict the final result.
2185
2186The color used for the transparency values should be supplied in the same
2187format/depth as the current image data. It is stored in the same format/depth
2188as the image data in a tRNS chunk, so this is what libpng expects for this data.
2189
2190The color used for the background value depends on the need_expand argument as
2191described below.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2192
2193Data will be decoded into the supplied row buffers packed into bytes
2194unless the library has been told to transform it into another format.
2195For example, 4 bit/pixel paletted or grayscale data will be returned
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]21962 pixels/byte with the leftmost pixel in the high-order bits of the byte,
2197unless png_set_packing() is called. 8-bit RGB data will be stored
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2198in RGB RGB RGB format unless png_set_filler() or png_set_add_alpha()
2199is called to insert filler bytes, either before or after each RGB triplet.
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]2200
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]220116-bit RGB data will be returned RRGGBB RRGGBB, with the most significant
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2202byte of the color value first, unless png_set_scale_16() is called to
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2203transform it to regular RGB RGB triplets, or png_set_filler() or
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]2204png_set_add alpha() is called to insert two filler bytes, either before
2205or after each RRGGBB triplet. Similarly, 8-bit or 16-bit grayscale data can
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2206be modified with png_set_filler(), png_set_add_alpha(), png_set_strip_16(),
2207or png_set_scale_16().
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2208
2209The following code transforms grayscale images of less than 8 to 8 bits,
2210changes paletted images to RGB, and adds a full alpha channel if there is
2211transparency information in a tRNS chunk. This is most useful on
2212grayscale images with bit depths of 2 or 4 or if there is a multiple-image
2213viewing application that wishes to treat all images in the same way.
2214
2215 if (color_type == PNG_COLOR_TYPE_PALETTE)
2216 png_set_palette_to_rgb(png_ptr);
2217
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2218 if (png_get_valid(png_ptr, info_ptr,
2219 PNG_INFO_tRNS)) png_set_tRNS_to_alpha(png_ptr);
2220
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2221 if (color_type == PNG_COLOR_TYPE_GRAY &&
2222 bit_depth < 8) png_set_expand_gray_1_2_4_to_8(png_ptr);
2223
2224The first two functions are actually aliases for png_set_expand(), added
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2225in libpng version 1.0.4, with the function names expanded to improve code
2226readability. In some future version they may actually do different
2227things.
2228
2229As of libpng version 1.2.9, png_set_expand_gray_1_2_4_to_8() was
2230added. It expands the sample depth without changing tRNS to alpha.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2231
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2232As of libpng version 1.5.2, png_set_expand_16() was added. It behaves as
2233png_set_expand(); however, the resultant channels have 16 bits rather than 8.
2234Use this when the output color or gray channels are made linear to avoid fairly
2235severe accuracy loss.
2236
2237 if (bit_depth < 16)
2238 png_set_expand_16(png_ptr);
2239
2240PNG can have files with 16 bits per channel. If you only can handle
22418 bits per channel, this will strip the pixels down to 8-bit.
2242
2243 if (bit_depth == 16)
2244#if PNG_LIBPNG_VER >= 10504
2245 png_set_scale_16(png_ptr);
2246#else
2247 png_set_strip_16(png_ptr);
2248#endif
2249
2250(The more accurate "png_set_scale_16()" API became available in libpng version
22511.5.4).
2252
2253If you need to process the alpha channel on the image separately from the image
2254data (for example if you convert it to a bitmap mask) it is possible to have
2255libpng strip the channel leaving just RGB or gray data:
2256
2257 if (color_type & PNG_COLOR_MASK_ALPHA)
2258 png_set_strip_alpha(png_ptr);
2259
2260If you strip the alpha channel you need to find some other way of dealing with
2261the information. If, instead, you want to convert the image to an opaque
2262version with no alpha channel use png_set_background; see below.
2263
2264As of libpng version 1.5.2, almost all useful expansions are supported, the
2265major ommissions are conversion of grayscale to indexed images (which can be
2266done trivially in the application) and conversion of indexed to grayscale (which
2267can be done by a trivial manipulation of the palette.)
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]2268
2269In the following table, the 01 means grayscale with depth<8, 31 means
2270indexed with depth<8, other numerals represent the color type, "T" means
2271the tRNS chunk is present, A means an alpha channel is present, and O
2272means tRNS or alpha is present but all pixels in the image are opaque.
2273
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2274 FROM 01 31 0 0T 0O 2 2T 2O 3 3T 3O 4A 4O 6A 6O
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]2275 TO
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2276 01 - [G] - - - - - - - - - - - - -
2277 31 [Q] Q [Q] [Q] [Q] Q Q Q Q Q Q [Q] [Q] Q Q
2278 0 1 G + . . G G G G G G B B GB GB
2279 0T lt Gt t + . Gt G G Gt G G Bt Bt GBt GBt
2280 0O lt Gt t . + Gt Gt G Gt Gt G Bt Bt GBt GBt
2281 2 C P C C C + . . C - - CB CB B B
2282 2T Ct - Ct C C t + t - - - CBt CBt Bt Bt
2283 2O Ct - Ct C C t t + - - - CBt CBt Bt Bt
2284 3 [Q] p [Q] [Q] [Q] Q Q Q + . . [Q] [Q] Q Q
2285 3T [Qt] p [Qt][Q] [Q] Qt Qt Qt t + t [Qt][Qt] Qt Qt
2286 3O [Qt] p [Qt][Q] [Q] Qt Qt Qt t t + [Qt][Qt] Qt Qt
2287 4A lA G A T T GA GT GT GA GT GT + BA G GBA
2288 4O lA GBA A T T GA GT GT GA GT GT BA + GBA G
2289 6A CA PA CA C C A T tT PA P P C CBA + BA
2290 6O CA PBA CA C C A tT T PA P P CBA C BA +
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]2291
2292Within the matrix,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2293 "+" identifies entries where 'from' and 'to' are the same.
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]2294 "-" means the transformation is not supported.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2295 "." means nothing is necessary (a tRNS chunk can just be ignored).
2296 "t" means the transformation is obtained by png_set_tRNS.
2297 "A" means the transformation is obtained by png_set_add_alpha().
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]2298 "X" means the transformation is obtained by png_set_expand().
2299 "1" means the transformation is obtained by
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2300 png_set_expand_gray_1_2_4_to_8() (and by png_set_expand()
2301 if there is no transparency in the original or the final
2302 format).
2303 "C" means the transformation is obtained by png_set_gray_to_rgb().
2304 "G" means the transformation is obtained by png_set_rgb_to_gray().
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]2305 "P" means the transformation is obtained by
2306 png_set_expand_palette_to_rgb().
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2307 "p" means the transformation is obtained by png_set_packing().
2308 "Q" means the transformation is obtained by png_set_quantize().
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]2309 "T" means the transformation is obtained by
2310 png_set_tRNS_to_alpha().
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2311 "B" means the transformation is obtained by
2312 png_set_background(), or png_strip_alpha().
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]2313
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2314When an entry has multiple transforms listed all are required to cause the
2315right overall transformation. When two transforms are separated by a comma
2316either will do the job. When transforms are enclosed in [] the transform should
2317do the job but this is currently unimplemented - a different format will result
2318if the suggested transformations are used.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2319
2320In PNG files, the alpha channel in an image
2321is the level of opacity. If you need the alpha channel in an image to
2322be the level of transparency instead of opacity, you can invert the
2323alpha channel (or the tRNS chunk data) after it's read, so that 0 is
2324fully opaque and 255 (in 8-bit or paletted images) or 65535 (in 16-bit
2325images) is fully transparent, with
2326
2327 png_set_invert_alpha(png_ptr);
2328
2329PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
2330they can, resulting in, for example, 8 pixels per byte for 1 bit
2331files. This code expands to 1 pixel per byte without changing the
2332values of the pixels:
2333
2334 if (bit_depth < 8)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2335 png_set_packing(png_ptr);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2336
2337PNG files have possible bit depths of 1, 2, 4, 8, and 16. All pixels
2338stored in a PNG image have been "scaled" or "shifted" up to the next
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]2339higher possible bit depth (e.g. from 5 bits/sample in the range [0,31]
2340to 8 bits/sample in the range [0, 255]). However, it is also possible
2341to convert the PNG pixel data back to the original bit depth of the
2342image. This call reduces the pixels back down to the original bit depth:
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2343
2344 png_color_8p sig_bit;
2345
2346 if (png_get_sBIT(png_ptr, info_ptr, &sig_bit))
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2347 png_set_shift(png_ptr, sig_bit);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2348
2349PNG files store 3-color pixels in red, green, blue order. This code
2350changes the storage of the pixels to blue, green, red:
2351
2352 if (color_type == PNG_COLOR_TYPE_RGB ||
2353 color_type == PNG_COLOR_TYPE_RGB_ALPHA)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2354 png_set_bgr(png_ptr);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2355
2356PNG files store RGB pixels packed into 3 or 6 bytes. This code expands them
2357into 4 or 8 bytes for windowing systems that need them in this format:
2358
2359 if (color_type == PNG_COLOR_TYPE_RGB)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2360 png_set_filler(png_ptr, filler, PNG_FILLER_BEFORE);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2361
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]2362where "filler" is the 8-bit or 16-bit number to fill with, and the location
2363is either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether
2364you want the filler before the RGB or after. When filling an 8-bit pixel,
2365the least significant 8 bits of the number are used, if a 16-bit number is
2366supplied. This transformation does not affect images that already have full
2367alpha channels. To add an opaque alpha channel, use filler=0xffff and
2368PNG_FILLER_AFTER which will generate RGBA pixels.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2369
2370Note that png_set_filler() does not change the color type. If you want
2371to do that, you can add a true alpha channel with
2372
2373 if (color_type == PNG_COLOR_TYPE_RGB ||
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2374 color_type == PNG_COLOR_TYPE_GRAY)
2375 png_set_add_alpha(png_ptr, filler, PNG_FILLER_AFTER);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2376
2377where "filler" contains the alpha value to assign to each pixel.
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]2378The png_set_add_alpha() function was added in libpng-1.2.7.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2379
2380If you are reading an image with an alpha channel, and you need the
2381data as ARGB instead of the normal PNG format RGBA:
2382
2383 if (color_type == PNG_COLOR_TYPE_RGB_ALPHA)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2384 png_set_swap_alpha(png_ptr);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2385
2386For some uses, you may want a grayscale image to be represented as
2387RGB. This code will do that conversion:
2388
2389 if (color_type == PNG_COLOR_TYPE_GRAY ||
2390 color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2391 png_set_gray_to_rgb(png_ptr);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2392
2393Conversely, you can convert an RGB or RGBA image to grayscale or grayscale
2394with alpha.
2395
2396 if (color_type == PNG_COLOR_TYPE_RGB ||
2397 color_type == PNG_COLOR_TYPE_RGB_ALPHA)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2398 png_set_rgb_to_gray(png_ptr, error_action,
2399 double red_weight, double green_weight);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2400
2401 error_action = 1: silently do the conversion
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2402
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2403 error_action = 2: issue a warning if the original
2404 image has any pixel where
2405 red != green or red != blue
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2406
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2407 error_action = 3: issue an error and abort the
2408 conversion if the original
2409 image has any pixel where
2410 red != green or red != blue
2411
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2412 red_weight: weight of red component
2413
2414 green_weight: weight of green component
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2415 If either weight is negative, default
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2416 weights are used.
2417
2418In the corresponding fixed point API the red_weight and green_weight values are
2419simply scaled by 100,000:
2420
2421 png_set_rgb_to_gray(png_ptr, error_action,
2422 png_fixed_point red_weight,
2423 png_fixed_point green_weight);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2424
2425If you have set error_action = 1 or 2, you can
2426later check whether the image really was gray, after processing
2427the image rows, with the png_get_rgb_to_gray_status(png_ptr) function.
2428It will return a png_byte that is zero if the image was gray or
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]24291 if there were any non-gray pixels. Background and sBIT data
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2430will be silently converted to grayscale, using the green channel
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2431data for sBIT, regardless of the error_action setting.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2432
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2433The default values come from the PNG file cHRM chunk if present; otherwise, the
2434defaults correspond to the ITU-R recommendation 709, and also the sRGB color
2435space, as recommended in the Charles Poynton's Colour FAQ,
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]2436Copyright (c) 2006-11-28 Charles Poynton, in section 9:
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2437
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]2438<http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC9>
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2439
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2440 Y = 0.2126 * R + 0.7152 * G + 0.0722 * B
2441
2442Previous versions of this document, 1998 through 2002, recommended a slightly
2443different formula:
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2444
2445 Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
2446
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2447Libpng uses an integer approximation:
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2448
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2449 Y = (6968 * R + 23434 * G + 2366 * B)/32768
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2450
2451The calculation is done in a linear colorspace, if the image gamma
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2452can be determined.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2453
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2454The png_set_background() function has been described already; it tells libpng to
2455composite images with alpha or simple transparency against the supplied
2456background color. For compatibility with versions of libpng earlier than
2457libpng-1.5.4 it is recommended that you call the function after reading the file
2458header, even if you don't want to use the color in a bKGD chunk, if one exists.
2459
2460If the PNG file contains a bKGD chunk (PNG_INFO_bKGD valid),
2461you may use this color, or supply another color more suitable for
2462the current display (e.g., the background color from a web page). You
2463need to tell libpng how the color is represented, both the format of the
2464component values in the color (the number of bits) and the gamma encoding of the
2465color. The function takes two arguments, background_gamma_mode and need_expand
2466to convey this information; however, only two combinations are likely to be
2467useful:
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2468
2469 png_color_16 my_background;
2470 png_color_16p image_background;
2471
2472 if (png_get_bKGD(png_ptr, info_ptr, &image_background))
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2473 png_set_background(png_ptr, image_background,
2474 PNG_BACKGROUND_GAMMA_FILE, 1/*needs to be expanded*/, 1);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2475 else
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2476 png_set_background(png_ptr, &my_background,
2477 PNG_BACKGROUND_GAMMA_SCREEN, 0/*do not expand*/, 1);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2478
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2479The second call was described above - my_background is in the format of the
2480final, display, output produced by libpng. Because you now know the format of
2481the PNG it is possible to avoid the need to choose either 8-bit or 16-bit
2482output and to retain palette images (the palette colors will be modified
2483appropriately and the tRNS chunk removed.) However, if you are doing this,
2484take great care not to ask for transformations without checking first that
2485they apply!
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2486
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2487In the first call the background color has the original bit depth and color type
2488of the PNG file. So, for palette images the color is supplied as a palette
2489index and for low bit greyscale images the color is a reduced bit value in
2490image_background->gray.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2491
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2492If you didn't call png_set_gamma() before reading the file header, for example
2493if you need your code to remain compatible with older versions of libpng prior
2494to libpng-1.5.4, this is the place to call it.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2495
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2496Do not call it if you called png_set_alpha_mode(); doing so will damage the
2497settings put in place by png_set_alpha_mode(). (If png_set_alpha_mode() is
2498supported then you can certainly do png_set_gamma() before reading the PNG
2499header.)
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2500
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2501This API unconditionally sets the screen and file gamma values, so it will
2502override the value in the PNG file unless it is called before the PNG file
2503reading starts. For this reason you must always call it with the PNG file
2504value when you call it in this position:
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2505
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2506 if (png_get_gAMA(png_ptr, info_ptr, &file_gamma))
2507 png_set_gamma(png_ptr, screen_gamma, file_gamma);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2508
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2509 else
2510 png_set_gamma(png_ptr, screen_gamma, 0.45455);
2511
2512If you need to reduce an RGB file to a paletted file, or if a paletted
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]2513file has more entries than will fit on your screen, png_set_quantize()
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2514will do that. Note that this is a simple match quantization that merely
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2515finds the closest color available. This should work fairly well with
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2516optimized palettes, but fairly badly with linear color cubes. If you
2517pass a palette that is larger than maximum_colors, the file will
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2518reduce the number of colors in the palette so it will fit into
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2519maximum_colors. If there is a histogram, libpng will use it to make
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2520more intelligent choices when reducing the palette. If there is no
2521histogram, it may not do as good a job.
2522
2523 if (color_type & PNG_COLOR_MASK_COLOR)
2524 {
2525 if (png_get_valid(png_ptr, info_ptr,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2526 PNG_INFO_PLTE))
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2527 {
2528 png_uint_16p histogram = NULL;
2529
2530 png_get_hIST(png_ptr, info_ptr,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2531 &histogram);
2532 png_set_quantize(png_ptr, palette, num_palette,
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2533 max_screen_colors, histogram, 1);
2534 }
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2535
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2536 else
2537 {
2538 png_color std_color_cube[MAX_SCREEN_COLORS] =
2539 { ... colors ... };
2540
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2541 png_set_quantize(png_ptr, std_color_cube,
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2542 MAX_SCREEN_COLORS, MAX_SCREEN_COLORS,
2543 NULL,0);
2544 }
2545 }
2546
2547PNG files describe monochrome as black being zero and white being one.
2548The following code will reverse this (make black be one and white be
2549zero):
2550
2551 if (bit_depth == 1 && color_type == PNG_COLOR_TYPE_GRAY)
2552 png_set_invert_mono(png_ptr);
2553
2554This function can also be used to invert grayscale and gray-alpha images:
2555
2556 if (color_type == PNG_COLOR_TYPE_GRAY ||
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2557 color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2558 png_set_invert_mono(png_ptr);
2559
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2560PNG files store 16-bit pixels in network byte order (big-endian,
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2561ie. most significant bits first). This code changes the storage to the
2562other way (little-endian, i.e. least significant bits first, the
2563way PCs store them):
2564
2565 if (bit_depth == 16)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2566 png_set_swap(png_ptr);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2567
2568If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you
2569need to change the order the pixels are packed into bytes, you can use:
2570
2571 if (bit_depth < 8)
2572 png_set_packswap(png_ptr);
2573
2574Finally, you can write your own transformation function if none of
2575the existing ones meets your needs. This is done by setting a callback
2576with
2577
2578 png_set_read_user_transform_fn(png_ptr,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2579 read_transform_fn);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2580
2581You must supply the function
2582
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2583 void read_transform_fn(png_structp png_ptr, png_row_infop
2584 row_info, png_bytep data)
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2585
2586See pngtest.c for a working example. Your function will be called
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2587after all of the other transformations have been processed. Take care with
2588interlaced images if you do the interlace yourself - the width of the row is the
2589width in 'row_info', not the overall image width.
2590
2591If supported, libpng provides two information routines that you can use to find
2592where you are in processing the image:
2593
2594 png_get_current_pass_number(png_structp png_ptr);
2595 png_get_current_row_number(png_structp png_ptr);
2596
2597Don't try using these outside a transform callback - firstly they are only
2598supported if user transforms are supported, secondly they may well return
2599unexpected results unless the row is actually being processed at the moment they
2600are called.
2601
2602With interlaced
2603images the value returned is the row in the input sub-image image. Use
2604PNG_ROW_FROM_PASS_ROW(row, pass) and PNG_COL_FROM_PASS_COL(col, pass) to
2605find the output pixel (x,y) given an interlaced sub-image pixel (row,col,pass).
2606
2607The discussion of interlace handling above contains more information on how to
2608use these values.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2609
2610You can also set up a pointer to a user structure for use by your
2611callback function, and you can inform libpng that your transform
2612function will change the number of channels or bit depth with the
2613function
2614
2615 png_set_user_transform_info(png_ptr, user_ptr,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2616 user_depth, user_channels);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2617
2618The user's application, not libpng, is responsible for allocating and
2619freeing any memory required for the user structure.
2620
2621You can retrieve the pointer via the function
2622png_get_user_transform_ptr(). For example:
2623
2624 voidp read_user_transform_ptr =
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2625 png_get_user_transform_ptr(png_ptr);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2626
2627The last thing to handle is interlacing; this is covered in detail below,
2628but you must call the function here if you want libpng to handle expansion
2629of the interlaced image.
2630
2631 number_of_passes = png_set_interlace_handling(png_ptr);
2632
2633After setting the transformations, libpng can update your png_info
2634structure to reflect any transformations you've requested with this
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2635call.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2636
2637 png_read_update_info(png_ptr, info_ptr);
2638
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2639This is most useful to update the info structure's rowbytes
2640field so you can use it to allocate your image memory. This function
2641will also update your palette with the correct screen_gamma and
2642background if these have been given with the calls above. You may
2643only call png_read_update_info() once with a particular info_ptr.
2644
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2645After you call png_read_update_info(), you can allocate any
2646memory you need to hold the image. The row data is simply
2647raw byte data for all forms of images. As the actual allocation
2648varies among applications, no example will be given. If you
2649are allocating one large chunk, you will need to build an
2650array of pointers to each row, as it will be needed for some
2651of the functions below.
2652
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2653Remember: Before you call png_read_update_info(), the png_get_*()
2654functions return the values corresponding to the original PNG image.
2655After you call png_read_update_info the values refer to the image
2656that libpng will output. Consequently you must call all the png_set_
2657functions before you call png_read_update_info(). This is particularly
2658important for png_set_interlace_handling() - if you are going to call
2659png_read_update_info() you must call png_set_interlace_handling() before
2660it unless you want to receive interlaced output.
