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1 /*
2 LodePNG version 20131222
3 
4 Copyright (c) 2005-2013 Lode Vandevenne
5 
6 This software is provided 'as-is', without any express or implied
7 warranty. In no event will the authors be held liable for any damages
8 arising from the use of this software.
9 
10 Permission is granted to anyone to use this software for any purpose,
11 including commercial applications, and to alter it and redistribute it
12 freely, subject to the following restrictions:
13 
14     1. The origin of this software must not be misrepresented; you must not
15     claim that you wrote the original software. If you use this software
16     in a product, an acknowledgment in the product documentation would be
17     appreciated but is not required.
18 
19     2. Altered source versions must be plainly marked as such, and must not be
20     misrepresented as being the original software.
21 
22     3. This notice may not be removed or altered from any source
23     distribution.
24 */
25 
26 #ifndef LODEPNG_H
27 #define LODEPNG_H
28 
29 #include <string.h> /*for size_t*/
30 
31 #ifdef __cplusplus
32 #include <vector>
33 #include <string>
34 #endif /*__cplusplus*/
35 
36 /*
37 The following #defines are used to create code sections. They can be disabled
38 to disable code sections, which can give faster compile time and smaller binary.
39 The "NO_COMPILE" defines are designed to be used to pass as defines to the
40 compiler command to disable them without modifying this header, e.g.
41 -DLODEPNG_NO_COMPILE_ZLIB for gcc.
42 */
43 /*deflate & zlib. If disabled, you must specify alternative zlib functions in
44 the custom_zlib field of the compress and decompress settings*/
45 #ifndef LODEPNG_NO_COMPILE_ZLIB
46 #define LODEPNG_COMPILE_ZLIB
47 #endif
48 /*png encoder and png decoder*/
49 #ifndef LODEPNG_NO_COMPILE_PNG
50 #define LODEPNG_COMPILE_PNG
51 #endif
52 /*deflate&zlib decoder and png decoder*/
53 #ifndef LODEPNG_NO_COMPILE_DECODER
54 #define LODEPNG_COMPILE_DECODER
55 #endif
56 /*deflate&zlib encoder and png encoder*/
57 #ifndef LODEPNG_NO_COMPILE_ENCODER
58 #define LODEPNG_COMPILE_ENCODER
59 #endif
60 /*the optional built in harddisk file loading and saving functions*/
61 #ifndef LODEPNG_NO_COMPILE_DISK
62 #define LODEPNG_COMPILE_DISK
63 #endif
64 /*support for chunks other than IHDR, IDAT, PLTE, tRNS, IEND: ancillary and unknown chunks*/
65 #ifndef LODEPNG_NO_COMPILE_ANCILLARY_CHUNKS
66 #define LODEPNG_COMPILE_ANCILLARY_CHUNKS
67 #endif
68 /*ability to convert error numerical codes to English text string*/
69 #ifndef LODEPNG_NO_COMPILE_ERROR_TEXT
70 #define LODEPNG_COMPILE_ERROR_TEXT
71 #endif
72 /*Compile the default allocators (C's free, malloc and realloc). If you disable this,
73 you can define the functions lodepng_free, lodepng_malloc and lodepng_realloc in your
74 source files with custom allocators.*/
75 #ifndef LODEPNG_NO_COMPILE_ALLOCATORS
76 #define LODEPNG_COMPILE_ALLOCATORS
77 #endif
78 /*compile the C++ version (you can disable the C++ wrapper here even when compiling for C++)*/
79 #ifdef __cplusplus
80 #ifndef LODEPNG_NO_COMPILE_CPP
81 #define LODEPNG_COMPILE_CPP
82 #endif
83 #endif
84 
85 #ifdef LODEPNG_COMPILE_PNG
86 /*The PNG color types (also used for raw).*/
87 typedef enum LodePNGColorType
88 {
89   LCT_GREY = 0, /*greyscale: 1,2,4,8,16 bit*/
90   LCT_RGB = 2, /*RGB: 8,16 bit*/
91   LCT_PALETTE = 3, /*palette: 1,2,4,8 bit*/
92   LCT_GREY_ALPHA = 4, /*greyscale with alpha: 8,16 bit*/
93   LCT_RGBA = 6 /*RGB with alpha: 8,16 bit*/
94 } LodePNGColorType;
95 
96 #ifdef LODEPNG_COMPILE_DECODER
97 /*
98 Converts PNG data in memory to raw pixel data.
99 out: Output parameter. Pointer to buffer that will contain the raw pixel data.
100      After decoding, its size is w * h * (bytes per pixel) bytes larger than
101      initially. Bytes per pixel depends on colortype and bitdepth.
102      Must be freed after usage with free(*out).
103      Note: for 16-bit per channel colors, uses big endian format like PNG does.
104 w: Output parameter. Pointer to width of pixel data.
105 h: Output parameter. Pointer to height of pixel data.
106 in: Memory buffer with the PNG file.
107 insize: size of the in buffer.
108 colortype: the desired color type for the raw output image. See explanation on PNG color types.
109 bitdepth: the desired bit depth for the raw output image. See explanation on PNG color types.
110 Return value: LodePNG error code (0 means no error).
111 */
112 unsigned lodepng_decode_memory(unsigned char** out, unsigned* w, unsigned* h,
113                                const unsigned char* in, size_t insize,
114                                LodePNGColorType colortype, unsigned bitdepth);
115 
116 /*Same as lodepng_decode_memory, but always decodes to 32-bit RGBA raw image*/
117 unsigned lodepng_decode32(unsigned char** out, unsigned* w, unsigned* h,
118                           const unsigned char* in, size_t insize);
119 
120 /*Same as lodepng_decode_memory, but always decodes to 24-bit RGB raw image*/
121 unsigned lodepng_decode24(unsigned char** out, unsigned* w, unsigned* h,
122                           const unsigned char* in, size_t insize);
123 
124 #ifdef LODEPNG_COMPILE_DISK
125 /*
126 Load PNG from disk, from file with given name.
127 Same as the other decode functions, but instead takes a filename as input.
128 */
129 unsigned lodepng_decode_file(unsigned char** out, unsigned* w, unsigned* h,
130                              const char* filename,
131                              LodePNGColorType colortype, unsigned bitdepth);
132 
133 /*Same as lodepng_decode_file, but always decodes to 32-bit RGBA raw image.*/
134 unsigned lodepng_decode32_file(unsigned char** out, unsigned* w, unsigned* h,
135                                const char* filename);
136 
137 /*Same as lodepng_decode_file, but always decodes to 24-bit RGB raw image.*/
138 unsigned lodepng_decode24_file(unsigned char** out, unsigned* w, unsigned* h,
139                                const char* filename);
140 #endif /*LODEPNG_COMPILE_DISK*/
141 #endif /*LODEPNG_COMPILE_DECODER*/
142 
143 
144 #ifdef LODEPNG_COMPILE_ENCODER
145 /*
146 Converts raw pixel data into a PNG image in memory. The colortype and bitdepth
147   of the output PNG image cannot be chosen, they are automatically determined
148   by the colortype, bitdepth and content of the input pixel data.
149   Note: for 16-bit per channel colors, needs big endian format like PNG does.
150 out: Output parameter. Pointer to buffer that will contain the PNG image data.
151      Must be freed after usage with free(*out).
152 outsize: Output parameter. Pointer to the size in bytes of the out buffer.
153 image: The raw pixel data to encode. The size of this buffer should be
154        w * h * (bytes per pixel), bytes per pixel depends on colortype and bitdepth.
155 w: width of the raw pixel data in pixels.
156 h: height of the raw pixel data in pixels.
157 colortype: the color type of the raw input image. See explanation on PNG color types.
158 bitdepth: the bit depth of the raw input image. See explanation on PNG color types.
159 Return value: LodePNG error code (0 means no error).
160 */
161 unsigned lodepng_encode_memory(unsigned char** out, size_t* outsize,
162                                const unsigned char* image, unsigned w, unsigned h,
163                                LodePNGColorType colortype, unsigned bitdepth);
164 
165 /*Same as lodepng_encode_memory, but always encodes from 32-bit RGBA raw image.*/
166 unsigned lodepng_encode32(unsigned char** out, size_t* outsize,
167                           const unsigned char* image, unsigned w, unsigned h);
168 
169 /*Same as lodepng_encode_memory, but always encodes from 24-bit RGB raw image.*/
170 unsigned lodepng_encode24(unsigned char** out, size_t* outsize,
171                           const unsigned char* image, unsigned w, unsigned h);
172 
173 #ifdef LODEPNG_COMPILE_DISK
174 /*
175 Converts raw pixel data into a PNG file on disk.
176 Same as the other encode functions, but instead takes a filename as output.
177 NOTE: This overwrites existing files without warning!
178 */
179 unsigned lodepng_encode_file(const char* filename,
180                              const unsigned char* image, unsigned w, unsigned h,
181                              LodePNGColorType colortype, unsigned bitdepth);
182 
183 /*Same as lodepng_encode_file, but always encodes from 32-bit RGBA raw image.*/
184 unsigned lodepng_encode32_file(const char* filename,
185                                const unsigned char* image, unsigned w, unsigned h);
186 
187 /*Same as lodepng_encode_file, but always encodes from 24-bit RGB raw image.*/
188 unsigned lodepng_encode24_file(const char* filename,
189                                const unsigned char* image, unsigned w, unsigned h);
190 #endif /*LODEPNG_COMPILE_DISK*/
191 #endif /*LODEPNG_COMPILE_ENCODER*/
192 
193 
194 #ifdef LODEPNG_COMPILE_CPP
195 namespace lodepng
196 {
197 #ifdef LODEPNG_COMPILE_DECODER
198 /*Same as lodepng_decode_memory, but decodes to an std::vector.*/
199 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
200                 const unsigned char* in, size_t insize,
201                 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
202 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
203                 const std::vector<unsigned char>& in,
204                 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
205 #ifdef LODEPNG_COMPILE_DISK
206 /*
207 Converts PNG file from disk to raw pixel data in memory.
208 Same as the other decode functions, but instead takes a filename as input.
209 */
210 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
211                 const std::string& filename,
212                 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
213 #endif //LODEPNG_COMPILE_DISK
214 #endif //LODEPNG_COMPILE_DECODER
215 
216 #ifdef LODEPNG_COMPILE_ENCODER
217 /*Same as lodepng_encode_memory, but encodes to an std::vector.*/
218 unsigned encode(std::vector<unsigned char>& out,
219                 const unsigned char* in, unsigned w, unsigned h,
220                 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
221 unsigned encode(std::vector<unsigned char>& out,
222                 const std::vector<unsigned char>& in, unsigned w, unsigned h,
