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1 /*
2 LodePNG version 20150418
4 Copyright (c) 2005-2015 Lode Vandevenne
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.
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:
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.
19  2. Altered source versions must be plainly marked as such, and must not be
20  misrepresented as being the original software.
22  3. This notice may not be removed or altered from any source
23  distribution.
24 */
27 #ifndef LODEPNG_H
28 #define LODEPNG_H
30 #include <string.h> /*for size_t*/
32 extern const char* LODEPNG_VERSION_STRING;
34 /*
35 The following #defines are used to create code sections. They can be disabled
36 to disable code sections, which can give faster compile time and smaller binary.
37 The "NO_COMPILE" defines are designed to be used to pass as defines to the
38 compiler command to disable them without modifying this header, e.g.
40 */
41 /*deflate & zlib. If disabled, you must specify alternative zlib functions in
42 the custom_zlib field of the compress and decompress settings*/
44 /*png encoder and png decoder*/
46 /*deflate&zlib decoder and png decoder*/
48 /*deflate&zlib encoder and png encoder*/
50 /*the optional built in harddisk file loading and saving functions*/
52 /*support for chunks other than IHDR, IDAT, PLTE, tRNS, IEND: ancillary and unknown chunks*/
54 /*ability to convert error numerical codes to English text string*/
56 /*Compile the default allocators (C's free, malloc and realloc). If you disable this,
57 you can define the functions lodepng_free, lodepng_malloc and lodepng_realloc in your
58 source files with custom allocators.*/
60 /*compile the C++ version (you can disable the C++ wrapper here even when compiling for C++)*/
63 /*The PNG color types (also used for raw).*/
64 typedef enum LodePNGColorType
65 {
66  LCT_GREY = 0, /*greyscale: 1,2,4,8,16 bit*/
67  LCT_RGB = 2, /*RGB: 8,16 bit*/
68  LCT_PALETTE = 3, /*palette: 1,2,4,8 bit*/
69  LCT_GREY_ALPHA = 4, /*greyscale with alpha: 8,16 bit*/
70  LCT_RGBA = 6 /*RGB with alpha: 8,16 bit*/
71 } LodePNGColorType;
74 /*
75 Converts PNG data in memory to raw pixel data.
76 out: Output parameter. Pointer to buffer that will contain the raw pixel data.
77  After decoding, its size is w * h * (bytes per pixel) bytes larger than
78  initially. Bytes per pixel depends on colortype and bitdepth.
79  Must be freed after usage with free(*out).
80  Note: for 16-bit per channel colors, uses big endian format like PNG does.
81 w: Output parameter. Pointer to width of pixel data.
82 h: Output parameter. Pointer to height of pixel data.
83 in: Memory buffer with the PNG file.
84 insize: size of the in buffer.
85 colortype: the desired color type for the raw output image. See explanation on PNG color types.
86 bitdepth: the desired bit depth for the raw output image. See explanation on PNG color types.
87 Return value: LodePNG error code (0 means no error).
88 */
89 unsigned lodepng_decode_memory(unsigned char** out, unsigned* w, unsigned* h,
90  const unsigned char* in, size_t insize,
91  LodePNGColorType colortype, unsigned bitdepth);
93 /*Same as lodepng_decode_memory, but always decodes to 32-bit RGBA raw image*/
94 unsigned lodepng_decode32(unsigned char** out, unsigned* w, unsigned* h,
95  const unsigned char* in, size_t insize);
97 /*Same as lodepng_decode_memory, but always decodes to 24-bit RGB raw image*/
98 unsigned lodepng_decode24(unsigned char** out, unsigned* w, unsigned* h,
99  const unsigned char* in, size_t insize);
