lodepng.h
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1 /*
2 LodePNG version 20080927
3 
4 Copyright (c) 2005-2008 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 <stdio.h>
30 #include <stdlib.h>
31 #include <string.h>
32 
33 /* ////////////////////////////////////////////////////////////////////////// */
34 /* Code Sections */
35 /* ////////////////////////////////////////////////////////////////////////// */
36 
37 /*The following defines can be commented disable code sections. Gives potential faster compile and smaller binary.*/
38 
39 #define LODEPNG_COMPILE_ZLIB /*deflate&zlib encoder and deflate&zlib decoder*/
40 #define LODEPNG_COMPILE_PNG /*png encoder and png decoder*/
41 //#define LODEPNG_COMPILE_DECODER /*deflate&zlib decoder and png decoder*/
42 #define LODEPNG_COMPILE_ENCODER /*deflate&zlib encoder and png encoder*/
43 #define LODEPNG_COMPILE_DISK /*the optional built in harddisk file loading and saving functions*/
44 //#define LODEPNG_COMPILE_ANCILLARY_CHUNKS /*any code or struct datamember related to chunks other than IHDR, IDAT, PLTE, tRNS, IEND*/
45 //#define LODEPNG_COMPILE_UNKNOWN_CHUNKS /*handling of unknown chunks*/
46 
47 /* ////////////////////////////////////////////////////////////////////////// */
48 /* LodeFlate & LodeZlib Setting structs */
49 /* ////////////////////////////////////////////////////////////////////////// */
50 
51 #ifdef LODEPNG_COMPILE_DECODER
52 typedef struct LodeZlib_DecompressSettings
53 {
54  unsigned ignoreAdler32;
55 } LodeZlib_DecompressSettings;
56 
57 extern const LodeZlib_DecompressSettings LodeZlib_defaultDecompressSettings;
58 void LodeZlib_DecompressSettings_init(LodeZlib_DecompressSettings* settings);
59 #endif /*LODEPNG_COMPILE_DECODER*/
60 
61 #ifdef LODEPNG_COMPILE_ENCODER
62 typedef struct LodeZlib_DeflateSettings /*deflate = compress*/
63 {
64  /*LZ77 related settings*/
65  unsigned btype; /*the block type for LZ*/
66  unsigned useLZ77; /*whether or not to use LZ77*/
67  unsigned windowSize; /*the maximum is 32768*/
69 
72 #endif /*LODEPNG_COMPILE_ENCODER*/
73 
74 #ifdef LODEPNG_COMPILE_ZLIB
75 /* ////////////////////////////////////////////////////////////////////////// */
76 /* LodeFlate & LodeZlib */
77 /* ////////////////////////////////////////////////////////////////////////// */
78 
79 #ifdef LODEPNG_COMPILE_DECODER
80 /*This function reallocates the out buffer and appends the data.
81 Either, *out must be NULL and *outsize must be 0, or, *out must be a valid buffer and *outsize its size in bytes.*/
82 unsigned LodeZlib_decompress(unsigned char** out, size_t* outsize, const unsigned char* in, size_t insize, const LodeZlib_DecompressSettings* settings);
83 #endif /*LODEPNG_COMPILE_DECODER*/
84 
85 #ifdef LODEPNG_COMPILE_ENCODER
86 /*This function reallocates the out buffer and appends the data.
87 Either, *out must be NULL and *outsize must be 0, or, *out must be a valid buffer and *outsize its size in bytes.*/
88 unsigned LodeZlib_compress(unsigned char** out, size_t* outsize, const unsigned char* in, size_t insize, const LodeZlib_DeflateSettings* settings);
89 #endif /*LODEPNG_COMPILE_ENCODER*/
90 #endif /*LODEPNG_COMPILE_ZLIB*/
91 
92 #ifdef LODEPNG_COMPILE_PNG
93 
94 /* ////////////////////////////////////////////////////////////////////////// */
95 /* LodePNG */
96 /* ////////////////////////////////////////////////////////////////////////// */
97 
98 /*LodePNG_chunk functions: These functions need as input a large enough amount of allocated memory.*/
99 
100 unsigned LodePNG_chunk_length(const unsigned char* chunk); /*get the length of the data of the chunk. Total chunk length has 12 bytes more.*/
101 
102 void LodePNG_chunk_type(char type[5], const unsigned char* chunk); /*puts the 4-byte type in null terminated string*/
103 unsigned char LodePNG_chunk_type_equals(const unsigned char* chunk, const char* type); /*check if the type is the given type*/
104 
105 /*properties of PNG chunks gotten from capitalization of chunk type name, as defined by the standard*/
106 unsigned char LodePNG_chunk_critical(const unsigned char* chunk); /*0: ancillary chunk, 1: it's one of the critical chunk types*/
107 unsigned char LodePNG_chunk_private(const unsigned char* chunk); /*0: public, 1: private*/
108 unsigned char LodePNG_chunk_safetocopy(const unsigned char* chunk); /*0: the chunk is unsafe to copy, 1: the chunk is safe to copy*/
109 
110 unsigned char* LodePNG_chunk_data(unsigned char* chunk); /*get pointer to the data of the chunk*/
111 const unsigned char* LodePNG_chunk_data_const(const unsigned char* chunk); /*get pointer to the data of the chunk*/
112 
113 unsigned LodePNG_chunk_check_crc(const unsigned char* chunk); /*returns 0 if the crc is correct, 1 if it's incorrect*/
114 void LodePNG_chunk_generate_crc(unsigned char* chunk); /*generates the correct CRC from the data and puts it in the last 4 bytes of the chunk*/
115 
116 /*iterate to next chunks.*/
117 unsigned char* LodePNG_chunk_next(unsigned char* chunk);
118 const unsigned char* LodePNG_chunk_next_const(const unsigned char* chunk);
119 
120 /*add chunks to out buffer. It reallocs the buffer to append the data. returns error code*/
121 unsigned LodePNG_append_chunk(unsigned char** out, size_t* outlength, const unsigned char* chunk); /*appends chunk that was already created, to the data. Returns pointer to start of appended chunk, or NULL if error happened*/
122 unsigned LodePNG_create_chunk(unsigned char** out, size_t* outlength, unsigned length, const char* type, const unsigned char* data); /*appends new chunk to out. Returns pointer to start of appended chunk, or NULL if error happened; may change memory address of out buffer*/
123 
124 typedef struct LodePNG_InfoColor /*info about the color type of an image*/
125 {
126  /*header (IHDR)*/
127  unsigned colorType; /*color type*/
128  unsigned bitDepth; /*bits per sample*/
129 
130  /*palette (PLTE)*/
131  unsigned char* palette; /*palette in RGBARGBA... order*/
132  size_t palettesize; /*palette size in number of colors (amount of bytes is 4 * palettesize)*/
133 
134  /*transparent color key (tRNS)*/
135  unsigned key_defined; /*is a transparent color key given?*/
136  unsigned key_r; /*red component of color key*/
137  unsigned key_g; /*green component of color key*/
138  unsigned key_b; /*blue component of color key*/
140 
144 
145 /*Use these functions instead of allocating palette manually*/
147 unsigned LodePNG_InfoColor_addPalette(LodePNG_InfoColor* info, unsigned char r, unsigned char g, unsigned char b, unsigned char a); /*add 1 color to the palette*/
148 
149 /*additional color info*/
150 unsigned LodePNG_InfoColor_getBpp(const LodePNG_InfoColor* info); /*bits per pixel*/
151 unsigned LodePNG_InfoColor_getChannels(const LodePNG_InfoColor* info); /*amount of channels*/
152 unsigned LodePNG_InfoColor_isGreyscaleType(const LodePNG_InfoColor* info); /*is it a greyscale type? (colorType 0 or 4)*/
153 unsigned LodePNG_InfoColor_isAlphaType(const LodePNG_InfoColor* info); /*has it an alpha channel? (colorType 2 or 6)*/
154 
155 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
156 typedef struct LodePNG_Time /*LodePNG's encoder does not generate the current time. To make it add a time chunk the correct time has to be provided*/
157 {
158  unsigned year; /*2 bytes*/
159  unsigned char month; /*1-12*/
160  unsigned char day; /*1-31*/
161  unsigned char hour; /*0-23*/
162  unsigned char minute; /*0-59*/
163  unsigned char second; /*0-60 (to allow for leap seconds)*/
164 } LodePNG_Time;
165 
166 typedef struct LodePNG_Text /*non-international text*/
167 {
168  size_t num;
169  char** keys; /*the keyword of a text chunk (e.g. "Comment")*/
170  char** strings; /*the actual text*/
171 } LodePNG_Text;
172 
173 void LodePNG_Text_init(LodePNG_Text* text);
174 void LodePNG_Text_cleanup(LodePNG_Text* text);
175 unsigned LodePNG_Text_copy(LodePNG_Text* dest, const LodePNG_Text* source);
176 
177 /*Use these functions instead of allocating the char**s manually*/
178 void LodePNG_Text_clear(LodePNG_Text* text);
179 unsigned LodePNG_Text_add(LodePNG_Text* text, const char* key, const char* str); /*push back both texts at once*/
180 
181 
182 typedef struct LodePNG_IText /*international text*/
183 {
184  size_t num;
185  char** keys; /*the English keyword of the text chunk (e.g. "Comment")*/
186  char** langtags; /*the language tag for this text's international language, ISO/IEC 646 string, e.g. ISO 639 language tag*/
187  char** transkeys; /*keyword translated to the international language - UTF-8 string*/
188  char** strings; /*the actual international text - UTF-8 string*/
189 } LodePNG_IText;
190 
191 void LodePNG_IText_init(LodePNG_IText* text);
192 void LodePNG_IText_cleanup(LodePNG_IText* text);
193 unsigned LodePNG_IText_copy(LodePNG_IText* dest, const LodePNG_IText* source);
194 
195 /*Use these functions instead of allocating the char**s manually*/
196 void LodePNG_IText_clear(LodePNG_IText* text);
197 unsigned LodePNG_IText_add(LodePNG_IText* text, const char* key, const char* langtag, const char* transkey, const char* str); /*push back the 4 texts of 1 chunk at once*/
198 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
199 
200 #ifdef LODEPNG_COMPILE_UNKNOWN_CHUNKS
201 typedef struct LodePNG_UnknownChunks /*unknown chunks read from the PNG, or extra chunks the user wants to have added in the encoded PNG*/
202 {
203  /*There are 3 buffers, one for each position in the PNG where unknown chunks can appear
204  each buffer contains all unknown chunks for that position consecutively
205  The 3 buffers are the unknown chunks between certain critical chunks:
206  0: IHDR-PLTE, 1: PLTE-IDAT, 2: IDAT-IEND*/
207  unsigned char* data[3];
208  size_t datasize[3]; /*size in bytes of the unknown chunks, given for protection*/
209 
210 } LodePNG_UnknownChunks;
211 
212 void LodePNG_UnknownChunks_init(LodePNG_UnknownChunks* chunks);