223                 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
224 #ifdef LODEPNG_COMPILE_DISK
225 /*
226 Converts 32-bit RGBA raw pixel data into a PNG file on disk.
227 Same as the other encode functions, but instead takes a filename as output.
228 NOTE: This overwrites existing files without warning!
229 */
230 unsigned encode(const std::string& filename,
231                 const unsigned char* in, unsigned w, unsigned h,
232                 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
233 unsigned encode(const std::string& filename,
234                 const std::vector<unsigned char>& in, unsigned w, unsigned h,
235                 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
236 #endif //LODEPNG_COMPILE_DISK
237 #endif //LODEPNG_COMPILE_ENCODER
238 } //namespace lodepng
239 #endif /*LODEPNG_COMPILE_CPP*/
240 #endif /*LODEPNG_COMPILE_PNG*/
241 
242 #ifdef LODEPNG_COMPILE_ERROR_TEXT
243 /*Returns an English description of the numerical error code.*/
244 const char* lodepng_error_text(unsigned code);
245 #endif /*LODEPNG_COMPILE_ERROR_TEXT*/
246 
247 #ifdef LODEPNG_COMPILE_DECODER
248 /*Settings for zlib decompression*/
249 typedef struct LodePNGDecompressSettings LodePNGDecompressSettings;
250 struct LodePNGDecompressSettings
251 {
252   unsigned ignore_adler32; /*if 1, continue and don't give an error message if the Adler32 checksum is corrupted*/
253 
254   /*use custom zlib decoder instead of built in one (default: null)*/
255   unsigned (*custom_zlib)(unsigned char**, size_t*,
256                           const unsigned char*, size_t,
257                           const LodePNGDecompressSettings*);
258   /*use custom deflate decoder instead of built in one (default: null)
259   if custom_zlib is used, custom_deflate is ignored since only the built in
260   zlib function will call custom_deflate*/
261   unsigned (*custom_inflate)(unsigned char**, size_t*,
262                              const unsigned char*, size_t,
263                              const LodePNGDecompressSettings*);
264 
265   const void* custom_context; /*optional custom settings for custom functions*/
266 };
267 
268 extern const LodePNGDecompressSettings lodepng_default_decompress_settings;
269 void lodepng_decompress_settings_init(LodePNGDecompressSettings* settings);
270 #endif /*LODEPNG_COMPILE_DECODER*/
271 
272 #ifdef LODEPNG_COMPILE_ENCODER
273 /*
274 Settings for zlib compression. Tweaking these settings tweaks the balance
275 between speed and compression ratio.
276 */
277 typedef struct LodePNGCompressSettings LodePNGCompressSettings;
278 struct LodePNGCompressSettings /*deflate = compress*/
279 {
280   /*LZ77 related settings*/
281   unsigned btype; /*the block type for LZ (0, 1, 2 or 3, see zlib standard). Should be 2 for proper compression.*/
282   unsigned use_lz77; /*whether or not to use LZ77. Should be 1 for proper compression.*/
283   unsigned windowsize; /*must be a power of two <= 32768. higher compresses more but is slower. Typical value: 2048.*/
284   unsigned minmatch; /*mininum lz77 length. 3 is normally best, 6 can be better for some PNGs. Default: 0*/
285   unsigned nicematch; /*stop searching if >= this length found. Set to 258 for best compression. Default: 128*/
286   unsigned lazymatching; /*use lazy matching: better compression but a bit slower. Default: true*/
287 
288   /*use custom zlib encoder instead of built in one (default: null)*/
289   unsigned (*custom_zlib)(unsigned char**, size_t*,
290                           const unsigned char*, size_t,
291                           const LodePNGCompressSettings*);
292   /*use custom deflate encoder instead of built in one (default: null)
293   if custom_zlib is used, custom_deflate is ignored since only the built in
294   zlib function will call custom_deflate*/
295   unsigned (*custom_deflate)(unsigned char**, size_t*,
296                              const unsigned char*, size_t,
297                              const LodePNGCompressSettings*);
298 
299   const void* custom_context; /*optional custom settings for custom functions*/
300 };
301 
302 extern const LodePNGCompressSettings lodepng_default_compress_settings;
303 void lodepng_compress_settings_init(LodePNGCompressSettings* settings);
304 #endif /*LODEPNG_COMPILE_ENCODER*/
305 
306 #ifdef LODEPNG_COMPILE_PNG
307 /*
308 Color mode of an image. Contains all information required to decode the pixel
309 bits to RGBA colors. This information is the same as used in the PNG file
310 format, and is used both for PNG and raw image data in LodePNG.
311 */
312 typedef struct LodePNGColorMode
313 {
314   /*header (IHDR)*/
315   LodePNGColorType colortype; /*color type, see PNG standard or documentation further in this header file*/
316   unsigned bitdepth;  /*bits per sample, see PNG standard or documentation further in this header file*/
317 
318   /*
319   palette (PLTE and tRNS)
320 
321   Dynamically allocated with the colors of the palette, including alpha.
322   When encoding a PNG, to store your colors in the palette of the LodePNGColorMode, first use
323   lodepng_palette_clear, then for each color use lodepng_palette_add.
324   If you encode an image without alpha with palette, don't forget to put value 255 in each A byte of the palette.
325 
326   When decoding, by default you can ignore this palette, since LodePNG already
327   fills the palette colors in the pixels of the raw RGBA output.
328 
329   The palette is only supported for color type 3.
330   */
331   unsigned char* palette; /*palette in RGBARGBA... order. When allocated, must be either 0, or have size 1024*/
332   size_t palettesize; /*palette size in number of colors (amount of bytes is 4 * palettesize)*/
333 
334   /*
335   transparent color key (tRNS)
336 
337   This color uses the same bit depth as the bitdepth value in this struct, which can be 1-bit to 16-bit.
338   For greyscale PNGs, r, g and b will all 3 be set to the same.
339 
340   When decoding, by default you can ignore this information, since LodePNG sets
341   pixels with this key to transparent already in the raw RGBA output.
342 
343   The color key is only supported for color types 0 and 2.
344   */
345   unsigned key_defined; /*is a transparent color key given? 0 = false, 1 = true*/
346   unsigned key_r;       /*red/greyscale component of color key*/
347   unsigned key_g;       /*green component of color key*/
348   unsigned key_b;       /*blue component of color key*/
349 } LodePNGColorMode;
350 
351 /*init, cleanup and copy functions to use with this struct*/
352 void lodepng_color_mode_init(LodePNGColorMode* info);
353 void lodepng_color_mode_cleanup(LodePNGColorMode* info);
354 /*return value is error code (0 means no error)*/
355 unsigned lodepng_color_mode_copy(LodePNGColorMode* dest, const LodePNGColorMode* source);
356 
357 void lodepng_palette_clear(LodePNGColorMode* info);
358 /*add 1 color to the palette*/
359 unsigned lodepng_palette_add(LodePNGColorMode* info,
360                              unsigned char r, unsigned char g, unsigned char b, unsigned char a);
361 
362 /*get the total amount of bits per pixel, based on colortype and bitdepth in the struct*/
363 unsigned lodepng_get_bpp(const LodePNGColorMode* info);
364 /*get the amount of color channels used, based on colortype in the struct.
365 If a palette is used, it counts as 1 channel.*/
366 unsigned lodepng_get_channels(const LodePNGColorMode* info);
367 /*is it a greyscale type? (only colortype 0 or 4)*/
368 unsigned lodepng_is_greyscale_type(const LodePNGColorMode* info);
369 /*has it got an alpha channel? (only colortype 2 or 6)*/
370 unsigned lodepng_is_alpha_type(const LodePNGColorMode* info);
371 /*has it got a palette? (only colortype 3)*/
372 unsigned lodepng_is_palette_type(const LodePNGColorMode* info);
373 /*only returns true if there is a palette and there is a value in the palette with alpha < 255.
374 Loops through the palette to check this.*/
375 unsigned lodepng_has_palette_alpha(const LodePNGColorMode* info);
376 /*
377 Check if the given color info indicates the possibility of having non-opaque pixels in the PNG image.
378 Returns true if the image can have translucent or invisible pixels (it still be opaque if it doesn't use such pixels).
379 Returns false if the image can only have opaque pixels.
380 In detail, it returns true only if it's a color type with alpha, or has a palette with non-opaque values,
381 or if "key_defined" is true.
382 */
383 unsigned lodepng_can_have_alpha(const LodePNGColorMode* info);
384 /*Returns the byte size of a raw image buffer with given width, height and color mode*/
385 size_t lodepng_get_raw_size(unsigned w, unsigned h, const LodePNGColorMode* color);
386 
387 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
388 /*The information of a Time chunk in PNG.*/
389 typedef struct LodePNGTime
390 {
391   unsigned year;    /*2 bytes used (0-65535)*/
392   unsigned month;   /*1-12*/
393   unsigned day;     /*1-31*/
394   unsigned hour;    /*0-23*/
395   unsigned minute;  /*0-59*/
396   unsigned second;  /*0-60 (to allow for leap seconds)*/
397 } LodePNGTime;
398 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
399 
400 /*Information about the PNG image, except pixels, width and height.*/
401 typedef struct LodePNGInfo
402 {
403   /*header (IHDR), palette (PLTE) and transparency (tRNS) chunks*/
404   unsigned compression_method;/*compression method of the original file. Always 0.*/
405   unsigned filter_method;     /*filter method of the original file*/
406   unsigned interlace_method;  /*interlace method of the original file*/
407   LodePNGColorMode color;     /*color type and bits, palette and transparency of the PNG file*/
408 
409 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
410   /*
411   suggested background color chunk (bKGD)
412   This color uses the same color mode as the PNG (except alpha channel), which can be 1-bit to 16-bit.
413 
414   For greyscale PNGs, r, g and b will all 3 be set to the same. When encoding
415   the encoder writes the red one. For palette PNGs: When decoding, the RGB value
416   will be stored, not a palette index. But when encoding, specify the index of
417   the palette in background_r, the other two are then ignored.
418 
419   The decoder does not use this background color to edit the color of pixels.
420   */
421   unsigned background_defined; /*is a suggested background color given?*/
422   unsigned background_r;       /*red component of suggested background color*/
423   unsigned background_g;       /*green component of suggested background color*/
424   unsigned background_b;       /*blue component of suggested background color*/
425 
426   /*
427   non-international text chunks (tEXt and zTXt)
428 
429   The char** arrays each contain num strings. The actual messages are in
430   text_strings, while text_keys are keywords that give a short description what
431   the actual text represents, e.g. Title, Author, Description, or anything else.