102 /*
103 Load PNG from disk, from file with given name.
104 Same as the other decode functions, but instead takes a filename as input.
105 */
106 unsigned lodepng_decode_file(unsigned char** out, unsigned* w, unsigned* h,
107  const char* filename,
108  LodePNGColorType colortype, unsigned bitdepth);
110 /*Same as lodepng_decode_file, but always decodes to 32-bit RGBA raw image.*/
111 unsigned lodepng_decode32_file(unsigned char** out, unsigned* w, unsigned* h,
112  const char* filename);
114 /*Same as lodepng_decode_file, but always decodes to 24-bit RGB raw image.*/
115 unsigned lodepng_decode24_file(unsigned char** out, unsigned* w, unsigned* h,
116  const char* filename);
122 /*
123 Converts raw pixel data into a PNG image in memory. The colortype and bitdepth
124  of the output PNG image cannot be chosen, they are automatically determined
125  by the colortype, bitdepth and content of the input pixel data.
126  Note: for 16-bit per channel colors, needs big endian format like PNG does.
127 out: Output parameter. Pointer to buffer that will contain the PNG image data.
128  Must be freed after usage with free(*out).
129 outsize: Output parameter. Pointer to the size in bytes of the out buffer.
130 image: The raw pixel data to encode. The size of this buffer should be
131  w * h * (bytes per pixel), bytes per pixel depends on colortype and bitdepth.
132 w: width of the raw pixel data in pixels.
133 h: height of the raw pixel data in pixels.
134 colortype: the color type of the raw input image. See explanation on PNG color types.
135 bitdepth: the bit depth of the raw input image. See explanation on PNG color types.
136 Return value: LodePNG error code (0 means no error).
137 */
138 unsigned lodepng_encode_memory(unsigned char** out, size_t* outsize,
139  const unsigned char* image, unsigned w, unsigned h,
140  LodePNGColorType colortype, unsigned bitdepth);
142 /*Same as lodepng_encode_memory, but always encodes from 32-bit RGBA raw image.*/
143 unsigned lodepng_encode32(unsigned char** out, size_t* outsize,
144  const unsigned char* image, unsigned w, unsigned h);
146 /*Same as lodepng_encode_memory, but always encodes from 24-bit RGB raw image.*/
147 unsigned lodepng_encode24(unsigned char** out, size_t* outsize,
148  const unsigned char* image, unsigned w, unsigned h);
151 /*
152 Converts raw pixel data into a PNG file on disk.
153 Same as the other encode functions, but instead takes a filename as output.
154 NOTE: This overwrites existing files without warning!
155 */
156 unsigned lodepng_encode_file(const char* filename,
157  const unsigned char* image, unsigned w, unsigned h,
158  LodePNGColorType colortype, unsigned bitdepth);
160 /*Same as lodepng_encode_file, but always encodes from 32-bit RGBA raw image.*/
161 unsigned lodepng_encode32_file(const char* filename,
162  const unsigned char* image, unsigned w, unsigned h);
164 /*Same as lodepng_encode_file, but always encodes from 24-bit RGB raw image.*/
165 unsigned lodepng_encode24_file(const char* filename,
166  const unsigned char* image, unsigned w, unsigned h);
171 #endif /*LODEPNG_COMPILE_PNG*/
174 /*Returns an English description of the numerical error code.*/
175 const char* lodepng_error_text(unsigned code);
179 /*Settings for zlib decompression*/
180 typedef struct LodePNGDecompressSettings LodePNGDecompressSettings;
181 struct LodePNGDecompressSettings
182 {
183  unsigned ignore_adler32; /*if 1, continue and don't give an error message if the Adler32 checksum is corrupted*/
185  /*use custom zlib decoder instead of built in one (default: null)*/
186  unsigned (*custom_zlib)(unsigned char**, size_t*,
187  const unsigned char*, size_t,
188  const LodePNGDecompressSettings*);
189  /*use custom deflate decoder instead of built in one (default: null)
190  if custom_zlib is used, custom_deflate is ignored since only the built in
191  zlib function will call custom_deflate*/
192  unsigned (*custom_inflate)(unsigned char**, size_t*,
193  const unsigned char*, size_t,
194  const LodePNGDecompressSettings*);
196  const void* custom_context; /*optional custom settings for custom functions*/
197 };
199 extern const LodePNGDecompressSettings lodepng_default_decompress_settings;
200 void lodepng_decompress_settings_init(LodePNGDecompressSettings* settings);
204 /*
205 Settings for zlib compression. Tweaking these settings tweaks the balance
206 between speed and compression ratio.