213 void LodePNG_UnknownChunks_cleanup(LodePNG_UnknownChunks* chunks);
214 unsigned LodePNG_UnknownChunks_copy(LodePNG_UnknownChunks* dest, const LodePNG_UnknownChunks* src);
215 #endif /*LODEPNG_COMPILE_UNKNOWN_CHUNKS*/
216 
217 typedef struct LodePNG_InfoPng /*information about the PNG image, except pixels and sometimes except width and height*/
218 {
219  /*header (IHDR), palette (PLTE) and transparency (tRNS)*/
220  unsigned width; /*width of the image in pixels (ignored by encoder, but filled in by decoder)*/
221  unsigned height; /*height of the image in pixels (ignored by encoder, but filled in by decoder)*/
222  unsigned compressionMethod; /*compression method of the original file*/
223  unsigned filterMethod; /*filter method of the original file*/
224  unsigned interlaceMethod; /*interlace method of the original file*/
225  LodePNG_InfoColor color; /*color type and bits, palette, transparency*/
226 
227 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
228 
229  /*suggested background color (bKGD)*/
230  unsigned background_defined; /*is a suggested background color given?*/
231  unsigned background_r; /*red component of suggested background color*/
232  unsigned background_g; /*green component of suggested background color*/
233  unsigned background_b; /*blue component of suggested background color*/
234 
235  /*non-international text chunks (tEXt and zTXt)*/
236  LodePNG_Text text;
237 
238  /*international text chunks (iTXt)*/
239  LodePNG_IText itext;
240 
241  /*time chunk (tIME)*/
242  unsigned char time_defined; /*if 0, no tIME chunk was or will be generated in the PNG image*/
243  LodePNG_Time time;
244 
245  /*phys chunk (pHYs)*/
246  unsigned phys_defined; /*is pHYs chunk defined?*/
247  unsigned phys_x;
248  unsigned phys_y;
249  unsigned char phys_unit; /*may be 0 (unknown unit) or 1 (metre)*/
250 
251 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
252 
253 #ifdef LODEPNG_COMPILE_UNKNOWN_CHUNKS
254  /*unknown chunks*/
255  LodePNG_UnknownChunks unknown_chunks;
256 #endif /*LODEPNG_COMPILE_UNKNOWN_CHUNKS*/
257 
259 
262 unsigned LodePNG_InfoPng_copy(LodePNG_InfoPng* dest, const LodePNG_InfoPng* source);
263 
264 typedef struct LodePNG_InfoRaw /*contains user-chosen information about the raw image data, which is independent of the PNG image*/
265 {
268 
271 unsigned LodePNG_InfoRaw_copy(LodePNG_InfoRaw* dest, const LodePNG_InfoRaw* source);
272 
273 /*
274 LodePNG_convert: Converts from any color type to 24-bit or 32-bit (later maybe more supported). return value = LodePNG error code
275 The out buffer must have (w * h * bpp + 7) / 8, where bpp is the bits per pixel of the output color type (LodePNG_InfoColor_getBpp)
276 */
277 unsigned LodePNG_convert(unsigned char* out, const unsigned char* in, LodePNG_InfoColor* infoOut, LodePNG_InfoColor* infoIn, unsigned w, unsigned h);
278 
279 #ifdef LODEPNG_COMPILE_DECODER
280 
281 typedef struct LodePNG_DecodeSettings
282 {
283  LodeZlib_DecompressSettings zlibsettings; /*in here is the setting to ignore Adler32 checksums*/
284 
285  unsigned ignoreCrc; /*ignore CRC checksums*/
286  unsigned color_convert; /*whether to convert the PNG to the color type you want. Default: yes*/
287 
288 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
289  unsigned readTextChunks; /*if false but rememberUnknownChunks is true, they're stored in the unknown chunks*/
290 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
291 
292 #ifdef LODEPNG_COMPILE_UNKNOWN_CHUNKS
293  unsigned rememberUnknownChunks; /*store all bytes from unknown chunks in the InfoPng (off by default, useful for a png editor)*/
294 #endif /*LODEPNG_COMPILE_UNKNOWN_CHUNKS*/
295 } LodePNG_DecodeSettings;
296 
297 void LodePNG_DecodeSettings_init(LodePNG_DecodeSettings* settings);
298 
299 typedef struct LodePNG_Decoder
300 {
301  LodePNG_DecodeSettings settings;
302  LodePNG_InfoRaw infoRaw;
303  LodePNG_InfoPng infoPng; /*info of the PNG image obtained after decoding*/
304  unsigned error;
305 } LodePNG_Decoder;
306 
307 void LodePNG_Decoder_init(LodePNG_Decoder* decoder);
308 void LodePNG_Decoder_cleanup(LodePNG_Decoder* decoder);
309 void LodePNG_Decoder_copy(LodePNG_Decoder* dest, const LodePNG_Decoder* source);
310 
311 /*decoding functions*/
312 /*This function allocates the out buffer and stores the size in *outsize.*/
313 void LodePNG_decode(LodePNG_Decoder* decoder, unsigned char** out, size_t* outsize, const unsigned char* in, size_t insize);
314 unsigned LodePNG_decode32(unsigned char** out, unsigned* w, unsigned* h, const unsigned char* in, size_t insize); /*return value is error*/
315 #ifdef LODEPNG_COMPILE_DISK
316 unsigned LodePNG_decode32f(unsigned char** out, unsigned* w, unsigned* h, const char* filename);
317 #endif /*LODEPNG_COMPILE_DISK*/
318 void LodePNG_inspect(LodePNG_Decoder* decoder, const unsigned char* in, size_t size); /*read the png header*/
319 
320 #endif /*LODEPNG_COMPILE_DECODER*/
321 
322 #ifdef LODEPNG_COMPILE_ENCODER
323 
325 {
326  LodeZlib_DeflateSettings zlibsettings; /*settings for the zlib encoder, such as window size, ...*/
327 
328  unsigned autoLeaveOutAlphaChannel; /*automatically use color type without alpha instead of given one, if given image is opaque*/
329  unsigned force_palette; /*force creating a PLTE chunk if colortype is 2 or 6 (= a suggested palette). If colortype is 3, PLTE is _always_ created.*/
330 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
331  unsigned add_id; /*add LodePNG version as text chunk*/
332  unsigned text_compression; /*encode text chunks as zTXt chunks instead of tEXt chunks, and use compression in iTXt chunks*/
333 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
335 
337 
338 typedef struct LodePNG_Encoder
339 {
341  LodePNG_InfoPng infoPng; /*the info specified by the user may not be changed by the encoder. The encoder will try to generate a PNG close to the given info.*/
342  LodePNG_InfoRaw infoRaw; /*put the properties of the input raw image in here*/
343  unsigned error;
345 
349 
350 /*This function allocates the out buffer and stores the size in *outsize.*/
351 void LodePNG_encode(LodePNG_Encoder* encoder, unsigned char** out, size_t* outsize, const unsigned char* image, unsigned w, unsigned h);
352 unsigned LodePNG_encode32(unsigned char** out, size_t* outsize, const unsigned char* image, unsigned w, unsigned h); /*return value is error*/
353 #ifdef LODEPNG_COMPILE_DISK
354 unsigned LodePNG_encode32f(const char* filename, const unsigned char* image, unsigned w, unsigned h);
355 #endif /*LODEPNG_COMPILE_DISK*/
356 #endif /*LODEPNG_COMPILE_ENCODER*/
357 #endif /*LODEPNG_COMPILE_PNG*/
358 
359 #ifdef LODEPNG_COMPILE_DISK
360 /*free functions allowing to load and save a file from/to harddisk*/
361 /*This function allocates the out buffer and stores the size in *outsize.*/
362 unsigned LodePNG_loadFile(unsigned char** out, size_t* outsize, const char* filename);
363 unsigned LodePNG_saveFile(const unsigned char* buffer, size_t buffersize, const char* filename);
364 #endif /*LODEPNG_COMPILE_DISK*/
365 
366 
367 /*
368 TODO:
369 [ ] test if there are no memory leaks or security exploits - done a lot but needs to be checked often
370 [ ] LZ77 encoder more like the one described in zlib - to make sure it's patentfree
371 [ ] converting color to 16-bit types
372 [ ] read all public PNG chunk types (but never let the color profile and gamma ones ever touch RGB values, that is very annoying for textures as well as images in a browser)
373 [ ] make sure encoder generates no chunks with size > (2^31)-1
374 [ ] partial decoding (stream processing)
375 [ ] let the "isFullyOpaque" function check color keys and transparent palettes too
376 [ ] better name for the variables "codes", "codesD", "codelengthcodes", "clcl" and "lldl"
377 [ ] check compatibility with vareous compilers - done but needs to be redone for every newer version
378 [ ] don't stop decoding on errors like 69, 57, 58 (make warnings that the decoder stores in the error at the very end? and make some errors just let it stop with this one chunk but still do the next ones)
379 [ ] make option to choose if the raw image with non multiple of 8 bits per scanline should have padding bits or not, if people like storing raw images that way
380 */
381 
382 #endif
383 
384 /*
385 LodePNG Documentation
386 ---------------------
387 
388 0. table of contents
389 --------------------
390 
391  1. about
392  1.1. supported features
393  1.2. features not supported
394  2. C and C++ version
395  3. A note about security!
396  4. simple functions
397  4.1 C Simple Functions
398  4.2 C++ Simple Functions
399  5. decoder
400  6. encoder
401  7. color conversions
402  8. info values
403  9. error values
404  10. file IO
405  11. chunks and PNG editing
406  12. compiler support
407  13. examples
408  13.1. decoder example
409  13.2. encoder example
410  14. LodeZlib
411  15. changes
412  16. contact information
413 
414 
415 1. about
416 --------
417 
418 PNG is a file format to store raster images losslessly with good compression,
419 supporting different color types. It can be implemented in a patent-free way.
420 
421 LodePNG is a PNG codec according to the Portable Network Graphics (PNG)
422 Specification (Second Edition) - W3C Recommendation 10 November 2003.
423 
424 The specifications used are:
425 
426 *) Portable Network Graphics (PNG) Specification (Second Edition):
427  http://www.w3.org/TR/2003/REC-PNG-20031110
428 *) RFC 1950 ZLIB Compressed Data Format version 3.3:
429  http://www.gzip.org/zlib/rfc-zlib.html
430 *) RFC 1951 DEFLATE Compressed Data Format Specification ver 1.3:
431  http://www.gzip.org/zlib/rfc-deflate.html
432 
433 The most recent version of LodePNG can currently be found at
434 http://members.gamedev.net/lode/projects/LodePNG/
435 
436 LodePNG works both in C (ISO C90) and C++, with a C++ wrapper that adds
437 extra functionality.
