comparison thirdparty/LodePNG/lodepng.h @ 695:d2e8b5edea7e

add: png loading with LodePNG (thanks LodePNG-author, this is a super amazing piece of code!)
author Sam <sam@basx.dev>
date Sat, 20 May 2023 16:35:23 +0700
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694:1fdcdceb13ae 695:d2e8b5edea7e
1 /*
2 LodePNG version 20230410
3
4 Copyright (c) 2005-2023 Lode Vandevenne
5
6 This software is provided 'as-is', without any express or implied
7 warranty. In no event will the authors be held liable for any damages
8 arising from the use of this software.
9
10 Permission is granted to anyone to use this software for any purpose,
11 including commercial applications, and to alter it and redistribute it
12 freely, subject to the following restrictions:
13
14 1. The origin of this software must not be misrepresented; you must not
15 claim that you wrote the original software. If you use this software
16 in a product, an acknowledgment in the product documentation would be
17 appreciated but is not required.
18
19 2. Altered source versions must be plainly marked as such, and must not be
20 misrepresented as being the original software.
21
22 3. This notice may not be removed or altered from any source
23 distribution.
24 */
25
26 #ifndef LODEPNG_H
27 #define LODEPNG_H
28
29 #include <string.h> /*for size_t*/
30
31 extern const char* LODEPNG_VERSION_STRING;
32
33 /*
34 The following #defines are used to create code sections. They can be disabled
35 to disable code sections, which can give faster compile time and smaller binary.
36 The "NO_COMPILE" defines are designed to be used to pass as defines to the
37 compiler command to disable them without modifying this header, e.g.
38 -DLODEPNG_NO_COMPILE_ZLIB for gcc or clang.
39 */
40 /*deflate & zlib. If disabled, you must specify alternative zlib functions in
41 the custom_zlib field of the compress and decompress settings*/
42 #ifndef LODEPNG_NO_COMPILE_ZLIB
43 /*pass -DLODEPNG_NO_COMPILE_ZLIB to the compiler to disable this, or comment out LODEPNG_COMPILE_ZLIB below*/
44 #define LODEPNG_COMPILE_ZLIB
45 #endif
46
47 /*png encoder and png decoder*/
48 #ifndef LODEPNG_NO_COMPILE_PNG
49 /*pass -DLODEPNG_NO_COMPILE_PNG to the compiler to disable this, or comment out LODEPNG_COMPILE_PNG below*/
50 #define LODEPNG_COMPILE_PNG
51 #endif
52
53 /*deflate&zlib decoder and png decoder*/
54 #ifndef LODEPNG_NO_COMPILE_DECODER
55 /*pass -DLODEPNG_NO_COMPILE_DECODER to the compiler to disable this, or comment out LODEPNG_COMPILE_DECODER below*/
56 #define LODEPNG_COMPILE_DECODER
57 #endif
58
59 /*deflate&zlib encoder and png encoder*/
60 #ifndef LODEPNG_NO_COMPILE_ENCODER
61 /*pass -DLODEPNG_NO_COMPILE_ENCODER to the compiler to disable this, or comment out LODEPNG_COMPILE_ENCODER below*/
62 #define LODEPNG_COMPILE_ENCODER
63 #endif
64
65 /*the optional built in harddisk file loading and saving functions*/
66 #ifndef LODEPNG_NO_COMPILE_DISK
67 /*pass -DLODEPNG_NO_COMPILE_DISK to the compiler to disable this, or comment out LODEPNG_COMPILE_DISK below*/
68 #define LODEPNG_COMPILE_DISK
69 #endif
70
71 /*support for chunks other than IHDR, IDAT, PLTE, tRNS, IEND: ancillary and unknown chunks*/
72 #ifndef LODEPNG_NO_COMPILE_ANCILLARY_CHUNKS
73 /*pass -DLODEPNG_NO_COMPILE_ANCILLARY_CHUNKS to the compiler to disable this,
74 or comment out LODEPNG_COMPILE_ANCILLARY_CHUNKS below*/
75 #define LODEPNG_COMPILE_ANCILLARY_CHUNKS
76 #endif
77
78 /*ability to convert error numerical codes to English text string*/
79 #ifndef LODEPNG_NO_COMPILE_ERROR_TEXT
80 /*pass -DLODEPNG_NO_COMPILE_ERROR_TEXT to the compiler to disable this,
81 or comment out LODEPNG_COMPILE_ERROR_TEXT below*/
82 #define LODEPNG_COMPILE_ERROR_TEXT
83 #endif
84
85 /*Compile the default allocators (C's free, malloc and realloc). If you disable this,
86 you can define the functions lodepng_free, lodepng_malloc and lodepng_realloc in your
87 source files with custom allocators.*/
88 #ifndef LODEPNG_NO_COMPILE_ALLOCATORS
89 /*pass -DLODEPNG_NO_COMPILE_ALLOCATORS to the compiler to disable the built-in ones,
90 or comment out LODEPNG_COMPILE_ALLOCATORS below*/
91 #define LODEPNG_COMPILE_ALLOCATORS
92 #endif
93
94 /*Disable built-in CRC function, in that case a custom implementation of
95 lodepng_crc32 must be defined externally so that it can be linked in.
96 The default built-in CRC code comes with 8KB of lookup tables, so for memory constrained environment you may want it
97 disabled and provide a much smaller implementation externally as said above. You can find such an example implementation
98 in a comment in the lodepng.c(pp) file in the 'else' case of the searchable LODEPNG_COMPILE_CRC section.*/
99 #ifndef LODEPNG_NO_COMPILE_CRC
100 /*pass -DLODEPNG_NO_COMPILE_CRC to the compiler to disable the built-in one,
101 or comment out LODEPNG_COMPILE_CRC below*/
102 #define LODEPNG_COMPILE_CRC
103 #endif
104
105 /*compile the C++ version (you can disable the C++ wrapper here even when compiling for C++)*/
106 #ifdef __cplusplus
107 #ifndef LODEPNG_NO_COMPILE_CPP
108 /*pass -DLODEPNG_NO_COMPILE_CPP to the compiler to disable C++ (not needed if a C-only compiler),
109 or comment out LODEPNG_COMPILE_CPP below*/
110 #define LODEPNG_COMPILE_CPP
111 #endif
112 #endif
113
114 #ifdef LODEPNG_COMPILE_CPP
115 #include <vector>
116 #include <string>
117 #endif /*LODEPNG_COMPILE_CPP*/
118
119 #ifdef LODEPNG_COMPILE_PNG
120 /*The PNG color types (also used for raw image).*/
121 typedef enum LodePNGColorType {
122 LCT_GREY = 0, /*grayscale: 1,2,4,8,16 bit*/
123 LCT_RGB = 2, /*RGB: 8,16 bit*/
124 LCT_PALETTE = 3, /*palette: 1,2,4,8 bit*/
125 LCT_GREY_ALPHA = 4, /*grayscale with alpha: 8,16 bit*/
126 LCT_RGBA = 6, /*RGB with alpha: 8,16 bit*/
127 /*LCT_MAX_OCTET_VALUE lets the compiler allow this enum to represent any invalid
128 byte value from 0 to 255 that could be present in an invalid PNG file header. Do
129 not use, compare with or set the name LCT_MAX_OCTET_VALUE, instead either use
130 the valid color type names above, or numeric values like 1 or 7 when checking for
131 particular disallowed color type byte values, or cast to integer to print it.*/
132 LCT_MAX_OCTET_VALUE = 255
133 } LodePNGColorType;
134
135 #ifdef LODEPNG_COMPILE_DECODER
136 /*
137 Converts PNG data in memory to raw pixel data.
138 out: Output parameter. Pointer to buffer that will contain the raw pixel data.
139 After decoding, its size is w * h * (bytes per pixel) bytes larger than
140 initially. Bytes per pixel depends on colortype and bitdepth.
141 Must be freed after usage with free(*out).
142 Note: for 16-bit per channel colors, uses big endian format like PNG does.
143 w: Output parameter. Pointer to width of pixel data.
144 h: Output parameter. Pointer to height of pixel data.
145 in: Memory buffer with the PNG file.
146 insize: size of the in buffer.
147 colortype: the desired color type for the raw output image. See explanation on PNG color types.
148 bitdepth: the desired bit depth for the raw output image. See explanation on PNG color types.
149 Return value: LodePNG error code (0 means no error).
150 */
151 unsigned lodepng_decode_memory(unsigned char** out, unsigned* w, unsigned* h,
152 const unsigned char* in, size_t insize,
153 LodePNGColorType colortype, unsigned bitdepth);
154
155 /*Same as lodepng_decode_memory, but always decodes to 32-bit RGBA raw image*/
156 unsigned lodepng_decode32(unsigned char** out, unsigned* w, unsigned* h,
157 const unsigned char* in, size_t insize);
158
159 /*Same as lodepng_decode_memory, but always decodes to 24-bit RGB raw image*/
160 unsigned lodepng_decode24(unsigned char** out, unsigned* w, unsigned* h,
161 const unsigned char* in, size_t insize);
162
163 #ifdef LODEPNG_COMPILE_DISK
164 /*
165 Load PNG from disk, from file with given name.
166 Same as the other decode functions, but instead takes a filename as input.
167
168 NOTE: Wide-character filenames are not supported, you can use an external method
169 to handle such files and decode in-memory.*/
170 unsigned lodepng_decode_file(unsigned char** out, unsigned* w, unsigned* h,
171 const char* filename,
172 LodePNGColorType colortype, unsigned bitdepth);
173
174 /*Same as lodepng_decode_file, but always decodes to 32-bit RGBA raw image.
175
176 NOTE: Wide-character filenames are not supported, you can use an external method
177 to handle such files and decode in-memory.*/
178 unsigned lodepng_decode32_file(unsigned char** out, unsigned* w, unsigned* h,
179 const char* filename);
180
181 /*Same as lodepng_decode_file, but always decodes to 24-bit RGB raw image.
182
183 NOTE: Wide-character filenames are not supported, you can use an external method
184 to handle such files and decode in-memory.*/
185 unsigned lodepng_decode24_file(unsigned char** out, unsigned* w, unsigned* h,
186 const char* filename);
187 #endif /*LODEPNG_COMPILE_DISK*/
188 #endif /*LODEPNG_COMPILE_DECODER*/
189
190
191 #ifdef LODEPNG_COMPILE_ENCODER
192 /*
193 Converts raw pixel data into a PNG image in memory. The colortype and bitdepth
194 of the output PNG image cannot be chosen, they are automatically determined
195 by the colortype, bitdepth and content of the input pixel data.
196 Note: for 16-bit per channel colors, needs big endian format like PNG does.
197 out: Output parameter. Pointer to buffer that will contain the PNG image data.
198 Must be freed after usage with free(*out).
199 outsize: Output parameter. Pointer to the size in bytes of the out buffer.
200 image: The raw pixel data to encode. The size of this buffer should be
201 w * h * (bytes per pixel), bytes per pixel depends on colortype and bitdepth.
202 w: width of the raw pixel data in pixels.
203 h: height of the raw pixel data in pixels.
204 colortype: the color type of the raw input image. See explanation on PNG color types.
205 bitdepth: the bit depth of the raw input image. See explanation on PNG color types.
206 Return value: LodePNG error code (0 means no error).
207 */
208 unsigned lodepng_encode_memory(unsigned char** out, size_t* outsize,
209 const unsigned char* image, unsigned w, unsigned h,
210 LodePNGColorType colortype, unsigned bitdepth);
211
212 /*Same as lodepng_encode_memory, but always encodes from 32-bit RGBA raw image.*/
213 unsigned lodepng_encode32(unsigned char** out, size_t* outsize,
214 const unsigned char* image, unsigned w, unsigned h);
215
216 /*Same as lodepng_encode_memory, but always encodes from 24-bit RGB raw image.*/
217 unsigned lodepng_encode24(unsigned char** out, size_t* outsize,
218 const unsigned char* image, unsigned w, unsigned h);
219
220 #ifdef LODEPNG_COMPILE_DISK
221 /*
222 Converts raw pixel data into a PNG file on disk.
223 Same as the other encode functions, but instead takes a filename as output.
224
225 NOTE: This overwrites existing files without warning!
226
227 NOTE: Wide-character filenames are not supported, you can use an external method
228 to handle such files and encode in-memory.*/
229 unsigned lodepng_encode_file(const char* filename,
230 const unsigned char* image, unsigned w, unsigned h,
231 LodePNGColorType colortype, unsigned bitdepth);
232
233 /*Same as lodepng_encode_file, but always encodes from 32-bit RGBA raw image.
234
235 NOTE: Wide-character filenames are not supported, you can use an external method
236 to handle such files and encode in-memory.*/
237 unsigned lodepng_encode32_file(const char* filename,
238 const unsigned char* image, unsigned w, unsigned h);
239
240 /*Same as lodepng_encode_file, but always encodes from 24-bit RGB raw image.
241
242 NOTE: Wide-character filenames are not supported, you can use an external method
243 to handle such files and encode in-memory.*/
244 unsigned lodepng_encode24_file(const char* filename,
245 const unsigned char* image, unsigned w, unsigned h);
246 #endif /*LODEPNG_COMPILE_DISK*/
247 #endif /*LODEPNG_COMPILE_ENCODER*/
248
249
250 #ifdef LODEPNG_COMPILE_CPP
251 namespace lodepng {
252 #ifdef LODEPNG_COMPILE_DECODER
253 /*Same as lodepng_decode_memory, but decodes to an std::vector. The colortype
254 is the format to output the pixels to. Default is RGBA 8-bit per channel.*/
255 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
256 const unsigned char* in, size_t insize,
257 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
258 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
259 const std::vector<unsigned char>& in,
260 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
261 #ifdef LODEPNG_COMPILE_DISK
262 /*
263 Converts PNG file from disk to raw pixel data in memory.
264 Same as the other decode functions, but instead takes a filename as input.
265
266 NOTE: Wide-character filenames are not supported, you can use an external method
267 to handle such files and decode in-memory.