432 
433   A keyword is minimum 1 character and maximum 79 characters long. It's
434   discouraged to use a single line length longer than 79 characters for texts.
435 
436   Don't allocate these text buffers yourself. Use the init/cleanup functions
437   correctly and use lodepng_add_text and lodepng_clear_text.
438   */
439   size_t text_num; /*the amount of texts in these char** buffers (there may be more texts in itext)*/
440   char** text_keys; /*the keyword of a text chunk (e.g. "Comment")*/
441   char** text_strings; /*the actual text*/
442 
443   /*
444   international text chunks (iTXt)
445   Similar to the non-international text chunks, but with additional strings
446   "langtags" and "transkeys".
447   */
448   size_t itext_num; /*the amount of international texts in this PNG*/
449   char** itext_keys; /*the English keyword of the text chunk (e.g. "Comment")*/
450   char** itext_langtags; /*language tag for this text's language, ISO/IEC 646 string, e.g. ISO 639 language tag*/
451   char** itext_transkeys; /*keyword translated to the international language - UTF-8 string*/
452   char** itext_strings; /*the actual international text - UTF-8 string*/
453 
454   /*time chunk (tIME)*/
455   unsigned time_defined; /*set to 1 to make the encoder generate a tIME chunk*/
456   LodePNGTime time;
457 
458   /*phys chunk (pHYs)*/
459   unsigned phys_defined; /*if 0, there is no pHYs chunk and the values below are undefined, if 1 else there is one*/
460   unsigned phys_x; /*pixels per unit in x direction*/
461   unsigned phys_y; /*pixels per unit in y direction*/
462   unsigned phys_unit; /*may be 0 (unknown unit) or 1 (metre)*/
463 
464   /*
465   unknown chunks
466   There are 3 buffers, one for each position in the PNG where unknown chunks can appear
467   each buffer contains all unknown chunks for that position consecutively
468   The 3 buffers are the unknown chunks between certain critical chunks:
469   0: IHDR-PLTE, 1: PLTE-IDAT, 2: IDAT-IEND
470   Do not allocate or traverse this data yourself. Use the chunk traversing functions declared
471   later, such as lodepng_chunk_next and lodepng_chunk_append, to read/write this struct.
472   */
473   unsigned char* unknown_chunks_data[3];
474   size_t unknown_chunks_size[3]; /*size in bytes of the unknown chunks, given for protection*/
475 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
476 } LodePNGInfo;
477 
478 /*init, cleanup and copy functions to use with this struct*/
479 void lodepng_info_init(LodePNGInfo* info);
480 void lodepng_info_cleanup(LodePNGInfo* info);
481 /*return value is error code (0 means no error)*/
482 unsigned lodepng_info_copy(LodePNGInfo* dest, const LodePNGInfo* source);
483 
484 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
485 void lodepng_clear_text(LodePNGInfo* info); /*use this to clear the texts again after you filled them in*/
486 unsigned lodepng_add_text(LodePNGInfo* info, const char* key, const char* str); /*push back both texts at once*/
487 
488 void lodepng_clear_itext(LodePNGInfo* info); /*use this to clear the itexts again after you filled them in*/
489 unsigned lodepng_add_itext(LodePNGInfo* info, const char* key, const char* langtag,
490                            const char* transkey, const char* str); /*push back the 4 texts of 1 chunk at once*/
491 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
492 
493 /*
494 Converts raw buffer from one color type to another color type, based on
495 LodePNGColorMode structs to describe the input and output color type.
496 See the reference manual at the end of this header file to see which color conversions are supported.
497 return value = LodePNG error code (0 if all went ok, an error if the conversion isn't supported)
498 The out buffer must have size (w * h * bpp + 7) / 8, where bpp is the bits per pixel
499 of the output color type (lodepng_get_bpp)
500 The fix_png value works as described in struct LodePNGDecoderSettings.
501 Note: for 16-bit per channel colors, uses big endian format like PNG does.
502 */
503 unsigned lodepng_convert(unsigned char* out, const unsigned char* in,
504                          LodePNGColorMode* mode_out, const LodePNGColorMode* mode_in,
505                          unsigned w, unsigned h, unsigned fix_png);
506 
507 #ifdef LODEPNG_COMPILE_DECODER
508 /*
509 Settings for the decoder. This contains settings for the PNG and the Zlib
510 decoder, but not the Info settings from the Info structs.
511 */
512 typedef struct LodePNGDecoderSettings
513 {
514   LodePNGDecompressSettings zlibsettings; /*in here is the setting to ignore Adler32 checksums*/
515 
516   unsigned ignore_crc; /*ignore CRC checksums*/
517   /*
518   The fix_png setting, if 1, makes the decoder tolerant towards some PNG images
519   that do not correctly follow the PNG specification. This only supports errors
520   that are fixable, were found in images that are actually used on the web, and
521   are silently tolerated by other decoders as well. Currently only one such fix
522   is implemented: if a palette index is out of bounds given the palette size,
523   interpret it as opaque black.
524   By default this value is 0, which makes it stop with an error on such images.
525   */
526   unsigned fix_png;
527   unsigned color_convert; /*whether to convert the PNG to the color type you want. Default: yes*/
528 
529 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
530   unsigned read_text_chunks; /*if false but remember_unknown_chunks is true, they're stored in the unknown chunks*/
531   /*store all bytes from unknown chunks in the LodePNGInfo (off by default, useful for a png editor)*/
532   unsigned remember_unknown_chunks;
533 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
534 } LodePNGDecoderSettings;
535 
536 void lodepng_decoder_settings_init(LodePNGDecoderSettings* settings);
537 #endif /*LODEPNG_COMPILE_DECODER*/
538 
539 #ifdef LODEPNG_COMPILE_ENCODER
540 /*automatically use color type with less bits per pixel if losslessly possible. Default: AUTO*/
541 typedef enum LodePNGFilterStrategy
542 {
543   /*every filter at zero*/
544   LFS_ZERO,
545   /*Use filter that gives minumum sum, as described in the official PNG filter heuristic.*/
546   LFS_MINSUM,
547   /*Use the filter type that gives smallest Shannon entropy for this scanline. Depending
548   on the image, this is better or worse than minsum.*/
549   LFS_ENTROPY,
550   /*
551   Brute-force-search PNG filters by compressing each filter for each scanline.
552   Experimental, very slow, and only rarely gives better compression than MINSUM.
553   */
554   LFS_BRUTE_FORCE,
555   /*use predefined_filters buffer: you specify the filter type for each scanline*/
556   LFS_PREDEFINED
557 } LodePNGFilterStrategy;
558 
559 /*automatically use color type with less bits per pixel if losslessly possible. Default: LAC_AUTO*/
560 typedef enum LodePNGAutoConvert
561 {
562   LAC_NO, /*use color type user requested*/
563   LAC_ALPHA, /*use color type user requested, but if only opaque pixels and RGBA or grey+alpha, use RGB or grey*/
564   LAC_AUTO, /*use PNG color type that can losslessly represent the uncompressed image the smallest possible*/
565   /*
566   like AUTO, but do not choose 1, 2 or 4 bit per pixel types.
567   sometimes a PNG image compresses worse if less than 8 bits per pixels.
568   */
569   LAC_AUTO_NO_NIBBLES,
570   /*
571   like AUTO, but never choose palette color type. For small images, encoding
572   the palette may take more bytes than what is gained. Note that AUTO also
573   already prevents encoding the palette for extremely small images, but that may
574   not be sufficient because due to the compression it cannot predict when to
575   switch.
576   */
577   LAC_AUTO_NO_PALETTE,
578   LAC_AUTO_NO_NIBBLES_NO_PALETTE
579 } LodePNGAutoConvert;
580 
581 
582 /*
583 Automatically chooses color type that gives smallest amount of bits in the
584 output image, e.g. grey if there are only greyscale pixels, palette if there
585 are less than 256 colors, ...
586 The auto_convert parameter allows limiting it to not use palette, ...
587 */
588 unsigned lodepng_auto_choose_color(LodePNGColorMode* mode_out,
589                                    const unsigned char* image, unsigned w, unsigned h,
590                                    const LodePNGColorMode* mode_in,
591                                    LodePNGAutoConvert auto_convert);
592 
593 /*Settings for the encoder.*/
594 typedef struct LodePNGEncoderSettings
595 {
596   LodePNGCompressSettings zlibsettings; /*settings for the zlib encoder, such as window size, ...*/
597 
598   LodePNGAutoConvert auto_convert; /*how to automatically choose output PNG color type, if at all*/
599 
600   /*If true, follows the official PNG heuristic: if the PNG uses a palette or lower than
601   8 bit depth, set all filters to zero. Otherwise use the filter_strategy. Note that to
602   completely follow the official PNG heuristic, filter_palette_zero must be true and
603   filter_strategy must be LFS_MINSUM*/
604   unsigned filter_palette_zero;
605   /*Which filter strategy to use when not using zeroes due to filter_palette_zero.
606   Set filter_palette_zero to 0 to ensure always using your chosen strategy. Default: LFS_MINSUM*/
607   LodePNGFilterStrategy filter_strategy;
608   /*used if filter_strategy is LFS_PREDEFINED. In that case, this must point to a buffer with
609   the same length as the amount of scanlines in the image, and each value must <= 5. You
610   have to cleanup this buffer, LodePNG will never free it. Don't forget that filter_palette_zero
611   must be set to 0 to ensure this is also used on palette or low bitdepth images.*/
612   const unsigned char* predefined_filters;
613 
614   /*force creating a PLTE chunk if colortype is 2 or 6 (= a suggested palette).
615   If colortype is 3, PLTE is _always_ created.*/
616   unsigned force_palette;
617 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
618   /*add LodePNG identifier and version as a text chunk, for debugging*/
619   unsigned add_id;
620   /*encode text chunks as zTXt chunks instead of tEXt chunks, and use compression in iTXt chunks*/
621   unsigned text_compression;
622 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
623 } LodePNGEncoderSettings;
624 
625 void lodepng_encoder_settings_init(LodePNGEncoderSettings* settings);
626 #endif /*LODEPNG_COMPILE_ENCODER*/
627 
628 
629 #if defined(LODEPNG_COMPILE_DECODER) || defined(LODEPNG_COMPILE_ENCODER)
630 /*The settings, state and information for extended encoding and decoding.*/
631 typedef struct LodePNGState
632 {
633 #ifdef LODEPNG_COMPILE_DECODER
634   LodePNGDecoderSettings decoder; /*the decoding settings*/
635 #endif /*LODEPNG_COMPILE_DECODER*/
636 #ifdef LODEPNG_COMPILE_ENCODER
637   LodePNGEncoderSettings encoder; /*the encoding settings*/
638 #endif /*LODEPNG_COMPILE_ENCODER*/
639   LodePNGColorMode info_raw; /*specifies the format in which you would like to get the raw pixel buffer*/
640   LodePNGInfo info_png; /*info of the PNG image obtained after decoding*/
641   unsigned error;
642 #ifdef LODEPNG_COMPILE_CPP
643   //For the lodepng::State subclass.
