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gerrit-public.fairphone.software / platform / external / libpng / b182893c047e5b5729bf0ebcb09067fd1fe350d7 / . / libpng.3
blob: 5b66ca847be2f5782e15c0a12bc30232584dd2ff [file] [log] [blame]
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame^]1.TH LIBPNG 3 "June 23, 2001"
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]2.SH NAME
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame^]3libpng \- Portable Network Graphics (PNG) Reference Library 1.2.0beta4
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4.SH SYNOPSIS
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]5\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]6
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]7\fB#include <png.h>\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]8
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]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
13\fI\fB
14
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]15\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]16
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]17\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]18
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]19\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]20
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]21\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]22
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]23\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]24
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]25\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]26
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]27\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]28
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]29\fI\fB
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]30
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]31\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]32
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]33\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]34
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]35\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]36
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]37\fI\fB
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]38
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]39\fBpng_infop png_create_info_struct (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]40
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]41\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]42
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]43\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]44
45\fI\fB
46
47\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
48
49\fI\fB
50
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]51\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]52
53\fI\fB
54
55\fBpng_structp png_create_write_struct_2(png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP
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57\fI\fB
58
59\fBint png_debug(int \fP\fIlevel\fP\fB, png_const_charp \fImessage\fP\fB);\fP
60
61\fI\fB
62
63\fBint png_debug1(int \fP\fIlevel\fP\fB, png_const_charp \fP\fImessage\fP\fB, \fIp1\fP\fB);\fP
64
65\fI\fB
66
67\fBint png_debug2(int \fP\fIlevel\fP\fB, png_const_charp \fP\fImessage\fP\fB, \fP\fIp1\fP\fB, \fIp2\fP\fB);\fP
68
69\fI\fB
70
71\fBvoid png_destroy_info_struct (png_structp \fP\fIpng_ptr\fP\fB, png_infopp \fIinfo_ptr_ptr\fP\fB);\fP
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73\fI\fB
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75\fBvoid png_destroy_read_struct (png_structpp \fP\fIpng_ptr_ptr\fP\fB, png_infopp \fP\fIinfo_ptr_ptr\fP\fB, png_infopp \fIend_info_ptr_ptr\fP\fB);\fP
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77\fI\fB
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79\fBvoid png_destroy_write_struct (png_structpp \fP\fIpng_ptr_ptr\fP\fB, png_infopp \fIinfo_ptr_ptr\fP\fB);\fP
80
81\fI\fB
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83\fBvoid png_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP
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85\fI\fB
86
87\fBvoid png_free (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP
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89\fI\fB
90
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]91\fBvoid png_free_chunk_list (png_structp \fIpng_ptr\fP\fB);\fP
92
93\fI\fB
94
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]95\fBvoid png_free_default(png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP
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97\fI\fB
98
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]99\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]100
101\fI\fB
102
Glenn Randers-Pehrson1fd5fb32001-05-06 05:34:26 -0500[diff] [blame]103\fBpng_uint_32 png_get_asm_flags (png_structp \fIpng_ptr\fP\fB);\fP
104
105\fI\fB
106
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]107\fBpng_byte png_get_bit_depth (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
108
109\fI\fB
110
111\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
112
113\fI\fB
114
115\fBpng_byte png_get_channels (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
116
117\fI\fB
118
119\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
120
121\fI\fB
122
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]123\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
124
125\fI\fB
126
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]127\fBpng_byte png_get_color_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
128
129\fI\fB
130
131\fBpng_byte png_get_compression_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
132
133\fI\fB
134
135\fBpng_byte png_get_copyright (png_structp \fIpng_ptr\fP\fB);\fP
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137\fI\fB
138
139\fBpng_voidp png_get_error_ptr (png_structp \fIpng_ptr\fP\fB);\fP
140
141\fI\fB
142
143\fBpng_byte png_get_filter_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
144
145\fI\fB
146
147\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
148
149\fI\fB
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Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]151\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
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153\fI\fB
154
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]155\fBpng_byte png_get_header_ver (png_structp \fIpng_ptr\fP\fB);\fP
156
157\fI\fB
158
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]159\fBpng_byte png_get_header_version (png_structp \fIpng_ptr\fP\fB);\fP
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161\fI\fB
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163\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
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165\fI\fB
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Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]167\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]168
169\fI\fB
170
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]171\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
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173\fI\fB
174
175\fBpng_uint_32 png_get_image_height (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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177\fI\fB
178
179\fBpng_uint_32 png_get_image_width (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
180
181\fI\fB
182
183\fBpng_byte png_get_interlace_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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185\fI\fB
186
187\fBpng_voidp png_get_io_ptr (png_structp \fIpng_ptr\fP\fB);\fP
188
189\fI\fB
190
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]191\fBpng_byte png_get_libpng_ver (png_structp \fIpng_ptr\fP\fB);\fP
192
193\fI\fB
194
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]195\fBpng_voidp png_get_mem_ptr(png_structp \fIpng_ptr\fP\fB);\fP
196
197\fI\fB
198
Glenn Randers-Pehrson1fd5fb32001-05-06 05:34:26 -0500[diff] [blame]199\fBpng_byte png_get_mmx_bitdepth_threshold (png_structp \fIpng_ptr\fP\fB);\fP
200
201\fI\fB
202
203\fBpng_uint_32 png_get_mmx_flagmask (int \fP\fIflag_select\fP\fB, int \fI*compilerID\fP\fB);\fP
204
205\fI\fB
206
207\fBpng_uint_32 png_get_mmx_rowbytes_threshold (png_structp \fIpng_ptr\fP\fB);\fP
208
209\fI\fB
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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
213\fI\fB
214
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
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217\fI\fB
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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
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221\fI\fB
222
223\fBfloat png_get_pixel_aspect_ratio (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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225\fI\fB
226
227\fBpng_uint_32 png_get_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
228
229\fI\fB
230
231\fBpng_voidp png_get_progressive_ptr (png_structp \fIpng_ptr\fP\fB);\fP
232
233\fI\fB
234
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
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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
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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
247\fI\fB
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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
251\fI\fB
252
253\fBpng_bytep png_get_signature (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
254
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
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
263\fI\fB
264
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
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267\fI\fB
268
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
271\fI\fB
272
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
275\fI\fB
276
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]277\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
278
279\fI\fB
280
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]281\fBpng_voidp png_get_user_chunk_ptr (png_structp \fIpng_ptr\fP\fB);\fP
282
283\fI\fB
284
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]285\fBpng_voidp png_get_user_transform_ptr (png_structp \fIpng_ptr\fP\fB);\fP
286
287\fI\fB
288
289\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
290
291\fI\fB
292
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]293\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]294
295\fI\fB
296
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]297\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]298
299\fI\fB
300
301\fBpng_uint_32 png_get_x_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
302
303\fI\fB
304
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]305\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]306
307\fI\fB
308
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]309\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]310
311\fI\fB
312
313\fBpng_uint_32 png_get_y_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
314
315\fI\fB
316
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]317\fBpng_uint_32 png_get_compression_buffer_size (png_structp \fIpng_ptr\fP\fB);\fP
318
319\fI\fB
320
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]321\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]322
323\fI\fB
324
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]325\fBDEPRECATED: void png_info_init (png_infop \fIinfo_ptr\fP\fB);\fP
326
327\fI\fB
328
329\fBDEPRECATED: void png_info_init_2 (png_infopp \fP\fIptr_ptr\fP\fB, png_size_t \fIpng_info_struct_size\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]330
331\fI\fB
332
333\fBpng_voidp png_malloc (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP
334
335\fI\fB
336
337\fBpng_voidp png_malloc_default(png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP
338
339\fI\fB
340
341\fBvoidp png_memcpy (png_voidp \fP\fIs1\fP\fB, png_voidp \fP\fIs2\fP\fB, png_size_t \fIsize\fP\fB);\fP
342
343\fI\fB
344
345\fBpng_voidp png_memcpy_check (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIs1\fP\fB, png_voidp \fP\fIs2\fP\fB, png_uint_32 \fIsize\fP\fB);\fP
346
347\fI\fB
348
349\fBvoidp png_memset (png_voidp \fP\fIs1\fP\fB, int \fP\fIvalue\fP\fB, png_size_t \fIsize\fP\fB);\fP
350
351\fI\fB
352
353\fBpng_voidp png_memset_check (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIs1\fP\fB, int \fP\fIvalue\fP\fB, png_uint_32 \fIsize\fP\fB);\fP
354
355\fI\fB
356
Glenn Randers-Pehrson1fd5fb32001-05-06 05:34:26 -0500[diff] [blame]357\fBint png_mmx_support \fI(void\fP\fB);\fP
358
359\fI\fB
360
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]361\fBDEPRECATED: void png_permit_empty_plte (png_structp \fP\fIpng_ptr\fP\fB, int \fIempty_plte_permitted\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]362
363\fI\fB
364
365\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
366
367\fI\fB
368
369\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
370
371\fI\fB
372
373\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
374
375\fI\fB
376
377\fBvoid png_read_end (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
378
379\fI\fB
380
381\fBvoid png_read_image (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fIimage\fP\fB);\fP
382
383\fI\fB
384
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]385\fBDEPRECATED: void png_read_init (png_structp \fIpng_ptr\fP\fB);\fP
386
387\fI\fB
388
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]389\fBDEPRECATED: void png_read_init_2 (png_structpp \fP\fIptr_ptr\fP\fB, png_const_charp \fP\fIuser_png_ver\fP\fB, png_size_t \fP\fIpng_struct_size\fP\fB, png_size_t \fIpng_info_size\fP\fB);\fP
390
391\fI\fB
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]392
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]393\fBvoid png_read_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
394
395\fI\fB
396
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]397\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]398
399\fI\fB
400
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]401\fBvoid png_read_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIrow\fP\fB, png_bytep \fIdisplay_row\fP\fB);\fP
402
403\fI\fB
404
405\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
406
407\fI\fB
408
409\fBvoid png_read_update_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
410
411\fI\fB
412
Glenn Randers-Pehrson1fd5fb32001-05-06 05:34:26 -0500[diff] [blame]413\fBpng_set_asm_flags (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIasm_flags\fP\fB);\fP
414
415\fI\fB
416
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]417\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
418
419\fI\fB
420
421\fBvoid png_set_bgr (png_structp \fIpng_ptr\fP\fB);\fP
422
423\fI\fB
424
425\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
426
427\fI\fB
428
429\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
430
431\fI\fB
432
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]433\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
434
435\fI\fB
436
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]437\fBvoid png_set_compression_level (png_structp \fP\fIpng_ptr\fP\fB, int \fIlevel\fP\fB);\fP
438
439\fI\fB
440
441\fBvoid png_set_compression_mem_level (png_structp \fP\fIpng_ptr\fP\fB, int \fImem_level\fP\fB);\fP
442
443\fI\fB
444
445\fBvoid png_set_compression_method (png_structp \fP\fIpng_ptr\fP\fB, int \fImethod\fP\fB);\fP
446
447\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]448
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]449\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]450
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]451\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]452
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]453\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]454
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]455\fI\fB
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]456
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]457\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]458
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]459\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]460
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]461\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]462
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]463\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]464
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]465\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]466
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]467\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]468
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]469\fBvoid png_set_expand (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]470
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]471\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]472
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]473\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]474
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]475\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]476
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]477\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]478
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]479\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]480
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]481\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]482
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]483\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]484
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]485\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]486
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]487\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]488
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]489\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]490
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]491\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]492
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]493\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]494
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]495\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]496
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]497\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
498
499\fI\fB
500
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]501\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]502
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]503\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]504
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]505\fBvoid png_set_gray_to_rgb (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]506
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]507\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]508
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]509\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]510
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]511\fI\fB
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]512
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]513\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]514
515\fI\fB
516
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]517\fBint png_set_interlace_handling (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]518
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]519\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]520
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]521\fBvoid png_set_invalid (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fImask\fP\fB);\fP
522
523\fI\fB
524
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]525\fBvoid png_set_invert_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]526
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]527\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]528
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]529\fBvoid png_set_invert_mono (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]530
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]531\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]532
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]533\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]534
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]535\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]536
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]537\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]538
539\fI\fB
540
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]541\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]542
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]543\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]544
Glenn Randers-Pehrson1fd5fb32001-05-06 05:34:26 -0500[diff] [blame]545\fBpng_set_mmx_thresholds (png_structp \fP\fIpng_ptr\fP\fB, png_byte \fP\fImmx_bitdepth_threshold\fP\fB, png_uint_32 \fImmx_rowbytes_threshold\fP\fB);\fP
546
547\fI\fB
548
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]549\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]550
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]551\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]552
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]553\fBvoid png_set_packing (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]554
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]555\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]556
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]557\fBvoid png_set_packswap (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]558
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]559\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]560
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]561\fBvoid png_set_palette_to_rgb(png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]562
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]563\fI\fB
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]564
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]565\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]566
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]567\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]568
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]569\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]570
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]571\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]572
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]573\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]574
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]575\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]576
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]577\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]578
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]579\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]580
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]581\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]582
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]583\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]584
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]585\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]586
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]587\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]588
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]589\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]590
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]591\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]592
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]593\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
594
595\fI\fB
596
597\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]598
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]599\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]600
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]601\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
602
603\fI\fB
604
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]605\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]606
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]607\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]608
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]609\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
610
611\fI\fB
612
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]613\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]614
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]615\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]616
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]617\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]618
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]619\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]620
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]621\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]622
623\fI\fB
624
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]625\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]626
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]627\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]628
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]629\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]630
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]631\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]632
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]633\fBvoid png_set_strip_16 (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]634
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]635\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]636
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]637\fBvoid png_set_strip_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]638
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]639\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]640
Glenn Randers-Pehrson1fd5fb32001-05-06 05:34:26 -0500[diff] [blame]641\fBvoid png_set_strip_error_numbers (png_structp \fIpng_ptr,
642
643\fBpng_uint_32 \fIstrip_mode\fP\fB);\fP
644
645\fI\fB
646
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]647\fBvoid png_set_swap (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]648
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]649\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]650
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]651\fBvoid png_set_swap_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]652
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]653\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]654
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]655\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]656
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]657\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]658
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]659\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]660
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]661\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]662
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]663\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]664
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]665\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]666
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]667\fBvoid png_set_tRNS_to_alpha(png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]668
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]669\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]670
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]671\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
672
673\fI\fB
674
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]675\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
676
677\fI\fB
678
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]679\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]680
681\fI\fB
682
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]683\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]684
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]685\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]686
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]687\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]688
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]689\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]690
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]691\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]692
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]693\fI\fB
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]694
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]695\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]696
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]697\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]698
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]699\fBvoid png_set_compression_buffer_size(png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP
700
701\fI\fB
702
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]703\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]704
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]705\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]706
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]707\fBvoid png_start_read_image (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]708
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]709\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]710
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]711\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]712
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]713\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]714
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]715\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]716
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]717\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]718
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]719\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]720
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]721\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]722
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]723\fBvoid png_write_chunk_end (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]724
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]725\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]726
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]727\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]728
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]729\fI\fB
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]730
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]731\fBvoid png_write_destroy (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]732
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]733\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]734
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]735\fBvoid png_write_destroy_info (png_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]736
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]737\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]738
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]739\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]740
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]741\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]742
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]743\fBvoid png_write_flush (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]744
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]745\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]746
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]747\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]748
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]749\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]750
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]751\fBDEPRECATED: void png_write_init (png_structp \fIpng_ptr\fP\fB);\fP
752
753\fI\fB
754
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]755\fBDEPRECATED: void png_write_init_2 (png_structpp \fP\fIptr_ptr\fP\fB, png_const_charp \fP\fIuser_png_ver\fP\fB, png_size_t \fP\fIpng_struct_size\fP\fB, png_size_t \fIpng_info_size\fP\fB);\fP
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]756
757\fI\fB
758
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]759\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]760
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]761\fI\fB
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]762
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]763\fBvoid png_write_info_before_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
764
765\fI\fB
766
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]767\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]768
769\fI\fB
770
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]771\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]772
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]773\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]774
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]775\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]776
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]777\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]778
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]779.SH DESCRIPTION
780The
781.I libpng
782library supports encoding, decoding, and various manipulations of
783the Portable Network Graphics (PNG) format image files. It uses the
784.IR zlib(3)
785compression library.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]786Following is a copy of the libpng.txt file that accompanies libpng.
787.SH LIBPNG.TXT
788libpng.txt - A description on how to use and modify libpng
789
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame^]790 libpng version 1.2.0beta4 - June 23, 2001
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]791 Updated and distributed by Glenn Randers-Pehrson
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]792 <randeg@alum.rpi.edu>
Glenn Randers-Pehrsone68f5a32001-05-14 09:20:53 -0500[diff] [blame]793 Copyright (c) 1998-2001 Glenn Randers-Pehrson
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]794 For conditions of distribution and use, see copyright
795 notice in png.h.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]796
797 based on:
798
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]799 libpng 1.0 beta 6 version 0.96 May 28, 1997
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]800 Updated and distributed by Andreas Dilger
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]801 Copyright (c) 1996, 1997 Andreas Dilger
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]802
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]803 libpng 1.0 beta 2 - version 0.88 January 26, 1996
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]804 For conditions of distribution and use, see copyright
805 notice in png.h. Copyright (c) 1995, 1996 Guy Eric
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]806 Schalnat, Group 42, Inc.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]807
808 Updated/rewritten per request in the libpng FAQ
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]809 Copyright (c) 1995, 1996 Frank J. T. Wojcik
810 December 18, 1995 & January 20, 1996
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]811
812.SH I. Introduction
813
814This file describes how to use and modify the PNG reference library
815(known as libpng) for your own use. There are five sections to this
816file: introduction, structures, reading, writing, and modification and
817configuration notes for various special platforms. In addition to this
818file, example.c is a good starting point for using the library, as
819it is heavily commented and should include everything most people
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]820will need. We assume that libpng is already installed; see the
821INSTALL file for instructions on how to install libpng.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]822
823Libpng was written as a companion to the PNG specification, as a way
824of reducing the amount of time and effort it takes to support the PNG
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]825file format in application programs.
826
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]827The PNG-1.2 specification is available at <http://www.libpng.org/pub/png>
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]828and at <ftp://ftp.uu.net/graphics/png/documents/>.
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]829
830The PNG-1.0 specification is available
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]831as RFC 2083 <ftp://ftp.uu.net/graphics/png/documents/> and as a
832W3C Recommendation <http://www.w3.org/TR/REC.png.html>. Some
833additional chunks are described in the special-purpose public chunks
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]834documents at <ftp://ftp.uu.net/graphics/png/documents/>.