438 
439 LodePNG exists out of two files:
440 -lodepng.h: the header file for both C and C++
441 -lodepng.c(pp): give it the name lodepng.c or lodepng.cpp depending on your usage
442 
443 If you want to start using LodePNG right away without reading this doc, get the
444 files lodepng_examples.c or lodepng_examples.cpp to see how to use it in code,
445 or check the (smaller) examples in chapter 13 here.
446 
447 LodePNG is simple but only supports the basic requirements. To achieve
448 simplicity, the following design choices were made: There are no dependencies
449 on any external library. To decode PNGs, there's a Decoder struct or class that
450 can convert any PNG file data into an RGBA image buffer with a single function
451 call. To encode PNGs, there's an Encoder struct or class that can convert image
452 data into PNG file data with a single function call. To read and write files,
453 there are simple functions to convert the files to/from buffers in memory.
454 
455 This all makes LodePNG suitable for loading textures in games, demoscene
456 productions, saving a screenshot, images in programs that require them for simple
457 usage, ... It's less suitable for full fledged image editors, loading PNGs
458 over network (it requires all the image data to be available before decoding can
459 begin), life-critical systems, ...
460 LodePNG has a standards conformant decoder and encoder, and supports the ability
461 to make a somewhat conformant editor.
462 
463 1.1. supported features
464 -----------------------
465 
466 The following features are supported by the decoder:
467 
468 *) decoding of PNGs with any color type, bit depth and interlace mode, to a 24- or 32-bit color raw image, or the same color type as the PNG
469 *) encoding of PNGs, from any raw image to 24- or 32-bit color, or the same color type as the raw image
470 *) Adam7 interlace and deinterlace for any color type
471 *) loading the image from harddisk or decoding it from a buffer from other sources than harddisk
472 *) support for alpha channels, including RGBA color model, translucent palettes and color keying
473 *) zlib decompression (inflate)
474 *) zlib compression (deflate)
475 *) CRC32 and ADLER32 checksums
476 *) handling of unknown chunks, allowing making a PNG editor that stores custom and unknown chunks.
477 *) the following chunks are supported (generated/interpreted) by both encoder and decoder:
478  IHDR: header information
479  PLTE: color palette
480  IDAT: pixel data
481  IEND: the final chunk
482  tRNS: transparency for palettized images
483  tEXt: textual information
484  zTXt: compressed textual information
485  iTXt: international textual information
486  bKGD: suggested background color
487  pHYs: physical dimensions
488  tIME: modification time
489 
490 1.2. features not supported
491 ---------------------------
492 
493 The following features are _not_ supported:
494 
495 *) some features needed to make a conformant PNG-Editor might be still missing.
496 *) partial loading/stream processing. All data must be available and is processed in one call.
497 *) The following public chunks are not supported but treated as unknown chunks by LodePNG
498  cHRM, gAMA, iCCP, sRGB, sBIT, hIST, sPLT
499 
500 
501 2. C and C++ version
502 --------------------
503 
504 The C version uses buffers allocated with alloc instead that you need to free()
505 yourself. On top of that, you need to use init and cleanup functions for each
506 struct whenever using a struct from the C version to avoid exploits and memory leaks.
507 
508 The C++ version has constructors and destructors that take care of these things,
509 and uses std::vectors in the interface for storing data.
510 
511 Both the C and the C++ version are contained in this file! The C++ code depends on
512 the C code, the C code works on its own.
513 
514 These files work without modification for both C and C++ compilers because all the
515 additional C++ code is in "#ifdef __cplusplus" blocks that make C-compilers ignore
516 it, and the C code is made to compile both with strict ISO C90 and C++.
517 
518 To use the C++ version, you need to rename the source file to lodepng.cpp (instead
519 of lodepng.c), and compile it with a C++ compiler.
520 
521 To use the C version, you need to rename the source file to lodepng.c (instead
522 of lodepng.cpp), and compile it with a C compiler.
523 
524 
525 3. A note about security!
526 -------------------------
527 
528 Despite being used already and having received bug fixes whenever bugs were reported,
529 LodePNG may still contain possible exploits.
530 
531 If you discover a possible exploit, please let me know, and it will be eliminated.
532 
533 When using LodePNG, care has to be taken with the C version of LodePNG, as well as the C-style
534 structs when working with C++. The following conventions are used for all C-style structs:
535 
536 -if a struct has a corresponding init function, always call the init function when making a new one, to avoid exploits
537 -if a struct has a corresponding cleanup function, call it before the struct disappears to avoid memory leaks
538 -if a struct has a corresponding copy function, use the copy function instead of "=". The destination must be inited already!
539 
540 
541 4. "Simple" Functions
542 ---------------------
543 
544 For the most simple usage cases of loading and saving a PNG image, there
545 are some simple functions that do everything in 1 call (instead of you
546 having to instantiate a struct or class).
547 
548 The simple versions always use 32-bit RGBA color for the raw image, but
549 still support loading arbitrary-colortype PNG images.
550 
551 The later sections of this manual are devoted to the complex versions, where
552 you can use other color types and conversions.
553 
554 4.1 C Simple Functions
555 ----------------------
556 
557 The C simple functions have a "32" or "32f" in their name, and don't take a struct as
558 parameter, unlike the non-simple ones (see more down in the documentation).
559 
560 unsigned LodePNG_decode32(unsigned char** out, unsigned* w, unsigned* h, const unsigned char* in, size_t insize);
561 
562 Load PNG from given buffer.
563 As input, give an unsigned char* buffer gotten by loading the .png file and its size.
564 As output, you get a dynamically allocated buffer of large enough size, and the width and height of the image.
565 The buffer's size is w * h * 4. The image is in RGBA format.
566 The return value is the error (0 if ok).
567 You need to do free(out) after usage to clean up the memory.
568 
569 unsigned LodePNG_decode32f(unsigned char** out, unsigned* w, unsigned* h, const char* filename);
570 
571 Load PNG from disk, from file with given name.
572 Same as decode32, except you give a filename instead of an input buffer.
573 
574 unsigned LodePNG_encode32(unsigned char** out, size_t* outsize, const unsigned char* image, unsigned w, unsigned h);
575 
576 Encode PNG into buffer.
577 As input, give a image buffer of size w * h * 4, in RGBA format.
578 As output, you get a dynamically allocated buffer and its size, which is a PNG file that can
579 directly be saved in this form to the harddisk.
580 The return value is the error (0 if ok).
581 You need to do free(out) after usage to clean up the memory.
582 
583 unsigned LodePNG_encode32f(const char* filename, const unsigned char* image, unsigned w, unsigned h);
584 
585 Encode PNG into file on disk with given name.
586 If the file exists, it's overwritten without warning!
587 Same parameters as encode2, except the result is stored in a file instead of a dynamic buffer.
588 
589 4.2 C++ Simple Functions
590 ------------------------
591 
592 For decoding a PNG there are:
593 
594 unsigned LodePNG::decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h, const unsigned char* in, unsigned size);
595 unsigned LodePNG::decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h, const std::vector<unsigned char>& in);
596 unsigned LodePNG::decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h, const std::string& filename);
597 
598 These store the pixel data as 32-bit RGBA color in the out vector, and the width
599 and height of the image in w and h.
600 The 3 functions each have a different input type: The first as unsigned char
601 buffer, the second as std::vector buffer, and the third allows you to give the
602 filename in case you want to load the PNG from disk instead of from a buffer.
603 The return value is the error (0 if ok).
604 
605 For encoding a PNG there are:
606 
607 unsigned LodePNG::encode(std::vector<unsigned char>& out, const unsigned char* in, unsigned w, unsigned h);
608 unsigned LodePNG::encode(std::vector<unsigned char>& out, const std::vector<unsigned char>& in, unsigned w, unsigned h);
609 unsigned LodePNG::encode(const std::string& filename, const std::vector<unsigned char>& in, unsigned w, unsigned h);
610 unsigned LodePNG::encode(const std::string& filename, const unsigned char* in, unsigned w, unsigned h);
611 
612 Specify the width and height of the input image with w and h.
613 You can choose to get the output in an std::vector or stored in a file, and
614 the input can come from an std::vector or an unsigned char* buffer. The input
615 buffer must be in RGBA format and the size must be w * h * 4 bytes.
616 
617 The first two functions append to the out buffer, they don't clear it, clear it
618 first before encoding into a buffer that you expect to only contain this result.
619 
620 On the other hand, the functions that encode to a file will completely overwrite
621 the original file without warning if it exists.
622 
623 The return value is the error (0 if ok).
624 
625 5. Decoder
626 ----------
627 
628 This is about the LodePNG_Decoder struct in the C version, and the
629 LodePNG::Decoder class in the C++ version. The C++ version inherits
630 from the C struct and adds functions in the interface.
631 
632 The Decoder class can be used to convert a PNG image to a raw image.
633 
634 Usage:
635 
636 -in C++:
637  declare a LodePNG::Decoder
638  call its decode member function with the parameters described below
639 
640 -in C more needs to be done due to the lack of constructors and destructors:
641  declare a LodePNG_Decoder struct
642  call LodePNG_Decoder_init with the struct as parameter
643  call LodePNG_Decode with the parameters described below
644  after usage, call LodePNG_Decoder_cleanup with the struct as parameter
645  after usage, free() the out buffer with image data that was created by the decode function
646 
647 The other parameters of the decode function are:
648 *) out: this buffer will be filled with the raw image pixels
649 *) in: pointer to the PNG image data or std::vector with the data
650 *) size: the size of the PNG image data (not needed for std::vector version)
651 
652 After decoding you need to read the width and height of the image from the
653 decoder, see further down in this manual to see how.
654 
655 There's also an optional function "inspect". It has the same parameters as decode except
656 the "out" parameter. This function will read only the header chunk of the PNG
657 image, and store the information from it in the LodePNG_InfoPng (see below).
658 This allows knowing information about the image without decoding it. Only the
659 header (IHDR) information is read by this, not text chunks, not the palette, ...
660 
661 During the decoding it's possible that an error can happen, for example if the
662 PNG image was corrupted. To check if an error happened during the last decoding,
663 check the value error, which is a member of the decoder struct.
664 In the C++ version, use hasError() and getError() of the Decoder.
665 The error codes are explained in another section.
666 
667 Now about colors and settings...
668 
669 The Decoder contains 3 components:
670 *) LodePNG_InfoPng: it stores information about the PNG (the input) in an LodePNG_InfoPng struct, don't modify this one yourself
671 *) Settings: you can specify a few other settings for the decoder to use
672 *) LodePNG_InfoRaw: here you can say what type of raw image (the output) you want to get
673 
674 Some of the parameters described below may be inside the sub-struct "LodePNG_InfoColor color".
675 In the C and C++ version, when using Info structs outside of the decoder or encoder, you need to use their
676 init and cleanup functions, but normally you use the ones in the decoder that are already handled
677 in the init and cleanup functions of the decoder itself.
