Gitiles
Code Review Sign In
gerrit-public.fairphone.software / platform / external / libpng / 895a9c97e2ea19b51bcfd6f26d2f51ab31041b12 / . / libpng.3
blob: 560be063f9f83ba0741a3c058fdb5f6b9adbb0f7 [file] [log] [blame]
Glenn Randers-Pehrson895a9c92008-07-25 08:51:18 -0500[diff] [blame^]1.TH LIBPNG 3 "July 25, 2008"
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]2.SH NAME
Glenn Randers-Pehrson895a9c92008-07-25 08:51:18 -0500[diff] [blame^]3libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0beta24
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4.SH SYNOPSIS
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]5\fI\fB
6
7\fB#include <png.h>\fP
8
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
12
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]13\fI\fB
14
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
16
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]17\fI\fB
18
Glenn Randers-Pehrson6bc53be2006-06-16 07:52:03 -0500[diff] [blame]19\fBvoid png_chunk_benign_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP
20
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]21\fI\fB
22
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]23\fBint png_check_sig (png_bytep \fP\fIsig\fP\fB, int \fInum\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]24
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]25\fI\fB
26
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]27\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]28
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]29\fI\fB
30
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]31\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]32
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]33\fI\fB
34
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]35\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]36
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]37\fI\fB
38
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]39\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]40
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]41\fI\fB
42
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]43\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]44
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]45\fI\fB
46
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]47\fBpng_infop png_create_info_struct (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]48
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]49\fI\fB
50
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]51\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]52
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]53\fI\fB
54
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]55\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
56
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]57\fI\fB
58
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]59\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]60
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]61\fI\fB
62
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]63\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
64
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]65\fI\fB
66
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]67\fBint png_debug(int \fP\fIlevel\fP\fB, png_const_charp \fImessage\fP\fB);\fP
68
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]69\fI\fB
70
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]71\fBint png_debug1(int \fP\fIlevel\fP\fB, png_const_charp \fP\fImessage\fP\fB, \fIp1\fP\fB);\fP
72
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]73\fI\fB
74
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]75\fBint png_debug2(int \fP\fIlevel\fP\fB, png_const_charp \fP\fImessage\fP\fB, \fP\fIp1\fP\fB, \fIp2\fP\fB);\fP
76
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]77\fI\fB
78
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]79\fBvoid png_destroy_info_struct (png_structp \fP\fIpng_ptr\fP\fB, png_infopp \fIinfo_ptr_ptr\fP\fB);\fP
80
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]81\fI\fB
82
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]83\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
84
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]85\fI\fB
86
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]87\fBvoid png_destroy_write_struct (png_structpp \fP\fIpng_ptr_ptr\fP\fB, png_infopp \fIinfo_ptr_ptr\fP\fB);\fP
88
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]89\fI\fB
90
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
92
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]93\fI\fB
94
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
96
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -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
100
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]101\fI\fB
102
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]103\fBvoid png_free_default(png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP
104
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -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-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]109\fI\fB
110
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]111\fBpng_byte png_get_bit_depth (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
112
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]113\fI\fB
114
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]115\fBpng_uint_32 png_get_bKGD (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_16p \fI*background\fP\fB);\fP
116
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]117\fI\fB
118
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]119\fBpng_byte png_get_channels (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
120
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]121\fI\fB
122
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]123\fBpng_uint_32 png_get_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_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
124
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]125\fI\fB
126
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]127\fBpng_uint_32 png_get_cHRM_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_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
128
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]129\fI\fB
130
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]131\fBpng_byte png_get_color_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
132
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]133\fI\fB
134
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]135\fBpng_byte png_get_compression_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
136
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]137\fI\fB
138
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]139\fBpng_byte png_get_copyright (png_structp \fIpng_ptr\fP\fB);\fP
140
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]141\fI\fB
142
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]143\fBpng_voidp png_get_error_ptr (png_structp \fIpng_ptr\fP\fB);\fP
144
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]145\fI\fB
146
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]147\fBpng_byte png_get_filter_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
148
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]149\fI\fB
150
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]151\fBpng_uint_32 png_get_gAMA (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fI*file_gamma\fP\fB);\fP
152
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]153\fI\fB
154
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]155\fBpng_uint_32 png_get_gAMA_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fI*int_file_gamma\fP\fB);\fP
156
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]157\fI\fB
158
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]159\fBpng_byte png_get_header_ver (png_structp \fIpng_ptr\fP\fB);\fP
160
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]161\fI\fB
162
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]163\fBpng_byte png_get_header_version (png_structp \fIpng_ptr\fP\fB);\fP
164
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]165\fI\fB
166
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]167\fBpng_uint_32 png_get_hIST (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_16p \fI*hist\fP\fB);\fP
168
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]169\fI\fB
170
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]171\fBpng_uint_32 png_get_iCCP (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charpp \fP\fIname\fP\fB, int \fP\fI*compression_type\fP\fB, png_charpp \fP\fIprofile\fP\fB, png_uint_32 \fI*proflen\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]172
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]173\fI\fB
174
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]175\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
176
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]177\fI\fB
178
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]179\fBpng_uint_32 png_get_image_height (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
180
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]181\fI\fB
182
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]183\fBpng_uint_32 png_get_image_width (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
184
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]185\fI\fB
186
187\fB#if \fI!defined(PNG_1_0_X)
188
189\fBpng_int_32 png_get_int_32 (png_bytep \fIbuf\fP\fB);\fP
190
191\fI\fB#endif
192
193\fI\fB
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]194
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]195\fBpng_byte png_get_interlace_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
196
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]197\fI\fB
198
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]199\fBpng_voidp png_get_io_ptr (png_structp \fIpng_ptr\fP\fB);\fP
200
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]201\fI\fB
202
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]203\fBpng_byte png_get_libpng_ver (png_structp \fIpng_ptr\fP\fB);\fP
204
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]205\fI\fB
206
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]207\fBpng_voidp png_get_mem_ptr(png_structp \fIpng_ptr\fP\fB);\fP
208
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]209\fI\fB
210
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]211\fBpng_uint_32 png_get_oFFs (png_structp \fP\fIpng_ptr\fP\fB, png_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
212
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]213\fI\fB
214
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]215\fBpng_uint_32 png_get_pCAL (png_structp \fP\fIpng_ptr\fP\fB, png_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
216
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]217\fI\fB
218
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]219\fBpng_uint_32 png_get_pHYs (png_structp \fP\fIpng_ptr\fP\fB, png_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
220
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]221\fI\fB
222
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]223\fBfloat png_get_pixel_aspect_ratio (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
224
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]225\fI\fB
226
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]227\fBpng_uint_32 png_get_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
228
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]229\fI\fB
230
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]231\fBpng_voidp png_get_progressive_ptr (png_structp \fIpng_ptr\fP\fB);\fP
232
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]233\fI\fB
234
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]235\fBpng_uint_32 png_get_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_colorp \fP\fI*palette\fP\fB, int \fI*num_palette\fP\fB);\fP
236
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]237\fI\fB
238
239\fBpng_byte png_get_rgb_to_gray_status (png_structp \fIpng_ptr)
240
241\fBpng_uint_32 png_get_rowbytes (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
242
243\fI\fB
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]244
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]245\fBpng_bytepp png_get_rows (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
246
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]247\fI\fB
248
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]249\fBpng_uint_32 png_get_sBIT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_8p \fI*sig_bit\fP\fB);\fP
250
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]251\fI\fB
252
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]253\fBpng_bytep png_get_signature (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
254
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]255\fI\fB
256
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]257\fBpng_uint_32 png_get_sPLT (png_structp \fP\fIpng_ptr\fP\fB, png_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]258
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]259\fI\fB
260
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]261\fBpng_uint_32 png_get_sRGB (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fI*intent\fP\fB);\fP
262
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]263\fI\fB
264
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]265\fBpng_uint_32 png_get_text (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_textp \fP\fI*text_ptr\fP\fB, int \fI*num_text\fP\fB);\fP
266
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]267\fI\fB
268
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]269\fBpng_uint_32 png_get_tIME (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fI*mod_time\fP\fB);\fP
270
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]271\fI\fB
272
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]273\fBpng_uint_32 png_get_tRNS (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fI*trans\fP\fB, int \fP\fI*num_trans\fP\fB, png_color_16p \fI*trans_values\fP\fB);\fP
274
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]275\fI\fB
276
277\fB#if \fI!defined(PNG_1_0_X)
278
279\fBpng_uint_16 png_get_uint_16 (png_bytep \fIbuf\fP\fB);\fP
280
281\fI\fB
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]282
283\fBpng_uint_32 png_get_uint_31 (png_bytep \fIbuf\fP\fB);\fP
284
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]285\fI\fB
286
287\fBpng_uint_32 png_get_uint_32 (png_bytep \fIbuf\fP\fB);\fP
288
289\fI\fB#endif
290
291\fI\fB
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]292
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]293\fBpng_uint_32 png_get_unknown_chunks (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_unknown_chunkpp \fIunknowns\fP\fB);\fP
294
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]295\fI\fB
296
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]297\fBpng_voidp png_get_user_chunk_ptr (png_structp \fIpng_ptr\fP\fB);\fP
298
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]299\fI\fB
300
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]301\fBpng_uint_32 png_get_user_height_max( png_structp \fIpng_ptr\fP\fB);\fP
302
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]303\fI\fB
304
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]305\fBpng_voidp png_get_user_transform_ptr (png_structp \fIpng_ptr\fP\fB);\fP
306
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]307\fI\fB
308
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]309\fBpng_uint_32 png_get_user_width_max (png_structp \fIpng_ptr\fP\fB);\fP
310
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]311\fI\fB
312
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]313\fBpng_uint_32 png_get_valid (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fIflag\fP\fB);\fP
314
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]315\fI\fB
316
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]317\fBpng_int_32 png_get_x_offset_microns (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]318
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]319\fI\fB
320
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]321\fBpng_int_32 png_get_x_offset_pixels (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]322
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]323\fI\fB
324
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]325\fBpng_uint_32 png_get_x_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
326
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]327\fI\fB
328
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]329\fBpng_int_32 png_get_y_offset_microns (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]330
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]331\fI\fB
332
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]333\fBpng_int_32 png_get_y_offset_pixels (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]334
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]335\fI\fB
336
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]337\fBpng_uint_32 png_get_y_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
338
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]339\fI\fB
340
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]341\fBpng_uint_32 png_get_compression_buffer_size (png_structp \fIpng_ptr\fP\fB);\fP
342
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]343\fI\fB
344
Glenn Randers-Pehrsonc1bfe682002-03-06 22:08:00 -0600[diff] [blame]345\fBint png_handle_as_unknown (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIchunk_name\fP\fB);\fP
346
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]347\fI\fB
348
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]349\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]350
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]351\fI\fB
352
Glenn Randers-Pehrsonbeb572e2006-08-19 13:59:24 -0500[diff] [blame]353\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]354
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]355\fI\fB
356
Glenn Randers-Pehrsonbeb572e2006-08-19 13:59:24 -0500[diff] [blame]357\fBpng_voidp png_malloc_default(png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]358
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]359\fI\fB
360
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]361\fBvoidp png_memcpy (png_voidp \fP\fIs1\fP\fB, png_voidp \fP\fIs2\fP\fB, png_size_t \fIsize\fP\fB);\fP
362
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]363\fI\fB
364
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]365\fBvoidp png_memset (png_voidp \fP\fIs1\fP\fB, int \fP\fIvalue\fP\fB, png_size_t \fIsize\fP\fB);\fP
366
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]367\fI\fB
368
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]369\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
370
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]371\fI\fB
372
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]373\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
374
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]375\fI\fB
376
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]377\fBvoid png_read_destroy (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_infop \fIend_info_ptr\fP\fB);\fP
378
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]379\fI\fB
380
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]381\fBvoid png_read_end (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
382
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]383\fI\fB
384
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]385\fBvoid png_read_image (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fIimage\fP\fB);\fP
386
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]387\fI\fB
388
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]389\fBvoid png_read_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
390
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]391\fI\fB
392
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]393\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]394
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]395\fI\fB
396
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]397\fBvoid png_read_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIrow\fP\fB, png_bytep \fIdisplay_row\fP\fB);\fP
398
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]399\fI\fB
400
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]401\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
402
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]403\fI\fB
404
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]405\fBvoid png_read_update_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
406
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]407\fI\fB
408
409\fB#if \fI!defined(PNG_1_0_X)
410
411\fBpng_save_int_32 (png_bytep \fP\fIbuf\fP\fB, png_int_32 \fIi\fP\fB);\fP
412
413\fI\fB
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]414
415\fBvoid png_save_uint_16 (png_bytep \fP\fIbuf\fP\fB, unsigned int \fIi\fP\fB);\fP
416
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]417\fI\fB
418
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]419\fBvoid png_save_uint_32 (png_bytep \fP\fIbuf\fP\fB, png_uint_32 \fIi\fP\fB);\fP
420
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]421\fI\fB
422
423\fBvoid png_set_add_alpha (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIfiller\fP\fB, int \fIflags\fP\fB);\fP
424
425\fI\fB#endif
426
427\fI\fB
Glenn Randers-Pehrson67864af2004-08-28 23:30:07 -0500[diff] [blame]428
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]429\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
430
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]431\fI\fB
432
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]433\fBvoid png_set_bgr (png_structp \fIpng_ptr\fP\fB);\fP
434
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]435\fI\fB
436
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]437\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
438
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]439\fI\fB
440
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]441\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
442
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]443\fI\fB
444
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]445\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
446
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]447\fI\fB
448
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]449\fBvoid png_set_compression_level (png_structp \fP\fIpng_ptr\fP\fB, int \fIlevel\fP\fB);\fP
450
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]451\fI\fB
452
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]453\fBvoid png_set_compression_mem_level (png_structp \fP\fIpng_ptr\fP\fB, int \fImem_level\fP\fB);\fP
454
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]455\fI\fB
456
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]457\fBvoid png_set_compression_method (png_structp \fP\fIpng_ptr\fP\fB, int \fImethod\fP\fB);\fP
458
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]459\fI\fB
460
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]461\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]462
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]463\fI\fB
464
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]465\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]466
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]467\fI\fB
468
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]469\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]470
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]471\fI\fB
472
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]473\fBvoid png_set_dither (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_dither\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]474
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]475\fI\fB
476
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]477\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]478
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]479\fI\fB
480
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]481\fBvoid png_set_expand (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]482
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]483\fI\fB
484
Glenn Randers-Pehrson1ce08362006-03-08 23:35:59 -0600[diff] [blame]485\fBvoid png_set_expand_gray_1_2_4_to_8(png_structp \fIpng_ptr\fP\fB);\fP
486
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]487\fI\fB
488
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]489\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]490
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]491\fI\fB
492
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]493\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]494
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]495\fI\fB
496
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]497\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]498
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]499\fI\fB
500
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]501\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]502
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]503\fI\fB
504
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]505\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]506
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]507\fI\fB
508
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]509\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]510
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]511\fI\fB
512
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]513\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
514
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]515\fI\fB
516
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]517\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]518
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]519\fI\fB
520
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]521\fBvoid png_set_gray_to_rgb (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]522
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]523\fI\fB
524
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]525\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]526
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]527\fI\fB
528
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]529\fBvoid png_set_iCCP (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fIname\fP\fB, int \fP\fIcompression_type\fP\fB, png_charp \fP\fIprofile\fP\fB, png_uint_32 \fIproflen\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]530
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]531\fI\fB
532
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]533\fBint png_set_interlace_handling (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]534
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]535\fI\fB
536
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]537\fBvoid png_set_invalid (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fImask\fP\fB);\fP
538
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]539\fI\fB
540
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]541\fBvoid png_set_invert_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]542
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]543\fI\fB
544
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]545\fBvoid png_set_invert_mono (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]546
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]547\fI\fB
548
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]549\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]550
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]551\fI\fB
552
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]553\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]554
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]555\fI\fB
556
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]557\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]558
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]559\fI\fB
560
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]561\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]562
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]563\fI\fB
564
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]565\fBvoid png_set_packing (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]566
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]567\fI\fB
568
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]569\fBvoid png_set_packswap (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]570
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]571\fI\fB
572
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]573\fBvoid png_set_palette_to_rgb(png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]574
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]575\fI\fB
576
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]577\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]578
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]579\fI\fB
580
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]581\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]582
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]583\fI\fB
584
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]585\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]586
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]587\fI\fB
588
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]589\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]590
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]591\fI\fB
592
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]593\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]594
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]595\fI\fB
596
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]597\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]598
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]599\fI\fB
600
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]601\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]602
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]603\fI\fB
604
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]605\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
606
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]607\fI\fB
608
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]609\fBvoid png_set_rgb_to_gray_fixed (png_structp \fP\fIpng_ptr\fP\fB, int error_action png_fixed_point \fP\fIred\fP\fB, png_fixed_point \fIgreen\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]610
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]611\fI\fB
612
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]613\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
614
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]615\fI\fB
616
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]617\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]618
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]619\fI\fB
620
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]621\fBvoid png_set_sCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fIunit\fP\fB, double \fP\fIwidth\fP\fB, double \fIheight\fP\fB);\fP
622
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]623\fI\fB
624
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]625\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]626
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]627\fI\fB
628
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]629\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]630
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]631\fI\fB
632
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]633\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]634
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]635\fI\fB
636
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]637\fBvoid png_set_sRGB (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIintent\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]638
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]639\fI\fB
640
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]641\fBvoid png_set_sRGB_gAMA_and_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIintent\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]642
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]643\fI\fB
644
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]645\fBvoid png_set_strip_16 (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]646
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]647\fI\fB
648
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]649\fBvoid png_set_strip_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]650
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]651\fI\fB
652
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]653\fBvoid png_set_swap (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]654
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]655\fI\fB
656
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]657\fBvoid png_set_swap_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]658
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]659\fI\fB
660
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]661\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]662
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]663\fI\fB
664
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]665\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]666
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]667\fI\fB
668
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]669\fBvoid png_set_tRNS (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fItrans\fP\fB, int \fP\fInum_trans\fP\fB, png_color_16p \fItrans_values\fP\fB);\fP
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]670
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]671\fI\fB
672
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]673\fBvoid png_set_tRNS_to_alpha(png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]674
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]675\fI\fB
676
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]677\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
678
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]679\fI\fB
680
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]681\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
682
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]683\fI\fB
684
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]685\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
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]686
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]687\fI\fB
688
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]689\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
690
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]691\fI\fB
692
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]693\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]694
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]695\fI\fB
696
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]697\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]698
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]699\fI\fB
700
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]701\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]702
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]703\fI\fB
704
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]705\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]706
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]707\fI\fB
708
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]709\fBvoid png_set_compression_buffer_size(png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP
710
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]711\fI\fB
712
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]713\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]714
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]715\fI\fB
716
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]717\fBvoid png_start_read_image (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]718
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]719\fI\fB
720
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]721\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]722
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]723\fI\fB
724
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]725\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]726
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]727\fI\fB
728
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]729\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]730
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]731\fI\fB
732
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]733\fBvoid png_write_chunk_end (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]734
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]735\fI\fB
736
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]737\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]738
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]739\fI\fB
740
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]741\fBvoid png_write_destroy (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]742
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]743\fI\fB
744
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]745\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]746
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]747\fI\fB
748
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]749\fBvoid png_write_flush (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]750
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]751\fI\fB
752
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]753\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]754
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]755\fI\fB
756
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]757\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]758
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]759\fI\fB
760
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]761\fBvoid png_write_info_before_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
762
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]763\fI\fB
764
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]765\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]766
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]767\fI\fB
768
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]769\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]770
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]771\fI\fB
772
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]773\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]774
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]775\fI\fB
776
Glenn Randers-Pehrson6bc53be2006-06-16 07:52:03 -0500[diff] [blame]777\fBvoid png_write_sig (png_structp \fIpng_ptr\fP\fB);\fP
778
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]779\fI\fB
780
Glenn Randers-Pehrson5b5dcf82004-07-17 22:45:44 -0500[diff] [blame]781\fBvoidpf png_zalloc (voidpf \fP\fIpng_ptr\fP\fB, uInt \fP\fIitems\fP\fB, uInt \fIsize\fP\fB);\fP
782
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]783\fI\fB
784
Glenn Randers-Pehrson5b5dcf82004-07-17 22:45:44 -0500[diff] [blame]785\fBvoid png_zfree (voidpf \fP\fIpng_ptr\fP\fB, voidpf \fIptr\fP\fB);\fP
786
Glenn Randers-Pehrson145f5c82008-07-10 09:13:13 -0500[diff] [blame]787\fI\fB
788
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]789.SH DESCRIPTION
790The
791.I libpng
792library supports encoding, decoding, and various manipulations of
793the Portable Network Graphics (PNG) format image files. It uses the
794.IR zlib(3)
795compression library.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]796Following is a copy of the libpng.txt file that accompanies libpng.
