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gerrit-public.fairphone.software / platform / external / libpng / 27742387225ac9c6be47aba9dbbcf401eea2e925 / . / libpng.3
blob: 633b8d39e4ee903e7635fca8d5859f8fd84a7ca3 [file] [log] [blame]
Glenn Randers-Pehrson0012e9c2011-01-26 22:04:03 -0600[diff] [blame]1.TH LIBPNG 3 "January 27, 2011"
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]2.SH NAME
Glenn Randers-Pehrson135d17c2011-01-24 00:16:54 -0600[diff] [blame]3libpng \- Portable Network Graphics (PNG) Reference Library 1.5.1beta10
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4.SH SYNOPSIS
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]5\fI\fB
6
7\fB#include <png.h>\fP
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9\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]10
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]11\fBpng_uint_32 png_access_version_number \fI(void\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]13\fI\fB
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Glenn Randers-Pehrson6bc53be2006-06-16 07:52:03 -0500[diff] [blame]15\fBvoid png_benign_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]17\fI\fB
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Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]19\fBvoid png_build_grayscale_palette (int \fP\fIbit_depth\fP\fB, png_colorp \fIpalette\fP\fB);\fP
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21\fI\fB
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23\fBpng_voidp png_calloc (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP
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25\fI\fB
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Glenn Randers-Pehrson6bc53be2006-06-16 07:52:03 -0500[diff] [blame]27\fBvoid png_chunk_benign_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]29\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]31\fBvoid png_chunk_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]32
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]33\fI\fB
34
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]35\fBvoid png_chunk_warning (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fImessage\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]36
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]37\fI\fB
38
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]39\fBvoid png_convert_from_struct_tm (png_timep \fP\fIptime\fP\fB, struct tm FAR * \fIttime\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]40
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]41\fI\fB
42
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]43\fBvoid png_convert_from_time_t (png_timep \fP\fIptime\fP\fB, time_t \fIttime\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]44
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]45\fI\fB
46
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]47\fBpng_charp png_convert_to_rfc1123 (png_structp \fP\fIpng_ptr\fP\fB, png_timep \fIptime\fP\fB);\fP
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]48
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]49\fI\fB
50
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]51\fBpng_infop png_create_info_struct (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]52
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]53\fI\fB
54
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]55\fBpng_structp png_create_read_struct (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarn_fn\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]56
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]57\fI\fB
58
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]59\fBpng_structp png_create_read_struct_2 (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]60
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]61\fI\fB
62
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]63\fBpng_structp png_create_write_struct (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarn_fn\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]64
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]65\fI\fB
66
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]67\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
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69\fI\fB
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71\fBvoid png_data_freer (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIfreer\fP\fB, png_uint_32 \fImask)\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]72
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]73\fI\fB
74
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]75\fBvoid png_destroy_info_struct (png_structp \fP\fIpng_ptr\fP\fB, png_infopp \fIinfo_ptr_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]77\fI\fB
78
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]79\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
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]81\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]83\fBvoid png_destroy_write_struct (png_structpp \fP\fIpng_ptr_ptr\fP\fB, png_infopp \fIinfo_ptr_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]85\fI\fB
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Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]87\fBvoid png_err (png_structp \fIpng_ptr\fP\fB);\fP
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89\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]91\fBvoid png_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]93\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]95\fBvoid png_free (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]97\fI\fB
98
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]99\fBvoid png_free_chunk_list (png_structp \fIpng_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]101\fI\fB
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Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]103\fBvoid png_free_default (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]104
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]105\fI\fB
106
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]107\fBvoid png_free_data (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fInum\fP\fB);\fP
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]108
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]109\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]111\fBpng_byte png_get_bit_depth (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]112
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]113\fI\fB
114
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]115\fBpng_uint_32 png_get_bKGD (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_16p \fI*background\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]116
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]117\fI\fB
118
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]119\fBpng_byte png_get_channels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]120
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]121\fI\fB
122
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]123\fBpng_uint_32 png_get_cHRM (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, double \fP\fI*white_x\fP\fB, double \fP\fI*white_y\fP\fB, double \fP\fI*red_x\fP\fB, double \fP\fI*red_y\fP\fB, double \fP\fI*green_x\fP\fB, double \fP\fI*green_y\fP\fB, double \fP\fI*blue_x\fP\fB, double \fI*blue_y\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]124
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]125\fI\fB
126
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]127\fBpng_uint_32 png_get_cHRM_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*white_x\fP\fB, png_uint_32 \fP\fI*white_y\fP\fB, png_uint_32 \fP\fI*red_x\fP\fB, png_uint_32 \fP\fI*red_y\fP\fB, png_uint_32 \fP\fI*green_x\fP\fB, png_uint_32 \fP\fI*green_y\fP\fB, png_uint_32 \fP\fI*blue_x\fP\fB, png_uint_32 \fI*blue_y\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]128
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]129\fI\fB
130
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]131\fBpng_uint_32 png_get_chunk_cache_max (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson800d1e92008-08-20 17:25:21 -0500[diff] [blame]132
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]133\fI\fB
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Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]135\fI\fB
136
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]137\fBpng_alloc_size_t png_get_chunk_malloc_max (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]138
139\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]141\fBpng_byte png_get_color_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]142
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]143\fI\fB
144
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]145\fBpng_uint_32 png_get_compression_buffer_size (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson800d1e92008-08-20 17:25:21 -0500[diff] [blame]146
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]147\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]149\fBpng_byte png_get_compression_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]150
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]151\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]153\fBpng_byte png_get_copyright (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]154
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]155\fI\fB
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John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]157\fBpng_uint_32 png_get_current_row_number \fI(png_const_structp\fP\fB);\fP
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159\fI\fB
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161\fBpng_byte png_get_current_pass_number \fI(png_const_structp\fP\fB);\fP
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163\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]165\fBpng_voidp png_get_error_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]166
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]167\fI\fB
168
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]169\fBpng_byte png_get_filter_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]170
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]171\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]173\fBpng_uint_32 png_get_gAMA (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, double \fI*file_gamma\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]174
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]175\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]177\fBpng_uint_32 png_get_gAMA_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fI*int_file_gamma\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]178
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]179\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]181\fBpng_byte png_get_header_ver (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]182
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]183\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]185\fBpng_byte png_get_header_version (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]186
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]187\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]189\fBpng_uint_32 png_get_hIST (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_16p \fI*hist\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]190
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]191\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]193\fBpng_uint_32 png_get_iCCP (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_charpp \fP\fIname\fP\fB, int \fP\fI*compression_type\fP\fB, png_bytepp \fP\fIprofile\fP\fB, png_uint_32 \fI*proflen\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]194
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]195\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]197\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
198
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]199\fI\fB
200
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]201\fBpng_uint_32 png_get_image_height (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]202
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]203\fI\fB
204
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]205\fBpng_uint_32 png_get_image_width (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]206
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]207\fI\fB
208
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]209\fBpng_int_32 png_get_int_32 (png_bytep \fIbuf\fP\fB);\fP
210
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]211\fI\fB
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]212
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]213\fBpng_byte png_get_interlace_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]214
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]215\fI\fB
216
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]217\fBpng_const_bytep png_get_io_chunk_name (png_structp \fIpng_ptr\fP\fB);\fP
218
219\fI\fB
220
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]221\fBpng_uint_32 png_get_io_chunk_type (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona63dbed2011-01-22 08:51:19 -0600[diff] [blame]222
223\fI\fB
224
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]225\fBpng_voidp png_get_io_ptr (png_structp \fIpng_ptr\fP\fB);\fP
226
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]227\fI\fB
228
Glenn Randers-Pehrsona63dbed2011-01-22 08:51:19 -0600[diff] [blame]229\fBpng_uint_32 png_get_io_state (png_structp \fIpng_ptr\fP\fB);\fP
230
231\fI\fB
232
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]233\fBpng_byte png_get_libpng_ver (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]234
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]235\fI\fB
236
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]237\fBpng_voidp png_get_mem_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]238
239\fI\fB
240
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]241\fBpng_uint_32 png_get_oFFs (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*offset_x\fP\fB, png_uint_32 \fP\fI*offset_y\fP\fB, int \fI*unit_type\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]242
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]243\fI\fB
244
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]245\fBpng_uint_32 png_get_pCAL (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fI*purpose\fP\fB, png_int_32 \fP\fI*X0\fP\fB, png_int_32 \fP\fI*X1\fP\fB, int \fP\fI*type\fP\fB, int \fP\fI*nparams\fP\fB, png_charp \fP\fI*units\fP\fB, png_charpp \fI*params\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]246
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]247\fI\fB
248
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]249\fBpng_uint_32 png_get_pHYs (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*res_x\fP\fB, png_uint_32 \fP\fI*res_y\fP\fB, int \fI*unit_type\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]250
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]251\fI\fB
252
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]253\fBfloat png_get_pixel_aspect_ratio (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]254
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]255\fI\fB
256
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]257\fBpng_uint_32 png_get_pHYs_dpi (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*res_x\fP\fB, png_uint_32 \fP\fI*res_y\fP\fB, int \fI*unit_type\fP\fB);\fP
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]258
259\fI\fB
260
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]261\fBpng_fixed_point png_get_pixel_aspect_ratio_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]262
263\fI\fB
264
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]265\fBpng_uint_32 png_get_pixels_per_inch (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]266
267\fI\fB
268
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]269\fBpng_uint_32 png_get_pixels_per_meter (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]270
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]271\fI\fB
272
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]273\fBpng_voidp png_get_progressive_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]274
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]275\fI\fB
276
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]277\fBpng_uint_32 png_get_PLTE (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_colorp \fP\fI*palette\fP\fB, int \fI*num_palette\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]278
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]279\fI\fB
280
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]281\fBpng_byte png_get_rgb_to_gray_status (png_const_structp \fIpng_ptr)
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]282
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]283\fBpng_uint_32 png_get_rowbytes (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]284
285\fI\fB
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]286
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]287\fBpng_bytepp png_get_rows (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]288
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]289\fI\fB
290
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]291\fBpng_uint_32 png_get_sBIT (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_8p \fI*sig_bit\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]292
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]293\fI\fB
294
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]295\fBvoid png_get_sCAL (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int* \fP\fIunit\fP\fB, double* \fP\fIwidth\fP\fB, double* \fIheight\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]296
297\fI\fB
298
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]299\fBvoid png_get_sCAL_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int* \fP\fIunit\fP\fB, png_fixed_pointp \fP\fIwidth\fP\fB, png_fixed_pointp \fIheight\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]300
301\fI\fB
302
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]303\fBvoid png_get_sCAL_s (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int* \fP\fIunit\fP\fB, png_charpp \fP\fIwidth\fP\fB, png_charpp \fIheight\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]304
305\fI\fB
306
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]307\fBpng_bytep png_get_signature (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]308
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]309\fI\fB
310
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]311\fBpng_uint_32 png_get_sPLT (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_spalette_p \fI*splt_ptr\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]312
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]313\fI\fB
314
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]315\fBpng_uint_32 png_get_sRGB (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int \fI*file_srgb_intent\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]316
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]317\fI\fB
318
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]319\fBpng_uint_32 png_get_text (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_textp \fP\fI*text_ptr\fP\fB, int \fI*num_text\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]320
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]321\fI\fB
322
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]323\fBpng_uint_32 png_get_tIME (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fI*mod_time\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]324
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]325\fI\fB
326
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]327\fBpng_uint_32 png_get_tRNS (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fI*trans_alpha\fP\fB, int \fP\fI*num_trans\fP\fB, png_color_16p \fI*trans_color\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]328
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]329\fI\fB
330
331\fB/* This function is really an inline macro. \fI*/
332
333\fBpng_uint_16 png_get_uint_16 (png_bytep \fIbuf\fP\fB);\fP
334
335\fI\fB
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]336
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]337\fBpng_uint_32 png_get_uint_31 (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIbuf\fP\fB);\fP
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]338
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]339\fI\fB
340
341\fB/* This function is really an inline macro. \fI*/
342
343\fBpng_uint_32 png_get_uint_32 (png_bytep \fIbuf\fP\fB);\fP
344
345\fI\fB
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]346
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]347\fBpng_uint_32 png_get_unknown_chunks (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_unknown_chunkpp \fIunknowns\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]348
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]349\fI\fB
350
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]351\fBpng_voidp png_get_user_chunk_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]352
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]353\fI\fB
354
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]355\fBpng_uint_32 png_get_user_height_max (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]356
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]357\fI\fB
358
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]359\fBpng_voidp png_get_user_transform_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]360
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]361\fI\fB
362
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]363\fBpng_uint_32 png_get_user_width_max (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]364
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]365\fI\fB
366
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]367\fBpng_uint_32 png_get_valid (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fIflag\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]368
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]369\fI\fB
370
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]371\fBfloat png_get_x_offset_inches (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]372
373\fI\fB
374
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]375\fBpng_fixed_point png_get_x_offset_inches_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]376
377\fI\fB
378
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]379\fBpng_int_32 png_get_x_offset_microns (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]380
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]381\fI\fB
382
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]383\fBpng_int_32 png_get_x_offset_pixels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]384
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]385\fI\fB
386
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]387\fBpng_uint_32 png_get_x_pixels_per_inch (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]388
389\fI\fB
390
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]391\fBpng_uint_32 png_get_x_pixels_per_meter (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]392
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]393\fI\fB
394
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]395\fBfloat png_get_y_offset_inches (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]396
397\fI\fB
398
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]399\fBpng_fixed_point png_get_y_offset_inches_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]400
401\fI\fB
402
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]403\fBpng_int_32 png_get_y_offset_microns (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]404
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]405\fI\fB
406
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]407\fBpng_int_32 png_get_y_offset_pixels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]408
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]409\fI\fB
410
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]411\fBpng_uint_32 png_get_y_pixels_per_inch (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]412
413\fI\fB
414
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]415\fBpng_uint_32 png_get_y_pixels_per_meter (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]416
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]417\fI\fB
418
Glenn Randers-Pehrsonc1bfe682002-03-06 22:08:00 -0600[diff] [blame]419\fBint png_handle_as_unknown (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIchunk_name\fP\fB);\fP
420
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]421\fI\fB
422
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]423\fBvoid png_info_init_3 (png_infopp \fP\fIinfo_ptr\fP\fB, png_size_t \fIpng_info_struct_size\fP\fB);\fP
424
425\fI\fB
426
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]427\fBvoid png_init_io (png_structp \fP\fIpng_ptr\fP\fB, FILE \fI*fp\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]428
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]429\fI\fB
430
Glenn Randers-Pehrsonf98726a2010-02-19 09:54:53 -0600[diff] [blame]431\fBvoid png_longjmp (png_structp \fP\fIpng_ptr\fP\fB, int \fIval\fP\fB);\fP
432
433\fI\fB
434
Glenn Randers-Pehrsonbeb572e2006-08-19 13:59:24 -0500[diff] [blame]435\fBpng_voidp png_malloc (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]436
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]437\fI\fB
438
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]439\fBpng_voidp png_malloc_default (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP
440
441\fI\fB
442
443\fBpng_voidp png_malloc_warn (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP
444
445\fI\fB
446
447\fBpng_uint_32 png_permit_mng_features (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fImng_features_permitted\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]448
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]449\fI\fB
450
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]451\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
452
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]453\fI\fB
454
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]455\fBpng_size_t png_process_data_pause \fP\fI(png_structp\fP\fB, int \fIsave\fP\fB);\fP
456
457\fI\fB
458
459\fBpng_uint_32 png_process_data_skip \fI(png_structp\fP\fB);\fP
460
461\fI\fB
462
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]463\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
464
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]465\fI\fB
466
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]467\fBvoid png_read_end (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
468
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]469\fI\fB
470
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]471\fBvoid png_read_image (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fIimage\fP\fB);\fP
472
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]473\fI\fB
474
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]475\fBvoid png_read_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
476
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]477\fI\fB
478
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]479\fBvoid png_read_png (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fItransforms\fP\fB, png_voidp \fIparams\fP\fB);\fP
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]480
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]481\fI\fB
482
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]483\fBvoid png_read_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIrow\fP\fB, png_bytep \fIdisplay_row\fP\fB);\fP
484
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]485\fI\fB
486
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]487\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
488
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]489\fI\fB
490
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]491\fBvoid png_read_update_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
492
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]493\fI\fB
494
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]495\fBint png_reset_zstream (png_structp \fIpng_ptr\fP\fB);\fP
496
497\fI\fB
498
499\fBvoid png_save_int_32 (png_bytep \fP\fIbuf\fP\fB, png_int_32 \fIi\fP\fB);\fP
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]500
501\fI\fB
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]502
503\fBvoid png_save_uint_16 (png_bytep \fP\fIbuf\fP\fB, unsigned int \fIi\fP\fB);\fP
504
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]505\fI\fB
506
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]507\fBvoid png_save_uint_32 (png_bytep \fP\fIbuf\fP\fB, png_uint_32 \fIi\fP\fB);\fP
508
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]509\fI\fB
510
511\fBvoid png_set_add_alpha (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIfiller\fP\fB, int \fIflags\fP\fB);\fP
512
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]513\fI\fB
Glenn Randers-Pehrson67864af2004-08-28 23:30:07 -0500[diff] [blame]514
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]515\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
516
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]517\fI\fB
518
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]519\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
520
521\fI\fB
522
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]523\fBvoid png_set_benign_errors (png_structp \fP\fIpng_ptr\fP\fB, int \fIallowed\fP\fB);\fP
524
525\fI\fB
526
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]527\fBvoid png_set_bgr (png_structp \fIpng_ptr\fP\fB);\fP
528
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]529\fI\fB
530
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]531\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
532
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]533\fI\fB
534
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]535\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
536
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]537\fI\fB
538
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]539\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
540
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]541\fI\fB
542
Glenn Randers-Pehrson800d1e92008-08-20 17:25:21 -0500[diff] [blame]543\fBvoid png_set_chunk_cache_max (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIuser_chunk_cache_max\fP\fB);\fP
544
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]545\fI\fB
546
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]547\fBvoid png_set_compression_level (png_structp \fP\fIpng_ptr\fP\fB, int \fIlevel\fP\fB);\fP
548
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]549\fI\fB
550
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]551\fBvoid png_set_compression_mem_level (png_structp \fP\fIpng_ptr\fP\fB, int \fImem_level\fP\fB);\fP
552
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]553\fI\fB
554
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]555\fBvoid png_set_compression_method (png_structp \fP\fIpng_ptr\fP\fB, int \fImethod\fP\fB);\fP
556
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]557\fI\fB
558
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]559\fBvoid png_set_compression_strategy (png_structp \fP\fIpng_ptr\fP\fB, int \fIstrategy\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]560
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]561\fI\fB
562
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]563\fBvoid png_set_compression_window_bits (png_structp \fP\fIpng_ptr\fP\fB, int \fIwindow_bits\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]564
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]565\fI\fB
566
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]567\fBvoid png_set_crc_action (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIcrit_action\fP\fB, int \fIancil_action\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]568
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]569\fI\fB
570
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]571\fBvoid png_set_error_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarning_fn\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]572
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]573\fI\fB
574
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]575\fBvoid png_set_expand (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]576
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]577\fI\fB
578
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]579\fBvoid png_set_expand_gray_1_2_4_to_8 (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson1ce08362006-03-08 23:35:59 -0600[diff] [blame]580
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]581\fI\fB
582
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]583\fBvoid png_set_filler (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIfiller\fP\fB, int \fIflags\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]584
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]585\fI\fB
586
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]587\fBvoid png_set_filter (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fImethod\fP\fB, int \fIfilters\fP\fB);\fP
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]588
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]589\fI\fB
590
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]591\fBvoid png_set_filter_heuristics (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIheuristic_method\fP\fB, int \fP\fInum_weights\fP\fB, png_doublep \fP\fIfilter_weights\fP\fB, png_doublep \fIfilter_costs\fP\fB);\fP
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]592
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]593\fI\fB
594
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]595\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
596
597\fI\fB
598
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]599\fBvoid png_set_flush (png_structp \fP\fIpng_ptr\fP\fB, int \fInrows\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]600
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]601\fI\fB
602
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]603\fBvoid png_set_gamma (png_structp \fP\fIpng_ptr\fP\fB, double \fP\fIscreen_gamma\fP\fB, double \fIdefault_file_gamma\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]604
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]605\fI\fB
606
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]607\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
608
609\fI\fB
610
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]611\fBvoid png_set_gAMA (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fIfile_gamma\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]612
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]613\fI\fB
614
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]615\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
616
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]617\fI\fB
618
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]619\fBvoid png_set_gray_1_2_4_to_8 (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]620
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]621\fI\fB
622
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]623\fBvoid png_set_gray_to_rgb (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]624
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]625\fI\fB
626
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]627\fBvoid png_set_hIST (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_16p \fIhist\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]628
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]629\fI\fB
630
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]631\fBvoid png_set_iCCP (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_const_charp \fP\fIname\fP\fB, int \fP\fIcompression_type\fP\fB, png_const_bytep \fP\fIprofile\fP\fB, png_uint_32 \fIproflen\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]632
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]633\fI\fB
634
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]635\fBint png_set_interlace_handling (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]636
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]637\fI\fB
638
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]639\fBvoid png_set_invalid (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fImask\fP\fB);\fP
640
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]641\fI\fB
642
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]643\fBvoid png_set_invert_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]644
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]645\fI\fB
646
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]647\fBvoid png_set_invert_mono (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]648
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]649\fI\fB
650
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]651\fBvoid png_set_IHDR (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIwidth\fP\fB, png_uint_32 \fP\fIheight\fP\fB, int \fP\fIbit_depth\fP\fB, int \fP\fIcolor_type\fP\fB, int \fP\fIinterlace_type\fP\fB, int \fP\fIcompression_type\fP\fB, int \fIfilter_type\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]652
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]653\fI\fB
654
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]655\fBvoid png_set_keep_unknown_chunks (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIkeep\fP\fB, png_bytep \fP\fIchunk_list\fP\fB, int \fInum_chunks\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]656
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]657\fI\fB
658
Glenn Randers-Pehrson1e6ed732009-11-20 22:06:56 -0600[diff] [blame]659\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
660
661\fI\fB
662
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]663\fBvoid png_set_chunk_malloc_max (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIuser_chunk_cache_max\fP\fB);\fP
664
665\fI\fB
666
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]667\fBvoid png_set_compression_buffer_size (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP
668
669\fI\fB
670
671\fBvoid png_set_mem_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]672
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]673\fI\fB
674
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]675\fBvoid png_set_oFFs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIoffset_x\fP\fB, png_uint_32 \fP\fIoffset_y\fP\fB, int \fIunit_type\fP\fB);\fP
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]676
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]677\fI\fB
678
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]679\fBvoid png_set_packing (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]680
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]681\fI\fB
682
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]683\fBvoid png_set_packswap (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]684
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]685\fI\fB
686
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]687\fBvoid png_set_palette_to_rgb (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]688
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]689\fI\fB
690
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]691\fBvoid png_set_pCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fIpurpose\fP\fB, png_int_32 \fP\fIX0\fP\fB, png_int_32 \fP\fIX1\fP\fB, int \fP\fItype\fP\fB, int \fP\fInparams\fP\fB, png_charp \fP\fIunits\fP\fB, png_charpp \fIparams\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]692
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]693\fI\fB
694
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]695\fBvoid png_set_pHYs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIres_x\fP\fB, png_uint_32 \fP\fIres_y\fP\fB, int \fIunit_type\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]696
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]697\fI\fB
698
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]699\fBvoid png_set_progressive_read_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIprogressive_ptr\fP\fB, png_progressive_info_ptr \fP\fIinfo_fn\fP\fB, png_progressive_row_ptr \fP\fIrow_fn\fP\fB, png_progressive_end_ptr \fIend_fn\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]700
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]701\fI\fB
702
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]703\fBvoid png_set_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_colorp \fP\fIpalette\fP\fB, int \fInum_palette\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]704
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]705\fI\fB
706
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]707\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
708
709\fI\fB
710
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]711\fBvoid png_set_read_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIio_ptr\fP\fB, png_rw_ptr \fIread_data_fn\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]712
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]713\fI\fB
714
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]715\fBvoid png_set_read_status_fn (png_structp \fP\fIpng_ptr\fP\fB, png_read_status_ptr \fIread_row_fn\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]716
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]717\fI\fB
718
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]719\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
720
721\fI\fB
722
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]723\fBvoid png_set_read_user_transform_fn (png_structp \fP\fIpng_ptr\fP\fB, png_user_transform_ptr \fIread_user_transform_fn\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]724
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]725\fI\fB
726
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]727\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
728
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]729\fI\fB
730
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]731\fBvoid png_set_rgb_to_gray_fixed (png_structp \fP\fIpng_ptr\fP\fB, int error_action png_uint_32 \fP\fIred\fP\fB, png_uint_32 \fIgreen\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]732
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]733\fI\fB
734
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]735\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
736
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]737\fI\fB
738
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]739\fBvoid png_set_sBIT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_8p \fIsig_bit\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]740
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]741\fI\fB
742
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]743\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
744
745\fI\fB
746
747\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
748
749\fI\fB
750
751\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
752
753\fI\fB
754
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]755\fBvoid png_set_shift (png_structp \fP\fIpng_ptr\fP\fB, png_color_8p \fItrue_bits\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]756
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]757\fI\fB
758
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]759\fBvoid png_set_sig_bytes (png_structp \fP\fIpng_ptr\fP\fB, int \fInum_bytes\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]760
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]761\fI\fB
762
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]763\fBvoid png_set_sPLT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_spalette_p \fP\fIsplt_ptr\fP\fB, int \fInum_spalettes\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]764
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]765\fI\fB
766
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]767\fBvoid png_set_sRGB (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIsrgb_intent\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]768
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]769\fI\fB
770
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]771\fBvoid png_set_sRGB_gAMA_and_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIsrgb_intent\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]772
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]773\fI\fB
774
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]775\fBvoid png_set_strip_16 (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]776
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]777\fI\fB
778
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]779\fBvoid png_set_strip_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]780
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]781\fI\fB
782
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]783\fBvoid png_set_strip_error_numbers (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIstrip_mode\fP\fB);\fP
784
785\fI\fB
786
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]787\fBvoid png_set_swap (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]788
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]789\fI\fB
790
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]791\fBvoid png_set_swap_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]792
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]793\fI\fB
794
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]795\fBvoid png_set_text (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_textp \fP\fItext_ptr\fP\fB, int \fInum_text\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]796
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]797\fI\fB
798
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]799\fBvoid png_set_tIME (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fImod_time\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]800
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]801\fI\fB
802
Glenn Randers-Pehrsonf3c51e42011-01-15 10:25:25 -0600[diff] [blame]803\fBvoid png_set_tRNS (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fItrans_alpha\fP\fB, int \fP\fInum_trans\fP\fB, png_color_16p \fItrans_color\fP\fB);\fP
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]804
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]805\fI\fB
806
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]807\fBvoid png_set_tRNS_to_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]808
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]809\fI\fB
810
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]811\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
812
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]813\fI\fB
814
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]815\fBvoid png_set_unknown_chunk_location (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIchunk\fP\fB, int \fIlocation\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]816
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]817\fI\fB
818
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]819\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
820
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]821\fI\fB
822
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]823\fBvoid png_set_user_transform_info (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIuser_transform_ptr\fP\fB, int \fP\fIuser_transform_depth\fP\fB, int \fIuser_transform_channels\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]824
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]825\fI\fB
826
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]827\fBvoid png_set_write_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIio_ptr\fP\fB, png_rw_ptr \fP\fIwrite_data_fn\fP\fB, png_flush_ptr \fIoutput_flush_fn\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]828
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]829\fI\fB
830
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]831\fBvoid png_set_write_status_fn (png_structp \fP\fIpng_ptr\fP\fB, png_write_status_ptr \fIwrite_row_fn\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]832
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]833\fI\fB
834
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]835\fBvoid png_set_write_user_transform_fn (png_structp \fP\fIpng_ptr\fP\fB, png_user_transform_ptr \fIwrite_user_transform_fn\fP\fB);\fP
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]836
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]837\fI\fB
838
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]839\fBint png_sig_cmp (png_bytep \fP\fIsig\fP\fB, png_size_t \fP\fIstart\fP\fB, png_size_t \fInum_to_check\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]840
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]841\fI\fB
842
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]843\fBvoid png_start_read_image (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]844
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]845\fI\fB
846
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]847\fBvoid png_warning (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fImessage\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]848
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]849\fI\fB
850
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]851\fBvoid png_write_chunk (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIchunk_name\fP\fB, png_bytep \fP\fIdata\fP\fB, png_size_t \fIlength\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]852
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]853\fI\fB
854
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]855\fBvoid png_write_chunk_data (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIdata\fP\fB, png_size_t \fIlength\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]856
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]857\fI\fB
858
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]859\fBvoid png_write_chunk_end (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]860
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]861\fI\fB
862
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]863\fBvoid png_write_chunk_start (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIchunk_name\fP\fB, png_uint_32 \fIlength\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]864
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]865\fI\fB
866
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]867\fBvoid png_write_end (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]868
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]869\fI\fB
870
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]871\fBvoid png_write_flush (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]872
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]873\fI\fB
874
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]875\fBvoid png_write_image (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fIimage\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]876
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]877\fI\fB
878
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]879\fBvoid png_write_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]880
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]881\fI\fB
882
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]883\fBvoid png_write_info_before_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
884
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]885\fI\fB
886
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]887\fBvoid png_write_png (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fItransforms\fP\fB, png_voidp \fIparams\fP\fB);\fP
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]888
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]889\fI\fB
890
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]891\fBvoid png_write_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIrow\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]892
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]893\fI\fB
894
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]895\fBvoid png_write_rows (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fP\fIrow\fP\fB, png_uint_32 \fInum_rows\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]896
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]897\fI\fB
898
Glenn Randers-Pehrson6bc53be2006-06-16 07:52:03 -0500[diff] [blame]899\fBvoid png_write_sig (png_structp \fIpng_ptr\fP\fB);\fP
900
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]901\fI\fB
902
Glenn Randers-Pehrson5b5dcf82004-07-17 22:45:44 -0500[diff] [blame]903\fBvoidpf png_zalloc (voidpf \fP\fIpng_ptr\fP\fB, uInt \fP\fIitems\fP\fB, uInt \fIsize\fP\fB);\fP
904
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]905\fI\fB
906
Glenn Randers-Pehrson5b5dcf82004-07-17 22:45:44 -0500[diff] [blame]907\fBvoid png_zfree (voidpf \fP\fIpng_ptr\fP\fB, voidpf \fIptr\fP\fB);\fP
908
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]909\fI\fB
910
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]911.SH DESCRIPTION
912The
913.I libpng
914library supports encoding, decoding, and various manipulations of
915the Portable Network Graphics (PNG) format image files. It uses the
916.IR zlib(3)
917compression library.