2661
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2662.SS Reading image data
2663
2664After you've allocated memory, you can read the image data.
2665The simplest way to do this is in one function call. If you are
2666allocating enough memory to hold the whole image, you can just
2667call png_read_image() and libpng will read in all the image data
2668and put it in the memory area supplied. You will need to pass in
2669an array of pointers to each row.
2670
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2671This function automatically handles interlacing, so you don't
2672need to call png_set_interlace_handling() (unless you call
2673png_read_update_info()) or call this function multiple times, or any
2674of that other stuff necessary with png_read_rows().
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2675
2676 png_read_image(png_ptr, row_pointers);
2677
2678where row_pointers is:
2679
2680 png_bytep row_pointers[height];
2681
2682You can point to void or char or whatever you use for pixels.
2683
2684If you don't want to read in the whole image at once, you can
2685use png_read_rows() instead. If there is no interlacing (check
2686interlace_type == PNG_INTERLACE_NONE), this is simple:
2687
2688 png_read_rows(png_ptr, row_pointers, NULL,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2689 number_of_rows);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2690
2691where row_pointers is the same as in the png_read_image() call.
2692
2693If you are doing this just one row at a time, you can do this with
2694a single row_pointer instead of an array of row_pointers:
2695
2696 png_bytep row_pointer = row;
2697 png_read_row(png_ptr, row_pointer, NULL);
2698
2699If the file is interlaced (interlace_type != 0 in the IHDR chunk), things
2700get somewhat harder. The only current (PNG Specification version 1.2)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2701interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7);
2702a somewhat complicated 2D interlace scheme, known as Adam7, that
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2703breaks down an image into seven smaller images of varying size, based
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2704on an 8x8 grid. This number is defined (from libpng 1.5) as
2705PNG_INTERLACE_ADAM7_PASSES in png.h
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2706
2707libpng can fill out those images or it can give them to you "as is".
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2708It is almost always better to have libpng handle the interlacing for you.
2709If you want the images filled out, there are two ways to do that. The one
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2710mentioned in the PNG specification is to expand each pixel to cover
2711those pixels that have not been read yet (the "rectangle" method).
2712This results in a blocky image for the first pass, which gradually
2713smooths out as more pixels are read. The other method is the "sparkle"
2714method, where pixels are drawn only in their final locations, with the
2715rest of the image remaining whatever colors they were initialized to
2716before the start of the read. The first method usually looks better,
2717but tends to be slower, as there are more pixels to put in the rows.
2718
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2719If, as is likely, you want libpng to expand the images, call this before
2720calling png_start_read_image() or png_read_update_info():
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2721
2722 if (interlace_type == PNG_INTERLACE_ADAM7)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2723 number_of_passes
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2724 = png_set_interlace_handling(png_ptr);
2725
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2726This will return the number of passes needed. Currently, this is seven,
2727but may change if another interlace type is added. This function can be
2728called even if the file is not interlaced, where it will return one pass.
2729You then need to read the whole image 'number_of_passes' times. Each time
2730will distribute the pixels from the current pass to the correct place in
2731the output image, so you need to supply the same rows to png_read_rows in
2732each pass.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2733
2734If you are not going to display the image after each pass, but are
2735going to wait until the entire image is read in, use the sparkle
2736effect. This effect is faster and the end result of either method
2737is exactly the same. If you are planning on displaying the image
2738after each pass, the "rectangle" effect is generally considered the
2739better looking one.
2740
2741If you only want the "sparkle" effect, just call png_read_rows() as
2742normal, with the third parameter NULL. Make sure you make pass over
2743the image number_of_passes times, and you don't change the data in the
2744rows between calls. You can change the locations of the data, just
2745not the data. Each pass only writes the pixels appropriate for that
2746pass, and assumes the data from previous passes is still valid.
2747
2748 png_read_rows(png_ptr, row_pointers, NULL,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2749 number_of_rows);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2750
2751If you only want the first effect (the rectangles), do the same as
2752before except pass the row buffer in the third parameter, and leave
2753the second parameter NULL.
2754
2755 png_read_rows(png_ptr, NULL, row_pointers,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2756 number_of_rows);
2757
2758If you don't want libpng to handle the interlacing details, just call
2759png_read_rows() PNG_INTERLACE_ADAM7_PASSES times to read in all the images.
2760Each of the images is a valid image by itself; however, you will almost
2761certainly need to distribute the pixels from each sub-image to the
2762correct place. This is where everything gets very tricky.
2763
2764If you want to retrieve the separate images you must pass the correct
2765number of rows to each successive call of png_read_rows(). The calculation
2766gets pretty complicated for small images, where some sub-images may
2767not even exist because either their width or height ends up zero.
2768libpng provides two macros to help you in 1.5 and later versions:
2769
2770 png_uint_32 width = PNG_PASS_COLS(image_width, pass_number);
2771 png_uint_32 height = PNG_PASS_ROWS(image_height, pass_number);
2772
2773Respectively these tell you the width and height of the sub-image
2774corresponding to the numbered pass. 'pass' is in in the range 0 to 6 -
2775this can be confusing because the specification refers to the same passes
2776as 1 to 7! Be careful, you must check both the width and height before
2777calling png_read_rows() and not call it for that pass if either is zero.
2778
2779You can, of course, read each sub-image row by row. If you want to
2780produce optimal code to make a pixel-by-pixel transformation of an
2781interlaced image this is the best approach; read each row of each pass,
2782transform it, and write it out to a new interlaced image.
2783
2784If you want to de-interlace the image yourself libpng provides further
2785macros to help that tell you where to place the pixels in the output image.
2786Because the interlacing scheme is rectangular - sub-image pixels are always
2787arranged on a rectangular grid - all you need to know for each pass is the
2788starting column and row in the output image of the first pixel plus the
2789spacing between each pixel. As of libpng 1.5 there are four macros to
2790retrieve this information:
2791
2792 png_uint_32 x = PNG_PASS_START_COL(pass);
2793 png_uint_32 y = PNG_PASS_START_ROW(pass);
2794 png_uint_32 xStep = 1U << PNG_PASS_COL_SHIFT(pass);
2795 png_uint_32 yStep = 1U << PNG_PASS_ROW_SHIFT(pass);
2796
2797These allow you to write the obvious loop:
2798
2799 png_uint_32 input_y = 0;
2800 png_uint_32 output_y = PNG_PASS_START_ROW(pass);
2801
2802 while (output_y < output_image_height)
2803 {
2804 png_uint_32 input_x = 0;
2805 png_uint_32 output_x = PNG_PASS_START_COL(pass);
2806
2807 while (output_x < output_image_width)
2808 {
2809 image[output_y][output_x] =
2810 subimage[pass][input_y][input_x++];
2811
2812 output_x += xStep;
2813 }
2814
2815 ++input_y;
2816 output_y += yStep;
2817 }
2818
2819Notice that the steps between successive output rows and columns are
2820returned as shifts. This is possible because the pixels in the subimages
2821are always a power of 2 apart - 1, 2, 4 or 8 pixels - in the original
2822image. In practice you may need to directly calculate the output coordinate
2823given an input coordinate. libpng provides two further macros for this
2824purpose:
2825
2826 png_uint_32 output_x = PNG_COL_FROM_PASS_COL(input_x, pass);
2827 png_uint_32 output_y = PNG_ROW_FROM_PASS_ROW(input_y, pass);
2828
2829Finally a pair of macros are provided to tell you if a particular image
2830row or column appears in a given pass:
2831
2832 int col_in_pass = PNG_COL_IN_INTERLACE_PASS(output_x, pass);
2833 int row_in_pass = PNG_ROW_IN_INTERLACE_PASS(output_y, pass);
2834
2835Bear in mind that you will probably also need to check the width and height
2836of the pass in addition to the above to be sure the pass even exists!
2837
2838With any luck you are convinced by now that you don't want to do your own
2839interlace handling. In reality normally the only good reason for doing this
2840is if you are processing PNG files on a pixel-by-pixel basis and don't want
2841to load the whole file into memory when it is interlaced.
2842
2843libpng includes a test program, pngvalid, that illustrates reading and
2844writing of interlaced images. If you can't get interlacing to work in your
2845code and don't want to leave it to libpng (the recommended approach), see
2846how pngvalid.c does it.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2847
2848.SS Finishing a sequential read
2849
2850After you are finished reading the image through the
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]2851low-level interface, you can finish reading the file.
2852
2853If you want to use a different crc action for handling CRC errors in
2854chunks after the image data, you can call png_set_crc_action()
2855again at this point.
2856
2857If you are interested in comments or time, which may be stored either
2858before or after the image data, you should pass the separate png_info
2859struct if you want to keep the comments from before and after the image
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2860separate.
2861
2862 png_infop end_info = png_create_info_struct(png_ptr);
2863
2864 if (!end_info)
2865 {
2866 png_destroy_read_struct(&png_ptr, &info_ptr,
2867 (png_infopp)NULL);
2868 return (ERROR);
2869 }
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2870
2871 png_read_end(png_ptr, end_info);
2872
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2873If you are not interested, you should still call png_read_end()
2874but you can pass NULL, avoiding the need to create an end_info structure.
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]2875If you do this, libpng will not process any chunks after IDAT other than
2876skipping over them and perhaps (depending on whether you have called
2877png_set_crc_action) checking their CRCs while looking for the IEND chunk.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2878
2879 png_read_end(png_ptr, (png_infop)NULL);
2880
2881If you don't call png_read_end(), then your file pointer will be
2882left pointing to the first chunk after the last IDAT, which is probably
2883not what you want if you expect to read something beyond the end of
2884the PNG datastream.
2885
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2886When you are done, you can free all memory allocated by libpng like this:
2887
2888 png_destroy_read_struct(&png_ptr, &info_ptr,
2889 &end_info);
2890
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2891or, if you didn't create an end_info structure,
2892
2893 png_destroy_read_struct(&png_ptr, &info_ptr,
2894 (png_infopp)NULL);
2895
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2896It is also possible to individually free the info_ptr members that
2897point to libpng-allocated storage with the following function:
2898
2899 png_free_data(png_ptr, info_ptr, mask, seq)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2900
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2901 mask - identifies data to be freed, a mask
2902 containing the bitwise OR of one or
2903 more of
2904 PNG_FREE_PLTE, PNG_FREE_TRNS,
2905 PNG_FREE_HIST, PNG_FREE_ICCP,
2906 PNG_FREE_PCAL, PNG_FREE_ROWS,
2907 PNG_FREE_SCAL, PNG_FREE_SPLT,
2908 PNG_FREE_TEXT, PNG_FREE_UNKN,
2909 or simply PNG_FREE_ALL
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2910
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2911 seq - sequence number of item to be freed
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]2912 (\-1 for all items)
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2913
2914This function may be safely called when the relevant storage has
2915already been freed, or has not yet been allocated, or was allocated
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]2916by the user and not by libpng, and will in those cases do nothing.
2917The "seq" parameter is ignored if only one item of the selected data
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]2918type, such as PLTE, is allowed. If "seq" is not \-1, and multiple items
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]2919are allowed for the data type identified in the mask, such as text or
2920sPLT, only the n'th item in the structure is freed, where n is "seq".
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2921
2922The default behavior is only to free data that was allocated internally
2923by libpng. This can be changed, so that libpng will not free the data,
2924or so that it will free data that was allocated by the user with png_malloc()
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2925or png_calloc() and passed in via a png_set_*() function, with
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2926
2927 png_data_freer(png_ptr, info_ptr, freer, mask)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2928
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2929 freer - one of
2930 PNG_DESTROY_WILL_FREE_DATA
2931 PNG_SET_WILL_FREE_DATA
2932 PNG_USER_WILL_FREE_DATA
2933
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2934 mask - which data elements are affected
2935 same choices as in png_free_data()
2936
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2937This function only affects data that has already been allocated.
2938You can call this function after reading the PNG data but before calling
2939any png_set_*() functions, to control whether the user or the png_set_*()
2940function is responsible for freeing any existing data that might be present,
2941and again after the png_set_*() functions to control whether the user
2942or png_destroy_*() is supposed to free the data. When the user assumes
2943responsibility for libpng-allocated data, the application must use
2944png_free() to free it, and when the user transfers responsibility to libpng
2945for data that the user has allocated, the user must have used png_malloc()
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2946or png_calloc() to allocate it.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2947
2948If you allocated your row_pointers in a single block, as suggested above in
2949the description of the high level read interface, you must not transfer
2950responsibility for freeing it to the png_set_rows or png_read_destroy function,
2951because they would also try to free the individual row_pointers[i].
2952
2953If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword
2954separately, do not transfer responsibility for freeing text_ptr to libpng,
2955because when libpng fills a png_text structure it combines these members with
2956the key member, and png_free_data() will free only text_ptr.key. Similarly,
2957if you transfer responsibility for free'ing text_ptr from libpng to your
2958application, your application must not separately free those members.
2959
2960The png_free_data() function will turn off the "valid" flag for anything
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]2961it frees. If you need to turn the flag off for a chunk that was freed by
2962your application instead of by libpng, you can use
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2963
2964 png_set_invalid(png_ptr, info_ptr, mask);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2965
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2966 mask - identifies the chunks to be made invalid,
2967 containing the bitwise OR of one or
2968 more of
2969 PNG_INFO_gAMA, PNG_INFO_sBIT,
2970 PNG_INFO_cHRM, PNG_INFO_PLTE,
2971 PNG_INFO_tRNS, PNG_INFO_bKGD,
2972 PNG_INFO_hIST, PNG_INFO_pHYs,
2973 PNG_INFO_oFFs, PNG_INFO_tIME,
2974 PNG_INFO_pCAL, PNG_INFO_sRGB,
2975 PNG_INFO_iCCP, PNG_INFO_sPLT,
2976 PNG_INFO_sCAL, PNG_INFO_IDAT
2977
2978For a more compact example of reading a PNG image, see the file example.c.
2979
2980.SS Reading PNG files progressively
2981
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]2982The progressive reader is slightly different from the non-progressive
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]2983reader. Instead of calling png_read_info(), png_read_rows(), and
2984png_read_end(), you make one call to png_process_data(), which calls
2985callbacks when it has the info, a row, or the end of the image. You
2986set up these callbacks with png_set_progressive_read_fn(). You don't
2987have to worry about the input/output functions of libpng, as you are
2988giving the library the data directly in png_process_data(). I will
2989assume that you have read the section on reading PNG files above,
2990so I will only highlight the differences (although I will show
2991all of the code).
2992
2993png_structp png_ptr;
2994png_infop info_ptr;
2995
2996 /* An example code fragment of how you would
2997 initialize the progressive reader in your
2998 application. */
2999 int
3000 initialize_png_reader()
3001 {
3002 png_ptr = png_create_read_struct
3003 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
3004 user_error_fn, user_warning_fn);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3005
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3006 if (!png_ptr)
3007 return (ERROR);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3008
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3009 info_ptr = png_create_info_struct(png_ptr);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3010
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3011 if (!info_ptr)
3012 {
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3013 png_destroy_read_struct(&png_ptr,
3014 (png_infopp)NULL, (png_infopp)NULL);
3015 return (ERROR);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3016 }
3017
3018 if (setjmp(png_jmpbuf(png_ptr)))
3019 {
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3020 png_destroy_read_struct(&png_ptr, &info_ptr,
3021 (png_infopp)NULL);
3022 return (ERROR);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3023 }
3024
3025 /* This one's new. You can provide functions
3026 to be called when the header info is valid,
3027 when each row is completed, and when the image
3028 is finished. If you aren't using all functions,
3029 you can specify NULL parameters. Even when all
3030 three functions are NULL, you need to call
3031 png_set_progressive_read_fn(). You can use
3032 any struct as the user_ptr (cast to a void pointer
3033 for the function call), and retrieve the pointer
3034 from inside the callbacks using the function
3035
3036 png_get_progressive_ptr(png_ptr);
3037
3038 which will return a void pointer, which you have
3039 to cast appropriately.
3040 */
3041 png_set_progressive_read_fn(png_ptr, (void *)user_ptr,
3042 info_callback, row_callback, end_callback);
3043
3044 return 0;
3045 }
3046
3047 /* A code fragment that you call as you receive blocks
3048 of data */
3049 int
3050 process_data(png_bytep buffer, png_uint_32 length)
3051 {
3052 if (setjmp(png_jmpbuf(png_ptr)))
3053 {
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3054 png_destroy_read_struct(&png_ptr, &info_ptr,
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3055 (png_infopp)NULL);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3056 return (ERROR);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3057 }
3058
3059 /* This one's new also. Simply give it a chunk
3060 of data from the file stream (in order, of
3061 course). On machines with segmented memory
3062 models machines, don't give it any more than
3063 64K. The library seems to run fine with sizes
3064 of 4K. Although you can give it much less if
3065 necessary (I assume you can give it chunks of
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]3066 1 byte, I haven't tried less than 256 bytes
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3067 yet). When this function returns, you may
3068 want to display any rows that were generated
3069 in the row callback if you don't already do
3070 so there.
3071 */
3072 png_process_data(png_ptr, info_ptr, buffer, length);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3073
3074 /* At this point you can call png_process_data_skip if
3075 you want to handle data the library will skip yourself;
3076 it simply returns the number of bytes to skip (and stops
3077 libpng skipping that number of bytes on the next
3078 png_process_data call).
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3079 return 0;
3080 }
3081
3082 /* This function is called (as set by
3083 png_set_progressive_read_fn() above) when enough data
3084 has been supplied so all of the header has been
3085 read.
3086 */
3087 void
3088 info_callback(png_structp png_ptr, png_infop info)
3089 {
3090 /* Do any setup here, including setting any of
3091 the transformations mentioned in the Reading
3092 PNG files section. For now, you _must_ call
3093 either png_start_read_image() or
3094 png_read_update_info() after all the
3095 transformations are set (even if you don't set
3096 any). You may start getting rows before
3097 png_process_data() returns, so this is your
3098 last chance to prepare for that.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3099
3100 This is where you turn on interlace handling,
3101 assuming you don't want to do it yourself.
3102
3103 If you need to you can stop the processing of
3104 your original input data at this point by calling
3105 png_process_data_pause. This returns the number
3106 of unprocessed bytes from the last png_process_data
3107 call - it is up to you to ensure that the next call
3108 sees these bytes again. If you don't want to bother
3109 with this you can get libpng to cache the unread
3110 bytes by setting the 'save' parameter (see png.h) but
3111 then libpng will have to copy the data internally.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3112 */
3113 }
3114
3115 /* This function is called when each row of image
3116 data is complete */
3117 void
3118 row_callback(png_structp png_ptr, png_bytep new_row,
3119 png_uint_32 row_num, int pass)
3120 {
3121 /* If the image is interlaced, and you turned
3122 on the interlace handler, this function will
3123 be called for every row in every pass. Some
3124 of these rows will not be changed from the
3125 previous pass. When the row is not changed,
3126 the new_row variable will be NULL. The rows
3127 and passes are called in order, so you don't
3128 really need the row_num and pass, but I'm
3129 supplying them because it may make your life
3130 easier.
3131
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3132 If you did not turn on interlace handling then
3133 the callback is called for each row of each
3134 sub-image when the image is interlaced. In this
3135 case 'row_num' is the row in the sub-image, not
3136 the row in the output image as it is in all other
3137 cases.
3138
3139 For the non-NULL rows of interlaced images when
3140 you have switched on libpng interlace handling,
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3141 you must call png_progressive_combine_row()
3142 passing in the row and the old row. You can
3143 call this function for NULL rows (it will just
3144 return) and for non-interlaced images (it just
3145 does the memcpy for you) if it will make the
3146 code easier. Thus, you can just do this for
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3147 all cases if you switch on interlace handling;
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3148 */
3149
3150 png_progressive_combine_row(png_ptr, old_row,
3151 new_row);
3152
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]3153 /* where old_row is what was displayed
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3154 previously for the row. Note that the first
3155 pass (pass == 0, really) will completely cover
3156 the old row, so the rows do not have to be
3157 initialized. After the first pass (and only
3158 for interlaced images), you will have to pass
3159 the current row, and the function will combine
3160 the old row and the new row.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3161
3162 You can also call png_process_data_pause in this
3163 callback - see above.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3164 */
3165 }
3166
3167 void
3168 end_callback(png_structp png_ptr, png_infop info)
3169 {
3170 /* This function is called after the whole image
3171 has been read, including any chunks after the
3172 image (up to and including the IEND). You
3173 will usually have the same info chunk as you
3174 had in the header, although some data may have
3175 been added to the comments and time fields.
3176
3177 Most people won't do much here, perhaps setting
3178 a flag that marks the image as finished.
3179 */
3180 }
3181
3182
3183
3184.SH IV. Writing
3185
3186Much of this is very similar to reading. However, everything of
3187importance is repeated here, so you won't have to constantly look
3188back up in the reading section to understand writing.
3189
3190.SS Setup
3191
3192You will want to do the I/O initialization before you get into libpng,
3193so if it doesn't work, you don't have anything to undo. If you are not
3194using the standard I/O functions, you will need to replace them with
3195custom writing functions. See the discussion under Customizing libpng.
