· 6 years ago · Jun 25, 2019, 12:00 AM
1/*
2LodePNG version 20160124
3
4Copyright (c) 2005-2016 Lode Vandevenne
5
6This software is provided 'as-is', without any express or implied
7warranty. In no event will the authors be held liable for any damages
8arising from the use of this software.
9
10Permission is granted to anyone to use this software for any purpose,
11including commercial applications, and to alter it and redistribute it
12freely, 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
31extern const char* LODEPNG_VERSION_STRING;
32
33/*
34The following #defines are used to create code sections. They can be disabled
35to disable code sections, which can give faster compile time and smaller binary.
36The "NO_COMPILE" defines are designed to be used to pass as defines to the
37compiler command to disable them without modifying this header, e.g.
38-DLODEPNG_NO_COMPILE_ZLIB for gcc.
39In addition to those below, you can also define LODEPNG_NO_COMPILE_CRC to
40allow implementing a custom lodepng_crc32.
41*/
42/*deflate & zlib. If disabled, you must specify alternative zlib functions in
43the custom_zlib field of the compress and decompress settings*/
44#ifndef LODEPNG_NO_COMPILE_ZLIB
45#define LODEPNG_COMPILE_ZLIB
46#endif
47/*png encoder and png decoder*/
48#ifndef LODEPNG_NO_COMPILE_PNG
49#define LODEPNG_COMPILE_PNG
50#endif
51/*deflate&zlib decoder and png decoder*/
52#ifndef LODEPNG_NO_COMPILE_DECODER
53#define LODEPNG_COMPILE_DECODER
54#endif
55/*deflate&zlib encoder and png encoder*/
56#ifndef LODEPNG_NO_COMPILE_ENCODER
57#define LODEPNG_COMPILE_ENCODER
58#endif
59/*the optional built in harddisk file loading and saving functions*/
60#ifndef LODEPNG_NO_COMPILE_DISK
61#define LODEPNG_COMPILE_DISK
62#endif
63/*support for chunks other than IHDR, IDAT, PLTE, tRNS, IEND: ancillary and unknown chunks*/
64#ifndef LODEPNG_NO_COMPILE_ANCILLARY_CHUNKS
65#define LODEPNG_COMPILE_ANCILLARY_CHUNKS
66#endif
67/*ability to convert error numerical codes to English text string*/
68#ifndef LODEPNG_NO_COMPILE_ERROR_TEXT
69#define LODEPNG_COMPILE_ERROR_TEXT
70#endif
71/*Compile the default allocators (C's free, malloc and realloc). If you disable this,
72you can define the functions lodepng_free, lodepng_malloc and lodepng_realloc in your
73source files with custom allocators.*/
74#ifndef LODEPNG_NO_COMPILE_ALLOCATORS
75#define LODEPNG_COMPILE_ALLOCATORS
76#endif
77/*compile the C++ version (you can disable the C++ wrapper here even when compiling for C++)*/
78#ifdef __cplusplus
79#ifndef LODEPNG_NO_COMPILE_CPP
80#define LODEPNG_COMPILE_CPP
81#endif
82#endif
83
84#ifdef LODEPNG_COMPILE_CPP
85#include <vector>
86#include <string>
87#endif /*LODEPNG_COMPILE_CPP*/
88
89#ifdef LODEPNG_COMPILE_PNG
90/*The PNG color types (also used for raw).*/
91typedef enum LodePNGColorType
92{
93 LCT_GREY = 0, /*greyscale: 1,2,4,8,16 bit*/
94 LCT_RGB = 2, /*RGB: 8,16 bit*/
95 LCT_PALETTE = 3, /*palette: 1,2,4,8 bit*/
96 LCT_GREY_ALPHA = 4, /*greyscale with alpha: 8,16 bit*/
97 LCT_RGBA = 6 /*RGB with alpha: 8,16 bit*/
98} LodePNGColorType;
99
100#ifdef LODEPNG_COMPILE_DECODER
101/*
102Converts PNG data in memory to raw pixel data.
103out: Output parameter. Pointer to buffer that will contain the raw pixel data.
104 After decoding, its size is w * h * (bytes per pixel) bytes larger than
105 initially. Bytes per pixel depends on colortype and bitdepth.
106 Must be freed after usage with free(*out).
107 Note: for 16-bit per channel colors, uses big endian format like PNG does.
108w: Output parameter. Pointer to width of pixel data.
109h: Output parameter. Pointer to height of pixel data.
110in: Memory buffer with the PNG file.
111insize: size of the in buffer.
112colortype: the desired color type for the raw output image. See explanation on PNG color types.
113bitdepth: the desired bit depth for the raw output image. See explanation on PNG color types.
114Return value: LodePNG error code (0 means no error).
115*/
116unsigned lodepng_decode_memory(unsigned char** out, unsigned* w, unsigned* h,
117 const unsigned char* in, size_t insize,
118 LodePNGColorType colortype, unsigned bitdepth);
119
120/*Same as lodepng_decode_memory, but always decodes to 32-bit RGBA raw image*/
121unsigned lodepng_decode32(unsigned char** out, unsigned* w, unsigned* h,
122 const unsigned char* in, size_t insize);
123
124/*Same as lodepng_decode_memory, but always decodes to 24-bit RGB raw image*/
125unsigned lodepng_decode24(unsigned char** out, unsigned* w, unsigned* h,
126 const unsigned char* in, size_t insize);
127
128#ifdef LODEPNG_COMPILE_DISK
129/*
130Load PNG from disk, from file with given name.
131Same as the other decode functions, but instead takes a filename as input.
132*/
133unsigned lodepng_decode_file(unsigned char** out, unsigned* w, unsigned* h,
134 const char* filename,
135 LodePNGColorType colortype, unsigned bitdepth);
136
137/*Same as lodepng_decode_file, but always decodes to 32-bit RGBA raw image.*/
138unsigned lodepng_decode32_file(unsigned char** out, unsigned* w, unsigned* h,
139 const char* filename);
140
141/*Same as lodepng_decode_file, but always decodes to 24-bit RGB raw image.*/
142unsigned lodepng_decode24_file(unsigned char** out, unsigned* w, unsigned* h,
143 const char* filename);
144#endif /*LODEPNG_COMPILE_DISK*/
145#endif /*LODEPNG_COMPILE_DECODER*/
146
147
148#ifdef LODEPNG_COMPILE_ENCODER
149/*
150Converts raw pixel data into a PNG image in memory. The colortype and bitdepth
151 of the output PNG image cannot be chosen, they are automatically determined
152 by the colortype, bitdepth and content of the input pixel data.
153 Note: for 16-bit per channel colors, needs big endian format like PNG does.
154out: Output parameter. Pointer to buffer that will contain the PNG image data.
155 Must be freed after usage with free(*out).
156outsize: Output parameter. Pointer to the size in bytes of the out buffer.
157image: The raw pixel data to encode. The size of this buffer should be
158 w * h * (bytes per pixel), bytes per pixel depends on colortype and bitdepth.
159w: width of the raw pixel data in pixels.
160h: height of the raw pixel data in pixels.
161colortype: the color type of the raw input image. See explanation on PNG color types.
162bitdepth: the bit depth of the raw input image. See explanation on PNG color types.
163Return value: LodePNG error code (0 means no error).
164*/
165unsigned lodepng_encode_memory(unsigned char** out, size_t* outsize,
166 const unsigned char* image, unsigned w, unsigned h,
167 LodePNGColorType colortype, unsigned bitdepth);
168
169/*Same as lodepng_encode_memory, but always encodes from 32-bit RGBA raw image.*/
170unsigned lodepng_encode32(unsigned char** out, size_t* outsize,
171 const unsigned char* image, unsigned w, unsigned h);
172
173/*Same as lodepng_encode_memory, but always encodes from 24-bit RGB raw image.*/
174unsigned lodepng_encode24(unsigned char** out, size_t* outsize,
175 const unsigned char* image, unsigned w, unsigned h);
176
177#ifdef LODEPNG_COMPILE_DISK
178/*
179Converts raw pixel data into a PNG file on disk.
180Same as the other encode functions, but instead takes a filename as output.
181NOTE: This overwrites existing files without warning!
182*/
183unsigned lodepng_encode_file(const char* filename,
184 const unsigned char* image, unsigned w, unsigned h,
185 LodePNGColorType colortype, unsigned bitdepth);
186
187/*Same as lodepng_encode_file, but always encodes from 32-bit RGBA raw image.*/
188unsigned lodepng_encode32_file(const char* filename,
189 const unsigned char* image, unsigned w, unsigned h);
190
191/*Same as lodepng_encode_file, but always encodes from 24-bit RGB raw image.*/
192unsigned lodepng_encode24_file(const char* filename,
193 const unsigned char* image, unsigned w, unsigned h);
194#endif /*LODEPNG_COMPILE_DISK*/
195#endif /*LODEPNG_COMPILE_ENCODER*/
196
197
198#ifdef LODEPNG_COMPILE_CPP
199namespace lodepng
200{
201#ifdef LODEPNG_COMPILE_DECODER
202/*Same as lodepng_decode_memory, but decodes to an std::vector. The colortype
203is the format to output the pixels to. Default is RGBA 8-bit per channel.*/
204unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
205 const unsigned char* in, size_t insize,
206 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
207unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
208 const std::vector<unsigned char>& in,
209 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
210#ifdef LODEPNG_COMPILE_DISK
211/*
212Converts PNG file from disk to raw pixel data in memory.
213Same as the other decode functions, but instead takes a filename as input.
214*/
215unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
216 const std::string& filename,
217 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
218#endif /* LODEPNG_COMPILE_DISK */
219#endif /* LODEPNG_COMPILE_DECODER */
220
221#ifdef LODEPNG_COMPILE_ENCODER
222/*Same as lodepng_encode_memory, but encodes to an std::vector. colortype
223is that of the raw input data. The output PNG color type will be auto chosen.*/
224unsigned encode(std::vector<unsigned char>& out,
225 const unsigned char* in, unsigned w, unsigned h,
226 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
227unsigned encode(std::vector<unsigned char>& out,
228 const std::vector<unsigned char>& in, unsigned w, unsigned h,
229 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
230#ifdef LODEPNG_COMPILE_DISK
231/*
232Converts 32-bit RGBA raw pixel data into a PNG file on disk.
233Same as the other encode functions, but instead takes a filename as output.
234NOTE: This overwrites existing files without warning!