Glenn Randers-Pehrson557b2562010-10-17 12:55:04 -0500[diff] [blame]918Following is a copy of the libpng-manual.txt file that accompanies libpng.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]919.SH LIBPNG.TXT
Glenn Randers-Pehrson557b2562010-10-17 12:55:04 -0500[diff] [blame]920libpng-manual.txt - A description on how to use and modify libpng
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]921
Glenn Randers-Pehrson0012e9c2011-01-26 22:04:03 -0600[diff] [blame]922 libpng version 1.5.1beta10 - January 27, 2011
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]923 Updated and distributed by Glenn Randers-Pehrson
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]924 <glennrp at users.sourceforge.net>
Glenn Randers-Pehrson9f45c8e2011-01-15 19:35:03 -0600[diff] [blame]925 Copyright (c) 1998-2011 Glenn Randers-Pehrson
Glenn Randers-Pehrson037023b2009-06-24 10:27:36 -0500[diff] [blame]926
Glenn Randers-Pehrsonbfbf8652009-06-26 21:46:52 -0500[diff] [blame]927 This document is released under the libpng license.
Glenn Randers-Pehrsonc332bbc2009-06-25 13:43:50 -0500[diff] [blame]928 For conditions of distribution and use, see the disclaimer
Glenn Randers-Pehrson037023b2009-06-24 10:27:36 -0500[diff] [blame]929 and license in png.h
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]930
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]931 Based on:
932
Glenn Randers-Pehrson0012e9c2011-01-26 22:04:03 -0600[diff] [blame]933 libpng versions 0.97, January 1998, through 1.5.1beta10 - January 27, 2011
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]934 Updated and distributed by Glenn Randers-Pehrson
Glenn Randers-Pehrson9f45c8e2011-01-15 19:35:03 -0600[diff] [blame]935 Copyright (c) 1998-2011 Glenn Randers-Pehrson
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]936
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]937 libpng 1.0 beta 6 version 0.96 May 28, 1997
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]938 Updated and distributed by Andreas Dilger
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]939 Copyright (c) 1996, 1997 Andreas Dilger
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]940
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]941 libpng 1.0 beta 2 - version 0.88 January 26, 1996
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]942 For conditions of distribution and use, see copyright
943 notice in png.h. Copyright (c) 1995, 1996 Guy Eric
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]944 Schalnat, Group 42, Inc.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]945
946 Updated/rewritten per request in the libpng FAQ
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]947 Copyright (c) 1995, 1996 Frank J. T. Wojcik
948 December 18, 1995 & January 20, 1996
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]949
950.SH I. Introduction
951
952This file describes how to use and modify the PNG reference library
953(known as libpng) for your own use. There are five sections to this
954file: introduction, structures, reading, writing, and modification and
955configuration notes for various special platforms. In addition to this
956file, example.c is a good starting point for using the library, as
957it is heavily commented and should include everything most people
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]958will need. We assume that libpng is already installed; see the
959INSTALL file for instructions on how to install libpng.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]960
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]961For examples of libpng usage, see the files "example.c", "pngtest.c",
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]962and the files in the "contrib" directory, all of which are included in
963the libpng distribution.
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]964
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]965Libpng was written as a companion to the PNG specification, as a way
966of reducing the amount of time and effort it takes to support the PNG
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]967file format in application programs.
968
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]969The PNG specification (second edition), November 2003, is available as
970a W3C Recommendation and as an ISO Standard (ISO/IEC 15948:2003 (E)) at
971<http://www.w3.org/TR/2003/REC-PNG-20031110/
972The W3C and ISO documents have identical technical content.
973
974The PNG-1.2 specification is available at
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]975<http://www.libpng.org/pub/png/documents/>. It is technically equivalent
976to the PNG specification (second edition) but has some additional material.
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]977
978The PNG-1.0 specification is available
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]979as RFC 2083 <http://www.libpng.org/pub/png/documents/> and as a
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]980W3C Recommendation <http://www.w3.org/TR/REC.png.html>.
981
982Some additional chunks are described in the special-purpose public chunks
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]983documents at <http://www.libpng.org/pub/png/documents/>.
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]984
985Other information
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]986about PNG, and the latest version of libpng, can be found at the PNG home
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]987page, <http://www.libpng.org/pub/png/>.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]988
989Most users will not have to modify the library significantly; advanced
990users may want to modify it more. All attempts were made to make it as
991complete as possible, while keeping the code easy to understand.
992Currently, this library only supports C. Support for other languages
993is being considered.
994
995Libpng has been designed to handle multiple sessions at one time,
996to be easily modifiable, to be portable to the vast majority of
997machines (ANSI, K&R, 16-, 32-, and 64-bit) available, and to be easy
998to use. The ultimate goal of libpng is to promote the acceptance of
999the PNG file format in whatever way possible. While there is still
1000work to be done (see the TODO file), libpng should cover the
1001majority of the needs of its users.
1002
1003Libpng uses zlib for its compression and decompression of PNG files.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1004Further information about zlib, and the latest version of zlib, can
Glenn Randers-Pehrsond56aca72000-11-23 11:51:42 -0600[diff] [blame]1005be found at the zlib home page, <http://www.info-zip.org/pub/infozip/zlib/>.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1006The zlib compression utility is a general purpose utility that is
1007useful for more than PNG files, and can be used without libpng.
1008See the documentation delivered with zlib for more details.
1009You can usually find the source files for the zlib utility wherever you
1010find the libpng source files.
1011
1012Libpng is thread safe, provided the threads are using different
1013instances of the structures. Each thread should have its own
1014png_struct and png_info instances, and thus its own image.
1015Libpng does not protect itself against two threads using the
Glenn Randers-Pehrson56f63962008-10-06 10:16:17 -0500[diff] [blame]1016same instance of a structure.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1017
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1018.SH II. Structures
1019
1020There are two main structures that are important to libpng, png_struct
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]1021and png_info. Both are internal structures that are no longer exposed
1022in the libpng interface (as of libpng 1.5.0).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1023
1024The png_info structure is designed to provide information about the
1025PNG file. At one time, the fields of png_info were intended to be
1026directly accessible to the user. However, this tended to cause problems
1027with applications using dynamically loaded libraries, and as a result
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]1028a set of interface functions for png_info (the png_get_*() and png_set_*()
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]1029functions) was developed.
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]1030
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]1031The png_struct structure is the object used by the library to decode a
1032single image. As of 1.5.0 this structure is also not exposed.
1033
1034Almost all libpng APIs require a pointer to a png_struct as the first argument.
1035Many (in particular the png_set and png_get APIs) also require a pointer
1036to png_info as the second argument. Some application visible macros
1037defined in png.h designed for basic data access (reading and writing
1038integers in the PNG format) break this rule, but it's almost always safe
1039to assume that a (png_struct*) has to be passed to call an API function.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1040
1041The png.h header file is an invaluable reference for programming with libpng.
1042And while I'm on the topic, make sure you include the libpng header file:
1043
1044#include <png.h>
1045
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]1046.SS Types
1047
1048The png.h header file defines a number of integral types used by the
1049APIs. Most of these are fairly obvious; for example types corresponding
1050to integers of particular sizes and types for passing color values.
1051
1052One exception is how non-integral numbers are handled. For application
1053convenience most APIs that take such numbers have C (double) arguments,
1054however internally PNG, and libpng, use 32 bit signed integers and encode
1055the value by multiplying by 100,000. As of libpng 1.5.0 a convenience
1056macro PNG_FP_1 is defined in png.h along with a type (png_fixed_point)
1057which is simply (png_int_32).
1058
1059All APIs that take (double) arguments also have an matching API that
1060takes the corresponding fixed point integer arguments. The fixed point
1061API has the same name as the floating point one with _fixed appended.
1062The actual range of values permitted in the APIs is frequently less than
1063the full range of (png_fixed_point) (-21474 to +21474). When APIs require
1064a non-negative argument the type is recorded as png_uint_32 above. Consult
1065the header file and the text below for more information.
1066
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]1067Special care must be take with sCAL chunk handling because the chunk itself
1068uses non-integral values encoded as strings containing decimal floating point
1069numbers. See the comments in the header file.
1070
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]1071.SS Configuration
1072
1073The main header file function declarations are frequently protected by C
1074preprocessing directives of the form:
1075
1076 #ifdef PNG_feature_SUPPORTED
1077 declare-function
1078 #endif
1079
1080The library can be built without support for these APIs, although a
1081standard build will have all implemented APIs. Application programs
1082should check the feature macros before using an API for maximum
1083portability. From libpng 1.5.0 the feature macros set during the build
1084of libpng are recorded in the header file "pnglibconf.h" and this file
1085is always included by png.h.
1086
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]1087If you don't need to change the library configuration from the default skip to
1088the next section ("Reading").
1089
1090Notice that some of the makefiles in the 'scripts' directory and (in 1.5.0) all
1091of the build project files in the 'projects' directory simply copy
1092scripts/pnglibconf.h.prebuilt to pnglibconf.h. This means that these build
1093systems do not permit easy auto-configuration of the library - they only
1094support the default configuration.
1095
1096The easiest way to make minor changes to the libpng configuration when
1097auto-configuration is supported is to add definitions to the command line
1098using (typically) CPPFLAGS. For example:
1099
1100CPPFLAGS=-DPNG_NO_FLOATING_ARITHMETIC
1101
1102will change the internal libpng math implementation for gamma correction and
1103other arithmetic calculations to fixed point, avoiding the need for fast
1104floating point support. The result can be seen in the generated pnglibconf.h -
1105make sure it contains the changed feature macro setting.
1106
1107If you need to make more extensive configuration changes - more than one or two
1108feature macro settings - you can either add -DPNG_USER_CONFIG to the build
1109command line and put a list of feature macro settings in pngusr.h or you can set
1110DFA_XTRA (a makefile variable) to a file containing the same information in the
1111form of 'option' settings.
1112
1113A. Changing pnglibconf.h
1114
1115A variety of methods exist to build libpng. Not all of these support
1116reconfiguration of pnglibconf.h. To reconfigure pnglibconf.h it must either be
1117rebuilt from scripts/pnglibconf.dfa using awk or it must be edited by hand.
1118
1119Hand editing is achieved by copying scripts/pnglibconf.h.prebuilt and changing
1120the lines defining the supported features, paying very close attention to the
1121'option' information in scripts/pnglibconf.dfa that describes those features and
1122their requirements. This is easy to get wrong.
1123
1124B. Configuration using DFA_XTRA
1125
1126Rebuilding from pnglibconf.dfa is easy if a functioning 'awk', or a later
1127variant such as 'nawk' or 'gawk', is available. The configure build will
1128automatically find an appropriate awk and build pnglibconf.h.
1129scripts/pnglibconf.mak contains a set of make rules for doing the same thing if
1130configure is not used, and many of the makefiles in the scripts directory use
1131this approach.
1132
1133When rebuilding simply write new file containing changed options and set
1134DFA_XTRA to the name of this file. This causes the build to append the new file
1135to the end of scripts/pnglibconf.dfa. pngusr.dfa should contain lines of the
1136following forms:
1137
1138everything = off
1139
1140This turns all optional features off. Include it at the start of pngusr.dfa to
1141make it easier to build a minimal configuration. You will need to turn at least
1142some features on afterward to enable either reading or writing code, or both.
1143
1144option feature on
1145option feature off
1146
1147Enable or disable a single feature. This will automatically enable other
1148features required by a feature that is turned on or disable other features that
1149require a feature which is turned off. Conflicting settings will cause an error
1150message to be emitted by awk.
1151
1152setting feature default value
1153
1154Changes the default value of setting 'feature' to 'value'. There are a small
1155number of settings listed at the top of pnglibconf.h, they are documented in the
1156source code. Most of these values have performance implications for the library
1157but most of them have no visible effect on the API. Some can also be overridden
1158from the API.
1159
1160C. Configuration using PNG_USR_CONFIG
1161
1162If -DPNG_USR_CONFIG is added to the CFLAGS when pnglibconf.h is built the file
1163pngusr.h will automatically be included before the options in
1164scripts/pnglibconf.dfa are processed. pngusr.h should contain only macro
1165definitions turning features on or off or setting settings.
1166
1167Apart from the global setting "everything = off" all the options listed above
1168can be set using macros in pngusr.h:
1169
1170#define PNG_feature_SUPPORTED
1171
1172is equivalent to:
1173
1174option feature on
1175
1176#define PNG_NO_feature
1177
1178is equivalent to:
1179
1180option feature off
1181
1182#define PNG_feature value
1183
1184is equivalent to:
1185
1186setting feature default value
1187
1188Notice that in both cases, pngusr.dfa and pngusr.h, the contents of the
1189pngusr file you supply override the contents of scripts/pnglibconf.dfa
1190
1191If confusing or incomprehensible behavior results it is possible to
1192examine the intermediate file pnglibconf.dfn to find the full set of
1193dependency information for each setting and option. Simply locate the
1194feature in the file and read the C comments that precede it.
1195
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1196.SH III. Reading
1197
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1198We'll now walk you through the possible functions to call when reading
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1199in a PNG file sequentially, briefly explaining the syntax and purpose
1200of each one. See example.c and png.h for more detail. While
1201progressive reading is covered in the next section, you will still
1202need some of the functions discussed in this section to read a PNG
1203file.
1204
1205.SS Setup
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1206
1207You will want to do the I/O initialization(*) before you get into libpng,
1208so if it doesn't work, you don't have much to undo. Of course, you
1209will also want to insure that you are, in fact, dealing with a PNG
1210file. Libpng provides a simple check to see if a file is a PNG file.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1211To use it, pass in the first 1 to 8 bytes of the file to the function
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]1212png_sig_cmp(), and it will return 0 (false) if the bytes match the
1213corresponding bytes of the PNG signature, or nonzero (true) otherwise.
1214Of course, the more bytes you pass in, the greater the accuracy of the
1215prediction.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1216
1217If you are intending to keep the file pointer open for use in libpng,
1218you must ensure you don't read more than 8 bytes from the beginning
1219of the file, and you also have to make a call to png_set_sig_bytes_read()
1220with the number of bytes you read from the beginning. Libpng will
1221then only check the bytes (if any) that your program didn't read.
1222
1223(*): If you are not using the standard I/O functions, you will need
1224to replace them with custom functions. See the discussion under
1225Customizing libpng.
1226
1227
1228 FILE *fp = fopen(file_name, "rb");
1229 if (!fp)
1230 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1231 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1232 }
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1233
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1234 fread(header, 1, number, fp);
Glenn Randers-Pehrsonc9442291999-01-06 21:50:16 -0600[diff] [blame]1235 is_png = !png_sig_cmp(header, 0, number);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1236
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1237 if (!is_png)
1238 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1239 return (NOT_PNG);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1240 }
1241
1242
1243Next, png_struct and png_info need to be allocated and initialized. In
1244order to ensure that the size of these structures is correct even with a
1245dynamically linked libpng, there are functions to initialize and
1246allocate the structures. We also pass the library version, optional
1247pointers to error handling functions, and a pointer to a data struct for
1248use by the error functions, if necessary (the pointer and functions can
1249be NULL if the default error handlers are to be used). See the section
1250on Changes to Libpng below regarding the old initialization functions.
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]1251The structure allocation functions quietly return NULL if they fail to
1252create the structure, so your application should check for that.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1253
1254 png_structp png_ptr = png_create_read_struct
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1255 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1256 user_error_fn, user_warning_fn);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1257
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1258 if (!png_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1259 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1260
1261 png_infop info_ptr = png_create_info_struct(png_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1262
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1263 if (!info_ptr)
1264 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1265 png_destroy_read_struct(&png_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1266 (png_infopp)NULL, (png_infopp)NULL);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1267 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1268 }
1269
1270 png_infop end_info = png_create_info_struct(png_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1271
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1272 if (!end_info)
1273 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1274 png_destroy_read_struct(&png_ptr, &info_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1275 (png_infopp)NULL);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1276 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1277 }
1278
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]1279If you want to use your own memory allocation routines,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1280use a libpng that was built with PNG_USER_MEM_SUPPORTED defined, and use
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]1281png_create_read_struct_2() instead of png_create_read_struct():
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1282
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]1283 png_structp png_ptr = png_create_read_struct_2
1284 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
1285 user_error_fn, user_warning_fn, (png_voidp)
1286 user_mem_ptr, user_malloc_fn, user_free_fn);
1287
1288The error handling routines passed to png_create_read_struct()
1289and the memory alloc/free routines passed to png_create_struct_2()
1290are only necessary if you are not using the libpng supplied error
1291handling and memory alloc/free functions.
1292
1293When libpng encounters an error, it expects to longjmp back
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1294to your routine. Therefore, you will need to call setjmp and pass
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1295your png_jmpbuf(png_ptr). If you read the file from different
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1296routines, you will need to update the jmpbuf field every time you enter
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1297a new routine that will call a png_*() function.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1298
1299See your documentation of setjmp/longjmp for your compiler for more
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]1300information on setjmp/longjmp. See the discussion on libpng error
1301handling in the Customizing Libpng section below for more information
1302on the libpng error handling. If an error occurs, and libpng longjmp's
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1303back to your setjmp, you will want to call png_destroy_read_struct() to
1304free any memory.
1305
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1306 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1307 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1308 png_destroy_read_struct(&png_ptr, &info_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1309 &end_info);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1310 fclose(fp);
1311 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1312 }
1313
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1314If you would rather avoid the complexity of setjmp/longjmp issues,
Glenn Randers-Pehrson54ac9a92010-04-02 17:06:22 -0500[diff] [blame]1315you can compile libpng with PNG_NO_SETJMP, in which case
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1316errors will result in a call to PNG_ABORT() which defaults to abort().
1317
Glenn Randers-Pehrson54ac9a92010-04-02 17:06:22 -0500[diff] [blame]1318You can #define PNG_ABORT() to a function that does something
1319more useful than abort(), as long as your function does not
1320return.
1321
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1322Now you need to set up the input code. The default for libpng is to
1323use the C function fread(). If you use this, you will need to pass a
1324valid FILE * in the function png_init_io(). Be sure that the file is
1325opened in binary mode. If you wish to handle reading data in another
1326way, you need not call the png_init_io() function, but you must then
1327implement the libpng I/O methods discussed in the Customizing Libpng
1328section below.
1329
1330 png_init_io(png_ptr, fp);
1331
1332If you had previously opened the file and read any of the signature from
1333the beginning in order to see if this was a PNG file, you need to let
1334libpng know that there are some bytes missing from the start of the file.
1335
1336 png_set_sig_bytes(png_ptr, number);
1337
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]1338You can change the zlib compression buffer size to be used while
1339reading compressed data with
1340
1341 png_set_compression_buffer_size(png_ptr, buffer_size);
1342
1343where the default size is 8192 bytes. Note that the buffer size
1344is changed immediately and the buffer is reallocated immediately,
1345instead of setting a flag to be acted upon later.
1346
Glenn Randers-Pehrson9dd1cdf2011-01-06 21:42:36 -0600[diff] [blame]1347If you want CRC errors to be handled in a different manner than
1348the default, use
1349
1350 png_set_crc_action(png_ptr, crit_action, ancil_action);
1351
1352The values for png_set_crc_action() say how libpng is to handle CRC errors in
1353ancillary and critical chunks, and whether to use the data contained
1354therein. Note that it is impossible to "discard" data in a critical
1355chunk.
1356
1357Choices for (int) crit_action are
1358 PNG_CRC_DEFAULT 0 error/quit
1359 PNG_CRC_ERROR_QUIT 1 error/quit
1360 PNG_CRC_WARN_USE 3 warn/use data
1361 PNG_CRC_QUIET_USE 4 quiet/use data
1362 PNG_CRC_NO_CHANGE 5 use the current value
1363
1364Choices for (int) ancil_action are
1365 PNG_CRC_DEFAULT 0 error/quit
1366 PNG_CRC_ERROR_QUIT 1 error/quit
1367 PNG_CRC_WARN_DISCARD 2 warn/discard data
1368 PNG_CRC_WARN_USE 3 warn/use data
1369 PNG_CRC_QUIET_USE 4 quiet/use data
1370 PNG_CRC_NO_CHANGE 5 use the current value
1371
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1372.SS Setting up callback code
1373
1374You can set up a callback function to handle any unknown chunks in the
1375input stream. You must supply the function
1376
Glenn Randers-Pehrson81ce8892011-01-24 08:04:37 -0600[diff] [blame]1377 read_chunk_callback(png_structp png_ptr,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1378 png_unknown_chunkp chunk);
1379 {
1380 /* The unknown chunk structure contains your
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1381 chunk data, along with similar data for any other
1382 unknown chunks: */
1383
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1384 png_byte name[5];
1385 png_byte *data;
1386 png_size_t size;
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1387
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1388 /* Note that libpng has already taken care of
1389 the CRC handling */
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1390
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1391 /* put your code here. Search for your chunk in the
1392 unknown chunk structure, process it, and return one
1393 of the following: */
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1394
1395 return (-n); /* chunk had an error */
1396 return (0); /* did not recognize */
1397 return (n); /* success */
1398 }
1399
1400(You can give your function another name that you like instead of
1401"read_chunk_callback")
1402
1403To inform libpng about your function, use
1404
1405 png_set_read_user_chunk_fn(png_ptr, user_chunk_ptr,
1406 read_chunk_callback);
1407
1408This names not only the callback function, but also a user pointer that
1409you can retrieve with
1410
1411 png_get_user_chunk_ptr(png_ptr);
1412
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1413If you call the png_set_read_user_chunk_fn() function, then all unknown
1414chunks will be saved when read, in case your callback function will need
1415one or more of them. This behavior can be changed with the
1416png_set_keep_unknown_chunks() function, described below.
1417
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]1418At this point, you can set up a callback function that will be
1419called after each row has been read, which you can use to control
1420a progress meter or the like. It's demonstrated in pngtest.c.
1421You must supply a function
1422
Glenn Randers-Pehrson81ce8892011-01-24 08:04:37 -0600[diff] [blame]1423 void read_row_callback(png_structp png_ptr,
1424 png_uint_32 row, int pass);
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]1425 {
1426 /* put your code here */
1427 }
1428
1429(You can give it another name that you like instead of "read_row_callback")
1430
1431To inform libpng about your function, use
1432
1433 png_set_read_status_fn(png_ptr, read_row_callback);
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1434
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1435.SS Unknown-chunk handling
1436
1437Now you get to set the way the library processes unknown chunks in the
1438input PNG stream. Both known and unknown chunks will be read. Normal
1439behavior is that known chunks will be parsed into information in
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1440various info_ptr members while unknown chunks will be discarded. This
1441behavior can be wasteful if your application will never use some known
1442chunk types. To change this, you can call:
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1443
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]1444 png_set_keep_unknown_chunks(png_ptr, keep,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1445 chunk_list, num_chunks);
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1446 keep - 0: default unknown chunk handling
1447 1: ignore; do not keep
Glenn Randers-Pehrsond029a752004-08-09 21:50:32 -0500[diff] [blame]1448 2: keep only if safe-to-copy
1449 3: keep even if unsafe-to-copy
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1450
Glenn Randers-Pehrsond029a752004-08-09 21:50:32 -0500[diff] [blame]1451 You can use these definitions:
1452 PNG_HANDLE_CHUNK_AS_DEFAULT 0
1453 PNG_HANDLE_CHUNK_NEVER 1
1454 PNG_HANDLE_CHUNK_IF_SAFE 2
1455 PNG_HANDLE_CHUNK_ALWAYS 3
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1456
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1457 chunk_list - list of chunks affected (a byte string,
1458 five bytes per chunk, NULL or '\0' if
1459 num_chunks is 0)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1460
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1461 num_chunks - number of chunks affected; if 0, all
Glenn Randers-Pehrsondff799e2004-08-07 21:42:49 -0500[diff] [blame]1462 unknown chunks are affected. If nonzero,
1463 only the chunks in the list are affected
1464
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1465Unknown chunks declared in this way will be saved as raw data onto a
1466list of png_unknown_chunk structures. If a chunk that is normally
1467known to libpng is named in the list, it will be handled as unknown,
1468according to the "keep" directive. If a chunk is named in successive
1469instances of png_set_keep_unknown_chunks(), the final instance will
Glenn Randers-Pehrsond029a752004-08-09 21:50:32 -0500[diff] [blame]1470take precedence. The IHDR and IEND chunks should not be named in
1471chunk_list; if they are, libpng will process them normally anyway.
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1472
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1473Here is an example of the usage of png_set_keep_unknown_chunks(),
1474where the private "vpAg" chunk will later be processed by a user chunk
1475callback function:
1476
1477 png_byte vpAg[5]={118, 112, 65, 103, (png_byte) '\0'};
1478
1479 #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
1480 png_byte unused_chunks[]=
1481 {
1482 104, 73, 83, 84, (png_byte) '\0', /* hIST */
1483 105, 84, 88, 116, (png_byte) '\0', /* iTXt */
1484 112, 67, 65, 76, (png_byte) '\0', /* pCAL */
1485 115, 67, 65, 76, (png_byte) '\0', /* sCAL */
1486 115, 80, 76, 84, (png_byte) '\0', /* sPLT */
1487 116, 73, 77, 69, (png_byte) '\0', /* tIME */
1488 };
1489 #endif
1490
1491 ...
1492
1493 #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
1494 /* ignore all unknown chunks: */
1495 png_set_keep_unknown_chunks(read_ptr, 1, NULL, 0);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1496
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1497 /* except for vpAg: */
1498 png_set_keep_unknown_chunks(read_ptr, 2, vpAg, 1);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1499
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1500 /* also ignore unused known chunks: */
1501 png_set_keep_unknown_chunks(read_ptr, 1, unused_chunks,
1502 (int)sizeof(unused_chunks)/5);
1503 #endif
1504
Glenn Randers-Pehrson800d1e92008-08-20 17:25:21 -0500[diff] [blame]1505.SS User limits
1506
1507The PNG specification allows the width and height of an image to be as
1508large as 2^31-1 (0x7fffffff), or about 2.147 billion rows and columns.
1509Since very few applications really need to process such large images,
1510we have imposed an arbitrary 1-million limit on rows and columns.
1511Larger images will be rejected immediately with a png_error() call. If
1512you wish to override this limit, you can use
1513
1514 png_set_user_limits(png_ptr, width_max, height_max);
1515
1516to set your own limits, or use width_max = height_max = 0x7fffffffL
1517to allow all valid dimensions (libpng may reject some very large images
1518anyway because of potential buffer overflow conditions).
1519
1520You should put this statement after you create the PNG structure and
1521before calling png_read_info(), png_read_png(), or png_process_data().
1522If you need to retrieve the limits that are being applied, use
1523
1524 width_max = png_get_user_width_max(png_ptr);
1525 height_max = png_get_user_height_max(png_ptr);
1526
1527The PNG specification sets no limit on the number of ancillary chunks
1528allowed in a PNG datastream. You can impose a limit on the total number
1529of sPLT, tEXt, iTXt, zTXt, and unknown chunks that will be stored, with
1530
1531 png_set_chunk_cache_max(png_ptr, user_chunk_cache_max);
1532
1533where 0x7fffffffL means unlimited. You can retrieve this limit with
1534
1535 chunk_cache_max = png_get_chunk_cache_max(png_ptr);
1536
Glenn Randers-Pehrson8f5846f2009-10-31 21:31:08 -0500[diff] [blame]1537This limit also applies to the number of buffers that can be allocated
1538by png_decompress_chunk() while decompressing iTXt, zTXt, and iCCP chunks.
1539
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]1540You can also set a limit on the amount of memory that a compressed chunk
1541other than IDAT can occupy, with
1542
1543 png_set_chunk_malloc_max(png_ptr, user_chunk_malloc_max);
1544
1545and you can retrieve the limit with
1546
1547 chunk_malloc_max = png_get_chunk_malloc_max(png_ptr);
1548
1549Any chunks that would cause either of these limits to be exceeded will
1550be ignored.