797.SH LIBPNG.TXT
798libpng.txt - A description on how to use and modify libpng
799
Glenn Randers-Pehrson895a9c92008-07-25 08:51:18 -0500[diff] [blame^]800 libpng version 1.4.0beta24 - July 25, 2008
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]801 Updated and distributed by Glenn Randers-Pehrson
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]802 <glennrp at users.sourceforge.net>
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]803 Copyright (c) 1998-2005 Glenn Randers-Pehrson
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]804 For conditions of distribution and use, see copyright
805 notice in png.h.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]806
807 based on:
808
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]809 libpng 1.0 beta 6 version 0.96 May 28, 1997
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]810 Updated and distributed by Andreas Dilger
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]811 Copyright (c) 1996, 1997 Andreas Dilger
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]812
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]813 libpng 1.0 beta 2 - version 0.88 January 26, 1996
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]814 For conditions of distribution and use, see copyright
815 notice in png.h. Copyright (c) 1995, 1996 Guy Eric
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]816 Schalnat, Group 42, Inc.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]817
818 Updated/rewritten per request in the libpng FAQ
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]819 Copyright (c) 1995, 1996 Frank J. T. Wojcik
820 December 18, 1995 & January 20, 1996
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]821
822.SH I. Introduction
823
824This file describes how to use and modify the PNG reference library
825(known as libpng) for your own use. There are five sections to this
826file: introduction, structures, reading, writing, and modification and
827configuration notes for various special platforms. In addition to this
828file, example.c is a good starting point for using the library, as
829it is heavily commented and should include everything most people
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]830will need. We assume that libpng is already installed; see the
831INSTALL file for instructions on how to install libpng.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]832
833Libpng was written as a companion to the PNG specification, as a way
834of reducing the amount of time and effort it takes to support the PNG
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]835file format in application programs.
836
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]837The PNG specification (second edition), November 2003, is available as
838a W3C Recommendation and as an ISO Standard (ISO/IEC 15948:2003 (E)) at
839<http://www.w3.org/TR/2003/REC-PNG-20031110/
840The W3C and ISO documents have identical technical content.
841
842The PNG-1.2 specification is available at
843<http://www.libpng.org/pub/png/documents/>
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]844
845The PNG-1.0 specification is available
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]846as RFC 2083 <http://www.libpng.org/pub/png/documents/> and as a
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]847W3C Recommendation <http://www.w3.org/TR/REC.png.html>. Some
848additional chunks are described in the special-purpose public chunks
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]849documents at <http://www.libpng.org/pub/png/documents/>.
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]850
851Other information
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]852about 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]853page, <http://www.libpng.org/pub/png/>.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]854
855Most users will not have to modify the library significantly; advanced
856users may want to modify it more. All attempts were made to make it as
857complete as possible, while keeping the code easy to understand.
858Currently, this library only supports C. Support for other languages
859is being considered.
860
861Libpng has been designed to handle multiple sessions at one time,
862to be easily modifiable, to be portable to the vast majority of
863machines (ANSI, K&R, 16-, 32-, and 64-bit) available, and to be easy
864to use. The ultimate goal of libpng is to promote the acceptance of
865the PNG file format in whatever way possible. While there is still
866work to be done (see the TODO file), libpng should cover the
867majority of the needs of its users.
868
869Libpng uses zlib for its compression and decompression of PNG files.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]870Further information about zlib, and the latest version of zlib, can
Glenn Randers-Pehrsond56aca72000-11-23 11:51:42 -0600[diff] [blame]871be 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]872The zlib compression utility is a general purpose utility that is
873useful for more than PNG files, and can be used without libpng.
874See the documentation delivered with zlib for more details.
875You can usually find the source files for the zlib utility wherever you
876find the libpng source files.
877
878Libpng is thread safe, provided the threads are using different
879instances of the structures. Each thread should have its own
880png_struct and png_info instances, and thus its own image.
881Libpng does not protect itself against two threads using the
Glenn Randers-Pehrson1ea0ff32001-08-07 22:25:59 -0500[diff] [blame]882same instance of a structure. Note: thread safety may be defeated
883by use of some of the MMX assembler code in pnggccrd.c, which is only
884compiled when the user defines PNG_THREAD_UNSAFE_OK.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]885
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]886.SH II. Structures
887
888There are two main structures that are important to libpng, png_struct
889and png_info. The first, png_struct, is an internal structure that
890will not, for the most part, be used by a user except as the first
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]891variable passed to every libpng function call.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]892
893The png_info structure is designed to provide information about the
894PNG file. At one time, the fields of png_info were intended to be
895directly accessible to the user. However, this tended to cause problems
896with applications using dynamically loaded libraries, and as a result
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]897a set of interface functions for png_info (the png_get_*() and png_set_*()
898functions) was developed. The fields of png_info are still available for
899older applications, but it is suggested that applications use the new
900interfaces if at all possible.
901
902Applications that do make direct access to the members of png_struct (except
903for png_ptr->jmpbuf) must be recompiled whenever the library is updated,
904and applications that make direct access to the members of png_info must
905be recompiled if they were compiled or loaded with libpng version 1.0.6,
906in which the members were in a different order. In version 1.0.7, the
907members of the png_info structure reverted to the old order, as they were
908in versions 0.97c through 1.0.5. Starting with version 2.0.0, both
909structures are going to be hidden, and the contents of the structures will
910only be accessible through the png_get/png_set functions.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]911
912The png.h header file is an invaluable reference for programming with libpng.
913And while I'm on the topic, make sure you include the libpng header file:
914
915#include <png.h>
916
917.SH III. Reading
918
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]919We'll now walk you through the possible functions to call when reading
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]920in a PNG file sequentially, briefly explaining the syntax and purpose
921of each one. See example.c and png.h for more detail. While
922progressive reading is covered in the next section, you will still
923need some of the functions discussed in this section to read a PNG
924file.
925
926.SS Setup
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]927
928You will want to do the I/O initialization(*) before you get into libpng,
929so if it doesn't work, you don't have much to undo. Of course, you
930will also want to insure that you are, in fact, dealing with a PNG
931file. 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]932To use it, pass in the first 1 to 8 bytes of the file to the function
933png_sig_cmp(), and it will return 0 if the bytes match the corresponding
934bytes of the PNG signature, or nonzero otherwise. Of course, the more bytes
935you pass in, the greater the accuracy of the prediction.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]936
937If you are intending to keep the file pointer open for use in libpng,
938you must ensure you don't read more than 8 bytes from the beginning
939of the file, and you also have to make a call to png_set_sig_bytes_read()
940with the number of bytes you read from the beginning. Libpng will
941then only check the bytes (if any) that your program didn't read.
942
943(*): If you are not using the standard I/O functions, you will need
944to replace them with custom functions. See the discussion under
945Customizing libpng.
946
947
948 FILE *fp = fopen(file_name, "rb");
949 if (!fp)
950 {
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]951 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]952 }
953 fread(header, 1, number, fp);
Glenn Randers-Pehrsonc9442291999-01-06 21:50:16 -0600[diff] [blame]954 is_png = !png_sig_cmp(header, 0, number);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]955 if (!is_png)
956 {
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]957 return (NOT_PNG);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]958 }
959
960
961Next, png_struct and png_info need to be allocated and initialized. In
962order to ensure that the size of these structures is correct even with a
963dynamically linked libpng, there are functions to initialize and
964allocate the structures. We also pass the library version, optional
965pointers to error handling functions, and a pointer to a data struct for
966use by the error functions, if necessary (the pointer and functions can
967be NULL if the default error handlers are to be used). See the section
968on Changes to Libpng below regarding the old initialization functions.
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]969The structure allocation functions quietly return NULL if they fail to
970create the structure, so your application should check for that.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]971
972 png_structp png_ptr = png_create_read_struct
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]973 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]974 user_error_fn, user_warning_fn);
975 if (!png_ptr)
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]976 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]977
978 png_infop info_ptr = png_create_info_struct(png_ptr);
979 if (!info_ptr)
980 {
981 png_destroy_read_struct(&png_ptr,
982 (png_infopp)NULL, (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]983 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]984 }
985
986 png_infop end_info = png_create_info_struct(png_ptr);
987 if (!end_info)
988 {
989 png_destroy_read_struct(&png_ptr, &info_ptr,
990 (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]991 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]992 }
993
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]994If you want to use your own memory allocation routines,
995define PNG_USER_MEM_SUPPORTED and use
996png_create_read_struct_2() instead of png_create_read_struct():
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]997
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]998 png_structp png_ptr = png_create_read_struct_2
999 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
1000 user_error_fn, user_warning_fn, (png_voidp)
1001 user_mem_ptr, user_malloc_fn, user_free_fn);
1002
1003The error handling routines passed to png_create_read_struct()
1004and the memory alloc/free routines passed to png_create_struct_2()
1005are only necessary if you are not using the libpng supplied error
1006handling and memory alloc/free functions.
1007
1008When libpng encounters an error, it expects to longjmp back
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1009to your routine. Therefore, you will need to call setjmp and pass
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1010your png_jmpbuf(png_ptr). If you read the file from different
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1011routines, you will need to update the jmpbuf field every time you enter
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1012a new routine that will call a png_*() function.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1013
1014See your documentation of setjmp/longjmp for your compiler for more
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]1015information on setjmp/longjmp. See the discussion on libpng error
1016handling in the Customizing Libpng section below for more information
1017on the libpng error handling. If an error occurs, and libpng longjmp's
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1018back to your setjmp, you will want to call png_destroy_read_struct() to
1019free any memory.
1020
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1021 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1022 {
1023 png_destroy_read_struct(&png_ptr, &info_ptr,
1024 &end_info);
1025 fclose(fp);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]1026 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1027 }
1028
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1029If you would rather avoid the complexity of setjmp/longjmp issues,
1030you can compile libpng with PNG_SETJMP_NOT_SUPPORTED, in which case
1031errors will result in a call to PNG_ABORT() which defaults to abort().
1032
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1033Now you need to set up the input code. The default for libpng is to
1034use the C function fread(). If you use this, you will need to pass a
1035valid FILE * in the function png_init_io(). Be sure that the file is
1036opened in binary mode. If you wish to handle reading data in another
1037way, you need not call the png_init_io() function, but you must then
1038implement the libpng I/O methods discussed in the Customizing Libpng
1039section below.
1040
1041 png_init_io(png_ptr, fp);
1042
1043If you had previously opened the file and read any of the signature from
1044the beginning in order to see if this was a PNG file, you need to let
1045libpng know that there are some bytes missing from the start of the file.
1046
1047 png_set_sig_bytes(png_ptr, number);
1048
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1049.SS Setting up callback code
1050
1051You can set up a callback function to handle any unknown chunks in the
1052input stream. You must supply the function
1053
1054 read_chunk_callback(png_ptr ptr,
1055 png_unknown_chunkp chunk);
1056 {
1057 /* The unknown chunk structure contains your
1058 chunk data: */
1059 png_byte name[5];
1060 png_byte *data;
1061 png_size_t size;
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1062 /* Note that libpng has already taken care of
1063 the CRC handling */
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1064
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1065 /* put your code here. Return one of the
1066 following: */
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1067
1068 return (-n); /* chunk had an error */
1069 return (0); /* did not recognize */
1070 return (n); /* success */
1071 }
1072
1073(You can give your function another name that you like instead of
1074"read_chunk_callback")
1075
1076To inform libpng about your function, use
1077
1078 png_set_read_user_chunk_fn(png_ptr, user_chunk_ptr,
1079 read_chunk_callback);
1080
1081This names not only the callback function, but also a user pointer that
1082you can retrieve with
1083
1084 png_get_user_chunk_ptr(png_ptr);
1085
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]1086At this point, you can set up a callback function that will be
1087called after each row has been read, which you can use to control
1088a progress meter or the like. It's demonstrated in pngtest.c.
1089You must supply a function
1090
Glenn Randers-Pehrsone68f5a32001-05-14 09:20:53 -0500[diff] [blame]1091 void read_row_callback(png_ptr ptr, png_uint_32 row,
1092 int pass);
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]1093 {
1094 /* put your code here */
1095 }
1096
1097(You can give it another name that you like instead of "read_row_callback")
1098
1099To inform libpng about your function, use
1100
1101 png_set_read_status_fn(png_ptr, read_row_callback);
1102
Glenn Randers-Pehrson67864af2004-08-28 23:30:07 -0500[diff] [blame]1103.SS Width and height limits
1104
1105The PNG specification allows the width and height of an image to be as
1106large as 2^31-1 (0x7fffffff), or about 2.147 billion rows and columns.
1107Since very few applications really need to process such large images,
1108we have imposed an arbitrary 1-million limit on rows and columns.
1109Larger images will be rejected immediately with a png_error() call. If
1110you wish to override this limit, you can use
1111
1112 png_set_user_limits(png_ptr, width_max, height_max);
1113
1114to set your own limits, or use width_max = height_max = 0x7fffffffL
1115to allow all valid dimensions (libpng may reject some very large images
1116anyway because of potential buffer overflow conditions).
1117
1118You should put this statement after you create the PNG structure and
1119before calling png_read_info(), png_read_png(), or png_process_data().
1120If you need to retrieve the limits that are being applied, use
1121
1122 width_max = png_get_user_width_max(png_ptr);
1123 height_max = png_get_user_height_max(png_ptr);
1124
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1125.SS Unknown-chunk handling
1126
1127Now you get to set the way the library processes unknown chunks in the
1128input PNG stream. Both known and unknown chunks will be read. Normal
1129behavior is that known chunks will be parsed into information in
1130various info_ptr members; unknown chunks will be discarded. To change
1131this, you can call:
1132
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]1133 png_set_keep_unknown_chunks(png_ptr, keep,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1134 chunk_list, num_chunks);
Glenn Randers-Pehrsond029a752004-08-09 21:50:32 -0500[diff] [blame]1135 keep - 0: do not handle as unknown
1136 1: do not keep
1137 2: keep only if safe-to-copy
1138 3: keep even if unsafe-to-copy
1139 You can use these definitions:
1140 PNG_HANDLE_CHUNK_AS_DEFAULT 0
1141 PNG_HANDLE_CHUNK_NEVER 1
1142 PNG_HANDLE_CHUNK_IF_SAFE 2
1143 PNG_HANDLE_CHUNK_ALWAYS 3
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1144 chunk_list - list of chunks affected (a byte string,
1145 five bytes per chunk, NULL or '\0' if
1146 num_chunks is 0)
1147 num_chunks - number of chunks affected; if 0, all
Glenn Randers-Pehrsondff799e2004-08-07 21:42:49 -0500[diff] [blame]1148 unknown chunks are affected. If nonzero,
1149 only the chunks in the list are affected
1150
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1151Unknown chunks declared in this way will be saved as raw data onto a
1152list of png_unknown_chunk structures. If a chunk that is normally
1153known to libpng is named in the list, it will be handled as unknown,
1154according to the "keep" directive. If a chunk is named in successive
1155instances of png_set_keep_unknown_chunks(), the final instance will
Glenn Randers-Pehrsond029a752004-08-09 21:50:32 -0500[diff] [blame]1156take precedence. The IHDR and IEND chunks should not be named in
1157chunk_list; if they are, libpng will process them normally anyway.
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1158
1159.SS The high-level read interface
1160
1161At this point there are two ways to proceed; through the high-level
1162read interface, or through a sequence of low-level read operations.
1163You can use the high-level interface if (a) you are willing to read
1164the entire image into memory, and (b) the input transformations
1165you want to do are limited to the following set:
1166
1167 PNG_TRANSFORM_IDENTITY No transformation
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1168 PNG_TRANSFORM_STRIP_16 Strip 16-bit samples to
1169 8 bits
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1170 PNG_TRANSFORM_STRIP_ALPHA Discard the alpha channel
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1171 PNG_TRANSFORM_PACKING Expand 1, 2 and 4-bit
1172 samples to bytes
1173 PNG_TRANSFORM_PACKSWAP Change order of packed
1174 pixels to LSB first
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1175 PNG_TRANSFORM_EXPAND Perform set_expand()
1176 PNG_TRANSFORM_INVERT_MONO Invert monochrome images
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1177 PNG_TRANSFORM_SHIFT Normalize pixels to the
1178 sBIT depth
1179 PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA
1180 to BGRA
1181 PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA
1182 to AG
1183 PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity
1184 to transparency
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1185 PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples
1186
1187(This excludes setting a background color, doing gamma transformation,
1188dithering, and setting filler.) If this is the case, simply do this:
1189
1190 png_read_png(png_ptr, info_ptr, png_transforms, NULL)
1191
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]1192where png_transforms is an integer containing the bitwise OR of
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1193some set of transformation flags. This call is equivalent to png_read_info(),
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1194followed the set of transformations indicated by the transform mask,
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1195then png_read_image(), and finally png_read_end().
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1196
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1197(The final parameter of this call is not yet used. Someday it might point
1198to transformation parameters required by some future input transform.)
1199
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]1200You must use png_transforms and not call any png_set_transform() functions
1201when you use png_read_png().
1202
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1203After you have called png_read_png(), you can retrieve the image data
1204with
1205
1206 row_pointers = png_get_rows(png_ptr, info_ptr);
1207
1208where row_pointers is an array of pointers to the pixel data for each row:
1209
1210 png_bytep row_pointers[height];
1211
1212If you know your image size and pixel size ahead of time, you can allocate
1213row_pointers prior to calling png_read_png() with
1214
Glenn Randers-Pehrsonbeb572e2006-08-19 13:59:24 -0500[diff] [blame]1215 if (height > PNG_UINT_32_MAX/sizeof(png_bytep))
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]1216 png_error (png_ptr,
1217 "Image is too tall to process in memory");
1218 if (width > PNG_UINT_32_MAX/pixel_size)
1219 png_error (png_ptr,
1220 "Image is too wide to process in memory");
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1221 row_pointers = png_malloc(png_ptr,
Glenn Randers-Pehrsonbeb572e2006-08-19 13:59:24 -0500[diff] [blame]1222 height*sizeof(png_bytep));
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1223 for (int i=0; i<height, i++)
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1224 row_pointers[i]=png_malloc(png_ptr,
1225 width*pixel_size);
Glenn Randers-Pehrsond56aca72000-11-23 11:51:42 -0600[diff] [blame]1226 png_set_rows(png_ptr, info_ptr, &row_pointers);
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1227
1228Alternatively you could allocate your image in one big block and define
1229row_pointers[i] to point into the proper places in your block.
1230
1231If you use png_set_rows(), the application is responsible for freeing
1232row_pointers (and row_pointers[i], if they were separately allocated).
1233
1234If you don't allocate row_pointers ahead of time, png_read_png() will
1235do it, and it'll be free'ed when you call png_destroy_*().
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1236
1237.SS The low-level read interface
1238
1239If you are going the low-level route, you are now ready to read all
1240the file information up to the actual image data. You do this with a
1241call to png_read_info().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1242
1243 png_read_info(png_ptr, info_ptr);
1244
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1245This will process all chunks up to but not including the image data.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1246
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1247.SS Querying the info structure
1248
1249Functions are used to get the information from the info_ptr once it
1250has been read. Note that these fields may not be completely filled
1251in until png_read_end() has read the chunk data following the image.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1252
1253 png_get_IHDR(png_ptr, info_ptr, &width, &height,
1254 &bit_depth, &color_type, &interlace_type,
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]1255 &compression_type, &filter_method);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1256
1257 width - holds the width of the image
1258 in pixels (up to 2^31).
1259 height - holds the height of the image
1260 in pixels (up to 2^31).
1261 bit_depth - holds the bit depth of one of the
1262 image channels. (valid values are
1263 1, 2, 4, 8, 16 and depend also on
1264 the color_type. See also
1265 significant bits (sBIT) below).
1266 color_type - describes which color/alpha channels
1267 are present.
1268 PNG_COLOR_TYPE_GRAY
1269 (bit depths 1, 2, 4, 8, 16)
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1270 PNG_COLOR_TYPE_GRAY_ALPHA
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1271 (bit depths 8, 16)
1272 PNG_COLOR_TYPE_PALETTE
1273 (bit depths 1, 2, 4, 8)
1274 PNG_COLOR_TYPE_RGB
1275 (bit_depths 8, 16)
1276 PNG_COLOR_TYPE_RGB_ALPHA
1277 (bit_depths 8, 16)
1278
1279 PNG_COLOR_MASK_PALETTE
1280 PNG_COLOR_MASK_COLOR
1281 PNG_COLOR_MASK_ALPHA
1282
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]1283 filter_method - (must be PNG_FILTER_TYPE_BASE
1284 for PNG 1.0, and can also be
1285 PNG_INTRAPIXEL_DIFFERENCING if
1286 the PNG datastream is embedded in
1287 a MNG-1.0 datastream)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1288 compression_type - (must be PNG_COMPRESSION_TYPE_BASE
1289 for PNG 1.0)
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1290 interlace_type - (PNG_INTERLACE_NONE or
1291 PNG_INTERLACE_ADAM7)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1292 Any or all of interlace_type, compression_type, of
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1293 filter_method can be NULL if you are
1294 not interested in their values.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1295
1296 channels = png_get_channels(png_ptr, info_ptr);
1297 channels - number of channels of info for the
1298 color type (valid values are 1 (GRAY,
1299 PALETTE), 2 (GRAY_ALPHA), 3 (RGB),
1300 4 (RGB_ALPHA or RGB + filler byte))
1301 rowbytes = png_get_rowbytes(png_ptr, info_ptr);
1302 rowbytes - number of bytes needed to hold a row
1303
1304 signature = png_get_signature(png_ptr, info_ptr);
1305 signature - holds the signature read from the
1306 file (if any). The data is kept in
1307 the same offset it would be if the
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1308 whole signature were read (i.e. if an
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1309 application had already read in 4
1310 bytes of signature before starting
1311 libpng, the remaining 4 bytes would
1312 be in signature[4] through signature[7]
1313 (see png_set_sig_bytes())).