235*/
236unsigned encode(const std::string& filename,
237 const unsigned char* in, unsigned w, unsigned h,
238 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
239unsigned encode(const std::string& filename,
240 const std::vector<unsigned char>& in, unsigned w, unsigned h,
241 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
242#endif /* LODEPNG_COMPILE_DISK */
243#endif /* LODEPNG_COMPILE_ENCODER */
244} /* namespace lodepng */
245#endif /*LODEPNG_COMPILE_CPP*/
246#endif /*LODEPNG_COMPILE_PNG*/
247
248#ifdef LODEPNG_COMPILE_ERROR_TEXT
249/*Returns an English description of the numerical error code.*/
250const char* lodepng_error_text(unsigned code);
251#endif /*LODEPNG_COMPILE_ERROR_TEXT*/
252
253#ifdef LODEPNG_COMPILE_DECODER
254/*Settings for zlib decompression*/
255typedef struct LodePNGDecompressSettings LodePNGDecompressSettings;
256struct LodePNGDecompressSettings
257{
258 unsigned ignore_adler32; /*if 1, continue and don't give an error message if the Adler32 checksum is corrupted*/
259
260 /*use custom zlib decoder instead of built in one (default: null)*/
261 unsigned (*custom_zlib)(unsigned char**, size_t*,
262 const unsigned char*, size_t,
263 const LodePNGDecompressSettings*);
264 /*use custom deflate decoder instead of built in one (default: null)
265 if custom_zlib is used, custom_deflate is ignored since only the built in
266 zlib function will call custom_deflate*/
267 unsigned (*custom_inflate)(unsigned char**, size_t*,
268 const unsigned char*, size_t,
269 const LodePNGDecompressSettings*);
270
271 const void* custom_context; /*optional custom settings for custom functions*/
272};
273
274extern const LodePNGDecompressSettings lodepng_default_decompress_settings;
275void lodepng_decompress_settings_init(LodePNGDecompressSettings* settings);
276#endif /*LODEPNG_COMPILE_DECODER*/
277
278#ifdef LODEPNG_COMPILE_ENCODER
279/*
280Settings for zlib compression. Tweaking these settings tweaks the balance
281between speed and compression ratio.
282*/
283typedef struct LodePNGCompressSettings LodePNGCompressSettings;
284struct LodePNGCompressSettings /*deflate = compress*/
285{
286 /*LZ77 related settings*/
287 unsigned btype; /*the block type for LZ (0, 1, 2 or 3, see zlib standard). Should be 2 for proper compression.*/
288 unsigned use_lz77; /*whether or not to use LZ77. Should be 1 for proper compression.*/
289 unsigned windowsize; /*must be a power of two <= 32768. higher compresses more but is slower. Default value: 2048.*/
290 unsigned minmatch; /*mininum lz77 length. 3 is normally best, 6 can be better for some PNGs. Default: 0*/
291 unsigned nicematch; /*stop searching if >= this length found. Set to 258 for best compression. Default: 128*/
292 unsigned lazymatching; /*use lazy matching: better compression but a bit slower. Default: true*/
293
294 /*use custom zlib encoder instead of built in one (default: null)*/
295 unsigned (*custom_zlib)(unsigned char**, size_t*,
296 const unsigned char*, size_t,
297 const LodePNGCompressSettings*);
298 /*use custom deflate encoder instead of built in one (default: null)
299 if custom_zlib is used, custom_deflate is ignored since only the built in
300 zlib function will call custom_deflate*/
301 unsigned (*custom_deflate)(unsigned char**, size_t*,
302 const unsigned char*, size_t,
303 const LodePNGCompressSettings*);
304
305 const void* custom_context; /*optional custom settings for custom functions*/
306};
307
308extern const LodePNGCompressSettings lodepng_default_compress_settings;
309void lodepng_compress_settings_init(LodePNGCompressSettings* settings);
310#endif /*LODEPNG_COMPILE_ENCODER*/
311
312#ifdef LODEPNG_COMPILE_PNG
313/*
314Color mode of an image. Contains all information required to decode the pixel
315bits to RGBA colors. This information is the same as used in the PNG file
316format, and is used both for PNG and raw image data in LodePNG.
317*/
318typedef struct LodePNGColorMode
319{
320 /*header (IHDR)*/
321 LodePNGColorType colortype; /*color type, see PNG standard or documentation further in this header file*/
322 unsigned bitdepth; /*bits per sample, see PNG standard or documentation further in this header file*/
323
324 /*
325 palette (PLTE and tRNS)
326
327 Dynamically allocated with the colors of the palette, including alpha.
328 When encoding a PNG, to store your colors in the palette of the LodePNGColorMode, first use
329 lodepng_palette_clear, then for each color use lodepng_palette_add.
330 If you encode an image without alpha with palette, don't forget to put value 255 in each A byte of the palette.
331
332 When decoding, by default you can ignore this palette, since LodePNG already
333 fills the palette colors in the pixels of the raw RGBA output.
334
335 The palette is only supported for color type 3.
336 */
337 unsigned char* palette; /*palette in RGBARGBA... order. When allocated, must be either 0, or have size 1024*/
338 size_t palettesize; /*palette size in number of colors (amount of bytes is 4 * palettesize)*/
339
340 /*
341 transparent color key (tRNS)
342
343 This color uses the same bit depth as the bitdepth value in this struct, which can be 1-bit to 16-bit.
344 For greyscale PNGs, r, g and b will all 3 be set to the same.
345
346 When decoding, by default you can ignore this information, since LodePNG sets
347 pixels with this key to transparent already in the raw RGBA output.
348
349 The color key is only supported for color types 0 and 2.
350 */
351 unsigned key_defined; /*is a transparent color key given? 0 = false, 1 = true*/
352 unsigned key_r; /*red/greyscale component of color key*/
353 unsigned key_g; /*green component of color key*/
354 unsigned key_b; /*blue component of color key*/
355} LodePNGColorMode;
356
357/*init, cleanup and copy functions to use with this struct*/
358void lodepng_color_mode_init(LodePNGColorMode* info);
359void lodepng_color_mode_cleanup(LodePNGColorMode* info);
360/*return value is error code (0 means no error)*/
361unsigned lodepng_color_mode_copy(LodePNGColorMode* dest, const LodePNGColorMode* source);
362
363void lodepng_palette_clear(LodePNGColorMode* info);
364/*add 1 color to the palette*/
365unsigned lodepng_palette_add(LodePNGColorMode* info,
366 unsigned char r, unsigned char g, unsigned char b, unsigned char a);
367
368/*get the total amount of bits per pixel, based on colortype and bitdepth in the struct*/
369unsigned lodepng_get_bpp(const LodePNGColorMode* info);
370/*get the amount of color channels used, based on colortype in the struct.
371If a palette is used, it counts as 1 channel.*/
372unsigned lodepng_get_channels(const LodePNGColorMode* info);
373/*is it a greyscale type? (only colortype 0 or 4)*/
374unsigned lodepng_is_greyscale_type(const LodePNGColorMode* info);
375/*has it got an alpha channel? (only colortype 2 or 6)*/
376unsigned lodepng_is_alpha_type(const LodePNGColorMode* info);
377/*has it got a palette? (only colortype 3)*/
378unsigned lodepng_is_palette_type(const LodePNGColorMode* info);
379/*only returns true if there is a palette and there is a value in the palette with alpha < 255.
380Loops through the palette to check this.*/
381unsigned lodepng_has_palette_alpha(const LodePNGColorMode* info);
382/*
383Check if the given color info indicates the possibility of having non-opaque pixels in the PNG image.
384Returns true if the image can have translucent or invisible pixels (it still be opaque if it doesn't use such pixels).
385Returns false if the image can only have opaque pixels.
386In detail, it returns true only if it's a color type with alpha, or has a palette with non-opaque values,
387or if "key_defined" is true.
388*/
389unsigned lodepng_can_have_alpha(const LodePNGColorMode* info);
390/*Returns the byte size of a raw image buffer with given width, height and color mode*/
391size_t lodepng_get_raw_size(unsigned w, unsigned h, const LodePNGColorMode* color);
392
393#ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
394/*The information of a Time chunk in PNG.*/
395typedef struct LodePNGTime
396{
397 unsigned year; /*2 bytes used (0-65535)*/
398 unsigned month; /*1-12*/
399 unsigned day; /*1-31*/
400 unsigned hour; /*0-23*/
401 unsigned minute; /*0-59*/
402 unsigned second; /*0-60 (to allow for leap seconds)*/
403} LodePNGTime;
404#endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
405
406/*Information about the PNG image, except pixels, width and height.*/
407typedef struct LodePNGInfo
408{
409 /*header (IHDR), palette (PLTE) and transparency (tRNS) chunks*/
410 unsigned compression_method;/*compression method of the original file. Always 0.*/
411 unsigned filter_method; /*filter method of the original file*/
412 unsigned interlace_method; /*interlace method of the original file*/
413 LodePNGColorMode color; /*color type and bits, palette and transparency of the PNG file*/
414
415#ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
416 /*
417 suggested background color chunk (bKGD)
418 This color uses the same color mode as the PNG (except alpha channel), which can be 1-bit to 16-bit.
419
420 For greyscale PNGs, r, g and b will all 3 be set to the same. When encoding
421 the encoder writes the red one. For palette PNGs: When decoding, the RGB value
422 will be stored, not a palette index. But when encoding, specify the index of
423 the palette in background_r, the other two are then ignored.
424
425 The decoder does not use this background color to edit the color of pixels.
426 */
427 unsigned background_defined; /*is a suggested background color given?*/
428 unsigned background_r; /*red component of suggested background color*/
429 unsigned background_g; /*green component of suggested background color*/
430 unsigned background_b; /*blue component of suggested background color*/
431
432 /*
433 non-international text chunks (tEXt and zTXt)
434
435 The char** arrays each contain num strings. The actual messages are in
436 text_strings, while text_keys are keywords that give a short description what
437 the actual text represents, e.g. Title, Author, Description, or anything else.
438
439 A keyword is minimum 1 character and maximum 79 characters long. It's
440 discouraged to use a single line length longer than 79 characters for texts.
441
442 Don't allocate these text buffers yourself. Use the init/cleanup functions
443 correctly and use lodepng_add_text and lodepng_clear_text.
444 */
445 size_t text_num; /*the amount of texts in these char** buffers (there may be more texts in itext)*/
446 char** text_keys; /*the keyword of a text chunk (e.g. "Comment")*/
447 char** text_strings; /*the actual text*/
448
449 /*
450 international text chunks (iTXt)
451 Similar to the non-international text chunks, but with additional strings
452 "langtags" and "transkeys".