~LodePNGStateLodePNGState644   virtual ~LodePNGState(){}
645 #endif
646 } LodePNGState;
647 
648 /*init, cleanup and copy functions to use with this struct*/
649 void lodepng_state_init(LodePNGState* state);
650 void lodepng_state_cleanup(LodePNGState* state);
651 void lodepng_state_copy(LodePNGState* dest, const LodePNGState* source);
652 #endif /* defined(LODEPNG_COMPILE_DECODER) || defined(LODEPNG_COMPILE_ENCODER) */
653 
654 #ifdef LODEPNG_COMPILE_DECODER
655 /*
656 Same as lodepng_decode_memory, but uses a LodePNGState to allow custom settings and
657 getting much more information about the PNG image and color mode.
658 */
659 unsigned lodepng_decode(unsigned char** out, unsigned* w, unsigned* h,
660                         LodePNGState* state,
661                         const unsigned char* in, size_t insize);
662 
663 /*
664 Read the PNG header, but not the actual data. This returns only the information
665 that is in the header chunk of the PNG, such as width, height and color type. The
666 information is placed in the info_png field of the LodePNGState.
667 */
668 unsigned lodepng_inspect(unsigned* w, unsigned* h,
669                          LodePNGState* state,
670                          const unsigned char* in, size_t insize);
671 #endif /*LODEPNG_COMPILE_DECODER*/
672 
673 
674 #ifdef LODEPNG_COMPILE_ENCODER
675 /*This function allocates the out buffer with standard malloc and stores the size in *outsize.*/
676 unsigned lodepng_encode(unsigned char** out, size_t* outsize,
677                         const unsigned char* image, unsigned w, unsigned h,
678                         LodePNGState* state);
679 #endif /*LODEPNG_COMPILE_ENCODER*/
680 
681 /*
682 The lodepng_chunk functions are normally not needed, except to traverse the
683 unknown chunks stored in the LodePNGInfo struct, or add new ones to it.
684 It also allows traversing the chunks of an encoded PNG file yourself.
685 
686 PNG standard chunk naming conventions:
687 First byte: uppercase = critical, lowercase = ancillary
688 Second byte: uppercase = public, lowercase = private
689 Third byte: must be uppercase
690 Fourth byte: uppercase = unsafe to copy, lowercase = safe to copy
691 */
692 
693 /*get the length of the data of the chunk. Total chunk length has 12 bytes more.*/
694 unsigned lodepng_chunk_length(const unsigned char* chunk);
695 
696 /*puts the 4-byte type in null terminated string*/
697 void lodepng_chunk_type(char type[5], const unsigned char* chunk);
698 
699 /*check if the type is the given type*/
700 unsigned char lodepng_chunk_type_equals(const unsigned char* chunk, const char* type);
701 
702 /*0: it's one of the critical chunk types, 1: it's an ancillary chunk (see PNG standard)*/
703 unsigned char lodepng_chunk_ancillary(const unsigned char* chunk);
704 
705 /*0: public, 1: private (see PNG standard)*/
706 unsigned char lodepng_chunk_private(const unsigned char* chunk);
707 
708 /*0: the chunk is unsafe to copy, 1: the chunk is safe to copy (see PNG standard)*/
709 unsigned char lodepng_chunk_safetocopy(const unsigned char* chunk);
710 
711 /*get pointer to the data of the chunk, where the input points to the header of the chunk*/
712 unsigned char* lodepng_chunk_data(unsigned char* chunk);
713 const unsigned char* lodepng_chunk_data_const(const unsigned char* chunk);
714 
715 /*returns 0 if the crc is correct, 1 if it's incorrect (0 for OK as usual!)*/
716 unsigned lodepng_chunk_check_crc(const unsigned char* chunk);
717 
718 /*generates the correct CRC from the data and puts it in the last 4 bytes of the chunk*/
719 void lodepng_chunk_generate_crc(unsigned char* chunk);
720 
721 /*iterate to next chunks. don't use on IEND chunk, as there is no next chunk then*/
722 unsigned char* lodepng_chunk_next(unsigned char* chunk);
723 const unsigned char* lodepng_chunk_next_const(const unsigned char* chunk);
724 
725 /*
726 Appends chunk to the data in out. The given chunk should already have its chunk header.
727 The out variable and outlength are updated to reflect the new reallocated buffer.
728 Returns error code (0 if it went ok)
729 */
730 unsigned lodepng_chunk_append(unsigned char** out, size_t* outlength, const unsigned char* chunk);
731 
732 /*
733 Appends new chunk to out. The chunk to append is given by giving its length, type
734 and data separately. The type is a 4-letter string.
735 The out variable and outlength are updated to reflect the new reallocated buffer.
736 Returne error code (0 if it went ok)
737 */
738 unsigned lodepng_chunk_create(unsigned char** out, size_t* outlength, unsigned length,
739                               const char* type, const unsigned char* data);
740 
741 
742 /*Calculate CRC32 of buffer*/
743 unsigned lodepng_crc32(const unsigned char* buf, size_t len);
744 #endif /*LODEPNG_COMPILE_PNG*/
745 
746 
747 #ifdef LODEPNG_COMPILE_ZLIB
748 /*
749 This zlib part can be used independently to zlib compress and decompress a
750 buffer. It cannot be used to create gzip files however, and it only supports the
751 part of zlib that is required for PNG, it does not support dictionaries.
752 */
753 
754 #ifdef LODEPNG_COMPILE_DECODER
755 /*Inflate a buffer. Inflate is the decompression step of deflate. Out buffer must be freed after use.*/
756 unsigned lodepng_inflate(unsigned char** out, size_t* outsize,
757                          const unsigned char* in, size_t insize,
758                          const LodePNGDecompressSettings* settings);
759 
760 /*
761 Decompresses Zlib data. Reallocates the out buffer and appends the data. The
762 data must be according to the zlib specification.
763 Either, *out must be NULL and *outsize must be 0, or, *out must be a valid
764 buffer and *outsize its size in bytes. out must be freed by user after usage.
765 */
766 unsigned lodepng_zlib_decompress(unsigned char** out, size_t* outsize,
767                                  const unsigned char* in, size_t insize,
768                                  const LodePNGDecompressSettings* settings);
769 #endif /*LODEPNG_COMPILE_DECODER*/
770 
771 #ifdef LODEPNG_COMPILE_ENCODER
772 /*
773 Compresses data with Zlib. Reallocates the out buffer and appends the data.
774 Zlib adds a small header and trailer around the deflate data.
775 The data is output in the format of the zlib specification.
776 Either, *out must be NULL and *outsize must be 0, or, *out must be a valid
777 buffer and *outsize its size in bytes. out must be freed by user after usage.
778 */
779 unsigned lodepng_zlib_compress(unsigned char** out, size_t* outsize,
780                                const unsigned char* in, size_t insize,
781                                const LodePNGCompressSettings* settings);
782 
783 /*
784 Find length-limited Huffman code for given frequencies. This function is in the
785 public interface only for tests, it's used internally by lodepng_deflate.
786 */
787 unsigned lodepng_huffman_code_lengths(unsigned* lengths, const unsigned* frequencies,
788                                       size_t numcodes, unsigned maxbitlen);
789 
790 /*Compress a buffer with deflate. See RFC 1951. Out buffer must be freed after use.*/
791 unsigned lodepng_deflate(unsigned char** out, size_t* outsize,
792                          const unsigned char* in, size_t insize,
793                          const LodePNGCompressSettings* settings);
794 
795 #endif /*LODEPNG_COMPILE_ENCODER*/
796 #endif /*LODEPNG_COMPILE_ZLIB*/
797 
798 #ifdef LODEPNG_COMPILE_DISK
799 /*
800 Load a file from disk into buffer. The function allocates the out buffer, and
801 after usage you should free it.
802 out: output parameter, contains pointer to loaded buffer.
803 outsize: output parameter, size of the allocated out buffer
804 filename: the path to the file to load
805 return value: error code (0 means ok)
806 */
807 unsigned lodepng_load_file(unsigned char** out, size_t* outsize, const char* filename);
808 
809 /*
810 Save a file from buffer to disk. Warning, if it exists, this function overwrites
811 the file without warning!
812 buffer: the buffer to write
813 buffersize: size of the buffer to write
814 filename: the path to the file to save to
815 return value: error code (0 means ok)
816 */
817 unsigned lodepng_save_file(const unsigned char* buffer, size_t buffersize, const char* filename);
818 #endif /*LODEPNG_COMPILE_DISK*/
819 
820 #ifdef LODEPNG_COMPILE_CPP
821 //The LodePNG C++ wrapper uses std::vectors instead of manually allocated memory buffers.
822 namespace lodepng
823 {
824 #ifdef LODEPNG_COMPILE_PNG
825 class State : public LodePNGState
826 {
827   public:
828     State();
829     State(const State& other);
830     virtual ~State();
831     State& operator=(const State& other);
832 };
833 
834 #ifdef LODEPNG_COMPILE_DECODER
835 //Same as other lodepng::decode, but using a State for more settings and information.
836 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
837                 State& state,
838                 const unsigned char* in, size_t insize);
839 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
840                 State& state,
841                 const std::vector<unsigned char>& in);
842 #endif /*LODEPNG_COMPILE_DECODER*/
843 
844 #ifdef LODEPNG_COMPILE_ENCODER
845 //Same as other lodepng::encode, but using a State for more settings and information.
846 unsigned encode(std::vector<unsigned char>& out,
847                 const unsigned char* in, unsigned w, unsigned h,
848                 State& state);
849 unsigned encode(std::vector<unsigned char>& out,
850                 const std::vector<unsigned char>& in, unsigned w, unsigned h,
851                 State& state);
852 #endif /*LODEPNG_COMPILE_ENCODER*/
853 
854 #ifdef LODEPNG_COMPILE_DISK
855 /*
856 Load a file from disk into an std::vector. If the vector is empty, then either
857 the file doesn't exist or is an empty file.
858 */
859 void load_file(std::vector<unsigned char>& buffer, const std::string& filename);
860 
861 /*
862 Save the binary data in an std::vector to a file on disk. The file is overwritten
863 without warning.