835
836Other information
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]837about PNG, and the latest version of libpng, can be found at the PNG home
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]838page, <http://www.libpng.org/pub/png/>
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]839and at <ftp://ftp.uu.net/graphics/png/>.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]840
841Most users will not have to modify the library significantly; advanced
842users may want to modify it more. All attempts were made to make it as
843complete as possible, while keeping the code easy to understand.
844Currently, this library only supports C. Support for other languages
845is being considered.
846
847Libpng has been designed to handle multiple sessions at one time,
848to be easily modifiable, to be portable to the vast majority of
849machines (ANSI, K&R, 16-, 32-, and 64-bit) available, and to be easy
850to use. The ultimate goal of libpng is to promote the acceptance of
851the PNG file format in whatever way possible. While there is still
852work to be done (see the TODO file), libpng should cover the
853majority of the needs of its users.
854
855Libpng uses zlib for its compression and decompression of PNG files.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]856Further information about zlib, and the latest version of zlib, can
Glenn Randers-Pehrsond56aca72000-11-23 11:51:42 -0600[diff] [blame]857be 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]858The zlib compression utility is a general purpose utility that is
859useful for more than PNG files, and can be used without libpng.
860See the documentation delivered with zlib for more details.
861You can usually find the source files for the zlib utility wherever you
862find the libpng source files.
863
864Libpng is thread safe, provided the threads are using different
865instances of the structures. Each thread should have its own
866png_struct and png_info instances, and thus its own image.
867Libpng does not protect itself against two threads using the
868same instance of a structure.
869
870
871.SH II. Structures
872
873There are two main structures that are important to libpng, png_struct
874and png_info. The first, png_struct, is an internal structure that
875will 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]876variable passed to every libpng function call.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]877
878The png_info structure is designed to provide information about the
879PNG file. At one time, the fields of png_info were intended to be
880directly accessible to the user. However, this tended to cause problems
881with applications using dynamically loaded libraries, and as a result
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]882a set of interface functions for png_info (the png_get_*() and png_set_*()
883functions) was developed. The fields of png_info are still available for
884older applications, but it is suggested that applications use the new
885interfaces if at all possible.
886
887Applications that do make direct access to the members of png_struct (except
888for png_ptr->jmpbuf) must be recompiled whenever the library is updated,
889and applications that make direct access to the members of png_info must
890be recompiled if they were compiled or loaded with libpng version 1.0.6,
891in which the members were in a different order. In version 1.0.7, the
892members of the png_info structure reverted to the old order, as they were
893in versions 0.97c through 1.0.5. Starting with version 2.0.0, both
894structures are going to be hidden, and the contents of the structures will
895only be accessible through the png_get/png_set functions.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]896
897The png.h header file is an invaluable reference for programming with libpng.
898And while I'm on the topic, make sure you include the libpng header file:
899
900#include <png.h>
901
902.SH III. Reading
903
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]904We'll now walk you through the possible functions to call when reading
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]905in a PNG file sequentially, briefly explaining the syntax and purpose
906of each one. See example.c and png.h for more detail. While
907progressive reading is covered in the next section, you will still
908need some of the functions discussed in this section to read a PNG
909file.
910
911.SS Setup
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]912
913You will want to do the I/O initialization(*) before you get into libpng,
914so if it doesn't work, you don't have much to undo. Of course, you
915will also want to insure that you are, in fact, dealing with a PNG
916file. 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]917To use it, pass in the first 1 to 8 bytes of the file to the function
918png_sig_cmp(), and it will return 0 if the bytes match the corresponding
919bytes of the PNG signature, or nonzero otherwise. Of course, the more bytes
920you pass in, the greater the accuracy of the prediction.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]921
922If you are intending to keep the file pointer open for use in libpng,
923you must ensure you don't read more than 8 bytes from the beginning
924of the file, and you also have to make a call to png_set_sig_bytes_read()
925with the number of bytes you read from the beginning. Libpng will
926then only check the bytes (if any) that your program didn't read.
927
928(*): If you are not using the standard I/O functions, you will need
929to replace them with custom functions. See the discussion under
930Customizing libpng.
931
932
933 FILE *fp = fopen(file_name, "rb");
934 if (!fp)
935 {
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]936 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]937 }
938 fread(header, 1, number, fp);
Glenn Randers-Pehrsonc9442291999-01-06 21:50:16 -0600[diff] [blame]939 is_png = !png_sig_cmp(header, 0, number);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]940 if (!is_png)
941 {
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]942 return (NOT_PNG);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]943 }
944
945
946Next, png_struct and png_info need to be allocated and initialized. In
947order to ensure that the size of these structures is correct even with a
948dynamically linked libpng, there are functions to initialize and
949allocate the structures. We also pass the library version, optional
950pointers to error handling functions, and a pointer to a data struct for
951use by the error functions, if necessary (the pointer and functions can
952be NULL if the default error handlers are to be used). See the section
953on Changes to Libpng below regarding the old initialization functions.
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]954The structure allocation functions quietly return NULL if they fail to
955create the structure, so your application should check for that.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]956
957 png_structp png_ptr = png_create_read_struct
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]958 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]959 user_error_fn, user_warning_fn);
960 if (!png_ptr)
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]961 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]962
963 png_infop info_ptr = png_create_info_struct(png_ptr);
964 if (!info_ptr)
965 {
966 png_destroy_read_struct(&png_ptr,
967 (png_infopp)NULL, (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]968 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]969 }
970
971 png_infop end_info = png_create_info_struct(png_ptr);
972 if (!end_info)
973 {
974 png_destroy_read_struct(&png_ptr, &info_ptr,
975 (png_infopp)NULL);
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
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]979If you want to use your own memory allocation routines,
980define PNG_USER_MEM_SUPPORTED and use
981png_create_read_struct_2() instead of png_create_read_struct():
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]982
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]983 png_structp png_ptr = png_create_read_struct_2
984 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
985 user_error_fn, user_warning_fn, (png_voidp)
986 user_mem_ptr, user_malloc_fn, user_free_fn);
987
988The error handling routines passed to png_create_read_struct()
989and the memory alloc/free routines passed to png_create_struct_2()
990are only necessary if you are not using the libpng supplied error
991handling and memory alloc/free functions.
992
993When libpng encounters an error, it expects to longjmp back
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]994to your routine. Therefore, you will need to call setjmp and pass
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]995your png_jmpbuf(png_ptr). If you read the file from different
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]996routines, you will need to update the jmpbuf field every time you enter
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]997a new routine that will call a png_*() function.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]998
999See your documentation of setjmp/longjmp for your compiler for more
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]1000information on setjmp/longjmp. See the discussion on libpng error
1001handling in the Customizing Libpng section below for more information
1002on the libpng error handling. If an error occurs, and libpng longjmp's
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1003back to your setjmp, you will want to call png_destroy_read_struct() to
1004free any memory.
1005
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1006 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1007 {
1008 png_destroy_read_struct(&png_ptr, &info_ptr,
1009 &end_info);
1010 fclose(fp);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]1011 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1012 }
1013
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1014If you would rather avoid the complexity of setjmp/longjmp issues,
1015you can compile libpng with PNG_SETJMP_NOT_SUPPORTED, in which case
1016errors will result in a call to PNG_ABORT() which defaults to abort().
1017
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1018Now you need to set up the input code. The default for libpng is to
1019use the C function fread(). If you use this, you will need to pass a
1020valid FILE * in the function png_init_io(). Be sure that the file is
1021opened in binary mode. If you wish to handle reading data in another
1022way, you need not call the png_init_io() function, but you must then
1023implement the libpng I/O methods discussed in the Customizing Libpng
1024section below.
1025
1026 png_init_io(png_ptr, fp);
1027
1028If you had previously opened the file and read any of the signature from
1029the beginning in order to see if this was a PNG file, you need to let
1030libpng know that there are some bytes missing from the start of the file.
1031
1032 png_set_sig_bytes(png_ptr, number);
1033
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1034.SS Setting up callback code
1035
1036You can set up a callback function to handle any unknown chunks in the
1037input stream. You must supply the function
1038
1039 read_chunk_callback(png_ptr ptr,
1040 png_unknown_chunkp chunk);
1041 {
1042 /* The unknown chunk structure contains your
1043 chunk data: */
1044 png_byte name[5];
1045 png_byte *data;
1046 png_size_t size;
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1047 /* Note that libpng has already taken care of
1048 the CRC handling */
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1049
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1050 /* put your code here. Return one of the
1051 following: */
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1052
1053 return (-n); /* chunk had an error */
1054 return (0); /* did not recognize */
1055 return (n); /* success */
1056 }
1057
1058(You can give your function another name that you like instead of
1059"read_chunk_callback")
1060
1061To inform libpng about your function, use
1062
1063 png_set_read_user_chunk_fn(png_ptr, user_chunk_ptr,
1064 read_chunk_callback);
1065
1066This names not only the callback function, but also a user pointer that
1067you can retrieve with
1068
1069 png_get_user_chunk_ptr(png_ptr);
1070
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]1071At this point, you can set up a callback function that will be
1072called after each row has been read, which you can use to control
1073a progress meter or the like. It's demonstrated in pngtest.c.
1074You must supply a function
1075
Glenn Randers-Pehrsone68f5a32001-05-14 09:20:53 -0500[diff] [blame]1076 void read_row_callback(png_ptr ptr, png_uint_32 row,
1077 int pass);
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]1078 {
1079 /* put your code here */
1080 }
1081
1082(You can give it another name that you like instead of "read_row_callback")
1083
1084To inform libpng about your function, use
1085
1086 png_set_read_status_fn(png_ptr, read_row_callback);
1087
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1088.SS Unknown-chunk handling
1089
1090Now you get to set the way the library processes unknown chunks in the
1091input PNG stream. Both known and unknown chunks will be read. Normal
1092behavior is that known chunks will be parsed into information in
1093various info_ptr members; unknown chunks will be discarded. To change
1094this, you can call:
1095
1096 png_set_keep_unknown_chunks(png_ptr, info_ptr, keep,
1097 chunk_list, num_chunks);
1098 keep - 0: do not keep
1099 1: keep only if safe-to-copy
1100 2: keep even if unsafe-to-copy
1101 chunk_list - list of chunks affected (a byte string,
1102 five bytes per chunk, NULL or '\0' if
1103 num_chunks is 0)
1104 num_chunks - number of chunks affected; if 0, all
1105 unknown chunks are affected
1106
1107Unknown chunks declared in this way will be saved as raw data onto a
1108list of png_unknown_chunk structures. If a chunk that is normally
1109known to libpng is named in the list, it will be handled as unknown,
1110according to the "keep" directive. If a chunk is named in successive
1111instances of png_set_keep_unknown_chunks(), the final instance will
1112take precedence.
1113
1114.SS The high-level read interface
1115
1116At this point there are two ways to proceed; through the high-level
1117read interface, or through a sequence of low-level read operations.
1118You can use the high-level interface if (a) you are willing to read
1119the entire image into memory, and (b) the input transformations
1120you want to do are limited to the following set:
1121
1122 PNG_TRANSFORM_IDENTITY No transformation
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1123 PNG_TRANSFORM_STRIP_16 Strip 16-bit samples to
1124 8 bits
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1125 PNG_TRANSFORM_STRIP_ALPHA Discard the alpha channel
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1126 PNG_TRANSFORM_PACKING Expand 1, 2 and 4-bit
1127 samples to bytes
1128 PNG_TRANSFORM_PACKSWAP Change order of packed
1129 pixels to LSB first
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1130 PNG_TRANSFORM_EXPAND Perform set_expand()
1131 PNG_TRANSFORM_INVERT_MONO Invert monochrome images
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1132 PNG_TRANSFORM_SHIFT Normalize pixels to the
1133 sBIT depth
1134 PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA
1135 to BGRA
1136 PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA
1137 to AG
1138 PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity
1139 to transparency
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1140 PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples
1141
1142(This excludes setting a background color, doing gamma transformation,
1143dithering, and setting filler.) If this is the case, simply do this:
1144
1145 png_read_png(png_ptr, info_ptr, png_transforms, NULL)
1146
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1147where png_transforms is an integer containing the logical OR of
1148some set of transformation flags. This call is equivalent to png_read_info(),
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1149followed the set of transformations indicated by the transform mask,
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1150then png_read_image(), and finally png_read_end().
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1151
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1152(The final parameter of this call is not yet used. Someday it might point
1153to transformation parameters required by some future input transform.)
1154
1155After you have called png_read_png(), you can retrieve the image data
1156with
1157
1158 row_pointers = png_get_rows(png_ptr, info_ptr);
1159
1160where row_pointers is an array of pointers to the pixel data for each row:
1161
1162 png_bytep row_pointers[height];
1163
1164If you know your image size and pixel size ahead of time, you can allocate
1165row_pointers prior to calling png_read_png() with
1166
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1167 row_pointers = png_malloc(png_ptr,
1168 height*sizeof(png_bytep));
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1169 for (int i=0; i<height, i++)
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1170 row_pointers[i]=png_malloc(png_ptr,
1171 width*pixel_size);
Glenn Randers-Pehrsond56aca72000-11-23 11:51:42 -0600[diff] [blame]1172 png_set_rows(png_ptr, info_ptr, &row_pointers);
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1173
1174Alternatively you could allocate your image in one big block and define
1175row_pointers[i] to point into the proper places in your block.
1176
1177If you use png_set_rows(), the application is responsible for freeing
1178row_pointers (and row_pointers[i], if they were separately allocated).
1179
1180If you don't allocate row_pointers ahead of time, png_read_png() will
1181do it, and it'll be free'ed when you call png_destroy_*().
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1182
1183.SS The low-level read interface
1184
1185If you are going the low-level route, you are now ready to read all
1186the file information up to the actual image data. You do this with a
1187call to png_read_info().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1188
1189 png_read_info(png_ptr, info_ptr);
1190
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1191This will process all chunks up to but not including the image data.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1192
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1193.SS Querying the info structure
1194
1195Functions are used to get the information from the info_ptr once it
1196has been read. Note that these fields may not be completely filled
1197in until png_read_end() has read the chunk data following the image.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1198
1199 png_get_IHDR(png_ptr, info_ptr, &width, &height,
1200 &bit_depth, &color_type, &interlace_type,
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]1201 &compression_type, &filter_method);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1202
1203 width - holds the width of the image
1204 in pixels (up to 2^31).
1205 height - holds the height of the image
1206 in pixels (up to 2^31).
1207 bit_depth - holds the bit depth of one of the
1208 image channels. (valid values are
1209 1, 2, 4, 8, 16 and depend also on
1210 the color_type. See also
1211 significant bits (sBIT) below).
1212 color_type - describes which color/alpha channels
1213 are present.
1214 PNG_COLOR_TYPE_GRAY
1215 (bit depths 1, 2, 4, 8, 16)
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1216 PNG_COLOR_TYPE_GRAY_ALPHA
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1217 (bit depths 8, 16)
1218 PNG_COLOR_TYPE_PALETTE
1219 (bit depths 1, 2, 4, 8)
1220 PNG_COLOR_TYPE_RGB
1221 (bit_depths 8, 16)
1222 PNG_COLOR_TYPE_RGB_ALPHA
1223 (bit_depths 8, 16)
1224
1225 PNG_COLOR_MASK_PALETTE
1226 PNG_COLOR_MASK_COLOR
1227 PNG_COLOR_MASK_ALPHA
1228
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]1229 filter_method - (must be PNG_FILTER_TYPE_BASE
1230 for PNG 1.0, and can also be
1231 PNG_INTRAPIXEL_DIFFERENCING if
1232 the PNG datastream is embedded in
1233 a MNG-1.0 datastream)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1234 compression_type - (must be PNG_COMPRESSION_TYPE_BASE
1235 for PNG 1.0)
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1236 interlace_type - (PNG_INTERLACE_NONE or
1237 PNG_INTERLACE_ADAM7)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1238 Any or all of interlace_type, compression_type, of
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1239 filter_method can be NULL if you are
1240 not interested in their values.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1241
1242 channels = png_get_channels(png_ptr, info_ptr);
1243 channels - number of channels of info for the
1244 color type (valid values are 1 (GRAY,
1245 PALETTE), 2 (GRAY_ALPHA), 3 (RGB),
1246 4 (RGB_ALPHA or RGB + filler byte))
1247 rowbytes = png_get_rowbytes(png_ptr, info_ptr);
1248 rowbytes - number of bytes needed to hold a row
1249
1250 signature = png_get_signature(png_ptr, info_ptr);
1251 signature - holds the signature read from the
1252 file (if any). The data is kept in
1253 the same offset it would be if the
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1254 whole signature were read (i.e. if an
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1255 application had already read in 4
1256 bytes of signature before starting
1257 libpng, the remaining 4 bytes would
1258 be in signature[4] through signature[7]
1259 (see png_set_sig_bytes())).
1260
1261
1262 width = png_get_image_width(png_ptr,
1263 info_ptr);
1264 height = png_get_image_height(png_ptr,
1265 info_ptr);
1266 bit_depth = png_get_bit_depth(png_ptr,
1267 info_ptr);
1268 color_type = png_get_color_type(png_ptr,
1269 info_ptr);
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]1270 filter_method = png_get_filter_type(png_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1271 info_ptr);
1272 compression_type = png_get_compression_type(png_ptr,
1273 info_ptr);
1274 interlace_type = png_get_interlace_type(png_ptr,
1275 info_ptr);
1276
1277
1278These are also important, but their validity depends on whether the chunk
1279has been read. The png_get_valid(png_ptr, info_ptr, PNG_INFO_<chunk>) and
1280png_get_<chunk>(png_ptr, info_ptr, ...) functions return non-zero if the
1281data has been read, or zero if it is missing. The parameters to the
1282png_get_<chunk> are set directly if they are simple data types, or a pointer
1283into the info_ptr is returned for any complex types.
1284
1285 png_get_PLTE(png_ptr, info_ptr, &palette,
1286 &num_palette);
1287 palette - the palette for the file
1288 (array of png_color)
1289 num_palette - number of entries in the palette
1290
1291 png_get_gAMA(png_ptr, info_ptr, &gamma);
1292 gamma - the gamma the file is written
1293 at (PNG_INFO_gAMA)
1294
1295 png_get_sRGB(png_ptr, info_ptr, &srgb_intent);
1296 srgb_intent - the rendering intent (PNG_INFO_sRGB)
1297 The presence of the sRGB chunk
1298 means that the pixel data is in the
1299 sRGB color space. This chunk also
1300 implies specific values of gAMA and
1301 cHRM.
1302
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1303 png_get_iCCP(png_ptr, info_ptr, &name,
1304 &compression_type, &profile, &proflen);
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1305 name - The profile name.
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1306 compression - The compression type; always
1307 PNG_COMPRESSION_TYPE_BASE for PNG 1.0.
1308 You may give NULL to this argument to
1309 ignore it.