453 */
454 size_t itext_num; /*the amount of international texts in this PNG*/
455 char** itext_keys; /*the English keyword of the text chunk (e.g. "Comment")*/
456 char** itext_langtags; /*language tag for this text's language, ISO/IEC 646 string, e.g. ISO 639 language tag*/
457 char** itext_transkeys; /*keyword translated to the international language - UTF-8 string*/
458 char** itext_strings; /*the actual international text - UTF-8 string*/
459
460 /*time chunk (tIME)*/
461 unsigned time_defined; /*set to 1 to make the encoder generate a tIME chunk*/
462 LodePNGTime time;
463
464 /*phys chunk (pHYs)*/
465 unsigned phys_defined; /*if 0, there is no pHYs chunk and the values below are undefined, if 1 else there is one*/
466 unsigned phys_x; /*pixels per unit in x direction*/
467 unsigned phys_y; /*pixels per unit in y direction*/
468 unsigned phys_unit; /*may be 0 (unknown unit) or 1 (metre)*/
469
470 /*
471 unknown chunks
472 There are 3 buffers, one for each position in the PNG where unknown chunks can appear
473 each buffer contains all unknown chunks for that position consecutively
474 The 3 buffers are the unknown chunks between certain critical chunks:
475 0: IHDR-PLTE, 1: PLTE-IDAT, 2: IDAT-IEND
476 Do not allocate or traverse this data yourself. Use the chunk traversing functions declared
477 later, such as lodepng_chunk_next and lodepng_chunk_append, to read/write this struct.
478 */
479 unsigned char* unknown_chunks_data[3];
480 size_t unknown_chunks_size[3]; /*size in bytes of the unknown chunks, given for protection*/
481#endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
482} LodePNGInfo;
483
484/*init, cleanup and copy functions to use with this struct*/
485void lodepng_info_init(LodePNGInfo* info);
486void lodepng_info_cleanup(LodePNGInfo* info);
487/*return value is error code (0 means no error)*/
488unsigned lodepng_info_copy(LodePNGInfo* dest, const LodePNGInfo* source);
489
490#ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
491void lodepng_clear_text(LodePNGInfo* info); /*use this to clear the texts again after you filled them in*/
492unsigned lodepng_add_text(LodePNGInfo* info, const char* key, const char* str); /*push back both texts at once*/
493
494void lodepng_clear_itext(LodePNGInfo* info); /*use this to clear the itexts again after you filled them in*/
495unsigned lodepng_add_itext(LodePNGInfo* info, const char* key, const char* langtag,
496 const char* transkey, const char* str); /*push back the 4 texts of 1 chunk at once*/
497#endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
498
499/*
500Converts raw buffer from one color type to another color type, based on
501LodePNGColorMode structs to describe the input and output color type.
502See the reference manual at the end of this header file to see which color conversions are supported.
503return value = LodePNG error code (0 if all went ok, an error if the conversion isn't supported)
504The out buffer must have size (w * h * bpp + 7) / 8, where bpp is the bits per pixel
505of the output color type (lodepng_get_bpp).
506For < 8 bpp images, there should not be padding bits at the end of scanlines.
507For 16-bit per channel colors, uses big endian format like PNG does.
508Return value is LodePNG error code
509*/
510unsigned lodepng_convert(unsigned char* out, const unsigned char* in,
511 const LodePNGColorMode* mode_out, const LodePNGColorMode* mode_in,
512 unsigned w, unsigned h);
513
514#ifdef LODEPNG_COMPILE_DECODER
515/*
516Settings for the decoder. This contains settings for the PNG and the Zlib
517decoder, but not the Info settings from the Info structs.
518*/
519typedef struct LodePNGDecoderSettings
520{
521 LodePNGDecompressSettings zlibsettings; /*in here is the setting to ignore Adler32 checksums*/
522
523 unsigned ignore_crc; /*ignore CRC checksums*/
524
525 unsigned color_convert; /*whether to convert the PNG to the color type you want. Default: yes*/
526
527#ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
528 unsigned read_text_chunks; /*if false but remember_unknown_chunks is true, they're stored in the unknown chunks*/
529 /*store all bytes from unknown chunks in the LodePNGInfo (off by default, useful for a png editor)*/
530 unsigned remember_unknown_chunks;
531#endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
532} LodePNGDecoderSettings;
533
534void lodepng_decoder_settings_init(LodePNGDecoderSettings* settings);
535#endif /*LODEPNG_COMPILE_DECODER*/
536
537#ifdef LODEPNG_COMPILE_ENCODER
538/*automatically use color type with less bits per pixel if losslessly possible. Default: AUTO*/
539typedef enum LodePNGFilterStrategy
540{
541 /*every filter at zero*/
542 LFS_ZERO,
543 /*Use filter that gives minimum sum, as described in the official PNG filter heuristic.*/
544 LFS_MINSUM,
545 /*Use the filter type that gives smallest Shannon entropy for this scanline. Depending
546 on the image, this is better or worse than minsum.*/
547 LFS_ENTROPY,
548 /*
549 Brute-force-search PNG filters by compressing each filter for each scanline.
550 Experimental, very slow, and only rarely gives better compression than MINSUM.
551 */
552 LFS_BRUTE_FORCE,
553 /*use predefined_filters buffer: you specify the filter type for each scanline*/
554 LFS_PREDEFINED
555} LodePNGFilterStrategy;
556
557/*Gives characteristics about the colors of the image, which helps decide which color model to use for encoding.
558Used internally by default if "auto_convert" is enabled. Public because it's useful for custom algorithms.*/
559typedef struct LodePNGColorProfile
560{
561 unsigned colored; /*not greyscale*/
562 unsigned key; /*if true, image is not opaque. Only if true and alpha is false, color key is possible.*/
563 unsigned short key_r; /*these values are always in 16-bit bitdepth in the profile*/
564 unsigned short key_g;
565 unsigned short key_b;
566 unsigned alpha; /*alpha channel or alpha palette required*/
567 unsigned numcolors; /*amount of colors, up to 257. Not valid if bits == 16.*/
568 unsigned char palette[1024]; /*Remembers up to the first 256 RGBA colors, in no particular order*/
569 unsigned bits; /*bits per channel (not for palette). 1,2 or 4 for greyscale only. 16 if 16-bit per channel required.*/
570} LodePNGColorProfile;
571
572void lodepng_color_profile_init(LodePNGColorProfile* profile);
573
574/*Get a LodePNGColorProfile of the image.*/
575unsigned lodepng_get_color_profile(LodePNGColorProfile* profile,
576 const unsigned char* image, unsigned w, unsigned h,
577 const LodePNGColorMode* mode_in);
578/*The function LodePNG uses internally to decide the PNG color with auto_convert.
579Chooses an optimal color model, e.g. grey if only grey pixels, palette if < 256 colors, ...*/
580unsigned lodepng_auto_choose_color(LodePNGColorMode* mode_out,
581 const unsigned char* image, unsigned w, unsigned h,
582 const LodePNGColorMode* mode_in);
583
584/*Settings for the encoder.*/
585typedef struct LodePNGEncoderSettings
586{
587 LodePNGCompressSettings zlibsettings; /*settings for the zlib encoder, such as window size, ...*/
588
589 unsigned auto_convert; /*automatically choose output PNG color type. Default: true*/
590
591 /*If true, follows the official PNG heuristic: if the PNG uses a palette or lower than
592 8 bit depth, set all filters to zero. Otherwise use the filter_strategy. Note that to
593 completely follow the official PNG heuristic, filter_palette_zero must be true and
594 filter_strategy must be LFS_MINSUM*/
595 unsigned filter_palette_zero;
596 /*Which filter strategy to use when not using zeroes due to filter_palette_zero.
597 Set filter_palette_zero to 0 to ensure always using your chosen strategy. Default: LFS_MINSUM*/
598 LodePNGFilterStrategy filter_strategy;
599 /*used if filter_strategy is LFS_PREDEFINED. In that case, this must point to a buffer with
600 the same length as the amount of scanlines in the image, and each value must <= 5. You
601 have to cleanup this buffer, LodePNG will never free it. Don't forget that filter_palette_zero
602 must be set to 0 to ensure this is also used on palette or low bitdepth images.*/
603 const unsigned char* predefined_filters;
604
605 /*force creating a PLTE chunk if colortype is 2 or 6 (= a suggested palette).
606 If colortype is 3, PLTE is _always_ created.*/
607 unsigned force_palette;
608#ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
609 /*add LodePNG identifier and version as a text chunk, for debugging*/
610 unsigned add_id;
611 /*encode text chunks as zTXt chunks instead of tEXt chunks, and use compression in iTXt chunks*/
612 unsigned text_compression;
613#endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
614} LodePNGEncoderSettings;
615
616void lodepng_encoder_settings_init(LodePNGEncoderSettings* settings);
617#endif /*LODEPNG_COMPILE_ENCODER*/
618
619
620#if defined(LODEPNG_COMPILE_DECODER) || defined(LODEPNG_COMPILE_ENCODER)
621/*The settings, state and information for extended encoding and decoding.*/
622typedef struct LodePNGState
623{
624#ifdef LODEPNG_COMPILE_DECODER
625 LodePNGDecoderSettings decoder; /*the decoding settings*/
626#endif /*LODEPNG_COMPILE_DECODER*/
627#ifdef LODEPNG_COMPILE_ENCODER
628 LodePNGEncoderSettings encoder; /*the encoding settings*/
629#endif /*LODEPNG_COMPILE_ENCODER*/
630 LodePNGColorMode info_raw; /*specifies the format in which you would like to get the raw pixel buffer*/
631 LodePNGInfo info_png; /*info of the PNG image obtained after decoding*/
632 unsigned error;
633#ifdef LODEPNG_COMPILE_CPP
634 /* For the lodepng::State subclass. */
635 virtual ~LodePNGState() {}
636#endif
637} LodePNGState;
638
639/*init, cleanup and copy functions to use with this struct*/
640void lodepng_state_init(LodePNGState* state);
641void lodepng_state_cleanup(LodePNGState* state);
642void lodepng_state_copy(LodePNGState* dest, const LodePNGState* source);
643#endif /* defined(LODEPNG_COMPILE_DECODER) || defined(LODEPNG_COMPILE_ENCODER) */
644
645#ifdef LODEPNG_COMPILE_DECODER
646/*
647Same as lodepng_decode_memory, but uses a LodePNGState to allow custom settings and
648getting much more information about the PNG image and color mode.