268 */
269 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
270 const std::string& filename,
271 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
272 #endif /* LODEPNG_COMPILE_DISK */
273 #endif /* LODEPNG_COMPILE_DECODER */
274
275 #ifdef LODEPNG_COMPILE_ENCODER
276 /*Same as lodepng_encode_memory, but encodes to an std::vector. colortype
277 is that of the raw input data. The output PNG color type will be auto chosen.*/
278 unsigned encode(std::vector<unsigned char>& out,
279 const unsigned char* in, unsigned w, unsigned h,
280 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
281 unsigned encode(std::vector<unsigned char>& out,
282 const std::vector<unsigned char>& in, unsigned w, unsigned h,
283 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
284 #ifdef LODEPNG_COMPILE_DISK
285 /*
286 Converts 32-bit RGBA raw pixel data into a PNG file on disk.
287 Same as the other encode functions, but instead takes a filename as output.
288
289 NOTE: This overwrites existing files without warning!
290
291 NOTE: Wide-character filenames are not supported, you can use an external method
292 to handle such files and decode in-memory.
293 */
294 unsigned encode(const std::string& filename,
295 const unsigned char* in, unsigned w, unsigned h,
296 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
297 unsigned encode(const std::string& filename,
298 const std::vector<unsigned char>& in, unsigned w, unsigned h,
299 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
300 #endif /* LODEPNG_COMPILE_DISK */
301 #endif /* LODEPNG_COMPILE_ENCODER */
302 } /* namespace lodepng */
303 #endif /*LODEPNG_COMPILE_CPP*/
304 #endif /*LODEPNG_COMPILE_PNG*/
305
306 #ifdef LODEPNG_COMPILE_ERROR_TEXT
307 /*Returns an English description of the numerical error code.*/
308 const char* lodepng_error_text(unsigned code);
309 #endif /*LODEPNG_COMPILE_ERROR_TEXT*/
310
311 #ifdef LODEPNG_COMPILE_DECODER
312 /*Settings for zlib decompression*/
313 typedef struct LodePNGDecompressSettings LodePNGDecompressSettings;
314 struct LodePNGDecompressSettings {
315 /* Check LodePNGDecoderSettings for more ignorable errors such as ignore_crc */
316 unsigned ignore_adler32; /*if 1, continue and don't give an error message if the Adler32 checksum is corrupted*/
317 unsigned ignore_nlen; /*ignore complement of len checksum in uncompressed blocks*/
318
319 /*Maximum decompressed size, beyond this the decoder may (and is encouraged to) stop decoding,
320 return an error, output a data size > max_output_size and all the data up to that point. This is
321 not hard limit nor a guarantee, but can prevent excessive memory usage. This setting is
322 ignored by the PNG decoder, but is used by the deflate/zlib decoder and can be used by custom ones.
323 Set to 0 to impose no limit (the default).*/
324 size_t max_output_size;
325
326 /*use custom zlib decoder instead of built in one (default: null).
327 Should return 0 if success, any non-0 if error (numeric value not exposed).*/
328 unsigned (*custom_zlib)(unsigned char**, size_t*,
329 const unsigned char*, size_t,
330 const LodePNGDecompressSettings*);
331 /*use custom deflate decoder instead of built in one (default: null)
332 if custom_zlib is not null, custom_inflate is ignored (the zlib format uses deflate).
333 Should return 0 if success, any non-0 if error (numeric value not exposed).*/
334 unsigned (*custom_inflate)(unsigned char**, size_t*,
335 const unsigned char*, size_t,
336 const LodePNGDecompressSettings*);
337
338 const void* custom_context; /*optional custom settings for custom functions*/
339 };
340
341 extern const LodePNGDecompressSettings lodepng_default_decompress_settings;
342 void lodepng_decompress_settings_init(LodePNGDecompressSettings* settings);
343 #endif /*LODEPNG_COMPILE_DECODER*/
344
345 #ifdef LODEPNG_COMPILE_ENCODER
346 /*
347 Settings for zlib compression. Tweaking these settings tweaks the balance
348 between speed and compression ratio.
349 */
350 typedef struct LodePNGCompressSettings LodePNGCompressSettings;
351 struct LodePNGCompressSettings /*deflate = compress*/ {
352 /*LZ77 related settings*/
353 unsigned btype; /*the block type for LZ (0, 1, 2 or 3, see zlib standard). Should be 2 for proper compression.*/
354 unsigned use_lz77; /*whether or not to use LZ77. Should be 1 for proper compression.*/
355 unsigned windowsize; /*must be a power of two <= 32768. higher compresses more but is slower. Default value: 2048.*/
356 unsigned minmatch; /*minimum lz77 length. 3 is normally best, 6 can be better for some PNGs. Default: 0*/
357 unsigned nicematch; /*stop searching if >= this length found. Set to 258 for best compression. Default: 128*/
358 unsigned lazymatching; /*use lazy matching: better compression but a bit slower. Default: true*/
359
360 /*use custom zlib encoder instead of built in one (default: null)*/
361 unsigned (*custom_zlib)(unsigned char**, size_t*,
362 const unsigned char*, size_t,
363 const LodePNGCompressSettings*);
364 /*use custom deflate encoder instead of built in one (default: null)
365 if custom_zlib is used, custom_deflate is ignored since only the built in
366 zlib function will call custom_deflate*/
367 unsigned (*custom_deflate)(unsigned char**, size_t*,
368 const unsigned char*, size_t,
369 const LodePNGCompressSettings*);
370
371 const void* custom_context; /*optional custom settings for custom functions*/
372 };
373
374 extern const LodePNGCompressSettings lodepng_default_compress_settings;
375 void lodepng_compress_settings_init(LodePNGCompressSettings* settings);
376 #endif /*LODEPNG_COMPILE_ENCODER*/
377
378 #ifdef LODEPNG_COMPILE_PNG
379 /*
380 Color mode of an image. Contains all information required to decode the pixel
381 bits to RGBA colors. This information is the same as used in the PNG file
382 format, and is used both for PNG and raw image data in LodePNG.
383 */
384 typedef struct LodePNGColorMode {
385 /*header (IHDR)*/
386 LodePNGColorType colortype; /*color type, see PNG standard or documentation further in this header file*/
387 unsigned bitdepth; /*bits per sample, see PNG standard or documentation further in this header file*/
388
389 /*
390 palette (PLTE and tRNS)
391
392 Dynamically allocated with the colors of the palette, including alpha.
393 This field may not be allocated directly, use lodepng_color_mode_init first,
394 then lodepng_palette_add per color to correctly initialize it (to ensure size
395 of exactly 1024 bytes).
396
397 The alpha channels must be set as well, set them to 255 for opaque images.
398
399 When decoding, with the default settings you can ignore this palette, since
400 LodePNG already fills the palette colors in the pixels of the raw RGBA output,
401 but when decoding to the original PNG color mode it is needed to reconstruct
402 the colors.
403
404 The palette is only supported for color type 3.
405 */
406 unsigned char* palette; /*palette in RGBARGBA... order. Must be either 0, or when allocated must have 1024 bytes*/
407 size_t palettesize; /*palette size in number of colors (amount of used bytes is 4 * palettesize)*/
408
409 /*
410 transparent color key (tRNS)
411
412 This color uses the same bit depth as the bitdepth value in this struct, which can be 1-bit to 16-bit.
413 For grayscale PNGs, r, g and b will all 3 be set to the same.
414
415 When decoding, by default you can ignore this information, since LodePNG sets
416 pixels with this key to transparent already in the raw RGBA output.
417
418 The color key is only supported for color types 0 and 2.
419 */
420 unsigned key_defined; /*is a transparent color key given? 0 = false, 1 = true*/
421 unsigned key_r; /*red/grayscale component of color key*/
422 unsigned key_g; /*green component of color key*/
423 unsigned key_b; /*blue component of color key*/
424 } LodePNGColorMode;
425
426 /*init, cleanup and copy functions to use with this struct*/
427 void lodepng_color_mode_init(LodePNGColorMode* info);
428 void lodepng_color_mode_cleanup(LodePNGColorMode* info);
429 /*return value is error code (0 means no error)*/
430 unsigned lodepng_color_mode_copy(LodePNGColorMode* dest, const LodePNGColorMode* source);
431 /* Makes a temporary LodePNGColorMode that does not need cleanup (no palette) */
432 LodePNGColorMode lodepng_color_mode_make(LodePNGColorType colortype, unsigned bitdepth);
433
434 void lodepng_palette_clear(LodePNGColorMode* info);
435 /*add 1 color to the palette*/
436 unsigned lodepng_palette_add(LodePNGColorMode* info,
437 unsigned char r, unsigned char g, unsigned char b, unsigned char a);
438
439 /*get the total amount of bits per pixel, based on colortype and bitdepth in the struct*/
440 unsigned lodepng_get_bpp(const LodePNGColorMode* info);
441 /*get the amount of color channels used, based on colortype in the struct.
442 If a palette is used, it counts as 1 channel.*/
443 unsigned lodepng_get_channels(const LodePNGColorMode* info);
444 /*is it a grayscale type? (only colortype 0 or 4)*/
445 unsigned lodepng_is_greyscale_type(const LodePNGColorMode* info);
446 /*has it got an alpha channel? (only colortype 2 or 6)*/
447 unsigned lodepng_is_alpha_type(const LodePNGColorMode* info);
448 /*has it got a palette? (only colortype 3)*/
449 unsigned lodepng_is_palette_type(const LodePNGColorMode* info);
450 /*only returns true if there is a palette and there is a value in the palette with alpha < 255.
451 Loops through the palette to check this.*/
452 unsigned lodepng_has_palette_alpha(const LodePNGColorMode* info);
453 /*
454 Check if the given color info indicates the possibility of having non-opaque pixels in the PNG image.
455 Returns true if the image can have translucent or invisible pixels (it still be opaque if it doesn't use such pixels).
456 Returns false if the image can only have opaque pixels.
457 In detail, it returns true only if it's a color type with alpha, or has a palette with non-opaque values,
458 or if "key_defined" is true.
459 */
460 unsigned lodepng_can_have_alpha(const LodePNGColorMode* info);
461 /*Returns the byte size of a raw image buffer with given width, height and color mode*/
462 size_t lodepng_get_raw_size(unsigned w, unsigned h, const LodePNGColorMode* color);
463
464 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
465 /*The information of a Time chunk in PNG.*/
466 typedef struct LodePNGTime {
467 unsigned year; /*2 bytes used (0-65535)*/
468 unsigned month; /*1-12*/
469 unsigned day; /*1-31*/
470 unsigned hour; /*0-23*/
471 unsigned minute; /*0-59*/
472 unsigned second; /*0-60 (to allow for leap seconds)*/
473 } LodePNGTime;
474 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
475
476 /*Information about the PNG image, except pixels, width and height.*/
477 typedef struct LodePNGInfo {
478 /*header (IHDR), palette (PLTE) and transparency (tRNS) chunks*/
479 unsigned compression_method;/*compression method of the original file. Always 0.*/
480 unsigned filter_method; /*filter method of the original file*/
481 unsigned interlace_method; /*interlace method of the original file: 0=none, 1=Adam7*/
482 LodePNGColorMode color; /*color type and bits, palette and transparency of the PNG file*/
483
484 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
485 /*
486 Suggested background color chunk (bKGD)
487
488 This uses the same color mode and bit depth as the PNG (except no alpha channel),
489 with values truncated to the bit depth in the unsigned integer.
490
491 For grayscale and palette PNGs, the value is stored in background_r. The values
492 in background_g and background_b are then unused. The decoder will set them
493 equal to background_r, the encoder ignores them in this case.
494
495 When decoding, you may get these in a different color mode than the one you requested
496 for the raw pixels: the colortype and bitdepth defined by info_png.color, that is the
497 ones defined in the header of the PNG image, are used.
498
499 When encoding with auto_convert, you must use the color model defined in info_png.color for
500 these values. The encoder normally ignores info_png.color when auto_convert is on, but will
501 use it to interpret these values (and convert copies of them to its chosen color model).
502
503 When encoding, avoid setting this to an expensive color, such as a non-gray value
504 when the image is gray, or the compression will be worse since it will be forced to
505 write the PNG with a more expensive color mode (when auto_convert is on).
506
507 The decoder does not use this background color to edit the color of pixels. This is a
508 completely optional metadata feature.
509 */
510 unsigned background_defined; /*is a suggested background color given?*/
511 unsigned background_r; /*red/gray/palette component of suggested background color*/
512 unsigned background_g; /*green component of suggested background color*/
513 unsigned background_b; /*blue component of suggested background color*/
514
515 /*
516 Non-international text chunks (tEXt and zTXt)
517
518 The char** arrays each contain num strings. The actual messages are in
519 text_strings, while text_keys are keywords that give a short description what
520 the actual text represents, e.g. Title, Author, Description, or anything else.