1310 profile - International Color Consortium color
1311 profile data. May contain NULs.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1312 proflen - length of profile data in bytes.
1313
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1314 png_get_sBIT(png_ptr, info_ptr, &sig_bit);
1315 sig_bit - the number of significant bits for
1316 (PNG_INFO_sBIT) each of the gray,
1317 red, green, and blue channels,
1318 whichever are appropriate for the
1319 given color type (png_color_16)
1320
1321 png_get_tRNS(png_ptr, info_ptr, &trans, &num_trans,
1322 &trans_values);
1323 trans - array of transparent entries for
1324 palette (PNG_INFO_tRNS)
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]1325 trans_values - graylevel or color sample values of
1326 the single transparent color for
1327 non-paletted images (PNG_INFO_tRNS)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1328 num_trans - number of transparent entries
1329 (PNG_INFO_tRNS)
1330
1331 png_get_hIST(png_ptr, info_ptr, &hist);
1332 (PNG_INFO_hIST)
1333 hist - histogram of palette (array of
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1334 png_uint_16)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1335
1336 png_get_tIME(png_ptr, info_ptr, &mod_time);
1337 mod_time - time image was last modified
1338 (PNG_VALID_tIME)
1339
1340 png_get_bKGD(png_ptr, info_ptr, &background);
1341 background - background color (PNG_VALID_bKGD)
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1342 valid 16-bit red, green and blue
1343 values, regardless of color_type
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1344
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]1345 num_comments = png_get_text(png_ptr, info_ptr,
1346 &text_ptr, &num_text);
1347 num_comments - number of comments
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1348 text_ptr - array of png_text holding image
1349 comments
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1350 text_ptr[i].compression - type of compression used
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1351 on "text" PNG_TEXT_COMPRESSION_NONE
1352 PNG_TEXT_COMPRESSION_zTXt
1353 PNG_ITXT_COMPRESSION_NONE
1354 PNG_ITXT_COMPRESSION_zTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1355 text_ptr[i].key - keyword for comment. Must contain
1356 1-79 characters.
1357 text_ptr[i].text - text comments for current
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]1358 keyword. Can be empty.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1359 text_ptr[i].text_length - length of text string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1360 after decompression, 0 for iTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1361 text_ptr[i].itxt_length - length of itxt string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1362 after decompression, 0 for tEXt/zTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1363 text_ptr[i].lang - language of comment (empty
1364 string for unknown).
1365 text_ptr[i].translated_keyword - keyword in UTF-8
1366 (empty string for unknown).
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1367 num_text - number of comments (same as
1368 num_comments; you can put NULL here
1369 to avoid the duplication)
1370 Note while png_set_text() will accept text, language,
1371 and translated keywords that can be NULL pointers, the
1372 structure returned by png_get_text will always contain
1373 regular zero-terminated C strings. They might be
1374 empty strings but they will never be NULL pointers.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1375
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1376 num_spalettes = png_get_sPLT(png_ptr, info_ptr,
1377 &palette_ptr);
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1378 palette_ptr - array of palette structures holding
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1379 contents of one or more sPLT chunks
1380 read.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1381 num_spalettes - number of sPLT chunks read.
1382
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1383 png_get_oFFs(png_ptr, info_ptr, &offset_x, &offset_y,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1384 &unit_type);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1385 offset_x - positive offset from the left edge
1386 of the screen
1387 offset_y - positive offset from the top edge
1388 of the screen
1389 unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
1390
1391 png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1392 &unit_type);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1393 res_x - pixels/unit physical resolution in
1394 x direction
1395 res_y - pixels/unit physical resolution in
1396 x direction
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1397 unit_type - PNG_RESOLUTION_UNKNOWN,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1398 PNG_RESOLUTION_METER
1399
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1400 png_get_sCAL(png_ptr, info_ptr, &unit, &width,
1401 &height)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1402 unit - physical scale units (an integer)
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1403 width - width of a pixel in physical scale units
1404 height - height of a pixel in physical scale units
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1405 (width and height are doubles)
1406
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1407 png_get_sCAL_s(png_ptr, info_ptr, &unit, &width,
1408 &height)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1409 unit - physical scale units (an integer)
1410 width - width of a pixel in physical scale units
1411 height - height of a pixel in physical scale units
1412 (width and height are strings like "2.54")
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1413
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1414 num_unknown_chunks = png_get_unknown_chunks(png_ptr,
1415 info_ptr, &unknowns)
1416 unknowns - array of png_unknown_chunk
1417 structures holding unknown chunks
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1418 unknowns[i].name - name of unknown chunk
1419 unknowns[i].data - data of unknown chunk
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1420 unknowns[i].size - size of unknown chunk's data
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1421 unknowns[i].location - position of chunk in file
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1422
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1423 The value of "i" corresponds to the order in which the
1424 chunks were read from the PNG file or inserted with the
1425 png_set_unknown_chunks() function.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1426
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1427The data from the pHYs chunk can be retrieved in several convenient
1428forms:
1429
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1430 res_x = png_get_x_pixels_per_meter(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1431 info_ptr)
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1432 res_y = png_get_y_pixels_per_meter(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1433 info_ptr)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1434 res_x_and_y = png_get_pixels_per_meter(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1435 info_ptr)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1436 res_x = png_get_x_pixels_per_inch(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1437 info_ptr)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1438 res_y = png_get_y_pixels_per_inch(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1439 info_ptr)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1440 res_x_and_y = png_get_pixels_per_inch(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1441 info_ptr)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1442 aspect_ratio = png_get_pixel_aspect_ratio(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1443 info_ptr)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1444
1445 (Each of these returns 0 [signifying "unknown"] if
1446 the data is not present or if res_x is 0;
1447 res_x_and_y is 0 if res_x != res_y)
1448
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1449The data from the oFFs chunk can be retrieved in several convenient
1450forms:
1451
1452 x_offset = png_get_x_offset_microns(png_ptr, info_ptr);
1453 y_offset = png_get_y_offset_microns(png_ptr, info_ptr);
1454 x_offset = png_get_x_offset_inches(png_ptr, info_ptr);
1455 y_offset = png_get_y_offset_inches(png_ptr, info_ptr);
1456
1457 (Each of these returns 0 [signifying "unknown" if both
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1458 x and y are 0] if the data is not present or if the
1459 chunk is present but the unit is the pixel)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1460
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1461For more information, see the png_info definition in png.h and the
1462PNG specification for chunk contents. Be careful with trusting
1463rowbytes, as some of the transformations could increase the space
1464needed to hold a row (expand, filler, gray_to_rgb, etc.).
1465See png_read_update_info(), below.
1466
1467A quick word about text_ptr and num_text. PNG stores comments in
1468keyword/text pairs, one pair per chunk, with no limit on the number
1469of text chunks, and a 2^31 byte limit on their size. While there are
1470suggested keywords, there is no requirement to restrict the use to these
1471strings. It is strongly suggested that keywords and text be sensible
1472to humans (that's the point), so don't use abbreviations. Non-printing
1473symbols are not allowed. See the PNG specification for more details.
1474There is also no requirement to have text after the keyword.
1475
1476Keywords should be limited to 79 Latin-1 characters without leading or
1477trailing spaces, but non-consecutive spaces are allowed within the
1478keyword. It is possible to have the same keyword any number of times.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1479The text_ptr is an array of png_text structures, each holding a
1480pointer to a language string, a pointer to a keyword and a pointer to
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1481a text string. The text string, language code, and translated
1482keyword may be empty or NULL pointers. The keyword/text
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1483pairs are put into the array in the order that they are received.
1484However, some or all of the text chunks may be after the image, so, to
1485make sure you have read all the text chunks, don't mess with these
1486until after you read the stuff after the image. This will be
1487mentioned again below in the discussion that goes with png_read_end().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1488
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1489.SS Input transformations
1490
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1491After you've read the header information, you can set up the library
1492to handle any special transformations of the image data. The various
1493ways to transform the data will be described in the order that they
1494should occur. This is important, as some of these change the color
1495type and/or bit depth of the data, and some others only work on
1496certain color types and bit depths. Even though each transformation
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1497checks 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]1498make sure to only enable a transformation if it will be valid for the
1499data. For example, don't swap red and blue on grayscale data.
1500
1501The colors used for the background and transparency values should be
1502supplied in the same format/depth as the current image data. They
1503are stored in the same format/depth as the image data in a bKGD or tRNS
1504chunk, so this is what libpng expects for this data. The colors are
1505transformed to keep in sync with the image data when an application
1506calls the png_read_update_info() routine (see below).
1507
1508Data will be decoded into the supplied row buffers packed into bytes
1509unless the library has been told to transform it into another format.
1510For example, 4 bit/pixel paletted or grayscale data will be returned
15112 pixels/byte with the leftmost pixel in the high-order bits of the
1512byte, unless png_set_packing() is called. 8-bit RGB data will be stored
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]1513in RGB RGB RGB format unless png_set_filler() is called to insert filler
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1514bytes, either before or after each RGB triplet. 16-bit RGB data will
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]1515be returned RRGGBB RRGGBB, with the most significant byte of the color
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1516value first, unless png_set_strip_16() is called to transform it to
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]1517regular RGB RGB triplets, or png_set_filler() is called to insert
1518filler bytes, either before or after each RRGGBB triplet. Similarly,
15198-bit or 16-bit grayscale data can be modified with png_set_filler()
1520or png_set_strip_16().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1521
1522The following code transforms grayscale images of less than 8 to 8 bits,
1523changes paletted images to RGB, and adds a full alpha channel if there is
1524transparency information in a tRNS chunk. This is most useful on
1525grayscale images with bit depths of 2 or 4 or if there is a multiple-image
1526viewing application that wishes to treat all images in the same way.
1527
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]1528 if (color_type == PNG_COLOR_TYPE_PALETTE)
1529 png_set_palette_to_rgb(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1530
1531 if (color_type == PNG_COLOR_TYPE_GRAY &&
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]1532 bit_depth < 8) png_set_gray_1_2_4_to_8(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1533
1534 if (png_get_valid(png_ptr, info_ptr,
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]1535 PNG_INFO_tRNS)) png_set_tRNS_to_alpha(png_ptr);
1536
1537These three functions are actually aliases for png_set_expand(), added
1538in libpng version 1.0.4, with the function names expanded to improve code
1539readability. In some future version they may actually do different
1540things.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1541
1542PNG can have files with 16 bits per channel. If you only can handle
15438 bits per channel, this will strip the pixels down to 8 bit.
1544
1545 if (bit_depth == 16)
1546 png_set_strip_16(png_ptr);
1547
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1548If, for some reason, you don't need the alpha channel on an image,
1549and you want to remove it rather than combining it with the background
1550(but the image author certainly had in mind that you *would* combine
1551it with the background, so that's what you should probably do):
1552
1553 if (color_type & PNG_COLOR_MASK_ALPHA)
1554 png_set_strip_alpha(png_ptr);
1555
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1556In PNG files, the alpha channel in an image
1557is the level of opacity. If you need the alpha channel in an image to
1558be the level of transparency instead of opacity, you can invert the
1559alpha channel (or the tRNS chunk data) after it's read, so that 0 is
1560fully opaque and 255 (in 8-bit or paletted images) or 65535 (in 16-bit
1561images) is fully transparent, with
1562
1563 png_set_invert_alpha(png_ptr);
1564
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1565PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
1566they can, resulting in, for example, 8 pixels per byte for 1 bit
1567files. This code expands to 1 pixel per byte without changing the
1568values of the pixels:
1569
1570 if (bit_depth < 8)
1571 png_set_packing(png_ptr);
1572
1573PNG files have possible bit depths of 1, 2, 4, 8, and 16. All pixels
1574stored in a PNG image have been "scaled" or "shifted" up to the next
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1575higher 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]15768 bits/sample in the range [0, 255]). However, it is also possible to
1577convert the PNG pixel data back to the original bit depth of the image.
1578This call reduces the pixels back down to the original bit depth:
1579
1580 png_color_16p sig_bit;
1581
1582 if (png_get_sBIT(png_ptr, info_ptr, &sig_bit))
1583 png_set_shift(png_ptr, sig_bit);
1584
1585PNG files store 3-color pixels in red, green, blue order. This code
1586changes the storage of the pixels to blue, green, red:
1587
1588 if (color_type == PNG_COLOR_TYPE_RGB ||
1589 color_type == PNG_COLOR_TYPE_RGB_ALPHA)
1590 png_set_bgr(png_ptr);
1591
1592PNG files store RGB pixels packed into 3 bytes. This code expands them
1593into 4 bytes for windowing systems that need them in this format:
1594
1595 if (bit_depth == 8 && color_type ==
1596 PNG_COLOR_TYPE_RGB) png_set_filler(png_ptr,
1597 filler, PNG_FILLER_BEFORE);
1598
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]1599where "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]1600either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether
1601you want the filler before the RGB or after. This transformation
1602does not affect images that already have full alpha channels.
1603
1604If you are reading an image with an alpha channel, and you need the
1605data as ARGB instead of the normal PNG format RGBA:
1606
1607 if (color_type == PNG_COLOR_TYPE_RGB_ALPHA)
1608 png_set_swap_alpha(png_ptr);
1609
1610For some uses, you may want a grayscale image to be represented as
1611RGB. This code will do that conversion:
1612
1613 if (color_type == PNG_COLOR_TYPE_GRAY ||
1614 color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
1615 png_set_gray_to_rgb(png_ptr);
1616
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1617Conversely, you can convert an RGB or RGBA image to grayscale or grayscale
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1618with alpha.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1619
1620 if (color_type == PNG_COLOR_TYPE_RGB ||
1621 color_type == PNG_COLOR_TYPE_RGB_ALPHA)
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1622 png_set_rgb_to_gray_fixed(png_ptr, error_action,
1623 int red_weight, int green_weight);
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1624
1625 error_action = 1: silently do the conversion
1626 error_action = 2: issue a warning if the original
1627 image has any pixel where
1628 red != green or red != blue
1629 error_action = 3: issue an error and abort the
1630 conversion if the original
1631 image has any pixel where
1632 red != green or red != blue
1633
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1634 red_weight: weight of red component times 100000
1635 green_weight: weight of green component times 100000
1636 If either weight is negative, default
1637 weights (21268, 71514) are used.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1638
1639If you have set error_action = 1 or 2, you can
1640later check whether the image really was gray, after processing
1641the image rows, with the png_get_rgb_to_gray_status(png_ptr) function.
1642It will return a png_byte that is zero if the image was gray or
16431 if there were any non-gray pixels. bKGD and sBIT data
1644will be silently converted to grayscale, using the green channel
1645data, regardless of the error_action setting.
1646
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1647With red_weight+green_weight<=100000,
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1648the normalized graylevel is computed:
1649
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1650 int rw = red_weight * 65536;
1651 int gw = green_weight * 65536;
1652 int bw = 65536 - (rw + gw);
1653 gray = (rw*red + gw*green + bw*blue)/65536;
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1654
1655The default values approximate those recommended in the Charles
1656Poynton's Color FAQ, <http://www.inforamp.net/~poynton/>
1657Copyright (c) 1998-01-04 Charles Poynton poynton@inforamp.net
1658
1659 Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
1660
1661Libpng approximates this with
1662
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1663 Y = 0.21268 * R + 0.7151 * G + 0.07217 * B
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1664
1665which can be expressed with integers as
1666
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1667 Y = (6969 * R + 23434 * G + 2365 * B)/32768
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1668
1669The calculation is done in a linear colorspace, if the image gamma
1670is known.
1671
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]1672If you have a grayscale and you are using png_set_expand_depth() or
1673png_set_expand() to change to
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]1674a higher bit-depth, you must either supply the background color as a gray
1675value at the original file bit-depth (need_expand = 1) or else supply the
1676background color as an RGB triplet at the final, expanded bit depth
1677(need_expand = 0). Similarly, if you are reading a paletted image, you
1678must either supply the background color as a palette index (need_expand = 1)
1679or 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]1680
1681 png_color_16 my_background;
1682 png_color_16p image_background;
1683
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]1684 if (png_get_bKGD(png_ptr, info_ptr, &image_background))
1685 png_set_background(png_ptr, image_background,
1686 PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1687 else
1688 png_set_background(png_ptr, &my_background,
1689 PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
1690
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]1691The png_set_background() function tells libpng to composite images
1692with alpha or simple transparency against the supplied background
1693color. If the PNG file contains a bKGD chunk (PNG_INFO_bKGD valid),
1694you may use this color, or supply another color more suitable for
1695the current display (e.g., the background color from a web page). You
1696need to tell libpng whether the color is in the gamma space of the
1697display (PNG_BACKGROUND_GAMMA_SCREEN for colors you supply), the file
1698(PNG_BACKGROUND_GAMMA_FILE for colors from the bKGD chunk), or one
1699that is neither of these gammas (PNG_BACKGROUND_GAMMA_UNIQUE - I don't
1700know why anyone would use this, but it's here).
1701
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1702To properly display PNG images on any kind of system, the application needs
1703to know what the display gamma is. Ideally, the user will know this, and
1704the application will allow them to set it. One method of allowing the user
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]1705to set the display gamma separately for each system is to check for a
1706SCREEN_GAMMA or DISPLAY_GAMMA environment variable, which will hopefully be
1707correctly set.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1708
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]1709Note that display_gamma is the overall gamma correction required to produce
1710pleasing results, which depends on the lighting conditions in the surrounding
1711environment. In a dim or brightly lit room, no compensation other than
1712the physical gamma exponent of the monitor is needed, while in a dark room
1713a slightly smaller exponent is better.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1714
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]1715 double gamma, screen_gamma;
1716
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1717 if (/* We have a user-defined screen
1718 gamma value */)
1719 {
1720 screen_gamma = user_defined_screen_gamma;
1721 }
1722 /* One way that applications can share the same
1723 screen gamma value */
1724 else if ((gamma_str = getenv("SCREEN_GAMMA"))
1725 != NULL)
1726 {
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]1727 screen_gamma = (double)atof(gamma_str);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1728 }
1729 /* If we don't have another value */
1730 else
1731 {
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1732 screen_gamma = 2.2; /* A good guess for a
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1733 PC monitor in a bright office or a dim room */
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1734 screen_gamma = 2.0; /* A good guess for a
1735 PC monitor in a dark room */
1736 screen_gamma = 1.7 or 1.0; /* A good
1737 guess for Mac systems */
1738 }
1739
1740The png_set_gamma() function handles gamma transformations of the data.
1741Pass both the file gamma and the current screen_gamma. If the file does
1742not 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]1743it 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]1744that file gammas are inverted from screen gammas. See the discussions
1745on gamma in the PNG specification for an excellent description of what
1746gamma is, and why all applications should support it. It is strongly
1747recommended that PNG viewers support gamma correction.