649*/
650unsigned lodepng_decode(unsigned char** out, unsigned* w, unsigned* h,
651 LodePNGState* state,
652 const unsigned char* in, size_t insize);
653
654/*
655Read the PNG header, but not the actual data. This returns only the information
656that is in the header chunk of the PNG, such as width, height and color type. The
657information is placed in the info_png field of the LodePNGState.
658*/
659unsigned lodepng_inspect(unsigned* w, unsigned* h,
660 LodePNGState* state,
661 const unsigned char* in, size_t insize);
662#endif /*LODEPNG_COMPILE_DECODER*/
663
664
665#ifdef LODEPNG_COMPILE_ENCODER
666/*This function allocates the out buffer with standard malloc and stores the size in *outsize.*/
667unsigned lodepng_encode(unsigned char** out, size_t* outsize,
668 const unsigned char* image, unsigned w, unsigned h,
669 LodePNGState* state);
670#endif /*LODEPNG_COMPILE_ENCODER*/
671
672/*
673The lodepng_chunk functions are normally not needed, except to traverse the
674unknown chunks stored in the LodePNGInfo struct, or add new ones to it.
675It also allows traversing the chunks of an encoded PNG file yourself.
676
677PNG standard chunk naming conventions:
678First byte: uppercase = critical, lowercase = ancillary
679Second byte: uppercase = public, lowercase = private
680Third byte: must be uppercase
681Fourth byte: uppercase = unsafe to copy, lowercase = safe to copy
682*/
683
684/*
685Gets the length of the data of the chunk. Total chunk length has 12 bytes more.
686There must be at least 4 bytes to read from. If the result value is too large,
687it may be corrupt data.
688*/
689unsigned lodepng_chunk_length(const unsigned char* chunk);
690
691/*puts the 4-byte type in null terminated string*/
692void lodepng_chunk_type(char type[5], const unsigned char* chunk);
693
694/*check if the type is the given type*/
695unsigned char lodepng_chunk_type_equals(const unsigned char* chunk, const char* type);
696
697/*0: it's one of the critical chunk types, 1: it's an ancillary chunk (see PNG standard)*/
698unsigned char lodepng_chunk_ancillary(const unsigned char* chunk);
699
700/*0: public, 1: private (see PNG standard)*/
701unsigned char lodepng_chunk_private(const unsigned char* chunk);
702
703/*0: the chunk is unsafe to copy, 1: the chunk is safe to copy (see PNG standard)*/
704unsigned char lodepng_chunk_safetocopy(const unsigned char* chunk);
705
706/*get pointer to the data of the chunk, where the input points to the header of the chunk*/
707unsigned char* lodepng_chunk_data(unsigned char* chunk);
708const unsigned char* lodepng_chunk_data_const(const unsigned char* chunk);
709
710/*returns 0 if the crc is correct, 1 if it's incorrect (0 for OK as usual!)*/
711unsigned lodepng_chunk_check_crc(const unsigned char* chunk);
712
713/*generates the correct CRC from the data and puts it in the last 4 bytes of the chunk*/
714void lodepng_chunk_generate_crc(unsigned char* chunk);
715
716/*iterate to next chunks. don't use on IEND chunk, as there is no next chunk then*/
717unsigned char* lodepng_chunk_next(unsigned char* chunk);
718const unsigned char* lodepng_chunk_next_const(const unsigned char* chunk);
719
720/*
721Appends chunk to the data in out. The given chunk should already have its chunk header.
722The out variable and outlength are updated to reflect the new reallocated buffer.
723Returns error code (0 if it went ok)
724*/
725unsigned lodepng_chunk_append(unsigned char** out, size_t* outlength, const unsigned char* chunk);
726
727/*
728Appends new chunk to out. The chunk to append is given by giving its length, type
729and data separately. The type is a 4-letter string.
730The out variable and outlength are updated to reflect the new reallocated buffer.
731Returne error code (0 if it went ok)
732*/
733unsigned lodepng_chunk_create(unsigned char** out, size_t* outlength, unsigned length,
734 const char* type, const unsigned char* data);
735
736
737/*Calculate CRC32 of buffer*/
738unsigned lodepng_crc32(const unsigned char* buf, size_t len);
739#endif /*LODEPNG_COMPILE_PNG*/
740
741
742#ifdef LODEPNG_COMPILE_ZLIB
743/*
744This zlib part can be used independently to zlib compress and decompress a
745buffer. It cannot be used to create gzip files however, and it only supports the
746part of zlib that is required for PNG, it does not support dictionaries.
747*/
748
749#ifdef LODEPNG_COMPILE_DECODER
750/*Inflate a buffer. Inflate is the decompression step of deflate. Out buffer must be freed after use.*/
751unsigned lodepng_inflate(unsigned char** out, size_t* outsize,
752 const unsigned char* in, size_t insize,
753 const LodePNGDecompressSettings* settings);
754
755/*
756Decompresses Zlib data. Reallocates the out buffer and appends the data. The
757data must be according to the zlib specification.
758Either, *out must be NULL and *outsize must be 0, or, *out must be a valid
759buffer and *outsize its size in bytes. out must be freed by user after usage.
760*/
761unsigned lodepng_zlib_decompress(unsigned char** out, size_t* outsize,
762 const unsigned char* in, size_t insize,
763 const LodePNGDecompressSettings* settings);
764#endif /*LODEPNG_COMPILE_DECODER*/
765
766#ifdef LODEPNG_COMPILE_ENCODER
767/*
768Compresses data with Zlib. Reallocates the out buffer and appends the data.
769Zlib adds a small header and trailer around the deflate data.
770The data is output in the format of the zlib specification.
771Either, *out must be NULL and *outsize must be 0, or, *out must be a valid
772buffer and *outsize its size in bytes. out must be freed by user after usage.
773*/
774unsigned lodepng_zlib_compress(unsigned char** out, size_t* outsize,
775 const unsigned char* in, size_t insize,
776 const LodePNGCompressSettings* settings);
777
778/*
779Find length-limited Huffman code for given frequencies. This function is in the
780public interface only for tests, it's used internally by lodepng_deflate.
781*/
782unsigned lodepng_huffman_code_lengths(unsigned* lengths, const unsigned* frequencies,
783 size_t numcodes, unsigned maxbitlen);
784
785/*Compress a buffer with deflate. See RFC 1951. Out buffer must be freed after use.*/
786unsigned lodepng_deflate(unsigned char** out, size_t* outsize,
787 const unsigned char* in, size_t insize,
788 const LodePNGCompressSettings* settings);
789
790#endif /*LODEPNG_COMPILE_ENCODER*/
791#endif /*LODEPNG_COMPILE_ZLIB*/
792
793#ifdef LODEPNG_COMPILE_DISK
794/*
795Load a file from disk into buffer. The function allocates the out buffer, and
796after usage you should free it.
797out: output parameter, contains pointer to loaded buffer.
798outsize: output parameter, size of the allocated out buffer
799filename: the path to the file to load
800return value: error code (0 means ok)
801*/
802unsigned lodepng_load_file(unsigned char** out, size_t* outsize, const char* filename);
803
804/*
805Save a file from buffer to disk. Warning, if it exists, this function overwrites
806the file without warning!
807buffer: the buffer to write
808buffersize: size of the buffer to write
809filename: the path to the file to save to
810return value: error code (0 means ok)
811*/
812unsigned lodepng_save_file(const unsigned char* buffer, size_t buffersize, const char* filename);
813#endif /*LODEPNG_COMPILE_DISK*/
814
815#ifdef LODEPNG_COMPILE_CPP
816/* The LodePNG C++ wrapper uses std::vectors instead of manually allocated memory buffers. */
817namespace lodepng
818{
819#ifdef LODEPNG_COMPILE_PNG
820class State : public LodePNGState
821{
822public:
823 State();
824 State(const State& other);
825 virtual ~State();
826 State& operator=(const State& other);
827};
828
829#ifdef LODEPNG_COMPILE_DECODER
830/* Same as other lodepng::decode, but using a State for more settings and information. */
831unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
832 State& state,
833 const unsigned char* in, size_t insize);
834unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
835 State& state,
836 const std::vector<unsigned char>& in);
837#endif /*LODEPNG_COMPILE_DECODER*/
838
839#ifdef LODEPNG_COMPILE_ENCODER
840/* Same as other lodepng::encode, but using a State for more settings and information. */
841unsigned encode(std::vector<unsigned char>& out,
842 const unsigned char* in, unsigned w, unsigned h,
843 State& state);
844unsigned encode(std::vector<unsigned char>& out,
845 const std::vector<unsigned char>& in, unsigned w, unsigned h,
846 State& state);
847#endif /*LODEPNG_COMPILE_ENCODER*/
848
849#ifdef LODEPNG_COMPILE_DISK
850/*
851Load a file from disk into an std::vector.
852return value: error code (0 means ok)
853*/
854unsigned load_file(std::vector<unsigned char>& buffer, const std::string& filename);
855
856/*
857Save the binary data in an std::vector to a file on disk. The file is overwritten
858without warning.
859*/
860unsigned save_file(const std::vector<unsigned char>& buffer, const std::string& filename);
861#endif /* LODEPNG_COMPILE_DISK */
862#endif /* LODEPNG_COMPILE_PNG */
863
864#ifdef LODEPNG_COMPILE_ZLIB
865#ifdef LODEPNG_COMPILE_DECODER
866/* Zlib-decompress an unsigned char buffer */
867unsigned decompress(std::vector<unsigned char>& out, const unsigned char* in, size_t insize,
868 const LodePNGDecompressSettings& settings = lodepng_default_decompress_settings);
869
870/* Zlib-decompress an std::vector */
871unsigned decompress(std::vector<unsigned char>& out, const std::vector<unsigned char>& in,
872 const LodePNGDecompressSettings& settings = lodepng_default_decompress_settings);
873#endif /* LODEPNG_COMPILE_DECODER */
874
875#ifdef LODEPNG_COMPILE_ENCODER
876/* Zlib-compress an unsigned char buffer */
877unsigned compress(std::vector<unsigned char>& out, const unsigned char* in, size_t insize,
878 const LodePNGCompressSettings& settings = lodepng_default_compress_settings);
879
880/* Zlib-compress an std::vector */
881unsigned compress(std::vector<unsigned char>& out, const std::vector<unsigned char>& in,
882 const LodePNGCompressSettings& settings = lodepng_default_compress_settings);
883#endif /* LODEPNG_COMPILE_ENCODER */
884#endif /* LODEPNG_COMPILE_ZLIB */
885} /* namespace lodepng */
886#endif /*LODEPNG_COMPILE_CPP*/
887
888/*
889TODO:
890[.] test if there are no memory leaks or security exploits - done a lot but needs to be checked often
891[.] check compatibility with various compilers - done but needs to be redone for every newer version
892[X] converting color to 16-bit per channel types
893[ ] read all public PNG chunk types (but never let the color profile and gamma ones touch RGB values)
894[ ] make sure encoder generates no chunks with size > (2^31)-1
895[ ] partial decoding (stream processing)
896[X] let the "isFullyOpaque" function check color keys and transparent palettes too
897[X] better name for the variables "codes", "codesD", "codelengthcodes", "clcl" and "lldl"
898[ ] don't stop decoding on errors like 69, 57, 58 (make warnings)
899[ ] let the C++ wrapper catch exceptions coming from the standard library and return LodePNG error codes
900[ ] allow user to provide custom color conversion functions, e.g. for premultiplied alpha, padding bits or not, ...