3196
3197 FILE *fp = fopen(file_name, "wb");
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3198
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3199 if (!fp)
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3200 return (ERROR);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3201
3202Next, png_struct and png_info need to be allocated and initialized.
3203As these can be both relatively large, you may not want to store these
3204on the stack, unless you have stack space to spare. Of course, you
3205will want to check if they return NULL. If you are also reading,
3206you won't want to name your read structure and your write structure
3207both "png_ptr"; you can call them anything you like, such as
3208"read_ptr" and "write_ptr". Look at pngtest.c, for example.
3209
3210 png_structp png_ptr = png_create_write_struct
3211 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
3212 user_error_fn, user_warning_fn);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3213
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3214 if (!png_ptr)
3215 return (ERROR);
3216
3217 png_infop info_ptr = png_create_info_struct(png_ptr);
3218 if (!info_ptr)
3219 {
3220 png_destroy_write_struct(&png_ptr,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3221 (png_infopp)NULL);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3222 return (ERROR);
3223 }
3224
3225If you want to use your own memory allocation routines,
3226define PNG_USER_MEM_SUPPORTED and use
3227png_create_write_struct_2() instead of png_create_write_struct():
3228
3229 png_structp png_ptr = png_create_write_struct_2
3230 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
3231 user_error_fn, user_warning_fn, (png_voidp)
3232 user_mem_ptr, user_malloc_fn, user_free_fn);
3233
3234After you have these structures, you will need to set up the
3235error handling. When libpng encounters an error, it expects to
3236longjmp() back to your routine. Therefore, you will need to call
3237setjmp() and pass the png_jmpbuf(png_ptr). If you
3238write the file from different routines, you will need to update
3239the png_jmpbuf(png_ptr) every time you enter a new routine that will
3240call a png_*() function. See your documentation of setjmp/longjmp
3241for your compiler for more information on setjmp/longjmp. See
3242the discussion on libpng error handling in the Customizing Libpng
3243section below for more information on the libpng error handling.
3244
3245 if (setjmp(png_jmpbuf(png_ptr)))
3246 {
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3247 png_destroy_write_struct(&png_ptr, &info_ptr);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3248 fclose(fp);
3249 return (ERROR);
3250 }
3251 ...
3252 return;
3253
3254If you would rather avoid the complexity of setjmp/longjmp issues,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3255you can compile libpng with PNG_NO_SETJMP, in which case
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3256errors will result in a call to PNG_ABORT() which defaults to abort().
3257
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3258You can #define PNG_ABORT() to a function that does something
3259more useful than abort(), as long as your function does not
3260return.
3261
3262Checking for invalid palette index on write was added at libpng
32631.5.10. If a pixel contains an invalid (out-of-range) index libpng issues
3264a benign error. This is enabled by default because this condition is an
3265error according to the PNG specification, Clause 11.3.2, but the error can
3266be ignored in each png_ptr with
3267
3268 png_set_check_for_invalid_index(png_ptr, 0);
3269
3270If the error is ignored, or if png_benign_error() treats it as a warning,
3271any invalid pixels are written as-is by the encoder, resulting in an
3272invalid PNG datastream as output. In this case the application is
3273responsible for ensuring that the pixel indexes are in range when it writes
3274a PLTE chunk with fewer entries than the bit depth would allow.
3275
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3276Now you need to set up the output code. The default for libpng is to
3277use the C function fwrite(). If you use this, you will need to pass a
3278valid FILE * in the function png_init_io(). Be sure that the file is
3279opened in binary mode. Again, if you wish to handle writing data in
3280another way, see the discussion on libpng I/O handling in the Customizing
3281Libpng section below.
3282
3283 png_init_io(png_ptr, fp);
3284
3285If you are embedding your PNG into a datastream such as MNG, and don't
3286want libpng to write the 8-byte signature, or if you have already
3287written the signature in your application, use
3288
3289 png_set_sig_bytes(png_ptr, 8);
3290
3291to inform libpng that it should not write a signature.
3292
3293.SS Write callbacks
3294
3295At this point, you can set up a callback function that will be
3296called after each row has been written, which you can use to control
3297a progress meter or the like. It's demonstrated in pngtest.c.
3298You must supply a function
3299
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3300 void write_row_callback(png_structp png_ptr, png_uint_32 row,
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3301 int pass);
3302 {
3303 /* put your code here */
3304 }
3305
3306(You can give it another name that you like instead of "write_row_callback")
3307
3308To inform libpng about your function, use
3309
3310 png_set_write_status_fn(png_ptr, write_row_callback);
3311
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3312When this function is called the row has already been completely processed and
3313it has also been written out. The 'row' and 'pass' refer to the next row to be
3314handled. For the
3315non-interlaced case the row that was just handled is simply one less than the
3316passed in row number, and pass will always be 0. For the interlaced case the
3317same applies unless the row value is 0, in which case the row just handled was
3318the last one from one of the preceding passes. Because interlacing may skip a
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]3319pass you cannot be sure that the preceding pass is just 'pass\-1', if you really
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3320need to know what the last pass is record (row,pass) from the callback and use
3321the last recorded value each time.
3322
3323As with the user transform you can find the output row using the
3324PNG_ROW_FROM_PASS_ROW macro.
3325
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3326You now have the option of modifying how the compression library will
3327run. The following functions are mainly for testing, but may be useful
3328in some cases, like if you need to write PNG files extremely fast and
3329are willing to give up some compression, or if you want to get the
3330maximum possible compression at the expense of slower writing. If you
3331have no special needs in this area, let the library do what it wants by
3332not calling this function at all, as it has been tuned to deliver a good
3333speed/compression ratio. The second parameter to png_set_filter() is
3334the filter method, for which the only valid values are 0 (as of the
3335July 1999 PNG specification, version 1.2) or 64 (if you are writing
3336a PNG datastream that is to be embedded in a MNG datastream). The third
3337parameter is a flag that indicates which filter type(s) are to be tested
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]3338for each scanline. See the PNG specification for details on the specific
3339filter types.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3340
3341
3342 /* turn on or off filtering, and/or choose
3343 specific filters. You can use either a single
3344 PNG_FILTER_VALUE_NAME or the bitwise OR of one
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3345 or more PNG_FILTER_NAME masks.
3346 */
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3347 png_set_filter(png_ptr, 0,
3348 PNG_FILTER_NONE | PNG_FILTER_VALUE_NONE |
3349 PNG_FILTER_SUB | PNG_FILTER_VALUE_SUB |
3350 PNG_FILTER_UP | PNG_FILTER_VALUE_UP |
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]3351 PNG_FILTER_AVG | PNG_FILTER_VALUE_AVG |
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3352 PNG_FILTER_PAETH | PNG_FILTER_VALUE_PAETH|
3353 PNG_ALL_FILTERS);
3354
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3355If an application wants to start and stop using particular filters during
3356compression, it should start out with all of the filters (to ensure that
3357the previous row of pixels will be stored in case it's needed later),
3358and then add and remove them after the start of compression.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3359
3360If you are writing a PNG datastream that is to be embedded in a MNG
3361datastream, the second parameter can be either 0 or 64.
3362
3363The png_set_compression_*() functions interface to the zlib compression
3364library, and should mostly be ignored unless you really know what you are
3365doing. The only generally useful call is png_set_compression_level()
3366which changes how much time zlib spends on trying to compress the image
3367data. See the Compression Library (zlib.h and algorithm.txt, distributed
3368with zlib) for details on the compression levels.
3369
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3370 #include zlib.h
3371
3372 /* Set the zlib compression level */
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3373 png_set_compression_level(png_ptr,
3374 Z_BEST_COMPRESSION);
3375
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3376 /* Set other zlib parameters for compressing IDAT */
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3377 png_set_compression_mem_level(png_ptr, 8);
3378 png_set_compression_strategy(png_ptr,
3379 Z_DEFAULT_STRATEGY);
3380 png_set_compression_window_bits(png_ptr, 15);
3381 png_set_compression_method(png_ptr, 8);
3382 png_set_compression_buffer_size(png_ptr, 8192)
3383
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3384 /* Set zlib parameters for text compression
3385 * If you don't call these, the parameters
3386 * fall back on those defined for IDAT chunks
3387 */
3388 png_set_text_compression_mem_level(png_ptr, 8);
3389 png_set_text_compression_strategy(png_ptr,
3390 Z_DEFAULT_STRATEGY);
3391 png_set_text_compression_window_bits(png_ptr, 15);
3392 png_set_text_compression_method(png_ptr, 8);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3393
3394.SS Setting the contents of info for output
3395
3396You now need to fill in the png_info structure with all the data you
3397wish to write before the actual image. Note that the only thing you
3398are allowed to write after the image is the text chunks and the time
3399chunk (as of PNG Specification 1.2, anyway). See png_write_end() and
3400the latest PNG specification for more information on that. If you
3401wish to write them before the image, fill them in now, and flag that
3402data as being valid. If you want to wait until after the data, don't
3403fill them until png_write_end(). For all the fields in png_info and
3404their data types, see png.h. For explanations of what the fields
3405contain, see the PNG specification.
3406
3407Some of the more important parts of the png_info are:
3408
3409 png_set_IHDR(png_ptr, info_ptr, width, height,
3410 bit_depth, color_type, interlace_type,
3411 compression_type, filter_method)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3412
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3413 width - holds the width of the image
3414 in pixels (up to 2^31).
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3415
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3416 height - holds the height of the image
3417 in pixels (up to 2^31).
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3418
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3419 bit_depth - holds the bit depth of one of the
3420 image channels.
3421 (valid values are 1, 2, 4, 8, 16
3422 and depend also on the
3423 color_type. See also significant
3424 bits (sBIT) below).
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3425
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3426 color_type - describes which color/alpha
3427 channels are present.
3428 PNG_COLOR_TYPE_GRAY
3429 (bit depths 1, 2, 4, 8, 16)
3430 PNG_COLOR_TYPE_GRAY_ALPHA
3431 (bit depths 8, 16)
3432 PNG_COLOR_TYPE_PALETTE
3433 (bit depths 1, 2, 4, 8)
3434 PNG_COLOR_TYPE_RGB
3435 (bit_depths 8, 16)
3436 PNG_COLOR_TYPE_RGB_ALPHA
3437 (bit_depths 8, 16)
3438
3439 PNG_COLOR_MASK_PALETTE
3440 PNG_COLOR_MASK_COLOR
3441 PNG_COLOR_MASK_ALPHA
3442
3443 interlace_type - PNG_INTERLACE_NONE or
3444 PNG_INTERLACE_ADAM7
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3445
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3446 compression_type - (must be
3447 PNG_COMPRESSION_TYPE_DEFAULT)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3448
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3449 filter_method - (must be PNG_FILTER_TYPE_DEFAULT
3450 or, if you are writing a PNG to
3451 be embedded in a MNG datastream,
3452 can also be
3453 PNG_INTRAPIXEL_DIFFERENCING)
3454
3455If you call png_set_IHDR(), the call must appear before any of the
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]3456other png_set_*() functions, because they might require access to some of
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3457the IHDR settings. The remaining png_set_*() functions can be called
3458in any order.
3459
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]3460If you wish, you can reset the compression_type, interlace_type, or
3461filter_method later by calling png_set_IHDR() again; if you do this, the
3462width, height, bit_depth, and color_type must be the same in each call.
3463
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3464 png_set_PLTE(png_ptr, info_ptr, palette,
3465 num_palette);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3466
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3467 palette - the palette for the file
3468 (array of png_color)
3469 num_palette - number of entries in the palette
3470
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]3471
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3472 png_set_gAMA(png_ptr, info_ptr, file_gamma);
3473 png_set_gAMA_fixed(png_ptr, info_ptr, int_file_gamma);
3474
3475 file_gamma - the gamma at which the image was
3476 created (PNG_INFO_gAMA)
3477
3478 int_file_gamma - 100,000 times the gamma at which
3479 the image was created
3480
3481 png_set_cHRM(png_ptr, info_ptr, white_x, white_y, red_x, red_y,
3482 green_x, green_y, blue_x, blue_y)
3483 png_set_cHRM_XYZ(png_ptr, info_ptr, red_X, red_Y, red_Z, green_X,
3484 green_Y, green_Z, blue_X, blue_Y, blue_Z)
3485 png_set_cHRM_fixed(png_ptr, info_ptr, int_white_x, int_white_y,
3486 int_red_x, int_red_y, int_green_x, int_green_y,
3487 int_blue_x, int_blue_y)
3488 png_set_cHRM_XYZ_fixed(png_ptr, info_ptr, int_red_X, int_red_Y,
3489 int_red_Z, int_green_X, int_green_Y, int_green_Z,
3490 int_blue_X, int_blue_Y, int_blue_Z)
3491
3492 {white,red,green,blue}_{x,y}
3493 A color space encoding specified using the chromaticities
3494 of the end points and the white point.
3495
3496 {red,green,blue}_{X,Y,Z}
3497 A color space encoding specified using the encoding end
3498 points - the CIE tristimulus specification of the intended
3499 color of the red, green and blue channels in the PNG RGB
3500 data. The white point is simply the sum of the three end
3501 points.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3502
3503 png_set_sRGB(png_ptr, info_ptr, srgb_intent);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3504
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3505 srgb_intent - the rendering intent
3506 (PNG_INFO_sRGB) The presence of
3507 the sRGB chunk means that the pixel
3508 data is in the sRGB color space.
3509 This chunk also implies specific
3510 values of gAMA and cHRM. Rendering
3511 intent is the CSS-1 property that
3512 has been defined by the International
3513 Color Consortium
3514 (http://www.color.org).
3515 It can be one of
3516 PNG_sRGB_INTENT_SATURATION,
3517 PNG_sRGB_INTENT_PERCEPTUAL,
3518 PNG_sRGB_INTENT_ABSOLUTE, or
3519 PNG_sRGB_INTENT_RELATIVE.
3520
3521
3522 png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr,
3523 srgb_intent);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3524
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3525 srgb_intent - the rendering intent
3526 (PNG_INFO_sRGB) The presence of the
3527 sRGB chunk means that the pixel
3528 data is in the sRGB color space.
3529 This function also causes gAMA and
3530 cHRM chunks with the specific values
3531 that are consistent with sRGB to be
3532 written.
3533
3534 png_set_iCCP(png_ptr, info_ptr, name, compression_type,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3535 profile, proflen);
3536
3537 name - The profile name.
3538
3539 compression_type - The compression type; always
3540 PNG_COMPRESSION_TYPE_BASE for PNG 1.0.
3541 You may give NULL to this argument to
3542 ignore it.
3543
3544 profile - International Color Consortium color
3545 profile data. May contain NULs.
3546
3547 proflen - length of profile data in bytes.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3548
3549 png_set_sBIT(png_ptr, info_ptr, sig_bit);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3550
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3551 sig_bit - the number of significant bits for
3552 (PNG_INFO_sBIT) each of the gray, red,
3553 green, and blue channels, whichever are
3554 appropriate for the given color type
3555 (png_color_16)
3556
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3557 png_set_tRNS(png_ptr, info_ptr, trans_alpha,
3558 num_trans, trans_color);
3559
3560 trans_alpha - array of alpha (transparency)
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]3561 entries for palette (PNG_INFO_tRNS)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3562
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3563 num_trans - number of transparent entries
3564 (PNG_INFO_tRNS)
3565
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3566 trans_color - graylevel or color sample values
3567 (in order red, green, blue) of the
3568 single transparent color for
3569 non-paletted images (PNG_INFO_tRNS)
3570
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3571 png_set_hIST(png_ptr, info_ptr, hist);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3572
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3573 hist - histogram of palette (array of
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3574 png_uint_16) (PNG_INFO_hIST)
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3575
3576 png_set_tIME(png_ptr, info_ptr, mod_time);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3577
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3578 mod_time - time image was last modified
3579 (PNG_VALID_tIME)
3580
3581 png_set_bKGD(png_ptr, info_ptr, background);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3582
3583 background - background color (of type
3584 png_color_16p) (PNG_VALID_bKGD)
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3585
3586 png_set_text(png_ptr, info_ptr, text_ptr, num_text);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3587
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3588 text_ptr - array of png_text holding image
3589 comments
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3590
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3591 text_ptr[i].compression - type of compression used
3592 on "text" PNG_TEXT_COMPRESSION_NONE
3593 PNG_TEXT_COMPRESSION_zTXt
3594 PNG_ITXT_COMPRESSION_NONE
3595 PNG_ITXT_COMPRESSION_zTXt
3596 text_ptr[i].key - keyword for comment. Must contain
3597 1-79 characters.
3598 text_ptr[i].text - text comments for current
3599 keyword. Can be NULL or empty.
3600 text_ptr[i].text_length - length of text string,
3601 after decompression, 0 for iTXt
3602 text_ptr[i].itxt_length - length of itxt string,
3603 after decompression, 0 for tEXt/zTXt
3604 text_ptr[i].lang - language of comment (NULL or
3605 empty for unknown).
3606 text_ptr[i].translated_keyword - keyword in UTF-8 (NULL
3607 or empty for unknown).
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3608
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]3609 Note that the itxt_length, lang, and lang_key
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3610 members of the text_ptr structure only exist when the
3611 library is built with iTXt chunk support. Prior to
3612 libpng-1.4.0 the library was built by default without
3613 iTXt support. Also note that when iTXt is supported,
3614 they contain NULL pointers when the "compression"
3615 field contains PNG_TEXT_COMPRESSION_NONE or
3616 PNG_TEXT_COMPRESSION_zTXt.
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]3617
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3618 num_text - number of comments
3619
3620 png_set_sPLT(png_ptr, info_ptr, &palette_ptr,
3621 num_spalettes);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3622
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3623 palette_ptr - array of png_sPLT_struct structures
3624 to be added to the list of palettes
3625 in the info structure.
3626 num_spalettes - number of palette structures to be
3627 added.
3628
3629 png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y,
3630 unit_type);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3631
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3632 offset_x - positive offset from the left
3633 edge of the screen
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3634
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3635 offset_y - positive offset from the top
3636 edge of the screen
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3637
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3638 unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
3639
3640 png_set_pHYs(png_ptr, info_ptr, res_x, res_y,
3641 unit_type);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3642
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3643 res_x - pixels/unit physical resolution
3644 in x direction
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3645
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3646 res_y - pixels/unit physical resolution
3647 in y direction
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3648
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3649 unit_type - PNG_RESOLUTION_UNKNOWN,
3650 PNG_RESOLUTION_METER
3651
3652 png_set_sCAL(png_ptr, info_ptr, unit, width, height)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3653
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3654 unit - physical scale units (an integer)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3655
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3656 width - width of a pixel in physical scale units
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3657
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3658 height - height of a pixel in physical scale units
3659 (width and height are doubles)
3660
3661 png_set_sCAL_s(png_ptr, info_ptr, unit, width, height)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3662
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3663 unit - physical scale units (an integer)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3664
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3665 width - width of a pixel in physical scale units
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3666 expressed as a string
3667
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3668 height - height of a pixel in physical scale units
3669 (width and height are strings like "2.54")
3670
3671 png_set_unknown_chunks(png_ptr, info_ptr, &unknowns,
3672 num_unknowns)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3673
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3674 unknowns - array of png_unknown_chunk
3675 structures holding unknown chunks
3676 unknowns[i].name - name of unknown chunk
3677 unknowns[i].data - data of unknown chunk
3678 unknowns[i].size - size of unknown chunk's data
3679 unknowns[i].location - position to write chunk in file
3680 0: do not write chunk
3681 PNG_HAVE_IHDR: before PLTE
3682 PNG_HAVE_PLTE: before IDAT
3683 PNG_AFTER_IDAT: after IDAT
3684
3685The "location" member is set automatically according to
3686what part of the output file has already been written.
3687You can change its value after calling png_set_unknown_chunks()
3688as demonstrated in pngtest.c. Within each of the "locations",
3689the chunks are sequenced according to their position in the
3690structure (that is, the value of "i", which is the order in which
3691the chunk was either read from the input file or defined with
3692png_set_unknown_chunks).
3693
3694A quick word about text and num_text. text is an array of png_text
3695structures. num_text is the number of valid structures in the array.
3696Each png_text structure holds a language code, a keyword, a text value,
3697and a compression type.
3698
3699The compression types have the same valid numbers as the compression
3700types of the image data. Currently, the only valid number is zero.
3701However, you can store text either compressed or uncompressed, unlike
3702images, which always have to be compressed. So if you don't want the
3703text compressed, set the compression type to PNG_TEXT_COMPRESSION_NONE.
3704Because tEXt and zTXt chunks don't have a language field, if you
3705specify PNG_TEXT_COMPRESSION_NONE or PNG_TEXT_COMPRESSION_zTXt
3706any language code or translated keyword will not be written out.
3707
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3708Until text gets around a few hundred bytes, it is not worth compressing it.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3709After the text has been written out to the file, the compression type
3710is set to PNG_TEXT_COMPRESSION_NONE_WR or PNG_TEXT_COMPRESSION_zTXt_WR,
3711so that it isn't written out again at the end (in case you are calling
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3712png_write_end() with the same struct).