1748
1749 if (png_get_gAMA(png_ptr, info_ptr, &gamma))
1750 png_set_gamma(png_ptr, screen_gamma, gamma);
1751 else
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1752 png_set_gamma(png_ptr, screen_gamma, 0.45455);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1753
1754If you need to reduce an RGB file to a paletted file, or if a paletted
1755file has more entries then will fit on your screen, png_set_dither()
1756will do that. Note that this is a simple match dither that merely
1757finds the closest color available. This should work fairly well with
1758optimized palettes, and fairly badly with linear color cubes. If you
1759pass a palette that is larger then maximum_colors, the file will
1760reduce the number of colors in the palette so it will fit into
1761maximum_colors. If there is a histogram, it will use it to make
1762more intelligent choices when reducing the palette. If there is no
1763histogram, it may not do as good a job.
1764
1765 if (color_type & PNG_COLOR_MASK_COLOR)
1766 {
1767 if (png_get_valid(png_ptr, info_ptr,
1768 PNG_INFO_PLTE))
1769 {
Glenn Randers-Pehrsonf05f8032000-12-23 14:27:39 -0600[diff] [blame]1770 png_uint_16p histogram;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1771
1772 png_get_hIST(png_ptr, info_ptr,
1773 &histogram);
1774 png_set_dither(png_ptr, palette, num_palette,
1775 max_screen_colors, histogram, 1);
1776 }
1777 else
1778 {
1779 png_color std_color_cube[MAX_SCREEN_COLORS] =
1780 { ... colors ... };
1781
1782 png_set_dither(png_ptr, std_color_cube,
1783 MAX_SCREEN_COLORS, MAX_SCREEN_COLORS,
1784 NULL,0);
1785 }
1786 }
1787
1788PNG files describe monochrome as black being zero and white being one.
1789The following code will reverse this (make black be one and white be
1790zero):
1791
1792 if (bit_depth == 1 && color_type == PNG_COLOR_GRAY)
1793 png_set_invert_mono(png_ptr);
1794
1795PNG files store 16 bit pixels in network byte order (big-endian,
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1796ie. most significant bits first). This code changes the storage to the
1797other way (little-endian, i.e. least significant bits first, the
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1798way PCs store them):
1799
1800 if (bit_depth == 16)
1801 png_set_swap(png_ptr);
1802
1803If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you
1804need to change the order the pixels are packed into bytes, you can use:
1805
1806 if (bit_depth < 8)
1807 png_set_packswap(png_ptr);
1808
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1809Finally, you can write your own transformation function if none of
1810the existing ones meets your needs. This is done by setting a callback
1811with
1812
1813 png_set_read_user_transform_fn(png_ptr,
1814 read_transform_fn);
1815
1816You must supply the function
1817
1818 void read_transform_fn(png_ptr ptr, row_info_ptr
1819 row_info, png_bytep data)
1820
1821See pngtest.c for a working example. Your function will be called
1822after all of the other transformations have been processed.
1823
1824You can also set up a pointer to a user structure for use by your
1825callback function, and you can inform libpng that your transform
1826function will change the number of channels or bit depth with the
1827function
1828
1829 png_set_user_transform_info(png_ptr, user_ptr,
1830 user_depth, user_channels);
1831
1832The user's application, not libpng, is responsible for allocating and
1833freeing any memory required for the user structure.
1834
1835You can retrieve the pointer via the function
1836png_get_user_transform_ptr(). For example:
1837
1838 voidp read_user_transform_ptr =
1839 png_get_user_transform_ptr(png_ptr);
1840
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1841The last thing to handle is interlacing; this is covered in detail below,
1842but you must call the function here if you want libpng to handle expansion
1843of the interlaced image.
1844
1845 number_of_passes = png_set_interlace_handling(png_ptr);
1846
1847After setting the transformations, libpng can update your png_info
1848structure to reflect any transformations you've requested with this
1849call. This is most useful to update the info structure's rowbytes
1850field so you can use it to allocate your image memory. This function
1851will also update your palette with the correct screen_gamma and
1852background if these have been given with the calls above.
1853
1854 png_read_update_info(png_ptr, info_ptr);
1855
1856After you call png_read_update_info(), you can allocate any
1857memory you need to hold the image. The row data is simply
1858raw byte data for all forms of images. As the actual allocation
1859varies among applications, no example will be given. If you
1860are allocating one large chunk, you will need to build an
1861array of pointers to each row, as it will be needed for some
1862of the functions below.
1863
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1864.SS Reading image data
1865
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1866After you've allocated memory, you can read the image data.
1867The simplest way to do this is in one function call. If you are
1868allocating enough memory to hold the whole image, you can just
1869call png_read_image() and libpng will read in all the image data
1870and put it in the memory area supplied. You will need to pass in
1871an array of pointers to each row.
1872
1873This function automatically handles interlacing, so you don't need
1874to call png_set_interlace_handling() or call this function multiple
1875times, or any of that other stuff necessary with png_read_rows().
1876
1877 png_read_image(png_ptr, row_pointers);
1878
1879where row_pointers is:
1880
1881 png_bytep row_pointers[height];
1882
1883You can point to void or char or whatever you use for pixels.
1884
1885If you don't want to read in the whole image at once, you can
1886use png_read_rows() instead. If there is no interlacing (check
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1887interlace_type == PNG_INTERLACE_NONE), this is simple:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1888
1889 png_read_rows(png_ptr, row_pointers, NULL,
1890 number_of_rows);
1891
1892where row_pointers is the same as in the png_read_image() call.
1893
1894If 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]1895a single row_pointer instead of an array of row_pointers:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1896
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1897 png_bytep row_pointer = row;
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]1898 png_read_row(png_ptr, row_pointer, NULL);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1899
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1900If the file is interlaced (interlace_type != 0 in the IHDR chunk), things
1901get somewhat harder. The only current (PNG Specification version 1.2)
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1902interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1903is a somewhat complicated 2D interlace scheme, known as Adam7, that
1904breaks down an image into seven smaller images of varying size, based
1905on an 8x8 grid.
1906
1907libpng can fill out those images or it can give them to you "as is".
1908If you want them filled out, there are two ways to do that. The one
1909mentioned in the PNG specification is to expand each pixel to cover
1910those pixels that have not been read yet (the "rectangle" method).
1911This results in a blocky image for the first pass, which gradually
1912smooths out as more pixels are read. The other method is the "sparkle"
1913method, where pixels are drawn only in their final locations, with the
1914rest of the image remaining whatever colors they were initialized to
1915before the start of the read. The first method usually looks better,
1916but tends to be slower, as there are more pixels to put in the rows.
1917
1918If you don't want libpng to handle the interlacing details, just call
1919png_read_rows() seven times to read in all seven images. Each of the
1920images is a valid image by itself, or they can all be combined on an
19218x8 grid to form a single image (although if you intend to combine them
1922you would be far better off using the libpng interlace handling).
1923
1924The first pass will return an image 1/8 as wide as the entire image
1925(every 8th column starting in column 0) and 1/8 as high as the original
1926(every 8th row starting in row 0), the second will be 1/8 as wide
1927(starting in column 4) and 1/8 as high (also starting in row 0). The
1928third pass will be 1/4 as wide (every 4th pixel starting in column 0) and
19291/8 as high (every 8th row starting in row 4), and the fourth pass will
1930be 1/4 as wide and 1/4 as high (every 4th column starting in column 2,
1931and every 4th row starting in row 0). The fifth pass will return an
1932image 1/2 as wide, and 1/4 as high (starting at column 0 and row 2),
1933while the sixth pass will be 1/2 as wide and 1/2 as high as the original
1934(starting in column 1 and row 0). The seventh and final pass will be as
1935wide as the original, and 1/2 as high, containing all of the odd
1936numbered scanlines. Phew!
1937
1938If you want libpng to expand the images, call this before calling
1939png_start_read_image() or png_read_update_info():
1940
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1941 if (interlace_type == PNG_INTERLACE_ADAM7)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1942 number_of_passes
1943 = png_set_interlace_handling(png_ptr);
1944
1945This will return the number of passes needed. Currently, this
1946is seven, but may change if another interlace type is added.
1947This function can be called even if the file is not interlaced,
1948where it will return one pass.
1949
1950If you are not going to display the image after each pass, but are
1951going to wait until the entire image is read in, use the sparkle
1952effect. This effect is faster and the end result of either method
1953is exactly the same. If you are planning on displaying the image
1954after each pass, the "rectangle" effect is generally considered the
1955better looking one.
1956
1957If you only want the "sparkle" effect, just call png_read_rows() as
1958normal, with the third parameter NULL. Make sure you make pass over
1959the image number_of_passes times, and you don't change the data in the
1960rows between calls. You can change the locations of the data, just
1961not the data. Each pass only writes the pixels appropriate for that
1962pass, and assumes the data from previous passes is still valid.
1963
1964 png_read_rows(png_ptr, row_pointers, NULL,
1965 number_of_rows);
1966
1967If you only want the first effect (the rectangles), do the same as
1968before except pass the row buffer in the third parameter, and leave
1969the second parameter NULL.
1970
1971 png_read_rows(png_ptr, NULL, row_pointers,
1972 number_of_rows);
1973
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1974.SS Finishing a sequential read
1975
1976After you are finished reading the image through either the high- or
1977low-level interfaces, you can finish reading the file. If you are
1978interested in comments or time, which may be stored either before or
1979after the image data, you should pass the separate png_info struct if
1980you want to keep the comments from before and after the image
1981separate. If you are not interested, you can pass NULL.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1982
1983 png_read_end(png_ptr, end_info);
1984
1985When you are done, you can free all memory allocated by libpng like this:
1986
1987 png_destroy_read_struct(&png_ptr, &info_ptr,
1988 &end_info);
1989
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1990It is also possible to individually free the info_ptr members that
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]1991point to libpng-allocated storage with the following function:
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1992
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1993 png_free_data(png_ptr, info_ptr, mask, seq)
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]1994 mask - identifies data to be freed, a mask
1995 containing the logical OR of one or
1996 more of
1997 PNG_FREE_PLTE, PNG_FREE_TRNS,
1998 PNG_FREE_HIST, PNG_FREE_ICCP,
1999 PNG_FREE_PCAL, PNG_FREE_ROWS,
2000 PNG_FREE_SCAL, PNG_FREE_SPLT,
2001 PNG_FREE_TEXT, PNG_FREE_UNKN,
2002 or simply PNG_FREE_ALL
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2003 seq - sequence number of item to be freed
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2004 (-1 for all items)
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2005
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2006This function may be safely called when the relevant storage has
Glenn Randers-Pehrson68ea2432000-04-01 21:10:05 -0600[diff] [blame]2007already been freed, or has not yet been allocated, or was allocated
2008by the user and not by libpng, and will in those
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2009cases do nothing. The "seq" parameter is ignored if only one item
2010of the selected data type, such as PLTE, is allowed. If "seq" is not
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]2011-1, and multiple items are allowed for the data type identified in
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2012the mask, such as text or sPLT, only the n'th item in the structure
2013is freed, where n is "seq".
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2014
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2015The default behavior is only to free data that was allocated internally
2016by libpng. This can be changed, so that libpng will not free the data,
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2017or so that it will free data that was allocated by the user with png_malloc()
2018or png_zalloc() and passed in via a png_set_*() function, with
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2019
2020 png_data_freer(png_ptr, info_ptr, freer, mask)
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2021 mask - which data elements are affected
2022 same choices as in png_free_data()
2023 freer - one of
2024 PNG_DESTROY_WILL_FREE_DATA
2025 PNG_SET_WILL_FREE_DATA
2026 PNG_USER_WILL_FREE_DATA
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2027
2028This function only affects data that has already been allocated.
2029You can call this function after reading the PNG data but before calling
2030any png_set_*() functions, to control whether the user or the png_set_*()
2031function is responsible for freeing any existing data that might be present,
2032and again after the png_set_*() functions to control whether the user
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2033or png_destroy_*() is supposed to free the data. When the user assumes
2034responsibility for libpng-allocated data, the application must use
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2035png_free() to free it, and when the user transfers responsibility to libpng
2036for data that the user has allocated, the user must have used png_malloc()
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame^]2037or png_zalloc() to allocate it.
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2038
2039If you allocated your row_pointers in a single block, as suggested above in
2040the description of the high level read interface, you must not transfer
2041responsibility for freeing it to the png_set_rows or png_read_destroy function,
2042because they would also try to free the individual row_pointers[i].
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2043
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2044If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword
2045separately, do not transfer responsibility for freeing text_ptr to libpng,
2046because when libpng fills a png_text structure it combines these members with
2047the key member, and png_free_data() will free only text_ptr.key. Similarly,
2048if you transfer responsibility for free'ing text_ptr from libpng to your
2049application, your application must not separately free those members.
2050
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2051The png_free_data() function will turn off the "valid" flag for anything
2052it frees. If you need to turn the flag off for a chunk that was freed by your
2053application instead of by libpng, you can use
2054
2055 png_set_invalid(png_ptr, info_ptr, mask);
2056 mask - identifies the chunks to be made invalid,
2057 containing the logical OR of one or
Glenn Randers-Pehrsond56aca72000-11-23 11:51:42 -0600[diff] [blame]2058 more of
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2059 PNG_INFO_gAMA, PNG_INFO_sBIT,
2060 PNG_INFO_cHRM, PNG_INFO_PLTE,
2061 PNG_INFO_tRNS, PNG_INFO_bKGD,
2062 PNG_INFO_hIST, PNG_INFO_pHYs,
2063 PNG_INFO_oFFs, PNG_INFO_tIME,
2064 PNG_INFO_pCAL, PNG_INFO_sRGB,
2065 PNG_INFO_iCCP, PNG_INFO_sPLT,
2066 PNG_INFO_sCAL, PNG_INFO_IDAT
2067
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2068For a more compact example of reading a PNG image, see the file example.c.
2069
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2070.SS Reading PNG files progressively
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2071
2072The progressive reader is slightly different then the non-progressive
2073reader. Instead of calling png_read_info(), png_read_rows(), and
2074png_read_end(), you make one call to png_process_data(), which calls
2075callbacks when it has the info, a row, or the end of the image. You
2076set up these callbacks with png_set_progressive_read_fn(). You don't
2077have to worry about the input/output functions of libpng, as you are
2078giving the library the data directly in png_process_data(). I will
2079assume that you have read the section on reading PNG files above,
2080so I will only highlight the differences (although I will show
2081all of the code).
2082
2083png_structp png_ptr;
2084png_infop info_ptr;
2085
2086 /* An example code fragment of how you would
2087 initialize the progressive reader in your
2088 application. */
2089 int
2090 initialize_png_reader()
2091 {
2092 png_ptr = png_create_read_struct
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]2093 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2094 user_error_fn, user_warning_fn);
2095 if (!png_ptr)
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2096 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2097 info_ptr = png_create_info_struct(png_ptr);
2098 if (!info_ptr)
2099 {
2100 png_destroy_read_struct(&png_ptr, (png_infopp)NULL,
2101 (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2102 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2103 }
2104
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2105 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2106 {
2107 png_destroy_read_struct(&png_ptr, &info_ptr,
2108 (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2109 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2110 }
2111
2112 /* This one's new. You can provide functions
2113 to be called when the header info is valid,
2114 when each row is completed, and when the image
2115 is finished. If you aren't using all functions,
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2116 you can specify NULL parameters. Even when all
2117 three functions are NULL, you need to call
2118 png_set_progressive_read_fn(). You can use
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2119 any struct as the user_ptr (cast to a void pointer
2120 for the function call), and retrieve the pointer
2121 from inside the callbacks using the function
2122
2123 png_get_progressive_ptr(png_ptr);
2124
2125 which will return a void pointer, which you have
2126 to cast appropriately.
2127 */
2128 png_set_progressive_read_fn(png_ptr, (void *)user_ptr,
2129 info_callback, row_callback, end_callback);
2130
2131 return 0;
2132 }
2133
2134 /* A code fragment that you call as you receive blocks
2135 of data */
2136 int
2137 process_data(png_bytep buffer, png_uint_32 length)
2138 {
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2139 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2140 {
2141 png_destroy_read_struct(&png_ptr, &info_ptr,
2142 (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2143 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2144 }
2145
2146 /* This one's new also. Simply give it a chunk
2147 of data from the file stream (in order, of
2148 course). On machines with segmented memory
2149 models machines, don't give it any more than
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2150 64K. The library seems to run fine with sizes
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2151 of 4K. Although you can give it much less if
2152 necessary (I assume you can give it chunks of
2153 1 byte, I haven't tried less then 256 bytes
2154 yet). When this function returns, you may
2155 want to display any rows that were generated
2156 in the row callback if you don't already do
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2157 so there.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2158 */
2159 png_process_data(png_ptr, info_ptr, buffer, length);
2160 return 0;
2161 }
2162
2163 /* This function is called (as set by
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2164 png_set_progressive_read_fn() above) when enough data
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2165 has been supplied so all of the header has been
2166 read.
2167 */
2168 void
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2169 info_callback(png_structp png_ptr, png_infop info)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2170 {
2171 /* Do any setup here, including setting any of
2172 the transformations mentioned in the Reading
2173 PNG files section. For now, you _must_ call
2174 either png_start_read_image() or
2175 png_read_update_info() after all the
2176 transformations are set (even if you don't set
2177 any). You may start getting rows before
2178 png_process_data() returns, so this is your
2179 last chance to prepare for that.
2180 */
2181 }
2182
2183 /* This function is called when each row of image
2184 data is complete */
2185 void
2186 row_callback(png_structp png_ptr, png_bytep new_row,
Glenn Randers-Pehrsone68f5a32001-05-14 09:20:53 -0500[diff] [blame]2187 png_uint_32 row_num, int pass)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2188 {
2189 /* If the image is interlaced, and you turned
2190 on the interlace handler, this function will
2191 be called for every row in every pass. Some
2192 of these rows will not be changed from the
2193 previous pass. When the row is not changed,
2194 the new_row variable will be NULL. The rows
2195 and passes are called in order, so you don't
2196 really need the row_num and pass, but I'm
2197 supplying them because it may make your life
2198 easier.