207 */
208 typedef struct LodePNGCompressSettings LodePNGCompressSettings;
209 struct LodePNGCompressSettings /*deflate = compress*/
210 {
211  /*LZ77 related settings*/
212  unsigned btype; /*the block type for LZ (0, 1, 2 or 3, see zlib standard). Should be 2 for proper compression.*/
213  unsigned use_lz77; /*whether or not to use LZ77. Should be 1 for proper compression.*/
214  unsigned windowsize; /*must be a power of two <= 32768. higher compresses more but is slower. Default value: 2048.*/
215  unsigned minmatch; /*mininum lz77 length. 3 is normally best, 6 can be better for some PNGs. Default: 0*/
216  unsigned nicematch; /*stop searching if >= this length found. Set to 258 for best compression. Default: 128*/
217  unsigned lazymatching; /*use lazy matching: better compression but a bit slower. Default: true*/
219  /*use custom zlib encoder instead of built in one (default: null)*/
220  unsigned (*custom_zlib)(unsigned char**, size_t*,
221  const unsigned char*, size_t,
222  const LodePNGCompressSettings*);
223  /*use custom deflate encoder instead of built in one (default: null)
224  if custom_zlib is used, custom_deflate is ignored since only the built in
225  zlib function will call custom_deflate*/
226  unsigned (*custom_deflate)(unsigned char**, size_t*,
227  const unsigned char*, size_t,
228  const LodePNGCompressSettings*);
230  const void* custom_context; /*optional custom settings for custom functions*/
231 };
233 extern const LodePNGCompressSettings lodepng_default_compress_settings;
234 void lodepng_compress_settings_init(LodePNGCompressSettings* settings);
238 /*
239 Color mode of an image. Contains all information required to decode the pixel
240 bits to RGBA colors. This information is the same as used in the PNG file
241 format, and is used both for PNG and raw image data in LodePNG.
242 */
243 typedef struct LodePNGColorMode
244 {
245  /*header (IHDR)*/
246  LodePNGColorType colortype; /*color type, see PNG standard or documentation further in this header file*/
247  unsigned bitdepth; /*bits per sample, see PNG standard or documentation further in this header file*/
249  /*
250  palette (PLTE and tRNS)
252  Dynamically allocated with the colors of the palette, including alpha.
253  When encoding a PNG, to store your colors in the palette of the LodePNGColorMode, first use
254  lodepng_palette_clear, then for each color use lodepng_palette_add.
255  If you encode an image without alpha with palette, don't forget to put value 255 in each A byte of the palette.
257  When decoding, by default you can ignore this palette, since LodePNG already
258  fills the palette colors in the pixels of the raw RGBA output.
260  The palette is only supported for color type 3.
261  */
262  unsigned char* palette; /*palette in RGBARGBA... order. When allocated, must be either 0, or have size 1024*/
263  size_t palettesize; /*palette size in number of colors (amount of bytes is 4 * palettesize)*/
265  /*
266  transparent color key (tRNS)
268  This color uses the same bit depth as the bitdepth value in this struct, which can be 1-bit to 16-bit.
269  For greyscale PNGs, r, g and b will all 3 be set to the same.
271  When decoding, by default you can ignore this information, since LodePNG sets
272  pixels with this key to transparent already in the raw RGBA output.