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3713
3714The keywords that are given in the PNG Specification are:
3715
3716 Title Short (one line) title or
3717 caption for image
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3718
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3719 Author Name of image's creator
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3720
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3721 Description Description of image (possibly long)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3722
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3723 Copyright Copyright notice
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3724
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3725 Creation Time Time of original image creation
3726 (usually RFC 1123 format, see below)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3727
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3728 Software Software used to create the image
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3729
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3730 Disclaimer Legal disclaimer
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3731
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3732 Warning Warning of nature of content
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3733
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3734 Source Device used to create the image
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3735
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3736 Comment Miscellaneous comment; conversion
3737 from other image format
3738
3739The keyword-text pairs work like this. Keywords should be short
3740simple descriptions of what the comment is about. Some typical
3741keywords are found in the PNG specification, as is some recommendations
3742on keywords. You can repeat keywords in a file. You can even write
3743some text before the image and some after. For example, you may want
3744to put a description of the image before the image, but leave the
3745disclaimer until after, so viewers working over modem connections
3746don't have to wait for the disclaimer to go over the modem before
3747they start seeing the image. Finally, keywords should be full
3748words, not abbreviations. Keywords and text are in the ISO 8859-1
3749(Latin-1) character set (a superset of regular ASCII) and can not
3750contain NUL characters, and should not contain control or other
3751unprintable characters. To make the comments widely readable, stick
3752with basic ASCII, and avoid machine specific character set extensions
3753like the IBM-PC character set. The keyword must be present, but
3754you can leave off the text string on non-compressed pairs.
3755Compressed pairs must have a text string, as only the text string
3756is compressed anyway, so the compression would be meaningless.
3757
3758PNG supports modification time via the png_time structure. Two
3759conversion routines are provided, png_convert_from_time_t() for
3760time_t and png_convert_from_struct_tm() for struct tm. The
3761time_t routine uses gmtime(). You don't have to use either of
3762these, but if you wish to fill in the png_time structure directly,
3763you should provide the time in universal time (GMT) if possible
3764instead of your local time. Note that the year number is the full
3765year (e.g. 1998, rather than 98 - PNG is year 2000 compliant!), and
3766that months start with 1.
3767
3768If you want to store the time of the original image creation, you should
3769use a plain tEXt chunk with the "Creation Time" keyword. This is
3770necessary because the "creation time" of a PNG image is somewhat vague,
3771depending on whether you mean the PNG file, the time the image was
3772created in a non-PNG format, a still photo from which the image was
3773scanned, or possibly the subject matter itself. In order to facilitate
3774machine-readable dates, it is recommended that the "Creation Time"
3775tEXt chunk use RFC 1123 format dates (e.g. "22 May 1997 18:07:10 GMT"),
3776although this isn't a requirement. Unlike the tIME chunk, the
3777"Creation Time" tEXt chunk is not expected to be automatically changed
3778by the software. To facilitate the use of RFC 1123 dates, a function
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]3779png_convert_to_rfc1123_buffer(buffer, png_timep) is provided to
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3780convert from PNG time to an RFC 1123 format string. The caller must provide
3781a writeable buffer of at least 29 bytes.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3782
3783.SS Writing unknown chunks
3784
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3785You can use the png_set_unknown_chunks function to queue up private chunks
3786for writing. You give it a chunk name, location, raw data, and a size. You
3787also must use png_set_keep_unknown_chunks() to ensure that libpng will
3788handle them. That's all there is to it. The chunks will be written by the
3789next following png_write_info_before_PLTE, png_write_info, or png_write_end
3790function, depending upon the specified location. Any chunks previously
3791read into the info structure's unknown-chunk list will also be written out
3792in a sequence that satisfies the PNG specification's ordering rules.
3793
3794Here is an example of writing two private chunks, prVt and miNE:
3795
3796 #ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
3797 /* Set unknown chunk data */
3798 png_unknown_chunk unk_chunk[2];
3799 strcpy((char *) unk_chunk[0].name, "prVt";
3800 unk_chunk[0].data = (unsigned char *) "PRIVATE DATA";
3801 unk_chunk[0].size = strlen(unk_chunk[0].data)+1;
3802 unk_chunk[0].location = PNG_HAVE_IHDR;
3803 strcpy((char *) unk_chunk[1].name, "miNE";
3804 unk_chunk[1].data = (unsigned char *) "MY CHUNK DATA";
3805 unk_chunk[1].size = strlen(unk_chunk[0].data)+1;
3806 unk_chunk[1].location = PNG_AFTER_IDAT;
3807 png_set_unknown_chunks(write_ptr, write_info_ptr,
3808 unk_chunk, 2);
3809 /* Needed because miNE is not safe-to-copy */
3810 png_set_keep_unknown_chunks(png, PNG_HANDLE_CHUNK_ALWAYS,
3811 (png_bytep) "miNE", 1);
3812 # if PNG_LIBPNG_VER < 10600
3813 /* Deal with unknown chunk location bug in 1.5.x and earlier */
3814 png_set_unknown_chunk_location(png, info, 0, PNG_HAVE_IHDR);
3815 png_set_unknown_chunk_location(png, info, 1, PNG_AFTER_IDAT);
3816 # endif
3817 # if PNG_LIBPNG_VER < 10500
3818 /* PNG_AFTER_IDAT writes two copies of the chunk prior to libpng-1.5.0,
3819 * one before IDAT and another after IDAT, so don't use it; only use
3820 * PNG_HAVE_IHDR location. This call resets the location previously
3821 * set by assignment and png_set_unknown_chunk_location() for chunk 1.
3822 */
3823 png_set_unknown_chunk_location(png, info, 1, PNG_HAVE_IHDR);
3824 # endif
3825 #endif
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3826
3827.SS The high-level write interface
3828
3829At this point there are two ways to proceed; through the high-level
3830write interface, or through a sequence of low-level write operations.
3831You can use the high-level interface if your image data is present
3832in the info structure. All defined output
3833transformations are permitted, enabled by the following masks.
3834
3835 PNG_TRANSFORM_IDENTITY No transformation
3836 PNG_TRANSFORM_PACKING Pack 1, 2 and 4-bit samples
3837 PNG_TRANSFORM_PACKSWAP Change order of packed
3838 pixels to LSB first
3839 PNG_TRANSFORM_INVERT_MONO Invert monochrome images
3840 PNG_TRANSFORM_SHIFT Normalize pixels to the
3841 sBIT depth
3842 PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA
3843 to BGRA
3844 PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA
3845 to AG
3846 PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity
3847 to transparency
3848 PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]3849 PNG_TRANSFORM_STRIP_FILLER Strip out filler
3850 bytes (deprecated).
3851 PNG_TRANSFORM_STRIP_FILLER_BEFORE Strip out leading
3852 filler bytes
3853 PNG_TRANSFORM_STRIP_FILLER_AFTER Strip out trailing
3854 filler bytes
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3855
3856If you have valid image data in the info structure (you can use
3857png_set_rows() to put image data in the info structure), simply do this:
3858
3859 png_write_png(png_ptr, info_ptr, png_transforms, NULL)
3860
3861where png_transforms is an integer containing the bitwise OR of some set of
3862transformation flags. This call is equivalent to png_write_info(),
3863followed the set of transformations indicated by the transform mask,
3864then png_write_image(), and finally png_write_end().
3865
3866(The final parameter of this call is not yet used. Someday it might point
3867to transformation parameters required by some future output transform.)
3868
3869You must use png_transforms and not call any png_set_transform() functions
3870when you use png_write_png().
3871
3872.SS The low-level write interface
3873
3874If you are going the low-level route instead, you are now ready to
3875write all the file information up to the actual image data. You do
3876this with a call to png_write_info().
3877
3878 png_write_info(png_ptr, info_ptr);
3879
3880Note that there is one transformation you may need to do before
3881png_write_info(). In PNG files, the alpha channel in an image is the
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]3882level of opacity. If your data is supplied as a level of transparency,
3883you can invert the alpha channel before you write it, so that 0 is
3884fully transparent and 255 (in 8-bit or paletted images) or 65535
3885(in 16-bit images) is fully opaque, with
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3886
3887 png_set_invert_alpha(png_ptr);
3888
3889This must appear before png_write_info() instead of later with the
3890other transformations because in the case of paletted images the tRNS
3891chunk data has to be inverted before the tRNS chunk is written. If
3892your image is not a paletted image, the tRNS data (which in such cases
3893represents a single color to be rendered as transparent) won't need to
3894be changed, and you can safely do this transformation after your
3895png_write_info() call.
3896
3897If you need to write a private chunk that you want to appear before
3898the PLTE chunk when PLTE is present, you can write the PNG info in
3899two steps, and insert code to write your own chunk between them:
3900
3901 png_write_info_before_PLTE(png_ptr, info_ptr);
3902 png_set_unknown_chunks(png_ptr, info_ptr, ...);
3903 png_write_info(png_ptr, info_ptr);
3904
3905After you've written the file information, you can set up the library
3906to handle any special transformations of the image data. The various
3907ways to transform the data will be described in the order that they
3908should occur. This is important, as some of these change the color
3909type and/or bit depth of the data, and some others only work on
3910certain color types and bit depths. Even though each transformation
3911checks to see if it has data that it can do something with, you should
3912make sure to only enable a transformation if it will be valid for the
3913data. For example, don't swap red and blue on grayscale data.
3914
3915PNG files store RGB pixels packed into 3 or 6 bytes. This code tells
3916the library to strip input data that has 4 or 8 bytes per pixel down
3917to 3 or 6 bytes (or strip 2 or 4-byte grayscale+filler data to 1 or 2
3918bytes per pixel).
3919
3920 png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
3921
3922where the 0 is unused, and the location is either PNG_FILLER_BEFORE or
3923PNG_FILLER_AFTER, depending upon whether the filler byte in the pixel
3924is stored XRGB or RGBX.
3925
3926PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
3927they can, resulting in, for example, 8 pixels per byte for 1 bit files.
3928If the data is supplied at 1 pixel per byte, use this code, which will
3929correctly pack the pixels into a single byte:
3930
3931 png_set_packing(png_ptr);
3932
3933PNG files reduce possible bit depths to 1, 2, 4, 8, and 16. If your
3934data is of another bit depth, you can write an sBIT chunk into the
3935file so that decoders can recover the original data if desired.
3936
3937 /* Set the true bit depth of the image data */
3938 if (color_type & PNG_COLOR_MASK_COLOR)
3939 {
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3940 sig_bit.red = true_bit_depth;
3941 sig_bit.green = true_bit_depth;
3942 sig_bit.blue = true_bit_depth;
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3943 }
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3944
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3945 else
3946 {
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3947 sig_bit.gray = true_bit_depth;
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3948 }
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3949
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3950 if (color_type & PNG_COLOR_MASK_ALPHA)
3951 {
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3952 sig_bit.alpha = true_bit_depth;
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3953 }
3954
3955 png_set_sBIT(png_ptr, info_ptr, &sig_bit);
3956
3957If the data is stored in the row buffer in a bit depth other than
3958one supported by PNG (e.g. 3 bit data in the range 0-7 for a 4-bit PNG),
3959this will scale the values to appear to be the correct bit depth as
3960is required by PNG.
3961
3962 png_set_shift(png_ptr, &sig_bit);
3963
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3964PNG files store 16-bit pixels in network byte order (big-endian,
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3965ie. most significant bits first). This code would be used if they are
3966supplied the other way (little-endian, i.e. least significant bits
3967first, the way PCs store them):
3968
3969 if (bit_depth > 8)
3970 png_set_swap(png_ptr);
3971
3972If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you
3973need to change the order the pixels are packed into bytes, you can use:
3974
3975 if (bit_depth < 8)
3976 png_set_packswap(png_ptr);
3977
3978PNG files store 3 color pixels in red, green, blue order. This code
3979would be used if they are supplied as blue, green, red:
3980
3981 png_set_bgr(png_ptr);
3982
3983PNG files describe monochrome as black being zero and white being
3984one. This code would be used if the pixels are supplied with this reversed
3985(black being one and white being zero):
3986
3987 png_set_invert_mono(png_ptr);
3988
3989Finally, you can write your own transformation function if none of
3990the existing ones meets your needs. This is done by setting a callback
3991with
3992
3993 png_set_write_user_transform_fn(png_ptr,
3994 write_transform_fn);
3995
3996You must supply the function
3997
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]3998 void write_transform_fn(png_structp png_ptr, png_row_infop
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]3999 row_info, png_bytep data)
4000
4001See pngtest.c for a working example. Your function will be called
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4002before any of the other transformations are processed. If supported
4003libpng also supplies an information routine that may be called from
4004your callback:
4005
4006 png_get_current_row_number(png_ptr);
4007 png_get_current_pass_number(png_ptr);
4008
4009This returns the current row passed to the transform. With interlaced
4010images the value returned is the row in the input sub-image image. Use
4011PNG_ROW_FROM_PASS_ROW(row, pass) and PNG_COL_FROM_PASS_COL(col, pass) to
4012find the output pixel (x,y) given an interlaced sub-image pixel (row,col,pass).
4013
4014The discussion of interlace handling above contains more information on how to
4015use these values.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4016
4017You can also set up a pointer to a user structure for use by your
4018callback function.
4019
4020 png_set_user_transform_info(png_ptr, user_ptr, 0, 0);
4021
4022The user_channels and user_depth parameters of this function are ignored
4023when writing; you can set them to zero as shown.
4024
4025You can retrieve the pointer via the function png_get_user_transform_ptr().
4026For example:
4027
4028 voidp write_user_transform_ptr =
4029 png_get_user_transform_ptr(png_ptr);
4030
4031It is possible to have libpng flush any pending output, either manually,
4032or automatically after a certain number of lines have been written. To
4033flush the output stream a single time call:
4034
4035 png_write_flush(png_ptr);
4036
4037and to have libpng flush the output stream periodically after a certain
4038number of scanlines have been written, call:
4039
4040 png_set_flush(png_ptr, nrows);
4041
4042Note that the distance between rows is from the last time png_write_flush()
4043was called, or the first row of the image if it has never been called.
4044So if you write 50 lines, and then png_set_flush 25, it will flush the
4045output on the next scanline, and every 25 lines thereafter, unless
4046png_write_flush() is called before 25 more lines have been written.
4047If nrows is too small (less than about 10 lines for a 640 pixel wide
4048RGB image) the image compression may decrease noticeably (although this
4049may be acceptable for real-time applications). Infrequent flushing will
4050only degrade the compression performance by a few percent over images
4051that do not use flushing.
4052
4053.SS Writing the image data
4054
4055That's it for the transformations. Now you can write the image data.
4056The simplest way to do this is in one function call. If you have the
4057whole image in memory, you can just call png_write_image() and libpng
4058will write the image. You will need to pass in an array of pointers to
4059each row. This function automatically handles interlacing, so you don't
4060need to call png_set_interlace_handling() or call this function multiple
4061times, or any of that other stuff necessary with png_write_rows().
4062
4063 png_write_image(png_ptr, row_pointers);
4064
4065where row_pointers is:
4066
4067 png_byte *row_pointers[height];
4068
4069You can point to void or char or whatever you use for pixels.
4070
4071If you don't want to write the whole image at once, you can
4072use png_write_rows() instead. If the file is not interlaced,
4073this is simple:
4074
4075 png_write_rows(png_ptr, row_pointers,
4076 number_of_rows);
4077
4078row_pointers is the same as in the png_write_image() call.
4079
4080If you are just writing one row at a time, you can do this with
4081a single row_pointer instead of an array of row_pointers:
4082
4083 png_bytep row_pointer = row;
4084
4085 png_write_row(png_ptr, row_pointer);
4086
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]4087When the file is interlaced, things can get a good deal more complicated.
4088The only currently (as of the PNG Specification version 1.2, dated July
40891999) defined interlacing scheme for PNG files is the "Adam7" interlace
4090scheme, that breaks down an image into seven smaller images of varying
4091size. libpng will build these images for you, or you can do them
4092yourself. If you want to build them yourself, see the PNG specification
4093for details of which pixels to write when.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4094
4095If you don't want libpng to handle the interlacing details, just
4096use png_set_interlace_handling() and call png_write_rows() the
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4097correct number of times to write all the sub-images
4098(png_set_interlace_handling() returns the number of sub-images.)
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4099
4100If you want libpng to build the sub-images, call this before you start
4101writing any rows:
4102
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4103 number_of_passes = png_set_interlace_handling(png_ptr);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4104
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]4105This will return the number of passes needed. Currently, this is seven,
4106but may change if another interlace type is added.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4107
4108Then write the complete image number_of_passes times.
4109
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4110 png_write_rows(png_ptr, row_pointers, number_of_rows);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4111
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4112Think carefully before you write an interlaced image. Typically code that
4113reads such images reads all the image data into memory, uncompressed, before
4114doing any processing. Only code that can display an image on the fly can
4115take advantage of the interlacing and even then the image has to be exactly
4116the correct size for the output device, because scaling an image requires
4117adjacent pixels and these are not available until all the passes have been
4118read.
4119
4120If you do write an interlaced image you will hardly ever need to handle
4121the interlacing yourself. Call png_set_interlace_handling() and use the
4122approach described above.
4123
4124The only time it is conceivable that you will really need to write an
4125interlaced image pass-by-pass is when you have read one pass by pass and
4126made some pixel-by-pixel transformation to it, as described in the read
4127code above. In this case use the PNG_PASS_ROWS and PNG_PASS_COLS macros
4128to determine the size of each sub-image in turn and simply write the rows
4129you obtained from the read code.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4130
4131.SS Finishing a sequential write
4132
4133After you are finished writing the image, you should finish writing
4134the file. If you are interested in writing comments or time, you should
4135pass an appropriately filled png_info pointer. If you are not interested,
4136you can pass NULL.
4137
4138 png_write_end(png_ptr, info_ptr);
4139
4140When you are done, you can free all memory used by libpng like this:
4141
4142 png_destroy_write_struct(&png_ptr, &info_ptr);
4143
4144It is also possible to individually free the info_ptr members that
4145point to libpng-allocated storage with the following function:
4146
4147 png_free_data(png_ptr, info_ptr, mask, seq)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4148
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4149 mask - identifies data to be freed, a mask
4150 containing the bitwise OR of one or
4151 more of
4152 PNG_FREE_PLTE, PNG_FREE_TRNS,
4153 PNG_FREE_HIST, PNG_FREE_ICCP,
4154 PNG_FREE_PCAL, PNG_FREE_ROWS,
4155 PNG_FREE_SCAL, PNG_FREE_SPLT,
4156 PNG_FREE_TEXT, PNG_FREE_UNKN,
4157 or simply PNG_FREE_ALL
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4158
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4159 seq - sequence number of item to be freed
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]4160 (\-1 for all items)
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4161
4162This function may be safely called when the relevant storage has
4163already been freed, or has not yet been allocated, or was allocated
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]4164by the user and not by libpng, and will in those cases do nothing.
4165The "seq" parameter is ignored if only one item of the selected data
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]4166type, such as PLTE, is allowed. If "seq" is not \-1, and multiple items
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]4167are allowed for the data type identified in the mask, such as text or
4168sPLT, only the n'th item in the structure is freed, where n is "seq".
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4169
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]4170If you allocated data such as a palette that you passed in to libpng
4171with png_set_*, you must not free it until just before the call to
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4172png_destroy_write_struct().
4173
4174The default behavior is only to free data that was allocated internally
4175by libpng. This can be changed, so that libpng will not free the data,
4176or so that it will free data that was allocated by the user with png_malloc()
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4177or png_calloc() and passed in via a png_set_*() function, with
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4178
4179 png_data_freer(png_ptr, info_ptr, freer, mask)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4180
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4181 freer - one of
4182 PNG_DESTROY_WILL_FREE_DATA
4183 PNG_SET_WILL_FREE_DATA
4184 PNG_USER_WILL_FREE_DATA
4185
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4186 mask - which data elements are affected
4187 same choices as in png_free_data()
4188
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4189For example, to transfer responsibility for some data from a read structure
4190to a write structure, you could use
4191
4192 png_data_freer(read_ptr, read_info_ptr,
4193 PNG_USER_WILL_FREE_DATA,
4194 PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4195
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4196 png_data_freer(write_ptr, write_info_ptr,
4197 PNG_DESTROY_WILL_FREE_DATA,
4198 PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST)
4199
4200thereby briefly reassigning responsibility for freeing to the user but
4201immediately afterwards reassigning it once more to the write_destroy
4202function. Having done this, it would then be safe to destroy the read
4203structure and continue to use the PLTE, tRNS, and hIST data in the write
4204structure.
4205
4206This function only affects data that has already been allocated.
4207You can call this function before calling after the png_set_*() functions
4208to control whether the user or png_destroy_*() is supposed to free the data.
4209When the user assumes responsibility for libpng-allocated data, the
4210application must use
4211png_free() to free it, and when the user transfers responsibility to libpng
4212for data that the user has allocated, the user must have used png_malloc()
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4213or png_calloc() to allocate it.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4214
4215If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword
4216separately, do not transfer responsibility for freeing text_ptr to libpng,
4217because when libpng fills a png_text structure it combines these members with
4218the key member, and png_free_data() will free only text_ptr.key. Similarly,
4219if you transfer responsibility for free'ing text_ptr from libpng to your
4220application, your application must not separately free those members.