521
522 All the string fields below including strings, keys, names and language tags are null terminated.
523 The PNG specification uses null characters for the keys, names and tags, and forbids null
524 characters to appear in the main text which is why we can use null termination everywhere here.
525
526 A keyword is minimum 1 character and maximum 79 characters long (plus the
527 additional null terminator). It's discouraged to use a single line length
528 longer than 79 characters for texts.
529
530 Don't allocate these text buffers yourself. Use the init/cleanup functions
531 correctly and use lodepng_add_text and lodepng_clear_text.
532
533 Standard text chunk keywords and strings are encoded using Latin-1.
534 */
535 size_t text_num; /*the amount of texts in these char** buffers (there may be more texts in itext)*/
536 char** text_keys; /*the keyword of a text chunk (e.g. "Comment")*/
537 char** text_strings; /*the actual text*/
538
539 /*
540 International text chunks (iTXt)
541 Similar to the non-international text chunks, but with additional strings
542 "langtags" and "transkeys", and the following text encodings are used:
543 keys: Latin-1, langtags: ASCII, transkeys and strings: UTF-8.
544 keys must be 1-79 characters (plus the additional null terminator), the other
545 strings are any length.
546 */
547 size_t itext_num; /*the amount of international texts in this PNG*/
548 char** itext_keys; /*the English keyword of the text chunk (e.g. "Comment")*/
549 char** itext_langtags; /*language tag for this text's language, ISO/IEC 646 string, e.g. ISO 639 language tag*/
550 char** itext_transkeys; /*keyword translated to the international language - UTF-8 string*/
551 char** itext_strings; /*the actual international text - UTF-8 string*/
552
553 /*time chunk (tIME)*/
554 unsigned time_defined; /*set to 1 to make the encoder generate a tIME chunk*/
555 LodePNGTime time;
556
557 /*phys chunk (pHYs)*/
558 unsigned phys_defined; /*if 0, there is no pHYs chunk and the values below are undefined, if 1 else there is one*/
559 unsigned phys_x; /*pixels per unit in x direction*/
560 unsigned phys_y; /*pixels per unit in y direction*/
561 unsigned phys_unit; /*may be 0 (unknown unit) or 1 (metre)*/
562
563 /*
564 Color profile related chunks: gAMA, cHRM, sRGB, iCPP, sBIT
565
566 LodePNG does not apply any color conversions on pixels in the encoder or decoder and does not interpret these color
567 profile values. It merely passes on the information. If you wish to use color profiles and convert colors, please
568 use these values with a color management library.
569
570 See the PNG, ICC and sRGB specifications for more information about the meaning of these values.
571 */
572
573 /* gAMA chunk: optional, overridden by sRGB or iCCP if those are present. */
574 unsigned gama_defined; /* Whether a gAMA chunk is present (0 = not present, 1 = present). */
575 unsigned gama_gamma; /* Gamma exponent times 100000 */
576
577 /* cHRM chunk: optional, overridden by sRGB or iCCP if those are present. */
578 unsigned chrm_defined; /* Whether a cHRM chunk is present (0 = not present, 1 = present). */
579 unsigned chrm_white_x; /* White Point x times 100000 */
580 unsigned chrm_white_y; /* White Point y times 100000 */
581 unsigned chrm_red_x; /* Red x times 100000 */
582 unsigned chrm_red_y; /* Red y times 100000 */
583 unsigned chrm_green_x; /* Green x times 100000 */
584 unsigned chrm_green_y; /* Green y times 100000 */
585 unsigned chrm_blue_x; /* Blue x times 100000 */
586 unsigned chrm_blue_y; /* Blue y times 100000 */
587
588 /*
589 sRGB chunk: optional. May not appear at the same time as iCCP.
590 If gAMA is also present gAMA must contain value 45455.
591 If cHRM is also present cHRM must contain respectively 31270,32900,64000,33000,30000,60000,15000,6000.
592 */
593 unsigned srgb_defined; /* Whether an sRGB chunk is present (0 = not present, 1 = present). */
594 unsigned srgb_intent; /* Rendering intent: 0=perceptual, 1=rel. colorimetric, 2=saturation, 3=abs. colorimetric */
595
596 /*
597 iCCP chunk: optional. May not appear at the same time as sRGB.
598
599 LodePNG does not parse or use the ICC profile (except its color space header field for an edge case), a
600 separate library to handle the ICC data (not included in LodePNG) format is needed to use it for color
601 management and conversions.
602
603 For encoding, if iCCP is present, gAMA and cHRM are recommended to be added as well with values that match the ICC
604 profile as closely as possible, if you wish to do this you should provide the correct values for gAMA and cHRM and
605 enable their '_defined' flags since LodePNG will not automatically compute them from the ICC profile.
606
607 For encoding, the ICC profile is required by the PNG specification to be an "RGB" profile for non-gray
608 PNG color types and a "GRAY" profile for gray PNG color types. If you disable auto_convert, you must ensure
609 the ICC profile type matches your requested color type, else the encoder gives an error. If auto_convert is
610 enabled (the default), and the ICC profile is not a good match for the pixel data, this will result in an encoder
611 error if the pixel data has non-gray pixels for a GRAY profile, or a silent less-optimal compression of the pixel
612 data if the pixels could be encoded as grayscale but the ICC profile is RGB.
613
614 To avoid this do not set an ICC profile in the image unless there is a good reason for it, and when doing so
615 make sure you compute it carefully to avoid the above problems.
616 */
617 unsigned iccp_defined; /* Whether an iCCP chunk is present (0 = not present, 1 = present). */
618 char* iccp_name; /* Null terminated string with profile name, 1-79 bytes */
619 /*
620 The ICC profile in iccp_profile_size bytes.
621 Don't allocate this buffer yourself. Use the init/cleanup functions
622 correctly and use lodepng_set_icc and lodepng_clear_icc.
623 */
624 unsigned char* iccp_profile;
625 unsigned iccp_profile_size; /* The size of iccp_profile in bytes */
626
627 /*
628 sBIT chunk: significant bits. Optional metadata, only set this if needed.
629
630 If defined, these values give the bit depth of the original data. Since PNG only stores 1, 2, 4, 8 or 16-bit
631 per channel data, the significant bits value can be used to indicate the original encoded data has another
632 sample depth, such as 10 or 12.
633
634 Encoders using this value, when storing the pixel data, should use the most significant bits
635 of the data to store the original bits, and use a good sample depth scaling method such as
636 "left bit replication" to fill in the least significant bits, rather than fill zeroes.
637
638 Decoders using this value, if able to work with data that's e.g. 10-bit or 12-bit, should right
639 shift the data to go back to the original bit depth, but decoders are also allowed to ignore
640 sbit and work e.g. with the 8-bit or 16-bit data from the PNG directly, since thanks
641 to the encoder contract, the values encoded in PNG are in valid range for the PNG bit depth.
642
643 For grayscale images, sbit_g and sbit_b are not used, and for images that don't use color
644 type RGBA or grayscale+alpha, sbit_a is not used (it's not used even for palette images with
645 translucent palette values, or images with color key). The values that are used must be
646 greater than zero and smaller than or equal to the PNG bit depth.
647
648 The color type from the header in the PNG image defines these used and unused fields: if
649 decoding with a color mode conversion, such as always decoding to RGBA, this metadata still
650 only uses the color type of the original PNG, and may e.g. lack the alpha channel info
651 if the PNG was RGB. When encoding with auto_convert (as well as without), also always the
652 color model defined in info_png.color determines this.
653
654 NOTE: enabling sbit can hurt compression, because the encoder can then not always use
655 auto_convert to choose a more optimal color mode for the data, because the PNG format has
656 strict requirements for the allowed sbit values in combination with color modes.
657 For example, setting these fields to 10-bit will force the encoder to keep using a 16-bit per channel
658 color mode, even if the pixel data would in fact fit in a more efficient 8-bit mode.
659 */
660 unsigned sbit_defined; /*is significant bits given? if not, the values below are unused*/
661 unsigned sbit_r; /*red or gray component of significant bits*/
662 unsigned sbit_g; /*green component of significant bits*/
663 unsigned sbit_b; /*blue component of significant bits*/
664 unsigned sbit_a; /*alpha component of significant bits*/
665
666 /* End of color profile related chunks */
667
668
669 /*
670 unknown chunks: chunks not known by LodePNG, passed on byte for byte.
671
672 There are 3 buffers, one for each position in the PNG where unknown chunks can appear.
673 Each buffer contains all unknown chunks for that position consecutively.
674 The 3 positions are:
675 0: between IHDR and PLTE, 1: between PLTE and IDAT, 2: between IDAT and IEND.
676
677 For encoding, do not store critical chunks or known chunks that are enabled with a "_defined" flag
678 above in here, since the encoder will blindly follow this and could then encode an invalid PNG file
679 (such as one with two IHDR chunks or the disallowed combination of sRGB with iCCP). But do use
680 this if you wish to store an ancillary chunk that is not supported by LodePNG (such as sPLT or hIST),
681 or any non-standard PNG chunk.
682
683 Do not allocate or traverse this data yourself. Use the chunk traversing functions declared
684 later, such as lodepng_chunk_next and lodepng_chunk_append, to read/write this struct.
685 */
686 unsigned char* unknown_chunks_data[3];
687 size_t unknown_chunks_size[3]; /*size in bytes of the unknown chunks, given for protection*/
688 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
689 } LodePNGInfo;
690
691 /*init, cleanup and copy functions to use with this struct*/
692 void lodepng_info_init(LodePNGInfo* info);
693 void lodepng_info_cleanup(LodePNGInfo* info);
694 /*return value is error code (0 means no error)*/
695 unsigned lodepng_info_copy(LodePNGInfo* dest, const LodePNGInfo* source);
696
697 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
698 unsigned lodepng_add_text(LodePNGInfo* info, const char* key, const char* str); /*push back both texts at once*/
699 void lodepng_clear_text(LodePNGInfo* info); /*use this to clear the texts again after you filled them in*/
700
701 unsigned lodepng_add_itext(LodePNGInfo* info, const char* key, const char* langtag,
702 const char* transkey, const char* str); /*push back the 4 texts of 1 chunk at once*/
703 void lodepng_clear_itext(LodePNGInfo* info); /*use this to clear the itexts again after you filled them in*/
704
705 /*replaces if exists*/
706 unsigned lodepng_set_icc(LodePNGInfo* info, const char* name, const unsigned char* profile, unsigned profile_size);
707 void lodepng_clear_icc(LodePNGInfo* info); /*use this to clear the texts again after you filled them in*/
708 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
709
710 /*
711 Converts raw buffer from one color type to another color type, based on
712 LodePNGColorMode structs to describe the input and output color type.
713 See the reference manual at the end of this header file to see which color conversions are supported.
714 return value = LodePNG error code (0 if all went ok, an error if the conversion isn't supported)
715 The out buffer must have size (w * h * bpp + 7) / 8, where bpp is the bits per pixel
716 of the output color type (lodepng_get_bpp).
717 For < 8 bpp images, there should not be padding bits at the end of scanlines.
718 For 16-bit per channel colors, uses big endian format like PNG does.
719 Return value is LodePNG error code
720 */
721 unsigned lodepng_convert(unsigned char* out, const unsigned char* in,
722 const LodePNGColorMode* mode_out, const LodePNGColorMode* mode_in,
723 unsigned w, unsigned h);
724
725 #ifdef LODEPNG_COMPILE_DECODER
726 /*
727 Settings for the decoder. This contains settings for the PNG and the Zlib
728 decoder, but not the Info settings from the Info structs.
729 */
730 typedef struct LodePNGDecoderSettings {
731 LodePNGDecompressSettings zlibsettings; /*in here is the setting to ignore Adler32 checksums*/
732
733 /* Check LodePNGDecompressSettings for more ignorable errors such as ignore_adler32 */
734 unsigned ignore_crc; /*ignore CRC checksums*/
735 unsigned ignore_critical; /*ignore unknown critical chunks*/
736 unsigned ignore_end; /*ignore issues at end of file if possible (missing IEND chunk, too large chunk, ...)*/
737 /* TODO: make a system involving warnings with levels and a strict mode instead. Other potentially recoverable
738 errors: srgb rendering intent value, size of content of ancillary chunks, more than 79 characters for some
739 strings, placement/combination rules for ancillary chunks, crc of unknown chunks, allowed characters
740 in string keys, etc... */
741
742 unsigned color_convert; /*whether to convert the PNG to the color type you want. Default: yes*/
743
744 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
745 unsigned read_text_chunks; /*if false but remember_unknown_chunks is true, they're stored in the unknown chunks*/
746
747 /*store all bytes from unknown chunks in the LodePNGInfo (off by default, useful for a png editor)*/
748 unsigned remember_unknown_chunks;
749
750 /* maximum size for decompressed text chunks. If a text chunk's text is larger than this, an error is returned,
751 unless reading text chunks is disabled or this limit is set higher or disabled. Set to 0 to allow any size.