274  The color key is only supported for color types 0 and 2.
275  */
276  unsigned key_defined; /*is a transparent color key given? 0 = false, 1 = true*/
277  unsigned key_r; /*red/greyscale component of color key*/
278  unsigned key_g; /*green component of color key*/
279  unsigned key_b; /*blue component of color key*/
280 } LodePNGColorMode;
282 /*init, cleanup and copy functions to use with this struct*/
283 void lodepng_color_mode_init(LodePNGColorMode* info);
284 void lodepng_color_mode_cleanup(LodePNGColorMode* info);
285 /*return value is error code (0 means no error)*/
286 unsigned lodepng_color_mode_copy(LodePNGColorMode* dest, const LodePNGColorMode* source);
288 void lodepng_palette_clear(LodePNGColorMode* info);
289 /*add 1 color to the palette*/
290 unsigned lodepng_palette_add(LodePNGColorMode* info,
291  unsigned char r, unsigned char g, unsigned char b, unsigned char a);
293 /*get the total amount of bits per pixel, based on colortype and bitdepth in the struct*/
294 unsigned lodepng_get_bpp(const LodePNGColorMode* info);
295 /*get the amount of color channels used, based on colortype in the struct.
296 If a palette is used, it counts as 1 channel.*/
297 unsigned lodepng_get_channels(const LodePNGColorMode* info);
298 /*is it a greyscale type? (only colortype 0 or 4)*/
299 unsigned lodepng_is_greyscale_type(const LodePNGColorMode* info);
300 /*has it got an alpha channel? (only colortype 2 or 6)*/
301 unsigned lodepng_is_alpha_type(const LodePNGColorMode* info);
302 /*has it got a palette? (only colortype 3)*/
303 unsigned lodepng_is_palette_type(const LodePNGColorMode* info);
304 /*only returns true if there is a palette and there is a value in the palette with alpha < 255.
305 Loops through the palette to check this.*/
306 unsigned lodepng_has_palette_alpha(const LodePNGColorMode* info);
307 /*
308 Check if the given color info indicates the possibility of having non-opaque pixels in the PNG image.
309 Returns true if the image can have translucent or invisible pixels (it still be opaque if it doesn't use such pixels).
310 Returns false if the image can only have opaque pixels.
311 In detail, it returns true only if it's a color type with alpha, or has a palette with non-opaque values,
312 or if "key_defined" is true.
313 */
314 unsigned lodepng_can_have_alpha(const LodePNGColorMode* info);
315 /*Returns the byte size of a raw image buffer with given width, height and color mode*/
316 size_t lodepng_get_raw_size(unsigned w, unsigned h, const LodePNGColorMode* color);
319 /*The information of a Time chunk in PNG.*/
320 typedef struct LodePNGTime
321 {
322  unsigned year; /*2 bytes used (0-65535)*/
323  unsigned month; /*1-12*/
324  unsigned day; /*1-31*/
325  unsigned hour; /*0-23*/
326  unsigned minute; /*0-59*/
327  unsigned second; /*0-60 (to allow for leap seconds)*/
328 } LodePNGTime;
331 /*Information about the PNG image, except pixels, width and height.*/
332 typedef struct LodePNGInfo
333 {
334  /*header (IHDR), palette (PLTE) and transparency (tRNS) chunks*/
335  unsigned compression_method;/*compression method of the original file. Always 0.*/
336  unsigned filter_method; /*filter method of the original file*/
337  unsigned interlace_method; /*interlace method of the original file*/
338  LodePNGColorMode color; /*color type and bits, palette and transparency of the PNG file*/
341  /*
342  suggested background color chunk (bKGD)
343  This color uses the same color mode as the PNG (except alpha channel), which can be 1-bit to 16-bit.
345  For greyscale PNGs, r, g and b will all 3 be set to the same. When encoding
346  the encoder writes the red one. For palette PNGs: When decoding, the RGB value
347  will be stored, not a palette index. But when encoding, specify the index of
348  the palette in background_r, the other two are then ignored.
350  The decoder does not use this background color to edit the color of pixels.
351  */
352  unsigned background_defined; /*is a suggested background color given?*/
353  unsigned background_r; /*red component of suggested background color*/
354  unsigned background_g; /*green component of suggested background color*/
355  unsigned background_b; /*blue component of suggested background color*/
357  /*
358  non-international text chunks (tEXt and zTXt)
360  The char** arrays each contain num strings. The actual messages are in
361  text_strings, while text_keys are keywords that give a short description what
362  the actual text represents, e.g. Title, Author, Description, or anything else.