901[ ] allow user to give data (void*) to custom allocator
902*/
903
904#endif /*LODEPNG_H inclusion guard*/
905
906/*
907LodePNG Documentation
908---------------------
909
9100. table of contents
911--------------------
912
913 1. about
914 1.1. supported features
915 1.2. features not supported
916 2. C and C++ version
917 3. security
918 4. decoding
919 5. encoding
920 6. color conversions
921 6.1. PNG color types
922 6.2. color conversions
923 6.3. padding bits
924 6.4. A note about 16-bits per channel and endianness
925 7. error values
926 8. chunks and PNG editing
927 9. compiler support
928 10. examples
929 10.1. decoder C++ example
930 10.2. decoder C example
931 11. state settings reference
932 12. changes
933 13. contact information
934
935
9361. about
937--------
938
939PNG is a file format to store raster images losslessly with good compression,
940supporting different color types and alpha channel.
941
942LodePNG is a PNG codec according to the Portable Network Graphics (PNG)
943Specification (Second Edition) - W3C Recommendation 10 November 2003.
944
945The specifications used are:
946
947*) Portable Network Graphics (PNG) Specification (Second Edition):
948 http://www.w3.org/TR/2003/REC-PNG-20031110
949*) RFC 1950 ZLIB Compressed Data Format version 3.3:
950 http://www.gzip.org/zlib/rfc-zlib.html
951*) RFC 1951 DEFLATE Compressed Data Format Specification ver 1.3:
952 http://www.gzip.org/zlib/rfc-deflate.html
953
954The most recent version of LodePNG can currently be found at
955http://lodev.org/lodepng/
956
957LodePNG works both in C (ISO C90) and C++, with a C++ wrapper that adds
958extra functionality.
959
960LodePNG exists out of two files:
961-lodepng.h: the header file for both C and C++
962-lodepng.c(pp): give it the name lodepng.c or lodepng.cpp (or .cc) depending on your usage
963
964If you want to start using LodePNG right away without reading this doc, get the
965examples from the LodePNG website to see how to use it in code, or check the
966smaller examples in chapter 13 here.
967
968LodePNG is simple but only supports the basic requirements. To achieve
969simplicity, the following design choices were made: There are no dependencies
970on any external library. There are functions to decode and encode a PNG with
971a single function call, and extended versions of these functions taking a
972LodePNGState struct allowing to specify or get more information. By default
973the colors of the raw image are always RGB or RGBA, no matter what color type
974the PNG file uses. To read and write files, there are simple functions to
975convert the files to/from buffers in memory.
976
977This all makes LodePNG suitable for loading textures in games, demos and small
978programs, ... It's less suitable for full fledged image editors, loading PNGs
979over network (it requires all the image data to be available before decoding can
980begin), life-critical systems, ...
981
9821.1. supported features
983-----------------------
984
985The following features are supported by the decoder:
986
987*) decoding of PNGs with any color type, bit depth and interlace mode, to a 24- or 32-bit color raw image,
988 or the same color type as the PNG
989*) encoding of PNGs, from any raw image to 24- or 32-bit color, or the same color type as the raw image
990*) Adam7 interlace and deinterlace for any color type
991*) loading the image from harddisk or decoding it from a buffer from other sources than harddisk
992*) support for alpha channels, including RGBA color model, translucent palettes and color keying
993*) zlib decompression (inflate)
994*) zlib compression (deflate)
995*) CRC32 and ADLER32 checksums
996*) handling of unknown chunks, allowing making a PNG editor that stores custom and unknown chunks.
997*) the following chunks are supported (generated/interpreted) by both encoder and decoder:
998 IHDR: header information
999 PLTE: color palette
1000 IDAT: pixel data
1001 IEND: the final chunk
1002 tRNS: transparency for palettized images
1003 tEXt: textual information
1004 zTXt: compressed textual information
1005 iTXt: international textual information
1006 bKGD: suggested background color
1007 pHYs: physical dimensions
1008 tIME: modification time
1009
10101.2. features not supported
1011---------------------------
1012
1013The following features are _not_ supported:
1014
1015*) some features needed to make a conformant PNG-Editor might be still missing.
1016*) partial loading/stream processing. All data must be available and is processed in one call.
1017*) The following public chunks are not supported but treated as unknown chunks by LodePNG
1018 cHRM, gAMA, iCCP, sRGB, sBIT, hIST, sPLT
1019 Some of these are not supported on purpose: LodePNG wants to provide the RGB values
1020 stored in the pixels, not values modified by system dependent gamma or color models.
1021
1022
10232. C and C++ version
1024--------------------
1025
1026The C version uses buffers allocated with alloc that you need to free()
1027yourself. You need to use init and cleanup functions for each struct whenever
1028using a struct from the C version to avoid exploits and memory leaks.
1029
1030The C++ version has extra functions with std::vectors in the interface and the
1031lodepng::State class which is a LodePNGState with constructor and destructor.
1032
1033These files work without modification for both C and C++ compilers because all
1034the additional C++ code is in "#ifdef __cplusplus" blocks that make C-compilers
1035ignore it, and the C code is made to compile both with strict ISO C90 and C++.
1036
1037To use the C++ version, you need to rename the source file to lodepng.cpp
1038(instead of lodepng.c), and compile it with a C++ compiler.
1039
1040To use the C version, you need to rename the source file to lodepng.c (instead
1041of lodepng.cpp), and compile it with a C compiler.
1042
1043
10443. Security
1045-----------
1046
1047Even if carefully designed, it's always possible that LodePNG contains possible
1048exploits. If you discover one, please let me know, and it will be fixed.
1049
1050When using LodePNG, care has to be taken with the C version of LodePNG, as well
1051as the C-style structs when working with C++. The following conventions are used
1052for all C-style structs:
1053
1054-if a struct has a corresponding init function, always call the init function when making a new one
1055-if a struct has a corresponding cleanup function, call it before the struct disappears to avoid memory leaks
1056-if a struct has a corresponding copy function, use the copy function instead of "=".
1057 The destination must also be inited already.
1058
1059
10604. Decoding
1061-----------
1062
1063Decoding converts a PNG compressed image to a raw pixel buffer.
1064
1065Most documentation on using the decoder is at its declarations in the header
1066above. For C, simple decoding can be done with functions such as
1067lodepng_decode32, and more advanced decoding can be done with the struct
1068LodePNGState and lodepng_decode. For C++, all decoding can be done with the
1069various lodepng::decode functions, and lodepng::State can be used for advanced
1070features.
1071
1072When using the LodePNGState, it uses the following fields for decoding:
1073*) LodePNGInfo info_png: it stores extra information about the PNG (the input) in here
1074*) LodePNGColorMode info_raw: here you can say what color mode of the raw image (the output) you want to get
1075*) LodePNGDecoderSettings decoder: you can specify a few extra settings for the decoder to use
1076
1077LodePNGInfo info_png
1078--------------------
1079
1080After decoding, this contains extra information of the PNG image, except the actual
1081pixels, width and height because these are already gotten directly from the decoder
1082functions.
1083
1084It contains for example the original color type of the PNG image, text comments,
1085suggested background color, etc... More details about the LodePNGInfo struct are
1086at its declaration documentation.
1087
1088LodePNGColorMode info_raw
1089-------------------------
1090
1091When decoding, here you can specify which color type you want
1092the resulting raw image to be. If this is different from the colortype of the
1093PNG, then the decoder will automatically convert the result. This conversion
1094always works, except if you want it to convert a color PNG to greyscale or to
1095a palette with missing colors.
1096
1097By default, 32-bit color is used for the result.
1098
1099LodePNGDecoderSettings decoder
1100------------------------------
1101
1102The settings can be used to ignore the errors created by invalid CRC and Adler32
1103chunks, and to disable the decoding of tEXt chunks.
1104
1105There's also a setting color_convert, true by default. If false, no conversion
1106is done, the resulting data will be as it was in the PNG (after decompression)
1107and you'll have to puzzle the colors of the pixels together yourself using the
1108color type information in the LodePNGInfo.
1109
1110
11115. Encoding
1112-----------
1113
1114Encoding converts a raw pixel buffer to a PNG compressed image.
1115
1116Most documentation on using the encoder is at its declarations in the header
1117above. For C, simple encoding can be done with functions such as
1118lodepng_encode32, and more advanced decoding can be done with the struct
1119LodePNGState and lodepng_encode. For C++, all encoding can be done with the
1120various lodepng::encode functions, and lodepng::State can be used for advanced
1121features.
1122
1123Like the decoder, the encoder can also give errors. However it gives less errors
1124since the encoder input is trusted, the decoder input (a PNG image that could
1125be forged by anyone) is not trusted.
1126
1127When using the LodePNGState, it uses the following fields for encoding:
1128*) LodePNGInfo info_png: here you specify how you want the PNG (the output) to be.
1129*) LodePNGColorMode info_raw: here you say what color type of the raw image (the input) has
1130*) LodePNGEncoderSettings encoder: you can specify a few settings for the encoder to use
1131
1132LodePNGInfo info_png
1133--------------------
1134
1135When encoding, you use this the opposite way as when decoding: for encoding,
1136you fill in the values you want the PNG to have before encoding. By default it's
1137not needed to specify a color type for the PNG since it's automatically chosen,
1138but it's possible to choose it yourself given the right settings.