2199
2200 For the non-NULL rows of interlaced images,
2201 you must call png_progressive_combine_row()
2202 passing in the row and the old row. You can
2203 call this function for NULL rows (it will just
2204 return) and for non-interlaced images (it just
2205 does the memcpy for you) if it will make the
2206 code easier. Thus, you can just do this for
2207 all cases:
2208 */
2209
2210 png_progressive_combine_row(png_ptr, old_row,
2211 new_row);
2212
2213 /* where old_row is what was displayed for
Glenn Randers-Pehrson345bc271998-06-14 14:43:31 -0500[diff] [blame]2214 previously for the row. Note that the first
2215 pass (pass == 0, really) will completely cover
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2216 the old row, so the rows do not have to be
2217 initialized. After the first pass (and only
2218 for interlaced images), you will have to pass
2219 the current row, and the function will combine
2220 the old row and the new row.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2221 */
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2222 }
2223
2224 void
2225 end_callback(png_structp png_ptr, png_infop info)
2226 {
2227 /* This function is called after the whole image
2228 has been read, including any chunks after the
2229 image (up to and including the IEND). You
2230 will usually have the same info chunk as you
2231 had in the header, although some data may have
2232 been added to the comments and time fields.
2233
2234 Most people won't do much here, perhaps setting
2235 a flag that marks the image as finished.
2236 */
2237 }
2238
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]2239
2240
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2241.SH IV. Writing
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2242
2243Much of this is very similar to reading. However, everything of
2244importance is repeated here, so you won't have to constantly look
2245back up in the reading section to understand writing.
2246
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2247.SS Setup
2248
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2249You will want to do the I/O initialization before you get into libpng,
2250so if it doesn't work, you don't have anything to undo. If you are not
2251using the standard I/O functions, you will need to replace them with
2252custom writing functions. See the discussion under Customizing libpng.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2253
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2254 FILE *fp = fopen(file_name, "wb");
2255 if (!fp)
2256 {
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2257 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2258 }
2259
2260Next, png_struct and png_info need to be allocated and initialized.
2261As these can be both relatively large, you may not want to store these
2262on the stack, unless you have stack space to spare. Of course, you
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2263will want to check if they return NULL. If you are also reading,
2264you won't want to name your read structure and your write structure
2265both "png_ptr"; you can call them anything you like, such as
2266"read_ptr" and "write_ptr". Look at pngtest.c, for example.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2267
2268 png_structp png_ptr = png_create_write_struct
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]2269 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2270 user_error_fn, user_warning_fn);
2271 if (!png_ptr)
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2272 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2273
2274 png_infop info_ptr = png_create_info_struct(png_ptr);
2275 if (!info_ptr)
2276 {
2277 png_destroy_write_struct(&png_ptr,
2278 (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2279 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2280 }
2281
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]2282If you want to use your own memory allocation routines,
2283define PNG_USER_MEM_SUPPORTED and use
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2284png_create_write_struct_2() instead of png_create_write_struct():
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]2285
2286 png_structp png_ptr = png_create_write_struct_2
2287 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
2288 user_error_fn, user_warning_fn, (png_voidp)
2289 user_mem_ptr, user_malloc_fn, user_free_fn);
2290
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2291After you have these structures, you will need to set up the
2292error handling. When libpng encounters an error, it expects to
2293longjmp() back to your routine. Therefore, you will need to call
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2294setjmp() and pass the png_jmpbuf(png_ptr). If you
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2295write the file from different routines, you will need to update
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2296the png_jmpbuf(png_ptr) every time you enter a new routine that will
2297call a png_*() function. See your documentation of setjmp/longjmp
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2298for your compiler for more information on setjmp/longjmp. See
2299the discussion on libpng error handling in the Customizing Libpng
2300section below for more information on the libpng error handling.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2301
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2302 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2303 {
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2304 png_destroy_write_struct(&png_ptr, &info_ptr);
2305 fclose(fp);
2306 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2307 }
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2308 ...
2309 return;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2310
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2311If you would rather avoid the complexity of setjmp/longjmp issues,
2312you can compile libpng with PNG_SETJMP_NOT_SUPPORTED, in which case
2313errors will result in a call to PNG_ABORT() which defaults to abort().
2314
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2315Now you need to set up the output code. The default for libpng is to
2316use the C function fwrite(). If you use this, you will need to pass a
2317valid FILE * in the function png_init_io(). Be sure that the file is
2318opened in binary mode. Again, if you wish to handle writing data in
2319another way, see the discussion on libpng I/O handling in the Customizing
2320Libpng section below.
2321
2322 png_init_io(png_ptr, fp);
2323
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2324.SS Write callbacks
2325
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2326At this point, you can set up a callback function that will be
2327called after each row has been written, which you can use to control
2328a progress meter or the like. It's demonstrated in pngtest.c.
2329You must supply a function
2330
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2331 void write_row_callback(png_ptr, png_uint_32 row,
2332 int pass);
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2333 {
2334 /* put your code here */
2335 }
2336
2337(You can give it another name that you like instead of "write_row_callback")
2338
2339To inform libpng about your function, use
2340
2341 png_set_write_status_fn(png_ptr, write_row_callback);
2342
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2343You now have the option of modifying how the compression library will
2344run. The following functions are mainly for testing, but may be useful
2345in some cases, like if you need to write PNG files extremely fast and
2346are willing to give up some compression, or if you want to get the
2347maximum possible compression at the expense of slower writing. If you
2348have no special needs in this area, let the library do what it wants by
2349not calling this function at all, as it has been tuned to deliver a good
2350speed/compression ratio. The second parameter to png_set_filter() is
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]2351the filter method, for which the only valid values are 0 (as of the
2352July 1999 PNG specification, version 1.2) or 64 (if you are writing
2353a PNG datastream that is to be embedded in a MNG datastream). The third
2354parameter is a flag that indicates which filter type(s) are to be tested
2355for each scanline. See the PNG specification for details on the specific filter
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]2356types.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2357
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2358
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2359 /* turn on or off filtering, and/or choose
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2360 specific filters. You can use either a single
2361 PNG_FILTER_VALUE_NAME or the logical OR of one
2362 or more PNG_FILTER_NAME masks. */
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2363 png_set_filter(png_ptr, 0,
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2364 PNG_FILTER_NONE | PNG_FILTER_VALUE_NONE |
2365 PNG_FILTER_SUB | PNG_FILTER_VALUE_SUB |
2366 PNG_FILTER_UP | PNG_FILTER_VALUE_UP |
2367 PNG_FILTER_AVE | PNG_FILTER_VALUE_AVE |
2368 PNG_FILTER_PAETH | PNG_FILTER_VALUE_PAETH|
2369 PNG_ALL_FILTERS);
2370
2371If an application
2372wants to start and stop using particular filters during compression,
2373it should start out with all of the filters (to ensure that the previous
2374row of pixels will be stored in case it's needed later), and then add
2375and remove them after the start of compression.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2376
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]2377If you are writing a PNG datastream that is to be embedded in a MNG
2378datastream, the second parameter can be either 0 or 64.
2379
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]2380The png_set_compression_*() functions interface to the zlib compression
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2381library, and should mostly be ignored unless you really know what you are
2382doing. The only generally useful call is png_set_compression_level()
2383which changes how much time zlib spends on trying to compress the image
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2384data. See the Compression Library (zlib.h and algorithm.txt, distributed
2385with zlib) for details on the compression levels.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2386
2387 /* set the zlib compression level */
2388 png_set_compression_level(png_ptr,
2389 Z_BEST_COMPRESSION);
2390
2391 /* set other zlib parameters */
2392 png_set_compression_mem_level(png_ptr, 8);
2393 png_set_compression_strategy(png_ptr,
2394 Z_DEFAULT_STRATEGY);
2395 png_set_compression_window_bits(png_ptr, 15);
2396 png_set_compression_method(png_ptr, 8);
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2397 png_set_compression_buffer_size(png_ptr, 8192)
2398
2399extern PNG_EXPORT(void,png_set_zbuf_size)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2400
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2401.SS Setting the contents of info for output
2402
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2403You now need to fill in the png_info structure with all the data you
2404wish to write before the actual image. Note that the only thing you
2405are allowed to write after the image is the text chunks and the time
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]2406chunk (as of PNG Specification 1.2, anyway). See png_write_end() and
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2407the latest PNG specification for more information on that. If you
2408wish to write them before the image, fill them in now, and flag that
2409data as being valid. If you want to wait until after the data, don't
2410fill them until png_write_end(). For all the fields in png_info and
2411their data types, see png.h. For explanations of what the fields
2412contain, see the PNG specification.
2413
2414Some of the more important parts of the png_info are:
2415
2416 png_set_IHDR(png_ptr, info_ptr, width, height,
2417 bit_depth, color_type, interlace_type,
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]2418 compression_type, filter_method)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2419 width - holds the width of the image
2420 in pixels (up to 2^31).
2421 height - holds the height of the image
2422 in pixels (up to 2^31).
2423 bit_depth - holds the bit depth of one of the
2424 image channels.
2425 (valid values are 1, 2, 4, 8, 16
2426 and depend also on the
2427 color_type. See also significant
2428 bits (sBIT) below).
2429 color_type - describes which color/alpha
2430 channels are present.
2431 PNG_COLOR_TYPE_GRAY
2432 (bit depths 1, 2, 4, 8, 16)
2433 PNG_COLOR_TYPE_GRAY_ALPHA
2434 (bit depths 8, 16)
2435 PNG_COLOR_TYPE_PALETTE
2436 (bit depths 1, 2, 4, 8)
2437 PNG_COLOR_TYPE_RGB
2438 (bit_depths 8, 16)
2439 PNG_COLOR_TYPE_RGB_ALPHA
2440 (bit_depths 8, 16)
2441
2442 PNG_COLOR_MASK_PALETTE
2443 PNG_COLOR_MASK_COLOR
2444 PNG_COLOR_MASK_ALPHA
2445
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2446 interlace_type - PNG_INTERLACE_NONE or
2447 PNG_INTERLACE_ADAM7
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2448 compression_type - (must be
2449 PNG_COMPRESSION_TYPE_DEFAULT)
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]2450 filter_method - (must be PNG_FILTER_TYPE_DEFAULT
2451 or, if you are writing a PNG to
2452 be embedded in a MNG datastream,
2453 can also be
2454 PNG_INTRAPIXEL_DIFFERENCING)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2455
2456 png_set_PLTE(png_ptr, info_ptr, palette,
2457 num_palette);
2458 palette - the palette for the file
2459 (array of png_color)
2460 num_palette - number of entries in the palette
2461
2462 png_set_gAMA(png_ptr, info_ptr, gamma);
2463 gamma - the gamma the image was created
2464 at (PNG_INFO_gAMA)
2465
2466 png_set_sRGB(png_ptr, info_ptr, srgb_intent);
2467 srgb_intent - the rendering intent
2468 (PNG_INFO_sRGB) The presence of
2469 the sRGB chunk means that the pixel
2470 data is in the sRGB color space.
2471 This chunk also implies specific
2472 values of gAMA and cHRM. Rendering
2473 intent is the CSS-1 property that
2474 has been defined by the International
2475 Color Consortium
2476 (http://www.color.org).
2477 It can be one of
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]2478 PNG_sRGB_INTENT_SATURATION,
2479 PNG_sRGB_INTENT_PERCEPTUAL,
2480 PNG_sRGB_INTENT_ABSOLUTE, or
2481 PNG_sRGB_INTENT_RELATIVE.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2482
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2483
2484 png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr,
2485 srgb_intent);
2486 srgb_intent - the rendering intent
2487 (PNG_INFO_sRGB) The presence of the
2488 sRGB chunk means that the pixel
2489 data is in the sRGB color space.
2490 This function also causes gAMA and
2491 cHRM chunks with the specific values
2492 that are consistent with sRGB to be
2493 written.
2494
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2495 png_set_iCCP(png_ptr, info_ptr, name, compression_type,
2496 profile, proflen);
2497 name - The profile name.
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2498 compression - The compression type; always
2499 PNG_COMPRESSION_TYPE_BASE for PNG 1.0.
2500 You may give NULL to this argument to
2501 ignore it.
2502 profile - International Color Consortium color
2503 profile data. May contain NULs.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2504 proflen - length of profile data in bytes.
2505
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2506 png_set_sBIT(png_ptr, info_ptr, sig_bit);
2507 sig_bit - the number of significant bits for
2508 (PNG_INFO_sBIT) each of the gray, red,
2509 green, and blue channels, whichever are
2510 appropriate for the given color type
2511 (png_color_16)
2512
2513 png_set_tRNS(png_ptr, info_ptr, trans, num_trans,
2514 trans_values);
2515 trans - array of transparent entries for
2516 palette (PNG_INFO_tRNS)
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]2517 trans_values - graylevel or color sample values of
2518 the single transparent color for
2519 non-paletted images (PNG_INFO_tRNS)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2520 num_trans - number of transparent entries
2521 (PNG_INFO_tRNS)
2522
2523 png_set_hIST(png_ptr, info_ptr, hist);
2524 (PNG_INFO_hIST)
2525 hist - histogram of palette (array of
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2526 png_uint_16)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2527
2528 png_set_tIME(png_ptr, info_ptr, mod_time);
2529 mod_time - time image was last modified
2530 (PNG_VALID_tIME)
2531
2532 png_set_bKGD(png_ptr, info_ptr, background);
2533 background - background color (PNG_VALID_bKGD)
2534
2535 png_set_text(png_ptr, info_ptr, text_ptr, num_text);
2536 text_ptr - array of png_text holding image
2537 comments
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2538 text_ptr[i].compression - type of compression used
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2539 on "text" PNG_TEXT_COMPRESSION_NONE
2540 PNG_TEXT_COMPRESSION_zTXt
2541 PNG_ITXT_COMPRESSION_NONE
2542 PNG_ITXT_COMPRESSION_zTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2543 text_ptr[i].key - keyword for comment. Must contain
2544 1-79 characters.
2545 text_ptr[i].text - text comments for current
2546 keyword. Can be NULL or empty.
2547 text_ptr[i].text_length - length of text string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2548 after decompression, 0 for iTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2549 text_ptr[i].itxt_length - length of itxt string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2550 after decompression, 0 for tEXt/zTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2551 text_ptr[i].lang - language of comment (NULL or
2552 empty for unknown).
2553 text_ptr[i].translated_keyword - keyword in UTF-8 (NULL
2554 or empty for unknown).
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2555 num_text - number of comments
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2556
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2557 png_set_sPLT(png_ptr, info_ptr, &palette_ptr,
2558 num_spalettes);
2559 palette_ptr - array of png_sPLT_struct structures
2560 to be added to the list of palettes
2561 in the info structure.
2562 num_spalettes - number of palette structures to be
2563 added.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2564
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2565 png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y,
2566 unit_type);
2567 offset_x - positive offset from the left
2568 edge of the screen
2569 offset_y - positive offset from the top
2570 edge of the screen
2571 unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
2572
2573 png_set_pHYs(png_ptr, info_ptr, res_x, res_y,
2574 unit_type);
2575 res_x - pixels/unit physical resolution
2576 in x direction
2577 res_y - pixels/unit physical resolution
2578 in y direction
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2579 unit_type - PNG_RESOLUTION_UNKNOWN,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2580 PNG_RESOLUTION_METER
2581
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2582 png_set_sCAL(png_ptr, info_ptr, unit, width, height)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2583 unit - physical scale units (an integer)
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2584 width - width of a pixel in physical scale units
2585 height - height of a pixel in physical scale units
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2586 (width and height are doubles)
2587
2588 png_set_sCAL_s(png_ptr, info_ptr, unit, width, height)
2589 unit - physical scale units (an integer)
2590 width - width of a pixel in physical scale units
2591 height - height of a pixel in physical scale units
2592 (width and height are strings like "2.54")
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2593
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2594 png_set_unknown_chunks(png_ptr, info_ptr, &unknowns,
2595 num_unknowns)
2596 unknowns - array of png_unknown_chunk
2597 structures holding unknown chunks
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2598 unknowns[i].name - name of unknown chunk
2599 unknowns[i].data - data of unknown chunk
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2600 unknowns[i].size - size of unknown chunk's data
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2601 unknowns[i].location - position to write chunk in file
2602 0: do not write chunk
2603 PNG_HAVE_IHDR: before PLTE
2604 PNG_HAVE_PLTE: before IDAT
2605 PNG_AFTER_IDAT: after IDAT
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2606
2607The "location" member is set automatically according to
2608what part of the output file has already been written.
2609You can change its value after calling png_set_unknown_chunks()
2610as demonstrated in pngtest.c. Within each of the "locations",
2611the chunks are sequenced according to their position in the
2612structure (that is, the value of "i", which is the order in which
2613the chunk was either read from the input file or defined with
2614png_set_unknown_chunks).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2615
2616A quick word about text and num_text. text is an array of png_text
2617structures. num_text is the number of valid structures in the array.
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2618Each png_text structure holds a language code, a keyword, a text value,
2619and a compression type.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2620
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2621The compression types have the same valid numbers as the compression
2622types of the image data. Currently, the only valid number is zero.
2623However, you can store text either compressed or uncompressed, unlike
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2624images, which always have to be compressed. So if you don't want the
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2625text compressed, set the compression type to PNG_TEXT_COMPRESSION_NONE.
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2626Because tEXt and zTXt chunks don't have a language field, if you
2627specify PNG_TEXT_COMPRESSION_NONE or PNG_TEXT_COMPRESSION_zTXt
2628any language code or translated keyword will not be written out.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2629
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2630Until text gets around 1000 bytes, it is not worth compressing it.
2631After the text has been written out to the file, the compression type
2632is set to PNG_TEXT_COMPRESSION_NONE_WR or PNG_TEXT_COMPRESSION_zTXt_WR,
2633so that it isn't written out again at the end (in case you are calling
2634png_write_end() with the same struct.
2635
2636The keywords that are given in the PNG Specification are:
2637
2638 Title Short (one line) title or
2639 caption for image
2640 Author Name of image's creator
2641 Description Description of image (possibly long)
2642 Copyright Copyright notice
2643 Creation Time Time of original image creation
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2644 (usually RFC 1123 format, see below)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2645 Software Software used to create the image
2646 Disclaimer Legal disclaimer
2647 Warning Warning of nature of content
2648 Source Device used to create the image
2649 Comment Miscellaneous comment; conversion
2650 from other image format
2651
2652The keyword-text pairs work like this. Keywords should be short
2653simple descriptions of what the comment is about. Some typical
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2654keywords are found in the PNG specification, as is some recommendations
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2655on keywords. You can repeat keywords in a file. You can even write
2656some text before the image and some after. For example, you may want
2657to put a description of the image before the image, but leave the
2658disclaimer until after, so viewers working over modem connections
2659don't have to wait for the disclaimer to go over the modem before
2660they start seeing the image. Finally, keywords should be full
2661words, not abbreviations. Keywords and text are in the ISO 8859-1
2662(Latin-1) character set (a superset of regular ASCII) and can not
2663contain NUL characters, and should not contain control or other
2664unprintable characters. To make the comments widely readable, stick
2665with basic ASCII, and avoid machine specific character set extensions
2666like the IBM-PC character set. The keyword must be present, but
2667you can leave off the text string on non-compressed pairs.