1314
1315
1316 width = png_get_image_width(png_ptr,
1317 info_ptr);
1318 height = png_get_image_height(png_ptr,
1319 info_ptr);
1320 bit_depth = png_get_bit_depth(png_ptr,
1321 info_ptr);
1322 color_type = png_get_color_type(png_ptr,
1323 info_ptr);
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]1324 filter_method = png_get_filter_type(png_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1325 info_ptr);
1326 compression_type = png_get_compression_type(png_ptr,
1327 info_ptr);
1328 interlace_type = png_get_interlace_type(png_ptr,
1329 info_ptr);
1330
1331
1332These are also important, but their validity depends on whether the chunk
1333has been read. The png_get_valid(png_ptr, info_ptr, PNG_INFO_<chunk>) and
1334png_get_<chunk>(png_ptr, info_ptr, ...) functions return non-zero if the
1335data has been read, or zero if it is missing. The parameters to the
1336png_get_<chunk> are set directly if they are simple data types, or a pointer
1337into the info_ptr is returned for any complex types.
1338
1339 png_get_PLTE(png_ptr, info_ptr, &palette,
1340 &num_palette);
1341 palette - the palette for the file
1342 (array of png_color)
1343 num_palette - number of entries in the palette
1344
1345 png_get_gAMA(png_ptr, info_ptr, &gamma);
1346 gamma - the gamma the file is written
1347 at (PNG_INFO_gAMA)
1348
1349 png_get_sRGB(png_ptr, info_ptr, &srgb_intent);
1350 srgb_intent - the rendering intent (PNG_INFO_sRGB)
1351 The presence of the sRGB chunk
1352 means that the pixel data is in the
1353 sRGB color space. This chunk also
1354 implies specific values of gAMA and
1355 cHRM.
1356
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1357 png_get_iCCP(png_ptr, info_ptr, &name,
1358 &compression_type, &profile, &proflen);
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1359 name - The profile name.
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1360 compression - The compression type; always
1361 PNG_COMPRESSION_TYPE_BASE for PNG 1.0.
1362 You may give NULL to this argument to
1363 ignore it.
1364 profile - International Color Consortium color
1365 profile data. May contain NULs.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1366 proflen - length of profile data in bytes.
1367
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1368 png_get_sBIT(png_ptr, info_ptr, &sig_bit);
1369 sig_bit - the number of significant bits for
1370 (PNG_INFO_sBIT) each of the gray,
1371 red, green, and blue channels,
1372 whichever are appropriate for the
1373 given color type (png_color_16)
1374
1375 png_get_tRNS(png_ptr, info_ptr, &trans, &num_trans,
1376 &trans_values);
1377 trans - array of transparent entries for
1378 palette (PNG_INFO_tRNS)
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]1379 trans_values - graylevel or color sample values of
1380 the single transparent color for
1381 non-paletted images (PNG_INFO_tRNS)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1382 num_trans - number of transparent entries
1383 (PNG_INFO_tRNS)
1384
1385 png_get_hIST(png_ptr, info_ptr, &hist);
1386 (PNG_INFO_hIST)
1387 hist - histogram of palette (array of
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1388 png_uint_16)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1389
1390 png_get_tIME(png_ptr, info_ptr, &mod_time);
1391 mod_time - time image was last modified
1392 (PNG_VALID_tIME)
1393
1394 png_get_bKGD(png_ptr, info_ptr, &background);
1395 background - background color (PNG_VALID_bKGD)
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1396 valid 16-bit red, green and blue
1397 values, regardless of color_type
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1398
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]1399 num_comments = png_get_text(png_ptr, info_ptr,
1400 &text_ptr, &num_text);
1401 num_comments - number of comments
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1402 text_ptr - array of png_text holding image
1403 comments
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1404 text_ptr[i].compression - type of compression used
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1405 on "text" PNG_TEXT_COMPRESSION_NONE
1406 PNG_TEXT_COMPRESSION_zTXt
1407 PNG_ITXT_COMPRESSION_NONE
1408 PNG_ITXT_COMPRESSION_zTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1409 text_ptr[i].key - keyword for comment. Must contain
1410 1-79 characters.
1411 text_ptr[i].text - text comments for current
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]1412 keyword. Can be empty.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1413 text_ptr[i].text_length - length of text string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1414 after decompression, 0 for iTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1415 text_ptr[i].itxt_length - length of itxt string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1416 after decompression, 0 for tEXt/zTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1417 text_ptr[i].lang - language of comment (empty
1418 string for unknown).
Glenn Randers-Pehrson73d57cb2002-03-25 18:49:08 -0600[diff] [blame]1419 text_ptr[i].lang_key - keyword in UTF-8
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1420 (empty string for unknown).
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1421 num_text - number of comments (same as
1422 num_comments; you can put NULL here
1423 to avoid the duplication)
1424 Note while png_set_text() will accept text, language,
1425 and translated keywords that can be NULL pointers, the
1426 structure returned by png_get_text will always contain
1427 regular zero-terminated C strings. They might be
1428 empty strings but they will never be NULL pointers.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1429
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1430 num_spalettes = png_get_sPLT(png_ptr, info_ptr,
1431 &palette_ptr);
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1432 palette_ptr - array of palette structures holding
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1433 contents of one or more sPLT chunks
1434 read.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1435 num_spalettes - number of sPLT chunks read.
1436
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1437 png_get_oFFs(png_ptr, info_ptr, &offset_x, &offset_y,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1438 &unit_type);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1439 offset_x - positive offset from the left edge
1440 of the screen
1441 offset_y - positive offset from the top edge
1442 of the screen
1443 unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
1444
1445 png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1446 &unit_type);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1447 res_x - pixels/unit physical resolution in
1448 x direction
1449 res_y - pixels/unit physical resolution in
1450 x direction
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1451 unit_type - PNG_RESOLUTION_UNKNOWN,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1452 PNG_RESOLUTION_METER
1453
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1454 png_get_sCAL(png_ptr, info_ptr, &unit, &width,
1455 &height)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1456 unit - physical scale units (an integer)
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1457 width - width of a pixel in physical scale units
1458 height - height of a pixel in physical scale units
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1459 (width and height are doubles)
1460
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1461 png_get_sCAL_s(png_ptr, info_ptr, &unit, &width,
1462 &height)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1463 unit - physical scale units (an integer)
1464 width - width of a pixel in physical scale units
1465 height - height of a pixel in physical scale units
1466 (width and height are strings like "2.54")
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1467
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1468 num_unknown_chunks = png_get_unknown_chunks(png_ptr,
1469 info_ptr, &unknowns)
1470 unknowns - array of png_unknown_chunk
1471 structures holding unknown chunks
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1472 unknowns[i].name - name of unknown chunk
1473 unknowns[i].data - data of unknown chunk
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1474 unknowns[i].size - size of unknown chunk's data
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1475 unknowns[i].location - position of chunk in file
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1476
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1477 The value of "i" corresponds to the order in which the
1478 chunks were read from the PNG file or inserted with the
1479 png_set_unknown_chunks() function.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1480
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1481The data from the pHYs chunk can be retrieved in several convenient
1482forms:
1483
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1484 res_x = png_get_x_pixels_per_meter(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1485 info_ptr)
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1486 res_y = png_get_y_pixels_per_meter(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1487 info_ptr)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1488 res_x_and_y = png_get_pixels_per_meter(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1489 info_ptr)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1490 res_x = png_get_x_pixels_per_inch(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1491 info_ptr)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1492 res_y = png_get_y_pixels_per_inch(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1493 info_ptr)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1494 res_x_and_y = png_get_pixels_per_inch(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1495 info_ptr)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1496 aspect_ratio = png_get_pixel_aspect_ratio(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1497 info_ptr)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1498
1499 (Each of these returns 0 [signifying "unknown"] if
1500 the data is not present or if res_x is 0;
1501 res_x_and_y is 0 if res_x != res_y)
1502
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1503The data from the oFFs chunk can be retrieved in several convenient
1504forms:
1505
1506 x_offset = png_get_x_offset_microns(png_ptr, info_ptr);
1507 y_offset = png_get_y_offset_microns(png_ptr, info_ptr);
1508 x_offset = png_get_x_offset_inches(png_ptr, info_ptr);
1509 y_offset = png_get_y_offset_inches(png_ptr, info_ptr);
1510
1511 (Each of these returns 0 [signifying "unknown" if both
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1512 x and y are 0] if the data is not present or if the
1513 chunk is present but the unit is the pixel)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1514
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1515For more information, see the png_info definition in png.h and the
1516PNG specification for chunk contents. Be careful with trusting
1517rowbytes, as some of the transformations could increase the space
1518needed to hold a row (expand, filler, gray_to_rgb, etc.).
1519See png_read_update_info(), below.
1520
1521A quick word about text_ptr and num_text. PNG stores comments in
1522keyword/text pairs, one pair per chunk, with no limit on the number
1523of text chunks, and a 2^31 byte limit on their size. While there are
1524suggested keywords, there is no requirement to restrict the use to these
1525strings. It is strongly suggested that keywords and text be sensible
1526to humans (that's the point), so don't use abbreviations. Non-printing
1527symbols are not allowed. See the PNG specification for more details.
1528There is also no requirement to have text after the keyword.
1529
1530Keywords should be limited to 79 Latin-1 characters without leading or
1531trailing spaces, but non-consecutive spaces are allowed within the
1532keyword. It is possible to have the same keyword any number of times.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1533The text_ptr is an array of png_text structures, each holding a
1534pointer to a language string, a pointer to a keyword and a pointer to
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1535a text string. The text string, language code, and translated
1536keyword may be empty or NULL pointers. The keyword/text
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1537pairs are put into the array in the order that they are received.
1538However, some or all of the text chunks may be after the image, so, to
1539make sure you have read all the text chunks, don't mess with these
1540until after you read the stuff after the image. This will be
1541mentioned again below in the discussion that goes with png_read_end().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1542
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1543.SS Input transformations
1544
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1545After you've read the header information, you can set up the library
1546to handle any special transformations of the image data. The various
1547ways to transform the data will be described in the order that they
1548should occur. This is important, as some of these change the color
1549type and/or bit depth of the data, and some others only work on
1550certain color types and bit depths. Even though each transformation
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1551checks 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]1552make sure to only enable a transformation if it will be valid for the
1553data. For example, don't swap red and blue on grayscale data.
1554
1555The colors used for the background and transparency values should be
1556supplied in the same format/depth as the current image data. They
1557are stored in the same format/depth as the image data in a bKGD or tRNS
1558chunk, so this is what libpng expects for this data. The colors are
1559transformed to keep in sync with the image data when an application
1560calls the png_read_update_info() routine (see below).
1561
1562Data will be decoded into the supplied row buffers packed into bytes
1563unless the library has been told to transform it into another format.
1564For example, 4 bit/pixel paletted or grayscale data will be returned
15652 pixels/byte with the leftmost pixel in the high-order bits of the
1566byte, unless png_set_packing() is called. 8-bit RGB data will be stored
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]1567in RGB RGB RGB format unless png_set_filler() or png_set_add_alpha()
1568is called to insert filler bytes, either before or after each RGB triplet.
156916-bit RGB data will be returned RRGGBB RRGGBB, with the most significant
1570byte of the color value first, unless png_set_strip_16() is called to
Glenn Randers-Pehrson16e11662004-11-01 14:13:40 -0600[diff] [blame]1571transform it to regular RGB RGB triplets, or png_set_filler() or
1572png_set_add alpha() is called to insert filler bytes, either before or
1573after each RRGGBB triplet. Similarly, 8-bit or 16-bit grayscale data can
1574be modified with
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]1575png_set_filler(), png_set_add_alpha(), or png_set_strip_16().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1576
1577The following code transforms grayscale images of less than 8 to 8 bits,
1578changes paletted images to RGB, and adds a full alpha channel if there is
1579transparency information in a tRNS chunk. This is most useful on
1580grayscale images with bit depths of 2 or 4 or if there is a multiple-image
1581viewing application that wishes to treat all images in the same way.
1582
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]1583 if (color_type == PNG_COLOR_TYPE_PALETTE)
1584 png_set_palette_to_rgb(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1585
1586 if (color_type == PNG_COLOR_TYPE_GRAY &&
Glenn Randers-Pehrson1ce08362006-03-08 23:35:59 -0600[diff] [blame]1587 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]1588
1589 if (png_get_valid(png_ptr, info_ptr,
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]1590 PNG_INFO_tRNS)) png_set_tRNS_to_alpha(png_ptr);
1591
1592These three functions are actually aliases for png_set_expand(), added
1593in libpng version 1.0.4, with the function names expanded to improve code
1594readability. In some future version they may actually do different
1595things.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1596
Glenn Randers-Pehrson1ce08362006-03-08 23:35:59 -0600[diff] [blame]1597As of libpng version 1.2.9, png_set_expand_gray_1_2_4_to_8() was
1598added. It expands the sample depth without changing tRNS to alpha.
Glenn Randers-Pehrson1ce08362006-03-08 23:35:59 -0600[diff] [blame]1599
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1600PNG can have files with 16 bits per channel. If you only can handle
16018 bits per channel, this will strip the pixels down to 8 bit.
1602
1603 if (bit_depth == 16)
1604 png_set_strip_16(png_ptr);
1605
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1606If, for some reason, you don't need the alpha channel on an image,
1607and you want to remove it rather than combining it with the background
1608(but the image author certainly had in mind that you *would* combine
1609it with the background, so that's what you should probably do):
1610
1611 if (color_type & PNG_COLOR_MASK_ALPHA)
1612 png_set_strip_alpha(png_ptr);
1613
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1614In PNG files, the alpha channel in an image
1615is the level of opacity. If you need the alpha channel in an image to
1616be the level of transparency instead of opacity, you can invert the
1617alpha channel (or the tRNS chunk data) after it's read, so that 0 is
1618fully opaque and 255 (in 8-bit or paletted images) or 65535 (in 16-bit
1619images) is fully transparent, with
1620
1621 png_set_invert_alpha(png_ptr);
1622
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1623PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
1624they can, resulting in, for example, 8 pixels per byte for 1 bit
1625files. This code expands to 1 pixel per byte without changing the
1626values of the pixels:
1627
1628 if (bit_depth < 8)
1629 png_set_packing(png_ptr);
1630
1631PNG files have possible bit depths of 1, 2, 4, 8, and 16. All pixels
1632stored in a PNG image have been "scaled" or "shifted" up to the next
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1633higher possible bit depth (e.g. from 5 bits/sample in the range [0,31] to
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]16348 bits/sample in the range [0, 255]). However, it is also possible to
1635convert the PNG pixel data back to the original bit depth of the image.
1636This call reduces the pixels back down to the original bit depth:
1637
Glenn Randers-Pehrson1ea0ff32001-08-07 22:25:59 -0500[diff] [blame]1638 png_color_8p sig_bit;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1639
1640 if (png_get_sBIT(png_ptr, info_ptr, &sig_bit))
1641 png_set_shift(png_ptr, sig_bit);
1642
1643PNG files store 3-color pixels in red, green, blue order. This code
1644changes the storage of the pixels to blue, green, red:
1645
1646 if (color_type == PNG_COLOR_TYPE_RGB ||
1647 color_type == PNG_COLOR_TYPE_RGB_ALPHA)
1648 png_set_bgr(png_ptr);
1649
Glenn Randers-Pehrson1b8e5672001-08-25 06:46:06 -0500[diff] [blame]1650PNG files store RGB pixels packed into 3 or 6 bytes. This code expands them
1651into 4 or 8 bytes for windowing systems that need them in this format:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1652
Glenn Randers-Pehrson1b8e5672001-08-25 06:46:06 -0500[diff] [blame]1653 if (color_type == PNG_COLOR_TYPE_RGB)
1654 png_set_filler(png_ptr, filler, PNG_FILLER_BEFORE);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1655
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]1656where "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]1657either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether
1658you want the filler before the RGB or after. This transformation
Glenn Randers-Pehrson1b8e5672001-08-25 06:46:06 -0500[diff] [blame]1659does not affect images that already have full alpha channels. To add an
1660opaque alpha channel, use filler=0xff or 0xffff and PNG_FILLER_AFTER which
1661will generate RGBA pixels.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1662
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]1663Note that png_set_filler() does not change the color type. If you want
1664to do that, you can add a true alpha channel with
1665
1666 if (color_type == PNG_COLOR_TYPE_RGB ||
1667 color_type == PNG_COLOR_TYPE_GRAY)
1668 png_set_add_alpha(png_ptr, filler, PNG_FILLER_AFTER);
1669
1670where "filler" contains the alpha value to assign to each pixel.
Glenn Randers-Pehrson16e11662004-11-01 14:13:40 -0600[diff] [blame]1671This function was added in libpng-1.2.7.
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]1672
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1673If you are reading an image with an alpha channel, and you need the
1674data as ARGB instead of the normal PNG format RGBA:
1675
1676 if (color_type == PNG_COLOR_TYPE_RGB_ALPHA)
1677 png_set_swap_alpha(png_ptr);
1678
1679For some uses, you may want a grayscale image to be represented as
1680RGB. This code will do that conversion:
1681
1682 if (color_type == PNG_COLOR_TYPE_GRAY ||
1683 color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
1684 png_set_gray_to_rgb(png_ptr);
1685
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1686Conversely, you can convert an RGB or RGBA image to grayscale or grayscale
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1687with alpha.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1688
1689 if (color_type == PNG_COLOR_TYPE_RGB ||
1690 color_type == PNG_COLOR_TYPE_RGB_ALPHA)
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1691 png_set_rgb_to_gray_fixed(png_ptr, error_action,
1692 int red_weight, int green_weight);
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1693
1694 error_action = 1: silently do the conversion
1695 error_action = 2: issue a warning if the original
1696 image has any pixel where
1697 red != green or red != blue
1698 error_action = 3: issue an error and abort the
1699 conversion if the original
1700 image has any pixel where
1701 red != green or red != blue
1702
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1703 red_weight: weight of red component times 100000
1704 green_weight: weight of green component times 100000
1705 If either weight is negative, default
1706 weights (21268, 71514) are used.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1707
1708If you have set error_action = 1 or 2, you can
1709later check whether the image really was gray, after processing
1710the image rows, with the png_get_rgb_to_gray_status(png_ptr) function.
1711It will return a png_byte that is zero if the image was gray or
17121 if there were any non-gray pixels. bKGD and sBIT data
1713will be silently converted to grayscale, using the green channel
1714data, regardless of the error_action setting.
1715
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1716With red_weight+green_weight<=100000,
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1717the normalized graylevel is computed:
1718
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1719 int rw = red_weight * 65536;
1720 int gw = green_weight * 65536;
1721 int bw = 65536 - (rw + gw);
1722 gray = (rw*red + gw*green + bw*blue)/65536;
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1723
1724The default values approximate those recommended in the Charles
1725Poynton's Color FAQ, <http://www.inforamp.net/~poynton/>
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]1726Copyright (c) 1998-01-04 Charles Poynton <poynton at inforamp.net>
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1727
1728 Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
1729
1730Libpng approximates this with
1731
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1732 Y = 0.21268 * R + 0.7151 * G + 0.07217 * B
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1733
1734which can be expressed with integers as
1735
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1736 Y = (6969 * R + 23434 * G + 2365 * B)/32768
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1737
1738The calculation is done in a linear colorspace, if the image gamma
1739is known.
1740
Glenn Randers-Pehrson73d57cb2002-03-25 18:49:08 -0600[diff] [blame]1741If you have a grayscale and you are using png_set_expand_depth(),
1742png_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]1743a higher bit-depth, you must either supply the background color as a gray
1744value at the original file bit-depth (need_expand = 1) or else supply the
1745background color as an RGB triplet at the final, expanded bit depth
1746(need_expand = 0). Similarly, if you are reading a paletted image, you
1747must either supply the background color as a palette index (need_expand = 1)
1748or 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]1749
1750 png_color_16 my_background;
1751 png_color_16p image_background;
1752
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]1753 if (png_get_bKGD(png_ptr, info_ptr, &image_background))
1754 png_set_background(png_ptr, image_background,
1755 PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1756 else
1757 png_set_background(png_ptr, &my_background,
1758 PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
1759
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]1760The png_set_background() function tells libpng to composite images
1761with alpha or simple transparency against the supplied background
1762color. If the PNG file contains a bKGD chunk (PNG_INFO_bKGD valid),
1763you may use this color, or supply another color more suitable for
1764the current display (e.g., the background color from a web page). You
1765need to tell libpng whether the color is in the gamma space of the
1766display (PNG_BACKGROUND_GAMMA_SCREEN for colors you supply), the file
1767(PNG_BACKGROUND_GAMMA_FILE for colors from the bKGD chunk), or one
1768that is neither of these gammas (PNG_BACKGROUND_GAMMA_UNIQUE - I don't
1769know why anyone would use this, but it's here).