678 
679 =LodePNG_InfoPng=
680 
681 This contains information such as the original color type of the PNG image, text
682 comments, suggested background color, etc... More details about the LodePNG_InfoPng struct
683 are in another section.
684 
685 Because the dimensions of the image are important, there are shortcuts to get them in the
686 C++ version: use decoder.getWidth() and decoder.getHeight().
687 In the C version, use decoder.infoPng.width and decoder.infoPng.height.
688 
689 =LodePNG_InfoRaw=
690 
691 In the LodePNG_InfoRaw struct of the Decoder, you can specify which color type you want
692 the resulting raw image to be. If this is different from the colorType of the
693 PNG, then the decoder will automatically convert the result to your LodePNG_InfoRaw
694 settings. Currently the following options are supported to convert to:
695 -colorType 6, bitDepth 8: 32-bit RGBA
696 -colorType 2, bitDepth 8: 24-bit RGB
697 -other color types if it's exactly the same as that in the PNG image
698 
699 Palette of LodePNG_InfoRaw isn't used by the Decoder, when converting from palette color
700 to palette color, the values of the pixels are left untouched so that the colors
701 will change if the palette is different. Color key of LodePNG_InfoRaw is not used by the
702 Decoder. If setting color_convert is false then LodePNG_InfoRaw is completely ignored,
703 but it will be modified to match the color type of the PNG so will be overwritten.
704 
705 By default, 32-bit color is used for the result.
706 
707 =Settings=
708 
709 The Settings can be used to ignore the errors created by invalid CRC and Adler32
710 chunks, and to disable the decoding of tEXt chunks.
711 
712 There's also a setting color_convert, true by default. If false, no conversion
713 is done, the resulting data will be as it was in the PNG (after decompression)
714 and you'll have to puzzle the colors of the pixels together yourself using the
715 color type information in the LodePNG_InfoPng.
716 
717 
718 6. Encoder
719 ----------
720 
721 This is about the LodePNG_Encoder struct in the C version, and the
722 LodePNG::Encoder class in the C++ version.
723 
724 The Encoder class can be used to convert raw image data into a PNG image.
725 
726 The PNG part of the encoder is working good, the zlib compression part is
727 becoming quite fine but not as good as the official zlib yet, because it's not
728 as fast and doesn't provide an as high compression ratio.
729 
730 Usage:
731 
732 -in C++:
733  declare a LodePNG::Encoder
734  call its encode member function with the parameters described below
735 
736 -in C more needs to be done due to the lack of constructors and destructors:
737  declare a LodePNG_Encoder struct
738  call LodePNG_Encoder_init with the struct as parameter
739  call LodePNG_Encode with the parameters described below
740  after usage, call LodePNG_Encoder_cleanup with the struct as parameter
741  after usage, free() the out buffer with PNG data that was created by the encode function
742 
743 The raw image given to the encoder is an unsigned char* buffer. You also have to
744 specify the width and height of the raw image. The result is stored in a given
745 buffer. These buffers can be unsigned char* pointers, std::vectors or dynamically
746 allocated unsigned char* buffers that you have to free() yourself, depending on
747 which you use.
748 
749 The parameters of the encode function are:
750 *) out: in this buffer the PNG file data will be stored (it will be appended)
751 *) in: vector of or pointer to a buffer containing the raw image
752 *) w and h: the width and height of the raw image in pixels
753 
754 Make sure that the in buffer you provide, is big enough to contain w * h pixels
755 of the color type specified by the LodePNG_InfoRaw.
756 
757 In the C version, you need to free() the out buffer after usage to avoid memory leaks.
758 In the C version, you need to use the LodePNG_Encoder_init function before using the decoder,
759 and the LodePNG_Encoder_cleanup function after using it.
760 In the C++ version, you don't need to do this since RAII takes care of it.
761 
762 The encoder generates some errors but not for everything, because, unlike when
763 decoding a PNG, when encoding one there aren't so much parameters of the input
764 that can be corrupted. It's the responsibility of the user to make sure that all
765 preconditions are satesfied, such as giving a correct window size, giving an
766 existing btype, making sure the given buffer is large enough to contain an image
767 with the given width and height and colortype, ... The encoder can generate
768 some errors, see the section with the explanations of errors for those.
769 
770 Like the Decoder, the Encoder has 3 components:
771 *) LodePNG_InfoRaw: here you say what color type of the raw image (the input) has
772 *) Settings: you can specify a few settings for the encoder to use
773 *) LodePNG_InfoPng: the same LodePNG_InfoPng struct as created by the Decoder. For the encoder,
774 with this you specify how you want the PNG (the output) to be.
775 
776 Some of the parameters described below may be inside the sub-struct "LodePNG_InfoColor color".
777 In the C and C++ version, when using Info structs outside of the decoder or encoder, you need to use their
778 init and cleanup functions, but normally you use the ones in the encoder that are already handled
779 in the init and cleanup functions of the decoder itself.
780 
781 =LodePNG_InfoPng=
782 
783 The Decoder class stores information about the PNG image in an LodePNG_InfoPng object. With
784 the Encoder you can do the opposite: you give it an LodePNG_InfoPng object, and it'll try
785 to match the LodePNG_InfoPng you give as close as possible in the PNG it encodes. For
786 example in the LodePNG_InfoPng you can specify the color type you want to use, possible
787 tEXt chunks you want the PNG to contain, etc... For an explanation of all the
788 values in LodePNG_InfoPng see a further section. Not all PNG color types are supported
789 by the Encoder.
790 
791 Note that the encoder will only TRY to match the LodePNG_InfoPng struct you give.
792 Some things are ignored by the encoder. The width and height of LodePNG_InfoPng are
793 ignored as well, because instead the width and height of the raw image you give
794 in the input are used. In fact the encoder currently uses only the following
795 settings from it:
796 -colorType: the ones it supports
797 -text chunks, that you can add to the LodePNG_InfoPng with "addText"
798 -the color key, if applicable for the given color type
799 -the palette, if you encode to a PNG with colorType 3
800 -the background color: it'll add a bKGD chunk to the PNG if one is given
801 -the interlaceMethod: None (0) or Adam7 (1)
802 
803 When encoding to a PNG with colorType 3, the encoder will generate a PLTE chunk.
804 If the palette contains any colors for which the alpha channel is not 255 (so
805 there are translucent colors in the palette), it'll add a tRNS chunk.
806 
807 =LodePNG_InfoRaw=
808 
809 You specify the color type of the raw image that you give to the input here,
810 including a possible transparent color key and palette you happen to be using in
811 your raw image data.
812 
813 By default, 32-bit color is assumed, meaning your input has to be in RGBA
814 format with 4 bytes (unsigned chars) per pixel.
815 
816 =Settings=
817 
818 The following settings are supported (some are in sub-structs):
819 *) autoLeaveOutAlphaChannel: when this option is enabled, when you specify a PNG
820 color type with alpha channel (not to be confused with the color type of the raw
821 image you specify!!), but the encoder detects that all pixels of the given image
822 are opaque, then it'll automatically use the corresponding type without alpha
823 channel, resulting in a smaller PNG image.
824 *) btype: the block type for LZ77. 0 = uncompressed, 1 = fixed huffman tree, 2 = dynamic huffman tree (best compression)
825 *) useLZ77: whether or not to use LZ77 for compressed block types
826 *) windowSize: the window size used by the LZ77 encoder (1 - 32768)
827 *) force_palette: if colorType is 2 or 6, you can make the encoder write a PLTE
828  chunk if force_palette is true. This can used as suggested palette to convert
829  to by viewers that don't support more than 256 colors (if those still exist)
830 *) add_id: add text chunk "Encoder: LodePNG <version>" to the image.
831 *) text_compression: default 0. If 1, it'll store texts as zTXt instead of tEXt chunks.
832  zTXt chunks use zlib compression on the text. This gives a smaller result on
833  large texts but a larger result on small texts (such as a single program name).
834  It's all tEXt or all zTXt though, there's no separate setting per text yet.
835 
836 
837 7. color conversions
838 --------------------
839 
840 For trickier usage of LodePNG, you need to understand about PNG color types and
841 about how and when LodePNG uses the settings in LodePNG_InfoPng, LodePNG_InfoRaw and Settings.
842 
843 =PNG color types=
844 
845 A PNG image can have many color types, ranging from 1-bit color to 64-bit color,
846 as well as palettized color modes. After the zlib decompression and unfiltering
847 in the PNG image is done, the raw pixel data will have that color type and thus
848 a certain amount of bits per pixel. If you want the output raw image after
849 decoding to have another color type, a conversion is done by LodePNG.
850 
851 The PNG specification mentions the following color types:
852 
853 0: greyscale, bit depths 1, 2, 4, 8, 16
854 2: RGB, bit depths 8 and 16
855 3: palette, bit depths 1, 2, 4 and 8
856 4: greyscale with alpha, bit depths 8 and 16
857 6: RGBA, bit depths 8 and 16
858 
859 Bit depth is the amount of bits per color channel.
860 
861 =Default Behaviour of LodePNG=
862 
863 By default, the Decoder will convert the data from the PNG to 32-bit RGBA color,
864 no matter what color type the PNG has, so that the result can be used directly
865 as a texture in OpenGL etc... without worries about what color type the original
866 image has.
867 
868 The Encoder assumes by default that the raw input you give it is a 32-bit RGBA
869 buffer and will store the PNG as either 32 bit or 24 bit depending on whether
870 or not any translucent pixels were detected in it.
871 
872 To get the default behaviour, don't change the values of LodePNG_InfoRaw and LodePNG_InfoPng of
873 the encoder, and don't change the values of LodePNG_InfoRaw of the decoder.
874 
875 =Color Conversions=
876 
877 As explained in the sections about the Encoder and Decoder, you can specify
878 color types and bit depths in LodePNG_InfoPng and LodePNG_InfoRaw, to change the default behaviour
879 explained above. (for the Decoder you can only specify the LodePNG_InfoRaw, because the
880 LodePNG_InfoPng contains what the PNG file has).
881 
882 To avoid some confusion:
883 -the Decoder converts from PNG to raw image
884 -the Encoder converts from raw image to PNG
885 -the color type and bit depth in LodePNG_InfoRaw, are those of the raw image
886 -the color type and bit depth in LodePNG_InfoPng, are those of the PNG
887 -if the color type of the LodePNG_InfoRaw and PNG image aren't the same, a conversion
888 between the color types is done if the color types are supported
889 
890 Supported color types:
891 -It's possible to load PNGs from any colortype and to save PNGs of any colorType.