1551
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1552.SS The high-level read interface
1553
1554At this point there are two ways to proceed; through the high-level
1555read interface, or through a sequence of low-level read operations.
1556You can use the high-level interface if (a) you are willing to read
1557the entire image into memory, and (b) the input transformations
1558you want to do are limited to the following set:
1559
1560 PNG_TRANSFORM_IDENTITY No transformation
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1561 PNG_TRANSFORM_STRIP_16 Strip 16-bit samples to
1562 8 bits
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1563 PNG_TRANSFORM_STRIP_ALPHA Discard the alpha channel
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1564 PNG_TRANSFORM_PACKING Expand 1, 2 and 4-bit
1565 samples to bytes
1566 PNG_TRANSFORM_PACKSWAP Change order of packed
1567 pixels to LSB first
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1568 PNG_TRANSFORM_EXPAND Perform set_expand()
1569 PNG_TRANSFORM_INVERT_MONO Invert monochrome images
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1570 PNG_TRANSFORM_SHIFT Normalize pixels to the
1571 sBIT depth
1572 PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA
1573 to BGRA
1574 PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA
1575 to AG
1576 PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity
1577 to transparency
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1578 PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples
Glenn Randers-Pehrson99708d52009-06-29 17:30:00 -0500[diff] [blame]1579 PNG_TRANSFORM_GRAY_TO_RGB Expand grayscale samples
1580 to RGB (or GA to RGBA)
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1581
1582(This excludes setting a background color, doing gamma transformation,
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]1583quantizing, and setting filler.) If this is the case, simply do this:
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1584
1585 png_read_png(png_ptr, info_ptr, png_transforms, NULL)
1586
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]1587where png_transforms is an integer containing the bitwise OR of some
1588set of transformation flags. This call is equivalent to png_read_info(),
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1589followed the set of transformations indicated by the transform mask,
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1590then png_read_image(), and finally png_read_end().
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1591
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1592(The final parameter of this call is not yet used. Someday it might point
1593to transformation parameters required by some future input transform.)
1594
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]1595You must use png_transforms and not call any png_set_transform() functions
1596when you use png_read_png().
1597
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1598After you have called png_read_png(), you can retrieve the image data
1599with
1600
1601 row_pointers = png_get_rows(png_ptr, info_ptr);
1602
1603where row_pointers is an array of pointers to the pixel data for each row:
1604
1605 png_bytep row_pointers[height];
1606
1607If you know your image size and pixel size ahead of time, you can allocate
1608row_pointers prior to calling png_read_png() with
1609
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1610 if (height > PNG_UINT_32_MAX/png_sizeof(png_byte))
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]1611 png_error (png_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1612 "Image is too tall to process in memory");
1613
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]1614 if (width > PNG_UINT_32_MAX/pixel_size)
1615 png_error (png_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1616 "Image is too wide to process in memory");
1617
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1618 row_pointers = png_malloc(png_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1619 height*png_sizeof(png_bytep));
1620
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1621 for (int i=0; i<height, i++)
1622 row_pointers[i]=NULL; /* security precaution */
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1623
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1624 for (int i=0; i<height, i++)
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1625 row_pointers[i]=png_malloc(png_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1626 width*pixel_size);
1627
Glenn Randers-Pehrsond56aca72000-11-23 11:51:42 -0600[diff] [blame]1628 png_set_rows(png_ptr, info_ptr, &row_pointers);
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1629
1630Alternatively you could allocate your image in one big block and define
1631row_pointers[i] to point into the proper places in your block.
1632
1633If you use png_set_rows(), the application is responsible for freeing
1634row_pointers (and row_pointers[i], if they were separately allocated).
1635
1636If you don't allocate row_pointers ahead of time, png_read_png() will
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1637do it, and it'll be free'ed by libpng when you call png_destroy_*().
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1638
1639.SS The low-level read interface
1640
1641If you are going the low-level route, you are now ready to read all
1642the file information up to the actual image data. You do this with a
1643call to png_read_info().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1644
1645 png_read_info(png_ptr, info_ptr);
1646
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1647This will process all chunks up to but not including the image data.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1648
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1649.SS Querying the info structure
1650
1651Functions are used to get the information from the info_ptr once it
1652has been read. Note that these fields may not be completely filled
1653in until png_read_end() has read the chunk data following the image.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1654
1655 png_get_IHDR(png_ptr, info_ptr, &width, &height,
1656 &bit_depth, &color_type, &interlace_type,
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]1657 &compression_type, &filter_method);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1658
1659 width - holds the width of the image
1660 in pixels (up to 2^31).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1661
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1662 height - holds the height of the image
1663 in pixels (up to 2^31).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1664
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1665 bit_depth - holds the bit depth of one of the
1666 image channels. (valid values are
1667 1, 2, 4, 8, 16 and depend also on
1668 the color_type. See also
1669 significant bits (sBIT) below).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1670
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1671 color_type - describes which color/alpha channels
1672 are present.
1673 PNG_COLOR_TYPE_GRAY
1674 (bit depths 1, 2, 4, 8, 16)
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1675 PNG_COLOR_TYPE_GRAY_ALPHA
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1676 (bit depths 8, 16)
1677 PNG_COLOR_TYPE_PALETTE
1678 (bit depths 1, 2, 4, 8)
1679 PNG_COLOR_TYPE_RGB
1680 (bit_depths 8, 16)
1681 PNG_COLOR_TYPE_RGB_ALPHA
1682 (bit_depths 8, 16)
1683
1684 PNG_COLOR_MASK_PALETTE
1685 PNG_COLOR_MASK_COLOR
1686 PNG_COLOR_MASK_ALPHA
1687
Glenn Randers-Pehrson2cb633b2011-01-21 08:31:29 -0600[diff] [blame]1688 interlace_type - (PNG_INTERLACE_NONE or
1689 PNG_INTERLACE_ADAM7)
1690
1691 compression_type - (must be PNG_COMPRESSION_TYPE_BASE
1692 for PNG 1.0)
1693
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]1694 filter_method - (must be PNG_FILTER_TYPE_BASE
1695 for PNG 1.0, and can also be
1696 PNG_INTRAPIXEL_DIFFERENCING if
1697 the PNG datastream is embedded in
1698 a MNG-1.0 datastream)
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1699
1700 Any or all of interlace_type, compression_type, or
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1701 filter_method can be NULL if you are
1702 not interested in their values.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1703
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1704 Note that png_get_IHDR() returns 32-bit data into
1705 the application's width and height variables.
1706 This is an unsafe situation if these are 16-bit
1707 variables. In such situations, the
1708 png_get_image_width() and png_get_image_height()
1709 functions described below are safer.
1710
1711 width = png_get_image_width(png_ptr,
1712 info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1713
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1714 height = png_get_image_height(png_ptr,
1715 info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1716
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1717 bit_depth = png_get_bit_depth(png_ptr,
1718 info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1719
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1720 color_type = png_get_color_type(png_ptr,
1721 info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1722
Glenn Randers-Pehrson2cb633b2011-01-21 08:31:29 -0600[diff] [blame]1723 interlace_type = png_get_interlace_type(png_ptr,
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1724 info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1725
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1726 compression_type = png_get_compression_type(png_ptr,
1727 info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1728
Glenn Randers-Pehrson2cb633b2011-01-21 08:31:29 -0600[diff] [blame]1729 filter_method = png_get_filter_type(png_ptr,
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1730 info_ptr);
1731
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1732 channels = png_get_channels(png_ptr, info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1733
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1734 channels - number of channels of info for the
1735 color type (valid values are 1 (GRAY,
1736 PALETTE), 2 (GRAY_ALPHA), 3 (RGB),
1737 4 (RGB_ALPHA or RGB + filler byte))
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1738
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1739 rowbytes = png_get_rowbytes(png_ptr, info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1740
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1741 rowbytes - number of bytes needed to hold a row
1742
1743 signature = png_get_signature(png_ptr, info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1744
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1745 signature - holds the signature read from the
1746 file (if any). The data is kept in
1747 the same offset it would be if the
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1748 whole signature were read (i.e. if an
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1749 application had already read in 4
1750 bytes of signature before starting
1751 libpng, the remaining 4 bytes would
1752 be in signature[4] through signature[7]
1753 (see png_set_sig_bytes())).
1754
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1755These are also important, but their validity depends on whether the chunk
1756has been read. The png_get_valid(png_ptr, info_ptr, PNG_INFO_<chunk>) and
1757png_get_<chunk>(png_ptr, info_ptr, ...) functions return non-zero if the
1758data has been read, or zero if it is missing. The parameters to the
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]1759png_get_<chunk> are set directly if they are simple data types, or a
1760pointer into the info_ptr is returned for any complex types.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1761
1762 png_get_PLTE(png_ptr, info_ptr, &palette,
1763 &num_palette);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1764
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1765 palette - the palette for the file
1766 (array of png_color)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1767
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1768 num_palette - number of entries in the palette
1769
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]1770 png_get_gAMA(png_ptr, info_ptr, &file_gamma);
Glenn Randers-Pehrson27742382011-01-27 09:37:34 -0600[diff] [blame^]1771 png_get_gAMA_fixed(png_ptr, info_ptr, &int_file_gamma);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1772
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]1773 file_gamma - the gamma at which the file is
1774 written (PNG_INFO_gAMA)
1775
1776 int_file_gamma - 100,000 times the gamma at which the
1777 file is written
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1778
1779 png_get_sRGB(png_ptr, info_ptr, &srgb_intent);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1780
Glenn Randers-Pehrson27742382011-01-27 09:37:34 -0600[diff] [blame^]1781 file_srgb_intent - the rendering intent (PNG_INFO_sRGB)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1782 The presence of the sRGB chunk
1783 means that the pixel data is in the
1784 sRGB color space. This chunk also
1785 implies specific values of gAMA and
1786 cHRM.
1787
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1788 png_get_iCCP(png_ptr, info_ptr, &name,
1789 &compression_type, &profile, &proflen);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1790
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]1791 name - The profile name.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1792
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]1793 compression_type - The compression type; always
1794 PNG_COMPRESSION_TYPE_BASE for PNG 1.0.
1795 You may give NULL to this argument to
1796 ignore it.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1797
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]1798 profile - International Color Consortium color
1799 profile data. May contain NULs.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1800
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]1801 proflen - length of profile data in bytes.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1802
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1803 png_get_sBIT(png_ptr, info_ptr, &sig_bit);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1804
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1805 sig_bit - the number of significant bits for
1806 (PNG_INFO_sBIT) each of the gray,
1807 red, green, and blue channels,
1808 whichever are appropriate for the
1809 given color type (png_color_16)
1810
Glenn Randers-Pehrson866b62a2009-08-08 16:33:14 -0500[diff] [blame]1811 png_get_tRNS(png_ptr, info_ptr, &trans_alpha,
1812 &num_trans, &trans_color);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1813
Glenn Randers-Pehrson866b62a2009-08-08 16:33:14 -0500[diff] [blame]1814 trans_alpha - array of alpha (transparency)
1815 entries for palette (PNG_INFO_tRNS)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1816
Glenn Randers-Pehrsonf3c51e42011-01-15 10:25:25 -0600[diff] [blame]1817 num_trans - number of transparent entries
1818 (PNG_INFO_tRNS)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1819
Glenn Randers-Pehrson56f63962008-10-06 10:16:17 -0500[diff] [blame]1820 trans_color - graylevel or color sample values of
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]1821 the single transparent color for
1822 non-paletted images (PNG_INFO_tRNS)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1823
1824 png_get_hIST(png_ptr, info_ptr, &hist);
1825 (PNG_INFO_hIST)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1826
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1827 hist - histogram of palette (array of
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1828 png_uint_16)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1829
1830 png_get_tIME(png_ptr, info_ptr, &mod_time);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1831
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1832 mod_time - time image was last modified
1833 (PNG_VALID_tIME)
1834
1835 png_get_bKGD(png_ptr, info_ptr, &background);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1836
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1837 background - background color (PNG_VALID_bKGD)
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1838 valid 16-bit red, green and blue
1839 values, regardless of color_type
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1840
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]1841 num_comments = png_get_text(png_ptr, info_ptr,
1842 &text_ptr, &num_text);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1843
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]1844 num_comments - number of comments
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1845
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1846 text_ptr - array of png_text holding image
1847 comments
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1848
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1849 text_ptr[i].compression - type of compression used
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1850 on "text" PNG_TEXT_COMPRESSION_NONE
1851 PNG_TEXT_COMPRESSION_zTXt
1852 PNG_ITXT_COMPRESSION_NONE
1853 PNG_ITXT_COMPRESSION_zTXt
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1854
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1855 text_ptr[i].key - keyword for comment. Must contain
1856 1-79 characters.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1857
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1858 text_ptr[i].text - text comments for current
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]1859 keyword. Can be empty.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1860
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1861 text_ptr[i].text_length - length of text string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1862 after decompression, 0 for iTXt
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1863
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1864 text_ptr[i].itxt_length - length of itxt string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1865 after decompression, 0 for tEXt/zTXt
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1866
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1867 text_ptr[i].lang - language of comment (empty
1868 string for unknown).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1869
Glenn Randers-Pehrson73d57cb2002-03-25 18:49:08 -0600[diff] [blame]1870 text_ptr[i].lang_key - keyword in UTF-8
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1871 (empty string for unknown).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1872
Glenn Randers-Pehrson8f5846f2009-10-31 21:31:08 -0500[diff] [blame]1873 Note that the itxt_length, lang, and lang_key
1874 members of the text_ptr structure only exist
1875 when the library is built with iTXt chunk support.
1876
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1877 num_text - number of comments (same as
1878 num_comments; you can put NULL here
1879 to avoid the duplication)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1880
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1881 Note while png_set_text() will accept text, language,
1882 and translated keywords that can be NULL pointers, the
1883 structure returned by png_get_text will always contain
1884 regular zero-terminated C strings. They might be
1885 empty strings but they will never be NULL pointers.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1886
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1887 num_spalettes = png_get_sPLT(png_ptr, info_ptr,
1888 &palette_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1889
1890 num_spalettes - number of sPLT chunks read.
1891
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1892 palette_ptr - array of palette structures holding
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1893 contents of one or more sPLT chunks
1894 read.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1895
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1896 png_get_oFFs(png_ptr, info_ptr, &offset_x, &offset_y,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1897 &unit_type);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1898
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1899 offset_x - positive offset from the left edge
1900 of the screen
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1901
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1902 offset_y - positive offset from the top edge
1903 of the screen
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1904
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1905 unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
1906
1907 png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1908 &unit_type);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1909
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1910 res_x - pixels/unit physical resolution in
1911 x direction
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1912
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1913 res_y - pixels/unit physical resolution in
1914 x direction
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1915
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1916 unit_type - PNG_RESOLUTION_UNKNOWN,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1917 PNG_RESOLUTION_METER
1918
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1919 png_get_sCAL(png_ptr, info_ptr, &unit, &width,
1920 &height)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1921
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1922 unit - physical scale units (an integer)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1923
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1924 width - width of a pixel in physical scale units
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1925
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1926 height - height of a pixel in physical scale units
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1927 (width and height are doubles)
1928
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1929 png_get_sCAL_s(png_ptr, info_ptr, &unit, &width,
1930 &height)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1931
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1932 unit - physical scale units (an integer)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1933
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1934 width - width of a pixel in physical scale units
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1935
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1936 height - height of a pixel in physical scale units
1937 (width and height are strings like "2.54")
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1938
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1939 num_unknown_chunks = png_get_unknown_chunks(png_ptr,
1940 info_ptr, &unknowns)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1941
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1942 unknowns - array of png_unknown_chunk
1943 structures holding unknown chunks
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1944
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1945 unknowns[i].name - name of unknown chunk
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1946
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1947 unknowns[i].data - data of unknown chunk
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1948
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1949 unknowns[i].size - size of unknown chunk's data
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1950
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1951 unknowns[i].location - position of chunk in file
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1952
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1953 The value of "i" corresponds to the order in which the
1954 chunks were read from the PNG file or inserted with the
1955 png_set_unknown_chunks() function.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1956
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1957The data from the pHYs chunk can be retrieved in several convenient
1958forms:
1959
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1960 res_x = png_get_x_pixels_per_meter(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1961 info_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1962
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1963 res_y = png_get_y_pixels_per_meter(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1964 info_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1965
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1966 res_x_and_y = png_get_pixels_per_meter(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1967 info_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1968
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1969 res_x = png_get_x_pixels_per_inch(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1970 info_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1971
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1972 res_y = png_get_y_pixels_per_inch(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1973 info_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1974
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1975 res_x_and_y = png_get_pixels_per_inch(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1976 info_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1977
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1978 aspect_ratio = png_get_pixel_aspect_ratio(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1979 info_ptr)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1980
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1981 Each of these returns 0 [signifying "unknown"] if
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1982 the data is not present or if res_x is 0;
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1983 res_x_and_y is 0 if res_x != res_y
1984
1985 Note that because of the way the resolutions are
1986 stored internally, the inch conversions won't
1987 come out to exactly even number. For example,
1988 72 dpi is stored as 0.28346 pixels/meter, and
1989 when this is retrieved it is 71.9988 dpi, so
1990 be sure to round the returned value appropriately
1991 if you want to display a reasonable-looking result.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1992
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1993The data from the oFFs chunk can be retrieved in several convenient
1994forms:
1995
1996 x_offset = png_get_x_offset_microns(png_ptr, info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1997
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1998 y_offset = png_get_y_offset_microns(png_ptr, info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1999
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2000 x_offset = png_get_x_offset_inches(png_ptr, info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2001
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2002 y_offset = png_get_y_offset_inches(png_ptr, info_ptr);
2003
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2004 Each of these returns 0 [signifying "unknown" if both
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2005 x and y are 0] if the data is not present or if the
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2006 chunk is present but the unit is the pixel. The
2007 remark about inexact inch conversions applies here
2008 as well, because a value in inches can't always be
2009 converted to microns and back without some loss
2010 of precision.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2011
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2012For more information, see the png_info definition in png.h and the
2013PNG specification for chunk contents. Be careful with trusting
2014rowbytes, as some of the transformations could increase the space
2015needed to hold a row (expand, filler, gray_to_rgb, etc.).
2016See png_read_update_info(), below.
2017
2018A quick word about text_ptr and num_text. PNG stores comments in
2019keyword/text pairs, one pair per chunk, with no limit on the number
2020of text chunks, and a 2^31 byte limit on their size. While there are
2021suggested keywords, there is no requirement to restrict the use to these
2022strings. It is strongly suggested that keywords and text be sensible
2023to humans (that's the point), so don't use abbreviations. Non-printing
2024symbols are not allowed. See the PNG specification for more details.
2025There is also no requirement to have text after the keyword.
2026
2027Keywords should be limited to 79 Latin-1 characters without leading or
2028trailing spaces, but non-consecutive spaces are allowed within the
2029keyword. It is possible to have the same keyword any number of times.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2030The text_ptr is an array of png_text structures, each holding a
2031pointer to a language string, a pointer to a keyword and a pointer to
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2032a text string. The text string, language code, and translated
2033keyword may be empty or NULL pointers. The keyword/text
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2034pairs are put into the array in the order that they are received.
2035However, some or all of the text chunks may be after the image, so, to
2036make sure you have read all the text chunks, don't mess with these
2037until after you read the stuff after the image. This will be
2038mentioned again below in the discussion that goes with png_read_end().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2039
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2040.SS Input transformations
2041
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2042After you've read the header information, you can set up the library
2043to handle any special transformations of the image data. The various
2044ways to transform the data will be described in the order that they
2045should occur. This is important, as some of these change the color
2046type and/or bit depth of the data, and some others only work on
2047certain color types and bit depths. Even though each transformation
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2048checks to see if it has data that it can do something with, you should
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2049make sure to only enable a transformation if it will be valid for the
2050data. For example, don't swap red and blue on grayscale data.
2051
2052The colors used for the background and transparency values should be
2053supplied in the same format/depth as the current image data. They
2054are stored in the same format/depth as the image data in a bKGD or tRNS
2055chunk, so this is what libpng expects for this data. The colors are
2056transformed to keep in sync with the image data when an application
2057calls the png_read_update_info() routine (see below).
2058
2059Data will be decoded into the supplied row buffers packed into bytes
2060unless the library has been told to transform it into another format.
2061For example, 4 bit/pixel paletted or grayscale data will be returned
20622 pixels/byte with the leftmost pixel in the high-order bits of the
2063byte, unless png_set_packing() is called. 8-bit RGB data will be stored
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]2064in RGB RGB RGB format unless png_set_filler() or png_set_add_alpha()
2065is called to insert filler bytes, either before or after each RGB triplet.
206616-bit RGB data will be returned RRGGBB RRGGBB, with the most significant
2067byte of the color value first, unless png_set_strip_16() is called to
Glenn Randers-Pehrson16e11662004-11-01 14:13:40 -0600[diff] [blame]2068transform it to regular RGB RGB triplets, or png_set_filler() or
2069png_set_add alpha() is called to insert filler bytes, either before or
2070after each RRGGBB triplet. Similarly, 8-bit or 16-bit grayscale data can
2071be modified with
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]2072png_set_filler(), png_set_add_alpha(), or png_set_strip_16().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2073
2074The following code transforms grayscale images of less than 8 to 8 bits,
2075changes paletted images to RGB, and adds a full alpha channel if there is
2076transparency information in a tRNS chunk. This is most useful on
2077grayscale images with bit depths of 2 or 4 or if there is a multiple-image
2078viewing application that wishes to treat all images in the same way.
2079
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2080 if (color_type == PNG_COLOR_TYPE_PALETTE)
2081 png_set_palette_to_rgb(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2082
2083 if (color_type == PNG_COLOR_TYPE_GRAY &&
Glenn Randers-Pehrson1ce08362006-03-08 23:35:59 -0600[diff] [blame]2084 bit_depth < 8) png_set_expand_gray_1_2_4_to_8(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2085
2086 if (png_get_valid(png_ptr, info_ptr,
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]2087 PNG_INFO_tRNS)) png_set_tRNS_to_alpha(png_ptr);
2088
2089These three functions are actually aliases for png_set_expand(), added
2090in libpng version 1.0.4, with the function names expanded to improve code
2091readability. In some future version they may actually do different
2092things.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2093
Glenn Randers-Pehrson1ce08362006-03-08 23:35:59 -0600[diff] [blame]2094As of libpng version 1.2.9, png_set_expand_gray_1_2_4_to_8() was
2095added. It expands the sample depth without changing tRNS to alpha.
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]2096
Glenn Randers-Pehrson135d17c2011-01-24 00:16:54 -0600[diff] [blame]2097As of libpng version 1.5.1beta10, not all possible expansions are supported.
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]2098
2099In the following table, the 01 means grayscale with depth<8, 31 means
2100indexed with depth<8, other numerals represent the color type, "T" means
2101the tRNS chunk is present, A means an alpha channel is present, and O
2102means tRNS or alpha is present but all pixels in the image are opaque.
2103
2104 FROM 01 31 0 0T 0O 2 2T 2O 3 3T 3O 4A 4O 6A 6O
2105 TO
2106 01 -
2107 31 -
2108 0 1 -
2109 0T -
2110 0O -
2111 2 GX -
2112 2T -
2113 2O -
2114 3 1 -
2115 3T -
2116 3O -
2117 4A T -
2118 4O -
2119 6A GX TX TX -
2120 6O GX TX -
2121
2122Within the matrix,
2123 "-" means the transformation is not supported.
2124 "X" means the transformation is obtained by png_set_expand().
2125 "1" means the transformation is obtained by
2126 png_set_expand_gray_1_2_4_to_8
2127 "G" means the transformation is obtained by
2128 png_set_gray_to_rgb().
2129 "P" means the transformation is obtained by
2130 png_set_expand_palette_to_rgb().
2131 "T" means the transformation is obtained by
2132 png_set_tRNS_to_alpha().
Glenn Randers-Pehrson1ce08362006-03-08 23:35:59 -0600[diff] [blame]2133
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2134PNG can have files with 16 bits per channel. If you only can handle
21358 bits per channel, this will strip the pixels down to 8 bit.
2136
2137 if (bit_depth == 16)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2138 png_set_strip_16(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2139
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2140If, for some reason, you don't need the alpha channel on an image,
2141and you want to remove it rather than combining it with the background
2142(but the image author certainly had in mind that you *would* combine
2143it with the background, so that's what you should probably do):
2144
2145 if (color_type & PNG_COLOR_MASK_ALPHA)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2146 png_set_strip_alpha(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2147
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2148In PNG files, the alpha channel in an image
2149is the level of opacity. If you need the alpha channel in an image to
2150be the level of transparency instead of opacity, you can invert the
2151alpha channel (or the tRNS chunk data) after it's read, so that 0 is
2152fully opaque and 255 (in 8-bit or paletted images) or 65535 (in 16-bit
2153images) is fully transparent, with
2154
2155 png_set_invert_alpha(png_ptr);
2156
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2157PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
2158they can, resulting in, for example, 8 pixels per byte for 1 bit
2159files. This code expands to 1 pixel per byte without changing the
2160values of the pixels:
2161
2162 if (bit_depth < 8)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2163 png_set_packing(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2164
2165PNG files have possible bit depths of 1, 2, 4, 8, and 16. All pixels
2166stored in a PNG image have been "scaled" or "shifted" up to the next
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]2167higher possible bit depth (e.g. from 5 bits/sample in the range [0,31]
2168to 8 bits/sample in the range [0, 255]). However, it is also possible
2169to convert the PNG pixel data back to the original bit depth of the
2170image. This call reduces the pixels back down to the original bit depth:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2171
Glenn Randers-Pehrson1ea0ff32001-08-07 22:25:59 -0500[diff] [blame]2172 png_color_8p sig_bit;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2173
2174 if (png_get_sBIT(png_ptr, info_ptr, &sig_bit))
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2175 png_set_shift(png_ptr, sig_bit);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2176
2177PNG files store 3-color pixels in red, green, blue order. This code
2178changes the storage of the pixels to blue, green, red:
2179
2180 if (color_type == PNG_COLOR_TYPE_RGB ||
2181 color_type == PNG_COLOR_TYPE_RGB_ALPHA)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2182 png_set_bgr(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2183
Glenn Randers-Pehrson1b8e5672001-08-25 06:46:06 -0500[diff] [blame]2184PNG files store RGB pixels packed into 3 or 6 bytes. This code expands them
2185into 4 or 8 bytes for windowing systems that need them in this format:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2186
Glenn Randers-Pehrson1b8e5672001-08-25 06:46:06 -0500[diff] [blame]2187 if (color_type == PNG_COLOR_TYPE_RGB)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2188 png_set_filler(png_ptr, filler, PNG_FILLER_BEFORE);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2189
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]2190where "filler" is the 8 or 16-bit number to fill with, and the location is
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2191either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether
2192you want the filler before the RGB or after. This transformation
Glenn Randers-Pehrson1b8e5672001-08-25 06:46:06 -0500[diff] [blame]2193does not affect images that already have full alpha channels. To add an
2194opaque alpha channel, use filler=0xff or 0xffff and PNG_FILLER_AFTER which
2195will generate RGBA pixels.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2196
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]2197Note that png_set_filler() does not change the color type. If you want
2198to do that, you can add a true alpha channel with
2199
2200 if (color_type == PNG_COLOR_TYPE_RGB ||
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2201 color_type == PNG_COLOR_TYPE_GRAY)
2202 png_set_add_alpha(png_ptr, filler, PNG_FILLER_AFTER);
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]2203
2204where "filler" contains the alpha value to assign to each pixel.
Glenn Randers-Pehrson16e11662004-11-01 14:13:40 -0600[diff] [blame]2205This function was added in libpng-1.2.7.
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]2206
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2207If you are reading an image with an alpha channel, and you need the
2208data as ARGB instead of the normal PNG format RGBA:
2209
2210 if (color_type == PNG_COLOR_TYPE_RGB_ALPHA)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2211 png_set_swap_alpha(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2212
2213For some uses, you may want a grayscale image to be represented as
2214RGB. This code will do that conversion:
2215
2216 if (color_type == PNG_COLOR_TYPE_GRAY ||
2217 color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2218 png_set_gray_to_rgb(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2219
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2220Conversely, you can convert an RGB or RGBA image to grayscale or grayscale
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2221with alpha.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2222
2223 if (color_type == PNG_COLOR_TYPE_RGB ||
2224 color_type == PNG_COLOR_TYPE_RGB_ALPHA)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2225 png_set_rgb_to_gray_fixed(png_ptr, error_action,
2226 int red_weight, int green_weight);
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2227
2228 error_action = 1: silently do the conversion
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2229
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2230 error_action = 2: issue a warning if the original
2231 image has any pixel where
2232 red != green or red != blue
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2233
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2234 error_action = 3: issue an error and abort the
2235 conversion if the original
2236 image has any pixel where
2237 red != green or red != blue
2238
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2239 red_weight: weight of red component times 100000
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2240
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2241 green_weight: weight of green component times 100000
2242 If either weight is negative, default
2243 weights (21268, 71514) are used.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2244
2245If you have set error_action = 1 or 2, you can
2246later check whether the image really was gray, after processing
2247the image rows, with the png_get_rgb_to_gray_status(png_ptr) function.