752 By default it is a value that prevents unreasonably large strings from hogging memory. */
753 size_t max_text_size;
754
755 /* maximum size for compressed ICC chunks. If the ICC profile is larger than this, an error will be returned. Set to
756 0 to allow any size. By default this is a value that prevents ICC profiles that would be much larger than any
757 legitimate profile could be to hog memory. */
758 size_t max_icc_size;
759 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
760 } LodePNGDecoderSettings;
761
762 void lodepng_decoder_settings_init(LodePNGDecoderSettings* settings);
763 #endif /*LODEPNG_COMPILE_DECODER*/
764
765 #ifdef LODEPNG_COMPILE_ENCODER
766 /*automatically use color type with less bits per pixel if losslessly possible. Default: AUTO*/
767 typedef enum LodePNGFilterStrategy {
768 /*every filter at zero*/
769 LFS_ZERO = 0,
770 /*every filter at 1, 2, 3 or 4 (paeth), unlike LFS_ZERO not a good choice, but for testing*/
771 LFS_ONE = 1,
772 LFS_TWO = 2,
773 LFS_THREE = 3,
774 LFS_FOUR = 4,
775 /*Use filter that gives minimum sum, as described in the official PNG filter heuristic.*/
776 LFS_MINSUM,
777 /*Use the filter type that gives smallest Shannon entropy for this scanline. Depending
778 on the image, this is better or worse than minsum.*/
779 LFS_ENTROPY,
780 /*
781 Brute-force-search PNG filters by compressing each filter for each scanline.
782 Experimental, very slow, and only rarely gives better compression than MINSUM.
783 */
784 LFS_BRUTE_FORCE,
785 /*use predefined_filters buffer: you specify the filter type for each scanline*/
786 LFS_PREDEFINED
787 } LodePNGFilterStrategy;
788
789 /*Gives characteristics about the integer RGBA colors of the image (count, alpha channel usage, bit depth, ...),
790 which helps decide which color model to use for encoding.
791 Used internally by default if "auto_convert" is enabled. Public because it's useful for custom algorithms.*/
792 typedef struct LodePNGColorStats {
793 unsigned colored; /*not grayscale*/
794 unsigned key; /*image is not opaque and color key is possible instead of full alpha*/
795 unsigned short key_r; /*key values, always as 16-bit, in 8-bit case the byte is duplicated, e.g. 65535 means 255*/
796 unsigned short key_g;
797 unsigned short key_b;
798 unsigned alpha; /*image is not opaque and alpha channel or alpha palette required*/
799 unsigned numcolors; /*amount of colors, up to 257. Not valid if bits == 16 or allow_palette is disabled.*/
800 unsigned char palette[1024]; /*Remembers up to the first 256 RGBA colors, in no particular order, only valid when numcolors is valid*/
801 unsigned bits; /*bits per channel (not for palette). 1,2 or 4 for grayscale only. 16 if 16-bit per channel required.*/
802 size_t numpixels;
803
804 /*user settings for computing/using the stats*/
805 unsigned allow_palette; /*default 1. if 0, disallow choosing palette colortype in auto_choose_color, and don't count numcolors*/
806 unsigned allow_greyscale; /*default 1. if 0, choose RGB or RGBA even if the image only has gray colors*/
807 } LodePNGColorStats;
808
809 void lodepng_color_stats_init(LodePNGColorStats* stats);
810
811 /*Get a LodePNGColorStats of the image. The stats must already have been inited.
812 Returns error code (e.g. alloc fail) or 0 if ok.*/
813 unsigned lodepng_compute_color_stats(LodePNGColorStats* stats,
814 const unsigned char* image, unsigned w, unsigned h,
815 const LodePNGColorMode* mode_in);
816
817 /*Settings for the encoder.*/
818 typedef struct LodePNGEncoderSettings {
819 LodePNGCompressSettings zlibsettings; /*settings for the zlib encoder, such as window size, ...*/
820
821 unsigned auto_convert; /*automatically choose output PNG color type. Default: true*/
822
823 /*If true, follows the official PNG heuristic: if the PNG uses a palette or lower than
824 8 bit depth, set all filters to zero. Otherwise use the filter_strategy. Note that to
825 completely follow the official PNG heuristic, filter_palette_zero must be true and
826 filter_strategy must be LFS_MINSUM*/
827 unsigned filter_palette_zero;
828 /*Which filter strategy to use when not using zeroes due to filter_palette_zero.
829 Set filter_palette_zero to 0 to ensure always using your chosen strategy. Default: LFS_MINSUM*/
830 LodePNGFilterStrategy filter_strategy;
831 /*used if filter_strategy is LFS_PREDEFINED. In that case, this must point to a buffer with
832 the same length as the amount of scanlines in the image, and each value must <= 5. You
833 have to cleanup this buffer, LodePNG will never free it. Don't forget that filter_palette_zero
834 must be set to 0 to ensure this is also used on palette or low bitdepth images.*/
835 const unsigned char* predefined_filters;
836
837 /*force creating a PLTE chunk if colortype is 2 or 6 (= a suggested palette).
838 If colortype is 3, PLTE is always created. If color type is explicitely set
839 to a grayscale type (1 or 4), this is not done and is ignored. If enabling this,
840 a palette must be present in the info_png.
841 NOTE: enabling this may worsen compression if auto_convert is used to choose
842 optimal color mode, because it cannot use grayscale color modes in this case*/
843 unsigned force_palette;
844 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
845 /*add LodePNG identifier and version as a text chunk, for debugging*/
846 unsigned add_id;
847 /*encode text chunks as zTXt chunks instead of tEXt chunks, and use compression in iTXt chunks*/
848 unsigned text_compression;
849 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
850 } LodePNGEncoderSettings;
851
852 void lodepng_encoder_settings_init(LodePNGEncoderSettings* settings);
853 #endif /*LODEPNG_COMPILE_ENCODER*/
854
855
856 #if defined(LODEPNG_COMPILE_DECODER) || defined(LODEPNG_COMPILE_ENCODER)
857 /*The settings, state and information for extended encoding and decoding.*/
858 typedef struct LodePNGState {
859 #ifdef LODEPNG_COMPILE_DECODER
860 LodePNGDecoderSettings decoder; /*the decoding settings*/
861 #endif /*LODEPNG_COMPILE_DECODER*/
862 #ifdef LODEPNG_COMPILE_ENCODER
863 LodePNGEncoderSettings encoder; /*the encoding settings*/
864 #endif /*LODEPNG_COMPILE_ENCODER*/
865 LodePNGColorMode info_raw; /*specifies the format in which you would like to get the raw pixel buffer*/
866 LodePNGInfo info_png; /*info of the PNG image obtained after decoding*/
867 unsigned error;
868 } LodePNGState;
869
870 /*init, cleanup and copy functions to use with this struct*/
871 void lodepng_state_init(LodePNGState* state);
872 void lodepng_state_cleanup(LodePNGState* state);
873 void lodepng_state_copy(LodePNGState* dest, const LodePNGState* source);
874 #endif /* defined(LODEPNG_COMPILE_DECODER) || defined(LODEPNG_COMPILE_ENCODER) */
875
876 #ifdef LODEPNG_COMPILE_DECODER
877 /*
878 Same as lodepng_decode_memory, but uses a LodePNGState to allow custom settings and
879 getting much more information about the PNG image and color mode.
880 */
881 unsigned lodepng_decode(unsigned char** out, unsigned* w, unsigned* h,
882 LodePNGState* state,
883 const unsigned char* in, size_t insize);
884
885 /*
886 Read the PNG header, but not the actual data. This returns only the information
887 that is in the IHDR chunk of the PNG, such as width, height and color type. The
888 information is placed in the info_png field of the LodePNGState.
889 */
890 unsigned lodepng_inspect(unsigned* w, unsigned* h,
891 LodePNGState* state,
892 const unsigned char* in, size_t insize);
893 #endif /*LODEPNG_COMPILE_DECODER*/
894
895 /*
896 Reads one metadata chunk (other than IHDR, which is handled by lodepng_inspect)
897 of the PNG file and outputs what it read in the state. Returns error code on failure.
898 Use lodepng_inspect first with a new state, then e.g. lodepng_chunk_find_const
899 to find the desired chunk type, and if non null use lodepng_inspect_chunk (with
900 chunk_pointer - start_of_file as pos).
901 Supports most metadata chunks from the PNG standard (gAMA, bKGD, tEXt, ...).
902 Ignores unsupported, unknown, non-metadata or IHDR chunks (without error).
903 Requirements: &in[pos] must point to start of a chunk, must use regular
904 lodepng_inspect first since format of most other chunks depends on IHDR, and if
905 there is a PLTE chunk, that one must be inspected before tRNS or bKGD.
906 */
907 unsigned lodepng_inspect_chunk(LodePNGState* state, size_t pos,
908 const unsigned char* in, size_t insize);
909
910 #ifdef LODEPNG_COMPILE_ENCODER
911 /*This function allocates the out buffer with standard malloc and stores the size in *outsize.*/
912 unsigned lodepng_encode(unsigned char** out, size_t* outsize,
913 const unsigned char* image, unsigned w, unsigned h,
914 LodePNGState* state);
915 #endif /*LODEPNG_COMPILE_ENCODER*/
916
917 /*
918 The lodepng_chunk functions are normally not needed, except to traverse the
919 unknown chunks stored in the LodePNGInfo struct, or add new ones to it.
920 It also allows traversing the chunks of an encoded PNG file yourself.
921
922 The chunk pointer always points to the beginning of the chunk itself, that is
923 the first byte of the 4 length bytes.
924
925 In the PNG file format, chunks have the following format:
926 -4 bytes length: length of the data of the chunk in bytes (chunk itself is 12 bytes longer)
927 -4 bytes chunk type (ASCII a-z,A-Z only, see below)
928 -length bytes of data (may be 0 bytes if length was 0)
929 -4 bytes of CRC, computed on chunk name + data
930
931 The first chunk starts at the 8th byte of the PNG file, the entire rest of the file
932 exists out of concatenated chunks with the above format.
933
934 PNG standard chunk ASCII naming conventions:
935 -First byte: uppercase = critical, lowercase = ancillary
936 -Second byte: uppercase = public, lowercase = private
937 -Third byte: must be uppercase
938 -Fourth byte: uppercase = unsafe to copy, lowercase = safe to copy
939 */
940
941 /*
942 Gets the length of the data of the chunk. Total chunk length has 12 bytes more.
943 There must be at least 4 bytes to read from. If the result value is too large,
944 it may be corrupt data.
945 */
946 unsigned lodepng_chunk_length(const unsigned char* chunk);
947
948 /*puts the 4-byte type in null terminated string*/
949 void lodepng_chunk_type(char type[5], const unsigned char* chunk);
950
951 /*check if the type is the given type*/
952 unsigned char lodepng_chunk_type_equals(const unsigned char* chunk, const char* type);
953
954 /*0: it's one of the critical chunk types, 1: it's an ancillary chunk (see PNG standard)*/
955 unsigned char lodepng_chunk_ancillary(const unsigned char* chunk);
956
957 /*0: public, 1: private (see PNG standard)*/
958 unsigned char lodepng_chunk_private(const unsigned char* chunk);
959
960 /*0: the chunk is unsafe to copy, 1: the chunk is safe to copy (see PNG standard)*/
961 unsigned char lodepng_chunk_safetocopy(const unsigned char* chunk);
962
963 /*get pointer to the data of the chunk, where the input points to the header of the chunk*/
964 unsigned char* lodepng_chunk_data(unsigned char* chunk);
965 const unsigned char* lodepng_chunk_data_const(const unsigned char* chunk);
966
967 /*returns 0 if the crc is correct, 1 if it's incorrect (0 for OK as usual!)*/
968 unsigned lodepng_chunk_check_crc(const unsigned char* chunk);
969
970 /*generates the correct CRC from the data and puts it in the last 4 bytes of the chunk*/
971 void lodepng_chunk_generate_crc(unsigned char* chunk);
972
973 /*
974 Iterate to next chunks, allows iterating through all chunks of the PNG file.
975 Input must be at the beginning of a chunk (result of a previous lodepng_chunk_next call,
976 or the 8th byte of a PNG file which always has the first chunk), or alternatively may
977 point to the first byte of the PNG file (which is not a chunk but the magic header, the
978 function will then skip over it and return the first real chunk).
979 Will output pointer to the start of the next chunk, or at or beyond end of the file if there
980 is no more chunk after this or possibly if the chunk is corrupt.
981 Start this process at the 8th byte of the PNG file.
982 In a non-corrupt PNG file, the last chunk should have name "IEND".
983 */
984 unsigned char* lodepng_chunk_next(unsigned char* chunk, unsigned char* end);
985 const unsigned char* lodepng_chunk_next_const(const unsigned char* chunk, const unsigned char* end);
986
987 /*Finds the first chunk with the given type in the range [chunk, end), or returns NULL if not found.*/
988 unsigned char* lodepng_chunk_find(unsigned char* chunk, unsigned char* end, const char type[5]);
989 const unsigned char* lodepng_chunk_find_const(const unsigned char* chunk, const unsigned char* end, const char type[5]);
990
991 /*
992 Appends chunk to the data in out. The given chunk should already have its chunk header.
993 The out variable and outsize are updated to reflect the new reallocated buffer.
994 Returns error code (0 if it went ok)
995 */
996 unsigned lodepng_chunk_append(unsigned char** out, size_t* outsize, const unsigned char* chunk);
997
998 /*
999 Appends new chunk to out. The chunk to append is given by giving its length, type
1000 and data separately. The type is a 4-letter string.
1001 The out variable and outsize are updated to reflect the new reallocated buffer.
1002 Returne error code (0 if it went ok)
1003 */
1004 unsigned lodepng_chunk_create(unsigned char** out, size_t* outsize, unsigned length,
1005 const char* type, const unsigned char* data);
1006
1007
1008 /*Calculate CRC32 of buffer*/
1009 unsigned lodepng_crc32(const unsigned char* buf, size_t len);
1010 #endif /*LODEPNG_COMPILE_PNG*/
1011
1012
1013 #ifdef LODEPNG_COMPILE_ZLIB
1014 /*
1015 This zlib part can be used independently to zlib compress and decompress a
1016 buffer. It cannot be used to create gzip files however, and it only supports the
1017 part of zlib that is required for PNG, it does not support dictionaries.