892 -Both encoder and decoder use the same converter. So both encoder and decoder
893 suport the same color types at the input and the output. So the decoder supports
894 any type of PNG image and can convert it to certain types of raw image, while the
895 encoder supports any type of raw data but only certain color types for the output PNG.
896 -The converter can convert from _any_ input color type, to 24-bit RGB or 32-bit RGBA
897 -The converter can convert from greyscale input color type, to 8-bit greyscale or greyscale with alpha
898 -If both color types are the same, conversion from anything to anything is possible
899 -Color types that are invalid according to the PNG specification are not allowed
900 -When converting from a type with alpha channel to one without, the alpha channel information is discarded
901 -When converting from a type without alpha channel to one with, the result will be opaque except pixels that have the same color as the color key of the input if one was given
902 -When converting from 16-bit bitDepth to 8-bit bitDepth, the 16-bit precision information is lost, only the most significant byte is kept
903 -Converting from color to greyscale is not supported on purpose: choosing what kind of color to greyscale conversion to do is not a decision a PNG codec should make
904 -Converting from/to a palette type, only keeps the indices, it ignores the colors defined in the palette
905 
906 No conversion needed...:
907 -If the color type of the PNG image and raw image are the same, then no
908 conversion is done, and all color types are supported.
909 -In the encoder, you can make it save a PNG with any color by giving the
910 LodePNG_InfoRaw and LodePNG_InfoPng the same color type.
911 -In the decoder, you can make it store the pixel data in the same color type
912 as the PNG has, by setting the color_convert setting to false. Settings in
913 infoRaw are then ignored.
914 
915 The function LodePNG_convert does this, which is available in the interface but
916 normally isn't needed since the encoder and decoder already call it.
917 
918 =More Notes=
919 
920 In the PNG file format, if a less than 8-bit per pixel color type is used and the scanlines
921 have a bit amount that isn't a multiple of 8, then padding bits are used so that each
922 scanline starts at a fresh byte.
923 However: The input image you give to the encoder, and the output image you get from the decoder
924 will NOT have these padding bits in that case, e.g. in the case of a 1-bit image with a width
925 of 7 pixels, the first pixel of the second scanline will the the 8th bit of the first byte,
926 not the first bit of a new byte.
927 
928 8. info values
929 --------------
930 
931 Both the encoder and decoder use a variable of type LodePNG_InfoPng and LodePNG_InfoRaw, which
932 both also contain a LodePNG_InfoColor. Here's a list of each of the values stored in them:
933 
934 *) info from the PNG header (IHDR chunk):
935 
936 width: width of the image in pixels
937 height: height of the image in pixels
938 colorType: color type of the original PNG file
939 bitDepth: bits per sample
940 compressionMethod: compression method of the original file. Always 0.
941 filterMethod: filter method of the original file. Always 0.
942 interlaceMethod: interlace method of the original file. 0 is no interlace, 1 is adam7 interlace.
943 
944 Note: width and height are only used as information of a decoded PNG image. When encoding one, you don't have
945 to specify width and height in an LodePNG_Info struct, but you give them as parameters of the encode function.
946 The rest of the LodePNG_Info struct IS used by the encoder though!
947 
948 *) palette:
949 
950 This is a dynamically allocated unsigned char array with the colors of the palette. The value palettesize
951 indicates the amount of colors in the palette. The allocated size of the buffer is 4 * palettesize bytes,
952 because there are 4 values per color: R, G, B and A. Even if less color channels are used, the palette
953 is always in RGBA format, in the order RGBARGBARGBA.....
954 
955 When encoding a PNG, to store your colors in the palette of the LodePNG_InfoRaw, first use
956 LodePNG_InfoColor_clearPalette, then for each color use LodePNG_InfoColor_addPalette.
957 In the C++ version the Encoder class also has the above functions available directly in its interface.
958 
959 Note that the palette information from the tRNS chunk is also already included in this palette vector.
960 
961 If you encode an image with palette, don't forget that you have to set the alpha channels (A) of the palette
962 too, set them to 255 for an opaque palette. If you leave them at zero, the image will be encoded as
963 fully invisible. This both for the palette in the infoRaw and the infoPng if the png is to have a palette.
964 
965 *) transparent color key
966 
967 key_defined: is a transparent color key given?
968 key_r: red/greyscale component of color key
969 key_g: green component of color key
970 key_b: blue component of color key
971 
972 For greyscale PNGs, r, g and b will all 3 be set to the same.
973 
974 This color is 8-bit for 8-bit PNGs, 16-bit for 16-bit per channel PNGs.
975 
976 *) suggested background color
977 
978 background_defined: is a suggested background color given?
979 background_r: red component of sugg. background color
980 background_g: green component of sugg. background color
981 background_b: blue component of sugg. background color
982 
983 This color is 8-bit for 8-bit PNGs, 16-bit for 16-bit PNGs
984 
985 For greyscale PNGs, r, g and b will all 3 be set to the same. When encoding
986 the encoder writes the red one away.
987 For palette PNGs: When decoding, the RGB value will be stored, no a palette
988 index. But when encoding, specify the index of the palette in background_r,
989 the other two are then ignored.
990 
991 The decoder pretty much ignores this background color, after all if you make a
992 PNG translucent normally you intend it to be used against any background, on
993 websites, as translucent textures in games, ... But you can get the color this
994 way if needed.
995 
996 *) text and itext
997 
998 Non-international text:
999 
1000 -text.keys: a char** buffer containing the keywords (see below)
1001 -text.strings: a char** buffer containing the texts (see below)
1002 -text.num: the amount of texts in the above char** buffers (there may be more texts in itext)
1003 -LodePNG_InfoText_clearText: use this to clear the texts again after you filled them in
1004 -LodePNG_InfoText_addText: this function is used to push back a keyword and text
1005 
1006 International text: This is stored in separate arrays! The sum text.num and itext.num is the real amount of texts.
1007 
1008 -itext.keys: keyword in English
1009 -itext.langtags: ISO 639 letter code for the language
1010 -itext.transkeys: keyword in this language
1011 -itext.strings: the text in this language, in UTF-8
1012 -itext.num: the amount of international texts in this PNG
1013 -LodePNG_InfoIText_clearText: use this to clear the itexts again after you filled them in
1014 -LodePNG_InfoIText_addText: this function is used to push back all 4 parts of an itext
1015 
1016 Don't allocate these text buffers yourself. Use the init/cleanup functions
1017 correctly and use addText and clearText.
1018 
1019 In the C++ version the Encoder class also has the above functions available directly in its interface.
1020 The char** buffers are used like the argv parameter of a main() function, and (i)text.num takes the role
1021 of argc.
1022 
1023 In a text, there must be as much keys as strings because they always form pairs. In an itext,
1024 there must always be as much keys, langtags, transkeys and strings.
1025 
1026 They keyword of text chunks gives a short description what the actual text
1027 represents. There are a few standard standard keywords recognised
1028 by many programs: Title, Author, Description, Copyright, Creation Time,
1029 Software, Disclaimer, Warning, Source, Comment. It's allowed to use other keys.
1030 
1031 The keyword is minimum 1 character and maximum 79 characters long. It's
1032 discouraged to use a single line length longer than 79 characters for texts.
1033 
1034 *) additional color info
1035 
1036 These functions are available with longer names in the C version, and directly
1037 in the Decoder's interface in the C++ version.
1038 
1039 getBpp(): bits per pixel of the PNG image
1040 getChannels(): amount of color channels of the PNG image
1041 isGreyscaleType(): its color type 0 or 4
1042 isAlphaType(): its color type 2 or 6
1043 
1044 These values are calculated out of color type and bit depth of InfoColor.
1045 
1046 The difference between bits per pixel and bit depth is that bit depth is the
1047 number of bits per color channel, while a pixel can have multiple channels.
1048 
1049 *) pHYs chunk (image dimensions)
1050 
1051 phys_defined: if 0, there is no pHYs chunk and the values are undefined, if 1 else there is one
1052 phys_x: pixels per unit in x direction
1053 phys_y: pixels per unit in y direction
1054 phys_unit: the unit, 0 is no unit (x and y only give the ratio), 1 is metre
1055 
1056 *) tIME chunk (modification time)
1057 
1058 time_defined: if 0, there is no tIME chunk and the values are undefined, if 1 there is one
1059 time: this struct contains year as a 2-byte number (0-65535), month, day, hour, minute,
1060 second as 1-byte numbers that must be in the correct range
1061 
1062 Note: to make the encoder add a time chunk, set time_defined to 1 and fill in
1063 the correct values in all the time parameters, LodePNG will not fill the current
1064 time in these values itself, all it does is copy them over into the chunk bytes.
1065 
1066 
1067 9. error values
1068 ---------------
1069 
1070 The meanings of the LodePNG error values:
1071 
1072 *) 0: no error, everything went ok
1073 *) 1: the Encoder/Decoder has done nothing yet, so error checking makes no sense yet
1074 *) 10: while huffman decoding: end of input memory reached without endcode
1075 *) 11: while huffman decoding: error in code tree made it jump outside of tree
1076 *) 13: problem while processing dynamic deflate block
1077 *) 14: problem while processing dynamic deflate block
1078 *) 15: problem while processing dynamic deflate block
1079 *) 16: unexisting code while processing dynamic deflate block
1080 *) 17: while inflating: end of out buffer memory reached
1081 *) 18: while inflating: invalid distance code
1082 *) 19: while inflating: end of out buffer memory reached
1083 *) 20: invalid deflate block BTYPE encountered while decoding
1084 *) 21: NLEN is not ones complement of LEN in a deflate block
1085 *) 22: while inflating: end of out buffer memory reached.
1086  This can happen if the inflated deflate data is longer than the amount of bytes required to fill up
1087  all the pixels of the image, given the color depth and image dimensions. Something that doesn't
1088  happen in a normal, well encoded, PNG image.