1770
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1771To properly display PNG images on any kind of system, the application needs
1772to know what the display gamma is. Ideally, the user will know this, and
1773the application will allow them to set it. One method of allowing the user
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]1774to set the display gamma separately for each system is to check for a
1775SCREEN_GAMMA or DISPLAY_GAMMA environment variable, which will hopefully be
1776correctly set.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1777
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]1778Note that display_gamma is the overall gamma correction required to produce
1779pleasing results, which depends on the lighting conditions in the surrounding
1780environment. In a dim or brightly lit room, no compensation other than
1781the physical gamma exponent of the monitor is needed, while in a dark room
1782a slightly smaller exponent is better.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1783
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]1784 double gamma, screen_gamma;
1785
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1786 if (/* We have a user-defined screen
1787 gamma value */)
1788 {
1789 screen_gamma = user_defined_screen_gamma;
1790 }
1791 /* One way that applications can share the same
1792 screen gamma value */
1793 else if ((gamma_str = getenv("SCREEN_GAMMA"))
1794 != NULL)
1795 {
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]1796 screen_gamma = (double)atof(gamma_str);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1797 }
1798 /* If we don't have another value */
1799 else
1800 {
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1801 screen_gamma = 2.2; /* A good guess for a
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1802 PC monitor in a bright office or a dim room */
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1803 screen_gamma = 2.0; /* A good guess for a
1804 PC monitor in a dark room */
1805 screen_gamma = 1.7 or 1.0; /* A good
1806 guess for Mac systems */
1807 }
1808
1809The png_set_gamma() function handles gamma transformations of the data.
1810Pass both the file gamma and the current screen_gamma. If the file does
1811not 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]1812it 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]1813that file gammas are inverted from screen gammas. See the discussions
1814on gamma in the PNG specification for an excellent description of what
1815gamma is, and why all applications should support it. It is strongly
1816recommended that PNG viewers support gamma correction.
1817
1818 if (png_get_gAMA(png_ptr, info_ptr, &gamma))
1819 png_set_gamma(png_ptr, screen_gamma, gamma);
1820 else
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1821 png_set_gamma(png_ptr, screen_gamma, 0.45455);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1822
1823If you need to reduce an RGB file to a paletted file, or if a paletted
1824file has more entries then will fit on your screen, png_set_dither()
1825will do that. Note that this is a simple match dither that merely
1826finds the closest color available. This should work fairly well with
1827optimized palettes, and fairly badly with linear color cubes. If you
1828pass a palette that is larger then maximum_colors, the file will
1829reduce the number of colors in the palette so it will fit into
1830maximum_colors. If there is a histogram, it will use it to make
1831more intelligent choices when reducing the palette. If there is no
1832histogram, it may not do as good a job.
1833
1834 if (color_type & PNG_COLOR_MASK_COLOR)
1835 {
1836 if (png_get_valid(png_ptr, info_ptr,
1837 PNG_INFO_PLTE))
1838 {
Glenn Randers-Pehrson865f4f02002-09-15 20:30:38 -0500[diff] [blame]1839 png_uint_16p histogram = NULL;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1840
1841 png_get_hIST(png_ptr, info_ptr,
1842 &histogram);
1843 png_set_dither(png_ptr, palette, num_palette,
1844 max_screen_colors, histogram, 1);
1845 }
1846 else
1847 {
1848 png_color std_color_cube[MAX_SCREEN_COLORS] =
1849 { ... colors ... };
1850
1851 png_set_dither(png_ptr, std_color_cube,
1852 MAX_SCREEN_COLORS, MAX_SCREEN_COLORS,
1853 NULL,0);
1854 }
1855 }
1856
1857PNG files describe monochrome as black being zero and white being one.
1858The following code will reverse this (make black be one and white be
1859zero):
1860
Glenn Randers-Pehrson1ea0ff32001-08-07 22:25:59 -0500[diff] [blame]1861 if (bit_depth == 1 && color_type == PNG_COLOR_TYPE_GRAY)
1862 png_set_invert_mono(png_ptr);
1863
1864This function can also be used to invert grayscale and gray-alpha images:
1865
1866 if (color_type == PNG_COLOR_TYPE_GRAY ||
1867 color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1868 png_set_invert_mono(png_ptr);
1869
1870PNG files store 16 bit pixels in network byte order (big-endian,
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1871ie. most significant bits first). This code changes the storage to the
1872other way (little-endian, i.e. least significant bits first, the
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1873way PCs store them):
1874
1875 if (bit_depth == 16)
1876 png_set_swap(png_ptr);
1877
1878If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you
1879need to change the order the pixels are packed into bytes, you can use:
1880
1881 if (bit_depth < 8)
1882 png_set_packswap(png_ptr);
1883
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1884Finally, you can write your own transformation function if none of
1885the existing ones meets your needs. This is done by setting a callback
1886with
1887
1888 png_set_read_user_transform_fn(png_ptr,
1889 read_transform_fn);
1890
1891You must supply the function
1892
1893 void read_transform_fn(png_ptr ptr, row_info_ptr
1894 row_info, png_bytep data)
1895
1896See pngtest.c for a working example. Your function will be called
1897after all of the other transformations have been processed.
1898
1899You can also set up a pointer to a user structure for use by your
1900callback function, and you can inform libpng that your transform
1901function will change the number of channels or bit depth with the
1902function
1903
1904 png_set_user_transform_info(png_ptr, user_ptr,
1905 user_depth, user_channels);
1906
1907The user's application, not libpng, is responsible for allocating and
1908freeing any memory required for the user structure.
1909
1910You can retrieve the pointer via the function
1911png_get_user_transform_ptr(). For example:
1912
1913 voidp read_user_transform_ptr =
1914 png_get_user_transform_ptr(png_ptr);
1915
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1916The last thing to handle is interlacing; this is covered in detail below,
1917but you must call the function here if you want libpng to handle expansion
1918of the interlaced image.
1919
1920 number_of_passes = png_set_interlace_handling(png_ptr);
1921
1922After setting the transformations, libpng can update your png_info
1923structure to reflect any transformations you've requested with this
1924call. This is most useful to update the info structure's rowbytes
1925field so you can use it to allocate your image memory. This function
1926will also update your palette with the correct screen_gamma and
1927background if these have been given with the calls above.
1928
1929 png_read_update_info(png_ptr, info_ptr);
1930
1931After you call png_read_update_info(), you can allocate any
1932memory you need to hold the image. The row data is simply
1933raw byte data for all forms of images. As the actual allocation
1934varies among applications, no example will be given. If you
1935are allocating one large chunk, you will need to build an
1936array of pointers to each row, as it will be needed for some
1937of the functions below.
1938
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1939.SS Reading image data
1940
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1941After you've allocated memory, you can read the image data.
1942The simplest way to do this is in one function call. If you are
1943allocating enough memory to hold the whole image, you can just
1944call png_read_image() and libpng will read in all the image data
1945and put it in the memory area supplied. You will need to pass in
1946an array of pointers to each row.
1947
1948This function automatically handles interlacing, so you don't need
1949to call png_set_interlace_handling() or call this function multiple
1950times, or any of that other stuff necessary with png_read_rows().
1951
1952 png_read_image(png_ptr, row_pointers);
1953
1954where row_pointers is:
1955
1956 png_bytep row_pointers[height];
1957
1958You can point to void or char or whatever you use for pixels.
1959
1960If you don't want to read in the whole image at once, you can
1961use png_read_rows() instead. If there is no interlacing (check
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1962interlace_type == PNG_INTERLACE_NONE), this is simple:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1963
1964 png_read_rows(png_ptr, row_pointers, NULL,
1965 number_of_rows);
1966
1967where row_pointers is the same as in the png_read_image() call.
1968
1969If 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]1970a single row_pointer instead of an array of row_pointers:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1971
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1972 png_bytep row_pointer = row;
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]1973 png_read_row(png_ptr, row_pointer, NULL);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1974
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1975If the file is interlaced (interlace_type != 0 in the IHDR chunk), things
1976get somewhat harder. The only current (PNG Specification version 1.2)
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1977interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1978is a somewhat complicated 2D interlace scheme, known as Adam7, that
1979breaks down an image into seven smaller images of varying size, based
1980on an 8x8 grid.
1981
1982libpng can fill out those images or it can give them to you "as is".
1983If you want them filled out, there are two ways to do that. The one
1984mentioned in the PNG specification is to expand each pixel to cover
1985those pixels that have not been read yet (the "rectangle" method).
1986This results in a blocky image for the first pass, which gradually
1987smooths out as more pixels are read. The other method is the "sparkle"
1988method, where pixels are drawn only in their final locations, with the
1989rest of the image remaining whatever colors they were initialized to
1990before the start of the read. The first method usually looks better,
1991but tends to be slower, as there are more pixels to put in the rows.
1992
1993If you don't want libpng to handle the interlacing details, just call
1994png_read_rows() seven times to read in all seven images. Each of the
1995images is a valid image by itself, or they can all be combined on an
19968x8 grid to form a single image (although if you intend to combine them
1997you would be far better off using the libpng interlace handling).
1998
1999The first pass will return an image 1/8 as wide as the entire image
2000(every 8th column starting in column 0) and 1/8 as high as the original
2001(every 8th row starting in row 0), the second will be 1/8 as wide
2002(starting in column 4) and 1/8 as high (also starting in row 0). The
2003third pass will be 1/4 as wide (every 4th pixel starting in column 0) and
20041/8 as high (every 8th row starting in row 4), and the fourth pass will
2005be 1/4 as wide and 1/4 as high (every 4th column starting in column 2,
2006and every 4th row starting in row 0). The fifth pass will return an
2007image 1/2 as wide, and 1/4 as high (starting at column 0 and row 2),
2008while the sixth pass will be 1/2 as wide and 1/2 as high as the original
2009(starting in column 1 and row 0). The seventh and final pass will be as
2010wide as the original, and 1/2 as high, containing all of the odd
2011numbered scanlines. Phew!
2012
2013If you want libpng to expand the images, call this before calling
2014png_start_read_image() or png_read_update_info():
2015
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2016 if (interlace_type == PNG_INTERLACE_ADAM7)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2017 number_of_passes
2018 = png_set_interlace_handling(png_ptr);
2019
2020This will return the number of passes needed. Currently, this
2021is seven, but may change if another interlace type is added.
2022This function can be called even if the file is not interlaced,
2023where it will return one pass.
2024
2025If you are not going to display the image after each pass, but are
2026going to wait until the entire image is read in, use the sparkle
2027effect. This effect is faster and the end result of either method
2028is exactly the same. If you are planning on displaying the image
2029after each pass, the "rectangle" effect is generally considered the
2030better looking one.
2031
2032If you only want the "sparkle" effect, just call png_read_rows() as
2033normal, with the third parameter NULL. Make sure you make pass over
2034the image number_of_passes times, and you don't change the data in the
2035rows between calls. You can change the locations of the data, just
2036not the data. Each pass only writes the pixels appropriate for that
2037pass, and assumes the data from previous passes is still valid.
2038
2039 png_read_rows(png_ptr, row_pointers, NULL,
2040 number_of_rows);
2041
2042If you only want the first effect (the rectangles), do the same as
2043before except pass the row buffer in the third parameter, and leave
2044the second parameter NULL.
2045
2046 png_read_rows(png_ptr, NULL, row_pointers,
2047 number_of_rows);
2048
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2049.SS Finishing a sequential read
2050
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]2051After you are finished reading the image through the
2052low-level interface, you can finish reading the file. If you are
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2053interested in comments or time, which may be stored either before or
2054after the image data, you should pass the separate png_info struct if
2055you want to keep the comments from before and after the image
2056separate. If you are not interested, you can pass NULL.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2057
2058 png_read_end(png_ptr, end_info);
2059
2060When you are done, you can free all memory allocated by libpng like this:
2061
2062 png_destroy_read_struct(&png_ptr, &info_ptr,
2063 &end_info);
2064
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2065It is also possible to individually free the info_ptr members that
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2066point to libpng-allocated storage with the following function:
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2067
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2068 png_free_data(png_ptr, info_ptr, mask, seq)
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2069 mask - identifies data to be freed, a mask
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]2070 containing the bitwise OR of one or
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2071 more of
2072 PNG_FREE_PLTE, PNG_FREE_TRNS,
2073 PNG_FREE_HIST, PNG_FREE_ICCP,
2074 PNG_FREE_PCAL, PNG_FREE_ROWS,
2075 PNG_FREE_SCAL, PNG_FREE_SPLT,
2076 PNG_FREE_TEXT, PNG_FREE_UNKN,
2077 or simply PNG_FREE_ALL
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2078 seq - sequence number of item to be freed
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2079 (-1 for all items)
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2080
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2081This function may be safely called when the relevant storage has
Glenn Randers-Pehrson68ea2432000-04-01 21:10:05 -0600[diff] [blame]2082already been freed, or has not yet been allocated, or was allocated
2083by the user and not by libpng, and will in those
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2084cases do nothing. The "seq" parameter is ignored if only one item
2085of the selected data type, such as PLTE, is allowed. If "seq" is not
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]2086-1, and multiple items are allowed for the data type identified in
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2087the mask, such as text or sPLT, only the n'th item in the structure
2088is freed, where n is "seq".
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2089
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2090The default behavior is only to free data that was allocated internally
2091by libpng. This can be changed, so that libpng will not free the data,
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2092or so that it will free data that was allocated by the user with png_malloc()
2093or png_zalloc() and passed in via a png_set_*() function, with
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2094
2095 png_data_freer(png_ptr, info_ptr, freer, mask)
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2096 mask - which data elements are affected
2097 same choices as in png_free_data()
2098 freer - one of
2099 PNG_DESTROY_WILL_FREE_DATA
2100 PNG_SET_WILL_FREE_DATA
2101 PNG_USER_WILL_FREE_DATA
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2102
2103This function only affects data that has already been allocated.
2104You can call this function after reading the PNG data but before calling
2105any png_set_*() functions, to control whether the user or the png_set_*()
2106function is responsible for freeing any existing data that might be present,
2107and again after the png_set_*() functions to control whether the user
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2108or png_destroy_*() is supposed to free the data. When the user assumes
2109responsibility for libpng-allocated data, the application must use
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2110png_free() to free it, and when the user transfers responsibility to libpng
2111for data that the user has allocated, the user must have used png_malloc()
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame]2112or png_zalloc() to allocate it.
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2113
2114If you allocated your row_pointers in a single block, as suggested above in
2115the description of the high level read interface, you must not transfer
2116responsibility for freeing it to the png_set_rows or png_read_destroy function,
2117because they would also try to free the individual row_pointers[i].
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2118
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2119If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword
2120separately, do not transfer responsibility for freeing text_ptr to libpng,
2121because when libpng fills a png_text structure it combines these members with
2122the key member, and png_free_data() will free only text_ptr.key. Similarly,
2123if you transfer responsibility for free'ing text_ptr from libpng to your
2124application, your application must not separately free those members.
2125
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2126The png_free_data() function will turn off the "valid" flag for anything
2127it frees. If you need to turn the flag off for a chunk that was freed by your
2128application instead of by libpng, you can use
2129
2130 png_set_invalid(png_ptr, info_ptr, mask);
2131 mask - identifies the chunks to be made invalid,
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]2132 containing the bitwise OR of one or
Glenn Randers-Pehrsond56aca72000-11-23 11:51:42 -0600[diff] [blame]2133 more of
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2134 PNG_INFO_gAMA, PNG_INFO_sBIT,
2135 PNG_INFO_cHRM, PNG_INFO_PLTE,
2136 PNG_INFO_tRNS, PNG_INFO_bKGD,
2137 PNG_INFO_hIST, PNG_INFO_pHYs,
2138 PNG_INFO_oFFs, PNG_INFO_tIME,
2139 PNG_INFO_pCAL, PNG_INFO_sRGB,
2140 PNG_INFO_iCCP, PNG_INFO_sPLT,
2141 PNG_INFO_sCAL, PNG_INFO_IDAT
2142
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2143For a more compact example of reading a PNG image, see the file example.c.
2144
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2145.SS Reading PNG files progressively
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2146
2147The progressive reader is slightly different then the non-progressive
2148reader. Instead of calling png_read_info(), png_read_rows(), and
2149png_read_end(), you make one call to png_process_data(), which calls
2150callbacks when it has the info, a row, or the end of the image. You
2151set up these callbacks with png_set_progressive_read_fn(). You don't
2152have to worry about the input/output functions of libpng, as you are
2153giving the library the data directly in png_process_data(). I will
2154assume that you have read the section on reading PNG files above,
2155so I will only highlight the differences (although I will show
2156all of the code).
2157
2158png_structp png_ptr;
2159png_infop info_ptr;
2160
2161 /* An example code fragment of how you would
2162 initialize the progressive reader in your
2163 application. */
2164 int
2165 initialize_png_reader()
2166 {
2167 png_ptr = png_create_read_struct
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]2168 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2169 user_error_fn, user_warning_fn);
2170 if (!png_ptr)
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2171 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2172 info_ptr = png_create_info_struct(png_ptr);
2173 if (!info_ptr)
2174 {
2175 png_destroy_read_struct(&png_ptr, (png_infopp)NULL,
2176 (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2177 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2178 }
2179
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2180 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2181 {
2182 png_destroy_read_struct(&png_ptr, &info_ptr,
2183 (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2184 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2185 }
2186
2187 /* This one's new. You can provide functions
2188 to be called when the header info is valid,
2189 when each row is completed, and when the image
2190 is finished. If you aren't using all functions,
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2191 you can specify NULL parameters. Even when all
2192 three functions are NULL, you need to call
2193 png_set_progressive_read_fn(). You can use
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2194 any struct as the user_ptr (cast to a void pointer
2195 for the function call), and retrieve the pointer
2196 from inside the callbacks using the function
2197
2198 png_get_progressive_ptr(png_ptr);
2199
2200 which will return a void pointer, which you have
2201 to cast appropriately.
2202 */
2203 png_set_progressive_read_fn(png_ptr, (void *)user_ptr,
2204 info_callback, row_callback, end_callback);
2205
2206 return 0;
2207 }
2208
2209 /* A code fragment that you call as you receive blocks
2210 of data */
2211 int
2212 process_data(png_bytep buffer, png_uint_32 length)
2213 {
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2214 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2215 {
2216 png_destroy_read_struct(&png_ptr, &info_ptr,
2217 (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2218 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2219 }
2220
2221 /* This one's new also. Simply give it a chunk
2222 of data from the file stream (in order, of
2223 course). On machines with segmented memory
2224 models machines, don't give it any more than
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2225 64K. The library seems to run fine with sizes
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2226 of 4K. Although you can give it much less if
2227 necessary (I assume you can give it chunks of
2228 1 byte, I haven't tried less then 256 bytes
2229 yet). When this function returns, you may
2230 want to display any rows that were generated
2231 in the row callback if you don't already do
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2232 so there.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2233 */
2234 png_process_data(png_ptr, info_ptr, buffer, length);
2235 return 0;
2236 }
2237
2238 /* This function is called (as set by
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2239 png_set_progressive_read_fn() above) when enough data
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2240 has been supplied so all of the header has been
2241 read.
2242 */
2243 void
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2244 info_callback(png_structp png_ptr, png_infop info)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2245 {
2246 /* Do any setup here, including setting any of
2247 the transformations mentioned in the Reading
2248 PNG files section. For now, you _must_ call
2249 either png_start_read_image() or
2250 png_read_update_info() after all the
2251 transformations are set (even if you don't set
2252 any). You may start getting rows before
2253 png_process_data() returns, so this is your
2254 last chance to prepare for that.
2255 */
2256 }
2257
2258 /* This function is called when each row of image
2259 data is complete */
2260 void
2261 row_callback(png_structp png_ptr, png_bytep new_row,
Glenn Randers-Pehrsone68f5a32001-05-14 09:20:53 -0500[diff] [blame]2262 png_uint_32 row_num, int pass)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2263 {
2264 /* If the image is interlaced, and you turned
2265 on the interlace handler, this function will
2266 be called for every row in every pass. Some
2267 of these rows will not be changed from the
2268 previous pass. When the row is not changed,
2269 the new_row variable will be NULL. The rows
2270 and passes are called in order, so you don't
2271 really need the row_num and pass, but I'm
2272 supplying them because it may make your life
2273 easier.
2274
2275 For the non-NULL rows of interlaced images,
2276 you must call png_progressive_combine_row()
2277 passing in the row and the old row. You can
2278 call this function for NULL rows (it will just
2279 return) and for non-interlaced images (it just
2280 does the memcpy for you) if it will make the
2281 code easier. Thus, you can just do this for
2282 all cases:
2283 */
2284
2285 png_progressive_combine_row(png_ptr, old_row,
2286 new_row);
2287
2288 /* where old_row is what was displayed for
Glenn Randers-Pehrson345bc271998-06-14 14:43:31 -0500[diff] [blame]2289 previously for the row. Note that the first
2290 pass (pass == 0, really) will completely cover
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2291 the old row, so the rows do not have to be
2292 initialized. After the first pass (and only
2293 for interlaced images), you will have to pass
2294 the current row, and the function will combine
2295 the old row and the new row.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2296 */
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2297 }
2298
2299 void
2300 end_callback(png_structp png_ptr, png_infop info)
2301 {
2302 /* This function is called after the whole image
2303 has been read, including any chunks after the
2304 image (up to and including the IEND). You
2305 will usually have the same info chunk as you
2306 had in the header, although some data may have
2307 been added to the comments and time fields.