864 */
865 void save_file(const std::vector<unsigned char>& buffer, const std::string& filename);
866 #endif //LODEPNG_COMPILE_DISK
867 #endif //LODEPNG_COMPILE_PNG
868 
869 #ifdef LODEPNG_COMPILE_ZLIB
870 #ifdef LODEPNG_COMPILE_DECODER
871 //Zlib-decompress an unsigned char buffer
872 unsigned decompress(std::vector<unsigned char>& out, const unsigned char* in, size_t insize,
873                     const LodePNGDecompressSettings& settings = lodepng_default_decompress_settings);
874 
875 //Zlib-decompress an std::vector
876 unsigned decompress(std::vector<unsigned char>& out, const std::vector<unsigned char>& in,
877                     const LodePNGDecompressSettings& settings = lodepng_default_decompress_settings);
878 #endif //LODEPNG_COMPILE_DECODER
879 
880 #ifdef LODEPNG_COMPILE_ENCODER
881 //Zlib-compress an unsigned char buffer
882 unsigned compress(std::vector<unsigned char>& out, const unsigned char* in, size_t insize,
883                   const LodePNGCompressSettings& settings = lodepng_default_compress_settings);
884 
885 //Zlib-compress an std::vector
886 unsigned compress(std::vector<unsigned char>& out, const std::vector<unsigned char>& in,
887                   const LodePNGCompressSettings& settings = lodepng_default_compress_settings);
888 #endif //LODEPNG_COMPILE_ENCODER
889 #endif //LODEPNG_COMPILE_ZLIB
890 } //namespace lodepng
891 #endif /*LODEPNG_COMPILE_CPP*/
892 
893 /*
894 TODO:
895 [.] test if there are no memory leaks or security exploits - done a lot but needs to be checked often
896 [.] check compatibility with vareous compilers  - done but needs to be redone for every newer version
897 [X] converting color to 16-bit per channel types
898 [ ] read all public PNG chunk types (but never let the color profile and gamma ones touch RGB values)
899 [ ] make sure encoder generates no chunks with size > (2^31)-1
900 [ ] partial decoding (stream processing)
901 [X] let the "isFullyOpaque" function check color keys and transparent palettes too
902 [X] better name for the variables "codes", "codesD", "codelengthcodes", "clcl" and "lldl"
903 [ ] don't stop decoding on errors like 69, 57, 58 (make warnings)
904 [ ] make option to choose if the raw image with non multiple of 8 bits per scanline should have padding bits or not
905 [ ] let the C++ wrapper catch exceptions coming from the standard library and return LodePNG error codes
906 */
907 
908 #endif /*LODEPNG_H inclusion guard*/
909 
910 /*
911 LodePNG Documentation
912 ---------------------
913 
914 0. table of contents
915 --------------------
916 
917   1. about
918    1.1. supported features
919    1.2. features not supported
920   2. C and C++ version
921   3. security
922   4. decoding
923   5. encoding
924   6. color conversions
925     6.1. PNG color types
926     6.2. color conversions
927     6.3. padding bits
928     6.4. A note about 16-bits per channel and endianness
929   7. error values
930   8. chunks and PNG editing
931   9. compiler support
932   10. examples
933    10.1. decoder C++ example
934    10.2. decoder C example
935   11. changes
936   12. contact information
937 
938 
939 1. about
940 --------
941 
942 PNG is a file format to store raster images losslessly with good compression,
943 supporting different color types and alpha channel.
944 
945 LodePNG is a PNG codec according to the Portable Network Graphics (PNG)
946 Specification (Second Edition) - W3C Recommendation 10 November 2003.
947 
948 The specifications used are:
949 
950 *) Portable Network Graphics (PNG) Specification (Second Edition):
951      http://www.w3.org/TR/2003/REC-PNG-20031110
952 *) RFC 1950 ZLIB Compressed Data Format version 3.3:
953      http://www.gzip.org/zlib/rfc-zlib.html
954 *) RFC 1951 DEFLATE Compressed Data Format Specification ver 1.3:
955      http://www.gzip.org/zlib/rfc-deflate.html
956 
957 The most recent version of LodePNG can currently be found at
958 http://lodev.org/lodepng/
959 
960 LodePNG works both in C (ISO C90) and C++, with a C++ wrapper that adds
961 extra functionality.
962 
963 LodePNG exists out of two files:
964 -lodepng.h: the header file for both C and C++
965 -lodepng.c(pp): give it the name lodepng.c or lodepng.cpp (or .cc) depending on your usage
966 
967 If you want to start using LodePNG right away without reading this doc, get the
968 examples from the LodePNG website to see how to use it in code, or check the
969 smaller examples in chapter 13 here.
970 
971 LodePNG is simple but only supports the basic requirements. To achieve
972 simplicity, the following design choices were made: There are no dependencies
973 on any external library. There are functions to decode and encode a PNG with
974 a single function call, and extended versions of these functions taking a
975 LodePNGState struct allowing to specify or get more information. By default
976 the colors of the raw image are always RGB or RGBA, no matter what color type
977 the PNG file uses. To read and write files, there are simple functions to
978 convert the files to/from buffers in memory.
979 
980 This all makes LodePNG suitable for loading textures in games, demos and small
981 programs, ... It's less suitable for full fledged image editors, loading PNGs
982 over network (it requires all the image data to be available before decoding can
983 begin), life-critical systems, ...
984 
985 1.1. supported features
986 -----------------------
987 
988 The following features are supported by the decoder:
989 
990 *) decoding of PNGs with any color type, bit depth and interlace mode, to a 24- or 32-bit color raw image,
991    or the same color type as the PNG
992 *) encoding of PNGs, from any raw image to 24- or 32-bit color, or the same color type as the raw image
993 *) Adam7 interlace and deinterlace for any color type
994 *) loading the image from harddisk or decoding it from a buffer from other sources than harddisk
995 *) support for alpha channels, including RGBA color model, translucent palettes and color keying
996 *) zlib decompression (inflate)
997 *) zlib compression (deflate)
998 *) CRC32 and ADLER32 checksums
999 *) handling of unknown chunks, allowing making a PNG editor that stores custom and unknown chunks.
1000 *) the following chunks are supported (generated/interpreted) by both encoder and decoder:
1001     IHDR: header information
1002     PLTE: color palette
1003     IDAT: pixel data
1004     IEND: the final chunk
1005     tRNS: transparency for palettized images
1006     tEXt: textual information
1007     zTXt: compressed textual information
1008     iTXt: international textual information
1009     bKGD: suggested background color
1010     pHYs: physical dimensions
1011     tIME: modification time
1012 
1013 1.2. features not supported
1014 ---------------------------
1015 
1016 The following features are _not_ supported:
1017 
1018 *) some features needed to make a conformant PNG-Editor might be still missing.
1019 *) partial loading/stream processing. All data must be available and is processed in one call.
1020 *) The following public chunks are not supported but treated as unknown chunks by LodePNG
1021     cHRM, gAMA, iCCP, sRGB, sBIT, hIST, sPLT
1022    Some of these are not supported on purpose: LodePNG wants to provide the RGB values
1023    stored in the pixels, not values modified by system dependent gamma or color models.
1024 
1025 
1026 2. C and C++ version
1027 --------------------
1028 
1029 The C version uses buffers allocated with alloc that you need to free()
1030 yourself. You need to use init and cleanup functions for each struct whenever
1031 using a struct from the C version to avoid exploits and memory leaks.
1032 
1033 The C++ version has extra functions with std::vectors in the interface and the
1034 lodepng::State class which is a LodePNGState with constructor and destructor.
1035 
1036 These files work without modification for both C and C++ compilers because all
1037 the additional C++ code is in "#ifdef __cplusplus" blocks that make C-compilers
1038 ignore it, and the C code is made to compile both with strict ISO C90 and C++.
1039 
1040 To use the C++ version, you need to rename the source file to lodepng.cpp
1041 (instead of lodepng.c), and compile it with a C++ compiler.
1042 
1043 To use the C version, you need to rename the source file to lodepng.c (instead
1044 of lodepng.cpp), and compile it with a C compiler.
1045 
1046 
1047 3. Security
1048 -----------
1049 
1050 Even if carefully designed, it's always possible that LodePNG contains possible
1051 exploits. If you discover one, please let me know, and it will be fixed.
1052 
1053 When using LodePNG, care has to be taken with the C version of LodePNG, as well
1054 as the C-style structs when working with C++. The following conventions are used
1055 for all C-style structs:
1056 
1057 -if a struct has a corresponding init function, always call the init function when making a new one
1058 -if a struct has a corresponding cleanup function, call it before the struct disappears to avoid memory leaks
1059 -if a struct has a corresponding copy function, use the copy function instead of "=".
1060  The destination must also be inited already.
1061 
1062 
1063 4. Decoding
1064 -----------
1065 
1066 Decoding converts a PNG compressed image to a raw pixel buffer.
1067 
1068 Most documentation on using the decoder is at its declarations in the header
1069 above. For C, simple decoding can be done with functions such as
1070 lodepng_decode32, and more advanced decoding can be done with the struct
1071 LodePNGState and lodepng_decode. For C++, all decoding can be done with the
1072 various lodepng::decode functions, and lodepng::State can be used for advanced
1073 features.
1074 
1075 When using the LodePNGState, it uses the following fields for decoding:
1076 *) LodePNGInfo info_png: it stores extra information about the PNG (the input) in here
1077 *) LodePNGColorMode info_raw: here you can say what color mode of the raw image (the output) you want to get
1078 *) LodePNGDecoderSettings decoder: you can specify a few extra settings for the decoder to use
1079 
1080 LodePNGInfo info_png
1081 --------------------
1082 
1083 After decoding, this contains extra information of the PNG image, except the actual
1084 pixels, width and height because these are already gotten directly from the decoder
1085 functions.
1086 
1087 It contains for example the original color type of the PNG image, text comments,
1088 suggested background color, etc... More details about the LodePNGInfo struct are
1089 at its declaration documentation.
1090 
1091 LodePNGColorMode info_raw
1092 -------------------------
1093 
1094 When decoding, here you can specify which color type you want
1095 the resulting raw image to be. If this is different from the colortype of the
1096 PNG, then the decoder will automatically convert the result. This conversion
1097 always works, except if you want it to convert a color PNG to greyscale or to
1098 a palette with missing colors.
1099 
1100 By default, 32-bit color is used for the result.
1101 
1102 LodePNGDecoderSettings decoder
1103 ------------------------------
1104 
1105 The settings can be used to ignore the errors created by invalid CRC and Adler32
1106 chunks, and to disable the decoding of tEXt chunks.