2248It will return a png_byte that is zero if the image was gray or
22491 if there were any non-gray pixels. bKGD and sBIT data
2250will be silently converted to grayscale, using the green channel
2251data, regardless of the error_action setting.
2252
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2253With red_weight+green_weight<=100000,
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2254the normalized graylevel is computed:
2255
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2256 int rw = red_weight * 65536;
2257 int gw = green_weight * 65536;
2258 int bw = 65536 - (rw + gw);
2259 gray = (rw*red + gw*green + bw*blue)/65536;
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2260
2261The default values approximate those recommended in the Charles
2262Poynton's Color FAQ, <http://www.inforamp.net/~poynton/>
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]2263Copyright (c) 1998-01-04 Charles Poynton <poynton at inforamp.net>
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2264
2265 Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
2266
Glenn Randers-Pehrson9962b842011-01-24 00:12:14 -0600[diff] [blame]2267Libpng approximates this with integers scaled by 32768:
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2268
Glenn Randers-Pehrson9962b842011-01-24 00:12:14 -0600[diff] [blame]2269 Y = (6968 * R + 23434 * G + 2366 * B)/32768
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2270
2271The calculation is done in a linear colorspace, if the image gamma
Glenn Randers-Pehrson9962b842011-01-24 00:12:14 -0600[diff] [blame]2272can be determined.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2273
Glenn Randers-Pehrson73d57cb2002-03-25 18:49:08 -0600[diff] [blame]2274If you have a grayscale and you are using png_set_expand_depth(),
2275png_set_expand(), or png_set_gray_to_rgb to change to truecolor or to
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]2276a higher bit-depth, you must either supply the background color as a gray
2277value at the original file bit-depth (need_expand = 1) or else supply the
2278background color as an RGB triplet at the final, expanded bit depth
2279(need_expand = 0). Similarly, if you are reading a paletted image, you
2280must either supply the background color as a palette index (need_expand = 1)
2281or as an RGB triplet that may or may not be in the palette (need_expand = 0).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2282
2283 png_color_16 my_background;
2284 png_color_16p image_background;
2285
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]2286 if (png_get_bKGD(png_ptr, info_ptr, &image_background))
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2287 png_set_background(png_ptr, image_background,
2288 PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2289 else
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2290 png_set_background(png_ptr, &my_background,
2291 PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2292
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2293The png_set_background() function tells libpng to composite images
2294with alpha or simple transparency against the supplied background
2295color. If the PNG file contains a bKGD chunk (PNG_INFO_bKGD valid),
2296you may use this color, or supply another color more suitable for
2297the current display (e.g., the background color from a web page). You
2298need to tell libpng whether the color is in the gamma space of the
2299display (PNG_BACKGROUND_GAMMA_SCREEN for colors you supply), the file
2300(PNG_BACKGROUND_GAMMA_FILE for colors from the bKGD chunk), or one
2301that is neither of these gammas (PNG_BACKGROUND_GAMMA_UNIQUE - I don't
2302know why anyone would use this, but it's here).
2303
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2304To properly display PNG images on any kind of system, the application needs
2305to know what the display gamma is. Ideally, the user will know this, and
2306the application will allow them to set it. One method of allowing the user
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]2307to set the display gamma separately for each system is to check for a
2308SCREEN_GAMMA or DISPLAY_GAMMA environment variable, which will hopefully be
2309correctly set.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2310
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]2311Note that display_gamma is the overall gamma correction required to produce
2312pleasing results, which depends on the lighting conditions in the surrounding
2313environment. In a dim or brightly lit room, no compensation other than
2314the physical gamma exponent of the monitor is needed, while in a dark room
2315a slightly smaller exponent is better.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2316
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]2317 double gamma, screen_gamma;
2318
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2319 if (/* We have a user-defined screen
2320 gamma value */)
2321 {
2322 screen_gamma = user_defined_screen_gamma;
2323 }
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2324
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2325 /* One way that applications can share the same
2326 screen gamma value */
2327 else if ((gamma_str = getenv("SCREEN_GAMMA"))
2328 != NULL)
2329 {
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]2330 screen_gamma = (double)atof(gamma_str);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2331 }
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2332
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2333 /* If we don't have another value */
2334 else
2335 {
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2336 screen_gamma = 2.2; /* A good guess for a
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2337 PC monitor in a bright office or a dim room */
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2338
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2339 screen_gamma = 2.0; /* A good guess for a
2340 PC monitor in a dark room */
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2341
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2342 screen_gamma = 1.7 or 1.0; /* A good
2343 guess for Mac systems */
2344 }
2345
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]2346The functions png_set_gamma() and its fixed point equivalent
2347png_set_gamma_fixed() handle gamma transformations of the data.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2348Pass both the file gamma and the current screen_gamma. If the file does
2349not have a gamma value, you can pass one anyway if you have an idea what
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2350it is (usually 0.45455 is a good guess for GIF images on PCs). Note
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2351that file gammas are inverted from screen gammas. See the discussions
2352on gamma in the PNG specification for an excellent description of what
2353gamma is, and why all applications should support it. It is strongly
2354recommended that PNG viewers support gamma correction.
2355
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]2356 if (png_get_gAMA(png_ptr, info_ptr, &file_gamma))
2357 png_set_gamma(png_ptr, screen_gamma, file_gamma);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2358
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2359 else
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2360 png_set_gamma(png_ptr, screen_gamma, 0.45455);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2361
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]2362If you need to reduce an RGB file to a paletted file, or if a paletted
2363file has more entries then will fit on your screen, png_set_quantize()
Glenn Randers-Pehrson862cb202010-04-16 22:12:51 -0500[diff] [blame]2364will do that. Note that this is a simple match quantization that merely
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]2365finds the closest color available. This should work fairly well with
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2366optimized palettes, but fairly badly with linear color cubes. If you
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]2367pass a palette that is larger then maximum_colors, the file will
2368reduce the number of colors in the palette so it will fit into
2369maximum_colors. If there is a histogram, it will use it to make
2370more intelligent choices when reducing the palette. If there is no
2371histogram, it may not do as good a job.
2372
2373 if (color_type & PNG_COLOR_MASK_COLOR)
2374 {
2375 if (png_get_valid(png_ptr, info_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2376 PNG_INFO_PLTE))
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]2377 {
2378 png_uint_16p histogram = NULL;
2379
2380 png_get_hIST(png_ptr, info_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2381 &histogram);
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]2382 png_set_quantize(png_ptr, palette, num_palette,
2383 max_screen_colors, histogram, 1);
2384 }
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2385
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]2386 else
2387 {
2388 png_color std_color_cube[MAX_SCREEN_COLORS] =
2389 { ... colors ... };
2390
2391 png_set_quantize(png_ptr, std_color_cube,
2392 MAX_SCREEN_COLORS, MAX_SCREEN_COLORS,
2393 NULL,0);
2394 }
2395 }
2396
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2397PNG files describe monochrome as black being zero and white being one.
2398The following code will reverse this (make black be one and white be
2399zero):
2400
Glenn Randers-Pehrson1ea0ff32001-08-07 22:25:59 -0500[diff] [blame]2401 if (bit_depth == 1 && color_type == PNG_COLOR_TYPE_GRAY)
2402 png_set_invert_mono(png_ptr);
2403
2404This function can also be used to invert grayscale and gray-alpha images:
2405
2406 if (color_type == PNG_COLOR_TYPE_GRAY ||
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2407 color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2408 png_set_invert_mono(png_ptr);
2409
2410PNG files store 16 bit pixels in network byte order (big-endian,
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2411ie. most significant bits first). This code changes the storage to the
2412other way (little-endian, i.e. least significant bits first, the
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2413way PCs store them):
2414
2415 if (bit_depth == 16)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2416 png_set_swap(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2417
2418If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you
2419need to change the order the pixels are packed into bytes, you can use:
2420
2421 if (bit_depth < 8)
2422 png_set_packswap(png_ptr);
2423
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2424Finally, you can write your own transformation function if none of
2425the existing ones meets your needs. This is done by setting a callback
2426with
2427
2428 png_set_read_user_transform_fn(png_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2429 read_transform_fn);
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2430
2431You must supply the function
2432
Glenn Randers-Pehrson81ce8892011-01-24 08:04:37 -0600[diff] [blame]2433 void read_transform_fn(png_structp png_ptr, row_info_ptr
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2434 row_info, png_bytep data)
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2435
2436See pngtest.c for a working example. Your function will be called
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]2437after all of the other transformations have been processed. Take care with
2438interlaced images if you do the interlace yourself - the width of the row is the
2439width in 'row_info', not the overall image width.
2440
2441If supported libpng provides two information routines that you can use to find
2442where you are in processing the image:
2443
2444 png_get_current_pass_number(png_structp png_ptr);
2445 png_get_current_row_number(png_structp png_ptr);
2446
2447Don't try using these outside a transform callback - firstly they are only
2448supported if user transforms are supported, secondly they may well return
2449unexpected results unless the row is actually being processed at the moment they
2450are called.
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2451
2452You can also set up a pointer to a user structure for use by your
2453callback function, and you can inform libpng that your transform
2454function will change the number of channels or bit depth with the
2455function
2456
2457 png_set_user_transform_info(png_ptr, user_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2458 user_depth, user_channels);
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2459
2460The user's application, not libpng, is responsible for allocating and
2461freeing any memory required for the user structure.
2462
2463You can retrieve the pointer via the function
2464png_get_user_transform_ptr(). For example:
2465
2466 voidp read_user_transform_ptr =
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2467 png_get_user_transform_ptr(png_ptr);
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2468
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2469The last thing to handle is interlacing; this is covered in detail below,
2470but you must call the function here if you want libpng to handle expansion
2471of the interlaced image.
2472
2473 number_of_passes = png_set_interlace_handling(png_ptr);
2474
2475After setting the transformations, libpng can update your png_info
2476structure to reflect any transformations you've requested with this
2477call. This is most useful to update the info structure's rowbytes
2478field so you can use it to allocate your image memory. This function
2479will also update your palette with the correct screen_gamma and
2480background if these have been given with the calls above.
2481
2482 png_read_update_info(png_ptr, info_ptr);
2483
2484After you call png_read_update_info(), you can allocate any
2485memory you need to hold the image. The row data is simply
2486raw byte data for all forms of images. As the actual allocation
2487varies among applications, no example will be given. If you
2488are allocating one large chunk, you will need to build an
2489array of pointers to each row, as it will be needed for some
2490of the functions below.
2491
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2492Remember: Before you call png_read_update_info(), the png_get_
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]2493functions return the values corresponding to the original PNG image.
2494After you call png_read_update_info the values refer to the image
2495that libpng will output. Consequently you must call all the png_set_
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2496functions before you call png_read_update_info(). This is particularly
2497important for png_set_interlace_handling() - if you are going to call
2498png_read_update_info() you must call png_set_interlace_handling() before
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]2499it unless you want to receive interlaced output.
2500
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2501.SS Reading image data
2502
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2503After you've allocated memory, you can read the image data.
2504The simplest way to do this is in one function call. If you are
2505allocating enough memory to hold the whole image, you can just
2506call png_read_image() and libpng will read in all the image data
2507and put it in the memory area supplied. You will need to pass in
2508an array of pointers to each row.
2509
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]2510This function automatically handles interlacing, so you don't
2511need to call png_set_interlace_handling() (unless you call
2512png_read_update_info()) or call this function multiple times, or any
2513of that other stuff necessary with png_read_rows().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2514
2515 png_read_image(png_ptr, row_pointers);
2516
2517where row_pointers is:
2518
2519 png_bytep row_pointers[height];
2520
2521You can point to void or char or whatever you use for pixels.
2522
2523If you don't want to read in the whole image at once, you can
2524use png_read_rows() instead. If there is no interlacing (check
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2525interlace_type == PNG_INTERLACE_NONE), this is simple:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2526
2527 png_read_rows(png_ptr, row_pointers, NULL,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2528 number_of_rows);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2529
2530where row_pointers is the same as in the png_read_image() call.
2531
2532If you are doing this just one row at a time, you can do this with
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2533a single row_pointer instead of an array of row_pointers:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2534
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2535 png_bytep row_pointer = row;
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2536 png_read_row(png_ptr, row_pointer, NULL);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2537
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2538If the file is interlaced (interlace_type != 0 in the IHDR chunk), things
2539get somewhat harder. The only current (PNG Specification version 1.2)
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2540interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7);
2541a somewhat complicated 2D interlace scheme, known as Adam7, that
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2542breaks down an image into seven smaller images of varying size, based
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2543on an 8x8 grid. This number is defined (from libpng 1.5) as
2544PNG_INTERLACE_ADAM7_PASSES in png.h
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2545
2546libpng can fill out those images or it can give them to you "as is".
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2547It is almost always better to have libpng handle the interlacing for you.
2548If you want the images filled out, there are two ways to do that. The one
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2549mentioned in the PNG specification is to expand each pixel to cover
2550those pixels that have not been read yet (the "rectangle" method).
2551This results in a blocky image for the first pass, which gradually
2552smooths out as more pixels are read. The other method is the "sparkle"
2553method, where pixels are drawn only in their final locations, with the
2554rest of the image remaining whatever colors they were initialized to
2555before the start of the read. The first method usually looks better,
2556but tends to be slower, as there are more pixels to put in the rows.
2557
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2558If, as is likely, you want libpng to expand the images, call this before
2559calling png_start_read_image() or png_read_update_info():
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2560
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2561 if (interlace_type == PNG_INTERLACE_ADAM7)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2562 number_of_passes
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2563 = png_set_interlace_handling(png_ptr);
2564
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2565This will return the number of passes needed. Currently, this is seven,
2566but may change if another interlace type is added. This function can be
2567called even if the file is not interlaced, where it will return one pass.
2568You then need to read the whole image 'number_of_passes' times. Each time
2569will distribute the pixels from the current pass to the correct place in
2570the output image, so you need to supply the same rows to png_read_rows in
2571each pass.
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]2572
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2573If you are not going to display the image after each pass, but are
2574going to wait until the entire image is read in, use the sparkle
2575effect. This effect is faster and the end result of either method
2576is exactly the same. If you are planning on displaying the image
2577after each pass, the "rectangle" effect is generally considered the
2578better looking one.
2579
2580If you only want the "sparkle" effect, just call png_read_rows() as
2581normal, with the third parameter NULL. Make sure you make pass over
2582the image number_of_passes times, and you don't change the data in the
2583rows between calls. You can change the locations of the data, just
2584not the data. Each pass only writes the pixels appropriate for that
2585pass, and assumes the data from previous passes is still valid.
2586
2587 png_read_rows(png_ptr, row_pointers, NULL,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2588 number_of_rows);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2589
2590If you only want the first effect (the rectangles), do the same as
2591before except pass the row buffer in the third parameter, and leave
2592the second parameter NULL.
2593
2594 png_read_rows(png_ptr, NULL, row_pointers,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2595 number_of_rows);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2596
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2597If you don't want libpng to handle the interlacing details, just call
2598png_read_rows() PNG_INTERLACE_ADAM7_PASSES times to read in all the images.
2599Each of the images is a valid image by itself, however you will almost
2600certainly need to distribute the pixels from each sub-image to the
2601correct place. This is where everything gets very tricky.
2602
2603If you want to retrieve the separate images you must pass the correct
2604number of rows to each successive call of png_read_rows(). The calculation
2605gets pretty complicated for small images, where some sub-images may
2606not even exist because either their width or height ends up zero.
2607libpng provides two macros to help you in 1.5 and later versions:
2608
2609 png_uint_32 width = PNG_PASS_COLS(image_width, pass_number);
2610 png_uint_32 height = PNG_PASS_ROWS(image_height, pass_number);
2611
2612Respectively these tell you the width and height of the sub-image
2613corresponding to the numbered pass. 'pass' is in in the range 0 to 6 -
2614this can be confusing because the specification refers to the same passes
2615as 1 to 7! Be careful, you must check both the width and height before
2616calling png_read_rows() and not call it for that pass if either is zero.
2617
2618You can, of course, read each sub-image row by row. If you want to
2619produce optimal code to make a pixel-by-pixel transformation of an
2620interlaced image this is the best approach; read each row of each pass,
2621transform it, and write it out to a new interlaced image.
2622
2623If you want to de-interlace the image yourself libpng provides further
2624macros to help that tell you where to place the pixels in the output image.
2625Because the interlacing scheme is rectangular - sub-image pixels are always
2626arranged on a rectangular grid - all you need to know for each pass is the
2627starting column and row in the output image of the first pixel plus the
2628spacing between each pixel. As of libpng 1.5 there are four macros to
2629retrieve this information:
2630
2631 png_uint_32 x = PNG_PASS_START_COL(pass);
2632 png_uint_32 y = PNG_PASS_START_ROW(pass);
2633 png_uint_32 xStep = 1U << PNG_PASS_COL_SHIFT(pass);
2634 png_uint_32 yStep = 1U << PNG_PASS_ROW_SHIFT(pass);
2635
2636These allow you to write the obvious loop:
2637
2638 png_uint_32 input_y = 0;
2639 png_uint_32 output_y = PNG_PASS_START_ROW(pass);
2640
2641 while (output_y < output_image_height)
2642 {
2643 png_uint_32 input_x = 0;
2644 png_uint_32 output_x = PNG_PASS_START_COL(pass);
2645
2646 while (output_x < output_image_width)
2647 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2648 image[output_y][output_x] =
2649 subimage[pass][input_y][input_x++];
2650
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2651 output_x += xStep;
2652 }
2653
2654 ++input_y;
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2655 output_y += yStep;
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2656 }
2657
2658Notice that the steps between successive output rows and columns are
2659returned as shifts. This is possible because the pixels in the subimages
2660are always a power of 2 apart - 1, 2, 4 or 8 pixels - in the original
2661image. In practice you may need to directly calculate the output coordinate
2662given an input coordinate. libpng provides two further macros for this
2663purpose:
2664
2665 png_uint_32 output_x = PNG_COL_FROM_PASS_COL(input_x, pass);
2666 png_uint_32 output_y = PNG_ROW_FROM_PASS_ROW(input_y, pass);
2667
2668Finally a pair of macros are provided to tell you if a particular image
2669row or column appears in a given pass:
2670
2671 int col_in_pass = PNG_COL_IN_INTERLACE_PASS(output_x, pass);
2672 int row_in_pass = PNG_ROW_IN_INTERLACE_PASS(output_y, pass);
2673
2674Bear in mind that you will probably also need to check the width and height
2675of the pass in addition to the above to be sure the pass even exists!
2676
2677With any luck you are convinced by now that you don't want to do your own
2678interlace handling. In reality normally the only good reason for doing this
2679is if you are processing PNG files on a pixel-by-pixel basis and don't want
2680to load the whole file into memory when it is interlaced.
2681
2682libpng includes a test program, pngvalid, that illustrates reading and
2683writing of interlaced images. If you can't get interlacing to work in your
2684code and don't want to leave it to libpng (the recommended approach) see
2685how pngvalid.c does it.
2686
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2687.SS Finishing a sequential read
2688
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]2689After you are finished reading the image through the
2690low-level interface, you can finish reading the file. If you are
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2691interested in comments or time, which may be stored either before or
2692after the image data, you should pass the separate png_info struct if
2693you want to keep the comments from before and after the image
2694separate. If you are not interested, you can pass NULL.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2695
2696 png_read_end(png_ptr, end_info);
2697
2698When you are done, you can free all memory allocated by libpng like this:
2699
2700 png_destroy_read_struct(&png_ptr, &info_ptr,
2701 &end_info);
2702
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2703It is also possible to individually free the info_ptr members that
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2704point to libpng-allocated storage with the following function:
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2705
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2706 png_free_data(png_ptr, info_ptr, mask, seq)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2707
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2708 mask - identifies data to be freed, a mask
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]2709 containing the bitwise OR of one or
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2710 more of
2711 PNG_FREE_PLTE, PNG_FREE_TRNS,
2712 PNG_FREE_HIST, PNG_FREE_ICCP,
2713 PNG_FREE_PCAL, PNG_FREE_ROWS,
2714 PNG_FREE_SCAL, PNG_FREE_SPLT,
2715 PNG_FREE_TEXT, PNG_FREE_UNKN,
2716 or simply PNG_FREE_ALL
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2717
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2718 seq - sequence number of item to be freed
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2719 (-1 for all items)
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2720
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2721This function may be safely called when the relevant storage has
Glenn Randers-Pehrson68ea2432000-04-01 21:10:05 -0600[diff] [blame]2722already been freed, or has not yet been allocated, or was allocated
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]2723by the user and not by libpng, and will in those cases do nothing.
2724The "seq" parameter is ignored if only one item of the selected data
2725type, such as PLTE, is allowed. If "seq" is not -1, and multiple items
2726are allowed for the data type identified in the mask, such as text or
2727sPLT, only the n'th item in the structure is freed, where n is "seq".
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2728
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2729The default behavior is only to free data that was allocated internally
2730by libpng. This can be changed, so that libpng will not free the data,
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2731or so that it will free data that was allocated by the user with png_malloc()
2732or png_zalloc() and passed in via a png_set_*() function, with
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2733
2734 png_data_freer(png_ptr, info_ptr, freer, mask)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2735
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2736 freer - one of
2737 PNG_DESTROY_WILL_FREE_DATA
2738 PNG_SET_WILL_FREE_DATA
2739 PNG_USER_WILL_FREE_DATA
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2740
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2741 mask - which data elements are affected
2742 same choices as in png_free_data()
2743
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2744This function only affects data that has already been allocated.
2745You can call this function after reading the PNG data but before calling
2746any png_set_*() functions, to control whether the user or the png_set_*()
2747function is responsible for freeing any existing data that might be present,
2748and again after the png_set_*() functions to control whether the user
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2749or png_destroy_*() is supposed to free the data. When the user assumes
2750responsibility for libpng-allocated data, the application must use
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2751png_free() to free it, and when the user transfers responsibility to libpng
2752for data that the user has allocated, the user must have used png_malloc()
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame]2753or png_zalloc() to allocate it.
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2754
2755If you allocated your row_pointers in a single block, as suggested above in
2756the description of the high level read interface, you must not transfer
2757responsibility for freeing it to the png_set_rows or png_read_destroy function,
2758because they would also try to free the individual row_pointers[i].
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2759
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2760If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword
2761separately, do not transfer responsibility for freeing text_ptr to libpng,
2762because when libpng fills a png_text structure it combines these members with
2763the key member, and png_free_data() will free only text_ptr.key. Similarly,
2764if you transfer responsibility for free'ing text_ptr from libpng to your
2765application, your application must not separately free those members.
2766
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2767The png_free_data() function will turn off the "valid" flag for anything
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]2768it frees. If you need to turn the flag off for a chunk that was freed by
2769your application instead of by libpng, you can use
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2770
2771 png_set_invalid(png_ptr, info_ptr, mask);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2772
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2773 mask - identifies the chunks to be made invalid,
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]2774 containing the bitwise OR of one or
Glenn Randers-Pehrsond56aca72000-11-23 11:51:42 -0600[diff] [blame]2775 more of
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2776 PNG_INFO_gAMA, PNG_INFO_sBIT,
2777 PNG_INFO_cHRM, PNG_INFO_PLTE,
2778 PNG_INFO_tRNS, PNG_INFO_bKGD,
2779 PNG_INFO_hIST, PNG_INFO_pHYs,
2780 PNG_INFO_oFFs, PNG_INFO_tIME,
2781 PNG_INFO_pCAL, PNG_INFO_sRGB,
2782 PNG_INFO_iCCP, PNG_INFO_sPLT,
2783 PNG_INFO_sCAL, PNG_INFO_IDAT
2784
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2785For a more compact example of reading a PNG image, see the file example.c.
2786
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2787.SS Reading PNG files progressively
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2788
2789The progressive reader is slightly different then the non-progressive
2790reader. Instead of calling png_read_info(), png_read_rows(), and
2791png_read_end(), you make one call to png_process_data(), which calls
2792callbacks when it has the info, a row, or the end of the image. You
2793set up these callbacks with png_set_progressive_read_fn(). You don't
2794have to worry about the input/output functions of libpng, as you are
2795giving the library the data directly in png_process_data(). I will
2796assume that you have read the section on reading PNG files above,
2797so I will only highlight the differences (although I will show
2798all of the code).
2799
2800png_structp png_ptr;
2801png_infop info_ptr;
2802
2803 /* An example code fragment of how you would
2804 initialize the progressive reader in your
2805 application. */
2806 int
2807 initialize_png_reader()
2808 {
2809 png_ptr = png_create_read_struct
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]2810 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2811 user_error_fn, user_warning_fn);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2812
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2813 if (!png_ptr)
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2814 return (ERROR);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2815
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2816 info_ptr = png_create_info_struct(png_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2817
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2818 if (!info_ptr)
2819 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2820 png_destroy_read_struct(&png_ptr,
2821 (png_infopp)NULL, (png_infopp)NULL);
2822 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2823 }
2824
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2825 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2826 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2827 png_destroy_read_struct(&png_ptr, &info_ptr,
2828 (png_infopp)NULL);
2829 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2830 }
2831
2832 /* This one's new. You can provide functions
2833 to be called when the header info is valid,
2834 when each row is completed, and when the image
2835 is finished. If you aren't using all functions,
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2836 you can specify NULL parameters. Even when all
2837 three functions are NULL, you need to call
2838 png_set_progressive_read_fn(). You can use
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2839 any struct as the user_ptr (cast to a void pointer
2840 for the function call), and retrieve the pointer
2841 from inside the callbacks using the function
2842
2843 png_get_progressive_ptr(png_ptr);
2844
2845 which will return a void pointer, which you have
2846 to cast appropriately.
2847 */
2848 png_set_progressive_read_fn(png_ptr, (void *)user_ptr,
2849 info_callback, row_callback, end_callback);
2850
2851 return 0;
2852 }
2853
2854 /* A code fragment that you call as you receive blocks
2855 of data */
2856 int
2857 process_data(png_bytep buffer, png_uint_32 length)
2858 {
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2859 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2860 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2861 png_destroy_read_struct(&png_ptr, &info_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2862 (png_infopp)NULL);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2863 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2864 }
2865
2866 /* This one's new also. Simply give it a chunk
2867 of data from the file stream (in order, of
2868 course). On machines with segmented memory
2869 models machines, don't give it any more than
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2870 64K. The library seems to run fine with sizes
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2871 of 4K. Although you can give it much less if
2872 necessary (I assume you can give it chunks of
2873 1 byte, I haven't tried less then 256 bytes
2874 yet). When this function returns, you may
2875 want to display any rows that were generated
2876 in the row callback if you don't already do
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2877 so there.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2878 */
2879 png_process_data(png_ptr, info_ptr, buffer, length);
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]2880
2881 /* At this point you can call png_process_data_skip if
2882 you want to handle data the library will skip yourself;
2883 it simply returns the number of bytes to skip (and stops
2884 libpng skipping that number of bytes on the next
2885 png_process_data call).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2886 return 0;
2887 }
2888
2889 /* This function is called (as set by
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2890 png_set_progressive_read_fn() above) when enough data
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2891 has been supplied so all of the header has been
2892 read.
2893 */
2894 void
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2895 info_callback(png_structp png_ptr, png_infop info)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2896 {
2897 /* Do any setup here, including setting any of
2898 the transformations mentioned in the Reading
2899 PNG files section. For now, you _must_ call
2900 either png_start_read_image() or
2901 png_read_update_info() after all the
2902 transformations are set (even if you don't set
2903 any). You may start getting rows before
2904 png_process_data() returns, so this is your
2905 last chance to prepare for that.
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2906
2907 This is where you turn on interlace handling,
2908 assuming you don't want to do it yourself.
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]2909
2910 If you need to you can stop the processing of
2911 your original input data at this point by calling
2912 png_process_data_pause. This returns the number
2913 of unprocessed bytes from the last png_process_data
2914 call - it is up to you to ensure that the next call
2915 sees these bytes again. If you don't want to bother
2916 with this you can get libpng to cache the unread
2917 bytes by setting the 'save' parameter (see png.h) but
2918 then libpng will have to copy the data internally.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2919 */
2920 }
2921
2922 /* This function is called when each row of image
2923 data is complete */
2924 void
2925 row_callback(png_structp png_ptr, png_bytep new_row,
Glenn Randers-Pehrsone68f5a32001-05-14 09:20:53 -0500[diff] [blame]2926 png_uint_32 row_num, int pass)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2927 {
2928 /* If the image is interlaced, and you turned
2929 on the interlace handler, this function will
2930 be called for every row in every pass. Some
2931 of these rows will not be changed from the
2932 previous pass. When the row is not changed,
2933 the new_row variable will be NULL. The rows
2934 and passes are called in order, so you don't
2935 really need the row_num and pass, but I'm
2936 supplying them because it may make your life
2937 easier.
2938
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2939 If you did not turn on interlace handling then
2940 the callback is called for each row of each
2941 sub-image when the image is interlaced. In this
2942 case 'row_num' is the row in the sub-image, not
2943 the row in the output image as it is in all other
2944 cases.