4221For a more compact example of writing a PNG image, see the file example.c.
4222
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4223.SH V. Simplified API
4224
4225The simplified API, which became available in libpng-1.6.0, hides the details
4226of both libpng and the PNG file format itself.
4227It allows PNG files to be read into a very limited number of
4228in-memory bitmap formats or to be written from the same formats. If these
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]4229formats do not accommodate your needs then you can, and should, use the more
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4230sophisticated APIs above - these support a wide variety of in-memory formats
4231and a wide variety of sophisticated transformations to those formats as well
4232as a wide variety of APIs to manipulate ancilliary information.
4233
4234To read a PNG file using the simplified API:
4235
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4236 1) Declare a 'png_image' structure (see below) on the stack, set the
4237 version field to PNG_IMAGE_VERSION and the 'opaque' pointer to NULL
4238 (this is REQUIRED, your program may crash if you don't do it.)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4239
4240 2) Call the appropriate png_image_begin_read... function.
4241
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4242 3) Set the png_image 'format' member to the required sample format.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4243
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4244 4) Allocate a buffer for the image and, if required, the color-map.
4245
4246 5) Call png_image_finish_read to read the image and, if required, the
4247 color-map into your buffers.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4248
4249There are no restrictions on the format of the PNG input itself; all valid
4250color types, bit depths, and interlace methods are acceptable, and the
4251input image is transformed as necessary to the requested in-memory format
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4252during the png_image_finish_read() step. The only caveat is that if you
4253request a color-mapped image from a PNG that is full-color or makes
4254complex use of an alpha channel the transformation is extremely lossy and the
4255result may look terrible.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4256
4257To write a PNG file using the simplified API:
4258
4259 1) Declare a 'png_image' structure on the stack and memset()
4260 it to all zero.
4261
4262 2) Initialize the members of the structure that describe the
4263 image, setting the 'format' member to the format of the
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4264 image samples.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4265
4266 3) Call the appropriate png_image_write... function with a
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4267 pointer to the image and, if necessary, the color-map to write
4268 the PNG data.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4269
4270png_image is a structure that describes the in-memory format of an image
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4271when it is being read or defines the in-memory format of an image that you
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4272need to write. The "png_image" structure contains the following members:
4273
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4274 png_controlp opaque Initialize to NULL, free with png_image_free
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4275 png_uint_32 version Set to PNG_IMAGE_VERSION
4276 png_uint_32 width Image width in pixels (columns)
4277 png_uint_32 height Image height in pixels (rows)
4278 png_uint_32 format Image format as defined below
4279 png_uint_32 flags A bit mask containing informational flags
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4280 png_uint_32 colormap_entries; Number of entries in the color-map
4281 png_uint_32 warning_or_error;
4282 char message[64];
4283
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4284In the event of an error or warning the "warning_or_error"
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4285field will be set to a non-zero value and the 'message' field will contain
4286a '\0' terminated string with the libpng error or warning message. If both
4287warnings and an error were encountered, only the error is recorded. If there
4288are multiple warnings, only the first one is recorded.
4289
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4290The upper 30 bits of the "warning_or_error" value are reserved; the low two
4291bits contain a two bit code such that a value more than 1 indicates a failure
4292in the API just called:
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4293
4294 0 - no warning or error
4295 1 - warning
4296 2 - error
4297 3 - error preceded by warning
4298
4299The pixels (samples) of the image have one to four channels whose components
4300have original values in the range 0 to 1.0:
4301
4302 1: A single gray or luminance channel (G).
4303 2: A gray/luminance channel and an alpha channel (GA).
4304 3: Three red, green, blue color channels (RGB).
4305 4: Three color channels and an alpha channel (RGBA).
4306
4307The channels are encoded in one of two ways:
4308
4309 a) As a small integer, value 0..255, contained in a single byte. For the
4310alpha channel the original value is simply value/255. For the color or
4311luminance channels the value is encoded according to the sRGB specification
4312and matches the 8-bit format expected by typical display devices.
4313
4314The color/gray channels are not scaled (pre-multiplied) by the alpha
4315channel and are suitable for passing to color management software.
4316
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4317 b) As a value in the range 0..65535, contained in a 2-byte integer, in
4318the native byte order of the platform on which the application is running.
4319All channels can be converted to the original value by dividing by 65535; all
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4320channels are linear. Color channels use the RGB encoding (RGB end-points) of
4321the sRGB specification. This encoding is identified by the
4322PNG_FORMAT_FLAG_LINEAR flag below.
4323
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4324When the simplified API needs to convert between sRGB and linear colorspaces,
4325the actual sRGB transfer curve defined in the sRGB specification (see the
4326article at http://en.wikipedia.org/wiki/SRGB) is used, not the gamma=1/2.2
4327approximation used elsewhere in libpng.
4328
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4329When an alpha channel is present it is expected to denote pixel coverage
4330of the color or luminance channels and is returned as an associated alpha
4331channel: the color/gray channels are scaled (pre-multiplied) by the alpha
4332value.
4333
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4334The samples are either contained directly in the image data, between 1 and 8
4335bytes per pixel according to the encoding, or are held in a color-map indexed
4336by bytes in the image data. In the case of a color-map the color-map entries
4337are individual samples, encoded as above, and the image data has one byte per
4338pixel to select the relevant sample from the color-map.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4339
4340PNG_FORMAT_*
4341
4342The #defines to be used in png_image::format. Each #define identifies a
4343particular layout of channel data and, if present, alpha values. There are
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4344separate defines for each of the two component encodings.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4345
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4346A format is built up using single bit flag values. All combinations are
4347valid. Formats can be built up from the flag values or you can use one of
4348the predefined values below. When testing formats always use the FORMAT_FLAG
4349macros to test for individual features - future versions of the library may
4350add new flags.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4351
4352When reading or writing color-mapped images the format should be set to the
4353format of the entries in the color-map then png_image_{read,write}_colormap
4354called to read or write the color-map and set the format correctly for the
4355image data. Do not set the PNG_FORMAT_FLAG_COLORMAP bit directly!
4356
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4357NOTE: libpng can be built with particular features disabled. If you see
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4358compiler errors because the definition of one of the following flags has been
4359compiled out it is because libpng does not have the required support. It is
4360possible, however, for the libpng configuration to enable the format on just
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4361read or just write; in that case you may see an error at run time.
4362You can guard against this by checking for the definition of the
4363appropriate "_SUPPORTED" macro, one of:
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4364
4365 PNG_SIMPLIFIED_{READ,WRITE}_{BGR,AFIRST}_SUPPORTED
4366
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4367 PNG_FORMAT_FLAG_ALPHA format with an alpha channel
4368 PNG_FORMAT_FLAG_COLOR color format: otherwise grayscale
4369 PNG_FORMAT_FLAG_LINEAR 2-byte channels else 1-byte
4370 PNG_FORMAT_FLAG_COLORMAP image data is color-mapped
4371 PNG_FORMAT_FLAG_BGR BGR colors, else order is RGB
4372 PNG_FORMAT_FLAG_AFIRST alpha channel comes first
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4373
4374Supported formats are as follows. Future versions of libpng may support more
4375formats; for compatibility with older versions simply check if the format
4376macro is defined using #ifdef. These defines describe the in-memory layout
4377of the components of the pixels of the image.
4378
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4379First the single byte (sRGB) formats:
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4380
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4381 PNG_FORMAT_GRAY
4382 PNG_FORMAT_GA
4383 PNG_FORMAT_AG
4384 PNG_FORMAT_RGB
4385 PNG_FORMAT_BGR
4386 PNG_FORMAT_RGBA
4387 PNG_FORMAT_ARGB
4388 PNG_FORMAT_BGRA
4389 PNG_FORMAT_ABGR
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4390
4391Then the linear 2-byte formats. When naming these "Y" is used to
4392indicate a luminance (gray) channel. The component order within the pixel
4393is always the same - there is no provision for swapping the order of the
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4394components in the linear format. The components are 16-bit integers in
4395the native byte order for your platform, and there is no provision for
4396swapping the bytes to a different endian condition.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4397
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4398 PNG_FORMAT_LINEAR_Y
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4399 PNG_FORMAT_LINEAR_Y_ALPHA
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4400 PNG_FORMAT_LINEAR_RGB
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4401 PNG_FORMAT_LINEAR_RGB_ALPHA
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4402
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4403With color-mapped formats the image data is one byte for each pixel. The byte
4404is an index into the color-map which is formatted as above. To obtain a
4405color-mapped format it is sufficient just to add the PNG_FOMAT_FLAG_COLORMAP
4406to one of the above definitions, or you can use one of the definitions below.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4407
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4408 PNG_FORMAT_RGB_COLORMAP
4409 PNG_FORMAT_BGR_COLORMAP
4410 PNG_FORMAT_RGBA_COLORMAP
4411 PNG_FORMAT_ARGB_COLORMAP
4412 PNG_FORMAT_BGRA_COLORMAP
4413 PNG_FORMAT_ABGR_COLORMAP
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4414
4415PNG_IMAGE macros
4416
4417These are convenience macros to derive information from a png_image
4418structure. The PNG_IMAGE_SAMPLE_ macros return values appropriate to the
4419actual image sample values - either the entries in the color-map or the
4420pixels in the image. The PNG_IMAGE_PIXEL_ macros return corresponding values
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4421for the pixels and will always return 1 for color-mapped formats. The
4422remaining macros return information about the rows in the image and the
4423complete image.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4424
4425NOTE: All the macros that take a png_image::format parameter are compile time
4426constants if the format parameter is, itself, a constant. Therefore these
4427macros can be used in array declarations and case labels where required.
4428Similarly the macros are also pre-processor constants (sizeof is not used) so
4429they can be used in #if tests.
4430
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4431 PNG_IMAGE_SAMPLE_CHANNELS(fmt)
4432 Returns the total number of channels in a given format: 1..4
4433
4434 PNG_IMAGE_SAMPLE_COMPONENT_SIZE(fmt)
4435 Returns the size in bytes of a single component of a pixel or color-map
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4436 entry (as appropriate) in the image: 1 or 2.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4437
4438 PNG_IMAGE_SAMPLE_SIZE(fmt)
4439 This is the size of the sample data for one sample. If the image is
4440 color-mapped it is the size of one color-map entry (and image pixels are
4441 one byte in size), otherwise it is the size of one image pixel.
4442
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4443 PNG_IMAGE_MAXIMUM_COLORMAP_COMPONENTS(fmt)
4444 The maximum size of the color-map required by the format expressed in a
4445 count of components. This can be used to compile-time allocate a
4446 color-map:
4447
4448 png_uint_16 colormap[PNG_IMAGE_MAXIMUM_COLORMAP_COMPONENTS(linear_fmt)];
4449
4450 png_byte colormap[PNG_IMAGE_MAXIMUM_COLORMAP_COMPONENTS(sRGB_fmt)];
4451
4452 Alternatively use the PNG_IMAGE_COLORMAP_SIZE macro below to use the
4453 information from one of the png_image_begin_read_ APIs and dynamically
4454 allocate the required memory.
4455
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4456 PNG_IMAGE_COLORMAP_SIZE(fmt)
4457 The size of the color-map required by the format; this is the size of the
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4458 color-map buffer passed to the png_image_{read,write}_colormap APIs. It is
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4459 a fixed number determined by the format so can easily be allocated on the
4460 stack if necessary.
4461
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4462Corresponding information about the pixels
4463
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4464 PNG_IMAGE_PIXEL_CHANNELS(fmt)
4465 The number of separate channels (components) in a pixel; 1 for a
4466 color-mapped image.
4467
4468 PNG_IMAGE_PIXEL_COMPONENT_SIZE(fmt)\
4469 The size, in bytes, of each component in a pixel; 1 for a color-mapped
4470 image.
4471
4472 PNG_IMAGE_PIXEL_SIZE(fmt)
4473 The size, in bytes, of a complete pixel; 1 for a color-mapped image.
4474
4475Information about the whole row, or whole image
4476
4477 PNG_IMAGE_ROW_STRIDE(image)
4478 Returns the total number of components in a single row of the image; this
4479 is the minimum 'row stride', the minimum count of components between each
4480 row. For a color-mapped image this is the minimum number of bytes in a
4481 row.
4482
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4483 If you need the stride measured in bytes, row_stride_bytes is
4484 PNG_IMAGE_ROW_STRIDE(image) * PNG_IMAGE_PIXEL_COMPONENT_SIZE(fmt)
4485 plus any padding bytes that your application might need, for example
4486 to start the next row on a 4-byte boundary.
4487
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4488 PNG_IMAGE_BUFFER_SIZE(image, row_stride)
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4489 Return the size, in bytes, of an image buffer given a png_image and a row
4490 stride - the number of components to leave space for in each row.
4491
4492 PNG_IMAGE_SIZE(image)
4493 Return the size, in bytes, of the image in memory given just a png_image;
4494 the row stride is the minimum stride required for the image.
4495
4496 PNG_IMAGE_COLORMAP_SIZE(image)
4497 Return the size, in bytes, of the color-map of this image. If the image
4498 format is not a color-map format this will return a size sufficient for
4499 256 entries in the given format; check PNG_FORMAT_FLAG_COLORMAP if
4500 you don't want to allocate a color-map in this case.
4501
4502PNG_IMAGE_FLAG_*
4503
4504Flags containing additional information about the image are held in
4505the 'flags' field of png_image.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4506
4507 PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB == 0x01
4508 This indicates the the RGB values of the in-memory bitmap do not
4509 correspond to the red, green and blue end-points defined by sRGB.
4510
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4511 PNG_IMAGE_FLAG_FAST == 0x02
4512 On write emphasise speed over compression; the resultant PNG file will be
4513 larger but will be produced significantly faster, particular for large
4514 images. Do not use this option for images which will be distributed, only
4515 used it when producing intermediate files that will be read back in
4516 repeatedly. For a typical 24-bit image the option will double the read
4517 speed at the cost of increasing the image size by 25%, however for many
4518 more compressible images the PNG file can be 10 times larger with only a
4519 slight speed gain.
4520
4521 PNG_IMAGE_FLAG_16BIT_sRGB == 0x04
4522 On read if the image is a 16-bit per component image and there is no gAMA
4523 or sRGB chunk assume that the components are sRGB encoded. Notice that
4524 images output by the simplified API always have gamma information; setting
4525 this flag only affects the interpretation of 16-bit images from an
4526 external source. It is recommended that the application expose this flag
4527 to the user; the user can normally easily recognize the difference between
4528 linear and sRGB encoding. This flag has no effect on write - the data
4529 passed to the write APIs must have the correct encoding (as defined
4530 above.)
4531
4532 If the flag is not set (the default) input 16-bit per component data is
4533 assumed to be linear.
4534
4535 NOTE: the flag can only be set after the png_image_begin_read_ call,
4536 because that call initializes the 'flags' field.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4537
4538READ APIs
4539
4540 The png_image passed to the read APIs must have been initialized by setting
4541 the png_controlp field 'opaque' to NULL (or, better, memset the whole thing.)
4542
4543 int png_image_begin_read_from_file( png_imagep image,
4544 const char *file_name)
4545
4546 The named file is opened for read and the image header
4547 is filled in from the PNG header in the file.
4548
4549 int png_image_begin_read_from_stdio (png_imagep image,
4550 FILE* file)
4551
4552 The PNG header is read from the stdio FILE object.
4553
4554 int png_image_begin_read_from_memory(png_imagep image,
4555 png_const_voidp memory, png_size_t size)
4556
4557 The PNG header is read from the given memory buffer.
4558
4559 int png_image_finish_read(png_imagep image,
4560 png_colorp background, void *buffer,
4561 png_int_32 row_stride, void *colormap));
4562
4563 Finish reading the image into the supplied buffer and
4564 clean up the png_image structure.
4565
4566 row_stride is the step, in png_byte or png_uint_16 units
4567 as appropriate, between adjacent rows. A positive stride
4568 indicates that the top-most row is first in the buffer -
4569 the normal top-down arrangement. A negative stride
4570 indicates that the bottom-most row is first in the buffer.
4571
4572 background need only be supplied if an alpha channel must
4573 be removed from a png_byte format and the removal is to be
4574 done by compositing on a solid color; otherwise it may be
4575 NULL and any composition will be done directly onto the
4576 buffer. The value is an sRGB color to use for the
4577 background, for grayscale output the green channel is used.
4578
4579 For linear output removing the alpha channel is always done
4580 by compositing on black.
4581
4582 void png_image_free(png_imagep image)
4583
4584 Free any data allocated by libpng in image->opaque,
4585 setting the pointer to NULL. May be called at any time
4586 after the structure is initialized.
4587
4588When the simplified API needs to convert between sRGB and linear colorspaces,
4589the actual sRGB transfer curve defined in the sRGB specification (see the
4590article at http://en.wikipedia.org/wiki/SRGB) is used, not the gamma=1/2.2
4591approximation used elsewhere in libpng.
4592
4593WRITE APIS
4594
4595For write you must initialize a png_image structure to describe the image to
4596be written:
4597
4598 version: must be set to PNG_IMAGE_VERSION
4599 opaque: must be initialized to NULL
4600 width: image width in pixels
4601 height: image height in rows
4602 format: the format of the data you wish to write
4603 flags: set to 0 unless one of the defined flags applies; set
4604 PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB for color format images
4605 where the RGB values do not correspond to the colors in sRGB.
4606 colormap_entries: set to the number of entries in the color-map (0 to 256)
4607
4608 int png_image_write_to_file, (png_imagep image,
4609 const char *file, int convert_to_8bit, const void *buffer,
4610 png_int_32 row_stride, const void *colormap));
4611
4612 Write the image to the named file.
4613
4614 int png_image_write_to_stdio(png_imagep image, FILE *file,
4615 int convert_to_8_bit, const void *buffer,
4616 png_int_32 row_stride, const void *colormap)
4617
4618 Write the image to the given (FILE*).
4619
4620With all write APIs if image is in one of the linear formats with
4621(png_uint_16) data then setting convert_to_8_bit will cause the output to be
4622a (png_byte) PNG gamma encoded according to the sRGB specification, otherwise
4623a 16-bit linear encoded PNG file is written.
4624
4625With all APIs row_stride is handled as in the read APIs - it is the spacing
4626from one row to the next in component sized units (float) and if negative
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4627indicates a bottom-up row layout in the buffer. If you pass zero, libpng will
4628calculate the row_stride for you from the width and number of channels.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4629
4630Note that the write API does not support interlacing, sub-8-bit pixels,
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4631indexed (paletted) images, or most ancillary chunks.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4632
4633.SH VI. Modifying/Customizing libpng
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4634
4635There are two issues here. The first is changing how libpng does
4636standard things like memory allocation, input/output, and error handling.
4637The second deals with more complicated things like adding new chunks,
4638adding new transformations, and generally changing how libpng works.
4639Both of those are compile-time issues; that is, they are generally
4640determined at the time the code is written, and there is rarely a need
4641to provide the user with a means of changing them.
4642
4643Memory allocation, input/output, and error handling
4644
4645All of the memory allocation, input/output, and error handling in libpng
4646goes through callbacks that are user-settable. The default routines are
4647in pngmem.c, pngrio.c, pngwio.c, and pngerror.c, respectively. To change
4648these functions, call the appropriate png_set_*_fn() function.
4649
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]4650Memory allocation is done through the functions png_malloc(), png_calloc(),
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4651and png_free(). The png_malloc() and png_free() functions currently just
4652call the standard C functions and png_calloc() calls png_malloc() and then
4653clears the newly allocated memory to zero; note that png_calloc(png_ptr, size)
4654is not the same as the calloc(number, size) function provided by stdlib.h.
4655There is limited support for certain systems with segmented memory
4656architectures and the types of pointers declared by png.h match this; you
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4657will have to use appropriate pointers in your application. If you prefer
4658to use a different method of allocating and freeing data, you can use
4659png_create_read_struct_2() or png_create_write_struct_2() to register your
4660own functions as described above. These functions also provide a void
4661pointer that can be retrieved via
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4662
4663 mem_ptr=png_get_mem_ptr(png_ptr);
4664
4665Your replacement memory functions must have prototypes as follows:
4666
4667 png_voidp malloc_fn(png_structp png_ptr,
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4668 png_alloc_size_t size);
4669
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4670 void free_fn(png_structp png_ptr, png_voidp ptr);
4671
4672Your malloc_fn() must return NULL in case of failure. The png_malloc()
4673function will normally call png_error() if it receives a NULL from the
4674system memory allocator or from your replacement malloc_fn().
4675
4676Your free_fn() will never be called with a NULL ptr, since libpng's
4677png_free() checks for NULL before calling free_fn().