1018 */
1019
1020 #ifdef LODEPNG_COMPILE_DECODER
1021 /*Inflate a buffer. Inflate is the decompression step of deflate. Out buffer must be freed after use.*/
1022 unsigned lodepng_inflate(unsigned char** out, size_t* outsize,
1023 const unsigned char* in, size_t insize,
1024 const LodePNGDecompressSettings* settings);
1025
1026 /*
1027 Decompresses Zlib data. Reallocates the out buffer and appends the data. The
1028 data must be according to the zlib specification.
1029 Either, *out must be NULL and *outsize must be 0, or, *out must be a valid
1030 buffer and *outsize its size in bytes. out must be freed by user after usage.
1031 */
1032 unsigned lodepng_zlib_decompress(unsigned char** out, size_t* outsize,
1033 const unsigned char* in, size_t insize,
1034 const LodePNGDecompressSettings* settings);
1035 #endif /*LODEPNG_COMPILE_DECODER*/
1036
1037 #ifdef LODEPNG_COMPILE_ENCODER
1038 /*
1039 Compresses data with Zlib. Reallocates the out buffer and appends the data.
1040 Zlib adds a small header and trailer around the deflate data.
1041 The data is output in the format of the zlib specification.
1042 Either, *out must be NULL and *outsize must be 0, or, *out must be a valid
1043 buffer and *outsize its size in bytes. out must be freed by user after usage.
1044 */
1045 unsigned lodepng_zlib_compress(unsigned char** out, size_t* outsize,
1046 const unsigned char* in, size_t insize,
1047 const LodePNGCompressSettings* settings);
1048
1049 /*
1050 Find length-limited Huffman code for given frequencies. This function is in the
1051 public interface only for tests, it's used internally by lodepng_deflate.
1052 */
1053 unsigned lodepng_huffman_code_lengths(unsigned* lengths, const unsigned* frequencies,
1054 size_t numcodes, unsigned maxbitlen);
1055
1056 /*Compress a buffer with deflate. See RFC 1951. Out buffer must be freed after use.*/
1057 unsigned lodepng_deflate(unsigned char** out, size_t* outsize,
1058 const unsigned char* in, size_t insize,
1059 const LodePNGCompressSettings* settings);
1060
1061 #endif /*LODEPNG_COMPILE_ENCODER*/
1062 #endif /*LODEPNG_COMPILE_ZLIB*/
1063
1064 #ifdef LODEPNG_COMPILE_DISK
1065 /*
1066 Load a file from disk into buffer. The function allocates the out buffer, and
1067 after usage you should free it.
1068 out: output parameter, contains pointer to loaded buffer.
1069 outsize: output parameter, size of the allocated out buffer
1070 filename: the path to the file to load
1071 return value: error code (0 means ok)
1072
1073 NOTE: Wide-character filenames are not supported, you can use an external method
1074 to handle such files and decode in-memory.
1075 */
1076 unsigned lodepng_load_file(unsigned char** out, size_t* outsize, const char* filename);
1077
1078 /*
1079 Save a file from buffer to disk. Warning, if it exists, this function overwrites
1080 the file without warning!
1081 buffer: the buffer to write
1082 buffersize: size of the buffer to write
1083 filename: the path to the file to save to
1084 return value: error code (0 means ok)
1085
1086 NOTE: Wide-character filenames are not supported, you can use an external method
1087 to handle such files and encode in-memory
1088 */
1089 unsigned lodepng_save_file(const unsigned char* buffer, size_t buffersize, const char* filename);
1090 #endif /*LODEPNG_COMPILE_DISK*/
1091
1092 #ifdef LODEPNG_COMPILE_CPP
1093 /* The LodePNG C++ wrapper uses std::vectors instead of manually allocated memory buffers. */
1094 namespace lodepng {
1095 #ifdef LODEPNG_COMPILE_PNG
1096 class State : public LodePNGState {
1097 public:
1098 State();
1099 State(const State& other);
1100 ~State();
1101 State& operator=(const State& other);
1102 };
1103
1104 #ifdef LODEPNG_COMPILE_DECODER
1105 /* Same as other lodepng::decode, but using a State for more settings and information. */
1106 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
1107 State& state,
1108 const unsigned char* in, size_t insize);
1109 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
1110 State& state,
1111 const std::vector<unsigned char>& in);
1112 #endif /*LODEPNG_COMPILE_DECODER*/
1113
1114 #ifdef LODEPNG_COMPILE_ENCODER
1115 /* Same as other lodepng::encode, but using a State for more settings and information. */
1116 unsigned encode(std::vector<unsigned char>& out,
1117 const unsigned char* in, unsigned w, unsigned h,
1118 State& state);
1119 unsigned encode(std::vector<unsigned char>& out,
1120 const std::vector<unsigned char>& in, unsigned w, unsigned h,
1121 State& state);
1122 #endif /*LODEPNG_COMPILE_ENCODER*/
1123
1124 #ifdef LODEPNG_COMPILE_DISK
1125 /*
1126 Load a file from disk into an std::vector.
1127 return value: error code (0 means ok)
1128
1129 NOTE: Wide-character filenames are not supported, you can use an external method
1130 to handle such files and decode in-memory
1131 */
1132 unsigned load_file(std::vector<unsigned char>& buffer, const std::string& filename);
1133
1134 /*
1135 Save the binary data in an std::vector to a file on disk. The file is overwritten
1136 without warning.
1137
1138 NOTE: Wide-character filenames are not supported, you can use an external method
1139 to handle such files and encode in-memory
1140 */
1141 unsigned save_file(const std::vector<unsigned char>& buffer, const std::string& filename);
1142 #endif /* LODEPNG_COMPILE_DISK */
1143 #endif /* LODEPNG_COMPILE_PNG */
1144
1145 #ifdef LODEPNG_COMPILE_ZLIB
1146 #ifdef LODEPNG_COMPILE_DECODER
1147 /* Zlib-decompress an unsigned char buffer */
1148 unsigned decompress(std::vector<unsigned char>& out, const unsigned char* in, size_t insize,
1149 const LodePNGDecompressSettings& settings = lodepng_default_decompress_settings);
1150
1151 /* Zlib-decompress an std::vector */
1152 unsigned decompress(std::vector<unsigned char>& out, const std::vector<unsigned char>& in,
1153 const LodePNGDecompressSettings& settings = lodepng_default_decompress_settings);
1154 #endif /* LODEPNG_COMPILE_DECODER */
1155
1156 #ifdef LODEPNG_COMPILE_ENCODER
1157 /* Zlib-compress an unsigned char buffer */
1158 unsigned compress(std::vector<unsigned char>& out, const unsigned char* in, size_t insize,
1159 const LodePNGCompressSettings& settings = lodepng_default_compress_settings);
1160
1161 /* Zlib-compress an std::vector */
1162 unsigned compress(std::vector<unsigned char>& out, const std::vector<unsigned char>& in,
1163 const LodePNGCompressSettings& settings = lodepng_default_compress_settings);
1164 #endif /* LODEPNG_COMPILE_ENCODER */
1165 #endif /* LODEPNG_COMPILE_ZLIB */
1166 } /* namespace lodepng */
1167 #endif /*LODEPNG_COMPILE_CPP*/
1168
1169 /*
1170 TODO:
1171 [.] test if there are no memory leaks or security exploits - done a lot but needs to be checked often
1172 [.] check compatibility with various compilers - done but needs to be redone for every newer version
1173 [X] converting color to 16-bit per channel types
1174 [X] support color profile chunk types (but never let them touch RGB values by default)
1175 [ ] support all public PNG chunk types (almost done except sPLT and hIST)
1176 [ ] make sure encoder generates no chunks with size > (2^31)-1
1177 [ ] partial decoding (stream processing)
1178 [X] let the "isFullyOpaque" function check color keys and transparent palettes too
1179 [X] better name for the variables "codes", "codesD", "codelengthcodes", "clcl" and "lldl"
1180 [ ] allow treating some errors like warnings, when image is recoverable (e.g. 69, 57, 58)
1181 [ ] make warnings like: oob palette, checksum fail, data after iend, wrong/unknown crit chunk, no null terminator in text, ...
1182 [ ] error messages with line numbers (and version)
1183 [ ] errors in state instead of as return code?
1184 [ ] new errors/warnings like suspiciously big decompressed ztxt or iccp chunk
1185 [ ] let the C++ wrapper catch exceptions coming from the standard library and return LodePNG error codes
1186 [ ] allow user to provide custom color conversion functions, e.g. for premultiplied alpha, padding bits or not, ...
1187 [ ] allow user to give data (void*) to custom allocator
1188 [X] provide alternatives for C library functions not present on some platforms (memcpy, ...)
1189 */
1190
1191 #endif /*LODEPNG_H inclusion guard*/
1192
1193 /*
1194 LodePNG Documentation
1195 ---------------------
1196
1197 0. table of contents
1198 --------------------
1199
1200 1. about
1201 1.1. supported features
1202 1.2. features not supported
1203 2. C and C++ version
1204 3. security
1205 4. decoding
1206 5. encoding
1207 6. color conversions
1208 6.1. PNG color types
1209 6.2. color conversions
1210 6.3. padding bits
1211 6.4. A note about 16-bits per channel and endianness
1212 7. error values
1213 8. chunks and PNG editing
1214 9. compiler support
1215 10. examples
1216 10.1. decoder C++ example
1217 10.2. decoder C example
1218 11. state settings reference
1219 12. changes
1220 13. contact information
1221
1222
1223 1. about
1224 --------
1225
1226 PNG is a file format to store raster images losslessly with good compression,
1227 supporting different color types and alpha channel.
1228
1229 LodePNG is a PNG codec according to the Portable Network Graphics (PNG)
1230 Specification (Second Edition) - W3C Recommendation 10 November 2003.
1231
1232 The specifications used are:
1233
1234 *) Portable Network Graphics (PNG) Specification (Second Edition):
1235 http://www.w3.org/TR/2003/REC-PNG-20031110
1236 *) RFC 1950 ZLIB Compressed Data Format version 3.3:
1237 http://www.gzip.org/zlib/rfc-zlib.html
1238 *) RFC 1951 DEFLATE Compressed Data Format Specification ver 1.3:
1239 http://www.gzip.org/zlib/rfc-deflate.html
1240
1241 The most recent version of LodePNG can currently be found at
1242 http://lodev.org/lodepng/
1243
1244 LodePNG works both in C (ISO C90) and C++, with a C++ wrapper that adds
1245 extra functionality.
1246
1247 LodePNG exists out of two files:
1248 -lodepng.h: the header file for both C and C++
1249 -lodepng.c(pp): give it the name lodepng.c or lodepng.cpp (or .cc) depending on your usage
1250
1251 If you want to start using LodePNG right away without reading this doc, get the
1252 examples from the LodePNG website to see how to use it in code, or check the
1253 smaller examples in chapter 13 here.
1254
1255 LodePNG is simple but only supports the basic requirements. To achieve
1256 simplicity, the following design choices were made: There are no dependencies
1257 on any external library. There are functions to decode and encode a PNG with
1258 a single function call, and extended versions of these functions taking a
1259 LodePNGState struct allowing to specify or get more information. By default
1260 the colors of the raw image are always RGB or RGBA, no matter what color type
1261 the PNG file uses. To read and write files, there are simple functions to
1262 convert the files to/from buffers in memory.
1263
1264 This all makes LodePNG suitable for loading textures in games, demos and small
1265 programs, ... It's less suitable for full fledged image editors, loading PNGs
1266 over network (it requires all the image data to be available before decoding can
1267 begin), life-critical systems, ...
1268
1269 1.1. supported features
1270 -----------------------
1271
1272 The following features are supported by the decoder:
1273
1274 *) decoding of PNGs with any color type, bit depth and interlace mode, to a 24- or 32-bit color raw image,
1275 or the same color type as the PNG
1276 *) encoding of PNGs, from any raw image to 24- or 32-bit color, or the same color type as the raw image
1277 *) Adam7 interlace and deinterlace for any color type
1278 *) loading the image from harddisk or decoding it from a buffer from other sources than harddisk
1279 *) support for alpha channels, including RGBA color model, translucent palettes and color keying
1280 *) zlib decompression (inflate)
1281 *) zlib compression (deflate)
1282 *) CRC32 and ADLER32 checksums
1283 *) colorimetric color profile conversions: currently experimentally available in lodepng_util.cpp only,
1284 plus alternatively ability to pass on chroma/gamma/ICC profile information to other color management system.
1285 *) handling of unknown chunks, allowing making a PNG editor that stores custom and unknown chunks.
1286 *) the following chunks are supported by both encoder and decoder:
1287 IHDR: header information
1288 PLTE: color palette
1289 IDAT: pixel data
1290 IEND: the final chunk
1291 tRNS: transparency for palettized images
1292 tEXt: textual information
1293 zTXt: compressed textual information
1294 iTXt: international textual information
1295 bKGD: suggested background color
1296 pHYs: physical dimensions
1297 tIME: modification time
1298 cHRM: RGB chromaticities
1299 gAMA: RGB gamma correction
1300 iCCP: ICC color profile
1301 sRGB: rendering intent
1302 sBIT: significant bits
1303
1304 1.2. features not supported
1305 ---------------------------
1306
1307 The following features are not (yet) supported:
1308
1309 *) some features needed to make a conformant PNG-Editor might be still missing.