1089 *) 23: while inflating: end of in buffer memory reached
1090 *) 24: invalid FCHECK in zlib header
1091 *) 25: invalid compression method in zlib header
1092 *) 26: FDICT encountered in zlib header while it's not used for PNG
1093 *) 27: PNG file is smaller than a PNG header
1094 *) 28: incorrect PNG signature (the first 8 bytes of the PNG file)
1095  Maybe it's not a PNG, or a PNG file that got corrupted so that the header indicates the corruption.
1096 *) 29: first chunk is not the header chunk
1097 *) 30: chunk length too large, chunk broken off at end of file
1098 *) 31: illegal PNG color type or bpp
1099 *) 32: illegal PNG compression method
1100 *) 33: illegal PNG filter method
1101 *) 34: illegal PNG interlace method
1102 *) 35: chunk length of a chunk is too large or the chunk too small
1103 *) 36: illegal PNG filter type encountered
1104 *) 37: illegal bit depth for this color type given
1105 *) 38: the palette is too big (more than 256 colors)
1106 *) 39: more palette alpha values given in tRNS, than there are colors in the palette
1107 *) 40: tRNS chunk has wrong size for greyscale image
1108 *) 41: tRNS chunk has wrong size for RGB image
1109 *) 42: tRNS chunk appeared while it was not allowed for this color type
1110 *) 43: bKGD chunk has wrong size for palette image
1111 *) 44: bKGD chunk has wrong size for greyscale image
1112 *) 45: bKGD chunk has wrong size for RGB image
1113 *) 46: value encountered in indexed image is larger than the palette size (bitdepth == 8). Is the palette too small?
1114 *) 47: value encountered in indexed image is larger than the palette size (bitdepth < 8). Is the palette too small?
1115 *) 48: the input data is empty. Maybe a PNG file you tried to load doesn't exist or is in the wrong path.
1116 *) 49: jumped past memory while generating dynamic huffman tree
1117 *) 50: jumped past memory while generating dynamic huffman tree
1118 *) 51: jumped past memory while inflating huffman block
1119 *) 52: jumped past memory while inflating
1120 *) 53: size of zlib data too small
1121 *) 55: jumped past tree while generating huffman tree, this could be when the
1122  tree will have more leaves than symbols after generating it out of the
1123  given lengths. They call this an oversubscribed dynamic bit lengths tree in zlib.
1124 *) 56: given output image colorType or bitDepth not supported for color conversion
1125 *) 57: invalid CRC encountered (checking CRC can be disabled)
1126 *) 58: invalid ADLER32 encountered (checking ADLER32 can be disabled)
1127 *) 59: conversion to unexisting or unsupported color type or bit depth requested by encoder or decoder
1128 *) 60: invalid window size given in the settings of the encoder (must be 0-32768)
1129 *) 61: invalid BTYPE given in the settings of the encoder (only 0, 1 and 2 are allowed)
1130 *) 62: conversion from non-greyscale color to greyscale color requested by encoder or decoder. LodePNG
1131  leaves the choice of RGB to greyscale conversion formula to the user.
1132 *) 63: length of a chunk too long, max allowed for PNG is 2147483647 bytes per chunk (2^31-1)
1133 *) 64: the length of the "end" symbol 256 in the Huffman tree is 0, resulting in the inability of a deflated
1134  block to ever contain an end code. It must be at least 1.
1135 *) 66: the length of a text chunk keyword given to the encoder is longer than the maximum 79 bytes.
1136 *) 67: the length of a text chunk keyword given to the encoder is smaller than the minimum 1 byte.
1137 *) 68: tried to encode a PLTE chunk with a palette that has less than 1 or more than 256 colors
1138 *) 69: unknown chunk type with "critical" flag encountered by the decoder
1139 *) 71: unexisting interlace mode given to encoder (must be 0 or 1)
1140 *) 72: while decoding, unexisting compression method encountering in zTXt or iTXt chunk (it must be 0)
1141 *) 73: invalid tIME chunk size
1142 *) 74: invalid pHYs chunk size
1143 *) 75: no null termination char found while decoding any kind of text chunk, or wrong length
1144 *) 76: iTXt chunk too short to contain required bytes
1145 *) 77: integer overflow in buffer size happened somewhere
1146 *) 78: file doesn't exist or couldn't be opened for reading
1147 *) 79: file couldn't be opened for writing
1148 *) 80: tried creating a tree for 0 symbols
1149 *) 9900-9999: out of memory while allocating chunk of memory somewhere
1150 
1151 
1152 10. file IO
1153 -----------
1154 
1155 For cases where you want to load the PNG image from a file, you can use your own
1156 file loading code, or the file loading and saving functions provided with
1157 LodePNG. These use the same unsigned char format used by the Decoder and Encoder.
1158 
1159 The loadFile function fills the given buffer up with the file from harddisk
1160 with the given name.
1161 
1162 The saveFile function saves the contents of the given buffer to the file
1163 with given name. Warning: this overwrites the contents that were previously in
1164 the file if it already existed, without warning.
1165 
1166 Note that you don't have to decode a PNG image from a file, you can as well
1167 retrieve the buffer another way in your code, because the decode function takes
1168 a buffer as parameter, not a filename.
1169 
1170 Both C and C++ versions of the loadFile and saveFile functions are available.
1171 For the C version of loadFile, you need to free() the buffer after use. The
1172 C++ versions use std::vectors so they clean themselves automatically.
1173 
1174 
1175 11. chunks and PNG editing
1176 --------------------------
1177 
1178 If you want to add extra chunks to a PNG you encode, or use LodePNG for a PNG
1179 editor that should follow the rules about handling of unknown chunks, or if you
1180 program is able to read other types of chunks than the ones handled by LodePNG,
1181 then that's possible with the chunk functions of LodePNG.
1182 
1183 A PNG chunk has the following layout:
1184 
1185 4 bytes length
1186 4 bytes type name
1187 length bytes data
1188 4 bytes CRC
1189 
1190 
1191 11.1 iterating through chunks
1192 -----------------------------
1193 
1194 If you have a buffer containing the PNG image data, then the first chunk (the
1195 IHDR chunk) starts at byte number 8 of that buffer. The first 8 bytes are the
1196 signature of the PNG and are not part of a chunk. But if you start at byte 8
1197 then you have a chunk, and can check the following things of it.
1198 
1199 NOTE: none of these functions check for memory buffer boundaries. To avoid
1200 exploits, always make sure the buffer contains all the data of the chunks.
1201 When using LodePNG_chunk_next, make sure the returned value is within the
1202 allocated memory.
1203 
1204 unsigned LodePNG_chunk_length(const unsigned char* chunk):
1205 
1206 Get the length of the chunk's data. The total chunk length is this length + 12.
1207 
1208 void LodePNG_chunk_type(char type[5], const unsigned char* chunk):
1209 unsigned char LodePNG_chunk_type_equals(const unsigned char* chunk, const char* type):
1210 
1211 Get the type of the chunk or compare if it's a certain type
1212 
1213 unsigned char LodePNG_chunk_critical(const unsigned char* chunk):
1214 unsigned char LodePNG_chunk_private(const unsigned char* chunk):
1215 unsigned char LodePNG_chunk_safetocopy(const unsigned char* chunk):
1216 
1217 Check if the chunk is critical in the PNG standard (only IHDR, PLTE, IDAT and IEND are).
1218 Check if the chunk is private (public chunks are part of the standard, private ones not).
1219 Check if the chunk is safe to copy. If it's not, then, when modifying data in a critical
1220 chunk, unsafe to copy chunks of the old image may NOT be saved in the new one if your
1221 program doesn't handle that type of unknown chunk.
1222 
1223 unsigned char* LodePNG_chunk_data(unsigned char* chunk):
1224 const unsigned char* LodePNG_chunk_data_const(const unsigned char* chunk):
1225 
1226 Get a pointer to the start of the data of the chunk.
1227 
1228 unsigned LodePNG_chunk_check_crc(const unsigned char* chunk):
1229 void LodePNG_chunk_generate_crc(unsigned char* chunk):
1230 
1231 Check if the crc is correct or generate a correct one.
1232 
1233 unsigned char* LodePNG_chunk_next(unsigned char* chunk):
1234 const unsigned char* LodePNG_chunk_next_const(const unsigned char* chunk):
1235 
1236 Iterate to the next chunk. This works if you have a buffer with consecutive chunks. Note that these
1237 functions do no boundary checking of the allocated data whatsoever, so make sure there is enough
1238 data available in the buffer to be able to go to the next chunk.
1239 
1240 unsigned LodePNG_append_chunk(unsigned char** out, size_t* outlength, const unsigned char* chunk):
1241 unsigned LodePNG_create_chunk(unsigned char** out, size_t* outlength, unsigned length, const char* type, const unsigned char* data):
1242 
1243 These functions are used to create new chunks that are appended to the data in *out that has
1244 length *outlength. The append function appends an existing chunk to the new data. The create
1245 function creates a new chunk with the given parameters and appends it. Type is the 4-letter
1246 name of the chunk.
1247 
1248 
1249 11.2 chunks in infoPng
1250 ----------------------
1251 
1252 The LodePNG_InfoPng struct contains a struct LodePNG_UnknownChunks in it. This
1253 struct has 3 buffers (each with size) to contain 3 types of unknown chunks:
1254 the ones that come before the PLTE chunk, the ones that come between the PLTE
1255 and the IDAT chunks, and the ones that come after the IDAT chunks.
1256 It's necessary to make the distionction between these 3 cases because the PNG
1257 standard forces to keep the ordering of unknown chunks compared to the critical
1258 chunks, but does not force any other ordering rules.
1259 
1260 infoPng.unknown_chunks.data[0] is the chunks before PLTE
1261 infoPng.unknown_chunks.data[1] is the chunks after PLTE, before IDAT
1262 infoPng.unknown_chunks.data[2] is the chunks after IDAT
1263 
1264 The chunks in these 3 buffers can be iterated through and read by using the same
1265 way described in the previous subchapter.
1266 
1267 When using the decoder to decode a PNG, you can make it store all unknown chunks
1268 if you set the option settings.rememberUnknownChunks to 1. By default, this option
1269 is off and is 0.
1270 
1271 The encoder will always encode unknown chunks that are stored in the infoPng. If
1272 you need it to add a particular chunk that isn't known by LodePNG, you can use
1273 LodePNG_append_chunk or LodePNG_create_chunk to the chunk data in
1274 infoPng.unknown_chunks.data[x].
1275 
1276 Chunks that are known by LodePNG should not be added in that way. E.g. to make
1277 LodePNG add a bKGD chunk, set background_defined to true and add the correct
1278 parameters there and LodePNG will generate the chunk.
1279 
1280 
1281 12. compiler support
1282 --------------------
1283 
1284 No libraries other than the current standard C library are needed to compile
1285 LodePNG. For the C++ version, only the standard C++ library is needed on top.
1286 Add the files lodepng.c(pp) and lodepng.h to your project, include
1287 lodepng.h where needed, and your program can read/write PNG files.
1288 
1289 Use optimization! For both the encoder and decoder, compiling with the best
1290 optimizations makes a large difference.
1291 
1292 Make sure that LodePNG is compiled with the same compiler of the same version
1293 and with the same settings as the rest of the program, or the interfaces with
1294 std::vectors and std::strings in C++ can be incompatible resulting in bad things.