4678
4679Input/Output in libpng is done through png_read() and png_write(),
4680which currently just call fread() and fwrite(). The FILE * is stored in
4681png_struct and is initialized via png_init_io(). If you wish to change
4682the method of I/O, the library supplies callbacks that you can set
4683through the function png_set_read_fn() and png_set_write_fn() at run
4684time, instead of calling the png_init_io() function. These functions
4685also provide a void pointer that can be retrieved via the function
4686png_get_io_ptr(). For example:
4687
4688 png_set_read_fn(png_structp read_ptr,
4689 voidp read_io_ptr, png_rw_ptr read_data_fn)
4690
4691 png_set_write_fn(png_structp write_ptr,
4692 voidp write_io_ptr, png_rw_ptr write_data_fn,
4693 png_flush_ptr output_flush_fn);
4694
4695 voidp read_io_ptr = png_get_io_ptr(read_ptr);
4696 voidp write_io_ptr = png_get_io_ptr(write_ptr);
4697
4698The replacement I/O functions must have prototypes as follows:
4699
4700 void user_read_data(png_structp png_ptr,
4701 png_bytep data, png_size_t length);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4702
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4703 void user_write_data(png_structp png_ptr,
4704 png_bytep data, png_size_t length);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4705
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4706 void user_flush_data(png_structp png_ptr);
4707
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]4708The user_read_data() function is responsible for detecting and
4709handling end-of-data errors.
4710
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4711Supplying NULL for the read, write, or flush functions sets them back
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]4712to using the default C stream functions, which expect the io_ptr to
4713point to a standard *FILE structure. It is probably a mistake
4714to use NULL for one of write_data_fn and output_flush_fn but not both
4715of them, unless you have built libpng with PNG_NO_WRITE_FLUSH defined.
4716It is an error to read from a write stream, and vice versa.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4717
4718Error handling in libpng is done through png_error() and png_warning().
4719Errors handled through png_error() are fatal, meaning that png_error()
4720should never return to its caller. Currently, this is handled via
4721setjmp() and longjmp() (unless you have compiled libpng with
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4722PNG_NO_SETJMP, in which case it is handled via PNG_ABORT()),
4723but you could change this to do things like exit() if you should wish,
4724as long as your function does not return.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4725
4726On non-fatal errors, png_warning() is called
4727to print a warning message, and then control returns to the calling code.
4728By default png_error() and png_warning() print a message on stderr via
4729fprintf() unless the library is compiled with PNG_NO_CONSOLE_IO defined
4730(because you don't want the messages) or PNG_NO_STDIO defined (because
4731fprintf() isn't available). If you wish to change the behavior of the error
4732functions, you will need to set up your own message callbacks. These
4733functions are normally supplied at the time that the png_struct is created.
4734It is also possible to redirect errors and warnings to your own replacement
4735functions after png_create_*_struct() has been called by calling:
4736
4737 png_set_error_fn(png_structp png_ptr,
4738 png_voidp error_ptr, png_error_ptr error_fn,
4739 png_error_ptr warning_fn);
4740
4741 png_voidp error_ptr = png_get_error_ptr(png_ptr);
4742
4743If NULL is supplied for either error_fn or warning_fn, then the libpng
4744default function will be used, calling fprintf() and/or longjmp() if a
4745problem is encountered. The replacement error functions should have
4746parameters as follows:
4747
4748 void user_error_fn(png_structp png_ptr,
4749 png_const_charp error_msg);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4750
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4751 void user_warning_fn(png_structp png_ptr,
4752 png_const_charp warning_msg);
4753
4754The motivation behind using setjmp() and longjmp() is the C++ throw and
4755catch exception handling methods. This makes the code much easier to write,
4756as there is no need to check every return code of every function call.
4757However, there are some uncertainties about the status of local variables
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]4758after a longjmp, so the user may want to be careful about doing anything
4759after setjmp returns non-zero besides returning itself. Consult your
4760compiler documentation for more details. For an alternative approach, you
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4761may wish to use the "cexcept" facility (see http://cexcept.sourceforge.net),
4762which is illustrated in pngvalid.c and in contrib/visupng.
4763
4764Beginning in libpng-1.4.0, the png_set_benign_errors() API became available.
4765You can use this to handle certain errors (normally handled as errors)
4766as warnings.
4767
4768 png_set_benign_errors (png_ptr, int allowed);
4769
4770 allowed: 0: treat png_benign_error() as an error.
4771 1: treat png_benign_error() as a warning.
4772
4773As of libpng-1.6.0, the default condition is to treat benign errors as
4774warnings while reading and as errors while writing.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4775
4776.SS Custom chunks
4777
4778If you need to read or write custom chunks, you may need to get deeper
4779into the libpng code. The library now has mechanisms for storing
4780and writing chunks of unknown type; you can even declare callbacks
4781for custom chunks. However, this may not be good enough if the
4782library code itself needs to know about interactions between your
4783chunk and existing `intrinsic' chunks.
4784
4785If you need to write a new intrinsic chunk, first read the PNG
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]4786specification. Acquire a first level of understanding of how it works.
4787Pay particular attention to the sections that describe chunk names,
4788and look at how other chunks were designed, so you can do things
4789similarly. Second, check out the sections of libpng that read and
4790write chunks. Try to find a chunk that is similar to yours and use
4791it as a template. More details can be found in the comments inside
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4792the code. It is best to handle private or unknown chunks in a generic method,
4793via callback functions, instead of by modifying libpng functions. This
4794is illustrated in pngtest.c, which uses a callback function to handle a
4795private "vpAg" chunk and the new "sTER" chunk, which are both unknown to
4796libpng.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4797
4798If you wish to write your own transformation for the data, look through
4799the part of the code that does the transformations, and check out some of
4800the simpler ones to get an idea of how they work. Try to find a similar
4801transformation to the one you want to add and copy off of it. More details
4802can be found in the comments inside the code itself.
4803
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4804.SS Configuring for gui/windowing platforms:
4805
4806You will need to write new error and warning functions that use the GUI
4807interface, as described previously, and set them to be the error and
4808warning functions at the time that png_create_*_struct() is called,
4809in order to have them available during the structure initialization.
4810They can be changed later via png_set_error_fn(). On some compilers,
4811you may also have to change the memory allocators (png_malloc, etc.).
4812
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4813.SS Configuring zlib:
4814
4815There are special functions to configure the compression. Perhaps the
4816most useful one changes the compression level, which currently uses
4817input compression values in the range 0 - 9. The library normally
4818uses the default compression level (Z_DEFAULT_COMPRESSION = 6). Tests
4819have shown that for a large majority of images, compression values in
4820the range 3-6 compress nearly as well as higher levels, and do so much
4821faster. For online applications it may be desirable to have maximum speed
4822(Z_BEST_SPEED = 1). With versions of zlib after v0.99, you can also
4823specify no compression (Z_NO_COMPRESSION = 0), but this would create
4824files larger than just storing the raw bitmap. You can specify the
4825compression level by calling:
4826
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4827 #include zlib.h
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4828 png_set_compression_level(png_ptr, level);
4829
4830Another useful one is to reduce the memory level used by the library.
4831The memory level defaults to 8, but it can be lowered if you are
4832short on memory (running DOS, for example, where you only have 640K).
4833Note that the memory level does have an effect on compression; among
4834other things, lower levels will result in sections of incompressible
4835data being emitted in smaller stored blocks, with a correspondingly
4836larger relative overhead of up to 15% in the worst case.
4837
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4838 #include zlib.h
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4839 png_set_compression_mem_level(png_ptr, level);
4840
4841The other functions are for configuring zlib. They are not recommended
4842for normal use and may result in writing an invalid PNG file. See
4843zlib.h for more information on what these mean.
4844
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4845 #include zlib.h
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4846 png_set_compression_strategy(png_ptr,
4847 strategy);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4848
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4849 png_set_compression_window_bits(png_ptr,
4850 window_bits);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4851
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4852 png_set_compression_method(png_ptr, method);
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4853
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]4854This controls the size of the IDAT chunks (default 8192):
4855
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4856 png_set_compression_buffer_size(png_ptr, size);
4857
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4858As of libpng version 1.5.4, additional APIs became
4859available to set these separately for non-IDAT
4860compressed chunks such as zTXt, iTXt, and iCCP:
4861
4862 #include zlib.h
4863 #if PNG_LIBPNG_VER >= 10504
4864 png_set_text_compression_level(png_ptr, level);
4865
4866 png_set_text_compression_mem_level(png_ptr, level);
4867
4868 png_set_text_compression_strategy(png_ptr,
4869 strategy);
4870
4871 png_set_text_compression_window_bits(png_ptr,
4872 window_bits);
4873
4874 png_set_text_compression_method(png_ptr, method);
4875 #endif
4876
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4877.SS Controlling row filtering
4878
4879If you want to control whether libpng uses filtering or not, which
4880filters are used, and how it goes about picking row filters, you
4881can call one of these functions. The selection and configuration
4882of row filters can have a significant impact on the size and
4883encoding speed and a somewhat lesser impact on the decoding speed
4884of an image. Filtering is enabled by default for RGB and grayscale
4885images (with and without alpha), but not for paletted images nor
4886for any images with bit depths less than 8 bits/pixel.
4887
4888The 'method' parameter sets the main filtering method, which is
4889currently only '0' in the PNG 1.2 specification. The 'filters'
4890parameter sets which filter(s), if any, should be used for each
4891scanline. Possible values are PNG_ALL_FILTERS and PNG_NO_FILTERS
4892to turn filtering on and off, respectively.
4893
4894Individual filter types are PNG_FILTER_NONE, PNG_FILTER_SUB,
4895PNG_FILTER_UP, PNG_FILTER_AVG, PNG_FILTER_PAETH, which can be bitwise
4896ORed together with '|' to specify one or more filters to use.
4897These filters are described in more detail in the PNG specification.
4898If you intend to change the filter type during the course of writing
4899the image, you should start with flags set for all of the filters
4900you intend to use so that libpng can initialize its internal
4901structures appropriately for all of the filter types. (Note that this
4902means the first row must always be adaptively filtered, because libpng
4903currently does not allocate the filter buffers until png_write_row()
4904is called for the first time.)
4905
4906 filters = PNG_FILTER_NONE | PNG_FILTER_SUB
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]4907 PNG_FILTER_UP | PNG_FILTER_AVG |
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4908 PNG_FILTER_PAETH | PNG_ALL_FILTERS;
4909
4910 png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE,
4911 filters);
4912 The second parameter can also be
4913 PNG_INTRAPIXEL_DIFFERENCING if you are
4914 writing a PNG to be embedded in a MNG
4915 datastream. This parameter must be the
4916 same as the value of filter_method used
4917 in png_set_IHDR().
4918
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4919.SS Requesting debug printout
4920
4921The macro definition PNG_DEBUG can be used to request debugging
4922printout. Set it to an integer value in the range 0 to 3. Higher
4923numbers result in increasing amounts of debugging information. The
4924information is printed to the "stderr" file, unless another file
4925name is specified in the PNG_DEBUG_FILE macro definition.
4926
4927When PNG_DEBUG > 0, the following functions (macros) become available:
4928
4929 png_debug(level, message)
4930 png_debug1(level, message, p1)
4931 png_debug2(level, message, p1, p2)
4932
4933in which "level" is compared to PNG_DEBUG to decide whether to print
4934the message, "message" is the formatted string to be printed,
4935and p1 and p2 are parameters that are to be embedded in the string
4936according to printf-style formatting directives. For example,
4937
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4938 png_debug1(2, "foo=%d", foo);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4939
4940is expanded to
4941
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4942 if (PNG_DEBUG > 2)
4943 fprintf(PNG_DEBUG_FILE, "foo=%d\en", foo);
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4944
4945When PNG_DEBUG is defined but is zero, the macros aren't defined, but you
4946can still use PNG_DEBUG to control your own debugging:
4947
4948 #ifdef PNG_DEBUG
4949 fprintf(stderr, ...
4950 #endif
4951
4952When PNG_DEBUG = 1, the macros are defined, but only png_debug statements
4953having level = 0 will be printed. There aren't any such statements in
4954this version of libpng, but if you insert some they will be printed.
4955
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4956.SH VII. MNG support
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4957
4958The MNG specification (available at http://www.libpng.org/pub/mng) allows
4959certain extensions to PNG for PNG images that are embedded in MNG datastreams.
4960Libpng can support some of these extensions. To enable them, use the
4961png_permit_mng_features() function:
4962
4963 feature_set = png_permit_mng_features(png_ptr, mask)
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4964
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4965 mask is a png_uint_32 containing the bitwise OR of the
4966 features you want to enable. These include
4967 PNG_FLAG_MNG_EMPTY_PLTE
4968 PNG_FLAG_MNG_FILTER_64
4969 PNG_ALL_MNG_FEATURES
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4970
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4971 feature_set is a png_uint_32 that is the bitwise AND of
4972 your mask with the set of MNG features that is
4973 supported by the version of libpng that you are using.
4974
4975It is an error to use this function when reading or writing a standalone
4976PNG file with the PNG 8-byte signature. The PNG datastream must be wrapped
4977in a MNG datastream. As a minimum, it must have the MNG 8-byte signature
4978and the MHDR and MEND chunks. Libpng does not provide support for these
4979or any other MNG chunks; your application must provide its own support for
4980them. You may wish to consider using libmng (available at
4981http://www.libmng.com) instead.
4982
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4983.SH VIII. Changes to Libpng from version 0.88
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4984
4985It should be noted that versions of libpng later than 0.96 are not
4986distributed by the original libpng author, Guy Schalnat, nor by
4987Andreas Dilger, who had taken over from Guy during 1996 and 1997, and
4988distributed versions 0.89 through 0.96, but rather by another member
4989of the original PNG Group, Glenn Randers-Pehrson. Guy and Andreas are
4990still alive and well, but they have moved on to other things.
4991
4992The old libpng functions png_read_init(), png_write_init(),
4993png_info_init(), png_read_destroy(), and png_write_destroy() have been
4994moved to PNG_INTERNAL in version 0.95 to discourage their use. These
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]4995functions will be removed from libpng version 1.4.0.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]4996
4997The preferred method of creating and initializing the libpng structures is
4998via the png_create_read_struct(), png_create_write_struct(), and
4999png_create_info_struct() because they isolate the size of the structures
5000from the application, allow version error checking, and also allow the
5001use of custom error handling routines during the initialization, which
5002the old functions do not. The functions png_read_destroy() and
5003png_write_destroy() do not actually free the memory that libpng
5004allocated for these structs, but just reset the data structures, so they
5005can be used instead of png_destroy_read_struct() and
5006png_destroy_write_struct() if you feel there is too much system overhead
5007allocating and freeing the png_struct for each image read.
5008
5009Setting the error callbacks via png_set_message_fn() before
5010png_read_init() as was suggested in libpng-0.88 is no longer supported
5011because this caused applications that do not use custom error functions
5012to fail if the png_ptr was not initialized to zero. It is still possible
5013to set the error callbacks AFTER png_read_init(), or to change them with
5014png_set_error_fn(), which is essentially the same function, but with a new
5015name to force compilation errors with applications that try to use the old
5016method.
5017
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]5018Support for the sCAL, iCCP, iTXt, and sPLT chunks was added at libpng-1.0.6;
5019however, iTXt support was not enabled by default.
5020
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]5021Starting with version 1.0.7, you can find out which version of the library
5022you are using at run-time:
5023
5024 png_uint_32 libpng_vn = png_access_version_number();
5025
5026The number libpng_vn is constructed from the major version, minor
5027version with leading zero, and release number with leading zero,
5028(e.g., libpng_vn for version 1.0.7 is 10007).
5029
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5030Note that this function does not take a png_ptr, so you can call it
5031before you've created one.
5032
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]5033You can also check which version of png.h you used when compiling your
5034application:
5035
5036 png_uint_32 application_vn = PNG_LIBPNG_VER;
5037
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5038.SH IX. Changes to Libpng from version 1.0.x to 1.2.x
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]5039
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5040Support for user memory management was enabled by default. To
5041accomplish this, the functions png_create_read_struct_2(),
5042png_create_write_struct_2(), png_set_mem_fn(), png_get_mem_ptr(),
5043png_malloc_default(), and png_free_default() were added.
5044
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]5045Support for the iTXt chunk has been enabled by default as of
5046version 1.2.41.
5047
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5048Support for certain MNG features was enabled.
5049
5050Support for numbered error messages was added. However, we never got
5051around to actually numbering the error messages. The function
5052png_set_strip_error_numbers() was added (Note: the prototype for this
5053function was inadvertently removed from png.h in PNG_NO_ASSEMBLER_CODE
5054builds of libpng-1.2.15. It was restored in libpng-1.2.36).
5055
5056The png_malloc_warn() function was added at libpng-1.2.3. This issues
5057a png_warning and returns NULL instead of aborting when it fails to
5058acquire the requested memory allocation.
5059
5060Support for setting user limits on image width and height was enabled
5061by default. The functions png_set_user_limits(), png_get_user_width_max(),
5062and png_get_user_height_max() were added at libpng-1.2.6.
5063
5064The png_set_add_alpha() function was added at libpng-1.2.7.
5065
5066The function png_set_expand_gray_1_2_4_to_8() was added at libpng-1.2.9.
5067Unlike png_set_gray_1_2_4_to_8(), the new function does not expand the
5068tRNS chunk to alpha. The png_set_gray_1_2_4_to_8() function is
5069deprecated.
5070
5071A number of macro definitions in support of runtime selection of
5072assembler code features (especially Intel MMX code support) were
5073added at libpng-1.2.0:
5074
5075 PNG_ASM_FLAG_MMX_SUPPORT_COMPILED
5076 PNG_ASM_FLAG_MMX_SUPPORT_IN_CPU
5077 PNG_ASM_FLAG_MMX_READ_COMBINE_ROW
5078 PNG_ASM_FLAG_MMX_READ_INTERLACE
5079 PNG_ASM_FLAG_MMX_READ_FILTER_SUB
5080 PNG_ASM_FLAG_MMX_READ_FILTER_UP
5081 PNG_ASM_FLAG_MMX_READ_FILTER_AVG
5082 PNG_ASM_FLAG_MMX_READ_FILTER_PAETH
5083 PNG_ASM_FLAGS_INITIALIZED
5084 PNG_MMX_READ_FLAGS
5085 PNG_MMX_FLAGS
5086 PNG_MMX_WRITE_FLAGS
5087 PNG_MMX_FLAGS
5088
5089We added the following functions in support of runtime
5090selection of assembler code features:
5091
5092 png_get_mmx_flagmask()
5093 png_set_mmx_thresholds()
5094 png_get_asm_flags()
5095 png_get_mmx_bitdepth_threshold()
5096 png_get_mmx_rowbytes_threshold()
5097 png_set_asm_flags()
5098
5099We replaced all of these functions with simple stubs in libpng-1.2.20,
5100when the Intel assembler code was removed due to a licensing issue.
5101
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]5102These macros are deprecated:
5103
5104 PNG_READ_TRANSFORMS_NOT_SUPPORTED
5105 PNG_PROGRESSIVE_READ_NOT_SUPPORTED
5106 PNG_NO_SEQUENTIAL_READ_SUPPORTED
5107 PNG_WRITE_TRANSFORMS_NOT_SUPPORTED
5108 PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED
5109 PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED
5110
5111They have been replaced, respectively, by:
5112
5113 PNG_NO_READ_TRANSFORMS
5114 PNG_NO_PROGRESSIVE_READ
5115 PNG_NO_SEQUENTIAL_READ
5116 PNG_NO_WRITE_TRANSFORMS
5117 PNG_NO_READ_ANCILLARY_CHUNKS
5118 PNG_NO_WRITE_ANCILLARY_CHUNKS
5119
5120PNG_MAX_UINT was replaced with PNG_UINT_31_MAX. It has been
5121deprecated since libpng-1.0.16 and libpng-1.2.6.
5122
5123The function
5124 png_check_sig(sig, num)
5125was replaced with
5126 !png_sig_cmp(sig, 0, num)
5127It has been deprecated since libpng-0.90.
5128
5129The function
5130 png_set_gray_1_2_4_to_8()
5131which also expands tRNS to alpha was replaced with
5132 png_set_expand_gray_1_2_4_to_8()
5133which does not. It has been deprecated since libpng-1.0.18 and 1.2.9.
5134
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5135.SH X. Changes to Libpng from version 1.0.x/1.2.x to 1.4.x
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5136
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5137Private libpng prototypes and macro definitions were moved from
5138png.h and pngconf.h into a new pngpriv.h header file.
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]5139
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5140Functions png_set_benign_errors(), png_benign_error(), and
5141png_chunk_benign_error() were added.
5142
5143Support for setting the maximum amount of memory that the application
5144will allocate for reading chunks was added, as a security measure.
5145The functions png_set_chunk_cache_max() and png_get_chunk_cache_max()
5146were added to the library.
5147
5148We implemented support for I/O states by adding png_ptr member io_state
5149and functions png_get_io_chunk_name() and png_get_io_state() in pngget.c
5150
5151We added PNG_TRANSFORM_GRAY_TO_RGB to the available high-level
5152input transforms.
5153
5154Checking for and reporting of errors in the IHDR chunk is more thorough.
5155
5156Support for global arrays was removed, to improve thread safety.
5157
5158Some obsolete/deprecated macros and functions have been removed.