364  A keyword is minimum 1 character and maximum 79 characters long. It's
365  discouraged to use a single line length longer than 79 characters for texts.
367  Don't allocate these text buffers yourself. Use the init/cleanup functions
368  correctly and use lodepng_add_text and lodepng_clear_text.
369  */
370  size_t text_num; /*the amount of texts in these char** buffers (there may be more texts in itext)*/
371  char** text_keys; /*the keyword of a text chunk (e.g. "Comment")*/
372  char** text_strings; /*the actual text*/
374  /*
375  international text chunks (iTXt)
376  Similar to the non-international text chunks, but with additional strings
377  "langtags" and "transkeys".
378  */
379  size_t itext_num; /*the amount of international texts in this PNG*/
380  char** itext_keys; /*the English keyword of the text chunk (e.g. "Comment")*/
381  char** itext_langtags; /*language tag for this text's language, ISO/IEC 646 string, e.g. ISO 639 language tag*/
382  char** itext_transkeys; /*keyword translated to the international language - UTF-8 string*/
383  char** itext_strings; /*the actual international text - UTF-8 string*/
385  /*time chunk (tIME)*/
386  unsigned time_defined; /*set to 1 to make the encoder generate a tIME chunk*/
387  LodePNGTime time;
389  /*phys chunk (pHYs)*/
390  unsigned phys_defined; /*if 0, there is no pHYs chunk and the values below are undefined, if 1 else there is one*/
391  unsigned phys_x; /*pixels per unit in x direction*/
392  unsigned phys_y; /*pixels per unit in y direction*/
393  unsigned phys_unit; /*may be 0 (unknown unit) or 1 (metre)*/
395  /*
396  unknown chunks
397  There are 3 buffers, one for each position in the PNG where unknown chunks can appear
398  each buffer contains all unknown chunks for that position consecutively
399  The 3 buffers are the unknown chunks between certain critical chunks:
401  Do not allocate or traverse this data yourself. Use the chunk traversing functions declared
402  later, such as lodepng_chunk_next and lodepng_chunk_append, to read/write this struct.
403  */
404  unsigned char* unknown_chunks_data[3];
405  size_t unknown_chunks_size[3]; /*size in bytes of the unknown chunks, given for protection*/
407 } LodePNGInfo;
409 /*init, cleanup and copy functions to use with this struct*/
410 void lodepng_info_init(LodePNGInfo* info);
411 void lodepng_info_cleanup(LodePNGInfo* info);
412 /*return value is error code (0 means no error)*/
413 unsigned lodepng_info_copy(LodePNGInfo* dest, const LodePNGInfo* source);
416 void lodepng_clear_text(LodePNGInfo* info); /*use this to clear the texts again after you filled them in*/
417 unsigned lodepng_add_text(LodePNGInfo* info, const char* key, const char* str); /*push back both texts at once*/
419 void lodepng_clear_itext(LodePNGInfo* info); /*use this to clear the itexts again after you filled them in*/
420 unsigned lodepng_add_itext(LodePNGInfo* info, const char* key, const char* langtag,
421  const char* transkey, const char* str); /*push back the 4 texts of 1 chunk at once*/
424 /*
425 Converts raw buffer from one color type to another color type, based on
426 LodePNGColorMode structs to describe the input and output color type.
427 See the reference manual at the end of this header file to see which color conversions are supported.
428 return value = LodePNG error code (0 if all went ok, an error if the conversion isn't supported)
429 The out buffer must have size (w * h * bpp + 7) / 8, where bpp is the bits per pixel
430 of the output color type (lodepng_get_bpp).
431 For < 8 bpp images, there should not be padding bits at the end of scanlines.
432 For 16-bit per channel colors, uses big endian format like PNG does.
433 Return value is LodePNG error code
434 */
435 unsigned lodepng_convert(unsigned char* out, const unsigned char* in,
436  LodePNGColorMode* mode_out, const LodePNGColorMode* mode_in,
437  unsigned w, unsigned h);
440 /*
441 Settings for the decoder. This contains settings for the PNG and the Zlib
442 decoder, but not the Info settings from the Info structs.