1295 
1296 CHAR_BITS must be 8 or higher, because LodePNG uses unsigned chars for octets.
1297 
1298 *) gcc and g++
1299 
1300 LodePNG is developed in gcc so this compiler is natively supported. It gives no
1301 warnings with compiler options "-Wall -Wextra -pedantic -ansi", with gcc and g++
1302 version 4.2.2 on Linux.
1303 
1304 *) Mingw and Bloodshed DevC++
1305 
1306 The Mingw compiler (a port of gcc) used by Bloodshed DevC++ for Windows is fully
1307 supported by LodePNG.
1308 
1309 *) Visual Studio 2005 and Visual C++ 2005 Express Edition
1310 
1311 Versions 20070604 up to 20080107 have been tested on VS2005 and work. There are no
1312 warnings, except two warnings about 'fopen' being deprecated. 'fopen' is a function
1313 required by the C standard, so this warning is the fault of VS2005, it's nice of
1314 them to enforce secure code, however the multiplatform LodePNG can't follow their
1315 non-standard extensions. LodePNG is fully ISO C90 compliant.
1316 
1317 If you're using LodePNG in VS2005 and don't want to see the deprecated warnings,
1318 put this on top of lodepng.h before the inclusions: #define _CRT_SECURE_NO_DEPRECATE
1319 
1320 *) Visual Studio 6.0
1321 
1322 The C++ version of LodePNG was not supported by Visual Studio 6.0 because Visual
1323 Studio 6.0 doesn't follow the C++ standard and implements it incorrectly.
1324 The current C version of LodePNG has not been tested in VS6 but may work now.
1325 
1326 *) Comeau C/C++
1327 
1328 Vesion 20070107 compiles without problems on the Comeau C/C++ Online Test Drive
1329 at http://www.comeaucomputing.com/tryitout in both C90 and C++ mode.
1330 
1331 *) Compilers on Macintosh
1332 
1333 I'd love to support Macintosh but don't have one available to test it on.
1334 If it doesn't work with your compiler, maybe it can be gotten to work with the
1335 gcc compiler for Macintosh. Someone reported that it doesn't work well at all
1336 for Macintosh. All information on attempts to get it to work on Mac is welcome.
1337 
1338 *) Other Compilers
1339 
1340 If you encounter problems on other compilers, I'm happy to help out make LodePNG
1341 support the compiler if it supports the ISO C90 and C++ standard well enough. If
1342 the required modification to support the compiler requires using non standard or
1343 lesser C/C++ code or headers, I won't support it.
1344 
1345 
1346 13. examples
1347 ------------
1348 
1349 This decoder and encoder example show the most basic usage of LodePNG (using the
1350 classes, not the simple functions, which would be trivial)
1351 
1352 More complex examples can be found in:
1353 -lodepng_examples.c: 9 different examples in C, such as showing the image with SDL, ...
1354 -lodepng_examples.cpp: the exact same examples in C++ using the C++ wrapper of LodePNG
1355 
1356 
1357 13.1. decoder C++ example
1358 -------------------------
1359 
1360 ////////////////////////////////////////////////////////////////////////////////
1361 #include "lodepng.h"
1362 #include <iostream>
1363 
1364 int main(int argc, char *argv[])
1365 {
1366  const char* filename = argc > 1 ? argv[1] : "test.png";
1367 
1368  //load and decode
1369  std::vector<unsigned char> buffer, image;
1370  LodePNG::loadFile(buffer, filename); //load the image file with given filename
1371  LodePNG::Decoder decoder;
1372  decoder.decode(image, buffer.size() ? &buffer[0] : 0, (unsigned)buffer.size()); //decode the png
1373 
1374  //if there's an error, display it
1375  if(decoder.hasError()) std::cout << "error: " << decoder.getError() << std::endl;
1376 
1377  //the pixels are now in the vector "image", use it as texture, draw it, ...
1378 }
1379 
1380 //alternative version using the "simple" function
1381 int main(int argc, char *argv[])
1382 {
1383  const char* filename = argc > 1 ? argv[1] : "test.png";
1384 
1385  //load and decode
1386  std::vector<unsigned char> image;
1387  unsigned w, h;
1388  unsigned error = LodePNG::decode(image, w, h, filename);
1389 
1390  //if there's an error, display it
1391  if(error != 0) std::cout << "error: " << error << std::endl;
1392 
1393  //the pixels are now in the vector "image", use it as texture, draw it, ...
1394 }
1395 ////////////////////////////////////////////////////////////////////////////////
1396 
1397 
1398 13.2 encoder C++ example
1399 ------------------------
1400 
1401 ////////////////////////////////////////////////////////////////////////////////
1402 #include "lodepng.h"
1403 #include <iostream>
1404 
1405 int main(int argc, char *argv[])
1406 {
1407  //check if user gave a filename
1408  if(argc <= 1)
1409  {
1410  std::cout << "please provide a filename to save to\n";
1411  return 0;
1412  }
1413 
1414  //generate some image
1415  std::vector<unsigned char> image;
1416  image.resize(512 * 512 * 4);
1417  for(unsigned y = 0; y < 512; y++)
1418  for(unsigned x = 0; x < 512; x++)
1419  {
1420  image[4 * 512 * y + 4 * x + 0] = 255 * !(x & y);
1421  image[4 * 512 * y + 4 * x + 1] = x ^ y;
1422  image[4 * 512 * y + 4 * x + 2] = x | y;
1423  image[4 * 512 * y + 4 * x + 3] = 255;
1424  }
1425 
1426  //encode and save
1427  std::vector<unsigned char> buffer;
1428  LodePNG::Encoder encoder;
1429  encoder.encode(buffer, image, 512, 512);
1430  LodePNG::saveFile(buffer, argv[1]);
1431 
1432  //the same as the 4 lines of code above, but in 1 call:
1433  //LodePNG::encode(argv[1], image, 512, 512);
1434 }
1435 ////////////////////////////////////////////////////////////////////////////////
1436 
1437 
1438 13.3 Decoder C example
1439 ----------------------
1440 
1441 This example loads the PNG in 1 function call
1442 
1443 #include "lodepng.h"
1444 
1445 int main(int argc, char *argv[])
1446 {
1447  unsigned error;
1448  unsigned char* image;
1449  size_t w, h;
1450 
1451  if(argc <= 1) return 0;
1452 
1453  error = LodePNG_decode3(&image, &w, &h, filename);
1454 
1455  free(image);
1456 }
1457 
1458 
1459 14. LodeZlib
1460 ------------
1461 
1462 Also available in the interface is LodeZlib. Both C and C++ versions of these
1463 functions are available. The interface is similar to that of the "simple" PNG
1464 encoding and decoding functions.
1465 
1466 LodeZlib can be used to zlib compress and decompress a buffer. It cannot be
1467 used to create gzip files however. Also, it only supports the part of zlib
1468 that is required for PNG, it does not support compression and decompression
1469 with dictionaries.
1470 
1471 
1472 15. changes
1473 -----------
1474 
1475 The version number of LodePNG is the date of the change given in the format
1476 yyyymmdd.
1477 
1478 Some changes aren't backwards compatible. Those are indicated with a (!)
1479 symbol.
1480 
1481 *) 02 sep 2008: fixed bug where it could create empty tree that linux apps could
1482  read by ignoring the problem but windows apps couldn't.
1483 *) 06 jun 2008: added more error checks for out of memory cases.
1484 *) 26 apr 2008: added a few more checks here and there to ensure more safety.
1485 *) 06 mar 2008: crash with encoding of strings fixed
1486 *) 02 feb 2008: support for international text chunks added (iTXt)
1487 *) 23 jan 2008: small cleanups, and #defines to divide code in sections
1488 *) 20 jan 2008: support for unknown chunks allowing using LodePNG for an editor.
1489 *) 18 jan 2008: support for tIME and pHYs chunks added to encoder and decoder.
1490 *) 17 jan 2008: ability to encode and decode compressed zTXt chunks added
1491  Also vareous fixes, such as in the deflate and the padding bits code.
1492 *) 13 jan 2008: Added ability to encode Adam7-interlaced images. Improved
1493  filtering code of encoder.
1494 *) 07 jan 2008: (!) changed LodePNG to use ISO C90 instead of C++. A
1495  C++ wrapper around this provides an interface almost identical to before.
1496  Having LodePNG be pure ISO C90 makes it more portable. The C and C++ code
1497  are together in these files but it works both for C and C++ compilers.
1498 *) 29 dec 2007: (!) changed most integer types to unsigned int + other tweaks
1499 *) 30 aug 2007: bug fixed which makes this Borland C++ compatible
1500 *) 09 aug 2007: some VS2005 warnings removed again
1501 *) 21 jul 2007: deflate code placed in new namespace separate from zlib code
1502 *) 08 jun 2007: fixed bug with 2- and 4-bit color, and small interlaced images
1503 *) 04 jun 2007: improved support for Visual Studio 2005: crash with accessing
1504  invalid std::vector element [0] fixed, and level 3 and 4 warnings removed
1505 *) 02 jun 2007: made the encoder add a tag with version by default
1506 *) 27 may 2007: zlib and png code separated (but still in the same file),
1507  simple encoder/decoder functions added for more simple usage cases
1508 *) 19 may 2007: minor fixes, some code cleaning, new error added (error 69),
1509  moved some examples from here to lodepng_examples.cpp
1510 *) 12 may 2007: palette decoding bug fixed
1511 *) 24 apr 2007: changed the license from BSD to the zlib license
1512 *) 11 mar 2007: very simple addition: ability to encode bKGD chunks.
1513 *) 04 mar 2007: (!) tEXt chunk related fixes, and support for encoding
1514  palettized PNG images. Plus little interface change with palette and texts.
1515 *) 03 mar 2007: Made it encode dynamic Huffman shorter with repeat codes.
1516  Fixed a bug where the end code of a block had length 0 in the Huffman tree.
1517 *) 26 feb 2007: Huffman compression with dynamic trees (BTYPE 2) now implemented
1518  and supported by the encoder, resulting in smaller PNGs at the output.
1519 *) 27 jan 2007: Made the Adler-32 test faster so that a timewaste is gone.
1520 *) 24 jan 2007: gave encoder an error interface. Added color conversion from any
1521  greyscale type to 8-bit greyscale with or without alpha.
1522 *) 21 jan 2007: (!) Totally changed the interface. It allows more color types
1523  to convert to and is more uniform. See the manual for how it works now.
1524 *) 07 jan 2007: Some cleanup & fixes, and a few changes over the last days:
1525  encode/decode custom tEXt chunks, separate classes for zlib & deflate, and
1526  at last made the decoder give errors for incorrect Adler32 or Crc.
1527 *) 01 jan 2007: Fixed bug with encoding PNGs with less than 8 bits per channel.
1528 *) 29 dec 2006: Added support for encoding images without alpha channel, and
1529  cleaned out code as well as making certain parts faster.