5159
5160Typecasted NULL definitions such as
5161 #define png_voidp_NULL (png_voidp)NULL
5162were eliminated. If you used these in your application, just use
5163NULL instead.
5164
5165The png_struct and info_struct members "trans" and "trans_values" were
5166changed to "trans_alpha" and "trans_color", respectively.
5167
5168The obsolete, unused pnggccrd.c and pngvcrd.c files and related makefiles
5169were removed.
5170
5171The PNG_1_0_X and PNG_1_2_X macros were eliminated.
5172
5173The PNG_LEGACY_SUPPORTED macro was eliminated.
5174
5175Many WIN32_WCE #ifdefs were removed.
5176
5177The functions png_read_init(info_ptr), png_write_init(info_ptr),
5178png_info_init(info_ptr), png_read_destroy(), and png_write_destroy()
5179have been removed. They have been deprecated since libpng-0.95.
5180
5181The png_permit_empty_plte() was removed. It has been deprecated
5182since libpng-1.0.9. Use png_permit_mng_features() instead.
5183
5184We removed the obsolete stub functions png_get_mmx_flagmask(),
5185png_set_mmx_thresholds(), png_get_asm_flags(),
5186png_get_mmx_bitdepth_threshold(), png_get_mmx_rowbytes_threshold(),
5187png_set_asm_flags(), and png_mmx_supported()
5188
5189We removed the obsolete png_check_sig(), png_memcpy_check(), and
5190png_memset_check() functions. Instead use !png_sig_cmp(), memcpy(),
5191and memset(), respectively.
5192
5193The function png_set_gray_1_2_4_to_8() was removed. It has been
5194deprecated since libpng-1.0.18 and 1.2.9, when it was replaced with
5195png_set_expand_gray_1_2_4_to_8() because the former function also
5196expanded any tRNS chunk to an alpha channel.
5197
5198Macros for png_get_uint_16, png_get_uint_32, and png_get_int_32
5199were added and are used by default instead of the corresponding
5200functions. Unfortunately,
5201from libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the
5202function) incorrectly returned a value of type png_uint_32.
5203
5204We changed the prototype for png_malloc() from
5205 png_malloc(png_structp png_ptr, png_uint_32 size)
5206to
5207 png_malloc(png_structp png_ptr, png_alloc_size_t size)
5208
5209This also applies to the prototype for the user replacement malloc_fn().
5210
5211The png_calloc() function was added and is used in place of
5212of "png_malloc(); memset();" except in the case in png_read_png()
5213where the array consists of pointers; in this case a "for" loop is used
5214after the png_malloc() to set the pointers to NULL, to give robust.
5215behavior in case the application runs out of memory part-way through
5216the process.
5217
5218We changed the prototypes of png_get_compression_buffer_size() and
5219png_set_compression_buffer_size() to work with png_size_t instead of
5220png_uint_32.
5221
5222Support for numbered error messages was removed by default, since we
5223never got around to actually numbering the error messages. The function
5224png_set_strip_error_numbers() was removed from the library by default.
5225
5226The png_zalloc() and png_zfree() functions are no longer exported.
5227The png_zalloc() function no longer zeroes out the memory that it
5228allocates. Applications that called png_zalloc(png_ptr, number, size)
5229can call png_calloc(png_ptr, number*size) instead, and can call
5230png_free() instead of png_zfree().
5231
5232Support for dithering was disabled by default in libpng-1.4.0, because
5233it has not been well tested and doesn't actually "dither".
5234The code was not
5235removed, however, and could be enabled by building libpng with
5236PNG_READ_DITHER_SUPPORTED defined. In libpng-1.4.2, this support
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]5237was re-enabled, but the function was renamed png_set_quantize() to
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5238reflect more accurately what it actually does. At the same time,
5239the PNG_DITHER_[RED,GREEN_BLUE]_BITS macros were also renamed to
5240PNG_QUANTIZE_[RED,GREEN,BLUE]_BITS, and PNG_READ_DITHER_SUPPORTED
5241was renamed to PNG_READ_QUANTIZE_SUPPORTED.
5242
5243We removed the trailing '.' from the warning and error messages.
5244
5245.SH XI. Changes to Libpng from version 1.4.x to 1.5.x
5246
5247From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the
5248function) incorrectly returned a value of type png_uint_32.
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]5249The incorrect macro was removed from libpng-1.4.5.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5250
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]5251Checking for invalid palette index on write was added at libpng
52521.5.10. If a pixel contains an invalid (out-of-range) index libpng issues
5253a benign error. This is enabled by default because this condition is an
5254error according to the PNG specification, Clause 11.3.2, but the error can
5255be ignored in each png_ptr with
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5256
5257 png_set_check_for_invalid_index(png_ptr, allowed);
5258
5259 allowed - one of
5260 0: disable benign error (accept the
5261 invalid data without warning).
5262 1: enable benign error (treat the
5263 invalid data as an error or a
5264 warning).
5265
5266If the error is ignored, or if png_benign_error() treats it as a warning,
5267any invalid pixels are decoded as opaque black by the decoder and written
5268as-is by the encoder.
5269
5270Retrieving the maximum palette index found was added at libpng-1.5.15.
5271This statement must appear after png_read_png() or png_read_image() while
5272reading, and after png_write_png() or png_write_image() while writing.
5273
5274 int max_palette = png_get_palette_max(png_ptr, info_ptr);
5275
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]5276This will return the maximum palette index found in the image, or "\-1" if
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5277the palette was not checked, or "0" if no palette was found. Note that this
5278does not account for any palette index used by ancillary chunks such as the
5279bKGD chunk; you must check those separately to determine the maximum
5280palette index actually used.
5281
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5282There are no substantial API changes between the non-deprecated parts of
5283the 1.4.5 API and the 1.5.0 API; however, the ability to directly access
5284members of the main libpng control structures, png_struct and png_info,
5285deprecated in earlier versions of libpng, has been completely removed from
5286libpng 1.5.
5287
5288We no longer include zlib.h in png.h. The include statement has been moved
5289to pngstruct.h, where it is not accessible by applications. Applications that
5290need access to information in zlib.h will need to add the '#include "zlib.h"'
5291directive. It does not matter whether this is placed prior to or after
5292the '"#include png.h"' directive.
5293
5294The png_sprintf(), png_strcpy(), and png_strncpy() macros are no longer used
5295and were removed.
5296
5297We moved the png_strlen(), png_memcpy(), png_memset(), and png_memcmp()
5298macros into a private header file (pngpriv.h) that is not accessible to
5299applications.
5300
5301In png_get_iCCP, the type of "profile" was changed from png_charpp
5302to png_bytepp, and in png_set_iCCP, from png_charp to png_const_bytep.
5303
5304There are changes of form in png.h, including new and changed macros to
5305declare parts of the API. Some API functions with arguments that are
5306pointers to data not modified within the function have been corrected to
5307declare these arguments with PNG_CONST.
5308
5309Much of the internal use of C macros to control the library build has also
5310changed and some of this is visible in the exported header files, in
5311particular the use of macros to control data and API elements visible
5312during application compilation may require significant revision to
5313application code. (It is extremely rare for an application to do this.)
5314
5315Any program that compiled against libpng 1.4 and did not use deprecated
5316features or access internal library structures should compile and work
5317against libpng 1.5, except for the change in the prototype for
5318png_get_iCCP() and png_set_iCCP() API functions mentioned above.
5319
5320libpng 1.5.0 adds PNG_ PASS macros to help in the reading and writing of
5321interlaced images. The macros return the number of rows and columns in
5322each pass and information that can be used to de-interlace and (if
5323absolutely necessary) interlace an image.
5324
5325libpng 1.5.0 adds an API png_longjmp(png_ptr, value). This API calls
5326the application-provided png_longjmp_ptr on the internal, but application
5327initialized, longjmp buffer. It is provided as a convenience to avoid
5328the need to use the png_jmpbuf macro, which had the unnecessary side
5329effect of resetting the internal png_longjmp_ptr value.
5330
5331libpng 1.5.0 includes a complete fixed point API. By default this is
5332present along with the corresponding floating point API. In general the
5333fixed point API is faster and smaller than the floating point one because
5334the PNG file format used fixed point, not floating point. This applies
5335even if the library uses floating point in internal calculations. A new
5336macro, PNG_FLOATING_ARITHMETIC_SUPPORTED, reveals whether the library
5337uses floating point arithmetic (the default) or fixed point arithmetic
5338internally for performance critical calculations such as gamma correction.
5339In some cases, the gamma calculations may produce slightly different
5340results. This has changed the results in png_rgb_to_gray and in alpha
5341composition (png_set_background for example). This applies even if the
5342original image was already linear (gamma == 1.0) and, therefore, it is
5343not necessary to linearize the image. This is because libpng has *not*
5344been changed to optimize that case correctly, yet.
5345
5346Fixed point support for the sCAL chunk comes with an important caveat;
5347the sCAL specification uses a decimal encoding of floating point values
5348and the accuracy of PNG fixed point values is insufficient for
5349representation of these values. Consequently a "string" API
5350(png_get_sCAL_s and png_set_sCAL_s) is the only reliable way of reading
5351arbitrary sCAL chunks in the absence of either the floating point API or
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]5352internal floating point calculations. Starting with libpng-1.5.0, both
5353of these functions are present when PNG_sCAL_SUPPORTED is defined. Prior
5354to libpng-1.5.0, their presence also depended upon PNG_FIXED_POINT_SUPPORTED
5355being defined and PNG_FLOATING_POINT_SUPPORTED not being defined.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5356
5357Applications no longer need to include the optional distribution header
5358file pngusr.h or define the corresponding macros during application
5359build in order to see the correct variant of the libpng API. From 1.5.0
5360application code can check for the corresponding _SUPPORTED macro:
5361
5362#ifdef PNG_INCH_CONVERSIONS_SUPPORTED
5363 /* code that uses the inch conversion APIs. */
5364#endif
5365
5366This macro will only be defined if the inch conversion functions have been
5367compiled into libpng. The full set of macros, and whether or not support
5368has been compiled in, are available in the header file pnglibconf.h.
5369This header file is specific to the libpng build. Notice that prior to
53701.5.0 the _SUPPORTED macros would always have the default definition unless
5371reset by pngusr.h or by explicit settings on the compiler command line.
5372These settings may produce compiler warnings or errors in 1.5.0 because
5373of macro redefinition.
5374
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5375Applications can now choose whether to use these macros or to call the
5376corresponding function by defining PNG_USE_READ_MACROS or
5377PNG_NO_USE_READ_MACROS before including png.h. Notice that this is
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]5378only supported from 1.5.0; defining PNG_NO_USE_READ_MACROS prior to 1.5.0
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5379will lead to a link failure.
5380
5381Prior to libpng-1.5.4, the zlib compressor used the same set of parameters
5382when compressing the IDAT data and textual data such as zTXt and iCCP.
5383In libpng-1.5.4 we reinitialized the zlib stream for each type of data.
5384We added five png_set_text_*() functions for setting the parameters to
5385use with textual data.
5386
5387Prior to libpng-1.5.4, the PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
5388option was off by default, and slightly inaccurate scaling occurred.
5389This option can no longer be turned off, and the choice of accurate
5390or inaccurate 16-to-8 scaling is by using the new png_set_scale_16_to_8()
5391API for accurate scaling or the old png_set_strip_16_to_8() API for simple
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]5392chopping. In libpng-1.5.4, the PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED
5393macro became PNG_READ_SCALE_16_TO_8_SUPPORTED, and the PNG_READ_16_TO_8
5394macro became PNG_READ_STRIP_16_TO_8_SUPPORTED, to enable the two
5395png_set_*_16_to_8() functions separately.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5396
5397Prior to libpng-1.5.4, the png_set_user_limits() function could only be
5398used to reduce the width and height limits from the value of
5399PNG_USER_WIDTH_MAX and PNG_USER_HEIGHT_MAX, although this document said
5400that it could be used to override them. Now this function will reduce or
5401increase the limits.
5402
5403Starting in libpng-1.5.10, the user limits can be set en masse with the
5404configuration option PNG_SAFE_LIMITS_SUPPORTED. If this option is enabled,
5405a set of "safe" limits is applied in pngpriv.h. These can be overridden by
5406application calls to png_set_user_limits(), png_set_user_chunk_cache_max(),
5407and/or png_set_user_malloc_max() that increase or decrease the limits. Also,
5408in libpng-1.5.10 the default width and height limits were increased
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5409from 1,000,000 to 0x7fffffff (i.e., made unlimited). Therefore, the
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5410limits are now
5411 default safe
5412 png_user_width_max 0x7fffffff 1,000,000
5413 png_user_height_max 0x7fffffff 1,000,000
5414 png_user_chunk_cache_max 0 (unlimited) 128
5415 png_user_chunk_malloc_max 0 (unlimited) 8,000,000
5416
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]5417The png_set_option() function (and the "options" member of the png struct) was
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5418added to libpng-1.5.15, with option PNG_ARM_NEON.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5419
5420The library now supports a complete fixed point implementation and can
5421thus be used on systems that have no floating point support or very
5422limited or slow support. Previously gamma correction, an essential part
5423of complete PNG support, required reasonably fast floating point.
5424
5425As part of this the choice of internal implementation has been made
5426independent of the choice of fixed versus floating point APIs and all the
5427missing fixed point APIs have been implemented.
5428
5429The exact mechanism used to control attributes of API functions has
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5430changed, as described in the INSTALL file.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5431
5432A new test program, pngvalid, is provided in addition to pngtest.
5433pngvalid validates the arithmetic accuracy of the gamma correction
5434calculations and includes a number of validations of the file format.
5435A subset of the full range of tests is run when "make check" is done
5436(in the 'configure' build.) pngvalid also allows total allocated memory
5437usage to be evaluated and performs additional memory overwrite validation.
5438
5439Many changes to individual feature macros have been made. The following
5440are the changes most likely to be noticed by library builders who
5441configure libpng:
5442
54431) All feature macros now have consistent naming:
5444
5445#define PNG_NO_feature turns the feature off
5446#define PNG_feature_SUPPORTED turns the feature on
5447
5448pnglibconf.h contains one line for each feature macro which is either:
5449
5450#define PNG_feature_SUPPORTED
5451
5452if the feature is supported or:
5453
5454/*#undef PNG_feature_SUPPORTED*/
5455
5456if it is not. Library code consistently checks for the 'SUPPORTED' macro.
5457It does not, and libpng applications should not, check for the 'NO' macro
5458which will not normally be defined even if the feature is not supported.
5459The 'NO' macros are only used internally for setting or not setting the
5460corresponding 'SUPPORTED' macros.
5461
5462Compatibility with the old names is provided as follows:
5463
5464PNG_INCH_CONVERSIONS turns on PNG_INCH_CONVERSIONS_SUPPORTED
5465
5466And the following definitions disable the corresponding feature:
5467
5468PNG_SETJMP_NOT_SUPPORTED disables SETJMP
5469PNG_READ_TRANSFORMS_NOT_SUPPORTED disables READ_TRANSFORMS
5470PNG_NO_READ_COMPOSITED_NODIV disables READ_COMPOSITE_NODIV
5471PNG_WRITE_TRANSFORMS_NOT_SUPPORTED disables WRITE_TRANSFORMS
5472PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED disables READ_ANCILLARY_CHUNKS
5473PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED disables WRITE_ANCILLARY_CHUNKS
5474
5475Library builders should remove use of the above, inconsistent, names.
5476
54772) Warning and error message formatting was previously conditional on
5478the STDIO feature. The library has been changed to use the
5479CONSOLE_IO feature instead. This means that if CONSOLE_IO is disabled
5480the library no longer uses the printf(3) functions, even though the
5481default read/write implementations use (FILE) style stdio.h functions.
5482
54833) Three feature macros now control the fixed/floating point decisions:
5484
5485PNG_FLOATING_POINT_SUPPORTED enables the floating point APIs
5486
5487PNG_FIXED_POINT_SUPPORTED enables the fixed point APIs; however, in
5488practice these are normally required internally anyway (because the PNG
5489file format is fixed point), therefore in most cases PNG_NO_FIXED_POINT
5490merely stops the function from being exported.
5491
5492PNG_FLOATING_ARITHMETIC_SUPPORTED chooses between the internal floating
5493point implementation or the fixed point one. Typically the fixed point
5494implementation is larger and slower than the floating point implementation
5495on a system that supports floating point; however, it may be faster on a
5496system which lacks floating point hardware and therefore uses a software
5497emulation.
5498
54994) Added PNG_{READ,WRITE}_INT_FUNCTIONS_SUPPORTED. This allows the
5500functions to read and write ints to be disabled independently of
5501PNG_USE_READ_MACROS, which allows libpng to be built with the functions
5502even though the default is to use the macros - this allows applications
5503to choose at app buildtime whether or not to use macros (previously
5504impossible because the functions weren't in the default build.)
5505
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5506.SH XII. Changes to Libpng from version 1.5.x to 1.6.x
5507
5508A "simplified API" has been added (see documentation in png.h and a simple
5509example in contrib/examples/pngtopng.c). The new publicly visible API
5510includes the following:
5511
5512 macros:
5513 PNG_FORMAT_*
5514 PNG_IMAGE_*
5515 structures:
5516 png_control
5517 png_image
5518 read functions
5519 png_image_begin_read_from_file()
5520 png_image_begin_read_from_stdio()
5521 png_image_begin_read_from_memory()
5522 png_image_finish_read()
5523 png_image_free()
5524 write functions
5525 png_image_write_to_file()
5526 png_image_write_to_stdio()
5527
5528Starting with libpng-1.6.0, you can configure libpng to prefix all exported
5529symbols, using the PNG_PREFIX macro.
5530
5531We no longer include string.h in png.h. The include statement has been moved
5532to pngpriv.h, where it is not accessible by applications. Applications that
5533need access to information in string.h must add an '#include <string.h>'
5534directive. It does not matter whether this is placed prior to or after
5535the '#include "png.h"' directive.
5536
5537The following API are now DEPRECATED:
5538 png_info_init_3()
5539 png_convert_to_rfc1123() which has been replaced
5540 with png_convert_to_rfc1123_buffer()
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5541 png_malloc_default()
5542 png_free_default()
5543 png_reset_zstream()
5544
5545The following have been removed:
5546 png_get_io_chunk_name(), which has been replaced
5547 with png_get_io_chunk_type(). The new
5548 function returns a 32-bit integer instead of
5549 a string.
5550 The png_sizeof(), png_strlen(), png_memcpy(), png_memcmp(), and
5551 png_memset() macros are no longer used in the libpng sources and
5552 have been removed. These had already been made invisible to applications
5553 (i.e., defined in the private pngpriv.h header file) since libpng-1.5.0.
5554
5555The signatures of many exported functions were changed, such that
5556 png_structp became png_structrp or png_const_structrp
5557 png_infop became png_inforp or png_const_inforp
5558where "rp" indicates a "restricted pointer".
5559
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5560Dropped support for 16-bit platforms. The support for FAR/far types has
5561been eliminated and the definition of png_alloc_size_t is now controlled
5562by a flag so that 'small size_t' systems can select it if necessary.
5563
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5564Error detection in some chunks has improved; in particular the iCCP chunk
5565reader now does pretty complete validation of the basic format. Some bad
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]5566profiles that were previously accepted are now accepted with a warning or
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5567rejected, depending upon the png_set_benign_errors() setting, in particular
5568the very old broken Microsoft/HP 3144-byte sRGB profile. Starting with
5569libpng-1.6.11, recognizing and checking sRGB profiles can be avoided by
5570means of
5571
5572 #if defined(PNG_SKIP_sRGB_CHECK_PROFILE) && \
5573 defined(PNG_SET_OPTION_SUPPORTED)
5574 png_set_option(png_ptr, PNG_SKIP_sRGB_CHECK_PROFILE,
5575 PNG_OPTION_ON);
5576 #endif
5577
5578It's not a good idea to do this if you are using the "simplified API",
5579which needs to be able to recognize sRGB profiles conveyed via the iCCP
5580chunk.
5581
5582The PNG spec requirement that only grayscale profiles may appear in images
5583with color type 0 or 4 and that even if the image only contains gray pixels,
5584only RGB profiles may appear in images with color type 2, 3, or 6, is now
5585enforced. The sRGB chunk is allowed to appear in images with any color type
5586and is interpreted by libpng to convey a one-tracer-curve gray profile or a
5587three-tracer-curve RGB profile as appropriate.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5588
5589Prior to libpng-1.6.0 a warning would be issued if the iTXt chunk contained
5590an empty language field or an empty translated keyword. Both of these
5591are allowed by the PNG specification, so these warnings are no longer issued.
5592
5593The library now issues an error if the application attempts to set a
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]5594transform after it calls png_read_update_info() or if it attempts to call
5595both png_read_update_info() and png_start_read_image() or to call either
5596of them more than once.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5597
5598The default condition for benign_errors is now to treat benign errors as
5599warnings while reading and as errors while writing.
5600
5601The library now issues a warning if both background processing and RGB to
5602gray are used when gamma correction happens. As with previous versions of
5603the library the results are numerically very incorrect in this case.