1139
1140The encoder will not always exactly match the LodePNGInfo struct you give,
1141it tries as close as possible. Some things are ignored by the encoder. The
1142encoder uses, for example, the following settings from it when applicable:
1143colortype and bitdepth, text chunks, time chunk, the color key, the palette, the
1144background color, the interlace method, unknown chunks, ...
1145
1146When encoding to a PNG with colortype 3, the encoder will generate a PLTE chunk.
1147If the palette contains any colors for which the alpha channel is not 255 (so
1148there are translucent colors in the palette), it'll add a tRNS chunk.
1149
1150LodePNGColorMode info_raw
1151-------------------------
1152
1153You specify the color type of the raw image that you give to the input here,
1154including a possible transparent color key and palette you happen to be using in
1155your raw image data.
1156
1157By default, 32-bit color is assumed, meaning your input has to be in RGBA
1158format with 4 bytes (unsigned chars) per pixel.
1159
1160LodePNGEncoderSettings encoder
1161------------------------------
1162
1163The following settings are supported (some are in sub-structs):
1164*) auto_convert: when this option is enabled, the encoder will
1165automatically choose the smallest possible color mode (including color key) that
1166can encode the colors of all pixels without information loss.
1167*) btype: the block type for LZ77. 0 = uncompressed, 1 = fixed huffman tree,
1168 2 = dynamic huffman tree (best compression). Should be 2 for proper
1169 compression.
1170*) use_lz77: whether or not to use LZ77 for compressed block types. Should be
1171 true for proper compression.
1172*) windowsize: the window size used by the LZ77 encoder (1 - 32768). Has value
1173 2048 by default, but can be set to 32768 for better, but slow, compression.
1174*) force_palette: if colortype is 2 or 6, you can make the encoder write a PLTE
1175 chunk if force_palette is true. This can used as suggested palette to convert
1176 to by viewers that don't support more than 256 colors (if those still exist)
1177*) add_id: add text chunk "Encoder: LodePNG <version>" to the image.
1178*) text_compression: default 1. If 1, it'll store texts as zTXt instead of tEXt chunks.
1179 zTXt chunks use zlib compression on the text. This gives a smaller result on
1180 large texts but a larger result on small texts (such as a single program name).
1181 It's all tEXt or all zTXt though, there's no separate setting per text yet.
1182
1183
11846. color conversions
1185--------------------
1186
1187An important thing to note about LodePNG, is that the color type of the PNG, and
1188the color type of the raw image, are completely independent. By default, when
1189you decode a PNG, you get the result as a raw image in the color type you want,
1190no matter whether the PNG was encoded with a palette, greyscale or RGBA color.
1191And if you encode an image, by default LodePNG will automatically choose the PNG
1192color type that gives good compression based on the values of colors and amount
1193of colors in the image. It can be configured to let you control it instead as
1194well, though.
1195
1196To be able to do this, LodePNG does conversions from one color mode to another.
1197It can convert from almost any color type to any other color type, except the
1198following conversions: RGB to greyscale is not supported, and converting to a
1199palette when the palette doesn't have a required color is not supported. This is
1200not supported on purpose: this is information loss which requires a color
1201reduction algorithm that is beyong the scope of a PNG encoder (yes, RGB to grey
1202is easy, but there are multiple ways if you want to give some channels more
1203weight).
1204
1205By default, when decoding, you get the raw image in 32-bit RGBA or 24-bit RGB
1206color, no matter what color type the PNG has. And by default when encoding,
1207LodePNG automatically picks the best color model for the output PNG, and expects
1208the input image to be 32-bit RGBA or 24-bit RGB. So, unless you want to control
1209the color format of the images yourself, you can skip this chapter.
1210
12116.1. PNG color types
1212--------------------
1213
1214A PNG image can have many color types, ranging from 1-bit color to 64-bit color,
1215as well as palettized color modes. After the zlib decompression and unfiltering
1216in the PNG image is done, the raw pixel data will have that color type and thus
1217a certain amount of bits per pixel. If you want the output raw image after
1218decoding to have another color type, a conversion is done by LodePNG.
1219
1220The PNG specification gives the following color types:
1221
12220: greyscale, bit depths 1, 2, 4, 8, 16
12232: RGB, bit depths 8 and 16
12243: palette, bit depths 1, 2, 4 and 8
12254: greyscale with alpha, bit depths 8 and 16
12266: RGBA, bit depths 8 and 16
1227
1228Bit depth is the amount of bits per pixel per color channel. So the total amount
1229of bits per pixel is: amount of channels * bitdepth.
1230
12316.2. color conversions
1232----------------------
1233
1234As explained in the sections about the encoder and decoder, you can specify
1235color types and bit depths in info_png and info_raw to change the default
1236behaviour.
1237
1238If, when decoding, you want the raw image to be something else than the default,
1239you need to set the color type and bit depth you want in the LodePNGColorMode,
1240or the parameters colortype and bitdepth of the simple decoding function.
1241
1242If, when encoding, you use another color type than the default in the raw input
1243image, you need to specify its color type and bit depth in the LodePNGColorMode
1244of the raw image, or use the parameters colortype and bitdepth of the simple
1245encoding function.
1246
1247If, when encoding, you don't want LodePNG to choose the output PNG color type
1248but control it yourself, you need to set auto_convert in the encoder settings
1249to false, and specify the color type you want in the LodePNGInfo of the
1250encoder (including palette: it can generate a palette if auto_convert is true,
1251otherwise not).
1252
1253If the input and output color type differ (whether user chosen or auto chosen),
1254LodePNG will do a color conversion, which follows the rules below, and may
1255sometimes result in an error.
1256
1257To avoid some confusion:
1258-the decoder converts from PNG to raw image
1259-the encoder converts from raw image to PNG
1260-the colortype and bitdepth in LodePNGColorMode info_raw, are those of the raw image
1261-the colortype and bitdepth in the color field of LodePNGInfo info_png, are those of the PNG
1262-when encoding, the color type in LodePNGInfo is ignored if auto_convert
1263 is enabled, it is automatically generated instead
1264-when decoding, the color type in LodePNGInfo is set by the decoder to that of the original
1265 PNG image, but it can be ignored since the raw image has the color type you requested instead
1266-if the color type of the LodePNGColorMode and PNG image aren't the same, a conversion
1267 between the color types is done if the color types are supported. If it is not
1268 supported, an error is returned. If the types are the same, no conversion is done.
1269-even though some conversions aren't supported, LodePNG supports loading PNGs from any
1270 colortype and saving PNGs to any colortype, sometimes it just requires preparing
1271 the raw image correctly before encoding.
1272-both encoder and decoder use the same color converter.
1273
1274Non supported color conversions:
1275-color to greyscale: no error is thrown, but the result will look ugly because
1276only the red channel is taken
1277-anything to palette when that palette does not have that color in it: in this
1278case an error is thrown
1279
1280Supported color conversions:
1281-anything to 8-bit RGB, 8-bit RGBA, 16-bit RGB, 16-bit RGBA
1282-any grey or grey+alpha, to grey or grey+alpha
1283-anything to a palette, as long as the palette has the requested colors in it
1284-removing alpha channel
1285-higher to smaller bitdepth, and vice versa
1286
1287If you want no color conversion to be done (e.g. for speed or control):
1288-In the encoder, you can make it save a PNG with any color type by giving the
1289raw color mode and LodePNGInfo the same color mode, and setting auto_convert to
1290false.
1291-In the decoder, you can make it store the pixel data in the same color type
1292as the PNG has, by setting the color_convert setting to false. Settings in
1293info_raw are then ignored.
1294
1295The function lodepng_convert does the color conversion. It is available in the
1296interface but normally isn't needed since the encoder and decoder already call
1297it.
1298
12996.3. padding bits
1300-----------------
1301
1302In the PNG file format, if a less than 8-bit per pixel color type is used and the scanlines
1303have a bit amount that isn't a multiple of 8, then padding bits are used so that each
1304scanline starts at a fresh byte. But that is NOT true for the LodePNG raw input and output.
1305The raw input image you give to the encoder, and the raw output image you get from the decoder
1306will NOT have these padding bits, e.g. in the case of a 1-bit image with a width
1307of 7 pixels, the first pixel of the second scanline will the the 8th bit of the first byte,
1308not the first bit of a new byte.
1309
13106.4. A note about 16-bits per channel and endianness
1311----------------------------------------------------
1312
1313LodePNG uses unsigned char arrays for 16-bit per channel colors too, just like
1314for any other color format. The 16-bit values are stored in big endian (most
1315significant byte first) in these arrays. This is the opposite order of the
1316little endian used by x86 CPU's.
1317
1318LodePNG always uses big endian because the PNG file format does so internally.
1319Conversions to other formats than PNG uses internally are not supported by
1320LodePNG on purpose, there are myriads of formats, including endianness of 16-bit
1321colors, the order in which you store R, G, B and A, and so on. Supporting and
1322converting to/from all that is outside the scope of LodePNG.
1323
1324This may mean that, depending on your use case, you may want to convert the big
1325endian output of LodePNG to little endian with a for loop. This is certainly not
1326always needed, many applications and libraries support big endian 16-bit colors
1327anyway, but it means you cannot simply cast the unsigned char* buffer to an
1328unsigned short* buffer on x86 CPUs.
1329
1330
13317. error values
1332---------------
1333
1334All functions in LodePNG that return an error code, return 0 if everything went
1335OK, or a non-zero code if there was an error.
1336
1337The meaning of the LodePNG error values can be retrieved with the function
1338lodepng_error_text: given the numerical error code, it returns a description
1339of the error in English as a string.
1340
1341Check the implementation of lodepng_error_text to see the meaning of each code.
1342
1343
13448. chunks and PNG editing
1345-------------------------
1346
1347If you want to add extra chunks to a PNG you encode, or use LodePNG for a PNG
1348editor that should follow the rules about handling of unknown chunks, or if your
1349program is able to read other types of chunks than the ones handled by LodePNG,
1350then that's possible with the chunk functions of LodePNG.
1351
1352A PNG chunk has the following layout:
1353
13544 bytes length
13554 bytes type name
1356length bytes data
13574 bytes CRC
1358
13598.1. iterating through chunks
1360-----------------------------
1361
1362If you have a buffer containing the PNG image data, then the first chunk (the
1363IHDR chunk) starts at byte number 8 of that buffer. The first 8 bytes are the
1364signature of the PNG and are not part of a chunk. But if you start at byte 8
1365then you have a chunk, and can check the following things of it.