1107 
1108 There's also a setting color_convert, true by default. If false, no conversion
1109 is done, the resulting data will be as it was in the PNG (after decompression)
1110 and you'll have to puzzle the colors of the pixels together yourself using the
1111 color type information in the LodePNGInfo.
1112 
1113 
1114 5. Encoding
1115 -----------
1116 
1117 Encoding converts a raw pixel buffer to a PNG compressed image.
1118 
1119 Most documentation on using the encoder is at its declarations in the header
1120 above. For C, simple encoding can be done with functions such as
1121 lodepng_encode32, and more advanced decoding can be done with the struct
1122 LodePNGState and lodepng_encode. For C++, all encoding can be done with the
1123 various lodepng::encode functions, and lodepng::State can be used for advanced
1124 features.
1125 
1126 Like the decoder, the encoder can also give errors. However it gives less errors
1127 since the encoder input is trusted, the decoder input (a PNG image that could
1128 be forged by anyone) is not trusted.
1129 
1130 When using the LodePNGState, it uses the following fields for encoding:
1131 *) LodePNGInfo info_png: here you specify how you want the PNG (the output) to be.
1132 *) LodePNGColorMode info_raw: here you say what color type of the raw image (the input) has
1133 *) LodePNGEncoderSettings encoder: you can specify a few settings for the encoder to use
1134 
1135 LodePNGInfo info_png
1136 --------------------
1137 
1138 When encoding, you use this the opposite way as when decoding: for encoding,
1139 you fill in the values you want the PNG to have before encoding. By default it's
1140 not needed to specify a color type for the PNG since it's automatically chosen,
1141 but it's possible to choose it yourself given the right settings.
1142 
1143 The encoder will not always exactly match the LodePNGInfo struct you give,
1144 it tries as close as possible. Some things are ignored by the encoder. The
1145 encoder uses, for example, the following settings from it when applicable:
1146 colortype and bitdepth, text chunks, time chunk, the color key, the palette, the
1147 background color, the interlace method, unknown chunks, ...
1148 
1149 When encoding to a PNG with colortype 3, the encoder will generate a PLTE chunk.
1150 If the palette contains any colors for which the alpha channel is not 255 (so
1151 there are translucent colors in the palette), it'll add a tRNS chunk.
1152 
1153 LodePNGColorMode info_raw
1154 -------------------------
1155 
1156 You specify the color type of the raw image that you give to the input here,
1157 including a possible transparent color key and palette you happen to be using in
1158 your raw image data.
1159 
1160 By default, 32-bit color is assumed, meaning your input has to be in RGBA
1161 format with 4 bytes (unsigned chars) per pixel.
1162 
1163 LodePNGEncoderSettings encoder
1164 ------------------------------
1165 
1166 The following settings are supported (some are in sub-structs):
1167 *) auto_convert: when this option is enabled, the encoder will
1168 automatically choose the smallest possible color mode (including color key) that
1169 can encode the colors of all pixels without information loss.
1170 *) btype: the block type for LZ77. 0 = uncompressed, 1 = fixed huffman tree,
1171    2 = dynamic huffman tree (best compression). Should be 2 for proper
1172    compression.
1173 *) use_lz77: whether or not to use LZ77 for compressed block types. Should be
1174    true for proper compression.
1175 *) windowsize: the window size used by the LZ77 encoder (1 - 32768). Has value
1176    2048 by default, but can be set to 32768 for better, but slow, compression.
1177 *) force_palette: if colortype is 2 or 6, you can make the encoder write a PLTE
1178    chunk if force_palette is true. This can used as suggested palette to convert
1179    to by viewers that don't support more than 256 colors (if those still exist)
1180 *) add_id: add text chunk "Encoder: LodePNG <version>" to the image.
1181 *) text_compression: default 1. If 1, it'll store texts as zTXt instead of tEXt chunks.
1182   zTXt chunks use zlib compression on the text. This gives a smaller result on
1183   large texts but a larger result on small texts (such as a single program name).
1184   It's all tEXt or all zTXt though, there's no separate setting per text yet.
1185 
1186 
1187 6. color conversions
1188 --------------------
1189 
1190 An important thing to note about LodePNG, is that the color type of the PNG, and
1191 the color type of the raw image, are completely independent. By default, when
1192 you decode a PNG, you get the result as a raw image in the color type you want,
1193 no matter whether the PNG was encoded with a palette, greyscale or RGBA color.
1194 And if you encode an image, by default LodePNG will automatically choose the PNG
1195 color type that gives good compression based on the values of colors and amount
1196 of colors in the image. It can be configured to let you control it instead as
1197 well, though.
1198 
1199 To be able to do this, LodePNG does conversions from one color mode to another.
1200 It can convert from almost any color type to any other color type, except the
1201 following conversions: RGB to greyscale is not supported, and converting to a
1202 palette when the palette doesn't have a required color is not supported. This is
1203 not supported on purpose: this is information loss which requires a color
1204 reduction algorithm that is beyong the scope of a PNG encoder (yes, RGB to grey
1205 is easy, but there are multiple ways if you want to give some channels more
1206 weight).
1207 
1208 By default, when decoding, you get the raw image in 32-bit RGBA or 24-bit RGB
1209 color, no matter what color type the PNG has. And by default when encoding,
1210 LodePNG automatically picks the best color model for the output PNG, and expects
1211 the input image to be 32-bit RGBA or 24-bit RGB. So, unless you want to control
1212 the color format of the images yourself, you can skip this chapter.
1213 
1214 6.1. PNG color types
1215 --------------------
1216 
1217 A PNG image can have many color types, ranging from 1-bit color to 64-bit color,
1218 as well as palettized color modes. After the zlib decompression and unfiltering
1219 in the PNG image is done, the raw pixel data will have that color type and thus
1220 a certain amount of bits per pixel. If you want the output raw image after
1221 decoding to have another color type, a conversion is done by LodePNG.
1222 
1223 The PNG specification gives the following color types:
1224 
1225 0: greyscale, bit depths 1, 2, 4, 8, 16
1226 2: RGB, bit depths 8 and 16
1227 3: palette, bit depths 1, 2, 4 and 8
1228 4: greyscale with alpha, bit depths 8 and 16
1229 6: RGBA, bit depths 8 and 16
1230 
1231 Bit depth is the amount of bits per pixel per color channel. So the total amount
1232 of bits per pixel is: amount of channels * bitdepth.
1233 
1234 6.2. color conversions
1235 ----------------------
1236 
1237 As explained in the sections about the encoder and decoder, you can specify
1238 color types and bit depths in info_png and info_raw to change the default
1239 behaviour.
1240 
1241 If, when decoding, you want the raw image to be something else than the default,
1242 you need to set the color type and bit depth you want in the LodePNGColorMode,
1243 or the parameters of the simple function of LodePNG you're using.
1244 
1245 If, when encoding, you use another color type than the default in the input
1246 image, you need to specify its color type and bit depth in the LodePNGColorMode
1247 of the raw image, or use the parameters of the simplefunction of LodePNG you're
1248 using.
1249 
1250 If, when encoding, you don't want LodePNG to choose the output PNG color type
1251 but control it yourself, you need to set auto_convert in the encoder settings
1252 to LAC_NONE, and specify the color type you want in the LodePNGInfo of the
1253 encoder.
1254 
1255 If you do any of the above, LodePNG may need to do a color conversion, which
1256 follows the rules below, and may sometimes not be allowed.
1257 
1258 To avoid some confusion:
1259 -the decoder converts from PNG to raw image
1260 -the encoder converts from raw image to PNG
1261 -the colortype and bitdepth in LodePNGColorMode info_raw, are those of the raw image
1262 -the colortype and bitdepth in the color field of LodePNGInfo info_png, are those of the PNG
1263 -when encoding, the color type in LodePNGInfo is ignored if auto_convert
1264  is enabled, it is automatically generated instead
1265 -when decoding, the color type in LodePNGInfo is set by the decoder to that of the original
1266  PNG image, but it can be ignored since the raw image has the color type you requested instead
1267 -if the color type of the LodePNGColorMode and PNG image aren't the same, a conversion
1268  between the color types is done if the color types are supported. If it is not
1269  supported, an error is returned. If the types are the same, no conversion is done.
1270 -even though some conversions aren't supported, LodePNG supports loading PNGs from any
1271  colortype and saving PNGs to any colortype, sometimes it just requires preparing
1272  the raw image correctly before encoding.
1273 -both encoder and decoder use the same color converter.
1274 
1275 Non supported color conversions:
1276 -color to greyscale: no error is thrown, but the result will look ugly because
1277 only the red channel is taken
1278 -anything, to palette when that palette does not have that color in it: in this
1279 case an error is thrown
1280 
1281 Supported color conversions:
1282 -anything to 8-bit RGB, 8-bit RGBA, 16-bit RGB, 16-bit RGBA
1283 -any grey or grey+alpha, to grey or grey+alpha
1284 -anything to a palette, as long as the palette has the requested colors in it
1285 -removing alpha channel
1286 -higher to smaller bitdepth, and vice versa
1287 
1288 If you want no color conversion to be done:
1289 -In the encoder, you can make it save a PNG with any color type by giving the
1290 raw color mode and LodePNGInfo the same color mode, and setting auto_convert to
1291 LAC_NO.
1292 -In the decoder, you can make it store the pixel data in the same color type
1293 as the PNG has, by setting the color_convert setting to false. Settings in
1294 info_raw are then ignored.
1295 
1296 The function lodepng_convert does the color conversion. It is available in the
1297 interface but normally isn't needed since the encoder and decoder already call
1298 it.
1299 
1300 6.3. padding bits
1301 -----------------
1302 
1303 In the PNG file format, if a less than 8-bit per pixel color type is used and the scanlines
1304 have a bit amount that isn't a multiple of 8, then padding bits are used so that each
1305 scanline starts at a fresh byte. But that is NOT true for the LodePNG raw input and output.
1306 The raw input image you give to the encoder, and the raw output image you get from the decoder
1307 will NOT have these padding bits, e.g. in the case of a 1-bit image with a width
1308 of 7 pixels, the first pixel of the second scanline will the the 8th bit of the first byte,
1309 not the first bit of a new byte.
1310 
1311 6.4. A note about 16-bits per channel and endianness
1312 ----------------------------------------------------
1313 
1314 LodePNG uses unsigned char arrays for 16-bit per channel colors too, just like
1315 for any other color format. The 16-bit values are stored in big endian (most
1316 significant byte first) in these arrays. This is the opposite order of the
1317 little endian used by x86 CPU's.