2308
2309 Most people won't do much here, perhaps setting
2310 a flag that marks the image as finished.
2311 */
2312 }
2313
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]2314
2315
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2316.SH IV. Writing
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2317
2318Much of this is very similar to reading. However, everything of
2319importance is repeated here, so you won't have to constantly look
2320back up in the reading section to understand writing.
2321
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2322.SS Setup
2323
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2324You will want to do the I/O initialization before you get into libpng,
2325so if it doesn't work, you don't have anything to undo. If you are not
2326using the standard I/O functions, you will need to replace them with
2327custom writing functions. See the discussion under Customizing libpng.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2328
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2329 FILE *fp = fopen(file_name, "wb");
2330 if (!fp)
2331 {
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2332 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2333 }
2334
2335Next, png_struct and png_info need to be allocated and initialized.
2336As these can be both relatively large, you may not want to store these
2337on the stack, unless you have stack space to spare. Of course, you
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2338will want to check if they return NULL. If you are also reading,
2339you won't want to name your read structure and your write structure
2340both "png_ptr"; you can call them anything you like, such as
2341"read_ptr" and "write_ptr". Look at pngtest.c, for example.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2342
2343 png_structp png_ptr = png_create_write_struct
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]2344 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2345 user_error_fn, user_warning_fn);
2346 if (!png_ptr)
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2347 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2348
2349 png_infop info_ptr = png_create_info_struct(png_ptr);
2350 if (!info_ptr)
2351 {
2352 png_destroy_write_struct(&png_ptr,
2353 (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2354 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2355 }
2356
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]2357If you want to use your own memory allocation routines,
2358define PNG_USER_MEM_SUPPORTED and use
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2359png_create_write_struct_2() instead of png_create_write_struct():
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]2360
2361 png_structp png_ptr = png_create_write_struct_2
2362 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
2363 user_error_fn, user_warning_fn, (png_voidp)
2364 user_mem_ptr, user_malloc_fn, user_free_fn);
2365
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2366After you have these structures, you will need to set up the
2367error handling. When libpng encounters an error, it expects to
2368longjmp() back to your routine. Therefore, you will need to call
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2369setjmp() and pass the png_jmpbuf(png_ptr). If you
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2370write the file from different routines, you will need to update
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2371the png_jmpbuf(png_ptr) every time you enter a new routine that will
2372call a png_*() function. See your documentation of setjmp/longjmp
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2373for your compiler for more information on setjmp/longjmp. See
2374the discussion on libpng error handling in the Customizing Libpng
2375section below for more information on the libpng error handling.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2376
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2377 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2378 {
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2379 png_destroy_write_struct(&png_ptr, &info_ptr);
2380 fclose(fp);
2381 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2382 }
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2383 ...
2384 return;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2385
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2386If you would rather avoid the complexity of setjmp/longjmp issues,
2387you can compile libpng with PNG_SETJMP_NOT_SUPPORTED, in which case
2388errors will result in a call to PNG_ABORT() which defaults to abort().
2389
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2390Now you need to set up the output code. The default for libpng is to
2391use the C function fwrite(). If you use this, you will need to pass a
2392valid FILE * in the function png_init_io(). Be sure that the file is
2393opened in binary mode. Again, if you wish to handle writing data in
2394another way, see the discussion on libpng I/O handling in the Customizing
2395Libpng section below.
2396
2397 png_init_io(png_ptr, fp);
2398
Glenn Randers-Pehrsond60b8fa2006-04-20 21:31:14 -0500[diff] [blame]2399If you are embedding your PNG into a datastream such as MNG, and don't
2400want libpng to write the 8-byte signature, or if you have already
2401written the signature in your application, use
2402
2403 png_set_sig_bytes(png_ptr, 8);
2404
2405to inform libpng that it should not write a signature.
2406
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2407.SS Write callbacks
2408
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2409At this point, you can set up a callback function that will be
2410called after each row has been written, which you can use to control
2411a progress meter or the like. It's demonstrated in pngtest.c.
2412You must supply a function
2413
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2414 void write_row_callback(png_ptr, png_uint_32 row,
2415 int pass);
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2416 {
2417 /* put your code here */
2418 }
2419
2420(You can give it another name that you like instead of "write_row_callback")
2421
2422To inform libpng about your function, use
2423
2424 png_set_write_status_fn(png_ptr, write_row_callback);
2425
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2426You now have the option of modifying how the compression library will
2427run. The following functions are mainly for testing, but may be useful
2428in some cases, like if you need to write PNG files extremely fast and
2429are willing to give up some compression, or if you want to get the
2430maximum possible compression at the expense of slower writing. If you
2431have no special needs in this area, let the library do what it wants by
2432not calling this function at all, as it has been tuned to deliver a good
2433speed/compression ratio. The second parameter to png_set_filter() is
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]2434the filter method, for which the only valid values are 0 (as of the
2435July 1999 PNG specification, version 1.2) or 64 (if you are writing
2436a PNG datastream that is to be embedded in a MNG datastream). The third
2437parameter is a flag that indicates which filter type(s) are to be tested
2438for each scanline. See the PNG specification for details on the specific filter
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]2439types.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2440
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2441
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2442 /* turn on or off filtering, and/or choose
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2443 specific filters. You can use either a single
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]2444 PNG_FILTER_VALUE_NAME or the bitwise OR of one
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2445 or more PNG_FILTER_NAME masks. */
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2446 png_set_filter(png_ptr, 0,
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2447 PNG_FILTER_NONE | PNG_FILTER_VALUE_NONE |
2448 PNG_FILTER_SUB | PNG_FILTER_VALUE_SUB |
2449 PNG_FILTER_UP | PNG_FILTER_VALUE_UP |
2450 PNG_FILTER_AVE | PNG_FILTER_VALUE_AVE |
2451 PNG_FILTER_PAETH | PNG_FILTER_VALUE_PAETH|
2452 PNG_ALL_FILTERS);
2453
2454If an application
2455wants to start and stop using particular filters during compression,
2456it should start out with all of the filters (to ensure that the previous
2457row of pixels will be stored in case it's needed later), and then add
2458and remove them after the start of compression.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2459
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]2460If you are writing a PNG datastream that is to be embedded in a MNG
2461datastream, the second parameter can be either 0 or 64.
2462
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]2463The png_set_compression_*() functions interface to the zlib compression
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2464library, and should mostly be ignored unless you really know what you are
2465doing. The only generally useful call is png_set_compression_level()
2466which changes how much time zlib spends on trying to compress the image
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2467data. See the Compression Library (zlib.h and algorithm.txt, distributed
2468with zlib) for details on the compression levels.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2469
2470 /* set the zlib compression level */
2471 png_set_compression_level(png_ptr,
2472 Z_BEST_COMPRESSION);
2473
2474 /* set other zlib parameters */
2475 png_set_compression_mem_level(png_ptr, 8);
2476 png_set_compression_strategy(png_ptr,
2477 Z_DEFAULT_STRATEGY);
2478 png_set_compression_window_bits(png_ptr, 15);
2479 png_set_compression_method(png_ptr, 8);
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2480 png_set_compression_buffer_size(png_ptr, 8192)
2481
2482extern PNG_EXPORT(void,png_set_zbuf_size)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2483
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2484.SS Setting the contents of info for output
2485
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2486You now need to fill in the png_info structure with all the data you
2487wish to write before the actual image. Note that the only thing you
2488are allowed to write after the image is the text chunks and the time
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]2489chunk (as of PNG Specification 1.2, anyway). See png_write_end() and
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2490the latest PNG specification for more information on that. If you
2491wish to write them before the image, fill them in now, and flag that
2492data as being valid. If you want to wait until after the data, don't
2493fill them until png_write_end(). For all the fields in png_info and
2494their data types, see png.h. For explanations of what the fields
2495contain, see the PNG specification.
2496
2497Some of the more important parts of the png_info are:
2498
2499 png_set_IHDR(png_ptr, info_ptr, width, height,
2500 bit_depth, color_type, interlace_type,
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]2501 compression_type, filter_method)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2502 width - holds the width of the image
2503 in pixels (up to 2^31).
2504 height - holds the height of the image
2505 in pixels (up to 2^31).
2506 bit_depth - holds the bit depth of one of the
2507 image channels.
2508 (valid values are 1, 2, 4, 8, 16
2509 and depend also on the
2510 color_type. See also significant
2511 bits (sBIT) below).
2512 color_type - describes which color/alpha
2513 channels are present.
2514 PNG_COLOR_TYPE_GRAY
2515 (bit depths 1, 2, 4, 8, 16)
2516 PNG_COLOR_TYPE_GRAY_ALPHA
2517 (bit depths 8, 16)
2518 PNG_COLOR_TYPE_PALETTE
2519 (bit depths 1, 2, 4, 8)
2520 PNG_COLOR_TYPE_RGB
2521 (bit_depths 8, 16)
2522 PNG_COLOR_TYPE_RGB_ALPHA
2523 (bit_depths 8, 16)
2524
2525 PNG_COLOR_MASK_PALETTE
2526 PNG_COLOR_MASK_COLOR
2527 PNG_COLOR_MASK_ALPHA
2528
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2529 interlace_type - PNG_INTERLACE_NONE or
2530 PNG_INTERLACE_ADAM7
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2531 compression_type - (must be
2532 PNG_COMPRESSION_TYPE_DEFAULT)
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]2533 filter_method - (must be PNG_FILTER_TYPE_DEFAULT
2534 or, if you are writing a PNG to
2535 be embedded in a MNG datastream,
2536 can also be
2537 PNG_INTRAPIXEL_DIFFERENCING)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2538
2539 png_set_PLTE(png_ptr, info_ptr, palette,
2540 num_palette);
2541 palette - the palette for the file
2542 (array of png_color)
2543 num_palette - number of entries in the palette
2544
2545 png_set_gAMA(png_ptr, info_ptr, gamma);
2546 gamma - the gamma the image was created
2547 at (PNG_INFO_gAMA)
2548
2549 png_set_sRGB(png_ptr, info_ptr, srgb_intent);
2550 srgb_intent - the rendering intent
2551 (PNG_INFO_sRGB) The presence of
2552 the sRGB chunk means that the pixel
2553 data is in the sRGB color space.
2554 This chunk also implies specific
2555 values of gAMA and cHRM. Rendering
2556 intent is the CSS-1 property that
2557 has been defined by the International
2558 Color Consortium
2559 (http://www.color.org).
2560 It can be one of
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]2561 PNG_sRGB_INTENT_SATURATION,
2562 PNG_sRGB_INTENT_PERCEPTUAL,
2563 PNG_sRGB_INTENT_ABSOLUTE, or
2564 PNG_sRGB_INTENT_RELATIVE.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2565
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2566
2567 png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr,
2568 srgb_intent);
2569 srgb_intent - the rendering intent
2570 (PNG_INFO_sRGB) The presence of the
2571 sRGB chunk means that the pixel
2572 data is in the sRGB color space.
2573 This function also causes gAMA and
2574 cHRM chunks with the specific values
2575 that are consistent with sRGB to be
2576 written.
2577
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2578 png_set_iCCP(png_ptr, info_ptr, name, compression_type,
2579 profile, proflen);
2580 name - The profile name.
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2581 compression - The compression type; always
2582 PNG_COMPRESSION_TYPE_BASE for PNG 1.0.
2583 You may give NULL to this argument to
2584 ignore it.
2585 profile - International Color Consortium color
2586 profile data. May contain NULs.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2587 proflen - length of profile data in bytes.
2588
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2589 png_set_sBIT(png_ptr, info_ptr, sig_bit);
2590 sig_bit - the number of significant bits for
2591 (PNG_INFO_sBIT) each of the gray, red,
2592 green, and blue channels, whichever are
2593 appropriate for the given color type
2594 (png_color_16)
2595
2596 png_set_tRNS(png_ptr, info_ptr, trans, num_trans,
2597 trans_values);
2598 trans - array of transparent entries for
2599 palette (PNG_INFO_tRNS)
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]2600 trans_values - graylevel or color sample values of
2601 the single transparent color for
2602 non-paletted images (PNG_INFO_tRNS)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2603 num_trans - number of transparent entries
2604 (PNG_INFO_tRNS)
2605
2606 png_set_hIST(png_ptr, info_ptr, hist);
2607 (PNG_INFO_hIST)
2608 hist - histogram of palette (array of
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2609 png_uint_16)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2610
2611 png_set_tIME(png_ptr, info_ptr, mod_time);
2612 mod_time - time image was last modified
2613 (PNG_VALID_tIME)
2614
2615 png_set_bKGD(png_ptr, info_ptr, background);
2616 background - background color (PNG_VALID_bKGD)
2617
2618 png_set_text(png_ptr, info_ptr, text_ptr, num_text);
2619 text_ptr - array of png_text holding image
2620 comments
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2621 text_ptr[i].compression - type of compression used
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2622 on "text" PNG_TEXT_COMPRESSION_NONE
2623 PNG_TEXT_COMPRESSION_zTXt
2624 PNG_ITXT_COMPRESSION_NONE
2625 PNG_ITXT_COMPRESSION_zTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2626 text_ptr[i].key - keyword for comment. Must contain
2627 1-79 characters.
2628 text_ptr[i].text - text comments for current
2629 keyword. Can be NULL or empty.
2630 text_ptr[i].text_length - length of text string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2631 after decompression, 0 for iTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2632 text_ptr[i].itxt_length - length of itxt string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2633 after decompression, 0 for tEXt/zTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2634 text_ptr[i].lang - language of comment (NULL or
2635 empty for unknown).
2636 text_ptr[i].translated_keyword - keyword in UTF-8 (NULL
2637 or empty for unknown).
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2638 num_text - number of comments
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2639
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2640 png_set_sPLT(png_ptr, info_ptr, &palette_ptr,
2641 num_spalettes);
2642 palette_ptr - array of png_sPLT_struct structures
2643 to be added to the list of palettes
2644 in the info structure.
2645 num_spalettes - number of palette structures to be
2646 added.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2647
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2648 png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y,
2649 unit_type);
2650 offset_x - positive offset from the left
2651 edge of the screen
2652 offset_y - positive offset from the top
2653 edge of the screen
2654 unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
2655
2656 png_set_pHYs(png_ptr, info_ptr, res_x, res_y,
2657 unit_type);
2658 res_x - pixels/unit physical resolution
2659 in x direction
2660 res_y - pixels/unit physical resolution
2661 in y direction
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2662 unit_type - PNG_RESOLUTION_UNKNOWN,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2663 PNG_RESOLUTION_METER
2664
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2665 png_set_sCAL(png_ptr, info_ptr, unit, width, height)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2666 unit - physical scale units (an integer)
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2667 width - width of a pixel in physical scale units
2668 height - height of a pixel in physical scale units
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2669 (width and height are doubles)
2670
2671 png_set_sCAL_s(png_ptr, info_ptr, unit, width, height)
2672 unit - physical scale units (an integer)
2673 width - width of a pixel in physical scale units
2674 height - height of a pixel in physical scale units
2675 (width and height are strings like "2.54")
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2676
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2677 png_set_unknown_chunks(png_ptr, info_ptr, &unknowns,
2678 num_unknowns)
2679 unknowns - array of png_unknown_chunk
2680 structures holding unknown chunks
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2681 unknowns[i].name - name of unknown chunk
2682 unknowns[i].data - data of unknown chunk
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2683 unknowns[i].size - size of unknown chunk's data
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2684 unknowns[i].location - position to write chunk in file
2685 0: do not write chunk
2686 PNG_HAVE_IHDR: before PLTE
2687 PNG_HAVE_PLTE: before IDAT
2688 PNG_AFTER_IDAT: after IDAT
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2689
2690The "location" member is set automatically according to
2691what part of the output file has already been written.
2692You can change its value after calling png_set_unknown_chunks()
2693as demonstrated in pngtest.c. Within each of the "locations",
2694the chunks are sequenced according to their position in the
2695structure (that is, the value of "i", which is the order in which
2696the chunk was either read from the input file or defined with
2697png_set_unknown_chunks).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2698
2699A quick word about text and num_text. text is an array of png_text
2700structures. num_text is the number of valid structures in the array.
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2701Each png_text structure holds a language code, a keyword, a text value,
2702and a compression type.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2703
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2704The compression types have the same valid numbers as the compression
2705types of the image data. Currently, the only valid number is zero.
2706However, you can store text either compressed or uncompressed, unlike
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2707images, which always have to be compressed. So if you don't want the
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2708text compressed, set the compression type to PNG_TEXT_COMPRESSION_NONE.
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2709Because tEXt and zTXt chunks don't have a language field, if you
2710specify PNG_TEXT_COMPRESSION_NONE or PNG_TEXT_COMPRESSION_zTXt
2711any language code or translated keyword will not be written out.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2712
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2713Until text gets around 1000 bytes, it is not worth compressing it.
2714After the text has been written out to the file, the compression type
2715is set to PNG_TEXT_COMPRESSION_NONE_WR or PNG_TEXT_COMPRESSION_zTXt_WR,
2716so that it isn't written out again at the end (in case you are calling
2717png_write_end() with the same struct.
2718
2719The keywords that are given in the PNG Specification are:
2720
2721 Title Short (one line) title or
2722 caption for image
2723 Author Name of image's creator
2724 Description Description of image (possibly long)
2725 Copyright Copyright notice
2726 Creation Time Time of original image creation
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2727 (usually RFC 1123 format, see below)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2728 Software Software used to create the image
2729 Disclaimer Legal disclaimer
2730 Warning Warning of nature of content
2731 Source Device used to create the image
2732 Comment Miscellaneous comment; conversion
2733 from other image format
2734
2735The keyword-text pairs work like this. Keywords should be short
2736simple descriptions of what the comment is about. Some typical
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2737keywords are found in the PNG specification, as is some recommendations
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2738on keywords. You can repeat keywords in a file. You can even write
2739some text before the image and some after. For example, you may want
2740to put a description of the image before the image, but leave the
2741disclaimer until after, so viewers working over modem connections
2742don't have to wait for the disclaimer to go over the modem before
2743they start seeing the image. Finally, keywords should be full
2744words, not abbreviations. Keywords and text are in the ISO 8859-1
2745(Latin-1) character set (a superset of regular ASCII) and can not
2746contain NUL characters, and should not contain control or other
2747unprintable characters. To make the comments widely readable, stick
2748with basic ASCII, and avoid machine specific character set extensions
2749like the IBM-PC character set. The keyword must be present, but
2750you can leave off the text string on non-compressed pairs.
2751Compressed pairs must have a text string, as only the text string
2752is compressed anyway, so the compression would be meaningless.
2753
2754PNG supports modification time via the png_time structure. Two
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2755conversion routines are provided, png_convert_from_time_t() for
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2756time_t and png_convert_from_struct_tm() for struct tm. The
2757time_t routine uses gmtime(). You don't have to use either of
2758these, but if you wish to fill in the png_time structure directly,
2759you should provide the time in universal time (GMT) if possible
2760instead of your local time. Note that the year number is the full
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2761year (e.g. 1998, rather than 98 - PNG is year 2000 compliant!), and
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2762that months start with 1.
2763
2764If you want to store the time of the original image creation, you should
2765use a plain tEXt chunk with the "Creation Time" keyword. This is
2766necessary because the "creation time" of a PNG image is somewhat vague,
2767depending on whether you mean the PNG file, the time the image was
2768created in a non-PNG format, a still photo from which the image was
2769scanned, or possibly the subject matter itself. In order to facilitate
2770machine-readable dates, it is recommended that the "Creation Time"
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2771tEXt 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]2772although this isn't a requirement. Unlike the tIME chunk, the
2773"Creation Time" tEXt chunk is not expected to be automatically changed
2774by the software. To facilitate the use of RFC 1123 dates, a function
2775png_convert_to_rfc1123(png_timep) is provided to convert from PNG
2776time to an RFC 1123 format string.
2777
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2778.SS Writing unknown chunks
2779
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2780You can use the png_set_unknown_chunks function to queue up chunks
2781for writing. You give it a chunk name, raw data, and a size; that's
2782all there is to it. The chunks will be written by the next following
2783png_write_info_before_PLTE, png_write_info, or png_write_end function.
2784Any chunks previously read into the info structure's unknown-chunk
2785list will also be written out in a sequence that satisfies the PNG
2786specification's ordering rules.
2787
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2788.SS The high-level write interface
2789
2790At this point there are two ways to proceed; through the high-level
2791write interface, or through a sequence of low-level write operations.
2792You can use the high-level interface if your image data is present
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2793in the info structure. All defined output
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]2794transformations are permitted, enabled by the following masks.