2945
2946 For the non-NULL rows of interlaced images when
2947 you have switched on libpng interlace handling,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2948 you must call png_progressive_combine_row()
2949 passing in the row and the old row. You can
2950 call this function for NULL rows (it will just
2951 return) and for non-interlaced images (it just
2952 does the memcpy for you) if it will make the
2953 code easier. Thus, you can just do this for
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2954 all cases if you switch on interlace handling;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2955 */
2956
2957 png_progressive_combine_row(png_ptr, old_row,
2958 new_row);
2959
2960 /* where old_row is what was displayed for
Glenn Randers-Pehrson345bc271998-06-14 14:43:31 -0500[diff] [blame]2961 previously for the row. Note that the first
2962 pass (pass == 0, really) will completely cover
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2963 the old row, so the rows do not have to be
2964 initialized. After the first pass (and only
2965 for interlaced images), you will have to pass
2966 the current row, and the function will combine
2967 the old row and the new row.
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]2968
2969 You can also call png_process_data_pause in this
2970 callback - see above.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2971 */
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2972 }
2973
2974 void
2975 end_callback(png_structp png_ptr, png_infop info)
2976 {
2977 /* This function is called after the whole image
2978 has been read, including any chunks after the
2979 image (up to and including the IEND). You
2980 will usually have the same info chunk as you
2981 had in the header, although some data may have
2982 been added to the comments and time fields.
2983
2984 Most people won't do much here, perhaps setting
2985 a flag that marks the image as finished.
2986 */
2987 }
2988
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]2989
2990
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2991.SH IV. Writing
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2992
2993Much of this is very similar to reading. However, everything of
2994importance is repeated here, so you won't have to constantly look
2995back up in the reading section to understand writing.
2996
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2997.SS Setup
2998
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2999You will want to do the I/O initialization before you get into libpng,
3000so if it doesn't work, you don't have anything to undo. If you are not
3001using the standard I/O functions, you will need to replace them with
3002custom writing functions. See the discussion under Customizing libpng.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3003
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3004 FILE *fp = fopen(file_name, "wb");
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3005
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3006 if (!fp)
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]3007 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3008
3009Next, png_struct and png_info need to be allocated and initialized.
3010As these can be both relatively large, you may not want to store these
3011on the stack, unless you have stack space to spare. Of course, you
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3012will want to check if they return NULL. If you are also reading,
3013you won't want to name your read structure and your write structure
3014both "png_ptr"; you can call them anything you like, such as
3015"read_ptr" and "write_ptr". Look at pngtest.c, for example.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3016
3017 png_structp png_ptr = png_create_write_struct
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]3018 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3019 user_error_fn, user_warning_fn);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3020
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3021 if (!png_ptr)
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]3022 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3023
3024 png_infop info_ptr = png_create_info_struct(png_ptr);
3025 if (!info_ptr)
3026 {
3027 png_destroy_write_struct(&png_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3028 (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]3029 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3030 }
3031
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]3032If you want to use your own memory allocation routines,
3033define PNG_USER_MEM_SUPPORTED and use
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3034png_create_write_struct_2() instead of png_create_write_struct():
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]3035
3036 png_structp png_ptr = png_create_write_struct_2
3037 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
3038 user_error_fn, user_warning_fn, (png_voidp)
3039 user_mem_ptr, user_malloc_fn, user_free_fn);
3040
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3041After you have these structures, you will need to set up the
3042error handling. When libpng encounters an error, it expects to
3043longjmp() back to your routine. Therefore, you will need to call
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3044setjmp() and pass the png_jmpbuf(png_ptr). If you
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3045write the file from different routines, you will need to update
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3046the png_jmpbuf(png_ptr) every time you enter a new routine that will
3047call a png_*() function. See your documentation of setjmp/longjmp
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3048for your compiler for more information on setjmp/longjmp. See
3049the discussion on libpng error handling in the Customizing Libpng
3050section below for more information on the libpng error handling.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3051
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3052 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3053 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3054 png_destroy_write_struct(&png_ptr, &info_ptr);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]3055 fclose(fp);
3056 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3057 }
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3058 ...
3059 return;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3060
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3061If you would rather avoid the complexity of setjmp/longjmp issues,
Glenn Randers-Pehrson54ac9a92010-04-02 17:06:22 -0500[diff] [blame]3062you can compile libpng with PNG_NO_SETJMP, in which case
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3063errors will result in a call to PNG_ABORT() which defaults to abort().
3064
Glenn Randers-Pehrson54ac9a92010-04-02 17:06:22 -0500[diff] [blame]3065You can #define PNG_ABORT() to a function that does something
3066more useful than abort(), as long as your function does not
3067return.
3068
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3069Now you need to set up the output code. The default for libpng is to
3070use the C function fwrite(). If you use this, you will need to pass a
3071valid FILE * in the function png_init_io(). Be sure that the file is
3072opened in binary mode. Again, if you wish to handle writing data in
3073another way, see the discussion on libpng I/O handling in the Customizing
3074Libpng section below.
3075
3076 png_init_io(png_ptr, fp);
3077
Glenn Randers-Pehrsond60b8fa2006-04-20 21:31:14 -0500[diff] [blame]3078If you are embedding your PNG into a datastream such as MNG, and don't
3079want libpng to write the 8-byte signature, or if you have already
3080written the signature in your application, use
3081
3082 png_set_sig_bytes(png_ptr, 8);
3083
3084to inform libpng that it should not write a signature.
3085
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3086.SS Write callbacks
3087
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3088At this point, you can set up a callback function that will be
3089called after each row has been written, which you can use to control
3090a progress meter or the like. It's demonstrated in pngtest.c.
3091You must supply a function
3092
Glenn Randers-Pehrson81ce8892011-01-24 08:04:37 -0600[diff] [blame]3093 void write_row_callback(png_structp png_ptr, png_uint_32 row,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3094 int pass);
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3095 {
3096 /* put your code here */
3097 }
3098
3099(You can give it another name that you like instead of "write_row_callback")
3100
3101To inform libpng about your function, use
3102
3103 png_set_write_status_fn(png_ptr, write_row_callback);
3104
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3105You now have the option of modifying how the compression library will
3106run. The following functions are mainly for testing, but may be useful
3107in some cases, like if you need to write PNG files extremely fast and
3108are willing to give up some compression, or if you want to get the
3109maximum possible compression at the expense of slower writing. If you
3110have no special needs in this area, let the library do what it wants by
3111not calling this function at all, as it has been tuned to deliver a good
3112speed/compression ratio. The second parameter to png_set_filter() is
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]3113the filter method, for which the only valid values are 0 (as of the
3114July 1999 PNG specification, version 1.2) or 64 (if you are writing
3115a PNG datastream that is to be embedded in a MNG datastream). The third
3116parameter is a flag that indicates which filter type(s) are to be tested
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3117for each scanline. See the PNG specification for details on the specific
3118filter types.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3119
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3120
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3121 /* turn on or off filtering, and/or choose
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3122 specific filters. You can use either a single
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]3123 PNG_FILTER_VALUE_NAME or the bitwise OR of one
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3124 or more PNG_FILTER_NAME masks.
3125 */
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3126 png_set_filter(png_ptr, 0,
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3127 PNG_FILTER_NONE | PNG_FILTER_VALUE_NONE |
3128 PNG_FILTER_SUB | PNG_FILTER_VALUE_SUB |
3129 PNG_FILTER_UP | PNG_FILTER_VALUE_UP |
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]3130 PNG_FILTER_AVG | PNG_FILTER_VALUE_AVG |
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3131 PNG_FILTER_PAETH | PNG_FILTER_VALUE_PAETH|
3132 PNG_ALL_FILTERS);
3133
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]3134If an application wants to start and stop using particular filters during
3135compression, it should start out with all of the filters (to ensure that
3136the previous row of pixels will be stored in case it's needed later),
3137and then add and remove them after the start of compression.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3138
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]3139If you are writing a PNG datastream that is to be embedded in a MNG
3140datastream, the second parameter can be either 0 or 64.
3141
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]3142The png_set_compression_*() functions interface to the zlib compression
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3143library, and should mostly be ignored unless you really know what you are
3144doing. The only generally useful call is png_set_compression_level()
3145which changes how much time zlib spends on trying to compress the image
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3146data. See the Compression Library (zlib.h and algorithm.txt, distributed
3147with zlib) for details on the compression levels.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3148
3149 /* set the zlib compression level */
3150 png_set_compression_level(png_ptr,
3151 Z_BEST_COMPRESSION);
3152
3153 /* set other zlib parameters */
3154 png_set_compression_mem_level(png_ptr, 8);
3155 png_set_compression_strategy(png_ptr,
3156 Z_DEFAULT_STRATEGY);
3157 png_set_compression_window_bits(png_ptr, 15);
3158 png_set_compression_method(png_ptr, 8);
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3159 png_set_compression_buffer_size(png_ptr, 8192)
3160
3161extern PNG_EXPORT(void,png_set_zbuf_size)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3162
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3163.SS Setting the contents of info for output
3164
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3165You now need to fill in the png_info structure with all the data you
3166wish to write before the actual image. Note that the only thing you
3167are allowed to write after the image is the text chunks and the time
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3168chunk (as of PNG Specification 1.2, anyway). See png_write_end() and
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3169the latest PNG specification for more information on that. If you
3170wish to write them before the image, fill them in now, and flag that
3171data as being valid. If you want to wait until after the data, don't
3172fill them until png_write_end(). For all the fields in png_info and
3173their data types, see png.h. For explanations of what the fields
3174contain, see the PNG specification.
3175
3176Some of the more important parts of the png_info are:
3177
3178 png_set_IHDR(png_ptr, info_ptr, width, height,
3179 bit_depth, color_type, interlace_type,
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]3180 compression_type, filter_method)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3181
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3182 width - holds the width of the image
3183 in pixels (up to 2^31).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3184
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3185 height - holds the height of the image
3186 in pixels (up to 2^31).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3187
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3188 bit_depth - holds the bit depth of one of the
3189 image channels.
3190 (valid values are 1, 2, 4, 8, 16
3191 and depend also on the
3192 color_type. See also significant
3193 bits (sBIT) below).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3194
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3195 color_type - describes which color/alpha
3196 channels are present.
3197 PNG_COLOR_TYPE_GRAY
3198 (bit depths 1, 2, 4, 8, 16)
3199 PNG_COLOR_TYPE_GRAY_ALPHA
3200 (bit depths 8, 16)
3201 PNG_COLOR_TYPE_PALETTE
3202 (bit depths 1, 2, 4, 8)
3203 PNG_COLOR_TYPE_RGB
3204 (bit_depths 8, 16)
3205 PNG_COLOR_TYPE_RGB_ALPHA
3206 (bit_depths 8, 16)
3207
3208 PNG_COLOR_MASK_PALETTE
3209 PNG_COLOR_MASK_COLOR
3210 PNG_COLOR_MASK_ALPHA
3211
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3212 interlace_type - PNG_INTERLACE_NONE or
3213 PNG_INTERLACE_ADAM7
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3214
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3215 compression_type - (must be
3216 PNG_COMPRESSION_TYPE_DEFAULT)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3217
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]3218 filter_method - (must be PNG_FILTER_TYPE_DEFAULT
3219 or, if you are writing a PNG to
3220 be embedded in a MNG datastream,
3221 can also be
3222 PNG_INTRAPIXEL_DIFFERENCING)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3223
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]3224If you call png_set_IHDR(), the call must appear before any of the
Glenn Randers-Pehrsond60c8862009-06-15 21:56:14 -0500[diff] [blame]3225other png_set_*() functions, because they might require access to some of
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]3226the IHDR settings. The remaining png_set_*() functions can be called
3227in any order.
3228
Glenn Randers-Pehrsonb5444a12009-06-08 08:36:19 -0500[diff] [blame]3229If you wish, you can reset the compression_type, interlace_type, or
3230filter_method later by calling png_set_IHDR() again; if you do this, the
3231width, height, bit_depth, and color_type must be the same in each call.
Glenn Randers-Pehrson424c9852009-06-02 13:45:15 -0500[diff] [blame]3232
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3233 png_set_PLTE(png_ptr, info_ptr, palette,
3234 num_palette);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3235
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3236 palette - the palette for the file
3237 (array of png_color)
3238 num_palette - number of entries in the palette
3239
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]3240 png_set_gAMA(png_ptr, info_ptr, file_gamma);
3241 png_set_gAMA_fixed(png_ptr, info_ptr, int_file_gamma);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3242
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]3243 file_gamma - the gamma at which the image was
3244 created (PNG_INFO_gAMA)
3245
3246 int_file_gamma - 100,000 times the gamma at which
3247 the image was created
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3248
3249 png_set_sRGB(png_ptr, info_ptr, srgb_intent);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3250
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3251 srgb_intent - the rendering intent
3252 (PNG_INFO_sRGB) The presence of
3253 the sRGB chunk means that the pixel
3254 data is in the sRGB color space.
3255 This chunk also implies specific
3256 values of gAMA and cHRM. Rendering
3257 intent is the CSS-1 property that
3258 has been defined by the International
3259 Color Consortium
3260 (http://www.color.org).
3261 It can be one of
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]3262 PNG_sRGB_INTENT_SATURATION,
3263 PNG_sRGB_INTENT_PERCEPTUAL,
3264 PNG_sRGB_INTENT_ABSOLUTE, or
3265 PNG_sRGB_INTENT_RELATIVE.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3266
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3267
3268 png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr,
3269 srgb_intent);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3270
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3271 srgb_intent - the rendering intent
3272 (PNG_INFO_sRGB) The presence of the
3273 sRGB chunk means that the pixel
3274 data is in the sRGB color space.
3275 This function also causes gAMA and
3276 cHRM chunks with the specific values
3277 that are consistent with sRGB to be
3278 written.
3279
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3280 png_set_iCCP(png_ptr, info_ptr, name, compression_type,
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]3281 profile, proflen);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3282
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]3283 name - The profile name.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3284
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]3285 compression_type - The compression type; always
3286 PNG_COMPRESSION_TYPE_BASE for PNG 1.0.
3287 You may give NULL to this argument to
3288 ignore it.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3289
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]3290 profile - International Color Consortium color
3291 profile data. May contain NULs.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3292
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]3293 proflen - length of profile data in bytes.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3294
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3295 png_set_sBIT(png_ptr, info_ptr, sig_bit);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3296
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3297 sig_bit - the number of significant bits for
3298 (PNG_INFO_sBIT) each of the gray, red,
3299 green, and blue channels, whichever are
3300 appropriate for the given color type
3301 (png_color_16)
3302
Glenn Randers-Pehrson866b62a2009-08-08 16:33:14 -0500[diff] [blame]3303 png_set_tRNS(png_ptr, info_ptr, trans_alpha,
3304 num_trans, trans_color);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3305
Glenn Randers-Pehrson866b62a2009-08-08 16:33:14 -0500[diff] [blame]3306 trans_alpha - array of alpha (transparency)
3307 entries for palette (PNG_INFO_tRNS)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3308
Glenn Randers-Pehrsonb5444a12009-06-08 08:36:19 -0500[diff] [blame]3309 trans_color - graylevel or color sample values
3310 (in order red, green, blue) of the
3311 single transparent color for
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]3312 non-paletted images (PNG_INFO_tRNS)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3313
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3314 num_trans - number of transparent entries
3315 (PNG_INFO_tRNS)
3316
3317 png_set_hIST(png_ptr, info_ptr, hist);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3318
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3319 hist - histogram of palette (array of
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]3320 png_uint_16) (PNG_INFO_hIST)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3321
3322 png_set_tIME(png_ptr, info_ptr, mod_time);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3323
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3324 mod_time - time image was last modified
3325 (PNG_VALID_tIME)
3326
3327 png_set_bKGD(png_ptr, info_ptr, background);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3328
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3329 background - background color (PNG_VALID_bKGD)
3330
3331 png_set_text(png_ptr, info_ptr, text_ptr, num_text);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3332
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3333 text_ptr - array of png_text holding image
3334 comments
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3335
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3336 text_ptr[i].compression - type of compression used
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3337 on "text" PNG_TEXT_COMPRESSION_NONE
3338 PNG_TEXT_COMPRESSION_zTXt
3339 PNG_ITXT_COMPRESSION_NONE
3340 PNG_ITXT_COMPRESSION_zTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3341 text_ptr[i].key - keyword for comment. Must contain
3342 1-79 characters.
3343 text_ptr[i].text - text comments for current
3344 keyword. Can be NULL or empty.
3345 text_ptr[i].text_length - length of text string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3346 after decompression, 0 for iTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3347 text_ptr[i].itxt_length - length of itxt string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3348 after decompression, 0 for tEXt/zTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3349 text_ptr[i].lang - language of comment (NULL or
3350 empty for unknown).
3351 text_ptr[i].translated_keyword - keyword in UTF-8 (NULL
3352 or empty for unknown).
Glenn Randers-Pehrson8f5846f2009-10-31 21:31:08 -0500[diff] [blame]3353 Note that the itxt_length, lang, and lang_key
3354 members of the text_ptr structure only exist
3355 when the library is built with iTXt chunk support.
3356
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3357 num_text - number of comments
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3358
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3359 png_set_sPLT(png_ptr, info_ptr, &palette_ptr,
3360 num_spalettes);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3361
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3362 palette_ptr - array of png_sPLT_struct structures
3363 to be added to the list of palettes
3364 in the info structure.
3365 num_spalettes - number of palette structures to be
3366 added.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3367
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3368 png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y,
3369 unit_type);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3370
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3371 offset_x - positive offset from the left
3372 edge of the screen
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3373
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3374 offset_y - positive offset from the top
3375 edge of the screen
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3376
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3377 unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
3378
3379 png_set_pHYs(png_ptr, info_ptr, res_x, res_y,
3380 unit_type);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3381
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3382 res_x - pixels/unit physical resolution
3383 in x direction
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3384
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3385 res_y - pixels/unit physical resolution
3386 in y direction
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3387
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3388 unit_type - PNG_RESOLUTION_UNKNOWN,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3389 PNG_RESOLUTION_METER
3390
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3391 png_set_sCAL(png_ptr, info_ptr, unit, width, height)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3392
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3393 unit - physical scale units (an integer)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3394
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3395 width - width of a pixel in physical scale units
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3396
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3397 height - height of a pixel in physical scale units
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3398 (width and height are doubles)
3399
3400 png_set_sCAL_s(png_ptr, info_ptr, unit, width, height)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3401
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3402 unit - physical scale units (an integer)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3403
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3404 width - width of a pixel in physical scale units
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3405
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3406 height - height of a pixel in physical scale units
3407 (width and height are strings like "2.54")
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3408
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3409 png_set_unknown_chunks(png_ptr, info_ptr, &unknowns,
3410 num_unknowns)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3411
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3412 unknowns - array of png_unknown_chunk
3413 structures holding unknown chunks
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3414 unknowns[i].name - name of unknown chunk
3415 unknowns[i].data - data of unknown chunk
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3416 unknowns[i].size - size of unknown chunk's data
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3417 unknowns[i].location - position to write chunk in file
3418 0: do not write chunk
3419 PNG_HAVE_IHDR: before PLTE
3420 PNG_HAVE_PLTE: before IDAT
3421 PNG_AFTER_IDAT: after IDAT
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3422
3423The "location" member is set automatically according to
3424what part of the output file has already been written.
3425You can change its value after calling png_set_unknown_chunks()
3426as demonstrated in pngtest.c. Within each of the "locations",
3427the chunks are sequenced according to their position in the
3428structure (that is, the value of "i", which is the order in which
3429the chunk was either read from the input file or defined with
3430png_set_unknown_chunks).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3431
3432A quick word about text and num_text. text is an array of png_text
3433structures. num_text is the number of valid structures in the array.
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3434Each png_text structure holds a language code, a keyword, a text value,
3435and a compression type.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3436
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3437The compression types have the same valid numbers as the compression
3438types of the image data. Currently, the only valid number is zero.
3439However, you can store text either compressed or uncompressed, unlike
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3440images, which always have to be compressed. So if you don't want the
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3441text compressed, set the compression type to PNG_TEXT_COMPRESSION_NONE.
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3442Because tEXt and zTXt chunks don't have a language field, if you
3443specify PNG_TEXT_COMPRESSION_NONE or PNG_TEXT_COMPRESSION_zTXt
3444any language code or translated keyword will not be written out.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3445
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3446Until text gets around 1000 bytes, it is not worth compressing it.
3447After the text has been written out to the file, the compression type
3448is set to PNG_TEXT_COMPRESSION_NONE_WR or PNG_TEXT_COMPRESSION_zTXt_WR,
3449so that it isn't written out again at the end (in case you are calling
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3450png_write_end() with the same struct).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3451
3452The keywords that are given in the PNG Specification are:
3453
3454 Title Short (one line) title or
3455 caption for image
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3456
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3457 Author Name of image's creator
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3458
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3459 Description Description of image (possibly long)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3460
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3461 Copyright Copyright notice
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3462
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3463 Creation Time Time of original image creation
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3464 (usually RFC 1123 format, see below)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3465
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3466 Software Software used to create the image
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3467
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3468 Disclaimer Legal disclaimer
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3469
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3470 Warning Warning of nature of content
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3471
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3472 Source Device used to create the image
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3473
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3474 Comment Miscellaneous comment; conversion
3475 from other image format
3476
3477The keyword-text pairs work like this. Keywords should be short
3478simple descriptions of what the comment is about. Some typical
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3479keywords are found in the PNG specification, as is some recommendations
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3480on keywords. You can repeat keywords in a file. You can even write
3481some text before the image and some after. For example, you may want
3482to put a description of the image before the image, but leave the
3483disclaimer until after, so viewers working over modem connections
3484don't have to wait for the disclaimer to go over the modem before
3485they start seeing the image. Finally, keywords should be full
3486words, not abbreviations. Keywords and text are in the ISO 8859-1
3487(Latin-1) character set (a superset of regular ASCII) and can not
3488contain NUL characters, and should not contain control or other
3489unprintable characters. To make the comments widely readable, stick
3490with basic ASCII, and avoid machine specific character set extensions
3491like the IBM-PC character set. The keyword must be present, but
3492you can leave off the text string on non-compressed pairs.
3493Compressed pairs must have a text string, as only the text string
3494is compressed anyway, so the compression would be meaningless.
3495
3496PNG supports modification time via the png_time structure. Two
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3497conversion routines are provided, png_convert_from_time_t() for
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3498time_t and png_convert_from_struct_tm() for struct tm. The
3499time_t routine uses gmtime(). You don't have to use either of
3500these, but if you wish to fill in the png_time structure directly,
3501you should provide the time in universal time (GMT) if possible
3502instead of your local time. Note that the year number is the full
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3503year (e.g. 1998, rather than 98 - PNG is year 2000 compliant!), and
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3504that months start with 1.
3505
3506If you want to store the time of the original image creation, you should
3507use a plain tEXt chunk with the "Creation Time" keyword. This is
3508necessary because the "creation time" of a PNG image is somewhat vague,
3509depending on whether you mean the PNG file, the time the image was
3510created in a non-PNG format, a still photo from which the image was
3511scanned, or possibly the subject matter itself. In order to facilitate
3512machine-readable dates, it is recommended that the "Creation Time"
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3513tEXt chunk use RFC 1123 format dates (e.g. "22 May 1997 18:07:10 GMT"),
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3514although this isn't a requirement. Unlike the tIME chunk, the
3515"Creation Time" tEXt chunk is not expected to be automatically changed
3516by the software. To facilitate the use of RFC 1123 dates, a function
3517png_convert_to_rfc1123(png_timep) is provided to convert from PNG
3518time to an RFC 1123 format string.
3519
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3520.SS Writing unknown chunks
3521
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3522You can use the png_set_unknown_chunks function to queue up chunks
3523for writing. You give it a chunk name, raw data, and a size; that's
3524all there is to it. The chunks will be written by the next following
3525png_write_info_before_PLTE, png_write_info, or png_write_end function.
3526Any chunks previously read into the info structure's unknown-chunk
3527list will also be written out in a sequence that satisfies the PNG
3528specification's ordering rules.
3529
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3530.SS The high-level write interface
3531
3532At this point there are two ways to proceed; through the high-level
3533write interface, or through a sequence of low-level write operations.
3534You can use the high-level interface if your image data is present
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3535in the info structure. All defined output
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]3536transformations are permitted, enabled by the following masks.
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3537
3538 PNG_TRANSFORM_IDENTITY No transformation
3539 PNG_TRANSFORM_PACKING Pack 1, 2 and 4-bit samples
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3540 PNG_TRANSFORM_PACKSWAP Change order of packed
3541 pixels to LSB first
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3542 PNG_TRANSFORM_INVERT_MONO Invert monochrome images
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3543 PNG_TRANSFORM_SHIFT Normalize pixels to the
3544 sBIT depth
3545 PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA
3546 to BGRA
3547 PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA
3548 to AG
3549 PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity
3550 to transparency
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3551 PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples
Glenn Randers-Pehrson1eb14e92008-12-10 07:14:45 -0600[diff] [blame]3552 PNG_TRANSFORM_STRIP_FILLER Strip out filler
3553 bytes (deprecated).
3554 PNG_TRANSFORM_STRIP_FILLER_BEFORE Strip out leading
3555 filler bytes
3556 PNG_TRANSFORM_STRIP_FILLER_AFTER Strip out trailing
3557 filler bytes
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3558
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3559If you have valid image data in the info structure (you can use
3560png_set_rows() to put image data in the info structure), simply do this:
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3561
3562 png_write_png(png_ptr, info_ptr, png_transforms, NULL)
3563
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]3564where png_transforms is an integer containing the bitwise OR of some set of
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3565transformation flags. This call is equivalent to png_write_info(),
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3566followed the set of transformations indicated by the transform mask,
3567then png_write_image(), and finally png_write_end().
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3568
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3569(The final parameter of this call is not yet used. Someday it might point
3570to transformation parameters required by some future output transform.)
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3571
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]3572You must use png_transforms and not call any png_set_transform() functions
3573when you use png_write_png().
3574
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3575.SS The low-level write interface
3576
3577If you are going the low-level route instead, you are now ready to
3578write all the file information up to the actual image data. You do
3579this with a call to png_write_info().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3580
3581 png_write_info(png_ptr, info_ptr);
3582
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3583Note that there is one transformation you may need to do before
3584png_write_info(). In PNG files, the alpha channel in an image is the
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3585level of opacity. If your data is supplied as a level of transparency,
3586you can invert the alpha channel before you write it, so that 0 is
3587fully transparent and 255 (in 8-bit or paletted images) or 65535
3588(in 16-bit images) is fully opaque, with
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3589
3590 png_set_invert_alpha(png_ptr);
3591
3592This must appear before png_write_info() instead of later with the
3593other transformations because in the case of paletted images the tRNS
3594chunk data has to be inverted before the tRNS chunk is written. If
3595your image is not a paletted image, the tRNS data (which in such cases
3596represents a single color to be rendered as transparent) won't need to
3597be changed, and you can safely do this transformation after your
3598png_write_info() call.
3599
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]3600If you need to write a private chunk that you want to appear before
3601the PLTE chunk when PLTE is present, you can write the PNG info in
3602two steps, and insert code to write your own chunk between them:
3603
3604 png_write_info_before_PLTE(png_ptr, info_ptr);
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3605 png_set_unknown_chunks(png_ptr, info_ptr, ...);
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]3606 png_write_info(png_ptr, info_ptr);
3607
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3608After you've written the file information, you can set up the library
3609to handle any special transformations of the image data. The various
3610ways to transform the data will be described in the order that they
3611should occur. This is important, as some of these change the color
3612type and/or bit depth of the data, and some others only work on
3613certain color types and bit depths. Even though each transformation
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3614checks to see if it has data that it can do something with, you should
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3615make sure to only enable a transformation if it will be valid for the
3616data. For example, don't swap red and blue on grayscale data.
3617
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]3618PNG files store RGB pixels packed into 3 or 6 bytes. This code tells
Glenn Randers-Pehrson68ea2432000-04-01 21:10:05 -0600[diff] [blame]3619the library to strip input data that has 4 or 8 bytes per pixel down
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3620to 3 or 6 bytes (or strip 2 or 4-byte grayscale+filler data to 1 or 2
3621bytes per pixel).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3622
3623 png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
3624
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3625where the 0 is unused, and the location is either PNG_FILLER_BEFORE or
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3626PNG_FILLER_AFTER, depending upon whether the filler byte in the pixel
3627is stored XRGB or RGBX.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3628
3629PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
3630they can, resulting in, for example, 8 pixels per byte for 1 bit files.
3631If the data is supplied at 1 pixel per byte, use this code, which will
3632correctly pack the pixels into a single byte:
3633
3634 png_set_packing(png_ptr);
3635
3636PNG files reduce possible bit depths to 1, 2, 4, 8, and 16. If your
3637data is of another bit depth, you can write an sBIT chunk into the
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3638file so that decoders can recover the original data if desired.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3639
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3640 /* Set the true bit depth of the image data */
3641 if (color_type & PNG_COLOR_MASK_COLOR)
3642 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3643 sig_bit.red = true_bit_depth;
3644 sig_bit.green = true_bit_depth;
3645 sig_bit.blue = true_bit_depth;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3646 }
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3647
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3648 else
3649 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3650 sig_bit.gray = true_bit_depth;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3651 }
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3652
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3653 if (color_type & PNG_COLOR_MASK_ALPHA)
3654 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3655 sig_bit.alpha = true_bit_depth;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3656 }
3657
3658 png_set_sBIT(png_ptr, info_ptr, &sig_bit);
3659
3660If the data is stored in the row buffer in a bit depth other than
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3661one supported by PNG (e.g. 3 bit data in the range 0-7 for a 4-bit PNG),
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3662this will scale the values to appear to be the correct bit depth as
3663is required by PNG.