5604
5605There are some minor arithmetic changes in some transforms such as
5606png_set_background(), that might be detected by certain regression tests.
5607
5608Unknown chunk handling has been improved internally, without any API change.
5609This adds more correct option control of the unknown handling, corrects
5610a pre-existing bug where the per-chunk 'keep' setting is ignored, and makes
5611it possible to skip IDAT chunks in the sequential reader.
5612
5613The machine-generated configure files are no longer included in branches
5614libpng16 and later of the GIT repository. They continue to be included
5615in the tarball releases, however.
5616
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]5617Libpng-1.6.0 through 1.6.2 used the CMF bytes at the beginning of the IDAT
5618stream to set the size of the sliding window for reading instead of using the
5619default 32-kbyte sliding window size. It was discovered that there are
5620hundreds of PNG files in the wild that have incorrect CMF bytes that caused
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5621zlib to issue the "invalid distance too far back" error and reject the file.
5622Libpng-1.6.3 and later calculate their own safe CMF from the image dimensions,
5623provide a way to revert to the libpng-1.5.x behavior (ignoring the CMF bytes
5624and using a 32-kbyte sliding window), by using
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]5625
5626 png_set_option(png_ptr, PNG_MAXIMUM_INFLATE_WINDOW,
5627 PNG_OPTION_ON);
5628
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5629and provide a tool (contrib/tools/pngfix) for rewriting a PNG file while
5630optimizing the CMF bytes in its IDAT chunk correctly.
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5631
5632Libpng-1.6.0 and libpng-1.6.1 wrote uncompressed iTXt chunks with the wrong
5633length, which resulted in PNG files that cannot be read beyond the bad iTXt
5634chunk. This error was fixed in libpng-1.6.3, and a tool (called
5635contrib/tools/png-fix-itxt) has been added to the libpng distribution.
5636
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5637Starting with libpng-1.6.17, the PNG_SAFE_LIMITS macro was eliminated
5638and safe limits are used by default (users who need larger limits
5639can still override them at compile time or run time, as described above).
5640
5641The new limits are
5642 default spec limit
5643 png_user_width_max 1,000,000 2,147,483,647
5644 png_user_height_max 1,000,000 2,147,483,647
5645 png_user_chunk_cache_max 128 unlimited
5646 png_user_chunk_malloc_max 8,000,000 unlimited
5647
5648Starting with libpng-1.6.18, a PNG_RELEASE_BUILD macro was added, which allows
5649library builders to control compilation for an installed system (a release build).
5650It can be set for testing debug or beta builds to ensure that they will compile
5651when the build type is switched to RC or STABLE. In essence this overrides the
5652PNG_LIBPNG_BUILD_BASE_TYPE definition which is not directly user controllable.
5653
5654Starting with libpng-1.6.19, attempting to set an over-length PLTE chunk
5655is an error. Previously this requirement of the PNG specification was not
5656enforced, and the palette was always limited to 256 entries. An over-length
5657PLTE chunk found in an input PNG is silently truncated.
5658
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5659.SH XIII. Detecting libpng
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5660
5661The png_get_io_ptr() function has been present since libpng-0.88, has never
5662changed, and is unaffected by conditional compilation macros. It is the
5663best choice for use in configure scripts for detecting the presence of any
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]5664libpng version since 0.88. In an autoconf "configure.in" you could use
5665
5666 AC_CHECK_LIB(png, png_get_io_ptr, ...
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5667
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5668.SH XV. Source code repository
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5669
5670Since about February 2009, version 1.2.34, libpng has been under "git" source
5671control. The git repository was built from old libpng-x.y.z.tar.gz files
5672going back to version 0.70. You can access the git repository (read only)
5673at
5674
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5675 git://git.code.sf.net/p/libpng/code
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5676
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5677or you can browse it with a web browser by selecting the "code" button at
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5678
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5679 https://sourceforge.net/projects/libpng
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5680
5681Patches can be sent to glennrp at users.sourceforge.net or to
5682png-mng-implement at lists.sourceforge.net or you can upload them to
5683the libpng bug tracker at
5684
5685 http://libpng.sourceforge.net
5686
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5687We also accept patches built from the tar or zip distributions, and
5688simple verbal discriptions of bug fixes, reported either to the
5689SourceForge bug tracker, to the png-mng-implement at lists.sf.net
5690mailing list, or directly to glennrp.
5691
5692.SH XV. Coding style
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5693
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5694Our coding style is similar to the "Allman" style
5695(See http://en.wikipedia.org/wiki/Indent_style#Allman_style), with curly
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5696braces on separate lines:
5697
5698 if (condition)
5699 {
5700 action;
5701 }
5702
5703 else if (another condition)
5704 {
5705 another action;
5706 }
5707
5708The braces can be omitted from simple one-line actions:
5709
5710 if (condition)
5711 return (0);
5712
5713We use 3-space indentation, except for continued statements which
5714are usually indented the same as the first line of the statement
5715plus four more spaces.
5716
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]5717For macro definitions we use 2-space indentation, always leaving the "#"
5718in the first column.
5719
5720 #ifndef PNG_NO_FEATURE
5721 # ifndef PNG_FEATURE_SUPPORTED
5722 # define PNG_FEATURE_SUPPORTED
5723 # endif
5724 #endif
5725
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5726Comments appear with the leading "/*" at the same indentation as
5727the statement that follows the comment:
5728
5729 /* Single-line comment */
5730 statement;
5731
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5732 /* This is a multiple-line
5733 * comment.
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5734 */
5735 statement;
5736
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5737Very short comments can be placed after the end of the statement
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5738to which they pertain:
5739
5740 statement; /* comment */
5741
5742We don't use C++ style ("//") comments. We have, however,
5743used them in the past in some now-abandoned MMX assembler
5744code.
5745
5746Functions and their curly braces are not indented, and
5747exported functions are marked with PNGAPI:
5748
5749 /* This is a public function that is visible to
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5750 * application programmers. It does thus-and-so.
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5751 */
5752 void PNGAPI
5753 png_exported_function(png_ptr, png_info, foo)
5754 {
5755 body;
5756 }
5757
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]5758The return type and decorations are placed on a separate line
5759ahead of the function name, as illustrated above.
5760
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]5761The prototypes for all exported functions appear in png.h,
5762above the comment that says
5763
5764 /* Maintainer: Put new public prototypes here ... */
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5765
5766We mark all non-exported functions with "/* PRIVATE */"":
5767
5768 void /* PRIVATE */
5769 png_non_exported_function(png_ptr, png_info, foo)
5770 {
5771 body;
5772 }
5773
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]5774The prototypes for non-exported functions (except for those in
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5775pngtest) appear in pngpriv.h above the comment that says
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]5776
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5777 /* Maintainer: Put new private prototypes here ^ */
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5778
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5779To avoid polluting the global namespace, the names of all exported
5780functions and variables begin with "png_", and all publicly visible C
5781preprocessor macros begin with "PNG". We request that applications that
5782use libpng *not* begin any of their own symbols with either of these strings.
5783
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5784We put a space after the "sizeof" operator and we omit the
5785optional parentheses around its argument when the argument
5786is an expression, not a type name, and we always enclose the
5787sizeof operator, with its argument, in parentheses:
5788
5789 (sizeof (png_uint_32))
5790 (sizeof array)
5791
5792Prior to libpng-1.6.0 we used a "png_sizeof()" macro, formatted as
5793though it were a function.
5794
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5795Control keywords if, for, while, and switch are always followed by a space
5796to distinguish them from function calls, which have no trailing space.
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5797
5798We put a space after each comma and after each semicolon
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5799in "for" statements, and we put spaces before and after each
5800C binary operator and after "for" or "while", and before
5801"?". We don't put a space between a typecast and the expression
5802being cast, nor do we put one between a function name and the
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5803left parenthesis that follows it:
5804
Sireesh Tripurarib478e662014-05-09 15:15:10 +0530[diff] [blame]5805 for (i = 2; i > 0; \-\-i)
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]5806 y[i] = a(x) + (int)b;
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5807
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5808We prefer #ifdef and #ifndef to #if defined() and #if !defined()
5809when there is only one macro being tested. We always use parentheses
5810with "defined".
5811
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5812We express integer constants that are used as bit masks in hex format,
5813with an even number of lower-case hex digits, and to make them unsigned
5814(e.g., 0x00U, 0xffU, 0x0100U) and long if they are greater than 0x7fff
5815(e.g., 0xffffUL).
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5816
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5817We prefer to use underscores rather than camelCase in names, except
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5818for a few type names that we inherit from zlib.h.
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5819
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5820We prefer "if (something != 0)" and "if (something == 0)"
5821over "if (something)" and if "(!something)", respectively.
5822
Patrick Scott5f6bd842010-06-28 16:55:16 -0400[diff] [blame]5823We do not use the TAB character for indentation in the C sources.
5824
5825Lines do not exceed 80 characters.
5826
5827Other rules can be inferred by inspecting the libpng source.
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5828
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5829.SH XVI. Y2K Compliance in libpng
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]5830
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]5831Since the PNG Development group is an ad-hoc body, we can't make
5832an official declaration.
5833
5834This is your unofficial assurance that libpng from version 0.71 and
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5835upward through 1.6.20 are Y2K compliant. It is my belief that earlier
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]5836versions were also Y2K compliant.
5837
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5838Libpng only has two year fields. One is a 2-byte unsigned integer
5839that will hold years up to 65535. The other, which is deprecated,
5840holds the date in text format, and will hold years up to 9999.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]5841
5842The integer is
5843 "png_uint_16 year" in png_time_struct.
5844
Chris Craikb50c2172013-07-29 15:28:30 -0700[diff] [blame]5845The string is
5846 "char time_buffer[29]" in png_struct. This is no longer used
5847in libpng-1.6.x and will be removed from libpng-1.7.0.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]5848
5849There are seven time-related functions:
5850
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5851 png_convert_to_rfc_1123_buffer() in png.c
5852 (formerly png_convert_to_rfc_1152() in error, and
5853 also formerly png_convert_to_rfc_1123())
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]5854 png_convert_from_struct_tm() in pngwrite.c, called
5855 in pngwrite.c
5856 png_convert_from_time_t() in pngwrite.c
5857 png_get_tIME() in pngget.c
5858 png_handle_tIME() in pngrutil.c, called in pngread.c
5859 png_set_tIME() in pngset.c
5860 png_write_tIME() in pngwutil.c, called in pngwrite.c
5861
5862All appear to handle dates properly in a Y2K environment. The
5863png_convert_from_time_t() function calls gmtime() to convert from system
5864clock time, which returns (year - 1900), which we properly convert to
5865the full 4-digit year. There is a possibility that applications using
5866libpng are not passing 4-digit years into the png_convert_to_rfc_1123()
5867function, or that they are incorrectly passing only a 2-digit year
5868instead of "year - 1900" into the png_convert_from_struct_tm() function,
5869but this is not under our control. The libpng documentation has always
5870stated that it works with 4-digit years, and the APIs have been
5871documented as such.
5872
5873The tIME chunk itself is also Y2K compliant. It uses a 2-byte unsigned
5874integer to hold the year, and can hold years as large as 65535.
5875
5876zlib, upon which libpng depends, is also Y2K compliant. It contains
5877no date-related code.
5878
5879
5880 Glenn Randers-Pehrson
5881 libpng maintainer
5882 PNG Development Group
5883
5884.SH NOTE
5885
5886Note about libpng version numbers:
5887
5888Due to various miscommunications, unforeseen code incompatibilities
5889and occasional factors outside the authors' control, version numbering
5890on the library has not always been consistent and straightforward.
5891The following table summarizes matters since version 0.89c, which was
5892the first widely used release:
5893
5894 source png.h png.h shared-lib
5895 version string int version
5896 ------- ------ ----- ----------
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5897 0.89c "1.0 beta 3" 0.89 89 1.0.89
5898 0.90 "1.0 beta 4" 0.90 90 0.90 [should have been 2.0.90]
5899 0.95 "1.0 beta 5" 0.95 95 0.95 [should have been 2.0.95]
5900 0.96 "1.0 beta 6" 0.96 96 0.96 [should have been 2.0.96]
5901 0.97b "1.00.97 beta 7" 1.00.97 97 1.0.1 [should have been 2.0.97]
5902 0.97c 0.97 97 2.0.97
5903 0.98 0.98 98 2.0.98
5904 0.99 0.99 98 2.0.99
5905 0.99a-m 0.99 99 2.0.99
5906 1.00 1.00 100 2.1.0 [100 should be 10000]
5907 1.0.0 (from here on, the 100 2.1.0 [100 should be 10000]
5908 1.0.1 png.h string is 10001 2.1.0
5909 1.0.1a-e identical to the 10002 from here on, the shared library
5910 1.0.2 source version) 10002 is 2.V where V is the source code
5911 1.0.2a-b 10003 version, except as noted.
5912 1.0.3 10003
5913 1.0.3a-d 10004
5914 1.0.4 10004
5915 1.0.4a-f 10005
5916 1.0.5 (+ 2 patches) 10005
5917 1.0.5a-d 10006
5918 1.0.5e-r 10100 (not source compatible)
5919 1.0.5s-v 10006 (not binary compatible)
5920 1.0.6 (+ 3 patches) 10006 (still binary incompatible)
5921 1.0.6d-f 10007 (still binary incompatible)
5922 1.0.6g 10007
5923 1.0.6h 10007 10.6h (testing xy.z so-numbering)
5924 1.0.6i 10007 10.6i
5925 1.0.6j 10007 2.1.0.6j (incompatible with 1.0.0)
5926 1.0.7beta11-14 DLLNUM 10007 2.1.0.7beta11-14 (binary compatible)
5927 1.0.7beta15-18 1 10007 2.1.0.7beta15-18 (binary compatible)
5928 1.0.7rc1-2 1 10007 2.1.0.7rc1-2 (binary compatible)
5929 1.0.7 1 10007 (still compatible)
5930 ...
5931 1.0.19 10 10019 10.so.0.19[.0]
5932 ...
5933 1.2.53 13 10253 12.so.0.53[.0]
5934 ...
5935 1.5.23 15 10523 15.so.15.23[.0]
5936 ...
5937 1.6.20 16 10620 16.so.16.20[.0]
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]5938
5939Henceforth the source version will match the shared-library minor
5940and patch numbers; the shared-library major version number will be
5941used for changes in backward compatibility, as it is intended. The
5942PNG_PNGLIB_VER macro, which is not used within libpng but is available
5943for applications, is an unsigned integer of the form xyyzz corresponding
5944to the source version x.y.z (leading zeros in y and z). Beta versions
5945were given the previous public release number plus a letter, until
5946version 1.0.6j; from then on they were given the upcoming public
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5947release number plus "betaNN" or "rcNN".
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]5948
5949.SH "SEE ALSO"
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5950.IR libpngpf(3) ", " png(5)
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]5951.LP
5952.IR libpng :
5953.IP
5954http://libpng.sourceforge.net (follow the [DOWNLOAD] link)
5955http://www.libpng.org/pub/png
5956
5957.LP
5958.IR zlib :
5959.IP
5960(generally) at the same location as
5961.I libpng
5962or at
5963.br
5964ftp://ftp.info-zip.org/pub/infozip/zlib
5965
5966.LP
5967.IR PNG specification: RFC 2083
5968.IP
5969(generally) at the same location as
5970.I libpng
5971or at
5972.br
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5973ftp://ftp.rfc-editor.org:/in-notes/rfc2083.txt
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]5974.br
5975or (as a W3C Recommendation) at
5976.br
5977http://www.w3.org/TR/REC-png.html
5978
5979.LP
5980In the case of any inconsistency between the PNG specification
5981and this library, the specification takes precedence.
5982
5983.SH AUTHORS
5984This man page: Glenn Randers-Pehrson
5985<glennrp at users.sourceforge.net>
5986
5987The contributing authors would like to thank all those who helped
5988with testing, bug fixes, and patience. This wouldn't have been
5989possible without all of you.
5990
5991Thanks to Frank J. T. Wojcik for helping with the documentation.
5992
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]5993Libpng version 1.6.20 - December 3, 2015:
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]5994Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
5995Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net).
5996
5997Supported by the PNG development group
5998.br
5999png-mng-implement at lists.sf.net
6000(subscription required; visit
6001png-mng-implement at lists.sourceforge.net (subscription required; visit
6002https://lists.sourceforge.net/lists/listinfo/png-mng-implement
6003to subscribe).
6004
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]6005.SH NOTICES:
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]6006
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]6007This copy of the libpng notices is provided for your convenience. In case of
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]6008any discrepancy between this copy and the notices in the file png.h that is
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]6009included in the libpng distribution, the latter shall prevail.
6010
6011COPYRIGHT NOTICE, DISCLAIMER, and LICENSE:
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]6012
6013If you modify libpng you may insert additional notices immediately following
6014this sentence.
6015
Patrick Scotta0bb96c2009-07-22 11:50:02 -0400[diff] [blame]6016This code is released under the libpng license.
6017
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]6018libpng versions 1.0.7, July 1, 2000, through 1.6.20, December 3, 2015, are
6019Copyright (c) 2000-2002, 2004, 2006-2015 Glenn Randers-Pehrson, are
6020derived from libpng-1.0.6, and are distributed according to the same
6021disclaimer and license as libpng-1.0.6 with the following individuals
6022added to the list of Contributing Authors:
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]6023
6024 Simon-Pierre Cadieux
6025 Eric S. Raymond
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]6026 Mans Rullgard
6027 Cosmin Truta
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]6028 Gilles Vollant
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]6029 James Yu
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]6030
6031and with the following additions to the disclaimer:
6032
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]6033 There is no warranty against interference with your enjoyment of the
6034 library or against infringement. There is no warranty that our
6035 efforts or the library will fulfill any of your particular purposes
6036 or needs. This library is provided with all faults, and the entire
6037 risk of satisfactory quality, performance, accuracy, and effort is with
6038 the user.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]6039
6040libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]6041Copyright (c) 1998-2000 Glenn Randers-Pehrson, are derived from
6042libpng-0.96, and are distributed according to the same disclaimer and
6043license as libpng-0.96, with the following individuals added to the list
6044of Contributing Authors:
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]6045
6046 Tom Lane
6047 Glenn Randers-Pehrson
6048 Willem van Schaik
6049
6050libpng versions 0.89, June 1996, through 0.96, May 1997, are
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]6051Copyright (c) 1996-1997 Andreas Dilger, are derived from libpng-0.88,
6052and are distributed according to the same disclaimer and license as
6053libpng-0.88, with the following individuals added to the list of
6054Contributing Authors:
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]6055
6056 John Bowler
6057 Kevin Bracey
6058 Sam Bushell
6059 Magnus Holmgren
6060 Greg Roelofs
6061 Tom Tanner
6062
6063libpng versions 0.5, May 1995, through 0.88, January 1996, are
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]6064Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]6065
6066For the purposes of this copyright and license, "Contributing Authors"
6067is defined as the following set of individuals:
6068
6069 Andreas Dilger
6070 Dave Martindale
6071 Guy Eric Schalnat
6072 Paul Schmidt
6073 Tim Wegner
6074
6075The PNG Reference Library is supplied "AS IS". The Contributing Authors
6076and Group 42, Inc. disclaim all warranties, expressed or implied,
6077including, without limitation, the warranties of merchantability and of
6078fitness for any purpose. The Contributing Authors and Group 42, Inc.
6079assume no liability for direct, indirect, incidental, special, exemplary,
6080or consequential damages, which may result from the use of the PNG
6081Reference Library, even if advised of the possibility of such damage.
6082
6083Permission is hereby granted to use, copy, modify, and distribute this
6084source code, or portions hereof, for any purpose, without fee, subject
6085to the following restrictions:
6086
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]6087 1. The origin of this source code must not be misrepresented.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]6088
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]6089 2. Altered versions must be plainly marked as such and must not
6090 be misrepresented as being the original source.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]6091
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]6092 3. This Copyright notice may not be removed or altered from any
6093 source or altered source distribution.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]6094
6095The Contributing Authors and Group 42, Inc. specifically permit, without
6096fee, and encourage the use of this source code as a component to
6097supporting the PNG file format in commercial products. If you use this
6098source code in a product, acknowledgment is not required but would be
6099appreciated.
6100
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]6101END OF COPYRIGHT NOTICE, DISCLAIMER, and LICENSE.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]6102
6103A "png_get_copyright" function is available, for convenient use in "about"
6104boxes and the like:
6105
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]6106 printf("%s", png_get_copyright(NULL));
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]6107
6108Also, the PNG logo (in PNG format, of course) is supplied in the
6109files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31).
6110
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]6111Libpng is OSI Certified Open Source Software. OSI Certified Open Source is
6112a certification mark of the Open Source Initiative. OSI has not addressed
6113the additional disclaimers inserted at version 1.0.7.
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]6114
6115Glenn Randers-Pehrson
6116glennrp at users.sourceforge.net
Matt Sarett9ea75692016-01-08 13:00:42 -0500[diff] [blame]6117December 3, 2015
The Android Open Source Project893912b2009-03-03 19:30:05 -0800[diff] [blame]6118
6119.\" end of man page
6120