2668Compressed pairs must have a text string, as only the text string
2669is compressed anyway, so the compression would be meaningless.
2670
2671PNG supports modification time via the png_time structure. Two
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2672conversion routines are provided, png_convert_from_time_t() for
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2673time_t and png_convert_from_struct_tm() for struct tm. The
2674time_t routine uses gmtime(). You don't have to use either of
2675these, but if you wish to fill in the png_time structure directly,
2676you should provide the time in universal time (GMT) if possible
2677instead of your local time. Note that the year number is the full
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2678year (e.g. 1998, rather than 98 - PNG is year 2000 compliant!), and
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2679that months start with 1.
2680
2681If you want to store the time of the original image creation, you should
2682use a plain tEXt chunk with the "Creation Time" keyword. This is
2683necessary because the "creation time" of a PNG image is somewhat vague,
2684depending on whether you mean the PNG file, the time the image was
2685created in a non-PNG format, a still photo from which the image was
2686scanned, or possibly the subject matter itself. In order to facilitate
2687machine-readable dates, it is recommended that the "Creation Time"
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2688tEXt 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]2689although this isn't a requirement. Unlike the tIME chunk, the
2690"Creation Time" tEXt chunk is not expected to be automatically changed
2691by the software. To facilitate the use of RFC 1123 dates, a function
2692png_convert_to_rfc1123(png_timep) is provided to convert from PNG
2693time to an RFC 1123 format string.
2694
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2695.SS Writing unknown chunks
2696
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2697You can use the png_set_unknown_chunks function to queue up chunks
2698for writing. You give it a chunk name, raw data, and a size; that's
2699all there is to it. The chunks will be written by the next following
2700png_write_info_before_PLTE, png_write_info, or png_write_end function.
2701Any chunks previously read into the info structure's unknown-chunk
2702list will also be written out in a sequence that satisfies the PNG
2703specification's ordering rules.
2704
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2705.SS The high-level write interface
2706
2707At this point there are two ways to proceed; through the high-level
2708write interface, or through a sequence of low-level write operations.
2709You can use the high-level interface if your image data is present
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2710in the info structure. All defined output
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]2711transformations are permitted, enabled by the following masks.
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2712
2713 PNG_TRANSFORM_IDENTITY No transformation
2714 PNG_TRANSFORM_PACKING Pack 1, 2 and 4-bit samples
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2715 PNG_TRANSFORM_PACKSWAP Change order of packed
2716 pixels to LSB first
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2717 PNG_TRANSFORM_INVERT_MONO Invert monochrome images
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2718 PNG_TRANSFORM_SHIFT Normalize pixels to the
2719 sBIT depth
2720 PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA
2721 to BGRA
2722 PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA
2723 to AG
2724 PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity
2725 to transparency
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2726 PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples
2727 PNG_TRANSFORM_STRIP_FILLER Strip out filler bytes.
2728
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2729If you have valid image data in the info structure (you can use
2730png_set_rows() to put image data in the info structure), simply do this:
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2731
2732 png_write_png(png_ptr, info_ptr, png_transforms, NULL)
2733
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2734where png_transforms is an integer containing the logical OR of some set of
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2735transformation flags. This call is equivalent to png_write_info(),
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2736followed the set of transformations indicated by the transform mask,
2737then png_write_image(), and finally png_write_end().
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2738
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2739(The final parameter of this call is not yet used. Someday it might point
2740to transformation parameters required by some future output transform.)
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2741
2742.SS The low-level write interface
2743
2744If you are going the low-level route instead, you are now ready to
2745write all the file information up to the actual image data. You do
2746this with a call to png_write_info().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2747
2748 png_write_info(png_ptr, info_ptr);
2749
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2750Note that there is one transformation you may need to do before
2751png_write_info(). In PNG files, the alpha channel in an image is the
2752level of opacity. If your data is supplied as a level of
2753transparency, you can invert the alpha channel before you write it, so
2754that 0 is fully transparent and 255 (in 8-bit or paletted images) or
275565535 (in 16-bit images) is fully opaque, with
2756
2757 png_set_invert_alpha(png_ptr);
2758
2759This must appear before png_write_info() instead of later with the
2760other transformations because in the case of paletted images the tRNS
2761chunk data has to be inverted before the tRNS chunk is written. If
2762your image is not a paletted image, the tRNS data (which in such cases
2763represents a single color to be rendered as transparent) won't need to
2764be changed, and you can safely do this transformation after your
2765png_write_info() call.
2766
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]2767If you need to write a private chunk that you want to appear before
2768the PLTE chunk when PLTE is present, you can write the PNG info in
2769two steps, and insert code to write your own chunk between them:
2770
2771 png_write_info_before_PLTE(png_ptr, info_ptr);
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2772 png_set_unknown_chunks(png_ptr, info_ptr, ...);
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]2773 png_write_info(png_ptr, info_ptr);
2774
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2775After you've written the file information, you can set up the library
2776to handle any special transformations of the image data. The various
2777ways to transform the data will be described in the order that they
2778should occur. This is important, as some of these change the color
2779type and/or bit depth of the data, and some others only work on
2780certain color types and bit depths. Even though each transformation
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2781checks 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]2782make sure to only enable a transformation if it will be valid for the
2783data. For example, don't swap red and blue on grayscale data.
2784
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]2785PNG files store RGB pixels packed into 3 or 6 bytes. This code tells
Glenn Randers-Pehrson68ea2432000-04-01 21:10:05 -0600[diff] [blame]2786the 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]2787to 3 or 6 bytes (or strip 2 or 4-byte grayscale+filler data to 1 or 2
2788bytes per pixel).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2789
2790 png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
2791
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2792where the 0 is unused, and the location is either PNG_FILLER_BEFORE or
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2793PNG_FILLER_AFTER, depending upon whether the filler byte in the pixel
2794is stored XRGB or RGBX.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2795
2796PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
2797they can, resulting in, for example, 8 pixels per byte for 1 bit files.
2798If the data is supplied at 1 pixel per byte, use this code, which will
2799correctly pack the pixels into a single byte:
2800
2801 png_set_packing(png_ptr);
2802
2803PNG files reduce possible bit depths to 1, 2, 4, 8, and 16. If your
2804data is of another bit depth, you can write an sBIT chunk into the
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2805file so that decoders can recover the original data if desired.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2806
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2807 /* Set the true bit depth of the image data */
2808 if (color_type & PNG_COLOR_MASK_COLOR)
2809 {
2810 sig_bit.red = true_bit_depth;
2811 sig_bit.green = true_bit_depth;
2812 sig_bit.blue = true_bit_depth;
2813 }
2814 else
2815 {
2816 sig_bit.gray = true_bit_depth;
2817 }
2818 if (color_type & PNG_COLOR_MASK_ALPHA)
2819 {
2820 sig_bit.alpha = true_bit_depth;
2821 }
2822
2823 png_set_sBIT(png_ptr, info_ptr, &sig_bit);
2824
2825If 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]2826one 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]2827this will scale the values to appear to be the correct bit depth as
2828is required by PNG.
2829
2830 png_set_shift(png_ptr, &sig_bit);
2831
2832PNG files store 16 bit pixels in network byte order (big-endian,
2833ie. most significant bits first). This code would be used if they are
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2834supplied the other way (little-endian, i.e. least significant bits
2835first, the way PCs store them):
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2836
2837 if (bit_depth > 8)
2838 png_set_swap(png_ptr);
2839
2840If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you
2841need to change the order the pixels are packed into bytes, you can use:
2842
2843 if (bit_depth < 8)
2844 png_set_packswap(png_ptr);
2845
2846PNG files store 3 color pixels in red, green, blue order. This code
2847would be used if they are supplied as blue, green, red:
2848
2849 png_set_bgr(png_ptr);
2850
2851PNG files describe monochrome as black being zero and white being
2852one. This code would be used if the pixels are supplied with this reversed
2853(black being one and white being zero):
2854
2855 png_set_invert_mono(png_ptr);
2856
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2857Finally, you can write your own transformation function if none of
2858the existing ones meets your needs. This is done by setting a callback
2859with
2860
2861 png_set_write_user_transform_fn(png_ptr,
2862 write_transform_fn);
2863
2864You must supply the function
2865
2866 void write_transform_fn(png_ptr ptr, row_info_ptr
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2867 row_info, png_bytep data)
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2868
2869See pngtest.c for a working example. Your function will be called
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]2870before any of the other transformations are processed.
2871
2872You can also set up a pointer to a user structure for use by your
2873callback function.
2874
2875 png_set_user_transform_info(png_ptr, user_ptr, 0, 0);
2876
2877The user_channels and user_depth parameters of this function are ignored
2878when writing; you can set them to zero as shown.
2879
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2880You can retrieve the pointer via the function png_get_user_transform_ptr().
2881For example:
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]2882
2883 voidp write_user_transform_ptr =
2884 png_get_user_transform_ptr(png_ptr);
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2885
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2886It is possible to have libpng flush any pending output, either manually,
2887or automatically after a certain number of lines have been written. To
2888flush the output stream a single time call:
2889
2890 png_write_flush(png_ptr);
2891
2892and to have libpng flush the output stream periodically after a certain
2893number of scanlines have been written, call:
2894
2895 png_set_flush(png_ptr, nrows);
2896
2897Note that the distance between rows is from the last time png_write_flush()
2898was called, or the first row of the image if it has never been called.
2899So if you write 50 lines, and then png_set_flush 25, it will flush the
2900output on the next scanline, and every 25 lines thereafter, unless
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2901png_write_flush() is called before 25 more lines have been written.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2902If 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]2903RGB image) the image compression may decrease noticeably (although this
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2904may be acceptable for real-time applications). Infrequent flushing will
2905only degrade the compression performance by a few percent over images
2906that do not use flushing.
2907
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2908.SS Writing the image data
2909
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2910That's it for the transformations. Now you can write the image data.
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2911The 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]2912whole image in memory, you can just call png_write_image() and libpng
2913will write the image. You will need to pass in an array of pointers to
2914each row. This function automatically handles interlacing, so you don't
2915need to call png_set_interlace_handling() or call this function multiple
2916times, or any of that other stuff necessary with png_write_rows().
2917
2918 png_write_image(png_ptr, row_pointers);
2919
2920where row_pointers is:
2921
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]2922 png_byte *row_pointers[height];
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2923
2924You can point to void or char or whatever you use for pixels.
2925
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]2926If you don't want to write the whole image at once, you can
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2927use png_write_rows() instead. If the file is not interlaced,
2928this is simple:
2929
2930 png_write_rows(png_ptr, row_pointers,
2931 number_of_rows);
2932
2933row_pointers is the same as in the png_write_image() call.
2934
2935If 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]2936a single row_pointer instead of an array of row_pointers:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2937
2938 png_bytep row_pointer = row;
2939
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2940 png_write_row(png_ptr, row_pointer);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2941
2942When the file is interlaced, things can get a good deal more
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2943complicated. The only currently (as of the PNG Specification
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]2944version 1.2, dated July 1999) defined interlacing scheme for PNG files
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2945is the "Adam7" interlace scheme, that breaks down an
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2946image into seven smaller images of varying size. libpng will build
2947these images for you, or you can do them yourself. If you want to
2948build them yourself, see the PNG specification for details of which
2949pixels to write when.
2950
2951If you don't want libpng to handle the interlacing details, just
2952use png_set_interlace_handling() and call png_write_rows() the
2953correct number of times to write all seven sub-images.
2954
2955If you want libpng to build the sub-images, call this before you start
2956writing any rows:
2957
2958 number_of_passes =
2959 png_set_interlace_handling(png_ptr);
2960
2961This will return the number of passes needed. Currently, this
2962is seven, but may change if another interlace type is added.
2963
2964Then write the complete image number_of_passes times.
2965
2966 png_write_rows(png_ptr, row_pointers,
2967 number_of_rows);
2968
2969As some of these rows are not used, and thus return immediately,
2970you may want to read about interlacing in the PNG specification,
2971and only update the rows that are actually used.
2972
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2973.SS Finishing a sequential write
2974
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2975After you are finished writing the image, you should finish writing
2976the file. If you are interested in writing comments or time, you should
2977pass an appropriately filled png_info pointer. If you are not interested,
2978you can pass NULL.
2979
2980 png_write_end(png_ptr, info_ptr);
2981
2982When you are done, you can free all memory used by libpng like this:
2983
2984 png_destroy_write_struct(&png_ptr, &info_ptr);
2985
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2986It is also possible to individually free the info_ptr members that
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2987point to libpng-allocated storage with the following function:
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2988
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2989 png_free_data(png_ptr, info_ptr, mask, seq)
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2990 mask - identifies data to be freed, a mask
2991 containing the logical OR of one or
2992 more of
2993 PNG_FREE_PLTE, PNG_FREE_TRNS,
2994 PNG_FREE_HIST, PNG_FREE_ICCP,
2995 PNG_FREE_PCAL, PNG_FREE_ROWS,
2996 PNG_FREE_SCAL, PNG_FREE_SPLT,
2997 PNG_FREE_TEXT, PNG_FREE_UNKN,
2998 or simply PNG_FREE_ALL
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2999 seq - sequence number of item to be freed
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3000 (-1 for all items)
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3001
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]3002This function may be safely called when the relevant storage has
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3003already been freed, or has not yet been allocated, or was allocated
3004by the user and not by libpng, and will in those
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3005cases do nothing. The "seq" parameter is ignored if only one item
3006of the selected data type, such as PLTE, is allowed. If "seq" is not
Glenn Randers-Pehrson68ea2432000-04-01 21:10:05 -0600[diff] [blame]3007-1, and multiple items are allowed for the data type identified in
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3008the mask, such as text or sPLT, only the n'th item in the structure
3009is freed, where n is "seq".
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3010
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3011If you allocated data such as a palette that you passed
3012in 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]3013png_destroy_write_struct().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3014
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3015The default behavior is only to free data that was allocated internally
3016by libpng. This can be changed, so that libpng will not free the data,
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3017or so that it will free data that was allocated by the user with png_malloc()
3018or png_zalloc() and passed in via a png_set_*() function, with
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3019
3020 png_data_freer(png_ptr, info_ptr, freer, mask)
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3021 mask - which data elements are affected
3022 same choices as in png_free_data()
3023 freer - one of
3024 PNG_DESTROY_WILL_FREE_DATA
3025 PNG_SET_WILL_FREE_DATA
3026 PNG_USER_WILL_FREE_DATA
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3027
3028For example, to transfer responsibility for some data from a read structure
3029to a write structure, you could use
3030
3031 png_data_freer(read_ptr, read_info_ptr,
3032 PNG_USER_WILL_FREE_DATA,
3033 PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST)
3034 png_data_freer(write_ptr, write_info_ptr,
3035 PNG_DESTROY_WILL_FREE_DATA,
3036 PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST)
3037
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3038thereby briefly reassigning responsibility for freeing to the user but
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3039immediately afterwards reassigning it once more to the write_destroy
3040function. Having done this, it would then be safe to destroy the read
3041structure and continue to use the PLTE, tRNS, and hIST data in the write
3042structure.
3043
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3044This function only affects data that has already been allocated.
3045You can call this function before calling after the png_set_*() functions
3046to control whether the user or png_destroy_*() is supposed to free the data.
3047When the user assumes responsibility for libpng-allocated data, the
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3048application must use
3049png_free() to free it, and when the user transfers responsibility to libpng
3050for data that the user has allocated, the user must have used png_malloc()
3051or png_zalloc() to allocate it.
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3052
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3053If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword
3054separately, do not transfer responsibility for freeing text_ptr to libpng,
3055because when libpng fills a png_text structure it combines these members with
3056the key member, and png_free_data() will free only text_ptr.key. Similarly,
3057if you transfer responsibility for free'ing text_ptr from libpng to your
3058application, your application must not separately free those members.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3059For a more compact example of writing a PNG image, see the file example.c.
3060
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3061.SH V. Modifying/Customizing libpng:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3062
Glenn Randers-Pehrson231e6872001-01-12 15:13:06 -0600[diff] [blame]3063There are three issues here. The first is changing how libpng does
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3064standard things like memory allocation, input/output, and error handling.
3065The second deals with more complicated things like adding new chunks,
3066adding new transformations, and generally changing how libpng works.
Glenn Randers-Pehrson231e6872001-01-12 15:13:06 -0600[diff] [blame]3067Both of those are compile-time issues; that is, they are generally
3068determined at the time the code is written, and there is rarely a need
3069to provide the user with a means of changing them. The third is a
3070run-time issue: choosing between and/or tuning one or more alternate
3071versions of computationally intensive routines; specifically, optimized
3072assembly-language (and therefore compiler- and platform-dependent)
3073versions.
3074
3075Memory allocation, input/output, and error handling
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3076
3077All of the memory allocation, input/output, and error handling in libpng
Glenn Randers-Pehrson231e6872001-01-12 15:13:06 -0600[diff] [blame]3078goes through callbacks that are user-settable. The default routines are
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3079in pngmem.c, pngrio.c, pngwio.c, and pngerror.c, respectively. To change
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]3080these functions, call the appropriate png_set_*_fn() function.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3081
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3082Memory allocation is done through the functions png_malloc(), png_zalloc(),
3083and png_free(). These currently just call the standard C functions. If
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3084your pointers can't access more then 64K at a time, you will want to set
3085MAXSEG_64K in zlib.h. Since it is unlikely that the method of handling
3086memory allocation on a platform will change between applications, these
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3087functions must be modified in the library at compile time. If you prefer
3088to use a different method of allocating and freeing data, you can use
3089
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3090 png_set_mem_fn(png_structp png_ptr, png_voidp mem_ptr,
3091 png_malloc_ptr malloc_fn, png_free_ptr free_fn)
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3092
3093This function also provides a void pointer that can be retrieved via
3094
3095 mem_ptr=png_get_mem_ptr(png_ptr);
3096
3097Your replacement memory functions must have prototypes as follows:
3098
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3099 png_voidp malloc_fn(png_structp png_ptr,
3100 png_uint_32 size);
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3101 void free_fn(png_structp png_ptr, png_voidp ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3102
Glenn Randers-Pehrson82ae3832001-04-20 10:32:10 -0500[diff] [blame]3103Your malloc_fn() can return NULL in case of failure. The png_malloc()
3104function will call png_error() if it receives a NULL from the system
3105memory allocator or from your replacement malloc_fn().