1366
1367NOTE: none of these functions check for memory buffer boundaries. To avoid
1368exploits, always make sure the buffer contains all the data of the chunks.
1369When using lodepng_chunk_next, make sure the returned value is within the
1370allocated memory.
1371
1372unsigned lodepng_chunk_length(const unsigned char* chunk):
1373
1374Get the length of the chunk's data. The total chunk length is this length + 12.
1375
1376void lodepng_chunk_type(char type[5], const unsigned char* chunk):
1377unsigned char lodepng_chunk_type_equals(const unsigned char* chunk, const char* type):
1378
1379Get the type of the chunk or compare if it's a certain type
1380
1381unsigned char lodepng_chunk_critical(const unsigned char* chunk):
1382unsigned char lodepng_chunk_private(const unsigned char* chunk):
1383unsigned char lodepng_chunk_safetocopy(const unsigned char* chunk):
1384
1385Check if the chunk is critical in the PNG standard (only IHDR, PLTE, IDAT and IEND are).
1386Check if the chunk is private (public chunks are part of the standard, private ones not).
1387Check if the chunk is safe to copy. If it's not, then, when modifying data in a critical
1388chunk, unsafe to copy chunks of the old image may NOT be saved in the new one if your
1389program doesn't handle that type of unknown chunk.
1390
1391unsigned char* lodepng_chunk_data(unsigned char* chunk):
1392const unsigned char* lodepng_chunk_data_const(const unsigned char* chunk):
1393
1394Get a pointer to the start of the data of the chunk.
1395
1396unsigned lodepng_chunk_check_crc(const unsigned char* chunk):
1397void lodepng_chunk_generate_crc(unsigned char* chunk):
1398
1399Check if the crc is correct or generate a correct one.
1400
1401unsigned char* lodepng_chunk_next(unsigned char* chunk):
1402const unsigned char* lodepng_chunk_next_const(const unsigned char* chunk):
1403
1404Iterate to the next chunk. This works if you have a buffer with consecutive chunks. Note that these
1405functions do no boundary checking of the allocated data whatsoever, so make sure there is enough
1406data available in the buffer to be able to go to the next chunk.
1407
1408unsigned lodepng_chunk_append(unsigned char** out, size_t* outlength, const unsigned char* chunk):
1409unsigned lodepng_chunk_create(unsigned char** out, size_t* outlength, unsigned length,
1410 const char* type, const unsigned char* data):
1411
1412These functions are used to create new chunks that are appended to the data in *out that has
1413length *outlength. The append function appends an existing chunk to the new data. The create
1414function creates a new chunk with the given parameters and appends it. Type is the 4-letter
1415name of the chunk.
1416
14178.2. chunks in info_png
1418-----------------------
1419
1420The LodePNGInfo struct contains fields with the unknown chunk in it. It has 3
1421buffers (each with size) to contain 3 types of unknown chunks:
1422the ones that come before the PLTE chunk, the ones that come between the PLTE
1423and the IDAT chunks, and the ones that come after the IDAT chunks.
1424It's necessary to make the distionction between these 3 cases because the PNG
1425standard forces to keep the ordering of unknown chunks compared to the critical
1426chunks, but does not force any other ordering rules.
1427
1428info_png.unknown_chunks_data[0] is the chunks before PLTE
1429info_png.unknown_chunks_data[1] is the chunks after PLTE, before IDAT
1430info_png.unknown_chunks_data[2] is the chunks after IDAT
1431
1432The chunks in these 3 buffers can be iterated through and read by using the same
1433way described in the previous subchapter.
1434
1435When using the decoder to decode a PNG, you can make it store all unknown chunks
1436if you set the option settings.remember_unknown_chunks to 1. By default, this
1437option is off (0).
1438
1439The encoder will always encode unknown chunks that are stored in the info_png.
1440If you need it to add a particular chunk that isn't known by LodePNG, you can
1441use lodepng_chunk_append or lodepng_chunk_create to the chunk data in
1442info_png.unknown_chunks_data[x].
1443
1444Chunks that are known by LodePNG should not be added in that way. E.g. to make
1445LodePNG add a bKGD chunk, set background_defined to true and add the correct
1446parameters there instead.
1447
1448
14499. compiler support
1450-------------------
1451
1452No libraries other than the current standard C library are needed to compile
1453LodePNG. For the C++ version, only the standard C++ library is needed on top.
1454Add the files lodepng.c(pp) and lodepng.h to your project, include
1455lodepng.h where needed, and your program can read/write PNG files.
1456
1457It is compatible with C90 and up, and C++03 and up.
1458
1459If performance is important, use optimization when compiling! For both the
1460encoder and decoder, this makes a large difference.
1461
1462Make sure that LodePNG is compiled with the same compiler of the same version
1463and with the same settings as the rest of the program, or the interfaces with
1464std::vectors and std::strings in C++ can be incompatible.
1465
1466CHAR_BITS must be 8 or higher, because LodePNG uses unsigned chars for octets.
1467
1468*) gcc and g++
1469
1470LodePNG is developed in gcc so this compiler is natively supported. It gives no
1471warnings with compiler options "-Wall -Wextra -pedantic -ansi", with gcc and g++
1472version 4.7.1 on Linux, 32-bit and 64-bit.
1473
1474*) Clang
1475
1476Fully supported and warning-free.
1477
1478*) Mingw
1479
1480The Mingw compiler (a port of gcc for Windows) should be fully supported by
1481LodePNG.
1482
1483*) Visual Studio and Visual C++ Express Edition
1484
1485LodePNG should be warning-free with warning level W4. Two warnings were disabled
1486with pragmas though: warning 4244 about implicit conversions, and warning 4996
1487where it wants to use a non-standard function fopen_s instead of the standard C
1488fopen.
1489
1490Visual Studio may want "stdafx.h" files to be included in each source file and
1491give an error "unexpected end of file while looking for precompiled header".
1492This is not standard C++ and will not be added to the stock LodePNG. You can
1493disable it for lodepng.cpp only by right clicking it, Properties, C/C++,
1494Precompiled Headers, and set it to Not Using Precompiled Headers there.
1495
1496NOTE: Modern versions of VS should be fully supported, but old versions, e.g.
1497VS6, are not guaranteed to work.
1498
1499*) Compilers on Macintosh
1500
1501LodePNG has been reported to work both with gcc and LLVM for Macintosh, both for
1502C and C++.
1503
1504*) Other Compilers
1505
1506If you encounter problems on any compilers, feel free to let me know and I may
1507try to fix it if the compiler is modern and standards complient.
1508
1509
151010. examples
1511------------
1512
1513This decoder example shows the most basic usage of LodePNG. More complex
1514examples can be found on the LodePNG website.
1515
151610.1. decoder C++ example
1517-------------------------
1518
1519#include "lodepng.h"
1520#include <iostream>
1521
1522int main(int argc, char *argv[])
1523{
1524 const char* filename = argc > 1 ? argv[1] : "test.png";
1525
1526 //load and decode
1527 std::vector<unsigned char> image;
1528 unsigned width, height;
1529 unsigned error = lodepng::decode(image, width, height, filename);
1530
1531 //if there's an error, display it
1532 if(error) std::cout << "decoder error " << error << ": " << lodepng_error_text(error) << std::endl;
1533
1534 //the pixels are now in the vector "image", 4 bytes per pixel, ordered RGBARGBA..., use it as texture, draw it, ...
1535}
1536
153710.2. decoder C example
1538-----------------------
1539
1540#include "lodepng.h"
1541
1542int main(int argc, char *argv[])
1543{
1544 unsigned error;
1545 unsigned char* image;
1546 size_t width, height;
1547 const char* filename = argc > 1 ? argv[1] : "test.png";
1548
1549 error = lodepng_decode32_file(&image, &width, &height, filename);
1550
1551 if(error) printf("decoder error %u: %s\n", error, lodepng_error_text(error));
1552
1553 / * use image here * /
1554
1555 free(image);
1556 return 0;
1557}
1558
155911. state settings reference
1560----------------------------
1561
1562A quick reference of some settings to set on the LodePNGState
1563
1564For decoding:
1565
1566state.decoder.zlibsettings.ignore_adler32: ignore ADLER32 checksums
1567state.decoder.zlibsettings.custom_...: use custom inflate function
1568state.decoder.ignore_crc: ignore CRC checksums
1569state.decoder.color_convert: convert internal PNG color to chosen one
1570state.decoder.read_text_chunks: whether to read in text metadata chunks
1571state.decoder.remember_unknown_chunks: whether to read in unknown chunks
1572state.info_raw.colortype: desired color type for decoded image
1573state.info_raw.bitdepth: desired bit depth for decoded image
1574state.info_raw....: more color settings, see struct LodePNGColorMode
1575state.info_png....: no settings for decoder but ouput, see struct LodePNGInfo
1576
1577For encoding:
1578
1579state.encoder.zlibsettings.btype: disable compression by setting it to 0
1580state.encoder.zlibsettings.use_lz77: use LZ77 in compression
1581state.encoder.zlibsettings.windowsize: tweak LZ77 windowsize
1582state.encoder.zlibsettings.minmatch: tweak min LZ77 length to match
1583state.encoder.zlibsettings.nicematch: tweak LZ77 match where to stop searching
1584state.encoder.zlibsettings.lazymatching: try one more LZ77 matching
1585state.encoder.zlibsettings.custom_...: use custom deflate function
1586state.encoder.auto_convert: choose optimal PNG color type, if 0 uses info_png
1587state.encoder.filter_palette_zero: PNG filter strategy for palette
1588state.encoder.filter_strategy: PNG filter strategy to encode with
1589state.encoder.force_palette: add palette even if not encoding to one
1590state.encoder.add_id: add LodePNG identifier and version as a text chunk
1591state.encoder.text_compression: use compressed text chunks for metadata
1592state.info_raw.colortype: color type of raw input image you provide
1593state.info_raw.bitdepth: bit depth of raw input image you provide
1594state.info_raw: more color settings, see struct LodePNGColorMode
1595state.info_png.color.colortype: desired color type if auto_convert is false
1596state.info_png.color.bitdepth: desired bit depth if auto_convert is false
1597state.info_png.color....: more color settings, see struct LodePNGColorMode
1598state.info_png....: more PNG related settings, see struct LodePNGInfo
1599
1600
160112. changes
1602-----------
1603
1604The version number of LodePNG is the date of the change given in the format
1605yyyymmdd.