1318 
1319 LodePNG always uses big endian because the PNG file format does so internally.
1320 Conversions to other formats than PNG uses internally are not supported by
1321 LodePNG on purpose, there are myriads of formats, including endianness of 16-bit
1322 colors, the order in which you store R, G, B and A, and so on. Supporting and
1323 converting to/from all that is outside the scope of LodePNG.
1324 
1325 This may mean that, depending on your use case, you may want to convert the big
1326 endian output of LodePNG to little endian with a for loop. This is certainly not
1327 always needed, many applications and libraries support big endian 16-bit colors
1328 anyway, but it means you cannot simply cast the unsigned char* buffer to an
1329 unsigned short* buffer on x86 CPUs.
1330 
1331 
1332 7. error values
1333 ---------------
1334 
1335 All functions in LodePNG that return an error code, return 0 if everything went
1336 OK, or a non-zero code if there was an error.
1337 
1338 The meaning of the LodePNG error values can be retrieved with the function
1339 lodepng_error_text: given the numerical error code, it returns a description
1340 of the error in English as a string.
1341 
1342 Check the implementation of lodepng_error_text to see the meaning of each code.
1343 
1344 
1345 8. chunks and PNG editing
1346 -------------------------
1347 
1348 If you want to add extra chunks to a PNG you encode, or use LodePNG for a PNG
1349 editor that should follow the rules about handling of unknown chunks, or if your
1350 program is able to read other types of chunks than the ones handled by LodePNG,
1351 then that's possible with the chunk functions of LodePNG.
1352 
1353 A PNG chunk has the following layout:
1354 
1355 4 bytes length
1356 4 bytes type name
1357 length bytes data
1358 4 bytes CRC
1359 
1360 8.1. iterating through chunks
1361 -----------------------------
1362 
1363 If you have a buffer containing the PNG image data, then the first chunk (the
1364 IHDR chunk) starts at byte number 8 of that buffer. The first 8 bytes are the
1365 signature of the PNG and are not part of a chunk. But if you start at byte 8
1366 then you have a chunk, and can check the following things of it.
1367 
1368 NOTE: none of these functions check for memory buffer boundaries. To avoid
1369 exploits, always make sure the buffer contains all the data of the chunks.
1370 When using lodepng_chunk_next, make sure the returned value is within the
1371 allocated memory.
1372 
1373 unsigned lodepng_chunk_length(const unsigned char* chunk):
1374 
1375 Get the length of the chunk's data. The total chunk length is this length + 12.
1376 
1377 void lodepng_chunk_type(char type[5], const unsigned char* chunk):
1378 unsigned char lodepng_chunk_type_equals(const unsigned char* chunk, const char* type):
1379 
1380 Get the type of the chunk or compare if it's a certain type
1381 
1382 unsigned char lodepng_chunk_critical(const unsigned char* chunk):
1383 unsigned char lodepng_chunk_private(const unsigned char* chunk):
1384 unsigned char lodepng_chunk_safetocopy(const unsigned char* chunk):
1385 
1386 Check if the chunk is critical in the PNG standard (only IHDR, PLTE, IDAT and IEND are).
1387 Check if the chunk is private (public chunks are part of the standard, private ones not).
1388 Check if the chunk is safe to copy. If it's not, then, when modifying data in a critical
1389 chunk, unsafe to copy chunks of the old image may NOT be saved in the new one if your
1390 program doesn't handle that type of unknown chunk.
1391 
1392 unsigned char* lodepng_chunk_data(unsigned char* chunk):
1393 const unsigned char* lodepng_chunk_data_const(const unsigned char* chunk):
1394 
1395 Get a pointer to the start of the data of the chunk.
1396 
1397 unsigned lodepng_chunk_check_crc(const unsigned char* chunk):
1398 void lodepng_chunk_generate_crc(unsigned char* chunk):
1399 
1400 Check if the crc is correct or generate a correct one.
1401 
1402 unsigned char* lodepng_chunk_next(unsigned char* chunk):
1403 const unsigned char* lodepng_chunk_next_const(const unsigned char* chunk):
1404 
1405 Iterate to the next chunk. This works if you have a buffer with consecutive chunks. Note that these
1406 functions do no boundary checking of the allocated data whatsoever, so make sure there is enough
1407 data available in the buffer to be able to go to the next chunk.
1408 
1409 unsigned lodepng_chunk_append(unsigned char** out, size_t* outlength, const unsigned char* chunk):
1410 unsigned lodepng_chunk_create(unsigned char** out, size_t* outlength, unsigned length,
1411                               const char* type, const unsigned char* data):
1412 
1413 These functions are used to create new chunks that are appended to the data in *out that has
1414 length *outlength. The append function appends an existing chunk to the new data. The create
1415 function creates a new chunk with the given parameters and appends it. Type is the 4-letter
1416 name of the chunk.
1417 
1418 8.2. chunks in info_png
1419 -----------------------
1420 
1421 The LodePNGInfo struct contains fields with the unknown chunk in it. It has 3
1422 buffers (each with size) to contain 3 types of unknown chunks:
1423 the ones that come before the PLTE chunk, the ones that come between the PLTE
1424 and the IDAT chunks, and the ones that come after the IDAT chunks.
1425 It's necessary to make the distionction between these 3 cases because the PNG
1426 standard forces to keep the ordering of unknown chunks compared to the critical
1427 chunks, but does not force any other ordering rules.
1428 
1429 info_png.unknown_chunks_data[0] is the chunks before PLTE
1430 info_png.unknown_chunks_data[1] is the chunks after PLTE, before IDAT
1431 info_png.unknown_chunks_data[2] is the chunks after IDAT
1432 
1433 The chunks in these 3 buffers can be iterated through and read by using the same
1434 way described in the previous subchapter.
1435 
1436 When using the decoder to decode a PNG, you can make it store all unknown chunks
1437 if you set the option settings.remember_unknown_chunks to 1. By default, this
1438 option is off (0).
1439 
1440 The encoder will always encode unknown chunks that are stored in the info_png.
1441 If you need it to add a particular chunk that isn't known by LodePNG, you can
1442 use lodepng_chunk_append or lodepng_chunk_create to the chunk data in
1443 info_png.unknown_chunks_data[x].
1444 
1445 Chunks that are known by LodePNG should not be added in that way. E.g. to make
1446 LodePNG add a bKGD chunk, set background_defined to true and add the correct
1447 parameters there instead.
1448 
1449 
1450 9. compiler support
1451 -------------------
1452 
1453 No libraries other than the current standard C library are needed to compile
1454 LodePNG. For the C++ version, only the standard C++ library is needed on top.
1455 Add the files lodepng.c(pp) and lodepng.h to your project, include
1456 lodepng.h where needed, and your program can read/write PNG files.
1457 
1458 If performance is important, use optimization when compiling! For both the
1459 encoder and decoder, this makes a large difference.
1460 
1461 Make sure that LodePNG is compiled with the same compiler of the same version
1462 and with the same settings as the rest of the program, or the interfaces with
1463 std::vectors and std::strings in C++ can be incompatible.
1464 
1465 CHAR_BITS must be 8 or higher, because LodePNG uses unsigned chars for octets.
1466 
1467 *) gcc and g++
1468 
1469 LodePNG is developed in gcc so this compiler is natively supported. It gives no
1470 warnings with compiler options "-Wall -Wextra -pedantic -ansi", with gcc and g++
1471 version 4.7.1 on Linux, 32-bit and 64-bit.
1472 
1473 *) Mingw
1474 
1475 The Mingw compiler (a port of gcc) for Windows is fully supported by LodePNG.
1476 
1477 *) Visual Studio 2005 and up, Visual C++ Express Edition 2005 and up
1478 
1479 Visual Studio may give warnings about 'fopen' being deprecated. A multiplatform library
1480 can't support the proposed Visual Studio alternative however, so LodePNG keeps using
1481 fopen. If you don't want to see the deprecated warnings, put this on top of lodepng.h
1482 before the inclusions:
1483 #define _CRT_SECURE_NO_DEPRECATE
1484 
1485 Other than the above warnings, LodePNG should be warning-free with warning
1486 level 3 (W3). Warning level 4 (W4) will give warnings about integer conversions.
1487 I'm not planning to resolve these warnings. To get rid of them, let Visual
1488 Studio use warning level W3 for lodepng.cpp only: right click lodepng.cpp,
1489 Properties, C/C++, General, Warning Level: Level 3 (/W3).
1490 
1491 Visual Studio may want "stdafx.h" files to be included in each source file and
1492 give an error "unexpected end of file while looking for precompiled header".
1493 That is not standard C++ and will not be added to the stock LodePNG. You can
1494 disable it for lodepng.cpp only by right clicking it, Properties, C/C++,
1495 Precompiled Headers, and set it to Not Using Precompiled Headers there.
1496 
1497 *) Visual Studio 6.0
1498 
1499 LodePNG support for Visual Studio 6.0 is not guaranteed because VS6 doesn't
1500 follow the C++ standard correctly.
1501 
1502 *) Comeau C/C++
1503 
1504 Vesion 20070107 compiles without problems on the Comeau C/C++ Online Test Drive
1505 at http://www.comeaucomputing.com/tryitout in both C90 and C++ mode.
1506 
1507 *) Compilers on Macintosh
1508 
1509 LodePNG has been reported to work both with the gcc and LLVM for Macintosh, both
1510 for C and C++.
1511 
1512 *) Other Compilers
1513 
1514 If you encounter problems on other compilers, feel free to let me know and I may
1515 try to fix it if the compiler is modern standards complient.
1516 
1517 
1518 10. examples
1519 ------------
1520 
1521 This decoder example shows the most basic usage of LodePNG. More complex
1522 examples can be found on the LodePNG website.
1523 
1524 10.1. decoder C++ example
1525 -------------------------
1526 
1527 #include "lodepng.h"
1528 #include <iostream>
1529 
1530 int main(int argc, char *argv[])
1531 {
1532   const char* filename = argc > 1 ? argv[1] : "test.png";
1533 
1534   //load and decode
1535   std::vector<unsigned char> image;
1536   unsigned width, height;
1537   unsigned error = lodepng::decode(image, width, height, filename);
1538 
1539   //if there's an error, display it
1540   if(error) std::cout << "decoder error " << error << ": " << lodepng_error_text(error) << std::endl;
1541 
1542   //the pixels are now in the vector "image", 4 bytes per pixel, ordered RGBARGBA..., use it as texture, draw it, ...