3106
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3107Input/Output in libpng is done through png_read() and png_write(),
3108which currently just call fread() and fwrite(). The FILE * is stored in
3109png_struct and is initialized via png_init_io(). If you wish to change
3110the method of I/O, the library supplies callbacks that you can set
3111through the function png_set_read_fn() and png_set_write_fn() at run
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3112time, instead of calling the png_init_io() function. These functions
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3113also provide a void pointer that can be retrieved via the function
3114png_get_io_ptr(). For example:
3115
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]3116 png_set_read_fn(png_structp read_ptr,
3117 voidp read_io_ptr, png_rw_ptr read_data_fn)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3118
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]3119 png_set_write_fn(png_structp write_ptr,
3120 voidp write_io_ptr, png_rw_ptr write_data_fn,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3121 png_flush_ptr output_flush_fn);
3122
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]3123 voidp read_io_ptr = png_get_io_ptr(read_ptr);
3124 voidp write_io_ptr = png_get_io_ptr(write_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3125
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3126The replacement I/O functions must have prototypes as follows:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3127
3128 void user_read_data(png_structp png_ptr,
3129 png_bytep data, png_uint_32 length);
3130 void user_write_data(png_structp png_ptr,
3131 png_bytep data, png_uint_32 length);
3132 void user_flush_data(png_structp png_ptr);
3133
3134Supplying NULL for the read, write, or flush functions sets them back
3135to using the default C stream functions. It is an error to read from
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3136a write stream, and vice versa.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3137
3138Error handling in libpng is done through png_error() and png_warning().
3139Errors handled through png_error() are fatal, meaning that png_error()
3140should never return to its caller. Currently, this is handled via
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3141setjmp() and longjmp() (unless you have compiled libpng with
3142PNG_SETJMP_NOT_SUPPORTED, in which case it is handled via PNG_ABORT()),
3143but you could change this to do things like exit() if you should wish.
3144
3145On non-fatal errors, png_warning() is called
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3146to print a warning message, and then control returns to the calling code.
3147By default png_error() and png_warning() print a message on stderr via
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3148fprintf() unless the library is compiled with PNG_NO_CONSOLE_IO defined
3149(because you don't want the messages) or PNG_NO_STDIO defined (because
3150fprintf() isn't available). If you wish to change the behavior of the error
3151functions, you will need to set up your own message callbacks. These
3152functions are normally supplied at the time that the png_struct is created.
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3153It is also possible to redirect errors and warnings to your own replacement
3154functions after png_create_*_struct() has been called by calling:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3155
3156 png_set_error_fn(png_structp png_ptr,
3157 png_voidp error_ptr, png_error_ptr error_fn,
3158 png_error_ptr warning_fn);
3159
3160 png_voidp error_ptr = png_get_error_ptr(png_ptr);
3161
3162If NULL is supplied for either error_fn or warning_fn, then the libpng
3163default function will be used, calling fprintf() and/or longjmp() if a
3164problem is encountered. The replacement error functions should have
3165parameters as follows:
3166
3167 void user_error_fn(png_structp png_ptr,
3168 png_const_charp error_msg);
3169 void user_warning_fn(png_structp png_ptr,
3170 png_const_charp warning_msg);
3171
3172The motivation behind using setjmp() and longjmp() is the C++ throw and
3173catch exception handling methods. This makes the code much easier to write,
3174as there is no need to check every return code of every function call.
3175However, there are some uncertainties about the status of local variables
3176after a longjmp, so the user may want to be careful about doing anything after
3177setjmp returns non-zero besides returning itself. Consult your compiler
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3178documentation for more details. For an alternative approach, you may wish
3179to use the "cexcept" facility (see http://cexcept.sourceforge.net).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3180
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3181.SS Custom chunks
3182
3183If you need to read or write custom chunks, you may need to get deeper
3184into the libpng code. The library now has mechanisms for storing
3185and writing chunks of unknown type; you can even declare callbacks
3186for custom chunks. Hoewver, this may not be good enough if the
3187library code itself needs to know about interactions between your
3188chunk and existing `intrinsic' chunks.
3189
3190If you need to write a new intrinsic chunk, first read the PNG
3191specification. Acquire a first level of
3192understanding of how it works. Pay particular attention to the
3193sections that describe chunk names, and look at how other chunks were
3194designed, so you can do things similarly. Second, check out the
3195sections of libpng that read and write chunks. Try to find a chunk
3196that is similar to yours and use it as a template. More details can
3197be found in the comments inside the code. It is best to handle unknown
3198chunks in a generic method, via callback functions, instead of by
3199modifying libpng functions.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3200
3201If you wish to write your own transformation for the data, look through
3202the part of the code that does the transformations, and check out some of
3203the simpler ones to get an idea of how they work. Try to find a similar
3204transformation to the one you want to add and copy off of it. More details
3205can be found in the comments inside the code itself.
3206
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3207.SS Configuring for 16 bit platforms
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3208
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3209You 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]3210it 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]3211won'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]3212
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3213.SS Configuring for DOS
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3214
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3215For DOS users who only have access to the lower 640K, you will
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3216have to limit zlib's memory usage via a png_set_compression_mem_level()
3217call. See zlib.h or zconf.h in the zlib library for more information.
3218
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3219.SS Configuring for Medium Model
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3220
3221Libpng's support for medium model has been tested on most of the popular
3222compilers. Make sure MAXSEG_64K gets defined, USE_FAR_KEYWORD gets
3223defined, and FAR gets defined to far in pngconf.h, and you should be
3224all set. Everything in the library (except for zlib's structure) is
3225expecting far data. You must use the typedefs with the p or pp on
3226the end for pointers (or at least look at them and be careful). Make
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3227note that the rows of data are defined as png_bytepp, which is an
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3228unsigned char far * far *.
3229
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3230.SS Configuring for gui/windowing platforms:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3231
3232You will need to write new error and warning functions that use the GUI
3233interface, as described previously, and set them to be the error and
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]3234warning functions at the time that png_create_*_struct() is called,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3235in order to have them available during the structure initialization.
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3236They can be changed later via png_set_error_fn(). On some compilers,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3237you may also have to change the memory allocators (png_malloc, etc.).
3238
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3239.SS Configuring for compiler xxx:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3240
3241All includes for libpng are in pngconf.h. If you need to add/change/delete
3242an include, this is the place to do it. The includes that are not
3243needed outside libpng are protected by the PNG_INTERNAL definition,
3244which is only defined for those routines inside libpng itself. The
3245files in libpng proper only include png.h, which includes pngconf.h.
3246
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3247.SS Configuring zlib:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3248
3249There are special functions to configure the compression. Perhaps the
3250most useful one changes the compression level, which currently uses
3251input compression values in the range 0 - 9. The library normally
3252uses the default compression level (Z_DEFAULT_COMPRESSION = 6). Tests
3253have shown that for a large majority of images, compression values in
3254the range 3-6 compress nearly as well as higher levels, and do so much
3255faster. For online applications it may be desirable to have maximum speed
3256(Z_BEST_SPEED = 1). With versions of zlib after v0.99, you can also
3257specify no compression (Z_NO_COMPRESSION = 0), but this would create
3258files larger than just storing the raw bitmap. You can specify the
3259compression level by calling:
3260
3261 png_set_compression_level(png_ptr, level);
3262
3263Another useful one is to reduce the memory level used by the library.
3264The memory level defaults to 8, but it can be lowered if you are
3265short on memory (running DOS, for example, where you only have 640K).
3266
3267 png_set_compression_mem_level(png_ptr, level);
3268
3269The other functions are for configuring zlib. They are not recommended
3270for normal use and may result in writing an invalid PNG file. See
3271zlib.h for more information on what these mean.
3272
3273 png_set_compression_strategy(png_ptr,
3274 strategy);
3275 png_set_compression_window_bits(png_ptr,
3276 window_bits);
3277 png_set_compression_method(png_ptr, method);
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3278 png_set_compression_buffer_size(png_ptr, size);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3279
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3280.SS Controlling row filtering
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3281
3282If you want to control whether libpng uses filtering or not, which
3283filters are used, and how it goes about picking row filters, you
3284can call one of these functions. The selection and configuration
3285of row filters can have a significant impact on the size and
3286encoding speed and a somewhat lesser impact on the decoding speed
3287of an image. Filtering is enabled by default for RGB and grayscale
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3288images (with and without alpha), but not for paletted images nor
3289for any images with bit depths less than 8 bits/pixel.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3290
3291The 'method' parameter sets the main filtering method, which is
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3292currently only '0' in the PNG 1.2 specification. The 'filters'
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3293parameter sets which filter(s), if any, should be used for each
3294scanline. Possible values are PNG_ALL_FILTERS and PNG_NO_FILTERS
3295to turn filtering on and off, respectively.
3296
3297Individual filter types are PNG_FILTER_NONE, PNG_FILTER_SUB,
3298PNG_FILTER_UP, PNG_FILTER_AVG, PNG_FILTER_PAETH, which can be bitwise
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3299ORed together with '|' to specify one or more filters to use.
3300These filters are described in more detail in the PNG specification. If
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3301you intend to change the filter type during the course of writing
3302the image, you should start with flags set for all of the filters
3303you intend to use so that libpng can initialize its internal
3304structures appropriately for all of the filter types.
3305
3306 filters = PNG_FILTER_NONE | PNG_FILTER_SUB
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3307 PNG_FILTER_UP | PNG_FILTER_AVE |
3308 PNG_FILTER_PAETH | PNG_ALL_FILTERS;
3309 or
3310 filters = one of PNG_FILTER_VALUE_NONE,
3311 PNG_FILTER_VALUE_SUB, PNG_FILTER_VALUE_UP,
3312 PNG_FILTER_VALUE_AVE, PNG_FILTER_VALUE_PAETH
3313
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3314 png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE,
3315 filters);
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3316 The second parameter can also be
3317 PNG_INTRAPIXEL_DIFFERENCING if you are
3318 writing a PNG to be embedded in a MNG
3319 datastream. This parameter must be the
3320 same as the value of filter_method used
3321 in png_set_IHDR().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3322
3323It is also possible to influence how libpng chooses from among the
3324available filters. This is done in two ways - by telling it how
3325important it is to keep the same filter for successive rows, and
3326by telling it the relative computational costs of the filters.
3327
3328 double weights[3] = {1.5, 1.3, 1.1},
3329 costs[PNG_FILTER_VALUE_LAST] =
3330 {1.0, 1.3, 1.3, 1.5, 1.7};
3331
3332 png_set_filter_selection(png_ptr,
3333 PNG_FILTER_SELECTION_WEIGHTED, 3,
3334 weights, costs);
3335
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3336The weights are multiplying factors that indicate to libpng that the
3337row filter should be the same for successive rows unless another row filter
3338is that many times better than the previous filter. In the above example,
3339if 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]3340"sum of absolute differences" 1.5 x 1.3 times higher than other filters
3341and still be chosen, while the NONE filter could have a sum 1.1 times
3342higher than other filters and still be chosen. Unspecified weights are
3343taken to be 1.0, and the specified weights should probably be declining
3344like those above in order to emphasize recent filters over older filters.
3345
3346The filter costs specify for each filter type a relative decoding cost
3347to be considered when selecting row filters. This means that filters
3348with higher costs are less likely to be chosen over filters with lower
3349costs, unless their "sum of absolute differences" is that much smaller.
3350The costs do not necessarily reflect the exact computational speeds of
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3351the various filters, since this would unduly influence the final image
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3352size.
3353
3354Note that the numbers above were invented purely for this example and
3355are given only to help explain the function usage. Little testing has
3356been done to find optimum values for either the costs or the weights.
3357
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3358.SS Removing unwanted object code
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3359
3360There are a bunch of #define's in pngconf.h that control what parts of
3361libpng are compiled. All the defines end in _SUPPORTED. If you are
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]3362never going to use a capability, you can change the #define to #undef
3363before recompiling libpng and save yourself code and data space, or
3364you can turn off individual capabilities with defines that begin with
3365PNG_NO_.
3366
3367You can also turn all of the transforms and ancillary chunk capabilities
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3368off en masse with compiler directives that define
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]3369PNG_NO_READ[or WRITE]_TRANSFORMS, or PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS,
3370or all four,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3371along with directives to turn on any of the capabilities that you do
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]3372want. The PNG_NO_READ[or WRITE]_TRANSFORMS directives disable
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3373the extra transformations but still leave the library fully capable of reading
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3374and writing PNG files with all known public chunks
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]3375Use of the PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS directive
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3376produces a library that is incapable of reading or writing ancillary chunks.
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3377If you are not using the progressive reading capability, you can
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]3378turn that off with PNG_NO_PROGRESSIVE_READ (don't confuse
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3379this with the INTERLACING capability, which you'll still have).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3380
3381All the reading and writing specific code are in separate files, so the
3382linker should only grab the files it needs. However, if you want to
3383make sure, or if you are building a stand alone library, all the
3384reading files start with pngr and all the writing files start with
3385pngw. The files that don't match either (like png.c, pngtrans.c, etc.)
3386are used for both reading and writing, and always need to be included.
3387The progressive reader is in pngpread.c
3388
3389If you are creating or distributing a dynamically linked library (a .so
3390or DLL file), you should not remove or disable any parts of the library,
3391as this will cause applications linked with different versions of the
3392library to fail if they call functions not available in your library.
3393The size of the library itself should not be an issue, because only
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3394those sections that are actually used will be loaded into memory.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3395
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3396.SS Requesting debug printout
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3397
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3398The macro definition PNG_DEBUG can be used to request debugging
3399printout. Set it to an integer value in the range 0 to 3. Higher
3400numbers result in increasing amounts of debugging information. The
3401information is printed to the "stderr" file, unless another file
3402name is specified in the PNG_DEBUG_FILE macro definition.
3403
3404When PNG_DEBUG > 0, the following functions (macros) become available:
3405
3406 png_debug(level, message)
3407 png_debug1(level, message, p1)
3408 png_debug2(level, message, p1, p2)
3409
3410in which "level" is compared to PNG_DEBUG to decide whether to print
3411the message, "message" is the formatted string to be printed,
3412and p1 and p2 are parameters that are to be embedded in the string
3413according to printf-style formatting directives. For example,
3414
3415 png_debug1(2, "foo=%d\n", foo);
3416
3417is expanded to
3418
3419 if(PNG_DEBUG > 2)
3420 fprintf(PNG_DEBUG_FILE, "foo=%d\n", foo);
3421
3422When PNG_DEBUG is defined but is zero, the macros aren't defined, but you
3423can still use PNG_DEBUG to control your own debugging:
3424
3425 #ifdef PNG_DEBUG
3426 fprintf(stderr, ...
3427 #endif
3428
3429When PNG_DEBUG = 1, the macros are defined, but only png_debug statements
3430having level = 0 will be printed. There aren't any such statements in
3431this version of libpng, but if you insert some they will be printed.
3432
Glenn Randers-Pehrson1fd5fb32001-05-06 05:34:26 -0500[diff] [blame]3433.SH VI. Runtime optimization
Glenn Randers-Pehrson231e6872001-01-12 15:13:06 -0600[diff] [blame]3434
Glenn Randers-Pehrson1fd5fb32001-05-06 05:34:26 -0500[diff] [blame]3435A new feature in libpng 1.2.0 is the ability to dynamically switch between
3436standard and optimized versions of some routines. Currently these are
3437limited to three computationally intensive tasks when reading PNG files:
3438decoding row filters, expanding interlacing, and combining interlaced or
3439transparent row data with previous row data. Currently the optimized
3440versions are available only for x86 (Intel, AMD, etc.) platforms with
3441MMX support, though this may change in future versions. (For example,
3442the non-MMX assembler optimizations for zlib might become similarly
3443runtime-selectable in future releases, in which case libpng could be
3444extended to support them. Alternatively, the compile-time choice of
3445floating-point versus integer routines for gamma correction might become
3446runtime-selectable.)
3447
3448Because such optimizations tend to be very platform- and compiler-dependent,
3449both in how they are written and in how they perform, the new runtime code
3450in libpng has been written to allow programs to query, enable, and disable
3451either specific optimizations or all such optimizations. For example, to
3452enable all possible optimizations (bearing in mind that some "optimizations"
3453may actually run more slowly in rare cases):
3454
3455 #if defined(PNG_LIBPNG_VER) && (PNG_LIBPNG_VER >= 10200)
3456 png_uint_32 mask, flags;
3457
3458 flags = png_get_asm_flags(png_ptr);
3459 mask = png_get_asm_flagmask(PNG_SELECT_READ | PNG_SELECT_WRITE);
3460 png_set_asm_flags(png_ptr, flags | mask);
3461 #endif
3462
3463To enable only optimizations relevant to reading PNGs, use PNG_SELECT_READ
3464by itself when calling png_get_asm_flagmask(); similarly for optimizing
3465only writing. To disable all optimizations:
3466
3467 #if defined(PNG_LIBPNG_VER) && (PNG_LIBPNG_VER >= 10200)
3468 flags = png_get_asm_flags(png_ptr);
3469 mask = png_get_asm_flagmask(PNG_SELECT_READ | PNG_SELECT_WRITE);
3470 png_set_asm_flags(png_ptr, flags & ~mask);
3471 #endif
3472
3473To enable or disable only MMX-related features, use png_get_mmx_flagmask()
3474in place of png_get_asm_flagmask(). The mmx version takes one additional
3475parameter:
3476
3477 #if defined(PNG_LIBPNG_VER) && (PNG_LIBPNG_VER >= 10200)
3478 int selection = PNG_SELECT_READ | PNG_SELECT_WRITE;
3479 int compilerID;
3480
3481 mask = png_get_mmx_flagmask(selection, &compilerID);
3482 #endif
3483
3484On return, compilerID will indicate which version of the MMX assembler
3485optimizations was compiled. Currently two flavors exist: Microsoft
3486Visual C++ (compilerID == 1) and GNU C (a.k.a. gcc/gas, compilerID == 2).
3487On non-x86 platforms or on systems compiled without MMX optimizations, a
3488value of -1 is used.
3489
3490Note that both png_get_asm_flagmask() and png_get_mmx_flagmask() return
3491all valid, settable optimization bits for the version of the library that's
3492currently in use. In the case of shared (dynamically linked) libraries,
3493this may include optimizations that did not exist at the time the code was
3494written and compiled. It is also possible, of course, to enable only known,
3495specific optimizations; for example:
3496
3497 #if defined(PNG_LIBPNG_VER) && (PNG_LIBPNG_VER >= 10200)
3498 flags = PNG_ASM_FLAG_MMX_READ_COMBINE_ROW \
3499 | PNG_ASM_FLAG_MMX_READ_INTERLACE \
3500 | PNG_ASM_FLAG_MMX_READ_FILTER_SUB \
3501 | PNG_ASM_FLAG_MMX_READ_FILTER_UP \
3502 | PNG_ASM_FLAG_MMX_READ_FILTER_AVG \
3503 | PNG_ASM_FLAG_MMX_READ_FILTER_PAETH ;
3504 png_set_asm_flags(png_ptr, flags);
3505 #endif
3506
3507This method would enable only the MMX read-optimizations available at the
3508time of libpng 1.2.0's release, regardless of whether a later version of
3509the DLL were actually being used. (Also note that these functions did not
3510exist in versions older than 1.2.0, so any attempt to run a dynamically
3511linked app on such an older version would fail.)