1530 *) 28 dec 2006: Added "Settings" to the encoder.
1531 *) 26 dec 2006: The encoder now does LZ77 encoding and produces much smaller files now.
1532  Removed some code duplication in the decoder. Fixed little bug in an example.
1533 *) 09 dec 2006: (!) Placed output parameters of public functions as first parameter.
1534  Fixed a bug of the decoder with 16-bit per color.
1535 *) 15 okt 2006: Changed documentation structure
1536 *) 09 okt 2006: Encoder class added. It encodes a valid PNG image from the
1537  given image buffer, however for now it's not compressed.
1538 *) 08 sep 2006: (!) Changed to interface with a Decoder class
1539 *) 30 jul 2006: (!) LodePNG_InfoPng , width and height are now retrieved in different
1540  way. Renamed decodePNG to decodePNGGeneric.
1541 *) 29 jul 2006: (!) Changed the interface: image info is now returned as a
1542  struct of type LodePNG::LodePNG_Info, instead of a vector, which was a bit clumsy.
1543 *) 28 jul 2006: Cleaned the code and added new error checks.
1544  Corrected terminology "deflate" into "inflate".
1545 *) 23 jun 2006: Added SDL example in the documentation in the header, this
1546  example allows easy debugging by displaying the PNG and its transparency.
1547 *) 22 jun 2006: (!) Changed way to obtain error value. Added
1548  loadFile function for convenience. Made decodePNG32 faster.
1549 *) 21 jun 2006: (!) Changed type of info vector to unsigned.
1550  Changed position of palette in info vector. Fixed an important bug that
1551  happened on PNGs with an uncompressed block.
1552 *) 16 jun 2006: Internally changed unsigned into unsigned where
1553  needed, and performed some optimizations.
1554 *) 07 jun 2006: (!) Renamed functions to decodePNG and placed them
1555  in LodePNG namespace. Changed the order of the parameters. Rewrote the
1556  documentation in the header. Renamed files to lodepng.cpp and lodepng.h
1557 *) 22 apr 2006: Optimized and improved some code
1558 *) 07 sep 2005: (!) Changed to std::vector interface
1559 *) 12 aug 2005: Initial release
1560 
1561 
1562 16. contact information
1563 -----------------------
1564 
1565 Feel free to contact me with suggestions, problems, comments, ... concerning
1566 LodePNG. If you encounter a PNG image that doesn't work properly with this
1567 decoder, feel free to send it and I'll use it to find and fix the problem.
1568 
1569 My email address is (puzzle the account and domain together with an @ symbol):
1570 Domain: gmail dot com.
1571 Account: lode dot vandevenne.
1572 
1573 
1574 Copyright (c) 2005-2008 Lode Vandevenne
1575 */
size_t palettesize
Definition: lodepng.h:132
void LodePNG_chunk_generate_crc(unsigned char *chunk)
Definition: lodepng.cpp:1918
const unsigned char * LodePNG_chunk_data_const(const unsigned char *chunk)
Definition: lodepng.cpp:1904
unsigned LodePNG_InfoColor_isAlphaType(const LodePNG_InfoColor *info)
Definition: lodepng.cpp:2069
unsigned LodePNG_chunk_length(const unsigned char *chunk)
Definition: lodepng.cpp:1865
void LodePNG_chunk_type(char type[5], const unsigned char *chunk)
Definition: lodepng.cpp:1870
struct LodePNG_InfoPng LodePNG_InfoPng
unsigned colorType
Definition: lodepng.h:127
LodePNG_InfoRaw infoRaw
Definition: lodepng.h:342
static constexpr double g
Definition: Units.h:144
unsigned LodePNG_encode32(unsigned char **out, size_t *outsize, const unsigned char *image, unsigned w, unsigned h)
Definition: lodepng.cpp:4042
const LodeZlib_DeflateSettings LodeZlib_defaultDeflateSettings
Definition: lodepng.cpp:1704
unsigned char LodePNG_chunk_private(const unsigned char *chunk)
Definition: lodepng.cpp:1889
unsigned compressionMethod
Definition: lodepng.h:222
unsigned LodePNG_chunk_check_crc(const unsigned char *chunk)
Definition: lodepng.cpp:1909
void LodeZlib_DeflateSettings_init(LodeZlib_DeflateSettings *settings)
Definition: lodepng.cpp:1697
unsigned bitDepth
Definition: lodepng.h:128
unsigned char LodePNG_chunk_safetocopy(const unsigned char *chunk)
Definition: lodepng.cpp:1894
unsigned interlaceMethod
Definition: lodepng.h:224
LodePNG_InfoColor color
Definition: lodepng.h:225
void LodePNG_Encoder_cleanup(LodePNG_Encoder *encoder)
Definition: lodepng.cpp:4084
unsigned LodePNG_InfoColor_getBpp(const LodePNG_InfoColor *info)
Definition: lodepng.cpp:2066
unsigned LodeZlib_compress(unsigned char **out, size_t *outsize, const unsigned char *in, size_t insize, const LodeZlib_DeflateSettings *settings)
Definition: lodepng.cpp:1651
unsigned LodePNG_encode32f(const char *filename, const unsigned char *image, unsigned w, unsigned h)
Definition: lodepng.cpp:4054
unsigned LodePNG_InfoColor_copy(LodePNG_InfoColor *dest, const LodePNG_InfoColor *source)
Definition: lodepng.cpp:2323
void LodePNG_EncodeSettings_init(LodePNG_EncodeSettings *settings)
Definition: lodepng.cpp:4065
LodePNG_EncodeSettings settings
Definition: lodepng.h:340
unsigned LodePNG_loadFile(unsigned char **out, size_t *outsize, const char *filename)
Definition: lodepng.cpp:4110
unsigned char * LodePNG_chunk_data(unsigned char *chunk)
Definition: lodepng.cpp:1899
error
Definition: include.cc:26
void LodePNG_InfoPng_cleanup(LodePNG_InfoPng *info)
Definition: lodepng.cpp:2284
unsigned key_r
Definition: lodepng.h:136
unsigned force_palette
Definition: lodepng.h:329
unsigned char * LodePNG_chunk_next(unsigned char *chunk)
Definition: lodepng.cpp:1925
string filename
Definition: train.py:213
unsigned char LodePNG_chunk_critical(const unsigned char *chunk)
Definition: lodepng.cpp:1884
void LodePNG_InfoRaw_init(LodePNG_InfoRaw *info)
Definition: lodepng.cpp:2334
unsigned filterMethod
Definition: lodepng.h:223
unsigned LodePNG_InfoColor_addPalette(LodePNG_InfoColor *info, unsigned char r, unsigned char g, unsigned char b, unsigned char a)
Definition: lodepng.cpp:2046
void LodePNG_InfoPng_init(LodePNG_InfoPng *info)
Definition: lodepng.cpp:2262
void LodePNG_Encoder_copy(LodePNG_Encoder *dest, const LodePNG_Encoder *source)
Definition: lodepng.cpp:4090
unsigned LodePNG_InfoColor_getChannels(const LodePNG_InfoColor *info)
Definition: lodepng.cpp:2067
decltype(auto) constexpr size(T &&obj)
ADL-aware version of std::size.
Definition: StdUtils.h:92
unsigned LodePNG_InfoPng_copy(LodePNG_InfoPng *dest, const LodePNG_InfoPng *source)
Definition: lodepng.cpp:2296
static QFile::DecoderFn decoder
Definition: qfile.cpp:522
def key(type, name=None)
Definition: graph.py:13
unsigned LodePNG_convert(unsigned char *out, const unsigned char *in, LodePNG_InfoColor *infoOut, LodePNG_InfoColor *infoIn, unsigned w, unsigned h)
Definition: lodepng.cpp:2361
LodeZlib_DeflateSettings zlibsettings
Definition: lodepng.h:326
unsigned LodePNG_create_chunk(unsigned char **out, size_t *outlength, unsigned length, const char *type, const unsigned char *data)
Definition: lodepng.cpp:1956
void LodePNG_InfoColor_clearPalette(LodePNG_InfoColor *info)
Definition: lodepng.cpp:2040
unsigned LodePNG_InfoColor_isGreyscaleType(const LodePNG_InfoColor *info)
Definition: lodepng.cpp:2068
const double a
void LodePNG_InfoColor_cleanup(LodePNG_InfoColor *info)
Definition: lodepng.cpp:2035
LodePNG_InfoColor color
Definition: lodepng.h:266
const unsigned char * LodePNG_chunk_next_const(const unsigned char *chunk)
Definition: lodepng.cpp:1931
struct LodePNG_EncodeSettings LodePNG_EncodeSettings
unsigned LodePNG_append_chunk(unsigned char **out, size_t *outlength, const unsigned char *chunk)
Definition: lodepng.cpp:1937
unsigned height
Definition: lodepng.h:221
struct LodeZlib_DeflateSettings LodeZlib_DeflateSettings
void LodePNG_encode(LodePNG_Encoder *encoder, unsigned char **out, size_t *outsize, const unsigned char *image, unsigned w, unsigned h)
Definition: lodepng.cpp:3910
LodePNG_InfoPng infoPng
Definition: lodepng.h:341
unsigned key_defined
Definition: lodepng.h:135
unsigned LodePNG_saveFile(const unsigned char *buffer, size_t buffersize, const char *filename)
Definition: lodepng.cpp:4141
unsigned width
Definition: lodepng.h:220
unsigned LodePNG_InfoRaw_copy(LodePNG_InfoRaw *dest, const LodePNG_InfoRaw *source)
Definition: lodepng.cpp:2344
unsigned key_g
Definition: lodepng.h:137
static bool * b
Definition: config.cpp:1043
void LodePNG_Encoder_init(LodePNG_Encoder *encoder)
Definition: lodepng.cpp:4076
unsigned key_b
Definition: lodepng.h:138
unsigned char * palette
Definition: lodepng.h:131
second_as<> second
Type of time stored in seconds, in double precision.
Definition: spacetime.h:85
unsigned char LodePNG_chunk_type_equals(const unsigned char *chunk, const char *type)
Definition: lodepng.cpp:1877
struct LodePNG_Encoder LodePNG_Encoder
struct LodePNG_InfoColor LodePNG_InfoColor
static QFile::EncoderFn encoder
Definition: qfile.cpp:470
unsigned autoLeaveOutAlphaChannel
Definition: lodepng.h:328
static QCString str
void LodePNG_InfoRaw_cleanup(LodePNG_InfoRaw *info)
Definition: lodepng.cpp:2339
void LodePNG_InfoColor_init(LodePNG_InfoColor *info)
Definition: lodepng.cpp:2025
unsigned error
Definition: lodepng.h:343
struct LodePNG_InfoRaw LodePNG_InfoRaw