1543 }
1544 
1545 10.2. decoder C example
1546 -----------------------
1547 
1548 #include "lodepng.h"
1549 
1550 int main(int argc, char *argv[])
1551 {
1552   unsigned error;
1553   unsigned char* image;
1554   size_t width, height;
1555   const char* filename = argc > 1 ? argv[1] : "test.png";
1556 
1557   error = lodepng_decode32_file(&image, &width, &height, filename);
1558 
1559   if(error) printf("decoder error %u: %s\n", error, lodepng_error_text(error));
1560 
1561   / * use image here * /
1562 
1563   free(image);
1564   return 0;
1565 }
1566 
1567 
1568 11. changes
1569 -----------
1570 
1571 The version number of LodePNG is the date of the change given in the format
1572 yyyymmdd.
1573 
1574 Some changes aren't backwards compatible. Those are indicated with a (!)
1575 symbol.
1576 
1577 *) 22 dec 2013: Power of two windowsize required for optimization.
1578 *) 15 apr 2013: Fixed bug with LAC_ALPHA and color key.
1579 *) 25 mar 2013: Added an optional feature to ignore some PNG errors (fix_png).
1580 *) 11 mar 2013 (!): Bugfix with custom free. Changed from "my" to "lodepng_"
1581     prefix for the custom allocators and made it possible with a new #define to
1582     use custom ones in your project without needing to change lodepng's code.
1583 *) 28 jan 2013: Bugfix with color key.
1584 *) 27 okt 2012: Tweaks in text chunk keyword length error handling.
1585 *) 8 okt 2012 (!): Added new filter strategy (entropy) and new auto color mode.
1586     (no palette). Better deflate tree encoding. New compression tweak settings.
1587     Faster color conversions while decoding. Some internal cleanups.
1588 *) 23 sep 2012: Reduced warnings in Visual Studio a little bit.
1589 *) 1 sep 2012 (!): Removed #define's for giving custom (de)compression functions
1590     and made it work with function pointers instead.
1591 *) 23 jun 2012: Added more filter strategies. Made it easier to use custom alloc
1592     and free functions and toggle #defines from compiler flags. Small fixes.
1593 *) 6 may 2012 (!): Made plugging in custom zlib/deflate functions more flexible.
1594 *) 22 apr 2012 (!): Made interface more consistent, renaming a lot. Removed
1595     redundant C++ codec classes. Reduced amount of structs. Everything changed,
1596     but it is cleaner now imho and functionality remains the same. Also fixed
1597     several bugs and shrinked the implementation code. Made new samples.
1598 *) 6 nov 2011 (!): By default, the encoder now automatically chooses the best
1599     PNG color model and bit depth, based on the amount and type of colors of the
1600     raw image. For this, autoLeaveOutAlphaChannel replaced by auto_choose_color.
1601 *) 9 okt 2011: simpler hash chain implementation for the encoder.
1602 *) 8 sep 2011: lz77 encoder lazy matching instead of greedy matching.
1603 *) 23 aug 2011: tweaked the zlib compression parameters after benchmarking.
1604     A bug with the PNG filtertype heuristic was fixed, so that it chooses much
1605     better ones (it's quite significant). A setting to do an experimental, slow,
1606     brute force search for PNG filter types is added.
1607 *) 17 aug 2011 (!): changed some C zlib related function names.
1608 *) 16 aug 2011: made the code less wide (max 120 characters per line).
1609 *) 17 apr 2011: code cleanup. Bugfixes. Convert low to 16-bit per sample colors.
1610 *) 21 feb 2011: fixed compiling for C90. Fixed compiling with sections disabled.
1611 *) 11 dec 2010: encoding is made faster, based on suggestion by Peter Eastman
1612     to optimize long sequences of zeros.
1613 *) 13 nov 2010: added LodePNG_InfoColor_hasPaletteAlpha and
1614     LodePNG_InfoColor_canHaveAlpha functions for convenience.
1615 *) 7 nov 2010: added LodePNG_error_text function to get error code description.
1616 *) 30 okt 2010: made decoding slightly faster
1617 *) 26 okt 2010: (!) changed some C function and struct names (more consistent).
1618      Reorganized the documentation and the declaration order in the header.
1619 *) 08 aug 2010: only changed some comments and external samples.
1620 *) 05 jul 2010: fixed bug thanks to warnings in the new gcc version.
1621 *) 14 mar 2010: fixed bug where too much memory was allocated for char buffers.
1622 *) 02 sep 2008: fixed bug where it could create empty tree that linux apps could
1623     read by ignoring the problem but windows apps couldn't.
1624 *) 06 jun 2008: added more error checks for out of memory cases.
1625 *) 26 apr 2008: added a few more checks here and there to ensure more safety.
1626 *) 06 mar 2008: crash with encoding of strings fixed
1627 *) 02 feb 2008: support for international text chunks added (iTXt)
1628 *) 23 jan 2008: small cleanups, and #defines to divide code in sections
1629 *) 20 jan 2008: support for unknown chunks allowing using LodePNG for an editor.
1630 *) 18 jan 2008: support for tIME and pHYs chunks added to encoder and decoder.
1631 *) 17 jan 2008: ability to encode and decode compressed zTXt chunks added
1632     Also vareous fixes, such as in the deflate and the padding bits code.
1633 *) 13 jan 2008: Added ability to encode Adam7-interlaced images. Improved
1634     filtering code of encoder.
1635 *) 07 jan 2008: (!) changed LodePNG to use ISO C90 instead of C++. A
1636     C++ wrapper around this provides an interface almost identical to before.
1637     Having LodePNG be pure ISO C90 makes it more portable. The C and C++ code
1638     are together in these files but it works both for C and C++ compilers.
1639 *) 29 dec 2007: (!) changed most integer types to unsigned int + other tweaks
1640 *) 30 aug 2007: bug fixed which makes this Borland C++ compatible
1641 *) 09 aug 2007: some VS2005 warnings removed again
1642 *) 21 jul 2007: deflate code placed in new namespace separate from zlib code
1643 *) 08 jun 2007: fixed bug with 2- and 4-bit color, and small interlaced images
1644 *) 04 jun 2007: improved support for Visual Studio 2005: crash with accessing
1645     invalid std::vector element [0] fixed, and level 3 and 4 warnings removed
1646 *) 02 jun 2007: made the encoder add a tag with version by default
1647 *) 27 may 2007: zlib and png code separated (but still in the same file),
1648     simple encoder/decoder functions added for more simple usage cases
1649 *) 19 may 2007: minor fixes, some code cleaning, new error added (error 69),
1650     moved some examples from here to lodepng_examples.cpp
1651 *) 12 may 2007: palette decoding bug fixed
1652 *) 24 apr 2007: changed the license from BSD to the zlib license
1653 *) 11 mar 2007: very simple addition: ability to encode bKGD chunks.
1654 *) 04 mar 2007: (!) tEXt chunk related fixes, and support for encoding
1655     palettized PNG images. Plus little interface change with palette and texts.
1656 *) 03 mar 2007: Made it encode dynamic Huffman shorter with repeat codes.
1657     Fixed a bug where the end code of a block had length 0 in the Huffman tree.
1658 *) 26 feb 2007: Huffman compression with dynamic trees (BTYPE 2) now implemented
1659     and supported by the encoder, resulting in smaller PNGs at the output.
1660 *) 27 jan 2007: Made the Adler-32 test faster so that a timewaste is gone.
1661 *) 24 jan 2007: gave encoder an error interface. Added color conversion from any
1662     greyscale type to 8-bit greyscale with or without alpha.
1663 *) 21 jan 2007: (!) Totally changed the interface. It allows more color types
1664     to convert to and is more uniform. See the manual for how it works now.
1665 *) 07 jan 2007: Some cleanup & fixes, and a few changes over the last days:
1666     encode/decode custom tEXt chunks, separate classes for zlib & deflate, and
1667     at last made the decoder give errors for incorrect Adler32 or Crc.
1668 *) 01 jan 2007: Fixed bug with encoding PNGs with less than 8 bits per channel.
1669 *) 29 dec 2006: Added support for encoding images without alpha channel, and
1670     cleaned out code as well as making certain parts faster.
1671 *) 28 dec 2006: Added "Settings" to the encoder.
1672 *) 26 dec 2006: The encoder now does LZ77 encoding and produces much smaller files now.
1673     Removed some code duplication in the decoder. Fixed little bug in an example.
1674 *) 09 dec 2006: (!) Placed output parameters of public functions as first parameter.
1675     Fixed a bug of the decoder with 16-bit per color.
1676 *) 15 okt 2006: Changed documentation structure
1677 *) 09 okt 2006: Encoder class added. It encodes a valid PNG image from the
1678     given image buffer, however for now it's not compressed.
1679 *) 08 sep 2006: (!) Changed to interface with a Decoder class
1680 *) 30 jul 2006: (!) LodePNG_InfoPng , width and height are now retrieved in different
1681     way. Renamed decodePNG to decodePNGGeneric.
1682 *) 29 jul 2006: (!) Changed the interface: image info is now returned as a
1683     struct of type LodePNG::LodePNG_Info, instead of a vector, which was a bit clumsy.
1684 *) 28 jul 2006: Cleaned the code and added new error checks.
1685     Corrected terminology "deflate" into "inflate".
1686 *) 23 jun 2006: Added SDL example in the documentation in the header, this
1687     example allows easy debugging by displaying the PNG and its transparency.
1688 *) 22 jun 2006: (!) Changed way to obtain error value. Added
1689     loadFile function for convenience. Made decodePNG32 faster.
1690 *) 21 jun 2006: (!) Changed type of info vector to unsigned.
1691     Changed position of palette in info vector. Fixed an important bug that
1692     happened on PNGs with an uncompressed block.
1693 *) 16 jun 2006: Internally changed unsigned into unsigned where
1694     needed, and performed some optimizations.
1695 *) 07 jun 2006: (!) Renamed functions to decodePNG and placed them
1696     in LodePNG namespace. Changed the order of the parameters. Rewrote the
1697     documentation in the header. Renamed files to lodepng.cpp and lodepng.h
1698 *) 22 apr 2006: Optimized and improved some code
1699 *) 07 sep 2005: (!) Changed to std::vector interface
1700 *) 12 aug 2005: Initial release (C++, decoder only)
1701 
1702 
1703 12. contact information
1704 -----------------------
1705 
1706 Feel free to contact me with suggestions, problems, comments, ... concerning
1707 LodePNG. If you encounter a PNG image that doesn't work properly with this
1708 decoder, feel free to send it and I'll use it to find and fix the problem.
1709 
1710 My email address is (puzzle the account and domain together with an @ symbol):
1711 Domain: gmail dot com.
1712 Account: lode dot vandevenne.
1713 
1714 
1715 Copyright (c) 2005-2013 Lode Vandevenne
1716 */
1717