3512
3513To determine whether the processor supports MMX instructions at all, use
3514the png_mmx_support() function:
3515
3516 #if defined(PNG_LIBPNG_VER) && (PNG_LIBPNG_VER >= 10200)
3517 mmxsupport = png_mmx_support();
3518 #endif
3519
3520It returns -1 if MMX support is not compiled into libpng, 0 if MMX code
3521is compiled but MMX is not supported by the processor, or 1 if MMX support
3522is fully available. Note that png_mmx_support(), png_get_mmx_flagmask(),
3523and png_get_asm_flagmask() all may be called without allocating and ini-
3524tializing any PNG structures (for example, as part of a usage screen or
3525"about" box).
3526
3527For more extensive examples of runtime querying, enabling and disabling
3528of optimized features, see contrib/gregbook/readpng2.c in the libpng
3529source-code distribution.
3530
3531
3532.SH VII. MNG support
Glenn Randers-Pehrson2ad31ae2000-12-15 08:54:42 -0600[diff] [blame]3533
3534The MNG specification (available at http://www.libpng.org/pub/mng) allows
3535certain extensions to PNG for PNG images that are embedded in MNG datastreams.
3536Libpng can support some of these extensions. To enable them, use the
3537png_permit_mng_features() function:
3538
3539 feature_set = png_permit_mng_features(png_ptr, mask)
3540 mask is a png_uint_32 containing the logical OR of the
3541 features you want to enable. These include
3542 PNG_FLAG_MNG_EMPTY_PLTE
3543 PNG_FLAG_MNG_FILTER_64
3544 PNG_ALL_MNG_FEATURES
3545 feature_set is a png_32_uint that is the logical AND of
3546 your mask with the set of MNG features that is
3547 supported by the version of libpng that you are using.
3548
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]3549It is an error to use this function when reading or writing a standalone
3550PNG file with the PNG 8-byte signature. The PNG datastream must be wrapped
Glenn Randers-Pehrsonf05f8032000-12-23 14:27:39 -0600[diff] [blame]3551in a MNG datastream. As a minimum, it must have the MNG 8-byte signature
3552and the MHDR and MEND chunks. Libpng does not provide support for these
3553or any other MNG chunks; your application must provide its own support for
3554them. You may wish to consider using libmng (available at
3555http://www.libmng.com) instead.
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]3556
Glenn Randers-Pehrson1fd5fb32001-05-06 05:34:26 -0500[diff] [blame]3557.SH VIII. Changes to Libpng from version 0.88
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3558
3559It should be noted that versions of libpng later than 0.96 are not
3560distributed by the original libpng author, Guy Schalnat, nor by
3561Andreas Dilger, who had taken over from Guy during 1996 and 1997, and
3562distributed versions 0.89 through 0.96, but rather by another member
3563of the original PNG Group, Glenn Randers-Pehrson. Guy and Andreas are
3564still alive and well, but they have moved on to other things.
3565
3566The old libpng functions png_read_init(), png_write_init(),
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]3567png_info_init(), png_read_destroy(), and png_write_destroy() have been
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]3568moved to PNG_INTERNAL in version 0.95 to discourage their use. These
3569functions will be removed from libpng version 2.0.0.
3570
3571The preferred method of creating and initializing the libpng structures is
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3572via the png_create_read_struct(), png_create_write_struct(), and
3573png_create_info_struct() because they isolate the size of the structures
3574from the application, allow version error checking, and also allow the
3575use of custom error handling routines during the initialization, which
3576the old functions do not. The functions png_read_destroy() and
3577png_write_destroy() do not actually free the memory that libpng
3578allocated for these structs, but just reset the data structures, so they
3579can be used instead of png_destroy_read_struct() and
3580png_destroy_write_struct() if you feel there is too much system overhead
3581allocating and freeing the png_struct for each image read.
3582
3583Setting the error callbacks via png_set_message_fn() before
3584png_read_init() as was suggested in libpng-0.88 is no longer supported
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3585because this caused applications that do not use custom error functions
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3586to fail if the png_ptr was not initialized to zero. It is still possible
3587to set the error callbacks AFTER png_read_init(), or to change them with
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]3588png_set_error_fn(), which is essentially the same function, but with a new
3589name to force compilation errors with applications that try to use the old
3590method.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3591
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3592Starting with version 1.0.7, you can find out which version of the library
3593you are using at run-time:
3594
3595 png_uint_32 libpng_vn = png_access_version_number();
3596
3597The number libpng_vn is constructed from the major version, minor
3598version with leading zero, and release number with leading zero,
3599(e.g., libpng_vn for version 1.0.7 is 10007).
3600
3601You can also check which version of png.h you used when compiling your
3602application:
3603
3604 png_uint_32 application_vn = PNG_LIBPNG_VER;
3605
Glenn Randers-Pehrson1fd5fb32001-05-06 05:34:26 -0500[diff] [blame]3606.SH IX. Y2K Compliance in libpng
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]3607
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame^]3608June 23, 2001
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]3609
3610Since the PNG Development group is an ad-hoc body, we can't make
3611an official declaration.
3612
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3613This is your unofficial assurance that libpng from version 0.71 and
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame^]3614upward through 1.2.0beta4 are Y2K compliant. It is my belief that earlier
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3615versions were also Y2K compliant.
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]3616
3617Libpng only has three year fields. One is a 2-byte unsigned integer that
3618will hold years up to 65535. The other two hold the date in text
3619format, and will hold years up to 9999.
3620
3621The integer is
3622 "png_uint_16 year" in png_time_struct.
3623
3624The strings are
3625 "png_charp time_buffer" in png_struct and
3626 "near_time_buffer", which is a local character string in png.c.
3627
3628There are seven time-related functions:
3629
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3630 png_convert_to_rfc_1123() in png.c
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]3631 (formerly png_convert_to_rfc_1152() in error)
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3632 png_convert_from_struct_tm() in pngwrite.c, called
3633 in pngwrite.c
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]3634 png_convert_from_time_t() in pngwrite.c
3635 png_get_tIME() in pngget.c
3636 png_handle_tIME() in pngrutil.c, called in pngread.c
3637 png_set_tIME() in pngset.c
3638 png_write_tIME() in pngwutil.c, called in pngwrite.c
3639
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3640All appear to handle dates properly in a Y2K environment. The
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]3641png_convert_from_time_t() function calls gmtime() to convert from system
3642clock time, which returns (year - 1900), which we properly convert to
3643the full 4-digit year. There is a possibility that applications using
3644libpng are not passing 4-digit years into the png_convert_to_rfc_1123()
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3645function, or that they are incorrectly passing only a 2-digit year
3646instead of "year - 1900" into the png_convert_from_struct_tm() function,
3647but this is not under our control. The libpng documentation has always
3648stated that it works with 4-digit years, and the APIs have been
3649documented as such.
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]3650
3651The tIME chunk itself is also Y2K compliant. It uses a 2-byte unsigned
3652integer to hold the year, and can hold years as large as 65535.
3653
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3654zlib, upon which libpng depends, is also Y2K compliant. It contains
3655no date-related code.
3656
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]3657
3658 Glenn Randers-Pehrson
3659 libpng maintainer
3660 PNG Development Group
3661
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3662.SH NOTE
3663
3664Note about libpng version numbers:
3665
3666Due to various miscommunications, unforeseen code incompatibilities
3667and occasional factors outside the authors' control, version numbering
3668on the library has not always been consistent and straightforward.
3669The following table summarizes matters since version 0.89c, which was
3670the first widely used release:
3671
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3672 source png.h png.h shared-lib
3673 version string int version
3674 ------- ------ ----- ----------
3675 0.89c ("beta 3") 0.89 89 1.0.89
3676 0.90 ("beta 4") 0.90 90 0.90
3677 0.95 ("beta 5") 0.95 95 0.95
3678 0.96 ("beta 6") 0.96 96 0.96
3679 0.97b ("beta 7") 1.00.97 97 1.0.1
3680 0.97c 0.97 97 2.0.97
3681 0.98 0.98 98 2.0.98
3682 0.99 0.99 98 2.0.99
3683 0.99a-m 0.99 99 2.0.99
3684 1.00 1.00 100 2.1.0
3685 1.0.0 1.0.0 100 2.1.0
3686 1.0.0 (from here on, the 100 2.1.0
3687 1.0.1 png.h string is 10001 2.1.0
3688 1.0.1a-e identical to the 10002 from here on, the
3689 1.0.2 source version) 10002 shared library is 2.V
3690 1.0.2a-b 10003 where V is the source
3691 1.0.1 10001 code version except as
3692 1.0.1a-e 10002 2.1.0.1a-e noted.
3693 1.0.2 10002 2.1.0.2
3694 1.0.2a-b 10003 2.1.0.2a-b
3695 1.0.3 10003 2.1.0.3
3696 1.0.3a-d 10004 2.1.0.3a-d
3697 1.0.4 10004 2.1.0.4
3698 1.0.4a-f 10005 2.1.0.4a-f
3699 1.0.5 (+ 2 patches) 10005 2.1.0.5
3700 1.0.5a-d 10006 2.1.0.5a-d
3701 1.0.5e-r 10100 2.1.0.5e-r
3702 1.0.5s-v 10006 2.1.0.5s-v
3703 1.0.6 (+ 3 patches) 10006 2.1.0.6
3704 1.0.6d-g 10007 2.1.0.6d-g
3705 1.0.6h 10007 10.6h
3706 1.0.6i 10007 10.6i
3707 1.0.6j 10007 2.1.0.6j
3708 1.0.7beta11-14 DLLNUM 10007 2.1.0.7beta11-14
3709 1.0.7beta15-18 1 10007 2.1.0.7beta15-18
3710 1.0.7rc1-2 1 10007 2.1.0.7rc1-2
3711 1.0.7 1 10007 2.1.0.7
3712 1.0.8beta1-4 1 10008 2.1.0.8beta1-4
3713 1.0.8rc1 1 10008 2.1.0.8rc1
3714 1.0.8 1 10008 2.1.0.8
3715 1.0.9beta1-6 1 10009 2.1.0.9beta1-6
3716 1.0.9rc1 1 10009 2.1.0.9rc1
3717 1.0.9beta7-10 1 10009 2.1.0.9beta7-10
3718 1.0.9rc2 1 10009 2.1.0.9rc2
3719 1.0.9 1 10009 2.1.0.9
Glenn Randers-Pehrsone1644472001-03-23 05:06:56 -0600[diff] [blame]3720 1.0.10beta1 1 10010 2.1.0.10beta1
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3721 1.0.10rc1 1 10010 2.1.0.10rc1
Glenn Randers-Pehrson13cfbac2001-03-30 06:42:28 -0600[diff] [blame]3722 1.0.10 1 10010 2.1.0.10
Glenn Randers-Pehrsone1eff582001-04-14 20:15:41 -0500[diff] [blame]3723 1.0.11beta1-3 1 10011 2.1.0.11beta1-3
Glenn Randers-Pehrson82ae3832001-04-20 10:32:10 -0500[diff] [blame]3724 1.0.11rc1 1 10011 2.1.0.11rc1
Glenn Randers-Pehrson32835392001-04-27 08:29:32 -0500[diff] [blame]3725 1.0.11 1 10011 2.1.0.11
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame^]3726 1.0.12beta1-2 2 10012 2.1.0.12beta1-2
3727 1.0.12rc1 2 10012 2.1.0.12rc1
3728 1.0.12 2 10012 2.1.0.12
3729 1.1.0a-f - 10100 2.1.1.0a-f abandoned
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]3730 1.2.0beta1-2 2 10200 2.1.2.0beta1-2
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame^]3731 1.2.0beta3-4 3 10200 3.1.2.0beta3-4
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3732
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3733Henceforth the source version will match the shared-library minor
3734and patch numbers; the shared-library major version number will be
3735used for changes in backward compatibility, as it is intended. The
3736PNG_PNGLIB_VER macro, which is not used within libpng but is available
3737for applications, is an unsigned integer of the form xyyzz corresponding
3738to 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]3739were given the previous public release number plus a letter, until
3740version 1.0.6j; from then on they were given the upcoming public
3741release number plus "betaNN" or "rcN".
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3742
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3743.SH "SEE ALSO"
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3744libpngpf(3), png(5)
3745.LP
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3746.IR libpng :
3747.IP
3748ftp://ftp.uu.net/graphics/png
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]3749http://www.libpng.org/pub/png
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3750
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3751.LP
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3752.IR zlib :
3753.IP
3754(generally) at the same location as
3755.I libpng
3756or at
3757.br
3758ftp://ftp.uu.net/pub/archiving/zip/zlib
3759.br
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]3760ftp://ftp.info-zip.org/pub/infozip/zlib
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3761
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3762.LP
3763.IR PNG specification: RFC 2083
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3764.IP
3765(generally) at the same location as
3766.I libpng
3767or at
3768.br
3769ftp://ds.internic.net/rfc/rfc2083.txt
3770.br
3771or (as a W3C Recommendation) at
3772.br
3773http://www.w3.org/TR/REC-png.html
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3774
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3775.LP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3776In the case of any inconsistency between the PNG specification
3777and this library, the specification takes precedence.
3778
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3779.SH AUTHORS
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3780This man page: Glenn Randers-Pehrson
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3781<randeg@alum.rpi.edu>
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3782
3783The contributing authors would like to thank all those who helped
3784with testing, bug fixes, and patience. This wouldn't have been
3785possible without all of you.
3786
3787Thanks to Frank J. T. Wojcik for helping with the documentation.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3788
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame^]3789Libpng version 1.2.0beta4 - June 23, 2001:
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3790Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3791Currently maintained by Glenn Randers-Pehrson (randeg@alum.rpi.edu).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3792
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3793Supported by the PNG development group
3794.br
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3795(png-implement@ccrc.wustl.edu).
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3796
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]3797.SH COPYRIGHT NOTICE, DISCLAIMER, and LICENSE:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3798
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]3799(This copy of the libpng notices is provided for your convenience. In case of
3800any discrepancy between this copy and the notices in the file png.h that is
3801included in the libpng distribution, the latter shall prevail.)
3802
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]3803If you modify libpng you may insert additional notices immediately following
3804this sentence.
3805
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame^]3806libpng versions 1.0.7, July 1, 2000, through 1.2.0beta4, June 23, 2001, are
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3807Copyright (c) 2000-2001 Glenn Randers-Pehrson, and are
Glenn Randers-Pehrson32fc5ce2000-07-24 06:34:14 -0500[diff] [blame]3808distributed according to the same disclaimer and license as libpng-1.0.6
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]3809with the following individuals added to the list of Contributing Authors
3810
3811 Simon-Pierre Cadieux
3812 Eric S. Raymond
3813 Gilles Vollant
3814
3815and with the following additions to the disclaimer:
3816
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3817 There is no warranty against interference with your
3818 enjoyment of the library or against infringement.
3819 There is no warranty that our efforts or the library
3820 will fulfill any of your particular purposes or needs.
3821 This library is provided with all faults, and the entire
3822 risk of satisfactory quality, performance, accuracy, and
3823 effort is with the user.
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]3824
3825libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
3826Copyright (c) 1998, 1999 Glenn Randers-Pehrson
3827Distributed according to the same disclaimer and license as libpng-0.96,
3828with the following individuals added to the list of Contributing Authors:
3829
3830 Tom Lane
3831 Glenn Randers-Pehrson
3832 Willem van Schaik
3833
3834libpng versions 0.89, June 1996, through 0.96, May 1997, are
Glenn Randers-Pehrson54a066a1999-09-19 06:04:18 -0500[diff] [blame]3835Copyright (c) 1996, 1997 Andreas Dilger
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]3836Distributed according to the same disclaimer and license as libpng-0.88,
3837with the following individuals added to the list of Contributing Authors:
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]3838
3839 John Bowler
3840 Kevin Bracey
3841 Sam Bushell
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]3842 Magnus Holmgren
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]3843 Greg Roelofs
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]3844 Tom Tanner
3845
3846libpng versions 0.5, May 1995, through 0.88, January 1996, are
3847Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
3848
3849For the purposes of this copyright and license, "Contributing Authors"
3850is defined as the following set of individuals:
3851
3852 Andreas Dilger
3853 Dave Martindale
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]3854 Guy Eric Schalnat
3855 Paul Schmidt
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]3856 Tim Wegner
Glenn Randers-Pehrsonc9442291999-01-06 21:50:16 -0600[diff] [blame]3857
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]3858The PNG Reference Library is supplied "AS IS". The Contributing Authors
3859and Group 42, Inc. disclaim all warranties, expressed or implied,
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3860including, without limitation, the warranties of merchantability and of
3861fitness for any purpose. The Contributing Authors and Group 42, Inc.
3862assume no liability for direct, indirect, incidental, special, exemplary,
3863or consequential damages, which may result from the use of the PNG
3864Reference Library, even if advised of the possibility of such damage.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3865
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3866Permission is hereby granted to use, copy, modify, and distribute this
3867source code, or portions hereof, for any purpose, without fee, subject
3868to the following restrictions:
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3869
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]38701. The origin of this source code must not be misrepresented.
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3871
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]38722. Altered versions must be plainly marked as such and
3873 must not be misrepresented as being the original source.
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3874
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]38753. This Copyright notice may not be removed or altered from
3876 any source or altered source distribution.
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3877
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3878The Contributing Authors and Group 42, Inc. specifically permit, without
3879fee, and encourage the use of this source code as a component to
3880supporting the PNG file format in commercial products. If you use this
3881source code in a product, acknowledgment is not required but would be
3882appreciated.
3883
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]3884
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3885A "png_get_copyright" function is available, for convenient use in "about"
3886boxes and the like:
3887
3888 printf("%s",png_get_copyright(NULL));
3889
3890Also, the PNG logo (in PNG format, of course) is supplied in the
Glenn Randers-Pehrsona4d54bd2000-07-14 08:15:12 -0500[diff] [blame]3891files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31).
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3892
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]3893Libpng is OSI Certified Open Source Software. OSI Certified Open Source is a
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]3894certification mark of the Open Source Initiative.
3895
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]3896Glenn Randers-Pehrson
3897randeg@alum.rpi.edu
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame^]3898June 23, 2001
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]3899
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]3900.\" end of man page
3901