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2795
2796 PNG_TRANSFORM_IDENTITY No transformation
2797 PNG_TRANSFORM_PACKING Pack 1, 2 and 4-bit samples
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2798 PNG_TRANSFORM_PACKSWAP Change order of packed
2799 pixels to LSB first
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2800 PNG_TRANSFORM_INVERT_MONO Invert monochrome images
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2801 PNG_TRANSFORM_SHIFT Normalize pixels to the
2802 sBIT depth
2803 PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA
2804 to BGRA
2805 PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA
2806 to AG
2807 PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity
2808 to transparency
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2809 PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples
2810 PNG_TRANSFORM_STRIP_FILLER Strip out filler bytes.
2811
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2812If you have valid image data in the info structure (you can use
2813png_set_rows() to put image data in the info structure), simply do this:
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2814
2815 png_write_png(png_ptr, info_ptr, png_transforms, NULL)
2816
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]2817where png_transforms is an integer containing the bitwise OR of some set of
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2818transformation flags. This call is equivalent to png_write_info(),
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2819followed the set of transformations indicated by the transform mask,
2820then png_write_image(), and finally png_write_end().
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2821
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2822(The final parameter of this call is not yet used. Someday it might point
2823to transformation parameters required by some future output transform.)
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2824
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]2825You must use png_transforms and not call any png_set_transform() functions
2826when you use png_write_png().
2827
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2828.SS The low-level write interface
2829
2830If you are going the low-level route instead, you are now ready to
2831write all the file information up to the actual image data. You do
2832this with a call to png_write_info().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2833
2834 png_write_info(png_ptr, info_ptr);
2835
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2836Note that there is one transformation you may need to do before
2837png_write_info(). In PNG files, the alpha channel in an image is the
2838level of opacity. If your data is supplied as a level of
2839transparency, you can invert the alpha channel before you write it, so
2840that 0 is fully transparent and 255 (in 8-bit or paletted images) or
284165535 (in 16-bit images) is fully opaque, with
2842
2843 png_set_invert_alpha(png_ptr);
2844
2845This must appear before png_write_info() instead of later with the
2846other transformations because in the case of paletted images the tRNS
2847chunk data has to be inverted before the tRNS chunk is written. If
2848your image is not a paletted image, the tRNS data (which in such cases
2849represents a single color to be rendered as transparent) won't need to
2850be changed, and you can safely do this transformation after your
2851png_write_info() call.
2852
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]2853If you need to write a private chunk that you want to appear before
2854the PLTE chunk when PLTE is present, you can write the PNG info in
2855two steps, and insert code to write your own chunk between them:
2856
2857 png_write_info_before_PLTE(png_ptr, info_ptr);
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2858 png_set_unknown_chunks(png_ptr, info_ptr, ...);
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]2859 png_write_info(png_ptr, info_ptr);
2860
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2861After you've written the file information, you can set up the library
2862to handle any special transformations of the image data. The various
2863ways to transform the data will be described in the order that they
2864should occur. This is important, as some of these change the color
2865type and/or bit depth of the data, and some others only work on
2866certain color types and bit depths. Even though each transformation
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2867checks 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]2868make sure to only enable a transformation if it will be valid for the
2869data. For example, don't swap red and blue on grayscale data.
2870
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]2871PNG files store RGB pixels packed into 3 or 6 bytes. This code tells
Glenn Randers-Pehrson68ea2432000-04-01 21:10:05 -0600[diff] [blame]2872the 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]2873to 3 or 6 bytes (or strip 2 or 4-byte grayscale+filler data to 1 or 2
2874bytes per pixel).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2875
2876 png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
2877
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2878where the 0 is unused, and the location is either PNG_FILLER_BEFORE or
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2879PNG_FILLER_AFTER, depending upon whether the filler byte in the pixel
2880is stored XRGB or RGBX.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2881
2882PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
2883they can, resulting in, for example, 8 pixels per byte for 1 bit files.
2884If the data is supplied at 1 pixel per byte, use this code, which will
2885correctly pack the pixels into a single byte:
2886
2887 png_set_packing(png_ptr);
2888
2889PNG files reduce possible bit depths to 1, 2, 4, 8, and 16. If your
2890data is of another bit depth, you can write an sBIT chunk into the
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2891file so that decoders can recover the original data if desired.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2892
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2893 /* Set the true bit depth of the image data */
2894 if (color_type & PNG_COLOR_MASK_COLOR)
2895 {
2896 sig_bit.red = true_bit_depth;
2897 sig_bit.green = true_bit_depth;
2898 sig_bit.blue = true_bit_depth;
2899 }
2900 else
2901 {
2902 sig_bit.gray = true_bit_depth;
2903 }
2904 if (color_type & PNG_COLOR_MASK_ALPHA)
2905 {
2906 sig_bit.alpha = true_bit_depth;
2907 }
2908
2909 png_set_sBIT(png_ptr, info_ptr, &sig_bit);
2910
2911If 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]2912one 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]2913this will scale the values to appear to be the correct bit depth as
2914is required by PNG.
2915
2916 png_set_shift(png_ptr, &sig_bit);
2917
2918PNG files store 16 bit pixels in network byte order (big-endian,
2919ie. most significant bits first). This code would be used if they are
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2920supplied the other way (little-endian, i.e. least significant bits
2921first, the way PCs store them):
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2922
2923 if (bit_depth > 8)
2924 png_set_swap(png_ptr);
2925
2926If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you
2927need to change the order the pixels are packed into bytes, you can use:
2928
2929 if (bit_depth < 8)
2930 png_set_packswap(png_ptr);
2931
2932PNG files store 3 color pixels in red, green, blue order. This code
2933would be used if they are supplied as blue, green, red:
2934
2935 png_set_bgr(png_ptr);
2936
2937PNG files describe monochrome as black being zero and white being
2938one. This code would be used if the pixels are supplied with this reversed
2939(black being one and white being zero):
2940
2941 png_set_invert_mono(png_ptr);
2942
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2943Finally, you can write your own transformation function if none of
2944the existing ones meets your needs. This is done by setting a callback
2945with
2946
2947 png_set_write_user_transform_fn(png_ptr,
2948 write_transform_fn);
2949
2950You must supply the function
2951
2952 void write_transform_fn(png_ptr ptr, row_info_ptr
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2953 row_info, png_bytep data)
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2954
2955See pngtest.c for a working example. Your function will be called
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]2956before any of the other transformations are processed.
2957
2958You can also set up a pointer to a user structure for use by your
2959callback function.
2960
2961 png_set_user_transform_info(png_ptr, user_ptr, 0, 0);
2962
2963The user_channels and user_depth parameters of this function are ignored
2964when writing; you can set them to zero as shown.
2965
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2966You can retrieve the pointer via the function png_get_user_transform_ptr().
2967For example:
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]2968
2969 voidp write_user_transform_ptr =
2970 png_get_user_transform_ptr(png_ptr);
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2971
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2972It is possible to have libpng flush any pending output, either manually,
2973or automatically after a certain number of lines have been written. To
2974flush the output stream a single time call:
2975
2976 png_write_flush(png_ptr);
2977
2978and to have libpng flush the output stream periodically after a certain
2979number of scanlines have been written, call:
2980
2981 png_set_flush(png_ptr, nrows);
2982
2983Note that the distance between rows is from the last time png_write_flush()
2984was called, or the first row of the image if it has never been called.
2985So if you write 50 lines, and then png_set_flush 25, it will flush the
2986output on the next scanline, and every 25 lines thereafter, unless
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2987png_write_flush() is called before 25 more lines have been written.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2988If 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]2989RGB image) the image compression may decrease noticeably (although this
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2990may be acceptable for real-time applications). Infrequent flushing will
2991only degrade the compression performance by a few percent over images
2992that do not use flushing.
2993
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2994.SS Writing the image data
2995
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2996That's it for the transformations. Now you can write the image data.
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2997The 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]2998whole image in memory, you can just call png_write_image() and libpng
2999will write the image. You will need to pass in an array of pointers to
3000each row. This function automatically handles interlacing, so you don't
3001need to call png_set_interlace_handling() or call this function multiple
3002times, or any of that other stuff necessary with png_write_rows().
3003
3004 png_write_image(png_ptr, row_pointers);
3005
3006where row_pointers is:
3007
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]3008 png_byte *row_pointers[height];
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3009
3010You can point to void or char or whatever you use for pixels.
3011
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]3012If you don't want to write the whole image at once, you can
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3013use png_write_rows() instead. If the file is not interlaced,
3014this is simple:
3015
3016 png_write_rows(png_ptr, row_pointers,
3017 number_of_rows);
3018
3019row_pointers is the same as in the png_write_image() call.
3020
3021If 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]3022a single row_pointer instead of an array of row_pointers:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3023
3024 png_bytep row_pointer = row;
3025
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3026 png_write_row(png_ptr, row_pointer);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3027
3028When the file is interlaced, things can get a good deal more
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3029complicated. The only currently (as of the PNG Specification
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3030version 1.2, dated July 1999) defined interlacing scheme for PNG files
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3031is the "Adam7" interlace scheme, that breaks down an
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3032image into seven smaller images of varying size. libpng will build
3033these images for you, or you can do them yourself. If you want to
3034build them yourself, see the PNG specification for details of which
3035pixels to write when.
3036
3037If you don't want libpng to handle the interlacing details, just
3038use png_set_interlace_handling() and call png_write_rows() the
3039correct number of times to write all seven sub-images.
3040
3041If you want libpng to build the sub-images, call this before you start
3042writing any rows:
3043
3044 number_of_passes =
3045 png_set_interlace_handling(png_ptr);
3046
3047This will return the number of passes needed. Currently, this
3048is seven, but may change if another interlace type is added.
3049
3050Then write the complete image number_of_passes times.
3051
3052 png_write_rows(png_ptr, row_pointers,
3053 number_of_rows);
3054
3055As some of these rows are not used, and thus return immediately,
3056you may want to read about interlacing in the PNG specification,
3057and only update the rows that are actually used.
3058
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3059.SS Finishing a sequential write
3060
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3061After you are finished writing the image, you should finish writing
3062the file. If you are interested in writing comments or time, you should
3063pass an appropriately filled png_info pointer. If you are not interested,
3064you can pass NULL.
3065
3066 png_write_end(png_ptr, info_ptr);
3067
3068When you are done, you can free all memory used by libpng like this:
3069
3070 png_destroy_write_struct(&png_ptr, &info_ptr);
3071
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3072It is also possible to individually free the info_ptr members that
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]3073point to libpng-allocated storage with the following function:
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3074
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3075 png_free_data(png_ptr, info_ptr, mask, seq)
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3076 mask - identifies data to be freed, a mask
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]3077 containing the bitwise OR of one or
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3078 more of
3079 PNG_FREE_PLTE, PNG_FREE_TRNS,
3080 PNG_FREE_HIST, PNG_FREE_ICCP,
3081 PNG_FREE_PCAL, PNG_FREE_ROWS,
3082 PNG_FREE_SCAL, PNG_FREE_SPLT,
3083 PNG_FREE_TEXT, PNG_FREE_UNKN,
3084 or simply PNG_FREE_ALL
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3085 seq - sequence number of item to be freed
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3086 (-1 for all items)
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3087
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]3088This function may be safely called when the relevant storage has
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3089already been freed, or has not yet been allocated, or was allocated
3090by the user and not by libpng, and will in those
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3091cases do nothing. The "seq" parameter is ignored if only one item
3092of the selected data type, such as PLTE, is allowed. If "seq" is not
Glenn Randers-Pehrson68ea2432000-04-01 21:10:05 -0600[diff] [blame]3093-1, and multiple items are allowed for the data type identified in
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3094the mask, such as text or sPLT, only the n'th item in the structure
3095is freed, where n is "seq".
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3096
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3097If you allocated data such as a palette that you passed
3098in to libpng with png_set_*, you must not free it until just before the call to
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]3099png_destroy_write_struct().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3100
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3101The default behavior is only to free data that was allocated internally
3102by libpng. This can be changed, so that libpng will not free the data,
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3103or so that it will free data that was allocated by the user with png_malloc()
3104or png_zalloc() and passed in via a png_set_*() function, with
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3105
3106 png_data_freer(png_ptr, info_ptr, freer, mask)
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3107 mask - which data elements are affected
3108 same choices as in png_free_data()
3109 freer - one of
3110 PNG_DESTROY_WILL_FREE_DATA
3111 PNG_SET_WILL_FREE_DATA
3112 PNG_USER_WILL_FREE_DATA
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3113
3114For example, to transfer responsibility for some data from a read structure
3115to a write structure, you could use
3116
3117 png_data_freer(read_ptr, read_info_ptr,
3118 PNG_USER_WILL_FREE_DATA,
3119 PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST)
3120 png_data_freer(write_ptr, write_info_ptr,
3121 PNG_DESTROY_WILL_FREE_DATA,
3122 PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST)
3123
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3124thereby briefly reassigning responsibility for freeing to the user but
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3125immediately afterwards reassigning it once more to the write_destroy
3126function. Having done this, it would then be safe to destroy the read
3127structure and continue to use the PLTE, tRNS, and hIST data in the write
3128structure.
3129
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3130This function only affects data that has already been allocated.
3131You can call this function before calling after the png_set_*() functions
3132to control whether the user or png_destroy_*() is supposed to free the data.
3133When the user assumes responsibility for libpng-allocated data, the
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3134application must use
3135png_free() to free it, and when the user transfers responsibility to libpng
3136for data that the user has allocated, the user must have used png_malloc()
3137or png_zalloc() to allocate it.
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3138
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3139If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword
3140separately, do not transfer responsibility for freeing text_ptr to libpng,
3141because when libpng fills a png_text structure it combines these members with
3142the key member, and png_free_data() will free only text_ptr.key. Similarly,
3143if you transfer responsibility for free'ing text_ptr from libpng to your
3144application, your application must not separately free those members.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3145For a more compact example of writing a PNG image, see the file example.c.
3146
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3147.SH V. Modifying/Customizing libpng:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3148
Glenn Randers-Pehrson231e6872001-01-12 15:13:06 -0600[diff] [blame]3149There are three issues here. The first is changing how libpng does
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3150standard things like memory allocation, input/output, and error handling.
3151The second deals with more complicated things like adding new chunks,
3152adding new transformations, and generally changing how libpng works.
Glenn Randers-Pehrson231e6872001-01-12 15:13:06 -0600[diff] [blame]3153Both of those are compile-time issues; that is, they are generally
3154determined at the time the code is written, and there is rarely a need
3155to provide the user with a means of changing them. The third is a
3156run-time issue: choosing between and/or tuning one or more alternate
3157versions of computationally intensive routines; specifically, optimized
3158assembly-language (and therefore compiler- and platform-dependent)
3159versions.
3160
3161Memory allocation, input/output, and error handling
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3162
3163All of the memory allocation, input/output, and error handling in libpng
Glenn Randers-Pehrson231e6872001-01-12 15:13:06 -0600[diff] [blame]3164goes through callbacks that are user-settable. The default routines are
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3165in pngmem.c, pngrio.c, pngwio.c, and pngerror.c, respectively. To change
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]3166these functions, call the appropriate png_set_*_fn() function.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3167
Glenn Randers-Pehrsoncfbed9b2002-05-21 18:06:08 -0500[diff] [blame]3168Memory allocation is done through the functions png_malloc()
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3169and png_free(). These currently just call the standard C functions. If
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3170your pointers can't access more then 64K at a time, you will want to set
3171MAXSEG_64K in zlib.h. Since it is unlikely that the method of handling
3172memory allocation on a platform will change between applications, these
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3173functions must be modified in the library at compile time. If you prefer
3174to use a different method of allocating and freeing data, you can use
Glenn Randers-Pehrsoncfbed9b2002-05-21 18:06:08 -0500[diff] [blame]3175png_create_read_struct_2() or png_create_write_struct_2() to register
3176your own functions as described above.
Glenn Randers-Pehrsoncfbed9b2002-05-21 18:06:08 -0500[diff] [blame]3177These functions also provide a void pointer that can be retrieved via
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3178
3179 mem_ptr=png_get_mem_ptr(png_ptr);
3180
3181Your replacement memory functions must have prototypes as follows:
3182
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3183 png_voidp malloc_fn(png_structp png_ptr,
Glenn Randers-Pehrsonae498dc2001-11-24 14:53:31 -0600[diff] [blame]3184 png_size_t size);
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3185 void free_fn(png_structp png_ptr, png_voidp ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3186
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]3187Your malloc_fn() must return NULL in case of failure. The png_malloc()
3188function will normally call png_error() if it receives a NULL from the
3189system memory allocator or from your replacement malloc_fn().
Glenn Randers-Pehrson82ae3832001-04-20 10:32:10 -0500[diff] [blame]3190
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3191Input/Output in libpng is done through png_read() and png_write(),
3192which currently just call fread() and fwrite(). The FILE * is stored in
3193png_struct and is initialized via png_init_io(). If you wish to change
3194the method of I/O, the library supplies callbacks that you can set
3195through the function png_set_read_fn() and png_set_write_fn() at run
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3196time, instead of calling the png_init_io() function. These functions
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3197also provide a void pointer that can be retrieved via the function
3198png_get_io_ptr(). For example:
3199
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]3200 png_set_read_fn(png_structp read_ptr,
3201 voidp read_io_ptr, png_rw_ptr read_data_fn)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3202
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]3203 png_set_write_fn(png_structp write_ptr,
3204 voidp write_io_ptr, png_rw_ptr write_data_fn,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3205 png_flush_ptr output_flush_fn);
3206
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]3207 voidp read_io_ptr = png_get_io_ptr(read_ptr);
3208 voidp write_io_ptr = png_get_io_ptr(write_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3209
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3210The replacement I/O functions must have prototypes as follows:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3211
3212 void user_read_data(png_structp png_ptr,
Glenn Randers-Pehrson837a3d12002-05-10 20:19:58 -0500[diff] [blame]3213 png_bytep data, png_size_t length);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3214 void user_write_data(png_structp png_ptr,
Glenn Randers-Pehrson837a3d12002-05-10 20:19:58 -0500[diff] [blame]3215 png_bytep data, png_size_t length);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3216 void user_flush_data(png_structp png_ptr);
3217
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]3218The user_read_data() function is responsible for detecting and
3219handling end-of-data errors.
3220
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3221Supplying NULL for the read, write, or flush functions sets them back
3222to using the default C stream functions. It is an error to read from
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3223a write stream, and vice versa.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3224
3225Error handling in libpng is done through png_error() and png_warning().
3226Errors handled through png_error() are fatal, meaning that png_error()
3227should never return to its caller. Currently, this is handled via
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3228setjmp() and longjmp() (unless you have compiled libpng with
3229PNG_SETJMP_NOT_SUPPORTED, in which case it is handled via PNG_ABORT()),
3230but you could change this to do things like exit() if you should wish.
3231
3232On non-fatal errors, png_warning() is called
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3233to print a warning message, and then control returns to the calling code.
3234By default png_error() and png_warning() print a message on stderr via
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3235fprintf() unless the library is compiled with PNG_NO_CONSOLE_IO defined
3236(because you don't want the messages) or PNG_NO_STDIO defined (because
3237fprintf() isn't available). If you wish to change the behavior of the error
3238functions, you will need to set up your own message callbacks. These
3239functions are normally supplied at the time that the png_struct is created.
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3240It is also possible to redirect errors and warnings to your own replacement
3241functions after png_create_*_struct() has been called by calling:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3242
3243 png_set_error_fn(png_structp png_ptr,
3244 png_voidp error_ptr, png_error_ptr error_fn,
3245 png_error_ptr warning_fn);
3246
3247 png_voidp error_ptr = png_get_error_ptr(png_ptr);
3248
3249If NULL is supplied for either error_fn or warning_fn, then the libpng
3250default function will be used, calling fprintf() and/or longjmp() if a
3251problem is encountered. The replacement error functions should have
3252parameters as follows:
3253
3254 void user_error_fn(png_structp png_ptr,
3255 png_const_charp error_msg);
3256 void user_warning_fn(png_structp png_ptr,
3257 png_const_charp warning_msg);
3258
3259The motivation behind using setjmp() and longjmp() is the C++ throw and
3260catch exception handling methods. This makes the code much easier to write,
3261as there is no need to check every return code of every function call.
3262However, there are some uncertainties about the status of local variables
3263after a longjmp, so the user may want to be careful about doing anything after
3264setjmp returns non-zero besides returning itself. Consult your compiler
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3265documentation for more details. For an alternative approach, you may wish
3266to use the "cexcept" facility (see http://cexcept.sourceforge.net).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3267
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3268.SS Custom chunks
3269
3270If you need to read or write custom chunks, you may need to get deeper
3271into the libpng code. The library now has mechanisms for storing
3272and writing chunks of unknown type; you can even declare callbacks
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]3273for custom chunks. However, this may not be good enough if the
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3274library code itself needs to know about interactions between your
3275chunk and existing `intrinsic' chunks.