1310 *) partial loading/stream processing. All data must be available and is processed in one call.
1311 *) The hIST and sPLT public chunks are not (yet) supported but treated as unknown chunks
1312
1313
1314 2. C and C++ version
1315 --------------------
1316
1317 The C version uses buffers allocated with alloc that you need to free()
1318 yourself. You need to use init and cleanup functions for each struct whenever
1319 using a struct from the C version to avoid exploits and memory leaks.
1320
1321 The C++ version has extra functions with std::vectors in the interface and the
1322 lodepng::State class which is a LodePNGState with constructor and destructor.
1323
1324 These files work without modification for both C and C++ compilers because all
1325 the additional C++ code is in "#ifdef __cplusplus" blocks that make C-compilers
1326 ignore it, and the C code is made to compile both with strict ISO C90 and C++.
1327
1328 To use the C++ version, you need to rename the source file to lodepng.cpp
1329 (instead of lodepng.c), and compile it with a C++ compiler.
1330
1331 To use the C version, you need to rename the source file to lodepng.c (instead
1332 of lodepng.cpp), and compile it with a C compiler.
1333
1334
1335 3. Security
1336 -----------
1337
1338 Even if carefully designed, it's always possible that LodePNG contains possible
1339 exploits. If you discover one, please let me know, and it will be fixed.
1340
1341 When using LodePNG, care has to be taken with the C version of LodePNG, as well
1342 as the C-style structs when working with C++. The following conventions are used
1343 for all C-style structs:
1344
1345 -if a struct has a corresponding init function, always call the init function when making a new one
1346 -if a struct has a corresponding cleanup function, call it before the struct disappears to avoid memory leaks
1347 -if a struct has a corresponding copy function, use the copy function instead of "=".
1348 The destination must also be inited already.
1349
1350
1351 4. Decoding
1352 -----------
1353
1354 Decoding converts a PNG compressed image to a raw pixel buffer.
1355
1356 Most documentation on using the decoder is at its declarations in the header
1357 above. For C, simple decoding can be done with functions such as
1358 lodepng_decode32, and more advanced decoding can be done with the struct
1359 LodePNGState and lodepng_decode. For C++, all decoding can be done with the
1360 various lodepng::decode functions, and lodepng::State can be used for advanced
1361 features.
1362
1363 When using the LodePNGState, it uses the following fields for decoding:
1364 *) LodePNGInfo info_png: it stores extra information about the PNG (the input) in here
1365 *) LodePNGColorMode info_raw: here you can say what color mode of the raw image (the output) you want to get
1366 *) LodePNGDecoderSettings decoder: you can specify a few extra settings for the decoder to use
1367
1368 LodePNGInfo info_png
1369 --------------------
1370
1371 After decoding, this contains extra information of the PNG image, except the actual
1372 pixels, width and height because these are already gotten directly from the decoder
1373 functions.
1374
1375 It contains for example the original color type of the PNG image, text comments,
1376 suggested background color, etc... More details about the LodePNGInfo struct are
1377 at its declaration documentation.
1378
1379 LodePNGColorMode info_raw
1380 -------------------------
1381
1382 When decoding, here you can specify which color type you want
1383 the resulting raw image to be. If this is different from the colortype of the
1384 PNG, then the decoder will automatically convert the result. This conversion
1385 always works, except if you want it to convert a color PNG to grayscale or to
1386 a palette with missing colors.
1387
1388 By default, 32-bit color is used for the result.
1389
1390 LodePNGDecoderSettings decoder
1391 ------------------------------
1392
1393 The settings can be used to ignore the errors created by invalid CRC and Adler32
1394 chunks, and to disable the decoding of tEXt chunks.
1395
1396 There's also a setting color_convert, true by default. If false, no conversion
1397 is done, the resulting data will be as it was in the PNG (after decompression)
1398 and you'll have to puzzle the colors of the pixels together yourself using the
1399 color type information in the LodePNGInfo.
1400
1401
1402 5. Encoding
1403 -----------
1404
1405 Encoding converts a raw pixel buffer to a PNG compressed image.
1406
1407 Most documentation on using the encoder is at its declarations in the header
1408 above. For C, simple encoding can be done with functions such as
1409 lodepng_encode32, and more advanced decoding can be done with the struct
1410 LodePNGState and lodepng_encode. For C++, all encoding can be done with the
1411 various lodepng::encode functions, and lodepng::State can be used for advanced
1412 features.
1413
1414 Like the decoder, the encoder can also give errors. However it gives less errors
1415 since the encoder input is trusted, the decoder input (a PNG image that could
1416 be forged by anyone) is not trusted.
1417
1418 When using the LodePNGState, it uses the following fields for encoding:
1419 *) LodePNGInfo info_png: here you specify how you want the PNG (the output) to be.
1420 *) LodePNGColorMode info_raw: here you say what color type of the raw image (the input) has
1421 *) LodePNGEncoderSettings encoder: you can specify a few settings for the encoder to use
1422
1423 LodePNGInfo info_png
1424 --------------------
1425
1426 When encoding, you use this the opposite way as when decoding: for encoding,
1427 you fill in the values you want the PNG to have before encoding. By default it's
1428 not needed to specify a color type for the PNG since it's automatically chosen,
1429 but it's possible to choose it yourself given the right settings.
1430
1431 The encoder will not always exactly match the LodePNGInfo struct you give,
1432 it tries as close as possible. Some things are ignored by the encoder. The
1433 encoder uses, for example, the following settings from it when applicable:
1434 colortype and bitdepth, text chunks, time chunk, the color key, the palette, the
1435 background color, the interlace method, unknown chunks, ...
1436
1437 When encoding to a PNG with colortype 3, the encoder will generate a PLTE chunk.
1438 If the palette contains any colors for which the alpha channel is not 255 (so
1439 there are translucent colors in the palette), it'll add a tRNS chunk.
1440
1441 LodePNGColorMode info_raw
1442 -------------------------
1443
1444 You specify the color type of the raw image that you give to the input here,
1445 including a possible transparent color key and palette you happen to be using in
1446 your raw image data.
1447
1448 By default, 32-bit color is assumed, meaning your input has to be in RGBA
1449 format with 4 bytes (unsigned chars) per pixel.
1450
1451 LodePNGEncoderSettings encoder
1452 ------------------------------
1453
1454 The following settings are supported (some are in sub-structs):
1455 *) auto_convert: when this option is enabled, the encoder will
1456 automatically choose the smallest possible color mode (including color key) that
1457 can encode the colors of all pixels without information loss.
1458 *) btype: the block type for LZ77. 0 = uncompressed, 1 = fixed huffman tree,
1459 2 = dynamic huffman tree (best compression). Should be 2 for proper
1460 compression.
1461 *) use_lz77: whether or not to use LZ77 for compressed block types. Should be
1462 true for proper compression.
1463 *) windowsize: the window size used by the LZ77 encoder (1 - 32768). Has value
1464 2048 by default, but can be set to 32768 for better, but slow, compression.
1465 *) force_palette: if colortype is 2 or 6, you can make the encoder write a PLTE
1466 chunk if force_palette is true. This can used as suggested palette to convert
1467 to by viewers that don't support more than 256 colors (if those still exist)
1468 *) add_id: add text chunk "Encoder: LodePNG <version>" to the image.
1469 *) text_compression: default 1. If 1, it'll store texts as zTXt instead of tEXt chunks.
1470 zTXt chunks use zlib compression on the text. This gives a smaller result on
1471 large texts but a larger result on small texts (such as a single program name).
1472 It's all tEXt or all zTXt though, there's no separate setting per text yet.
1473
1474
1475 6. color conversions
1476 --------------------
1477
1478 An important thing to note about LodePNG, is that the color type of the PNG, and
1479 the color type of the raw image, are completely independent. By default, when
1480 you decode a PNG, you get the result as a raw image in the color type you want,
1481 no matter whether the PNG was encoded with a palette, grayscale or RGBA color.
1482 And if you encode an image, by default LodePNG will automatically choose the PNG
1483 color type that gives good compression based on the values of colors and amount
1484 of colors in the image. It can be configured to let you control it instead as
1485 well, though.
1486
1487 To be able to do this, LodePNG does conversions from one color mode to another.
1488 It can convert from almost any color type to any other color type, except the
1489 following conversions: RGB to grayscale is not supported, and converting to a
1490 palette when the palette doesn't have a required color is not supported. This is
1491 not supported on purpose: this is information loss which requires a color
1492 reduction algorithm that is beyond the scope of a PNG encoder (yes, RGB to gray
1493 is easy, but there are multiple ways if you want to give some channels more
1494 weight).
1495
1496 By default, when decoding, you get the raw image in 32-bit RGBA or 24-bit RGB
1497 color, no matter what color type the PNG has. And by default when encoding,
1498 LodePNG automatically picks the best color model for the output PNG, and expects
1499 the input image to be 32-bit RGBA or 24-bit RGB. So, unless you want to control
1500 the color format of the images yourself, you can skip this chapter.
1501
1502 6.1. PNG color types
1503 --------------------
1504
1505 A PNG image can have many color types, ranging from 1-bit color to 64-bit color,
1506 as well as palettized color modes. After the zlib decompression and unfiltering
1507 in the PNG image is done, the raw pixel data will have that color type and thus
1508 a certain amount of bits per pixel. If you want the output raw image after
1509 decoding to have another color type, a conversion is done by LodePNG.
1510
1511 The PNG specification gives the following color types:
1512
1513 0: grayscale, bit depths 1, 2, 4, 8, 16
1514 2: RGB, bit depths 8 and 16
1515 3: palette, bit depths 1, 2, 4 and 8
1516 4: grayscale with alpha, bit depths 8 and 16
1517 6: RGBA, bit depths 8 and 16
1518
1519 Bit depth is the amount of bits per pixel per color channel. So the total amount
1520 of bits per pixel is: amount of channels * bitdepth.
1521
1522 6.2. color conversions
1523 ----------------------
1524
1525 As explained in the sections about the encoder and decoder, you can specify
1526 color types and bit depths in info_png and info_raw to change the default
1527 behaviour.
1528
1529 If, when decoding, you want the raw image to be something else than the default,
1530 you need to set the color type and bit depth you want in the LodePNGColorMode,
1531 or the parameters colortype and bitdepth of the simple decoding function.
1532
1533 If, when encoding, you use another color type than the default in the raw input
1534 image, you need to specify its color type and bit depth in the LodePNGColorMode
1535 of the raw image, or use the parameters colortype and bitdepth of the simple
1536 encoding function.
1537
1538 If, when encoding, you don't want LodePNG to choose the output PNG color type
1539 but control it yourself, you need to set auto_convert in the encoder settings
1540 to false, and specify the color type you want in the LodePNGInfo of the
1541 encoder (including palette: it can generate a palette if auto_convert is true,
1542 otherwise not).
1543
1544 If the input and output color type differ (whether user chosen or auto chosen),
1545 LodePNG will do a color conversion, which follows the rules below, and may
1546 sometimes result in an error.
1547
1548 To avoid some confusion:
1549 -the decoder converts from PNG to raw image
1550 -the encoder converts from raw image to PNG
1551 -the colortype and bitdepth in LodePNGColorMode info_raw, are those of the raw image
1552 -the colortype and bitdepth in the color field of LodePNGInfo info_png, are those of the PNG
1553 -when encoding, the color type in LodePNGInfo is ignored if auto_convert
1554 is enabled, it is automatically generated instead
1555 -when decoding, the color type in LodePNGInfo is set by the decoder to that of the original
1556 PNG image, but it can be ignored since the raw image has the color type you requested instead
1557 -if the color type of the LodePNGColorMode and PNG image aren't the same, a conversion
1558 between the color types is done if the color types are supported. If it is not
1559 supported, an error is returned. If the types are the same, no conversion is done.
1560 -even though some conversions aren't supported, LodePNG supports loading PNGs from any
1561 colortype and saving PNGs to any colortype, sometimes it just requires preparing
1562 the raw image correctly before encoding.
1563 -both encoder and decoder use the same color converter.
1564
1565 The function lodepng_convert does the color conversion. It is available in the
1566 interface but normally isn't needed since the encoder and decoder already call
1567 it.
1568
1569 Non supported color conversions:
1570 -color to grayscale when non-gray pixels are present: no error is thrown, but
1571 the result will look ugly because only the red channel is taken (it assumes all
1572 three channels are the same in this case so ignores green and blue). The reason
1573 no error is given is to allow converting from three-channel grayscale images to
1574 one-channel even if there are numerical imprecisions.
1575 -anything to palette when the palette does not have an exact match for a from-color
1576 in it: in this case an error is thrown
1577
1578 Supported color conversions:
1579 -anything to 8-bit RGB, 8-bit RGBA, 16-bit RGB, 16-bit RGBA
1580 -any gray or gray+alpha, to gray or gray+alpha
1581 -anything to a palette, as long as the palette has the requested colors in it
1582 -removing alpha channel
1583 -higher to smaller bitdepth, and vice versa
1584
1585 If you want no color conversion to be done (e.g. for speed or control):
1586 -In the encoder, you can make it save a PNG with any color type by giving the
1587 raw color mode and LodePNGInfo the same color mode, and setting auto_convert to
1588 false.
1589 -In the decoder, you can make it store the pixel data in the same color type
1590 as the PNG has, by setting the color_convert setting to false. Settings in
1591 info_raw are then ignored.