3664
3665 png_set_shift(png_ptr, &sig_bit);
3666
3667PNG files store 16 bit pixels in network byte order (big-endian,
3668ie. most significant bits first). This code would be used if they are
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3669supplied the other way (little-endian, i.e. least significant bits
3670first, the way PCs store them):
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3671
3672 if (bit_depth > 8)
3673 png_set_swap(png_ptr);
3674
3675If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you
3676need to change the order the pixels are packed into bytes, you can use:
3677
3678 if (bit_depth < 8)
3679 png_set_packswap(png_ptr);
3680
3681PNG files store 3 color pixels in red, green, blue order. This code
3682would be used if they are supplied as blue, green, red:
3683
3684 png_set_bgr(png_ptr);
3685
3686PNG files describe monochrome as black being zero and white being
3687one. This code would be used if the pixels are supplied with this reversed
3688(black being one and white being zero):
3689
3690 png_set_invert_mono(png_ptr);
3691
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3692Finally, you can write your own transformation function if none of
3693the existing ones meets your needs. This is done by setting a callback
3694with
3695
3696 png_set_write_user_transform_fn(png_ptr,
3697 write_transform_fn);
3698
3699You must supply the function
3700
Glenn Randers-Pehrson81ce8892011-01-24 08:04:37 -0600[diff] [blame]3701 void write_transform_fn(png_structp png_ptr ptr,
3702 row_info_ptr row_info, png_bytep data)
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3703
3704See pngtest.c for a working example. Your function will be called
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]3705before any of the other transformations are processed. If supported
3706libpng also supplies an information routine that may be called from
3707your callback:
3708
3709 png_get_current_row_number(png_ptr);
3710
3711This returns the current row passed to the transform. Even with interlaced
3712images the value returned is the row in the final output image.
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3713
3714You can also set up a pointer to a user structure for use by your
3715callback function.
3716
3717 png_set_user_transform_info(png_ptr, user_ptr, 0, 0);
3718
3719The user_channels and user_depth parameters of this function are ignored
3720when writing; you can set them to zero as shown.
3721
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3722You can retrieve the pointer via the function png_get_user_transform_ptr().
3723For example:
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3724
3725 voidp write_user_transform_ptr =
3726 png_get_user_transform_ptr(png_ptr);
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3727
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3728It is possible to have libpng flush any pending output, either manually,
3729or automatically after a certain number of lines have been written. To
3730flush the output stream a single time call:
3731
3732 png_write_flush(png_ptr);
3733
3734and to have libpng flush the output stream periodically after a certain
3735number of scanlines have been written, call:
3736
3737 png_set_flush(png_ptr, nrows);
3738
3739Note that the distance between rows is from the last time png_write_flush()
3740was called, or the first row of the image if it has never been called.
3741So if you write 50 lines, and then png_set_flush 25, it will flush the
3742output on the next scanline, and every 25 lines thereafter, unless
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3743png_write_flush() is called before 25 more lines have been written.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3744If nrows is too small (less than about 10 lines for a 640 pixel wide
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3745RGB image) the image compression may decrease noticeably (although this
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3746may be acceptable for real-time applications). Infrequent flushing will
3747only degrade the compression performance by a few percent over images
3748that do not use flushing.
3749
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3750.SS Writing the image data
3751
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3752That's it for the transformations. Now you can write the image data.
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3753The simplest way to do this is in one function call. If you have the
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3754whole image in memory, you can just call png_write_image() and libpng
3755will write the image. You will need to pass in an array of pointers to
3756each row. This function automatically handles interlacing, so you don't
3757need to call png_set_interlace_handling() or call this function multiple
3758times, or any of that other stuff necessary with png_write_rows().
3759
3760 png_write_image(png_ptr, row_pointers);
3761
3762where row_pointers is:
3763
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]3764 png_byte *row_pointers[height];
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3765
3766You can point to void or char or whatever you use for pixels.
3767
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]3768If you don't want to write the whole image at once, you can
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3769use png_write_rows() instead. If the file is not interlaced,
3770this is simple:
3771
3772 png_write_rows(png_ptr, row_pointers,
3773 number_of_rows);
3774
3775row_pointers is the same as in the png_write_image() call.
3776
3777If you are just writing one row at a time, you can do this with
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3778a single row_pointer instead of an array of row_pointers:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3779
3780 png_bytep row_pointer = row;
3781
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3782 png_write_row(png_ptr, row_pointer);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3783
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3784When the file is interlaced, things can get a good deal more complicated.
3785The only currently (as of the PNG Specification version 1.2, dated July
37861999) defined interlacing scheme for PNG files is the "Adam7" interlace
3787scheme, that breaks down an image into seven smaller images of varying
3788size. libpng will build these images for you, or you can do them
3789yourself. If you want to build them yourself, see the PNG specification
3790for details of which pixels to write when.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3791
3792If you don't want libpng to handle the interlacing details, just
3793use png_set_interlace_handling() and call png_write_rows() the
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]3794correct number of times to write all the sub-images
3795(png_set_interlace_handling() returns the number of sub-images.)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3796
3797If you want libpng to build the sub-images, call this before you start
3798writing any rows:
3799
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]3800 number_of_passes = png_set_interlace_handling(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3801
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3802This will return the number of passes needed. Currently, this is seven,
3803but may change if another interlace type is added.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3804
3805Then write the complete image number_of_passes times.
3806
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]3807 png_write_rows(png_ptr, row_pointers, number_of_rows);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3808
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]3809Think carefully before you write an interlaced image. Typically code that
3810reads such images reads all the image data into memory, uncompressed, before
3811doing any processing. Only code that can display an image on the fly can
3812take advantage of the interlacing and even then the image has to be exactly
3813the correct size for the output device, because scaling an image requires
3814adjacent pixels and these are not available until all the passes have been
3815read.
3816
3817If you do write an interlaced image you will hardly ever need to handle
3818the interlacing yourself. Call png_set_interlace_handling() and use the
3819approach described above.
3820
3821The only time it is conceivable that you will really need to write an
3822interlaced image pass-by-pass is when you have read one pass by pass and
3823made some pixel-by-pixel transformation to it, as described in the read
3824code above. In this case use the PNG_PASS_ROWS and PNG_PASS_COLS macros
3825to determine the size of each sub-image in turn and simply write the rows
3826you obtained from the read code.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3827
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3828.SS Finishing a sequential write
3829
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3830After you are finished writing the image, you should finish writing
3831the file. If you are interested in writing comments or time, you should
3832pass an appropriately filled png_info pointer. If you are not interested,
3833you can pass NULL.
3834
3835 png_write_end(png_ptr, info_ptr);
3836
3837When you are done, you can free all memory used by libpng like this:
3838
3839 png_destroy_write_struct(&png_ptr, &info_ptr);
3840
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3841It is also possible to individually free the info_ptr members that
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]3842point to libpng-allocated storage with the following function:
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3843
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3844 png_free_data(png_ptr, info_ptr, mask, seq)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3845
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3846 mask - identifies data to be freed, a mask
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]3847 containing the bitwise OR of one or
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3848 more of
3849 PNG_FREE_PLTE, PNG_FREE_TRNS,
3850 PNG_FREE_HIST, PNG_FREE_ICCP,
3851 PNG_FREE_PCAL, PNG_FREE_ROWS,
3852 PNG_FREE_SCAL, PNG_FREE_SPLT,
3853 PNG_FREE_TEXT, PNG_FREE_UNKN,
3854 or simply PNG_FREE_ALL
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3855
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3856 seq - sequence number of item to be freed
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3857 (-1 for all items)
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3858
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]3859This function may be safely called when the relevant storage has
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3860already been freed, or has not yet been allocated, or was allocated
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3861by the user and not by libpng, and will in those cases do nothing.
3862The "seq" parameter is ignored if only one item of the selected data
3863type, such as PLTE, is allowed. If "seq" is not -1, and multiple items
3864are allowed for the data type identified in the mask, such as text or
3865sPLT, only the n'th item in the structure is freed, where n is "seq".
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3866
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3867If you allocated data such as a palette that you passed in to libpng
3868with png_set_*, you must not free it until just before the call to
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]3869png_destroy_write_struct().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3870
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3871The default behavior is only to free data that was allocated internally
3872by libpng. This can be changed, so that libpng will not free the data,
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3873or so that it will free data that was allocated by the user with png_malloc()
3874or png_zalloc() and passed in via a png_set_*() function, with
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3875
3876 png_data_freer(png_ptr, info_ptr, freer, mask)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3877
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3878 freer - one of
3879 PNG_DESTROY_WILL_FREE_DATA
3880 PNG_SET_WILL_FREE_DATA
3881 PNG_USER_WILL_FREE_DATA
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3882
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3883 mask - which data elements are affected
3884 same choices as in png_free_data()
3885
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3886For example, to transfer responsibility for some data from a read structure
3887to a write structure, you could use
3888
3889 png_data_freer(read_ptr, read_info_ptr,
3890 PNG_USER_WILL_FREE_DATA,
3891 PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3892
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3893 png_data_freer(write_ptr, write_info_ptr,
3894 PNG_DESTROY_WILL_FREE_DATA,
3895 PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST)
3896
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3897thereby briefly reassigning responsibility for freeing to the user but
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3898immediately afterwards reassigning it once more to the write_destroy
3899function. Having done this, it would then be safe to destroy the read
3900structure and continue to use the PLTE, tRNS, and hIST data in the write
3901structure.
3902
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3903This function only affects data that has already been allocated.
3904You can call this function before calling after the png_set_*() functions
3905to control whether the user or png_destroy_*() is supposed to free the data.
3906When the user assumes responsibility for libpng-allocated data, the
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3907application must use
3908png_free() to free it, and when the user transfers responsibility to libpng
3909for data that the user has allocated, the user must have used png_malloc()
3910or png_zalloc() to allocate it.
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3911
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3912If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword
3913separately, do not transfer responsibility for freeing text_ptr to libpng,
3914because when libpng fills a png_text structure it combines these members with
3915the key member, and png_free_data() will free only text_ptr.key. Similarly,
3916if you transfer responsibility for free'ing text_ptr from libpng to your
3917application, your application must not separately free those members.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3918For a more compact example of writing a PNG image, see the file example.c.
3919
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3920.SH V. Modifying/Customizing libpng:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3921
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]3922There are two issues here. The first is changing how libpng does
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3923standard things like memory allocation, input/output, and error handling.
3924The second deals with more complicated things like adding new chunks,
3925adding new transformations, and generally changing how libpng works.
Glenn Randers-Pehrson231e6872001-01-12 15:13:06 -0600[diff] [blame]3926Both of those are compile-time issues; that is, they are generally
3927determined at the time the code is written, and there is rarely a need
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]3928to provide the user with a means of changing them.
Glenn Randers-Pehrson231e6872001-01-12 15:13:06 -0600[diff] [blame]3929
3930Memory allocation, input/output, and error handling
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3931
3932All of the memory allocation, input/output, and error handling in libpng
Glenn Randers-Pehrson231e6872001-01-12 15:13:06 -0600[diff] [blame]3933goes through callbacks that are user-settable. The default routines are
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3934in pngmem.c, pngrio.c, pngwio.c, and pngerror.c, respectively. To change
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]3935these functions, call the appropriate png_set_*_fn() function.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3936
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3937Memory allocation is done through the functions png_malloc(), png_calloc(),
3938and png_free(). These currently just call the standard C functions.
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]3939png_calloc() calls png_malloc() and then clears the newly
3940allocated memory to zero. There is limited support for certain systems
3941with segmented memory architectures and the types of pointers declared by
3942png.h match this; you will have to use appropriate pointers in your
3943application. Since it is
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3944unlikely that the method of handling memory allocation on a platform
3945will change between applications, these functions must be modified in
3946the library at compile time. If you prefer to use a different method
3947of allocating and freeing data, you can use png_create_read_struct_2() or
3948png_create_write_struct_2() to register your own functions as described
3949above. These functions also provide a void pointer that can be retrieved
3950via
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3951
3952 mem_ptr=png_get_mem_ptr(png_ptr);
3953
3954Your replacement memory functions must have prototypes as follows:
3955
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3956 png_voidp malloc_fn(png_structp png_ptr,
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]3957 png_alloc_size_t size);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3958
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3959 void free_fn(png_structp png_ptr, png_voidp ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3960
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]3961Your malloc_fn() must return NULL in case of failure. The png_malloc()
3962function will normally call png_error() if it receives a NULL from the
3963system memory allocator or from your replacement malloc_fn().
Glenn Randers-Pehrson82ae3832001-04-20 10:32:10 -0500[diff] [blame]3964
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]3965Your free_fn() will never be called with a NULL ptr, since libpng's
3966png_free() checks for NULL before calling free_fn().
3967
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3968Input/Output in libpng is done through png_read() and png_write(),
3969which currently just call fread() and fwrite(). The FILE * is stored in
3970png_struct and is initialized via png_init_io(). If you wish to change
3971the method of I/O, the library supplies callbacks that you can set
3972through the function png_set_read_fn() and png_set_write_fn() at run
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3973time, instead of calling the png_init_io() function. These functions
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3974also provide a void pointer that can be retrieved via the function
3975png_get_io_ptr(). For example:
3976
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]3977 png_set_read_fn(png_structp read_ptr,
3978 voidp read_io_ptr, png_rw_ptr read_data_fn)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3979
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]3980 png_set_write_fn(png_structp write_ptr,
3981 voidp write_io_ptr, png_rw_ptr write_data_fn,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3982 png_flush_ptr output_flush_fn);
3983
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]3984 voidp read_io_ptr = png_get_io_ptr(read_ptr);
3985 voidp write_io_ptr = png_get_io_ptr(write_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3986
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3987The replacement I/O functions must have prototypes as follows:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3988
3989 void user_read_data(png_structp png_ptr,
Glenn Randers-Pehrson837a3d12002-05-10 20:19:58 -0500[diff] [blame]3990 png_bytep data, png_size_t length);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3991
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3992 void user_write_data(png_structp png_ptr,
Glenn Randers-Pehrson837a3d12002-05-10 20:19:58 -0500[diff] [blame]3993 png_bytep data, png_size_t length);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3994
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3995 void user_flush_data(png_structp png_ptr);
3996
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]3997The user_read_data() function is responsible for detecting and
3998handling end-of-data errors.
3999
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4000Supplying NULL for the read, write, or flush functions sets them back
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]4001to using the default C stream functions, which expect the io_ptr to
4002point to a standard *FILE structure. It is probably a mistake
4003to use NULL for one of write_data_fn and output_flush_fn but not both
4004of them, unless you have built libpng with PNG_NO_WRITE_FLUSH defined.
4005It is an error to read from a write stream, and vice versa.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4006
4007Error handling in libpng is done through png_error() and png_warning().
4008Errors handled through png_error() are fatal, meaning that png_error()
4009should never return to its caller. Currently, this is handled via
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4010setjmp() and longjmp() (unless you have compiled libpng with
Glenn Randers-Pehrson54ac9a92010-04-02 17:06:22 -0500[diff] [blame]4011PNG_NO_SETJMP, in which case it is handled via PNG_ABORT()),
Glenn Randers-Pehrson60988072010-04-13 22:11:06 -0500[diff] [blame]4012but you could change this to do things like exit() if you should wish,
Glenn Randers-Pehrson54ac9a92010-04-02 17:06:22 -0500[diff] [blame]4013as long as your function does not return.
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4014
4015On non-fatal errors, png_warning() is called
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4016to print a warning message, and then control returns to the calling code.
4017By default png_error() and png_warning() print a message on stderr via
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]4018fprintf() unless the library is compiled with PNG_NO_CONSOLE_IO defined
4019(because you don't want the messages) or PNG_NO_STDIO defined (because
4020fprintf() isn't available). If you wish to change the behavior of the error
4021functions, you will need to set up your own message callbacks. These
4022functions are normally supplied at the time that the png_struct is created.
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4023It is also possible to redirect errors and warnings to your own replacement
4024functions after png_create_*_struct() has been called by calling:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4025
4026 png_set_error_fn(png_structp png_ptr,
4027 png_voidp error_ptr, png_error_ptr error_fn,
4028 png_error_ptr warning_fn);
4029
4030 png_voidp error_ptr = png_get_error_ptr(png_ptr);
4031
4032If NULL is supplied for either error_fn or warning_fn, then the libpng
4033default function will be used, calling fprintf() and/or longjmp() if a
4034problem is encountered. The replacement error functions should have
4035parameters as follows:
4036
4037 void user_error_fn(png_structp png_ptr,
4038 png_const_charp error_msg);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4039
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4040 void user_warning_fn(png_structp png_ptr,
4041 png_const_charp warning_msg);
4042
4043The motivation behind using setjmp() and longjmp() is the C++ throw and
4044catch exception handling methods. This makes the code much easier to write,
4045as there is no need to check every return code of every function call.
4046However, there are some uncertainties about the status of local variables
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]4047after a longjmp, so the user may want to be careful about doing anything
4048after setjmp returns non-zero besides returning itself. Consult your
4049compiler documentation for more details. For an alternative approach, you
4050may wish to use the "cexcept" facility (see http://cexcept.sourceforge.net).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4051
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4052.SS Custom chunks
4053
4054If you need to read or write custom chunks, you may need to get deeper
4055into the libpng code. The library now has mechanisms for storing
4056and writing chunks of unknown type; you can even declare callbacks
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]4057for custom chunks. However, this may not be good enough if the
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4058library code itself needs to know about interactions between your
4059chunk and existing `intrinsic' chunks.
4060
4061If you need to write a new intrinsic chunk, first read the PNG
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]4062specification. Acquire a first level of understanding of how it works.
4063Pay particular attention to the sections that describe chunk names,
4064and look at how other chunks were designed, so you can do things
4065similarly. Second, check out the sections of libpng that read and
4066write chunks. Try to find a chunk that is similar to yours and use
4067it as a template. More details can be found in the comments inside
4068the code. It is best to handle unknown chunks in a generic method,
4069via callback functions, instead of by modifying libpng functions.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4070
4071If you wish to write your own transformation for the data, look through
4072the part of the code that does the transformations, and check out some of
4073the simpler ones to get an idea of how they work. Try to find a similar
4074transformation to the one you want to add and copy off of it. More details
4075can be found in the comments inside the code itself.
4076
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4077.SS Configuring for 16 bit platforms
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4078
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4079You will want to look into zconf.h to tell zlib (and thus libpng) that
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4080it cannot allocate more then 64K at a time. Even if you can, the memory
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]4081won't be accessible. So limit zlib and libpng to 64K by defining MAXSEG_64K.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4082
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4083.SS Configuring for DOS
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4084
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4085For DOS users who only have access to the lower 640K, you will
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4086have to limit zlib's memory usage via a png_set_compression_mem_level()
4087call. See zlib.h or zconf.h in the zlib library for more information.
4088
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4089.SS Configuring for Medium Model
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4090
4091Libpng's support for medium model has been tested on most of the popular
4092compilers. Make sure MAXSEG_64K gets defined, USE_FAR_KEYWORD gets
4093defined, and FAR gets defined to far in pngconf.h, and you should be
4094all set. Everything in the library (except for zlib's structure) is
4095expecting far data. You must use the typedefs with the p or pp on
4096the end for pointers (or at least look at them and be careful). Make
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4097note that the rows of data are defined as png_bytepp, which is an
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4098unsigned char far * far *.
4099
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4100.SS Configuring for gui/windowing platforms:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4101
4102You will need to write new error and warning functions that use the GUI
4103interface, as described previously, and set them to be the error and
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]4104warning functions at the time that png_create_*_struct() is called,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4105in order to have them available during the structure initialization.
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]4106They can be changed later via png_set_error_fn(). On some compilers,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4107you may also have to change the memory allocators (png_malloc, etc.).
4108
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4109.SS Configuring for compiler xxx:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4110
Glenn Randers-Pehrsonbeb572e2006-08-19 13:59:24 -0500[diff] [blame]4111All includes for libpng are in pngconf.h. If you need to add, change
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]4112or delete an include, this is the place to do it.
4113The includes that are not needed outside libpng are placed in pngpriv.h,
4114which is only used by the routines inside libpng itself.
4115The files in libpng proper only include pngpriv.h and png.h, which
4116in turn includes pngconf.h.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4117
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4118.SS Configuring zlib:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4119
4120There are special functions to configure the compression. Perhaps the
4121most useful one changes the compression level, which currently uses
4122input compression values in the range 0 - 9. The library normally
4123uses the default compression level (Z_DEFAULT_COMPRESSION = 6). Tests
4124have shown that for a large majority of images, compression values in
4125the range 3-6 compress nearly as well as higher levels, and do so much
4126faster. For online applications it may be desirable to have maximum speed
4127(Z_BEST_SPEED = 1). With versions of zlib after v0.99, you can also
4128specify no compression (Z_NO_COMPRESSION = 0), but this would create
4129files larger than just storing the raw bitmap. You can specify the
4130compression level by calling:
4131
4132 png_set_compression_level(png_ptr, level);
4133
4134Another useful one is to reduce the memory level used by the library.
4135The memory level defaults to 8, but it can be lowered if you are
4136short on memory (running DOS, for example, where you only have 640K).
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]4137Note that the memory level does have an effect on compression; among
4138other things, lower levels will result in sections of incompressible
4139data being emitted in smaller stored blocks, with a correspondingly
4140larger relative overhead of up to 15% in the worst case.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4141
4142 png_set_compression_mem_level(png_ptr, level);
4143
4144The other functions are for configuring zlib. They are not recommended
4145for normal use and may result in writing an invalid PNG file. See
4146zlib.h for more information on what these mean.
4147
4148 png_set_compression_strategy(png_ptr,
4149 strategy);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4150
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4151 png_set_compression_window_bits(png_ptr,
4152 window_bits);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4153
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4154 png_set_compression_method(png_ptr, method);
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4155 png_set_compression_buffer_size(png_ptr, size);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4156
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4157.SS Controlling row filtering
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4158
4159If you want to control whether libpng uses filtering or not, which
4160filters are used, and how it goes about picking row filters, you
4161can call one of these functions. The selection and configuration
4162of row filters can have a significant impact on the size and
4163encoding speed and a somewhat lesser impact on the decoding speed
4164of an image. Filtering is enabled by default for RGB and grayscale
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4165images (with and without alpha), but not for paletted images nor
4166for any images with bit depths less than 8 bits/pixel.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4167
4168The 'method' parameter sets the main filtering method, which is
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]4169currently only '0' in the PNG 1.2 specification. The 'filters'
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4170parameter sets which filter(s), if any, should be used for each
4171scanline. Possible values are PNG_ALL_FILTERS and PNG_NO_FILTERS
4172to turn filtering on and off, respectively.
4173
4174Individual filter types are PNG_FILTER_NONE, PNG_FILTER_SUB,
4175PNG_FILTER_UP, PNG_FILTER_AVG, PNG_FILTER_PAETH, which can be bitwise
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]4176ORed together with '|' to specify one or more filters to use.
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]4177These filters are described in more detail in the PNG specification.
4178If you intend to change the filter type during the course of writing
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4179the image, you should start with flags set for all of the filters
4180you intend to use so that libpng can initialize its internal
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]4181structures appropriately for all of the filter types. (Note that this
4182means the first row must always be adaptively filtered, because libpng
4183currently does not allocate the filter buffers until png_write_row()
4184is called for the first time.)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4185
4186 filters = PNG_FILTER_NONE | PNG_FILTER_SUB
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4187 PNG_FILTER_UP | PNG_FILTER_AVG |
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4188 PNG_FILTER_PAETH | PNG_ALL_FILTERS;
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4189
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4190 png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE,
4191 filters);
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]4192 The second parameter can also be
4193 PNG_INTRAPIXEL_DIFFERENCING if you are
4194 writing a PNG to be embedded in a MNG
4195 datastream. This parameter must be the
4196 same as the value of filter_method used
4197 in png_set_IHDR().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4198
4199It is also possible to influence how libpng chooses from among the
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]4200available filters. This is done in one or both of two ways - by
4201telling it how important it is to keep the same filter for successive
4202rows, and by telling it the relative computational costs of the filters.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4203
4204 double weights[3] = {1.5, 1.3, 1.1},
4205 costs[PNG_FILTER_VALUE_LAST] =
4206 {1.0, 1.3, 1.3, 1.5, 1.7};
4207
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]4208 png_set_filter_heuristics(png_ptr,
4209 PNG_FILTER_HEURISTIC_WEIGHTED, 3,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4210 weights, costs);
4211
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4212The weights are multiplying factors that indicate to libpng that the
4213row filter should be the same for successive rows unless another row filter
4214is that many times better than the previous filter. In the above example,
4215if the previous 3 filters were SUB, SUB, NONE, the SUB filter could have a
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4216"sum of absolute differences" 1.5 x 1.3 times higher than other filters
4217and still be chosen, while the NONE filter could have a sum 1.1 times
4218higher than other filters and still be chosen. Unspecified weights are
4219taken to be 1.0, and the specified weights should probably be declining
4220like those above in order to emphasize recent filters over older filters.
4221
4222The filter costs specify for each filter type a relative decoding cost
4223to be considered when selecting row filters. This means that filters
4224with higher costs are less likely to be chosen over filters with lower
4225costs, unless their "sum of absolute differences" is that much smaller.
4226The costs do not necessarily reflect the exact computational speeds of
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]4227the various filters, since this would unduly influence the final image
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4228size.
4229
4230Note that the numbers above were invented purely for this example and
4231are given only to help explain the function usage. Little testing has
4232been done to find optimum values for either the costs or the weights.
4233
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4234.SS Removing unwanted object code
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4235
4236There are a bunch of #define's in pngconf.h that control what parts of
4237libpng are compiled. All the defines end in _SUPPORTED. If you are
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]4238never going to use a capability, you can change the #define to #undef
4239before recompiling libpng and save yourself code and data space, or
4240you can turn off individual capabilities with defines that begin with
4241PNG_NO_.
4242
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4243In libpng-1.5.0 and later, the #define's are in pnglibconf.h instead.
4244
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]4245You can also turn all of the transforms and ancillary chunk capabilities
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4246off en masse with compiler directives that define
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]4247PNG_NO_READ[or WRITE]_TRANSFORMS, or PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS,
4248or all four,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4249along with directives to turn on any of the capabilities that you do
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]4250want. The PNG_NO_READ[or WRITE]_TRANSFORMS directives disable the extra
4251transformations but still leave the library fully capable of reading
4252and writing PNG files with all known public chunks. Use of the
4253PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS directive produces a library
4254that is incapable of reading or writing ancillary chunks. If you are
4255not using the progressive reading capability, you can turn that off
4256with PNG_NO_PROGRESSIVE_READ (don't confuse this with the INTERLACING
4257capability, which you'll still have).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4258
4259All the reading and writing specific code are in separate files, so the
4260linker should only grab the files it needs. However, if you want to
4261make sure, or if you are building a stand alone library, all the
4262reading files start with pngr and all the writing files start with
4263pngw. The files that don't match either (like png.c, pngtrans.c, etc.)
4264are used for both reading and writing, and always need to be included.
4265The progressive reader is in pngpread.c
4266
4267If you are creating or distributing a dynamically linked library (a .so
4268or DLL file), you should not remove or disable any parts of the library,
4269as this will cause applications linked with different versions of the
4270library to fail if they call functions not available in your library.
4271The size of the library itself should not be an issue, because only
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4272those sections that are actually used will be loaded into memory.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4273
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4274.SS Requesting debug printout
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4275
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4276The macro definition PNG_DEBUG can be used to request debugging
4277printout. Set it to an integer value in the range 0 to 3. Higher
4278numbers result in increasing amounts of debugging information. The
4279information is printed to the "stderr" file, unless another file
4280name is specified in the PNG_DEBUG_FILE macro definition.
4281
4282When PNG_DEBUG > 0, the following functions (macros) become available:
4283
4284 png_debug(level, message)
4285 png_debug1(level, message, p1)
4286 png_debug2(level, message, p1, p2)
4287
4288in which "level" is compared to PNG_DEBUG to decide whether to print
4289the message, "message" is the formatted string to be printed,
4290and p1 and p2 are parameters that are to be embedded in the string
4291according to printf-style formatting directives. For example,
4292
4293 png_debug1(2, "foo=%d\n", foo);
4294
4295is expanded to
4296
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4297 if (PNG_DEBUG > 2)
4298 fprintf(PNG_DEBUG_FILE, "foo=%d\n", foo);
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4299
4300When PNG_DEBUG is defined but is zero, the macros aren't defined, but you
4301can still use PNG_DEBUG to control your own debugging:
4302
4303 #ifdef PNG_DEBUG
4304 fprintf(stderr, ...
4305 #endif
4306
4307When PNG_DEBUG = 1, the macros are defined, but only png_debug statements
4308having level = 0 will be printed. There aren't any such statements in
4309this version of libpng, but if you insert some they will be printed.