3276
3277If you need to write a new intrinsic chunk, first read the PNG
3278specification. Acquire a first level of
3279understanding of how it works. Pay particular attention to the
3280sections that describe chunk names, and look at how other chunks were
3281designed, so you can do things similarly. Second, check out the
3282sections of libpng that read and write chunks. Try to find a chunk
3283that is similar to yours and use it as a template. More details can
3284be found in the comments inside the code. It is best to handle unknown
3285chunks in a generic method, via callback functions, instead of by
3286modifying libpng functions.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3287
3288If you wish to write your own transformation for the data, look through
3289the part of the code that does the transformations, and check out some of
3290the simpler ones to get an idea of how they work. Try to find a similar
3291transformation to the one you want to add and copy off of it. More details
3292can be found in the comments inside the code itself.
3293
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3294.SS Configuring for 16 bit platforms
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3295
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3296You 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]3297it 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]3298won'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]3299
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3300.SS Configuring for DOS
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3301
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3302For DOS users who only have access to the lower 640K, you will
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3303have to limit zlib's memory usage via a png_set_compression_mem_level()
3304call. See zlib.h or zconf.h in the zlib library for more information.
3305
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3306.SS Configuring for Medium Model
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3307
3308Libpng's support for medium model has been tested on most of the popular
3309compilers. Make sure MAXSEG_64K gets defined, USE_FAR_KEYWORD gets
3310defined, and FAR gets defined to far in pngconf.h, and you should be
3311all set. Everything in the library (except for zlib's structure) is
3312expecting far data. You must use the typedefs with the p or pp on
3313the end for pointers (or at least look at them and be careful). Make
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3314note that the rows of data are defined as png_bytepp, which is an
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3315unsigned char far * far *.
3316
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3317.SS Configuring for gui/windowing platforms:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3318
3319You will need to write new error and warning functions that use the GUI
3320interface, as described previously, and set them to be the error and
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]3321warning functions at the time that png_create_*_struct() is called,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3322in order to have them available during the structure initialization.
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3323They can be changed later via png_set_error_fn(). On some compilers,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3324you may also have to change the memory allocators (png_malloc, etc.).
3325
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3326.SS Configuring for compiler xxx:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3327
Glenn Randers-Pehrsonbeb572e2006-08-19 13:59:24 -0500[diff] [blame]3328All includes for libpng are in pngconf.h. If you need to add, change
3329or delete an include, this is the place to do it. The includes that
3330are not needed outside libpng are placed inside pngpriv.h, which is
3331only used by the routines inside libpng itself.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3332
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3333.SS Configuring zlib:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3334
3335There are special functions to configure the compression. Perhaps the
3336most useful one changes the compression level, which currently uses
3337input compression values in the range 0 - 9. The library normally
3338uses the default compression level (Z_DEFAULT_COMPRESSION = 6). Tests
3339have shown that for a large majority of images, compression values in
3340the range 3-6 compress nearly as well as higher levels, and do so much
3341faster. For online applications it may be desirable to have maximum speed
3342(Z_BEST_SPEED = 1). With versions of zlib after v0.99, you can also
3343specify no compression (Z_NO_COMPRESSION = 0), but this would create
3344files larger than just storing the raw bitmap. You can specify the
3345compression level by calling:
3346
3347 png_set_compression_level(png_ptr, level);
3348
3349Another useful one is to reduce the memory level used by the library.
3350The memory level defaults to 8, but it can be lowered if you are
3351short on memory (running DOS, for example, where you only have 640K).
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]3352Note that the memory level does have an effect on compression; among
3353other things, lower levels will result in sections of incompressible
3354data being emitted in smaller stored blocks, with a correspondingly
3355larger relative overhead of up to 15% in the worst case.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3356
3357 png_set_compression_mem_level(png_ptr, level);
3358
3359The other functions are for configuring zlib. They are not recommended
3360for normal use and may result in writing an invalid PNG file. See
3361zlib.h for more information on what these mean.
3362
3363 png_set_compression_strategy(png_ptr,
3364 strategy);
3365 png_set_compression_window_bits(png_ptr,
3366 window_bits);
3367 png_set_compression_method(png_ptr, method);
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3368 png_set_compression_buffer_size(png_ptr, size);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3369
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3370.SS Controlling row filtering
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3371
3372If you want to control whether libpng uses filtering or not, which
3373filters are used, and how it goes about picking row filters, you
3374can call one of these functions. The selection and configuration
3375of row filters can have a significant impact on the size and
3376encoding speed and a somewhat lesser impact on the decoding speed
3377of an image. Filtering is enabled by default for RGB and grayscale
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3378images (with and without alpha), but not for paletted images nor
3379for any images with bit depths less than 8 bits/pixel.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3380
3381The 'method' parameter sets the main filtering method, which is
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3382currently only '0' in the PNG 1.2 specification. The 'filters'
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3383parameter sets which filter(s), if any, should be used for each
3384scanline. Possible values are PNG_ALL_FILTERS and PNG_NO_FILTERS
3385to turn filtering on and off, respectively.
3386
3387Individual filter types are PNG_FILTER_NONE, PNG_FILTER_SUB,
3388PNG_FILTER_UP, PNG_FILTER_AVG, PNG_FILTER_PAETH, which can be bitwise
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3389ORed together with '|' to specify one or more filters to use.
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]3390These filters are described in more detail in the PNG specification.
3391If you intend to change the filter type during the course of writing
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3392the image, you should start with flags set for all of the filters
3393you intend to use so that libpng can initialize its internal
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]3394structures appropriately for all of the filter types. (Note that this
3395means the first row must always be adaptively filtered, because libpng
3396currently does not allocate the filter buffers until png_write_row()
3397is called for the first time.)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3398
3399 filters = PNG_FILTER_NONE | PNG_FILTER_SUB
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3400 PNG_FILTER_UP | PNG_FILTER_AVE |
3401 PNG_FILTER_PAETH | PNG_ALL_FILTERS;
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3402
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3403 png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE,
3404 filters);
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3405 The second parameter can also be
3406 PNG_INTRAPIXEL_DIFFERENCING if you are
3407 writing a PNG to be embedded in a MNG
3408 datastream. This parameter must be the
3409 same as the value of filter_method used
3410 in png_set_IHDR().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3411
3412It is also possible to influence how libpng chooses from among the
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]3413available filters. This is done in one or both of two ways - by
3414telling it how important it is to keep the same filter for successive
3415rows, and by telling it the relative computational costs of the filters.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3416
3417 double weights[3] = {1.5, 1.3, 1.1},
3418 costs[PNG_FILTER_VALUE_LAST] =
3419 {1.0, 1.3, 1.3, 1.5, 1.7};
3420
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]3421 png_set_filter_heuristics(png_ptr,
3422 PNG_FILTER_HEURISTIC_WEIGHTED, 3,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3423 weights, costs);
3424
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3425The weights are multiplying factors that indicate to libpng that the
3426row filter should be the same for successive rows unless another row filter
3427is that many times better than the previous filter. In the above example,
3428if 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]3429"sum of absolute differences" 1.5 x 1.3 times higher than other filters
3430and still be chosen, while the NONE filter could have a sum 1.1 times
3431higher than other filters and still be chosen. Unspecified weights are
3432taken to be 1.0, and the specified weights should probably be declining
3433like those above in order to emphasize recent filters over older filters.
3434
3435The filter costs specify for each filter type a relative decoding cost
3436to be considered when selecting row filters. This means that filters
3437with higher costs are less likely to be chosen over filters with lower
3438costs, unless their "sum of absolute differences" is that much smaller.
3439The costs do not necessarily reflect the exact computational speeds of
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3440the various filters, since this would unduly influence the final image
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3441size.
3442
3443Note that the numbers above were invented purely for this example and
3444are given only to help explain the function usage. Little testing has
3445been done to find optimum values for either the costs or the weights.
3446
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3447.SS Removing unwanted object code
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3448
3449There are a bunch of #define's in pngconf.h that control what parts of
3450libpng are compiled. All the defines end in _SUPPORTED. If you are
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]3451never going to use a capability, you can change the #define to #undef
3452before recompiling libpng and save yourself code and data space, or
3453you can turn off individual capabilities with defines that begin with
3454PNG_NO_.
3455
3456You can also turn all of the transforms and ancillary chunk capabilities
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3457off en masse with compiler directives that define
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]3458PNG_NO_READ[or WRITE]_TRANSFORMS, or PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS,
3459or all four,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3460along with directives to turn on any of the capabilities that you do
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]3461want. The PNG_NO_READ[or WRITE]_TRANSFORMS directives disable
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3462the extra transformations but still leave the library fully capable of reading
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3463and writing PNG files with all known public chunks
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]3464Use of the PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS directive
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3465produces a library that is incapable of reading or writing ancillary chunks.
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3466If you are not using the progressive reading capability, you can
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]3467turn that off with PNG_NO_PROGRESSIVE_READ (don't confuse
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3468this with the INTERLACING capability, which you'll still have).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3469
3470All the reading and writing specific code are in separate files, so the
3471linker should only grab the files it needs. However, if you want to
3472make sure, or if you are building a stand alone library, all the
3473reading files start with pngr and all the writing files start with
3474pngw. The files that don't match either (like png.c, pngtrans.c, etc.)
3475are used for both reading and writing, and always need to be included.
3476The progressive reader is in pngpread.c
3477
3478If you are creating or distributing a dynamically linked library (a .so
3479or DLL file), you should not remove or disable any parts of the library,
3480as this will cause applications linked with different versions of the
3481library to fail if they call functions not available in your library.
3482The size of the library itself should not be an issue, because only
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3483those sections that are actually used will be loaded into memory.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3484
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3485.SS Requesting debug printout
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3486
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3487The macro definition PNG_DEBUG can be used to request debugging
3488printout. Set it to an integer value in the range 0 to 3. Higher
3489numbers result in increasing amounts of debugging information. The
3490information is printed to the "stderr" file, unless another file
3491name is specified in the PNG_DEBUG_FILE macro definition.
3492
3493When PNG_DEBUG > 0, the following functions (macros) become available:
3494
3495 png_debug(level, message)
3496 png_debug1(level, message, p1)
3497 png_debug2(level, message, p1, p2)
3498
3499in which "level" is compared to PNG_DEBUG to decide whether to print
3500the message, "message" is the formatted string to be printed,
3501and p1 and p2 are parameters that are to be embedded in the string
3502according to printf-style formatting directives. For example,
3503
3504 png_debug1(2, "foo=%d\n", foo);
3505
3506is expanded to
3507
3508 if(PNG_DEBUG > 2)
3509 fprintf(PNG_DEBUG_FILE, "foo=%d\n", foo);
3510
3511When PNG_DEBUG is defined but is zero, the macros aren't defined, but you
3512can still use PNG_DEBUG to control your own debugging:
3513
3514 #ifdef PNG_DEBUG
3515 fprintf(stderr, ...
3516 #endif
3517
3518When PNG_DEBUG = 1, the macros are defined, but only png_debug statements
3519having level = 0 will be printed. There aren't any such statements in
3520this version of libpng, but if you insert some they will be printed.
3521
Glenn Randers-Pehrson67864af2004-08-28 23:30:07 -0500[diff] [blame]3522.SH VI. Runtime optimization
3523
3524A new feature in libpng 1.2.0 is the ability to dynamically switch between
3525standard and optimized versions of some routines. Currently these are
3526limited to three computationally intensive tasks when reading PNG files:
3527decoding row filters, expanding interlacing, and combining interlaced or
3528transparent row data with previous row data. Currently the optimized
3529versions are available only for x86 (Intel, AMD, etc.) platforms with
3530MMX support, though this may change in future versions. (For example,
3531the non-MMX assembler optimizations for zlib might become similarly
3532runtime-selectable in future releases, in which case libpng could be
3533extended to support them. Alternatively, the compile-time choice of
3534floating-point versus integer routines for gamma correction might become
3535runtime-selectable.)
3536
3537Because such optimizations tend to be very platform- and compiler-dependent,
3538both in how they are written and in how they perform, the new runtime code
3539in libpng has been written to allow programs to query, enable, and disable
3540either specific optimizations or all such optimizations. For example, to
3541enable all possible optimizations (bearing in mind that some "optimizations"
3542may actually run more slowly in rare cases):
3543
3544 #if defined(PNG_LIBPNG_VER) && (PNG_LIBPNG_VER >= 10200)
3545 png_uint_32 mask, flags;
3546
3547 flags = png_get_asm_flags(png_ptr);
3548 mask = png_get_asm_flagmask(PNG_SELECT_READ | PNG_SELECT_WRITE);
3549 png_set_asm_flags(png_ptr, flags | mask);
3550 #endif
3551
3552To enable only optimizations relevant to reading PNGs, use PNG_SELECT_READ
3553by itself when calling png_get_asm_flagmask(); similarly for optimizing
3554only writing. To disable all optimizations:
3555
3556 #if defined(PNG_LIBPNG_VER) && (PNG_LIBPNG_VER >= 10200)
3557 flags = png_get_asm_flags(png_ptr);
3558 mask = png_get_asm_flagmask(PNG_SELECT_READ | PNG_SELECT_WRITE);
3559 png_set_asm_flags(png_ptr, flags & ~mask);
3560 #endif
3561
3562To enable or disable only MMX-related features, use png_get_mmx_flagmask()
3563in place of png_get_asm_flagmask(). The mmx version takes one additional
3564parameter:
3565
3566 #if defined(PNG_LIBPNG_VER) && (PNG_LIBPNG_VER >= 10200)
3567 int selection = PNG_SELECT_READ | PNG_SELECT_WRITE;
3568 int compilerID;
3569
3570 mask = png_get_mmx_flagmask(selection, &compilerID);
3571 #endif
3572
3573On return, compilerID will indicate which version of the MMX assembler
3574optimizations was compiled. Currently two flavors exist: Microsoft
3575Visual C++ (compilerID == 1) and GNU C (a.k.a. gcc/gas, compilerID == 2).
3576On non-x86 platforms or on systems compiled without MMX optimizations, a
3577value of -1 is used.
3578
3579Note that both png_get_asm_flagmask() and png_get_mmx_flagmask() return
3580all valid, settable optimization bits for the version of the library that's
3581currently in use. In the case of shared (dynamically linked) libraries,
3582this may include optimizations that did not exist at the time the code was
3583written and compiled. It is also possible, of course, to enable only known,
3584specific optimizations; for example:
3585
3586 #if defined(PNG_LIBPNG_VER) && (PNG_LIBPNG_VER >= 10200)
3587 flags = PNG_ASM_FLAG_MMX_READ_COMBINE_ROW \
3588 | PNG_ASM_FLAG_MMX_READ_INTERLACE \
3589 | PNG_ASM_FLAG_MMX_READ_FILTER_SUB \
3590 | PNG_ASM_FLAG_MMX_READ_FILTER_UP \
3591 | PNG_ASM_FLAG_MMX_READ_FILTER_AVG \
3592 | PNG_ASM_FLAG_MMX_READ_FILTER_PAETH ;
3593 png_set_asm_flags(png_ptr, flags);
3594 #endif
3595
3596This method would enable only the MMX read-optimizations available at the
3597time of libpng 1.2.0's release, regardless of whether a later version of
3598the DLL were actually being used. (Also note that these functions did not
3599exist in versions older than 1.2.0, so any attempt to run a dynamically
3600linked app on such an older version would fail.)
3601
3602To determine whether the processor supports MMX instructions at all, use
3603the png_mmx_support() function:
3604
3605 #if defined(PNG_LIBPNG_VER) && (PNG_LIBPNG_VER >= 10200)
3606 mmxsupport = png_mmx_support();
3607 #endif
3608
3609It returns -1 if MMX support is not compiled into libpng, 0 if MMX code
3610is compiled but MMX is not supported by the processor, or 1 if MMX support
3611is fully available. Note that png_mmx_support(), png_get_mmx_flagmask(),
3612and png_get_asm_flagmask() all may be called without allocating and ini-
3613tializing any PNG structures (for example, as part of a usage screen or
3614"about" box).
3615
3616The following code can be used to prevent an application from using the
3617thread_unsafe features, even if libpng was built with PNG_THREAD_UNSAFE_OK
3618defined:
3619
Glenn Randers-Pehrson17218292006-04-20 07:20:46 -0500[diff] [blame]3620#if defined(PNG_USE_PNGGCCRD) && defined(PNG_MMX_CODE_SUPPORTED) \
Glenn Randers-Pehrson67864af2004-08-28 23:30:07 -0500[diff] [blame]3621 && defined(PNG_THREAD_UNSAFE_OK)
3622 /* Disable thread-unsafe features of pnggccrd */
Glenn Randers-Pehrson86dc9812006-05-10 07:27:44 -0500[diff] [blame]3623 if (png_access_version_number() >= 10200)
Glenn Randers-Pehrson67864af2004-08-28 23:30:07 -0500[diff] [blame]3624 {
3625 png_uint_32 mmx_disable_mask = 0;
3626 png_uint_32 asm_flags;
3627
3628 mmx_disable_mask |= ( PNG_ASM_FLAG_MMX_READ_COMBINE_ROW \
3629 | PNG_ASM_FLAG_MMX_READ_FILTER_SUB \
3630 | PNG_ASM_FLAG_MMX_READ_FILTER_AVG \
3631 | PNG_ASM_FLAG_MMX_READ_FILTER_PAETH );
3632 asm_flags = png_get_asm_flags(png_ptr);
3633 png_set_asm_flags(png_ptr, asm_flags & ~mmx_disable_mask);
3634 }
3635#endif
3636
3637For more extensive examples of runtime querying, enabling and disabling
3638of optimized features, see contrib/gregbook/readpng2.c in the libpng
3639source-code distribution.
3640
3641.SH VII. MNG support
Glenn Randers-Pehrson2ad31ae2000-12-15 08:54:42 -0600[diff] [blame]3642
3643The MNG specification (available at http://www.libpng.org/pub/mng) allows
3644certain extensions to PNG for PNG images that are embedded in MNG datastreams.
3645Libpng can support some of these extensions. To enable them, use the
3646png_permit_mng_features() function:
3647
3648 feature_set = png_permit_mng_features(png_ptr, mask)
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]3649 mask is a png_uint_32 containing the bitwise OR of the
Glenn Randers-Pehrson2ad31ae2000-12-15 08:54:42 -0600[diff] [blame]3650 features you want to enable. These include
3651 PNG_FLAG_MNG_EMPTY_PLTE
3652 PNG_FLAG_MNG_FILTER_64
3653 PNG_ALL_MNG_FEATURES
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]3654 feature_set is a png_uint_32 that is the bitwise AND of
Glenn Randers-Pehrson2ad31ae2000-12-15 08:54:42 -0600[diff] [blame]3655 your mask with the set of MNG features that is
3656 supported by the version of libpng that you are using.
3657
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]3658It is an error to use this function when reading or writing a standalone
3659PNG file with the PNG 8-byte signature. The PNG datastream must be wrapped
Glenn Randers-Pehrsonf05f8032000-12-23 14:27:39 -0600[diff] [blame]3660in a MNG datastream. As a minimum, it must have the MNG 8-byte signature
3661and the MHDR and MEND chunks. Libpng does not provide support for these
3662or any other MNG chunks; your application must provide its own support for
3663them. You may wish to consider using libmng (available at
3664http://www.libmng.com) instead.
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]3665
Glenn Randers-Pehrson67864af2004-08-28 23:30:07 -0500[diff] [blame]3666.SH VIII. Changes to Libpng from version 0.88
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3667
3668It should be noted that versions of libpng later than 0.96 are not
3669distributed by the original libpng author, Guy Schalnat, nor by
3670Andreas Dilger, who had taken over from Guy during 1996 and 1997, and
3671distributed versions 0.89 through 0.96, but rather by another member
3672of the original PNG Group, Glenn Randers-Pehrson. Guy and Andreas are
3673still alive and well, but they have moved on to other things.
3674
3675The old libpng functions png_read_init(), png_write_init(),
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]3676png_info_init(), png_read_destroy(), and png_write_destroy() have been
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]3677moved to PNG_INTERNAL in version 0.95 to discourage their use. These
3678functions will be removed from libpng version 2.0.0.
3679
3680The preferred method of creating and initializing the libpng structures is
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3681via the png_create_read_struct(), png_create_write_struct(), and
3682png_create_info_struct() because they isolate the size of the structures
3683from the application, allow version error checking, and also allow the
3684use of custom error handling routines during the initialization, which
3685the old functions do not. The functions png_read_destroy() and
3686png_write_destroy() do not actually free the memory that libpng
3687allocated for these structs, but just reset the data structures, so they
3688can be used instead of png_destroy_read_struct() and
3689png_destroy_write_struct() if you feel there is too much system overhead
3690allocating and freeing the png_struct for each image read.
3691
3692Setting the error callbacks via png_set_message_fn() before
3693png_read_init() as was suggested in libpng-0.88 is no longer supported
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3694because this caused applications that do not use custom error functions
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3695to fail if the png_ptr was not initialized to zero. It is still possible
3696to set the error callbacks AFTER png_read_init(), or to change them with
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]3697png_set_error_fn(), which is essentially the same function, but with a new
3698name to force compilation errors with applications that try to use the old
3699method.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3700
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3701Starting with version 1.0.7, you can find out which version of the library
3702you are using at run-time:
3703
3704 png_uint_32 libpng_vn = png_access_version_number();
3705
3706The number libpng_vn is constructed from the major version, minor
3707version with leading zero, and release number with leading zero,
3708(e.g., libpng_vn for version 1.0.7 is 10007).