1606
1607Some changes aren't backwards compatible. Those are indicated with a (!)
1608symbol.
1609
1610*) 08 dec 2015: Made load_file function return error if file can't be opened.
1611*) 24 okt 2015: Bugfix with decoding to palette output.
1612*) 18 apr 2015: Boundary PM instead of just package-merge for faster encoding.
1613*) 23 aug 2014: Reduced needless memory usage of decoder.
1614*) 28 jun 2014: Removed fix_png setting, always support palette OOB for
1615 simplicity. Made ColorProfile public.
1616*) 09 jun 2014: Faster encoder by fixing hash bug and more zeros optimization.
1617*) 22 dec 2013: Power of two windowsize required for optimization.
1618*) 15 apr 2013: Fixed bug with LAC_ALPHA and color key.
1619*) 25 mar 2013: Added an optional feature to ignore some PNG errors (fix_png).
1620*) 11 mar 2013 (!): Bugfix with custom free. Changed from "my" to "lodepng_"
1621 prefix for the custom allocators and made it possible with a new #define to
1622 use custom ones in your project without needing to change lodepng's code.
1623*) 28 jan 2013: Bugfix with color key.
1624*) 27 okt 2012: Tweaks in text chunk keyword length error handling.
1625*) 8 okt 2012 (!): Added new filter strategy (entropy) and new auto color mode.
1626 (no palette). Better deflate tree encoding. New compression tweak settings.
1627 Faster color conversions while decoding. Some internal cleanups.
1628*) 23 sep 2012: Reduced warnings in Visual Studio a little bit.
1629*) 1 sep 2012 (!): Removed #define's for giving custom (de)compression functions
1630 and made it work with function pointers instead.
1631*) 23 jun 2012: Added more filter strategies. Made it easier to use custom alloc
1632 and free functions and toggle #defines from compiler flags. Small fixes.
1633*) 6 may 2012 (!): Made plugging in custom zlib/deflate functions more flexible.
1634*) 22 apr 2012 (!): Made interface more consistent, renaming a lot. Removed
1635 redundant C++ codec classes. Reduced amount of structs. Everything changed,
1636 but it is cleaner now imho and functionality remains the same. Also fixed
1637 several bugs and shrunk the implementation code. Made new samples.
1638*) 6 nov 2011 (!): By default, the encoder now automatically chooses the best
1639 PNG color model and bit depth, based on the amount and type of colors of the
1640 raw image. For this, autoLeaveOutAlphaChannel replaced by auto_choose_color.
1641*) 9 okt 2011: simpler hash chain implementation for the encoder.
1642*) 8 sep 2011: lz77 encoder lazy matching instead of greedy matching.
1643*) 23 aug 2011: tweaked the zlib compression parameters after benchmarking.
1644 A bug with the PNG filtertype heuristic was fixed, so that it chooses much
1645 better ones (it's quite significant). A setting to do an experimental, slow,
1646 brute force search for PNG filter types is added.
1647*) 17 aug 2011 (!): changed some C zlib related function names.
1648*) 16 aug 2011: made the code less wide (max 120 characters per line).
1649*) 17 apr 2011: code cleanup. Bugfixes. Convert low to 16-bit per sample colors.
1650*) 21 feb 2011: fixed compiling for C90. Fixed compiling with sections disabled.
1651*) 11 dec 2010: encoding is made faster, based on suggestion by Peter Eastman
1652 to optimize long sequences of zeros.
1653*) 13 nov 2010: added LodePNG_InfoColor_hasPaletteAlpha and
1654 LodePNG_InfoColor_canHaveAlpha functions for convenience.
1655*) 7 nov 2010: added LodePNG_error_text function to get error code description.
1656*) 30 okt 2010: made decoding slightly faster
1657*) 26 okt 2010: (!) changed some C function and struct names (more consistent).
1658 Reorganized the documentation and the declaration order in the header.
1659*) 08 aug 2010: only changed some comments and external samples.
1660*) 05 jul 2010: fixed bug thanks to warnings in the new gcc version.
1661*) 14 mar 2010: fixed bug where too much memory was allocated for char buffers.
1662*) 02 sep 2008: fixed bug where it could create empty tree that linux apps could
1663 read by ignoring the problem but windows apps couldn't.
1664*) 06 jun 2008: added more error checks for out of memory cases.
1665*) 26 apr 2008: added a few more checks here and there to ensure more safety.
1666*) 06 mar 2008: crash with encoding of strings fixed
1667*) 02 feb 2008: support for international text chunks added (iTXt)
1668*) 23 jan 2008: small cleanups, and #defines to divide code in sections
1669*) 20 jan 2008: support for unknown chunks allowing using LodePNG for an editor.
1670*) 18 jan 2008: support for tIME and pHYs chunks added to encoder and decoder.
1671*) 17 jan 2008: ability to encode and decode compressed zTXt chunks added
1672 Also various fixes, such as in the deflate and the padding bits code.
1673*) 13 jan 2008: Added ability to encode Adam7-interlaced images. Improved
1674 filtering code of encoder.
1675*) 07 jan 2008: (!) changed LodePNG to use ISO C90 instead of C++. A
1676 C++ wrapper around this provides an interface almost identical to before.
1677 Having LodePNG be pure ISO C90 makes it more portable. The C and C++ code
1678 are together in these files but it works both for C and C++ compilers.
1679*) 29 dec 2007: (!) changed most integer types to unsigned int + other tweaks
1680*) 30 aug 2007: bug fixed which makes this Borland C++ compatible
1681*) 09 aug 2007: some VS2005 warnings removed again
1682*) 21 jul 2007: deflate code placed in new namespace separate from zlib code
1683*) 08 jun 2007: fixed bug with 2- and 4-bit color, and small interlaced images
1684*) 04 jun 2007: improved support for Visual Studio 2005: crash with accessing
1685 invalid std::vector element [0] fixed, and level 3 and 4 warnings removed
1686*) 02 jun 2007: made the encoder add a tag with version by default
1687*) 27 may 2007: zlib and png code separated (but still in the same file),
1688 simple encoder/decoder functions added for more simple usage cases
1689*) 19 may 2007: minor fixes, some code cleaning, new error added (error 69),
1690 moved some examples from here to lodepng_examples.cpp
1691*) 12 may 2007: palette decoding bug fixed
1692*) 24 apr 2007: changed the license from BSD to the zlib license
1693*) 11 mar 2007: very simple addition: ability to encode bKGD chunks.
1694*) 04 mar 2007: (!) tEXt chunk related fixes, and support for encoding
1695 palettized PNG images. Plus little interface change with palette and texts.
1696*) 03 mar 2007: Made it encode dynamic Huffman shorter with repeat codes.
1697 Fixed a bug where the end code of a block had length 0 in the Huffman tree.
1698*) 26 feb 2007: Huffman compression with dynamic trees (BTYPE 2) now implemented
1699 and supported by the encoder, resulting in smaller PNGs at the output.
1700*) 27 jan 2007: Made the Adler-32 test faster so that a timewaste is gone.
1701*) 24 jan 2007: gave encoder an error interface. Added color conversion from any
1702 greyscale type to 8-bit greyscale with or without alpha.
1703*) 21 jan 2007: (!) Totally changed the interface. It allows more color types
1704 to convert to and is more uniform. See the manual for how it works now.
1705*) 07 jan 2007: Some cleanup & fixes, and a few changes over the last days:
1706 encode/decode custom tEXt chunks, separate classes for zlib & deflate, and
1707 at last made the decoder give errors for incorrect Adler32 or Crc.
1708*) 01 jan 2007: Fixed bug with encoding PNGs with less than 8 bits per channel.
1709*) 29 dec 2006: Added support for encoding images without alpha channel, and
1710 cleaned out code as well as making certain parts faster.
1711*) 28 dec 2006: Added "Settings" to the encoder.
1712*) 26 dec 2006: The encoder now does LZ77 encoding and produces much smaller files now.
1713 Removed some code duplication in the decoder. Fixed little bug in an example.
1714*) 09 dec 2006: (!) Placed output parameters of public functions as first parameter.
1715 Fixed a bug of the decoder with 16-bit per color.
1716*) 15 okt 2006: Changed documentation structure
1717*) 09 okt 2006: Encoder class added. It encodes a valid PNG image from the
1718 given image buffer, however for now it's not compressed.
1719*) 08 sep 2006: (!) Changed to interface with a Decoder class
1720*) 30 jul 2006: (!) LodePNG_InfoPng , width and height are now retrieved in different
1721 way. Renamed decodePNG to decodePNGGeneric.
1722*) 29 jul 2006: (!) Changed the interface: image info is now returned as a
1723 struct of type LodePNG::LodePNG_Info, instead of a vector, which was a bit clumsy.
1724*) 28 jul 2006: Cleaned the code and added new error checks.
1725 Corrected terminology "deflate" into "inflate".
1726*) 23 jun 2006: Added SDL example in the documentation in the header, this
1727 example allows easy debugging by displaying the PNG and its transparency.
1728*) 22 jun 2006: (!) Changed way to obtain error value. Added
1729 loadFile function for convenience. Made decodePNG32 faster.
1730*) 21 jun 2006: (!) Changed type of info vector to unsigned.
1731 Changed position of palette in info vector. Fixed an important bug that
1732 happened on PNGs with an uncompressed block.
1733*) 16 jun 2006: Internally changed unsigned into unsigned where
1734 needed, and performed some optimizations.
1735*) 07 jun 2006: (!) Renamed functions to decodePNG and placed them
1736 in LodePNG namespace. Changed the order of the parameters. Rewrote the
1737 documentation in the header. Renamed files to lodepng.cpp and lodepng.h
1738*) 22 apr 2006: Optimized and improved some code
1739*) 07 sep 2005: (!) Changed to std::vector interface
1740*) 12 aug 2005: Initial release (C++, decoder only)
1741
1742
174313. contact information
1744-----------------------
1745
1746Feel free to contact me with suggestions, problems, comments, ... concerning
1747LodePNG. If you encounter a PNG image that doesn't work properly with this
1748decoder, feel free to send it and I'll use it to find and fix the problem.
1749
1750My email address is (puzzle the account and domain together with an @ symbol):
1751Domain: gmail dot com.
1752Account: lode dot vandevenne.
1753
1754
1755Copyright (c) 2005-2016 Lode Vandevenne
1756*/