4310
Glenn Randers-Pehrson56f63962008-10-06 10:16:17 -0500[diff] [blame]4311.SH VI. MNG support
Glenn Randers-Pehrson2ad31ae2000-12-15 08:54:42 -0600[diff] [blame]4312
4313The MNG specification (available at http://www.libpng.org/pub/mng) allows
4314certain extensions to PNG for PNG images that are embedded in MNG datastreams.
4315Libpng can support some of these extensions. To enable them, use the
4316png_permit_mng_features() function:
4317
4318 feature_set = png_permit_mng_features(png_ptr, mask)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4319
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]4320 mask is a png_uint_32 containing the bitwise OR of the
Glenn Randers-Pehrson2ad31ae2000-12-15 08:54:42 -0600[diff] [blame]4321 features you want to enable. These include
4322 PNG_FLAG_MNG_EMPTY_PLTE
4323 PNG_FLAG_MNG_FILTER_64
4324 PNG_ALL_MNG_FEATURES
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4325
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]4326 feature_set is a png_uint_32 that is the bitwise AND of
Glenn Randers-Pehrson2ad31ae2000-12-15 08:54:42 -0600[diff] [blame]4327 your mask with the set of MNG features that is
4328 supported by the version of libpng that you are using.
4329
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]4330It is an error to use this function when reading or writing a standalone
4331PNG file with the PNG 8-byte signature. The PNG datastream must be wrapped
Glenn Randers-Pehrsonf05f8032000-12-23 14:27:39 -0600[diff] [blame]4332in a MNG datastream. As a minimum, it must have the MNG 8-byte signature
4333and the MHDR and MEND chunks. Libpng does not provide support for these
4334or any other MNG chunks; your application must provide its own support for
4335them. You may wish to consider using libmng (available at
4336http://www.libmng.com) instead.
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]4337
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]4338.SH VII. Changes to Libpng from version 0.88
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4339
4340It should be noted that versions of libpng later than 0.96 are not
4341distributed by the original libpng author, Guy Schalnat, nor by
4342Andreas Dilger, who had taken over from Guy during 1996 and 1997, and
4343distributed versions 0.89 through 0.96, but rather by another member
4344of the original PNG Group, Glenn Randers-Pehrson. Guy and Andreas are
4345still alive and well, but they have moved on to other things.
4346
4347The old libpng functions png_read_init(), png_write_init(),
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]4348png_info_init(), png_read_destroy(), and png_write_destroy() have been
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]4349moved to PNG_INTERNAL in version 0.95 to discourage their use. These
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4350functions will be removed from libpng version 1.4.0.
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]4351
4352The preferred method of creating and initializing the libpng structures is
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4353via the png_create_read_struct(), png_create_write_struct(), and
4354png_create_info_struct() because they isolate the size of the structures
4355from the application, allow version error checking, and also allow the
4356use of custom error handling routines during the initialization, which
4357the old functions do not. The functions png_read_destroy() and
4358png_write_destroy() do not actually free the memory that libpng
4359allocated for these structs, but just reset the data structures, so they
4360can be used instead of png_destroy_read_struct() and
4361png_destroy_write_struct() if you feel there is too much system overhead
4362allocating and freeing the png_struct for each image read.
4363
4364Setting the error callbacks via png_set_message_fn() before
4365png_read_init() as was suggested in libpng-0.88 is no longer supported
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4366because this caused applications that do not use custom error functions
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4367to fail if the png_ptr was not initialized to zero. It is still possible
4368to set the error callbacks AFTER png_read_init(), or to change them with
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]4369png_set_error_fn(), which is essentially the same function, but with a new
4370name to force compilation errors with applications that try to use the old
4371method.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4372
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]4373Starting with version 1.0.7, you can find out which version of the library
4374you are using at run-time:
4375
4376 png_uint_32 libpng_vn = png_access_version_number();
4377
4378The number libpng_vn is constructed from the major version, minor
4379version with leading zero, and release number with leading zero,
4380(e.g., libpng_vn for version 1.0.7 is 10007).
4381
4382You can also check which version of png.h you used when compiling your
4383application:
4384
4385 png_uint_32 application_vn = PNG_LIBPNG_VER;
4386
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4387.SH VIII. Changes to Libpng from version 1.0.x to 1.2.x
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]4388
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4389Support for user memory management was enabled by default. To
4390accomplish this, the functions png_create_read_struct_2(),
4391png_create_write_struct_2(), png_set_mem_fn(), png_get_mem_ptr(),
4392png_malloc_default(), and png_free_default() were added.
4393
Glenn Randers-Pehrsond6ea40a2009-11-02 07:32:00 -0600[diff] [blame]4394Support for the iTXt chunk has been enabled by default as of
4395version 1.2.41.
4396
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4397Support for certain MNG features was enabled.
4398
4399Support for numbered error messages was added. However, we never got
4400around to actually numbering the error messages. The function
4401png_set_strip_error_numbers() was added (Note: the prototype for this
4402function was inadvertently removed from png.h in PNG_NO_ASSEMBLER_CODE
4403builds of libpng-1.2.15. It was restored in libpng-1.2.36).
4404
4405The png_malloc_warn() function was added at libpng-1.2.3. This issues
4406a png_warning and returns NULL instead of aborting when it fails to
4407acquire the requested memory allocation.
4408
4409Support for setting user limits on image width and height was enabled
4410by default. The functions png_set_user_limits(), png_get_user_width_max(),
4411and png_get_user_height_max() were added at libpng-1.2.6.
4412
4413The png_set_add_alpha() function was added at libpng-1.2.7.
4414
4415The function png_set_expand_gray_1_2_4_to_8() was added at libpng-1.2.9.
4416Unlike png_set_gray_1_2_4_to_8(), the new function does not expand the
4417tRNS chunk to alpha. The png_set_gray_1_2_4_to_8() function is
4418deprecated.
4419
4420A number of macro definitions in support of runtime selection of
4421assembler code features (especially Intel MMX code support) were
4422added at libpng-1.2.0:
4423
4424 PNG_ASM_FLAG_MMX_SUPPORT_COMPILED
4425 PNG_ASM_FLAG_MMX_SUPPORT_IN_CPU
4426 PNG_ASM_FLAG_MMX_READ_COMBINE_ROW
4427 PNG_ASM_FLAG_MMX_READ_INTERLACE
4428 PNG_ASM_FLAG_MMX_READ_FILTER_SUB
4429 PNG_ASM_FLAG_MMX_READ_FILTER_UP
4430 PNG_ASM_FLAG_MMX_READ_FILTER_AVG
4431 PNG_ASM_FLAG_MMX_READ_FILTER_PAETH
4432 PNG_ASM_FLAGS_INITIALIZED
4433 PNG_MMX_READ_FLAGS
4434 PNG_MMX_FLAGS
4435 PNG_MMX_WRITE_FLAGS
4436 PNG_MMX_FLAGS
4437
4438We added the following functions in support of runtime
4439selection of assembler code features:
4440
4441 png_get_mmx_flagmask()
4442 png_set_mmx_thresholds()
4443 png_get_asm_flags()
4444 png_get_mmx_bitdepth_threshold()
4445 png_get_mmx_rowbytes_threshold()
4446 png_set_asm_flags()
4447
4448We replaced all of these functions with simple stubs in libpng-1.2.20,
4449when the Intel assembler code was removed due to a licensing issue.
4450
Glenn Randers-Pehrson3d893a02009-08-31 13:32:46 -0500[diff] [blame]4451These macros are deprecated:
4452
4453 PNG_READ_TRANSFORMS_NOT_SUPPORTED
4454 PNG_PROGRESSIVE_READ_NOT_SUPPORTED
4455 PNG_NO_SEQUENTIAL_READ_SUPPORTED
4456 PNG_WRITE_TRANSFORMS_NOT_SUPPORTED
4457 PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED
4458 PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED
4459
4460They have been replaced, respectively, by:
4461
4462 PNG_NO_READ_TRANSFORMS
4463 PNG_NO_PROGRESSIVE_READ
4464 PNG_NO_SEQUENTIAL_READ
4465 PNG_NO_WRITE_TRANSFORMS
4466 PNG_NO_READ_ANCILLARY_CHUNKS
4467 PNG_NO_WRITE_ANCILLARY_CHUNKS
4468
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4469PNG_MAX_UINT was replaced with PNG_UINT_31_MAX. It has been
4470deprecated since libpng-1.0.16 and libpng-1.2.6.
4471
4472The function
4473 png_check_sig(sig, num)
4474was replaced with
4475 !png_sig_cmp(sig, 0, num)
4476It has been deprecated since libpng-0.90.
4477
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4478The function
4479 png_set_gray_1_2_4_to_8()
4480which also expands tRNS to alpha was replaced with
4481 png_set_expand_gray_1_2_4_to_8()
4482which does not. It has been deprecated since libpng-1.0.18 and 1.2.9.
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]4483
Glenn Randers-Pehrsond740c842009-11-04 19:01:54 -0600[diff] [blame]4484.SH IX. Changes to Libpng from version 1.0.x/1.2.x to 1.4.x
4485
4486Private libpng prototypes and macro definitions were moved from
4487png.h and pngconf.h into a new pngpriv.h header file.
4488
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4489Functions png_set_benign_errors(), png_benign_error(), and
4490png_chunk_benign_error() were added.
4491
4492Support for setting the maximum amount of memory that the application
4493will allocate for reading chunks was added, as a security measure.
4494The functions png_set_chunk_cache_max() and png_get_chunk_cache_max()
4495were added to the library.
4496
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]4497We implemented support for I/O states by adding png_ptr member io_state
4498and functions png_get_io_chunk_name() and png_get_io_state() in pngget.c
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4499
Glenn Randers-Pehrson5df7edb2009-10-29 23:32:44 -0500[diff] [blame]4500We added PNG_TRANSFORM_GRAY_TO_RGB to the available high-level
4501input transforms.
4502
Glenn Randers-Pehrson5df7edb2009-10-29 23:32:44 -0500[diff] [blame]4503Checking for and reporting of errors in the IHDR chunk is more thorough.
4504
Glenn Randers-Pehrson45af8192009-12-30 08:37:29 -0600[diff] [blame]4505Support for global arrays was removed, to improve thread safety.
4506
4507Some obsolete/deprecated macros and functions have been removed.
4508
4509Typecasted NULL definitions such as
4510 #define png_voidp_NULL (png_voidp)NULL
4511were eliminated. If you used these in your application, just use
4512NULL instead.
4513
4514The png_struct and info_struct members "trans" and "trans_values" were
4515changed to "trans_alpha" and "trans_color", respectively.
4516
4517The obsolete, unused pnggccrd.c and pngvcrd.c files and related makefiles
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]4518were removed.
Glenn Randers-Pehrson45af8192009-12-30 08:37:29 -0600[diff] [blame]4519
4520The PNG_1_0_X and PNG_1_2_X macros were eliminated.
4521
Glenn Randers-Pehrson5df7edb2009-10-29 23:32:44 -0500[diff] [blame]4522The PNG_LEGACY_SUPPORTED macro was eliminated.
4523
4524Many WIN32_WCE #ifdefs were removed.
4525
4526The functions png_read_init(info_ptr), png_write_init(info_ptr),
4527png_info_init(info_ptr), png_read_destroy(), and png_write_destroy()
4528have been removed. They have been deprecated since libpng-0.95.
4529
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4530The png_permit_empty_plte() was removed. It has been deprecated
4531since libpng-1.0.9. Use png_permit_mng_features() instead.
4532
4533We removed the obsolete stub functions png_get_mmx_flagmask(),
4534png_set_mmx_thresholds(), png_get_asm_flags(),
4535png_get_mmx_bitdepth_threshold(), png_get_mmx_rowbytes_threshold(),
4536png_set_asm_flags(), and png_mmx_supported()
4537
Glenn Randers-Pehrson45af8192009-12-30 08:37:29 -0600[diff] [blame]4538We removed the obsolete png_check_sig(), png_memcpy_check(), and
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]4539png_memset_check() functions. Instead use !png_sig_cmp(), memcpy(),
4540and memset(), respectively.
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4541
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]4542The function png_set_gray_1_2_4_to_8() was removed. It has been
4543deprecated since libpng-1.0.18 and 1.2.9, when it was replaced with
4544png_set_expand_gray_1_2_4_to_8() because the former function also
4545expanded palette images.
4546
Glenn Randers-Pehrson5b40b012010-11-25 07:16:29 -0600[diff] [blame]4547Macros for png_get_uint_16, png_get_uint_32, and png_get_int_32
4548were added and are used by default instead of the corresponding
4549functions. Unfortunately,
4550from libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the
4551function) incorrectly returned a value of type png_uint_32.
4552
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4553We changed the prototype for png_malloc() from
4554 png_malloc(png_structp png_ptr, png_uint_32 size)
4555to
4556 png_malloc(png_structp png_ptr, png_alloc_size_t size)
4557
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]4558This also applies to the prototype for the user replacement malloc_fn().
4559
Glenn Randers-Pehrson45af8192009-12-30 08:37:29 -0600[diff] [blame]4560The png_calloc() function was added and is used in place of
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]4561of "png_malloc(); memset();" except in the case in png_read_png()
Glenn Randers-Pehrson45af8192009-12-30 08:37:29 -0600[diff] [blame]4562where the array consists of pointers; in this case a "for" loop is used
4563after the png_malloc() to set the pointers to NULL, to give robust.
4564behavior in case the application runs out of memory part-way through
4565the process.
4566
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4567We changed the prototypes of png_get_compression_buffer_size() and
4568png_set_compression_buffer_size() to work with png_size_t instead of
4569png_uint_32.
4570
Glenn Randers-Pehrson45af8192009-12-30 08:37:29 -0600[diff] [blame]4571Support for numbered error messages was removed by default, since we
4572never got around to actually numbering the error messages. The function
4573png_set_strip_error_numbers() was removed from the library by default.
4574
4575The png_zalloc() and png_zfree() functions are no longer exported.
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4576The png_zalloc() function no longer zeroes out the memory that it
4577allocates.
4578
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]4579Support for dithering was disabled by default in libpng-1.4.0, because
4580been well tested and doesn't actually "dither". The code was not
4581removed, however, and could be enabled by building libpng with
4582PNG_READ_DITHER_SUPPORTED defined. In libpng-1.4.2, this support
4583was reenabled, but the function was renamed png_set_quantize() to
4584reflect more accurately what it actually does. At the same time,
4585the PNG_DITHER_[RED,GREEN_BLUE]_BITS macros were also renamed to
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4586PNG_QUANTIZE_[RED,GREEN,BLUE]_BITS, and PNG_READ_DITHER_SUPPORTED
4587was renamed to PNG_READ_QUANTIZE_SUPPORTED.
Glenn Randers-Pehrson60988072010-04-13 22:11:06 -0500[diff] [blame]4588
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4589We removed the trailing '.' from the warning and error messages.
4590
Glenn Randers-Pehrson5b40b012010-11-25 07:16:29 -0600[diff] [blame]4591.SH X. Changes to Libpng from version 1.4.x to 1.5.x
4592
4593From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the
4594function) incorrectly returned a value of type png_uint_32.
4595
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4596A. Changes that affect users of libpng
4597
4598There are no substantial API changes between the non-deprecated parts of
4599the 1.4.5 API and the 1.5.0 API, however the ability to directly access
4600the main libpng control structures, png_struct and png_info, deprecated
4601in earlier versions of libpng, has been completely removed from
4602libpng 1.5.
4603
Glenn Randers-Pehrson00879b12011-01-15 19:25:34 -0600[diff] [blame]4604We no longer include zlib.h in png.h. Applications that need access
4605to information in zlib.h will need to add the '#include "zlib.h"'
4606directive. It does not matter whether it is placed prior to or after
4607the '"#include png.h"' directive.
4608
4609We moved the png_strcpy(), png_strncpy(), png_strlen(), png_memcpy(),
4610png_memcmp(), png_sprintf, and png_memcpy() macros into a private
4611header file (pngpriv.h) that is not accessible to applications.
4612
Glenn Randers-Pehrson9d23b402011-01-08 10:42:01 -0600[diff] [blame]4613In png_get_iCCP, the type of "profile" was changed from png_charpp
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4614to png_bytepp, and in png_set_iCCP, from png_charp to png_const_bytep.
Glenn Randers-Pehrson9d23b402011-01-08 10:42:01 -0600[diff] [blame]4615
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4616There are changes of form in png.h, including new and changed macros to
4617declare
Glenn Randers-Pehrsonf5ea1b72011-01-06 06:42:51 -0600[diff] [blame]4618parts of the API. Some API functions with arguments that are pointers to
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4619data not modified within the function have been corrected to declare
4620these arguments with PNG_CONST.
4621
4622Much of the internal use of C macros to control the library build has also
4623changed and some of this is visible in the exported header files, in
4624particular the use of macros to control data and API elements visible
4625during application compilation may require significant revision to
4626application code. (It is extremely rare for an application to do this.)
4627
4628Any program that compiled against libpng 1.4 and did not use deprecated
4629features or access internal library structures should compile and work
4630against libpng 1.5.
4631
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]4632libpng 1.5.0 adds PNG_ PASS macros to help in the reading and writing of
4633interlaced images. The macros return the number of rows and columns in
4634each pass and information that can be used to de-interlace and (if
4635absolutely necessary) interlace an image.
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4636
4637libpng 1.5.0 adds an API png_longjmp(png_ptr, value). This API calls
4638the application provided png_longjmp_ptr on the internal, but application
4639initialized, jmpbuf. It is provided as a convenience to avoid the need
4640to use the png_jmpbuf macro, which had the unnecessary side effect of
4641resetting the internal png_longjmp_ptr value.
4642
4643libpng 1.5.0 includes a complete fixed point API. By default this is
4644present along with the corresponding floating point API. In general the
4645fixed point API is faster and smaller than the floating point one because
4646the PNG file format used fixed point, not floating point. This applies
4647even if the library uses floating point in internal calculations. A new
4648macro, PNG_FLOATING_ARITHMETIC_SUPPORTED, reveals whether the library
4649uses floating point arithmetic (the default) or fixed point arithmetic
4650internally for performance critical calculations such as gamma correction.
Glenn Randers-Pehrson00879b12011-01-15 19:25:34 -0600[diff] [blame]4651In some cases, the gamma calculations may produce slightly different
4652results. This has changed the results in png_rgb_to_gray and in alpha
4653composition (png_set_background for example). This applies even if the
4654original image was already linear (gamma == 1.0) and, therefore, it is
4655not necessary to linearize the image. This is because libpng has *not*
4656been changed to optimize that case correctly, yet.
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4657
4658Fixed point support for the sCAL chunk comes with an important caveat;
4659the sCAL specification uses a decimal encoding of floating point values
4660and the accuracy of PNG fixed point values is insufficient for
4661representation of these values. Consequently a "string" API
4662(png_get_sCAL_s and png_set_sCAL_s) is the only reliable way of reading
4663arbitrary sCAL chunks in the absence of either the floating point API or
4664internal floating point calculations.
4665
4666Applications no longer need to include the optional distribution header
4667file pngusr.h or define the corresponding macros during application
4668build in order to see the correct variant of the libpng API. From 1.5.0
4669application code can check for the corresponding _SUPPORTED macro:
4670
4671#ifdef PNG_INCH_CONVERSIONS_SUPPORTED
4672 /* code that uses the inch conversion APIs. */
4673#endif
4674
4675This macro will only be defined if the inch conversion functions have been
4676compiled into libpng. The full set of macros, and whether or not support
4677has been compiled in, are available in the header file pnglibconf.h.
4678This header file is specific to the libpng build. Notice that prior to
46791.5.0 the _SUPPORTED macros would always have the default definition unless
4680reset by pngusr.h or by explicit settings on the compiler command line.
4681These settings may produce compiler warnings or errors in 1.5.0 because
4682of macro redefinition.
4683
4684From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the
4685function) incorrectly returned a value of type png_uint_32. libpng 1.5.0
4686is consistent with the implementation in 1.4.5 and 1.2.x (where the macro
4687did not exist.)
4688
4689Applications can now choose whether to use these macros or to call the
4690corresponding function by defining PNG_USE_READ_MACROS or
4691PNG_NO_USE_READ_MACROS before including png.h. Notice that this is
4692only supported from 1.5.0 -defining PNG_NO_USE_READ_MACROS prior to 1.5.0
4693 will lead to a link failure.
Glenn Randers-Pehrson59fa3e92011-01-06 07:07:06 -0600[diff] [blame]4694
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4695B. Changes to the build and configuration of libpng
4696
4697Details of internal changes to the library code can be found in the CHANGES
4698file. These will be of no concern to the vast majority of library users or
4699builders, however the few who configure libpng to a non-default feature
4700set may need to change how this is done.
4701
4702There should be no need for library builders to alter build scripts if
4703these use the distributed build support - configure or the makefiles -
4704however users of the makefiles may care to update their build scripts
4705to build pnglibconf.h where the corresponding makefile does not do so.
4706
4707Building libpng with a non-default configuration has changed completely.
4708The old method using pngusr.h should still work correctly even though the
4709way pngusr.h is used in the build has been changed, however library
4710builders will probably want to examine the changes to take advantage of
4711new capabilities and to simplify their build system.
4712
4713B.1 Specific changes to library configuration capabilities
4714
4715The library now supports a complete fixed point implementation and can
4716thus be used on systems which have no floating point support or very
4717limited or slow support. Previously gamma correction, an essential part
4718of complete PNG support, required reasonably fast floating point.
4719
4720As part of this the choice of internal implementation has been made
4721independent of the choice of fixed versus floating point APIs and all the
4722missing fixed point APIs have been implemented.
4723
4724The exact mechanism used to control attributes of API functions has
4725changed. A single set of operating system independent macro definitions
4726is used and operating system specific directives are defined in
4727pnglibconf.h
4728
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4729As part of this the mechanism used to choose procedure call standards on
4730those systems that allow a choice has been changed. At present this only
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4731affects certain Microsoft (DOS, Windows) and IBM (OS/2) operating systems
4732running on Intel processors. As before PNGAPI is defined where required
4733to control the exported API functions; however, two new macros, PNGCBAPI
4734and PNGCAPI, are used instead for callback functions (PNGCBAPI) and
4735(PNGCAPI) for functions that must match a C library prototype (currently
4736only png_longjmp_ptr, which must match the C longjmp function.) The new
4737approach is documented in pngconf.h
4738
4739Despite these changes libpng 1.5.0 only supports the native C function
4740calling standard on those platforms tested so far (__cdecl on Microsoft
4741Windows). This is because the support requirements for alternative
4742calling conventions seem to no longer exist. Developers who find it
4743necessary to set PNG_API_RULE to 1 should advise the mailing list
4744(png-mng-implement) of this and library builders who use Openwatcom and
4745therefore set PNG_API_RULE to 2 should also contact the mailing list.
4746
4747A new test program, pngvalid, is provided in addition to pngtest.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4748pngvalid validates the arithmetic accuracy of the gamma correction
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4749calculations and includes a number of validations of the file format.
4750A subset of the full range of tests is run when "make check" is done
4751(in the 'configure' build.) pngvalid also allows total allocated memory
4752usage to be evaluated and performs additional memory overwrite validation.
4753
4754Many changes to individual feature macros have been made. The following
4755are the changes most likely to be noticed by library builders who
4756configure libpng:
4757
47581) All feature macros now have consistent naming:
4759
4760#define PNG_NO_feature turns the feature off
4761#define PNG_feature_SUPPORTED turns the feature on
4762
4763pnglibconf.h contains one line for each feature macro which is either:
4764
4765#define PNG_feature_SUPPORTED
4766
4767if the feature is supported or:
4768
4769/*#undef PNG_feature_SUPPORTED*/
4770
4771if it is not. Library code consistently checks for the 'SUPPORTED' macro.
4772It does not, and should not, check for the 'NO' macro which will not
4773normally be defined even if the feature is not supported.
4774
4775Compatibility with the old names is provided as follows:
4776
4777PNG_INCH_CONVERSIONS turns on PNG_INCH_CONVERSIONS_SUPPORTED
4778
4779And the following definitions disable the corresponding feature:
4780
4781PNG_SETJMP_NOT_SUPPORTED disables SETJMP
4782PNG_READ_TRANSFORMS_NOT_SUPPORTED disables READ_TRANSFORMS
4783PNG_NO_READ_COMPOSITED_NODIV disables READ_COMPOSITE_NODIV
4784PNG_WRITE_TRANSFORMS_NOT_SUPPORTED disables WRITE_TRANSFORMS
4785PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED disables READ_ANCILLARY_CHUNKS
4786PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED disables WRITE_ANCILLARY_CHUNKS
4787
4788Library builders should remove use of the above, inconsistent, names.
4789
47902) Warning and error message formatting was previously conditional on
4791the STDIO feature. The library has been changed to use the
4792CONSOLE_IO feature instead. This means that if CONSOLE_IO is disabled
4793the library no longer uses the printf(3) functions, even though the
4794default read/write implementations use (FILE) style stdio.h functions.
4795
47963) Three feature macros now control the fixed/floating point decisions:
4797
4798PNG_FLOATING_POINT_SUPPORTED enables the floating point APIs
4799
4800PNG_FIXED_POINT_SUPPORTED enables the fixed point APIs; however, in
4801practice these are normally required internally anyway (because the PNG
4802file format is fixed point), therefore in most cases PNG_NO_FIXED_POINT
4803merely stops the function from being exported.
4804
4805PNG_FLOATING_ARITHMETIC_SUPPORTED chooses between the internal floating
4806point implementation or the fixed point one. Typically the fixed point
4807implementation is larger and slower than the floating point implementation
4808on a system that supports floating point, however it may be faster on a
4809system which lacks floating point hardware and therefore uses a software
4810emulation.
4811
48124) Added PNG_{READ,WRITE}_INT_FUNCTIONS_SUPPORTED. This allows the
4813functions to read and write ints to be disabled independently of
4814PNG_USE_READ_MACROS, which allows libpng to be built with the functions
4815even though the default is to use the macros - this allows applications
4816to choose at app buildtime whether or not to use macros (previously
4817impossible because the functions weren't in the default build.)
4818
4819B.2 Changes to the configuration mechanism
4820
4821Prior to libpng-1.5.0 library builders who needed to configure libpng
4822had either to modify the exported pngconf.h header file to add system
4823specific configuration or had to write feature selection macros into
4824pngusr.h and cause this to be included into pngconf.h by defining
4825PNG_USER_CONFIG. The latter mechanism had the disadvantage that an
4826application built without PNG_USER_CONFIG defined would see the
4827unmodified, default, libpng API and thus would probably fail to link.
4828
4829These mechanisms still work in the configure build and in any makefile
4830build that builds pnglibconf.h although the feature selection macros
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4831have changed somewhat as described above. In 1.5.0, however, pngusr.h is
4832processed only once, when the exported header file pnglibconf.h is built.
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4833pngconf.h no longer includes pngusr.h, therefore it is ignored after the
4834build of pnglibconf.h and it is never included in an application build.
4835
4836The rarely used alternative of adding a list of feature macros to the
4837CFLAGS setting in the build also still works, however the macros will be
4838copied to pnglibconf.h and this may produce macro redefinition warnings
4839when the individual C files are compiled.
4840
4841All configuration now only works if pnglibconf.h is built from
4842scripts/pnglibconf.dfa. This requires the program awk. Brian Kernighan
4843(the original author of awk) maintains C source code of that awk and this
4844and all known later implementations (often called by subtly different
4845names - nawk and gawk for example) are adequate to build pnglibconf.h.
4846The Sun Microsystems (now Oracle) program 'awk' is an earlier version
4847and does not work, this may also apply to other systems that have a
4848functioning awk called 'nawk'.
4849
4850Configuration options are now documented in scripts/pnglibconf.dfa. This
4851file also includes dependency information that ensures a configuration is
4852consistent; that is, if a feature is switched off dependent features are
4853also removed. As a recommended alternative to using feature macros in
4854pngusr.h a system builder may also define equivalent options in pngusr.dfa
4855(or, indeed, any file) and add that to the configuration by setting
4856DFA_XTRA to the file name. The makefiles in contrib/pngminim illustrate
4857how to do this, and a case where pngusr.h is still required.
4858
Glenn Randers-Pehrson5b40b012010-11-25 07:16:29 -0600[diff] [blame]4859.SH XI. Detecting libpng
Glenn Randers-Pehrson424c9852009-06-02 13:45:15 -0500[diff] [blame]4860
4861The png_get_io_ptr() function has been present since libpng-0.88, has never
4862changed, and is unaffected by conditional compilation macros. It is the
4863best choice for use in configure scripts for detecting the presence of any
Glenn Randers-Pehrson99708d52009-06-29 17:30:00 -0500[diff] [blame]4864libpng version since 0.88. In an autoconf "configure.in" you could use
4865
4866 AC_CHECK_LIB(png, png_get_io_ptr, ...
Glenn Randers-Pehrson424c9852009-06-02 13:45:15 -0500[diff] [blame]4867
Glenn Randers-Pehrson5b40b012010-11-25 07:16:29 -0600[diff] [blame]4868.SH XII. Source code repository
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4869
4870Since about February 2009, version 1.2.34, libpng has been under "git" source
4871control. The git repository was built from old libpng-x.y.z.tar.gz files
4872going back to version 0.70. You can access the git repository (read only)
4873at
4874
4875 git://libpng.git.sourceforge.net/gitroot/libpng
4876
4877or you can browse it via "gitweb" at
4878
4879 http://libpng.git.sourceforge.net/git/gitweb.cgi?p=libpng
4880
4881Patches can be sent to glennrp at users.sourceforge.net or to
4882png-mng-implement at lists.sourceforge.net or you can upload them to
4883the libpng bug tracker at
4884
4885 http://libpng.sourceforge.net
4886
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4887We also accept patches built from the tar or zip distributions, and
4888simple verbal discriptions of bug fixes, reported either to the
4889SourceForge bug tracker or to the png-mng-implement at lists.sf.net
4890mailing list.