1592
1593 6.3. padding bits
1594 -----------------
1595
1596 In the PNG file format, if a less than 8-bit per pixel color type is used and the scanlines
1597 have a bit amount that isn't a multiple of 8, then padding bits are used so that each
1598 scanline starts at a fresh byte. But that is NOT true for the LodePNG raw input and output.
1599 The raw input image you give to the encoder, and the raw output image you get from the decoder
1600 will NOT have these padding bits, e.g. in the case of a 1-bit image with a width
1601 of 7 pixels, the first pixel of the second scanline will the 8th bit of the first byte,
1602 not the first bit of a new byte.
1603
1604 6.4. A note about 16-bits per channel and endianness
1605 ----------------------------------------------------
1606
1607 LodePNG uses unsigned char arrays for 16-bit per channel colors too, just like
1608 for any other color format. The 16-bit values are stored in big endian (most
1609 significant byte first) in these arrays. This is the opposite order of the
1610 little endian used by x86 CPU's.
1611
1612 LodePNG always uses big endian because the PNG file format does so internally.
1613 Conversions to other formats than PNG uses internally are not supported by
1614 LodePNG on purpose, there are myriads of formats, including endianness of 16-bit
1615 colors, the order in which you store R, G, B and A, and so on. Supporting and
1616 converting to/from all that is outside the scope of LodePNG.
1617
1618 This may mean that, depending on your use case, you may want to convert the big
1619 endian output of LodePNG to little endian with a for loop. This is certainly not
1620 always needed, many applications and libraries support big endian 16-bit colors
1621 anyway, but it means you cannot simply cast the unsigned char* buffer to an
1622 unsigned short* buffer on x86 CPUs.
1623
1624
1625 7. error values
1626 ---------------
1627
1628 All functions in LodePNG that return an error code, return 0 if everything went
1629 OK, or a non-zero code if there was an error.
1630
1631 The meaning of the LodePNG error values can be retrieved with the function
1632 lodepng_error_text: given the numerical error code, it returns a description
1633 of the error in English as a string.
1634
1635 Check the implementation of lodepng_error_text to see the meaning of each code.
1636
1637 It is not recommended to use the numerical values to programmatically make
1638 different decisions based on error types as the numbers are not guaranteed to
1639 stay backwards compatible. They are for human consumption only. Programmatically
1640 only 0 or non-0 matter.
1641
1642
1643 8. chunks and PNG editing
1644 -------------------------
1645
1646 If you want to add extra chunks to a PNG you encode, or use LodePNG for a PNG
1647 editor that should follow the rules about handling of unknown chunks, or if your
1648 program is able to read other types of chunks than the ones handled by LodePNG,
1649 then that's possible with the chunk functions of LodePNG.
1650
1651 A PNG chunk has the following layout:
1652
1653 4 bytes length
1654 4 bytes type name
1655 length bytes data
1656 4 bytes CRC
1657
1658 8.1. iterating through chunks
1659 -----------------------------
1660
1661 If you have a buffer containing the PNG image data, then the first chunk (the
1662 IHDR chunk) starts at byte number 8 of that buffer. The first 8 bytes are the
1663 signature of the PNG and are not part of a chunk. But if you start at byte 8
1664 then you have a chunk, and can check the following things of it.
1665
1666 NOTE: none of these functions check for memory buffer boundaries. To avoid
1667 exploits, always make sure the buffer contains all the data of the chunks.
1668 When using lodepng_chunk_next, make sure the returned value is within the
1669 allocated memory.
1670
1671 unsigned lodepng_chunk_length(const unsigned char* chunk):
1672
1673 Get the length of the chunk's data. The total chunk length is this length + 12.
1674
1675 void lodepng_chunk_type(char type[5], const unsigned char* chunk):
1676 unsigned char lodepng_chunk_type_equals(const unsigned char* chunk, const char* type):
1677
1678 Get the type of the chunk or compare if it's a certain type
1679
1680 unsigned char lodepng_chunk_critical(const unsigned char* chunk):
1681 unsigned char lodepng_chunk_private(const unsigned char* chunk):
1682 unsigned char lodepng_chunk_safetocopy(const unsigned char* chunk):
1683
1684 Check if the chunk is critical in the PNG standard (only IHDR, PLTE, IDAT and IEND are).
1685 Check if the chunk is private (public chunks are part of the standard, private ones not).
1686 Check if the chunk is safe to copy. If it's not, then, when modifying data in a critical
1687 chunk, unsafe to copy chunks of the old image may NOT be saved in the new one if your
1688 program doesn't handle that type of unknown chunk.
1689
1690 unsigned char* lodepng_chunk_data(unsigned char* chunk):
1691 const unsigned char* lodepng_chunk_data_const(const unsigned char* chunk):
1692
1693 Get a pointer to the start of the data of the chunk.
1694
1695 unsigned lodepng_chunk_check_crc(const unsigned char* chunk):
1696 void lodepng_chunk_generate_crc(unsigned char* chunk):
1697
1698 Check if the crc is correct or generate a correct one.
1699
1700 unsigned char* lodepng_chunk_next(unsigned char* chunk):
1701 const unsigned char* lodepng_chunk_next_const(const unsigned char* chunk):
1702
1703 Iterate to the next chunk. This works if you have a buffer with consecutive chunks. Note that these
1704 functions do no boundary checking of the allocated data whatsoever, so make sure there is enough
1705 data available in the buffer to be able to go to the next chunk.
1706
1707 unsigned lodepng_chunk_append(unsigned char** out, size_t* outsize, const unsigned char* chunk):
1708 unsigned lodepng_chunk_create(unsigned char** out, size_t* outsize, unsigned length,
1709 const char* type, const unsigned char* data):
1710
1711 These functions are used to create new chunks that are appended to the data in *out that has
1712 length *outsize. The append function appends an existing chunk to the new data. The create
1713 function creates a new chunk with the given parameters and appends it. Type is the 4-letter
1714 name of the chunk.
1715
1716 8.2. chunks in info_png
1717 -----------------------
1718
1719 The LodePNGInfo struct contains fields with the unknown chunk in it. It has 3
1720 buffers (each with size) to contain 3 types of unknown chunks:
1721 the ones that come before the PLTE chunk, the ones that come between the PLTE
1722 and the IDAT chunks, and the ones that come after the IDAT chunks.
1723 It's necessary to make the distinction between these 3 cases because the PNG
1724 standard forces to keep the ordering of unknown chunks compared to the critical
1725 chunks, but does not force any other ordering rules.
1726
1727 info_png.unknown_chunks_data[0] is the chunks before PLTE
1728 info_png.unknown_chunks_data[1] is the chunks after PLTE, before IDAT
1729 info_png.unknown_chunks_data[2] is the chunks after IDAT
1730
1731 The chunks in these 3 buffers can be iterated through and read by using the same
1732 way described in the previous subchapter.
1733
1734 When using the decoder to decode a PNG, you can make it store all unknown chunks
1735 if you set the option settings.remember_unknown_chunks to 1. By default, this
1736 option is off (0).
1737
1738 The encoder will always encode unknown chunks that are stored in the info_png.
1739 If you need it to add a particular chunk that isn't known by LodePNG, you can
1740 use lodepng_chunk_append or lodepng_chunk_create to the chunk data in
1741 info_png.unknown_chunks_data[x].
1742
1743 Chunks that are known by LodePNG should not be added in that way. E.g. to make
1744 LodePNG add a bKGD chunk, set background_defined to true and add the correct
1745 parameters there instead.
1746
1747
1748 9. compiler support
1749 -------------------
1750
1751 No libraries other than the current standard C library are needed to compile
1752 LodePNG. For the C++ version, only the standard C++ library is needed on top.
1753 Add the files lodepng.c(pp) and lodepng.h to your project, include
1754 lodepng.h where needed, and your program can read/write PNG files.
1755
1756 It is compatible with C90 and up, and C++03 and up.
1757
1758 If performance is important, use optimization when compiling! For both the
1759 encoder and decoder, this makes a large difference.
1760
1761 Make sure that LodePNG is compiled with the same compiler of the same version
1762 and with the same settings as the rest of the program, or the interfaces with
1763 std::vectors and std::strings in C++ can be incompatible.
1764
1765 CHAR_BITS must be 8 or higher, because LodePNG uses unsigned chars for octets.
1766
1767 *) gcc and g++
1768
1769 LodePNG is developed in gcc so this compiler is natively supported. It gives no
1770 warnings with compiler options "-Wall -Wextra -pedantic -ansi", with gcc and g++
1771 version 4.7.1 on Linux, 32-bit and 64-bit.
1772
1773 *) Clang
1774
1775 Fully supported and warning-free.
1776
1777 *) Mingw
1778
1779 The Mingw compiler (a port of gcc for Windows) should be fully supported by
1780 LodePNG.
1781
1782 *) Visual Studio and Visual C++ Express Edition
1783
1784 LodePNG should be warning-free with warning level W4. Two warnings were disabled
1785 with pragmas though: warning 4244 about implicit conversions, and warning 4996
1786 where it wants to use a non-standard function fopen_s instead of the standard C
1787 fopen.
1788
1789 Visual Studio may want "stdafx.h" files to be included in each source file and
1790 give an error "unexpected end of file while looking for precompiled header".
1791 This is not standard C++ and will not be added to the stock LodePNG. You can
1792 disable it for lodepng.cpp only by right clicking it, Properties, C/C++,
1793 Precompiled Headers, and set it to Not Using Precompiled Headers there.
1794
1795 NOTE: Modern versions of VS should be fully supported, but old versions, e.g.
1796 VS6, are not guaranteed to work.
1797
1798 *) Compilers on Macintosh
1799
1800 LodePNG has been reported to work both with gcc and LLVM for Macintosh, both for
1801 C and C++.
1802
1803 *) Other Compilers
1804
1805 If you encounter problems on any compilers, feel free to let me know and I may
1806 try to fix it if the compiler is modern and standards compliant.
1807
1808
1809 10. examples
1810 ------------
1811
1812 This decoder example shows the most basic usage of LodePNG. More complex
1813 examples can be found on the LodePNG website.
1814
1815 NOTE: these examples do not support wide-character filenames, you can use an
1816 external method to handle such files and encode or decode in-memory
1817
1818 10.1. decoder C++ example
1819 -------------------------
1820
1821 #include "lodepng.h"
1822 #include <iostream>
1823
1824 int main(int argc, char *argv[]) {
1825 const char* filename = argc > 1 ? argv[1] : "test.png";
1826
1827 //load and decode
1828 std::vector<unsigned char> image;
1829 unsigned width, height;
1830 unsigned error = lodepng::decode(image, width, height, filename);
1831
1832 //if there's an error, display it
1833 if(error) std::cout << "decoder error " << error << ": " << lodepng_error_text(error) << std::endl;
1834
1835 //the pixels are now in the vector "image", 4 bytes per pixel, ordered RGBARGBA..., use it as texture, draw it, ...
1836 }
1837
1838 10.2. decoder C example
1839 -----------------------
1840
1841 #include "lodepng.h"
1842
1843 int main(int argc, char *argv[]) {
1844 unsigned error;
1845 unsigned char* image;
1846 size_t width, height;
1847 const char* filename = argc > 1 ? argv[1] : "test.png";
1848
1849 error = lodepng_decode32_file(&image, &width, &height, filename);
1850
1851 if(error) printf("decoder error %u: %s\n", error, lodepng_error_text(error));
1852
1853 / * use image here * /
1854
1855 free(image);
1856 return 0;
1857 }
1858
1859 11. state settings reference
1860 ----------------------------
1861
1862 A quick reference of some settings to set on the LodePNGState
1863
1864 For decoding:
1865
1866 state.decoder.zlibsettings.ignore_adler32: ignore ADLER32 checksums
1867 state.decoder.zlibsettings.custom_...: use custom inflate function
1868 state.decoder.ignore_crc: ignore CRC checksums
1869 state.decoder.ignore_critical: ignore unknown critical chunks
1870 state.decoder.ignore_end: ignore missing IEND chunk. May fail if this corruption causes other errors
1871 state.decoder.color_convert: convert internal PNG color to chosen one
1872 state.decoder.read_text_chunks: whether to read in text metadata chunks
1873 state.decoder.remember_unknown_chunks: whether to read in unknown chunks
1874 state.info_raw.colortype: desired color type for decoded image
1875 state.info_raw.bitdepth: desired bit depth for decoded image
1876 state.info_raw....: more color settings, see struct LodePNGColorMode
1877 state.info_png....: no settings for decoder but ouput, see struct LodePNGInfo
1878
1879 For encoding:
1880
1881 state.encoder.zlibsettings.btype: disable compression by setting it to 0
1882 state.encoder.zlibsettings.use_lz77: use LZ77 in compression
1883 state.encoder.zlibsettings.windowsize: tweak LZ77 windowsize
1884 state.encoder.zlibsettings.minmatch: tweak min LZ77 length to match
1885 state.encoder.zlibsettings.nicematch: tweak LZ77 match where to stop searching
1886 state.encoder.zlibsettings.lazymatching: try one more LZ77 matching
1887 state.encoder.zlibsettings.custom_...: use custom deflate function
1888 state.encoder.auto_convert: choose optimal PNG color type, if 0 uses info_png
1889 state.encoder.filter_palette_zero: PNG filter strategy for palette
1890 state.encoder.filter_strategy: PNG filter strategy to encode with
1891 state.encoder.force_palette: add palette even if not encoding to one
1892 state.encoder.add_id: add LodePNG identifier and version as a text chunk
1893 state.encoder.text_compression: use compressed text chunks for metadata
1894 state.info_raw.colortype: color type of raw input image you provide
1895 state.info_raw.bitdepth: bit depth of raw input image you provide
1896 state.info_raw: more color settings, see struct LodePNGColorMode
1897 state.info_png.color.colortype: desired color type if auto_convert is false
1898 state.info_png.color.bitdepth: desired bit depth if auto_convert is false
1899 state.info_png.color....: more color settings, see struct LodePNGColorMode
1900 state.info_png....: more PNG related settings, see struct LodePNGInfo
1901
1902
1903 12. changes
1904 -----------
1905
1906 The version number of LodePNG is the date of the change given in the format
1907 yyyymmdd.