3709
3710You can also check which version of png.h you used when compiling your
3711application:
3712
3713 png_uint_32 application_vn = PNG_LIBPNG_VER;
3714
Glenn Randers-Pehrson67864af2004-08-28 23:30:07 -0500[diff] [blame]3715.SH IX. Y2K Compliance in libpng
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]3716
Glenn Randers-Pehrson895a9c92008-07-25 08:51:18 -0500[diff] [blame^]3717July 25, 2008
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]3718
3719Since the PNG Development group is an ad-hoc body, we can't make
3720an official declaration.
3721
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3722This is your unofficial assurance that libpng from version 0.71 and
Glenn Randers-Pehrson895a9c92008-07-25 08:51:18 -0500[diff] [blame^]3723upward through 1.4.0beta24 are Y2K compliant. It is my belief that earlier
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3724versions were also Y2K compliant.
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]3725
3726Libpng only has three year fields. One is a 2-byte unsigned integer that
3727will hold years up to 65535. The other two hold the date in text
3728format, and will hold years up to 9999.
3729
3730The integer is
3731 "png_uint_16 year" in png_time_struct.
3732
3733The strings are
3734 "png_charp time_buffer" in png_struct and
3735 "near_time_buffer", which is a local character string in png.c.
3736
3737There are seven time-related functions:
3738
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3739 png_convert_to_rfc_1123() in png.c
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]3740 (formerly png_convert_to_rfc_1152() in error)
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3741 png_convert_from_struct_tm() in pngwrite.c, called
3742 in pngwrite.c
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]3743 png_convert_from_time_t() in pngwrite.c
3744 png_get_tIME() in pngget.c
3745 png_handle_tIME() in pngrutil.c, called in pngread.c
3746 png_set_tIME() in pngset.c
3747 png_write_tIME() in pngwutil.c, called in pngwrite.c
3748
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3749All appear to handle dates properly in a Y2K environment. The
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]3750png_convert_from_time_t() function calls gmtime() to convert from system
3751clock time, which returns (year - 1900), which we properly convert to
3752the full 4-digit year. There is a possibility that applications using
3753libpng are not passing 4-digit years into the png_convert_to_rfc_1123()
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3754function, or that they are incorrectly passing only a 2-digit year
3755instead of "year - 1900" into the png_convert_from_struct_tm() function,
3756but this is not under our control. The libpng documentation has always
3757stated that it works with 4-digit years, and the APIs have been
3758documented as such.
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]3759
3760The tIME chunk itself is also Y2K compliant. It uses a 2-byte unsigned
3761integer to hold the year, and can hold years as large as 65535.
3762
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3763zlib, upon which libpng depends, is also Y2K compliant. It contains
3764no date-related code.
3765
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]3766
3767 Glenn Randers-Pehrson
3768 libpng maintainer
3769 PNG Development Group
3770
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3771.SH NOTE
3772
3773Note about libpng version numbers:
3774
3775Due to various miscommunications, unforeseen code incompatibilities
3776and occasional factors outside the authors' control, version numbering
3777on the library has not always been consistent and straightforward.
3778The following table summarizes matters since version 0.89c, which was
3779the first widely used release:
3780
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3781 source png.h png.h shared-lib
3782 version string int version
3783 ------- ------ ----- ----------
3784 0.89c ("beta 3") 0.89 89 1.0.89
3785 0.90 ("beta 4") 0.90 90 0.90
3786 0.95 ("beta 5") 0.95 95 0.95
3787 0.96 ("beta 6") 0.96 96 0.96
3788 0.97b ("beta 7") 1.00.97 97 1.0.1
3789 0.97c 0.97 97 2.0.97
3790 0.98 0.98 98 2.0.98
3791 0.99 0.99 98 2.0.99
3792 0.99a-m 0.99 99 2.0.99
3793 1.00 1.00 100 2.1.0
3794 1.0.0 1.0.0 100 2.1.0
3795 1.0.0 (from here on, the 100 2.1.0
3796 1.0.1 png.h string is 10001 2.1.0
3797 1.0.1a-e identical to the 10002 from here on, the
3798 1.0.2 source version) 10002 shared library is 2.V
3799 1.0.2a-b 10003 where V is the source
3800 1.0.1 10001 code version except as
3801 1.0.1a-e 10002 2.1.0.1a-e noted.
3802 1.0.2 10002 2.1.0.2
3803 1.0.2a-b 10003 2.1.0.2a-b
3804 1.0.3 10003 2.1.0.3
3805 1.0.3a-d 10004 2.1.0.3a-d
3806 1.0.4 10004 2.1.0.4
3807 1.0.4a-f 10005 2.1.0.4a-f
3808 1.0.5 (+ 2 patches) 10005 2.1.0.5
3809 1.0.5a-d 10006 2.1.0.5a-d
3810 1.0.5e-r 10100 2.1.0.5e-r
3811 1.0.5s-v 10006 2.1.0.5s-v
3812 1.0.6 (+ 3 patches) 10006 2.1.0.6
3813 1.0.6d-g 10007 2.1.0.6d-g
3814 1.0.6h 10007 10.6h
3815 1.0.6i 10007 10.6i
3816 1.0.6j 10007 2.1.0.6j
3817 1.0.7beta11-14 DLLNUM 10007 2.1.0.7beta11-14
3818 1.0.7beta15-18 1 10007 2.1.0.7beta15-18
3819 1.0.7rc1-2 1 10007 2.1.0.7rc1-2
3820 1.0.7 1 10007 2.1.0.7
3821 1.0.8beta1-4 1 10008 2.1.0.8beta1-4
3822 1.0.8rc1 1 10008 2.1.0.8rc1
3823 1.0.8 1 10008 2.1.0.8
3824 1.0.9beta1-6 1 10009 2.1.0.9beta1-6
3825 1.0.9rc1 1 10009 2.1.0.9rc1
3826 1.0.9beta7-10 1 10009 2.1.0.9beta7-10
3827 1.0.9rc2 1 10009 2.1.0.9rc2
3828 1.0.9 1 10009 2.1.0.9
Glenn Randers-Pehrsone1644472001-03-23 05:06:56 -0600[diff] [blame]3829 1.0.10beta1 1 10010 2.1.0.10beta1
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3830 1.0.10rc1 1 10010 2.1.0.10rc1
Glenn Randers-Pehrson13cfbac2001-03-30 06:42:28 -0600[diff] [blame]3831 1.0.10 1 10010 2.1.0.10
Glenn Randers-Pehrsone1eff582001-04-14 20:15:41 -0500[diff] [blame]3832 1.0.11beta1-3 1 10011 2.1.0.11beta1-3
Glenn Randers-Pehrson82ae3832001-04-20 10:32:10 -0500[diff] [blame]3833 1.0.11rc1 1 10011 2.1.0.11rc1
Glenn Randers-Pehrson32835392001-04-27 08:29:32 -0500[diff] [blame]3834 1.0.11 1 10011 2.1.0.11
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame]3835 1.0.12beta1-2 2 10012 2.1.0.12beta1-2
3836 1.0.12rc1 2 10012 2.1.0.12rc1
3837 1.0.12 2 10012 2.1.0.12
3838 1.1.0a-f - 10100 2.1.1.0a-f abandoned
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]3839 1.2.0beta1-2 2 10200 2.1.2.0beta1-2
Glenn Randers-Pehrson5a0be342001-10-18 20:55:13 -0500[diff] [blame]3840 1.2.0beta3-5 3 10200 3.1.2.0beta3-5
3841 1.2.0rc1 3 10200 3.1.2.0rc1
3842 1.2.0 3 10200 3.1.2.0
Glenn Randers-Pehrson5cded0b2001-11-07 07:10:08 -0600[diff] [blame]3843 1.2.1beta-4 3 10201 3.1.2.1beta1-4
Glenn Randers-Pehrsondb3b88d2001-12-04 06:30:43 -0600[diff] [blame]3844 1.2.1rc1-2 3 10201 3.1.2.1rc1-2
3845 1.2.1 3 10201 3.1.2.1
Glenn Randers-Pehrson25228ab2002-03-31 07:33:55 -0600[diff] [blame]3846 1.2.2beta1-6 12 10202 12.so.0.1.2.2beta1-6
Glenn Randers-Pehrsonfcbd7872002-04-07 16:35:38 -0500[diff] [blame]3847 1.0.13beta1 10 10013 10.so.0.1.0.13beta1
3848 1.0.13rc1 10 10013 10.so.0.1.0.13rc1
3849 1.2.2rc1 12 10202 12.so.0.1.2.2rc1
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]3850 1.0.13 10 10013 10.so.0.1.0.13
3851 1.2.2 12 10202 12.so.0.1.2.2
Glenn Randers-Pehrson22f28962002-05-13 18:17:09 -0500[diff] [blame]3852 1.2.3rc1-6 12 10203 12.so.0.1.2.3rc1-6
3853 1.2.3 12 10203 12.so.0.1.2.3
Glenn Randers-Pehrsond020e9d2002-06-28 09:34:00 -0500[diff] [blame]3854 1.2.4beta1-3 13 10204 12.so.0.1.2.4beta1-3
Glenn Randers-Pehrson2ae022d2002-07-01 22:23:46 -0500[diff] [blame]3855 1.2.4rc1 13 10204 12.so.0.1.2.4rc1
Glenn Randers-Pehrson484a8a12002-07-07 19:15:20 -0500[diff] [blame]3856 1.0.14 10 10014 10.so.0.1.0.14
3857 1.2.4 13 10204 12.so.0.1.2.4
Glenn Randers-Pehrson5b5dcf82004-07-17 22:45:44 -0500[diff] [blame]3858 1.2.5beta1-2 13 10205 12.so.0.1.2.5beta1-2
3859 1.0.15rc1 10 10015 10.so.0.1.0.15rc1
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]3860 1.0.15 10 10015 10.so.0.1.0.15
3861 1.2.5 13 10205 12.so.0.1.2.5
3862 1.2.6beta1-4 13 10206 12.so.0.1.2.6beta1-4
Glenn Randers-Pehrson37f116a2004-08-15 07:15:39 -0500[diff] [blame]3863 1.2.6rc1-5 13 10206 12.so.0.1.2.6rc1-5
3864 1.0.16 10 10016 10.so.0.1.0.16
3865 1.2.6 13 10206 12.so.0.1.2.6
Glenn Randers-Pehrson67864af2004-08-28 23:30:07 -0500[diff] [blame]3866 1.2.7beta1-2 13 10207 12.so.0.1.2.7beta1-2
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]3867 1.0.17rc1 10 10017 12.so.0.1.0.17rc1
3868 1.2.7rc1 13 10207 12.so.0.1.2.7rc1
Glenn Randers-Pehrson250dfe12004-09-11 21:19:54 -0500[diff] [blame]3869 1.0.17 10 10017 12.so.0.1.0.17
3870 1.2.7 13 10207 12.so.0.1.2.7
Glenn Randers-Pehrson40936072004-11-20 11:18:40 -0600[diff] [blame]3871 1.2.8beta1-5 13 10208 12.so.0.1.2.8beta1-5
Glenn Randers-Pehrson584b96e2004-11-29 15:08:00 -0600[diff] [blame]3872 1.0.18rc1-5 10 10018 12.so.0.1.0.18rc1-5
3873 1.2.8rc1-5 13 10208 12.so.0.1.2.8rc1-5
Glenn Randers-Pehrson917648e2004-12-02 18:14:51 -0600[diff] [blame]3874 1.0.18 10 10018 12.so.0.1.0.18
3875 1.2.8 13 10208 12.so.0.1.2.8
Glenn Randers-Pehrsone6474622006-03-04 16:50:47 -0600[diff] [blame]3876 1.2.9beta1-3 13 10209 12.so.0.1.2.9beta1-3
Glenn Randers-Pehrson4deeb792006-03-22 16:21:59 -0600[diff] [blame]3877 1.2.9beta4-11 13 10209 12.so.0.9[.0]
Glenn Randers-Pehrson3a512032006-03-31 05:29:33 -0600[diff] [blame]3878 1.2.9rc1 13 10209 12.so.0.9[.0]
Glenn Randers-Pehrsona7d0c942006-04-14 06:22:52 -0500[diff] [blame]3879 1.2.9 13 10209 12.so.0.9[.0]
Glenn Randers-Pehrsond60b8fa2006-04-20 21:31:14 -0500[diff] [blame]3880 1.2.10beta1-7 13 10210 12.so.0.10[.0]
Glenn Randers-Pehrson17218292006-04-20 07:20:46 -0500[diff] [blame]3881 1.2.10rc1-2 13 10210 12.so.0.10[.0]
Glenn Randers-Pehrson86dc9812006-05-10 07:27:44 -0500[diff] [blame]3882 1.2.10 13 10210 12.so.0.10[.0]
Glenn Randers-Pehrson6bc53be2006-06-16 07:52:03 -0500[diff] [blame]3883 1.4.0beta1-6 14 10400 14.so.0.0[.0]
3884 1.2.11beta1-4 13 10210 12.so.0.10[.0]
Glenn Randers-Pehrson3424ee72006-07-12 13:33:47 -0500[diff] [blame]3885 1.4.0beta7-8 14 10400 14.so.0.0[.0]
Glenn Randers-Pehrson701dbaa2006-11-17 09:36:54 -0600[diff] [blame]3886 1.2.11 13 10211 12.so.0.11[.0]
3887 1.2.12 13 10212 12.so.0.12[.0]
3888 1.4.0beta9-14 14 10400 14.so.0.0[.0]
3889 1.2.13 13 10213 12.so.0.13[.0]
Glenn Randers-Pehrson72b63302008-07-22 13:59:07 -0500[diff] [blame]3890 1.4.0beta15-23 14 10400 14.so.0.0[.0]
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3891
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3892Henceforth the source version will match the shared-library minor
3893and patch numbers; the shared-library major version number will be
3894used for changes in backward compatibility, as it is intended. The
3895PNG_PNGLIB_VER macro, which is not used within libpng but is available
3896for applications, is an unsigned integer of the form xyyzz corresponding
3897to 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]3898were given the previous public release number plus a letter, until
3899version 1.0.6j; from then on they were given the upcoming public
3900release number plus "betaNN" or "rcN".
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3901
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3902.SH "SEE ALSO"
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3903libpngpf(3), png(5)
3904.LP
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3905.IR libpng :
3906.IP
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]3907http://libpng.sourceforge.net (follow the [DOWNLOAD] link)
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]3908http://www.libpng.org/pub/png
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3909
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3910.LP
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3911.IR zlib :
3912.IP
3913(generally) at the same location as
3914.I libpng
3915or at
3916.br
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]3917ftp://ftp.info-zip.org/pub/infozip/zlib
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3918
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3919.LP
3920.IR PNG specification: RFC 2083
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3921.IP
3922(generally) at the same location as
3923.I libpng
3924or at
3925.br
3926ftp://ds.internic.net/rfc/rfc2083.txt
3927.br
3928or (as a W3C Recommendation) at
3929.br
3930http://www.w3.org/TR/REC-png.html
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3931
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3932.LP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3933In the case of any inconsistency between the PNG specification
3934and this library, the specification takes precedence.
3935
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3936.SH AUTHORS
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3937This man page: Glenn Randers-Pehrson
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]3938<glennrp at users.sourceforge.net>
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3939
3940The contributing authors would like to thank all those who helped
3941with testing, bug fixes, and patience. This wouldn't have been
3942possible without all of you.
3943
3944Thanks to Frank J. T. Wojcik for helping with the documentation.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3945
Glenn Randers-Pehrson895a9c92008-07-25 08:51:18 -0500[diff] [blame^]3946Libpng version 1.4.0beta24 - July 25, 2008:
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3947Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]3948Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3949
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3950Supported by the PNG development group
3951.br
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]3952png-mng-implement at lists.sf.net
3953(subscription required; visit
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]3954png-mng-implement at lists.sourceforge.net (subscription required; visit
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]3955https://lists.sourceforge.net/lists/listinfo/png-mng-implement
3956to subscribe).
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3957
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]3958.SH COPYRIGHT NOTICE, DISCLAIMER, and LICENSE:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3959
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]3960(This copy of the libpng notices is provided for your convenience. In case of
3961any discrepancy between this copy and the notices in the file png.h that is
3962included in the libpng distribution, the latter shall prevail.)
3963
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]3964If you modify libpng you may insert additional notices immediately following
3965this sentence.
3966
Glenn Randers-Pehrson895a9c92008-07-25 08:51:18 -0500[diff] [blame^]3967libpng versions 1.2.6, August 15, 2004, through 1.4.0beta24, July 25, 2008, are
Glenn Randers-Pehrsona7dbcba2007-05-15 16:16:34 -0500[diff] [blame]3968Copyright (c) 2004,2006-2007 Glenn Randers-Pehrson, and are
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]3969distributed according to the same disclaimer and license as libpng-1.2.5
Glenn Randers-Pehrsond029a752004-08-09 21:50:32 -0500[diff] [blame]3970with the following individual added to the list of Contributing Authors
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]3971
3972 Cosmin Truta
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]3973
3974libpng 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]3975Copyright (c) 2000-2002 Glenn Randers-Pehrson, and are
Glenn Randers-Pehrson32fc5ce2000-07-24 06:34:14 -0500[diff] [blame]3976distributed according to the same disclaimer and license as libpng-1.0.6
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]3977with the following individuals added to the list of Contributing Authors
3978
3979 Simon-Pierre Cadieux
3980 Eric S. Raymond
3981 Gilles Vollant
3982
3983and with the following additions to the disclaimer:
3984
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3985 There is no warranty against interference with your
3986 enjoyment of the library or against infringement.
3987 There is no warranty that our efforts or the library
3988 will fulfill any of your particular purposes or needs.
3989 This library is provided with all faults, and the entire
3990 risk of satisfactory quality, performance, accuracy, and
3991 effort is with the user.
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]3992
3993libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
3994Copyright (c) 1998, 1999 Glenn Randers-Pehrson
3995Distributed according to the same disclaimer and license as libpng-0.96,
3996with the following individuals added to the list of Contributing Authors:
3997
3998 Tom Lane
3999 Glenn Randers-Pehrson
4000 Willem van Schaik
4001
4002libpng versions 0.89, June 1996, through 0.96, May 1997, are
Glenn Randers-Pehrson54a066a1999-09-19 06:04:18 -0500[diff] [blame]4003Copyright (c) 1996, 1997 Andreas Dilger
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]4004Distributed according to the same disclaimer and license as libpng-0.88,
4005with the following individuals added to the list of Contributing Authors:
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]4006
4007 John Bowler
4008 Kevin Bracey
4009 Sam Bushell
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]4010 Magnus Holmgren
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]4011 Greg Roelofs
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]4012 Tom Tanner
4013
4014libpng versions 0.5, May 1995, through 0.88, January 1996, are
4015Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
4016
4017For the purposes of this copyright and license, "Contributing Authors"
4018is defined as the following set of individuals:
4019
4020 Andreas Dilger
4021 Dave Martindale
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]4022 Guy Eric Schalnat
4023 Paul Schmidt
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]4024 Tim Wegner
Glenn Randers-Pehrsonc9442291999-01-06 21:50:16 -0600[diff] [blame]4025
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]4026The PNG Reference Library is supplied "AS IS". The Contributing Authors
4027and Group 42, Inc. disclaim all warranties, expressed or implied,
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4028including, without limitation, the warranties of merchantability and of
4029fitness for any purpose. The Contributing Authors and Group 42, Inc.
4030assume no liability for direct, indirect, incidental, special, exemplary,
4031or consequential damages, which may result from the use of the PNG
4032Reference Library, even if advised of the possibility of such damage.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4033
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4034Permission is hereby granted to use, copy, modify, and distribute this
4035source code, or portions hereof, for any purpose, without fee, subject
4036to the following restrictions:
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4037
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]40381. The origin of this source code must not be misrepresented.
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4039
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]40402. Altered versions must be plainly marked as such and
4041 must not be misrepresented as being the original source.
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4042
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]40433. This Copyright notice may not be removed or altered from
4044 any source or altered source distribution.
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4045
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4046The Contributing Authors and Group 42, Inc. specifically permit, without
4047fee, and encourage the use of this source code as a component to
4048supporting the PNG file format in commercial products. If you use this
4049source code in a product, acknowledgment is not required but would be
4050appreciated.
4051
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]4052
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]4053A "png_get_copyright" function is available, for convenient use in "about"
4054boxes and the like:
4055
4056 printf("%s",png_get_copyright(NULL));
4057
4058Also, the PNG logo (in PNG format, of course) is supplied in the
Glenn Randers-Pehrsona4d54bd2000-07-14 08:15:12 -0500[diff] [blame]4059files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31).
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]4060
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]4061Libpng is OSI Certified Open Source Software. OSI Certified Open Source is a
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]4062certification mark of the Open Source Initiative.
4063
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]4064Glenn Randers-Pehrson
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]4065glennrp at users.sourceforge.net
Glenn Randers-Pehrson895a9c92008-07-25 08:51:18 -0500[diff] [blame^]4066July 25, 2008
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]4067
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4068.\" end of man page
4069