4891
Glenn Randers-Pehrson5b40b012010-11-25 07:16:29 -0600[diff] [blame]4892.SH XIII. Coding style
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4893
4894Our coding style is similar to the "Allman" style, with curly
4895braces on separate lines:
4896
4897 if (condition)
4898 {
4899 action;
4900 }
4901
4902 else if (another condition)
4903 {
4904 another action;
4905 }
4906
4907The braces can be omitted from simple one-line actions:
4908
4909 if (condition)
4910 return (0);
4911
4912We use 3-space indentation, except for continued statements which
4913are usually indented the same as the first line of the statement
4914plus four more spaces.
4915
Glenn Randers-Pehrson5ade7ed2009-09-30 15:11:49 -0500[diff] [blame]4916For macro definitions we use 2-space indentation, always leaving the "#"
4917in the first column.
4918
4919 #ifndef PNG_NO_FEATURE
4920 # ifndef PNG_FEATURE_SUPPORTED
4921 # define PNG_FEATURE_SUPPORTED
4922 # endif
4923 #endif
4924
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4925Comments appear with the leading "/*" at the same indentation as
4926the statement that follows the comment:
4927
4928 /* Single-line comment */
4929 statement;
4930
Glenn Randers-Pehrsone4c706a2010-03-06 14:51:54 -0600[diff] [blame]4931 /* This is a multiple-line
4932 * comment.
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4933 */
4934 statement;
4935
Glenn Randers-Pehrsone4c706a2010-03-06 14:51:54 -0600[diff] [blame]4936Very short comments can be placed after the end of the statement
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4937to which they pertain:
4938
4939 statement; /* comment */
4940
4941We don't use C++ style ("//") comments. We have, however,
4942used them in the past in some now-abandoned MMX assembler
4943code.
4944
Glenn Randers-Pehrsonb5444a12009-06-08 08:36:19 -0500[diff] [blame]4945Functions and their curly braces are not indented, and
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4946exported functions are marked with PNGAPI:
4947
4948 /* This is a public function that is visible to
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4949 * application programmers. It does thus-and-so.
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4950 */
4951 void PNGAPI
4952 png_exported_function(png_ptr, png_info, foo)
4953 {
4954 body;
4955 }
4956
Glenn Randers-Pehrson416976f2009-07-27 22:16:09 -0500[diff] [blame]4957The prototypes for all exported functions appear in png.h,
4958above the comment that says
4959
4960 /* Maintainer: Put new public prototypes here ... */
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4961
4962We mark all non-exported functions with "/* PRIVATE */"":
4963
4964 void /* PRIVATE */
4965 png_non_exported_function(png_ptr, png_info, foo)
4966 {
4967 body;
4968 }
4969
Glenn Randers-Pehrson416976f2009-07-27 22:16:09 -0500[diff] [blame]4970The prototypes for non-exported functions (except for those in
Glenn Randers-Pehrson5df7edb2009-10-29 23:32:44 -0500[diff] [blame]4971pngtest) appear in
4972pngpriv.h
Glenn Randers-Pehrson416976f2009-07-27 22:16:09 -0500[diff] [blame]4973above the comment that says
4974
4975 /* Maintainer: Put new private prototypes here ^ and in libpngpf.3 */
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4976
4977The names of all exported functions and variables begin
4978with "png_", and all publicly visible C preprocessor
4979macros begin with "PNG_".
4980
4981We put a space after each comma and after each semicolon
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4982in "for" statements, and we put spaces before and after each
Glenn Randers-Pehrsone4c706a2010-03-06 14:51:54 -0600[diff] [blame]4983C binary operator and after "for" or "while", and before
4984"?". We don't put a space between a typecast and the expression
4985being cast, nor do we put one between a function name and the
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4986left parenthesis that follows it:
4987
4988 for (i = 2; i > 0; --i)
Glenn Randers-Pehrson67f3b482009-09-23 11:36:28 -0500[diff] [blame]4989 y[i] = a(x) + (int)b;
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4990
Glenn Randers-Pehrsond60c8862009-06-15 21:56:14 -0500[diff] [blame]4991We prefer #ifdef and #ifndef to #if defined() and if !defined()
4992when there is only one macro being tested.
4993
Glenn Randers-Pehrson67f3b482009-09-23 11:36:28 -0500[diff] [blame]4994We do not use the TAB character for indentation in the C sources.
4995
Glenn Randers-Pehrson62ca98e2009-12-20 15:14:57 -0600[diff] [blame]4996Lines do not exceed 80 characters.
4997
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]4998Other rules can be inferred by inspecting the libpng source.
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4999
Glenn Randers-Pehrson5b40b012010-11-25 07:16:29 -0600[diff] [blame]5000.SH XIV. Y2K Compliance in libpng
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5001
Glenn Randers-Pehrson0012e9c2011-01-26 22:04:03 -0600[diff] [blame]5002January 27, 2011
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5003
5004Since the PNG Development group is an ad-hoc body, we can't make
5005an official declaration.
5006
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]5007This is your unofficial assurance that libpng from version 0.71 and
Glenn Randers-Pehrson135d17c2011-01-24 00:16:54 -0600[diff] [blame]5008upward through 1.5.1beta10 are Y2K compliant. It is my belief that earlier
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]5009versions were also Y2K compliant.
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5010
5011Libpng only has three year fields. One is a 2-byte unsigned integer that
5012will hold years up to 65535. The other two hold the date in text
5013format, and will hold years up to 9999.
5014
5015The integer is
5016 "png_uint_16 year" in png_time_struct.
5017
5018The strings are
5019 "png_charp time_buffer" in png_struct and
5020 "near_time_buffer", which is a local character string in png.c.
5021
5022There are seven time-related functions:
5023
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]5024 png_convert_to_rfc_1123() in png.c
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5025 (formerly png_convert_to_rfc_1152() in error)
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]5026 png_convert_from_struct_tm() in pngwrite.c, called
5027 in pngwrite.c
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5028 png_convert_from_time_t() in pngwrite.c
5029 png_get_tIME() in pngget.c
5030 png_handle_tIME() in pngrutil.c, called in pngread.c
5031 png_set_tIME() in pngset.c
5032 png_write_tIME() in pngwutil.c, called in pngwrite.c
5033
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]5034All appear to handle dates properly in a Y2K environment. The
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5035png_convert_from_time_t() function calls gmtime() to convert from system
5036clock time, which returns (year - 1900), which we properly convert to
5037the full 4-digit year. There is a possibility that applications using
5038libpng are not passing 4-digit years into the png_convert_to_rfc_1123()
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]5039function, or that they are incorrectly passing only a 2-digit year
5040instead of "year - 1900" into the png_convert_from_struct_tm() function,
5041but this is not under our control. The libpng documentation has always
5042stated that it works with 4-digit years, and the APIs have been
5043documented as such.
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5044
5045The tIME chunk itself is also Y2K compliant. It uses a 2-byte unsigned
5046integer to hold the year, and can hold years as large as 65535.
5047
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]5048zlib, upon which libpng depends, is also Y2K compliant. It contains
5049no date-related code.
5050
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5051
5052 Glenn Randers-Pehrson
5053 libpng maintainer
5054 PNG Development Group
5055
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5056.SH NOTE
5057
5058Note about libpng version numbers:
5059
5060Due to various miscommunications, unforeseen code incompatibilities
5061and occasional factors outside the authors' control, version numbering
5062on the library has not always been consistent and straightforward.
5063The following table summarizes matters since version 0.89c, which was
5064the first widely used release:
5065
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]5066 source png.h png.h shared-lib
5067 version string int version
5068 ------- ------ ----- ----------
5069 0.89c ("beta 3") 0.89 89 1.0.89
5070 0.90 ("beta 4") 0.90 90 0.90
5071 0.95 ("beta 5") 0.95 95 0.95
5072 0.96 ("beta 6") 0.96 96 0.96
5073 0.97b ("beta 7") 1.00.97 97 1.0.1
5074 0.97c 0.97 97 2.0.97
5075 0.98 0.98 98 2.0.98
5076 0.99 0.99 98 2.0.99
5077 0.99a-m 0.99 99 2.0.99
5078 1.00 1.00 100 2.1.0
5079 1.0.0 1.0.0 100 2.1.0
5080 1.0.0 (from here on, the 100 2.1.0
5081 1.0.1 png.h string is 10001 2.1.0
5082 1.0.1a-e identical to the 10002 from here on, the
5083 1.0.2 source version) 10002 shared library is 2.V
5084 1.0.2a-b 10003 where V is the source
5085 1.0.1 10001 code version except as
5086 1.0.1a-e 10002 2.1.0.1a-e noted.
5087 1.0.2 10002 2.1.0.2
5088 1.0.2a-b 10003 2.1.0.2a-b
5089 1.0.3 10003 2.1.0.3
5090 1.0.3a-d 10004 2.1.0.3a-d
5091 1.0.4 10004 2.1.0.4
5092 1.0.4a-f 10005 2.1.0.4a-f
5093 1.0.5 (+ 2 patches) 10005 2.1.0.5
5094 1.0.5a-d 10006 2.1.0.5a-d
5095 1.0.5e-r 10100 2.1.0.5e-r
5096 1.0.5s-v 10006 2.1.0.5s-v
5097 1.0.6 (+ 3 patches) 10006 2.1.0.6
5098 1.0.6d-g 10007 2.1.0.6d-g
5099 1.0.6h 10007 10.6h
5100 1.0.6i 10007 10.6i
5101 1.0.6j 10007 2.1.0.6j
Glenn Randers-Pehrson27742382011-01-27 09:37:34 -0600[diff] [blame^]5102 1.0.7beta10-14 DLLNUM 10007 2.1.0.7beta10-14
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]5103 1.0.7beta15-18 1 10007 2.1.0.7beta15-18
5104 1.0.7rc1-2 1 10007 2.1.0.7rc1-2
5105 1.0.7 1 10007 2.1.0.7
5106 1.0.8beta1-4 1 10008 2.1.0.8beta1-4
5107 1.0.8rc1 1 10008 2.1.0.8rc1
5108 1.0.8 1 10008 2.1.0.8
5109 1.0.9beta1-6 1 10009 2.1.0.9beta1-6
5110 1.0.9rc1 1 10009 2.1.0.9rc1
5111 1.0.9beta7-10 1 10009 2.1.0.9beta7-10
5112 1.0.9rc2 1 10009 2.1.0.9rc2
5113 1.0.9 1 10009 2.1.0.9
Glenn Randers-Pehrsone1644472001-03-23 05:06:56 -0600[diff] [blame]5114 1.0.10beta1 1 10010 2.1.0.10beta1
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]5115 1.0.10rc1 1 10010 2.1.0.10rc1
Glenn Randers-Pehrson13cfbac2001-03-30 06:42:28 -0600[diff] [blame]5116 1.0.10 1 10010 2.1.0.10
Glenn Randers-Pehrsone1eff582001-04-14 20:15:41 -0500[diff] [blame]5117 1.0.11beta1-3 1 10011 2.1.0.11beta1-3
Glenn Randers-Pehrson82ae3832001-04-20 10:32:10 -0500[diff] [blame]5118 1.0.11rc1 1 10011 2.1.0.11rc1
Glenn Randers-Pehrson32835392001-04-27 08:29:32 -0500[diff] [blame]5119 1.0.11 1 10011 2.1.0.11
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame]5120 1.0.12beta1-2 2 10012 2.1.0.12beta1-2
5121 1.0.12rc1 2 10012 2.1.0.12rc1
5122 1.0.12 2 10012 2.1.0.12
5123 1.1.0a-f - 10100 2.1.1.0a-f abandoned
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]5124 1.2.0beta1-2 2 10200 2.1.2.0beta1-2
Glenn Randers-Pehrson5a0be342001-10-18 20:55:13 -0500[diff] [blame]5125 1.2.0beta3-5 3 10200 3.1.2.0beta3-5
5126 1.2.0rc1 3 10200 3.1.2.0rc1
5127 1.2.0 3 10200 3.1.2.0
Glenn Randers-Pehrson5cded0b2001-11-07 07:10:08 -0600[diff] [blame]5128 1.2.1beta-4 3 10201 3.1.2.1beta1-4
Glenn Randers-Pehrsondb3b88d2001-12-04 06:30:43 -0600[diff] [blame]5129 1.2.1rc1-2 3 10201 3.1.2.1rc1-2
5130 1.2.1 3 10201 3.1.2.1
Glenn Randers-Pehrson25228ab2002-03-31 07:33:55 -0600[diff] [blame]5131 1.2.2beta1-6 12 10202 12.so.0.1.2.2beta1-6
Glenn Randers-Pehrsonfcbd7872002-04-07 16:35:38 -0500[diff] [blame]5132 1.0.13beta1 10 10013 10.so.0.1.0.13beta1
5133 1.0.13rc1 10 10013 10.so.0.1.0.13rc1
5134 1.2.2rc1 12 10202 12.so.0.1.2.2rc1
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]5135 1.0.13 10 10013 10.so.0.1.0.13
5136 1.2.2 12 10202 12.so.0.1.2.2
Glenn Randers-Pehrson22f28962002-05-13 18:17:09 -0500[diff] [blame]5137 1.2.3rc1-6 12 10203 12.so.0.1.2.3rc1-6
5138 1.2.3 12 10203 12.so.0.1.2.3
Glenn Randers-Pehrsond020e9d2002-06-28 09:34:00 -0500[diff] [blame]5139 1.2.4beta1-3 13 10204 12.so.0.1.2.4beta1-3
Glenn Randers-Pehrson2ae022d2002-07-01 22:23:46 -0500[diff] [blame]5140 1.2.4rc1 13 10204 12.so.0.1.2.4rc1
Glenn Randers-Pehrson484a8a12002-07-07 19:15:20 -0500[diff] [blame]5141 1.0.14 10 10014 10.so.0.1.0.14
5142 1.2.4 13 10204 12.so.0.1.2.4
Glenn Randers-Pehrson5b5dcf82004-07-17 22:45:44 -0500[diff] [blame]5143 1.2.5beta1-2 13 10205 12.so.0.1.2.5beta1-2
5144 1.0.15rc1 10 10015 10.so.0.1.0.15rc1
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]5145 1.0.15 10 10015 10.so.0.1.0.15
5146 1.2.5 13 10205 12.so.0.1.2.5
5147 1.2.6beta1-4 13 10206 12.so.0.1.2.6beta1-4
Glenn Randers-Pehrson37f116a2004-08-15 07:15:39 -0500[diff] [blame]5148 1.2.6rc1-5 13 10206 12.so.0.1.2.6rc1-5
5149 1.0.16 10 10016 10.so.0.1.0.16
5150 1.2.6 13 10206 12.so.0.1.2.6
Glenn Randers-Pehrson67864af2004-08-28 23:30:07 -0500[diff] [blame]5151 1.2.7beta1-2 13 10207 12.so.0.1.2.7beta1-2
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]5152 1.0.17rc1 10 10017 12.so.0.1.0.17rc1
5153 1.2.7rc1 13 10207 12.so.0.1.2.7rc1
Glenn Randers-Pehrson250dfe12004-09-11 21:19:54 -0500[diff] [blame]5154 1.0.17 10 10017 12.so.0.1.0.17
5155 1.2.7 13 10207 12.so.0.1.2.7
Glenn Randers-Pehrson40936072004-11-20 11:18:40 -0600[diff] [blame]5156 1.2.8beta1-5 13 10208 12.so.0.1.2.8beta1-5
Glenn Randers-Pehrson584b96e2004-11-29 15:08:00 -0600[diff] [blame]5157 1.0.18rc1-5 10 10018 12.so.0.1.0.18rc1-5
5158 1.2.8rc1-5 13 10208 12.so.0.1.2.8rc1-5
Glenn Randers-Pehrson917648e2004-12-02 18:14:51 -0600[diff] [blame]5159 1.0.18 10 10018 12.so.0.1.0.18
5160 1.2.8 13 10208 12.so.0.1.2.8
Glenn Randers-Pehrsone6474622006-03-04 16:50:47 -0600[diff] [blame]5161 1.2.9beta1-3 13 10209 12.so.0.1.2.9beta1-3
Glenn Randers-Pehrson4deeb792006-03-22 16:21:59 -0600[diff] [blame]5162 1.2.9beta4-11 13 10209 12.so.0.9[.0]
Glenn Randers-Pehrson3a512032006-03-31 05:29:33 -0600[diff] [blame]5163 1.2.9rc1 13 10209 12.so.0.9[.0]
Glenn Randers-Pehrsona7d0c942006-04-14 06:22:52 -0500[diff] [blame]5164 1.2.9 13 10209 12.so.0.9[.0]
Glenn Randers-Pehrsond60b8fa2006-04-20 21:31:14 -0500[diff] [blame]5165 1.2.10beta1-7 13 10210 12.so.0.10[.0]
Glenn Randers-Pehrson17218292006-04-20 07:20:46 -0500[diff] [blame]5166 1.2.10rc1-2 13 10210 12.so.0.10[.0]
Glenn Randers-Pehrson86dc9812006-05-10 07:27:44 -0500[diff] [blame]5167 1.2.10 13 10210 12.so.0.10[.0]
Glenn Randers-Pehrson6bc53be2006-06-16 07:52:03 -0500[diff] [blame]5168 1.4.0beta1-6 14 10400 14.so.0.0[.0]
Glenn Randers-Pehrsond60c8862009-06-15 21:56:14 -0500[diff] [blame]5169 1.2.11beta1-4 13 10210 12.so.0.11[.0]
Glenn Randers-Pehrson3424ee72006-07-12 13:33:47 -0500[diff] [blame]5170 1.4.0beta7-8 14 10400 14.so.0.0[.0]
Glenn Randers-Pehrson701dbaa2006-11-17 09:36:54 -0600[diff] [blame]5171 1.2.11 13 10211 12.so.0.11[.0]
5172 1.2.12 13 10212 12.so.0.12[.0]
5173 1.4.0beta9-14 14 10400 14.so.0.0[.0]
5174 1.2.13 13 10213 12.so.0.13[.0]
Glenn Randers-Pehrson97a9b482008-10-25 20:03:28 -0500[diff] [blame]5175 1.4.0beta15-36 14 10400 14.so.0.0[.0]
Glenn Randers-Pehrsonfa028102009-10-10 06:15:21 -0500[diff] [blame]5176 1.4.0beta37-87 14 10400 14.so.14.0[.0]
Glenn Randers-Pehrson733da8c2009-10-30 00:00:15 -0500[diff] [blame]5177 1.4.0rc01 14 10400 14.so.14.0[.0]
Glenn Randers-Pehrson62ca98e2009-12-20 15:14:57 -0600[diff] [blame]5178 1.4.0beta88-109 14 10400 14.so.14.0[.0]
Glenn Randers-Pehrson67a83db2010-01-01 18:26:18 -0600[diff] [blame]5179 1.4.0rc02-08 14 10400 14.so.14.0[.0]
Glenn Randers-Pehrsondbcfb712009-12-25 14:24:18 -0600[diff] [blame]5180 1.4.0 14 10400 14.so.14.0[.0]
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]5181 1.4.1beta01-03 14 10401 14.so.14.1[.0]
5182 1.4.1rc01 14 10401 14.so.14.1[.0]
Glenn Randers-Pehrson7a5be532010-02-14 07:16:19 -0600[diff] [blame]5183 1.4.1beta04-12 14 10401 14.so.14.1[.0]
Glenn Randers-Pehrsonaaf377c2010-03-08 11:20:30 -0600[diff] [blame]5184 1.4.1 14 10401 14.so.14.1[.0]
Glenn Randers-Pehrson5b3d5542010-06-18 21:55:53 -0500[diff] [blame]5185 1.4.2 14 10402 14.so.14.2[.0]
5186 1.4.3 14 10403 14.so.14.3[.0]
Glenn Randers-Pehrson2776d5e2010-11-21 15:18:02 -0600[diff] [blame]5187 1.4.4 14 10404 14.so.14.4[.0]
Glenn Randers-Pehrsonfd20a5a2010-12-27 08:53:08 -0600[diff] [blame]5188 1.5.0beta01-58 15 10500 15.so.15.0[.0]
Glenn Randers-Pehrson64b863c2011-01-04 09:57:06 -0600[diff] [blame]5189 1.5.0rc01-07 15 10500 15.so.15.0[.0]
Glenn Randers-Pehrsonf5ea1b72011-01-06 06:42:51 -0600[diff] [blame]5190 1.5.0 15 10500 15.so.15.0[.0]
Glenn Randers-Pehrson27742382011-01-27 09:37:34 -0600[diff] [blame^]5191 1.5.1rc01 15 10501 15.so.15.1[.0]
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5192
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]5193Henceforth the source version will match the shared-library minor
5194and patch numbers; the shared-library major version number will be
5195used for changes in backward compatibility, as it is intended. The
5196PNG_PNGLIB_VER macro, which is not used within libpng but is available
5197for applications, is an unsigned integer of the form xyyzz corresponding
5198to the source version x.y.z (leading zeros in y and z). Beta versions
Glenn Randers-Pehrsone1644472001-03-23 05:06:56 -0600[diff] [blame]5199were given the previous public release number plus a letter, until
5200version 1.0.6j; from then on they were given the upcoming public
5201release number plus "betaNN" or "rcN".
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]5202
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5203.SH "SEE ALSO"
Glenn Randers-Pehrson4e763f12010-03-03 10:45:50 -0600[diff] [blame]5204.BR "png"(5), " libpngpf"(3), " zlib"(3), " deflate"(5), " " and " zlib"(5)
Glenn Randers-Pehrson7fb32a82010-03-03 09:47:49 -0600[diff] [blame]5205
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]5206.LP
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5207.IR libpng :
5208.IP
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]5209http://libpng.sourceforge.net (follow the [DOWNLOAD] link)
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]5210http://www.libpng.org/pub/png
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5211
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]5212.LP
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5213.IR zlib :
5214.IP
5215(generally) at the same location as
5216.I libpng
5217or at
5218.br
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]5219ftp://ftp.info-zip.org/pub/infozip/zlib
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5220
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]5221.LP
5222.IR PNG specification: RFC 2083
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5223.IP
5224(generally) at the same location as
5225.I libpng
5226or at
5227.br
5228ftp://ds.internic.net/rfc/rfc2083.txt
5229.br
5230or (as a W3C Recommendation) at
5231.br
5232http://www.w3.org/TR/REC-png.html
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5233
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]5234.LP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5235In the case of any inconsistency between the PNG specification
5236and this library, the specification takes precedence.
5237
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5238.SH AUTHORS
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5239This man page: Glenn Randers-Pehrson
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]5240<glennrp at users.sourceforge.net>
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5241
5242The contributing authors would like to thank all those who helped
5243with testing, bug fixes, and patience. This wouldn't have been
5244possible without all of you.
5245
5246Thanks to Frank J. T. Wojcik for helping with the documentation.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]5247
Glenn Randers-Pehrson0012e9c2011-01-26 22:04:03 -0600[diff] [blame]5248Libpng version 1.5.1beta10 - January 27, 2011:
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5249Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]5250Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5251
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5252Supported by the PNG development group
5253.br
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]5254png-mng-implement at lists.sf.net
5255(subscription required; visit
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]5256png-mng-implement at lists.sourceforge.net (subscription required; visit
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]5257https://lists.sourceforge.net/lists/listinfo/png-mng-implement
5258to subscribe).
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5259
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5260.SH COPYRIGHT NOTICE, DISCLAIMER, and LICENSE:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5261
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]5262(This copy of the libpng notices is provided for your convenience. In case of
5263any discrepancy between this copy and the notices in the file png.h that is
5264included in the libpng distribution, the latter shall prevail.)
5265
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5266If you modify libpng you may insert additional notices immediately following
5267this sentence.
5268
Glenn Randers-Pehrsonbfbf8652009-06-26 21:46:52 -0500[diff] [blame]5269This code is released under the libpng license.
Glenn Randers-Pehrson037023b2009-06-24 10:27:36 -0500[diff] [blame]5270
Glenn Randers-Pehrson0012e9c2011-01-26 22:04:03 -0600[diff] [blame]5271libpng versions 1.2.6, August 15, 2004, through 1.5.1beta10, January 27, 2011, are
Glenn Randers-Pehrsona7dbcba2007-05-15 16:16:34 -0500[diff] [blame]5272Copyright (c) 2004,2006-2007 Glenn Randers-Pehrson, and are
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]5273distributed according to the same disclaimer and license as libpng-1.2.5
Glenn Randers-Pehrsond029a752004-08-09 21:50:32 -0500[diff] [blame]5274with the following individual added to the list of Contributing Authors
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]5275
5276 Cosmin Truta
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]5277
5278libpng versions 1.0.7, July 1, 2000, through 1.2.5 - October 3, 2002, are
Glenn Randers-Pehrsonc6de22d2002-02-23 18:55:25 -0600[diff] [blame]5279Copyright (c) 2000-2002 Glenn Randers-Pehrson, and are
Glenn Randers-Pehrson32fc5ce2000-07-24 06:34:14 -0500[diff] [blame]5280distributed according to the same disclaimer and license as libpng-1.0.6
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5281with the following individuals added to the list of Contributing Authors
5282
5283 Simon-Pierre Cadieux
5284 Eric S. Raymond
5285 Gilles Vollant
5286
5287and with the following additions to the disclaimer:
5288
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]5289 There is no warranty against interference with your
5290 enjoyment of the library or against infringement.
5291 There is no warranty that our efforts or the library
5292 will fulfill any of your particular purposes or needs.
5293 This library is provided with all faults, and the entire
5294 risk of satisfactory quality, performance, accuracy, and
5295 effort is with the user.
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5296
5297libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
5298Copyright (c) 1998, 1999 Glenn Randers-Pehrson
5299Distributed according to the same disclaimer and license as libpng-0.96,
5300with the following individuals added to the list of Contributing Authors:
5301
5302 Tom Lane
5303 Glenn Randers-Pehrson
5304 Willem van Schaik
5305
5306libpng versions 0.89, June 1996, through 0.96, May 1997, are
Glenn Randers-Pehrson54a066a1999-09-19 06:04:18 -0500[diff] [blame]5307Copyright (c) 1996, 1997 Andreas Dilger
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5308Distributed according to the same disclaimer and license as libpng-0.88,
5309with the following individuals added to the list of Contributing Authors:
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]5310
5311 John Bowler
5312 Kevin Bracey
5313 Sam Bushell
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]5314 Magnus Holmgren
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]5315 Greg Roelofs
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5316 Tom Tanner
5317
5318libpng versions 0.5, May 1995, through 0.88, January 1996, are
5319Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
5320
5321For the purposes of this copyright and license, "Contributing Authors"
5322is defined as the following set of individuals:
5323
5324 Andreas Dilger
5325 Dave Martindale
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]5326 Guy Eric Schalnat
5327 Paul Schmidt
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]5328 Tim Wegner
Glenn Randers-Pehrsonc9442291999-01-06 21:50:16 -0600[diff] [blame]5329
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5330The PNG Reference Library is supplied "AS IS". The Contributing Authors
5331and Group 42, Inc. disclaim all warranties, expressed or implied,
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5332including, without limitation, the warranties of merchantability and of
5333fitness for any purpose. The Contributing Authors and Group 42, Inc.
5334assume no liability for direct, indirect, incidental, special, exemplary,
5335or consequential damages, which may result from the use of the PNG
5336Reference Library, even if advised of the possibility of such damage.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5337
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5338Permission is hereby granted to use, copy, modify, and distribute this
5339source code, or portions hereof, for any purpose, without fee, subject
5340to the following restrictions:
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5341
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]53421. The origin of this source code must not be misrepresented.
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5343
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]53442. Altered versions must be plainly marked as such and
5345 must not be misrepresented as being the original source.
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5346
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]53473. This Copyright notice may not be removed or altered from
5348 any source or altered source distribution.
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5349
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5350The Contributing Authors and Group 42, Inc. specifically permit, without
5351fee, and encourage the use of this source code as a component to
5352supporting the PNG file format in commercial products. If you use this
5353source code in a product, acknowledgment is not required but would be
5354appreciated.
5355
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5356
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]5357A "png_get_copyright" function is available, for convenient use in "about"
5358boxes and the like:
5359
5360 printf("%s",png_get_copyright(NULL));
5361
5362Also, the PNG logo (in PNG format, of course) is supplied in the
Glenn Randers-Pehrsona4d54bd2000-07-14 08:15:12 -0500[diff] [blame]5363files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31).
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]5364
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5365Libpng is OSI Certified Open Source Software. OSI Certified Open Source is a
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]5366certification mark of the Open Source Initiative.
5367
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5368Glenn Randers-Pehrson
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]5369glennrp at users.sourceforge.net
Glenn Randers-Pehrson0012e9c2011-01-26 22:04:03 -0600[diff] [blame]5370January 27, 2011
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5371
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5372.\" end of man page
5373