1908
1909 Some changes aren't backwards compatible. Those are indicated with a (!)
1910 symbol.
1911
1912 Not all changes are listed here, the commit history in github lists more:
1913 https://github.com/lvandeve/lodepng
1914
1915 *) 10 apr 2023: faster CRC32 implementation, but with larger lookup table.
1916 *) 13 jun 2022: added support for the sBIT chunk.
1917 *) 09 jan 2022: minor decoder speed improvements.
1918 *) 27 jun 2021: added warnings that file reading/writing functions don't support
1919 wide-character filenames (support for this is not planned, opening files is
1920 not the core part of PNG decoding/decoding and is platform dependent).
1921 *) 17 okt 2020: prevent decoding too large text/icc chunks by default.
1922 *) 06 mar 2020: simplified some of the dynamic memory allocations.
1923 *) 12 jan 2020: (!) added 'end' argument to lodepng_chunk_next to allow correct
1924 overflow checks.
1925 *) 14 aug 2019: around 25% faster decoding thanks to huffman lookup tables.
1926 *) 15 jun 2019: (!) auto_choose_color API changed (for bugfix: don't use palette
1927 if gray ICC profile) and non-ICC LodePNGColorProfile renamed to
1928 LodePNGColorStats.
1929 *) 30 dec 2018: code style changes only: removed newlines before opening braces.
1930 *) 10 sep 2018: added way to inspect metadata chunks without full decoding.
1931 *) 19 aug 2018: (!) fixed color mode bKGD is encoded with and made it use
1932 palette index in case of palette.
1933 *) 10 aug 2018: (!) added support for gAMA, cHRM, sRGB and iCCP chunks. This
1934 change is backwards compatible unless you relied on unknown_chunks for those.
1935 *) 11 jun 2018: less restrictive check for pixel size integer overflow
1936 *) 14 jan 2018: allow optionally ignoring a few more recoverable errors
1937 *) 17 sep 2017: fix memory leak for some encoder input error cases
1938 *) 27 nov 2016: grey+alpha auto color model detection bugfix
1939 *) 18 apr 2016: Changed qsort to custom stable sort (for platforms w/o qsort).
1940 *) 09 apr 2016: Fixed colorkey usage detection, and better file loading (within
1941 the limits of pure C90).
1942 *) 08 dec 2015: Made load_file function return error if file can't be opened.
1943 *) 24 okt 2015: Bugfix with decoding to palette output.
1944 *) 18 apr 2015: Boundary PM instead of just package-merge for faster encoding.
1945 *) 24 aug 2014: Moved to github
1946 *) 23 aug 2014: Reduced needless memory usage of decoder.
1947 *) 28 jun 2014: Removed fix_png setting, always support palette OOB for
1948 simplicity. Made ColorProfile public.
1949 *) 09 jun 2014: Faster encoder by fixing hash bug and more zeros optimization.
1950 *) 22 dec 2013: Power of two windowsize required for optimization.
1951 *) 15 apr 2013: Fixed bug with LAC_ALPHA and color key.
1952 *) 25 mar 2013: Added an optional feature to ignore some PNG errors (fix_png).
1953 *) 11 mar 2013: (!) Bugfix with custom free. Changed from "my" to "lodepng_"
1954 prefix for the custom allocators and made it possible with a new #define to
1955 use custom ones in your project without needing to change lodepng's code.
1956 *) 28 jan 2013: Bugfix with color key.
1957 *) 27 okt 2012: Tweaks in text chunk keyword length error handling.
1958 *) 8 okt 2012: (!) Added new filter strategy (entropy) and new auto color mode.
1959 (no palette). Better deflate tree encoding. New compression tweak settings.
1960 Faster color conversions while decoding. Some internal cleanups.
1961 *) 23 sep 2012: Reduced warnings in Visual Studio a little bit.
1962 *) 1 sep 2012: (!) Removed #define's for giving custom (de)compression functions
1963 and made it work with function pointers instead.
1964 *) 23 jun 2012: Added more filter strategies. Made it easier to use custom alloc
1965 and free functions and toggle #defines from compiler flags. Small fixes.
1966 *) 6 may 2012: (!) Made plugging in custom zlib/deflate functions more flexible.
1967 *) 22 apr 2012: (!) Made interface more consistent, renaming a lot. Removed
1968 redundant C++ codec classes. Reduced amount of structs. Everything changed,
1969 but it is cleaner now imho and functionality remains the same. Also fixed
1970 several bugs and shrunk the implementation code. Made new samples.
1971 *) 6 nov 2011: (!) By default, the encoder now automatically chooses the best
1972 PNG color model and bit depth, based on the amount and type of colors of the
1973 raw image. For this, autoLeaveOutAlphaChannel replaced by auto_choose_color.
1974 *) 9 okt 2011: simpler hash chain implementation for the encoder.
1975 *) 8 sep 2011: lz77 encoder lazy matching instead of greedy matching.
1976 *) 23 aug 2011: tweaked the zlib compression parameters after benchmarking.
1977 A bug with the PNG filtertype heuristic was fixed, so that it chooses much
1978 better ones (it's quite significant). A setting to do an experimental, slow,
1979 brute force search for PNG filter types is added.
1980 *) 17 aug 2011: (!) changed some C zlib related function names.
1981 *) 16 aug 2011: made the code less wide (max 120 characters per line).
1982 *) 17 apr 2011: code cleanup. Bugfixes. Convert low to 16-bit per sample colors.
1983 *) 21 feb 2011: fixed compiling for C90. Fixed compiling with sections disabled.
1984 *) 11 dec 2010: encoding is made faster, based on suggestion by Peter Eastman
1985 to optimize long sequences of zeros.
1986 *) 13 nov 2010: added LodePNG_InfoColor_hasPaletteAlpha and
1987 LodePNG_InfoColor_canHaveAlpha functions for convenience.
1988 *) 7 nov 2010: added LodePNG_error_text function to get error code description.
1989 *) 30 okt 2010: made decoding slightly faster
1990 *) 26 okt 2010: (!) changed some C function and struct names (more consistent).
1991 Reorganized the documentation and the declaration order in the header.
1992 *) 08 aug 2010: only changed some comments and external samples.
1993 *) 05 jul 2010: fixed bug thanks to warnings in the new gcc version.
1994 *) 14 mar 2010: fixed bug where too much memory was allocated for char buffers.
1995 *) 02 sep 2008: fixed bug where it could create empty tree that linux apps could
1996 read by ignoring the problem but windows apps couldn't.
1997 *) 06 jun 2008: added more error checks for out of memory cases.
1998 *) 26 apr 2008: added a few more checks here and there to ensure more safety.
1999 *) 06 mar 2008: crash with encoding of strings fixed
2000 *) 02 feb 2008: support for international text chunks added (iTXt)
2001 *) 23 jan 2008: small cleanups, and #defines to divide code in sections
2002 *) 20 jan 2008: support for unknown chunks allowing using LodePNG for an editor.
2003 *) 18 jan 2008: support for tIME and pHYs chunks added to encoder and decoder.
2004 *) 17 jan 2008: ability to encode and decode compressed zTXt chunks added
2005 Also various fixes, such as in the deflate and the padding bits code.
2006 *) 13 jan 2008: Added ability to encode Adam7-interlaced images. Improved
2007 filtering code of encoder.
2008 *) 07 jan 2008: (!) changed LodePNG to use ISO C90 instead of C++. A
2009 C++ wrapper around this provides an interface almost identical to before.
2010 Having LodePNG be pure ISO C90 makes it more portable. The C and C++ code
2011 are together in these files but it works both for C and C++ compilers.
2012 *) 29 dec 2007: (!) changed most integer types to unsigned int + other tweaks
2013 *) 30 aug 2007: bug fixed which makes this Borland C++ compatible
2014 *) 09 aug 2007: some VS2005 warnings removed again
2015 *) 21 jul 2007: deflate code placed in new namespace separate from zlib code
2016 *) 08 jun 2007: fixed bug with 2- and 4-bit color, and small interlaced images
2017 *) 04 jun 2007: improved support for Visual Studio 2005: crash with accessing
2018 invalid std::vector element [0] fixed, and level 3 and 4 warnings removed
2019 *) 02 jun 2007: made the encoder add a tag with version by default
2020 *) 27 may 2007: zlib and png code separated (but still in the same file),
2021 simple encoder/decoder functions added for more simple usage cases
2022 *) 19 may 2007: minor fixes, some code cleaning, new error added (error 69),
2023 moved some examples from here to lodepng_examples.cpp
2024 *) 12 may 2007: palette decoding bug fixed
2025 *) 24 apr 2007: changed the license from BSD to the zlib license
2026 *) 11 mar 2007: very simple addition: ability to encode bKGD chunks.
2027 *) 04 mar 2007: (!) tEXt chunk related fixes, and support for encoding
2028 palettized PNG images. Plus little interface change with palette and texts.
2029 *) 03 mar 2007: Made it encode dynamic Huffman shorter with repeat codes.
2030 Fixed a bug where the end code of a block had length 0 in the Huffman tree.
2031 *) 26 feb 2007: Huffman compression with dynamic trees (BTYPE 2) now implemented
2032 and supported by the encoder, resulting in smaller PNGs at the output.
2033 *) 27 jan 2007: Made the Adler-32 test faster so that a timewaste is gone.
2034 *) 24 jan 2007: gave encoder an error interface. Added color conversion from any
2035 greyscale type to 8-bit greyscale with or without alpha.
2036 *) 21 jan 2007: (!) Totally changed the interface. It allows more color types
2037 to convert to and is more uniform. See the manual for how it works now.
2038 *) 07 jan 2007: Some cleanup & fixes, and a few changes over the last days:
2039 encode/decode custom tEXt chunks, separate classes for zlib & deflate, and
2040 at last made the decoder give errors for incorrect Adler32 or Crc.
2041 *) 01 jan 2007: Fixed bug with encoding PNGs with less than 8 bits per channel.
2042 *) 29 dec 2006: Added support for encoding images without alpha channel, and
2043 cleaned out code as well as making certain parts faster.
2044 *) 28 dec 2006: Added "Settings" to the encoder.
2045 *) 26 dec 2006: The encoder now does LZ77 encoding and produces much smaller files now.
2046 Removed some code duplication in the decoder. Fixed little bug in an example.
2047 *) 09 dec 2006: (!) Placed output parameters of public functions as first parameter.
2048 Fixed a bug of the decoder with 16-bit per color.
2049 *) 15 okt 2006: Changed documentation structure
2050 *) 09 okt 2006: Encoder class added. It encodes a valid PNG image from the
2051 given image buffer, however for now it's not compressed.
2052 *) 08 sep 2006: (!) Changed to interface with a Decoder class
2053 *) 30 jul 2006: (!) LodePNG_InfoPng , width and height are now retrieved in different
2054 way. Renamed decodePNG to decodePNGGeneric.
2055 *) 29 jul 2006: (!) Changed the interface: image info is now returned as a
2056 struct of type LodePNG::LodePNG_Info, instead of a vector, which was a bit clumsy.
2057 *) 28 jul 2006: Cleaned the code and added new error checks.
2058 Corrected terminology "deflate" into "inflate".
2059 *) 23 jun 2006: Added SDL example in the documentation in the header, this
2060 example allows easy debugging by displaying the PNG and its transparency.
2061 *) 22 jun 2006: (!) Changed way to obtain error value. Added
2062 loadFile function for convenience. Made decodePNG32 faster.
2063 *) 21 jun 2006: (!) Changed type of info vector to unsigned.
2064 Changed position of palette in info vector. Fixed an important bug that
2065 happened on PNGs with an uncompressed block.
2066 *) 16 jun 2006: Internally changed unsigned into unsigned where
2067 needed, and performed some optimizations.
2068 *) 07 jun 2006: (!) Renamed functions to decodePNG and placed them
2069 in LodePNG namespace. Changed the order of the parameters. Rewrote the
2070 documentation in the header. Renamed files to lodepng.cpp and lodepng.h
2071 *) 22 apr 2006: Optimized and improved some code
2072 *) 07 sep 2005: (!) Changed to std::vector interface
2073 *) 12 aug 2005: Initial release (C++, decoder only)
2074
2075
2076 13. contact information
2077 -----------------------
2078
2079 Feel free to contact me with suggestions, problems, comments, ... concerning
2080 LodePNG. If you encounter a PNG image that doesn't work properly with this
2081 decoder, feel free to send it and I'll use it to find and fix the problem.
2082
2083 My email address is (puzzle the account and domain together with an @ symbol):
2084 Domain: gmail dot com.
2085 Account: lode dot vandevenne.
2086
2087
2088 Copyright (c) 2005-2022 Lode Vandevenne
2089 */