443 */
444 typedef struct LodePNGDecoderSettings
445 {
446  LodePNGDecompressSettings zlibsettings; /*in here is the setting to ignore Adler32 checksums*/
448  unsigned ignore_crc; /*ignore CRC checksums*/
450  unsigned color_convert; /*whether to convert the PNG to the color type you want. Default: yes*/
453  unsigned read_text_chunks; /*if false but remember_unknown_chunks is true, they're stored in the unknown chunks*/
454  /*store all bytes from unknown chunks in the LodePNGInfo (off by default, useful for a png editor)*/
455  unsigned remember_unknown_chunks;
457 } LodePNGDecoderSettings;
459 void lodepng_decoder_settings_init(LodePNGDecoderSettings* settings);
463 /*automatically use color type with less bits per pixel if losslessly possible. Default: AUTO*/
464 typedef enum LodePNGFilterStrategy
465 {
466  /*every filter at zero*/
467  LFS_ZERO,
468  /*Use filter that gives minumum sum, as described in the official PNG filter heuristic.*/
470  /*Use the filter type that gives smallest Shannon entropy for this scanline. Depending
471  on the image, this is better or worse than minsum.*/
473  /*
474  Brute-force-search PNG filters by compressing each filter for each scanline.
475  Experimental, very slow, and only rarely gives better compression than MINSUM.
476  */
478  /*use predefined_filters buffer: you specify the filter type for each scanline*/
480 } LodePNGFilterStrategy;
482 /*Gives characteristics about the colors of the image, which helps decide which color model to use for encoding.
483 Used internally by default if "auto_convert" is enabled. Public because it's useful for custom algorithms.*/
484 typedef struct LodePNGColorProfile
485 {
486  unsigned colored; /*not greyscale*/
487  unsigned key; /*if true, image is not opaque. Only if true and alpha is false, color key is possible.*/
488  unsigned short key_r; /*these values are always in 16-bit bitdepth in the profile*/
489  unsigned short key_g;
490  unsigned short key_b;
491  unsigned alpha; /*alpha channel or alpha palette required*/
492  unsigned numcolors; /*amount of colors, up to 257. Not valid if bits == 16.*/
493  unsigned char palette[1024]; /*Remembers up to the first 256 RGBA colors, in no particular order*/
494  unsigned bits; /*bits per channel (not for palette). 1,2 or 4 for greyscale only. 16 if 16-bit per channel required.*/
495 } LodePNGColorProfile;
497 void lodepng_color_profile_init(LodePNGColorProfile* profile);
499 /*Get a LodePNGColorProfile of the image.*/
500 unsigned lodepng_get_color_profile(LodePNGColorProfile* profile,
501  const unsigned char* image, unsigned w, unsigned h,
502  const LodePNGColorMode* mode_in);
503 /*The function LodePNG uses internally to decide the PNG color with auto_convert.
504 Chooses an optimal color model, e.g. grey if only grey pixels, palette if < 256 colors, ...*/
505 unsigned lodepng_auto_choose_color(LodePNGColorMode* mode_out,
506  const unsigned char* image, unsigned w, unsigned h,
507  const LodePNGColorMode* mode_in);
509 /*Settings for the encoder.*/
510 typedef struct LodePNGEncoderSettings
511 {
512  LodePNGCompressSettings zlibsettings; /*settings for the zlib encoder, such as window size, ...*/
514  unsigned auto_convert; /*automatically choose output PNG color type. Default: true*/
516  /*If true, follows the official PNG heuristic: if the PNG uses a palette or lower than
517  8 bit depth, set all filters to zero. Otherwise use the filter_strategy. Note that to
518  completely follow the official PNG heuristic, filter_palette_zero must be true and
519  filter_strategy must be LFS_MINSUM*/
520  unsigned filter_palette_zero;
521  /*Which filter strategy to use when not using zeroes due to filter_palette_zero.
522  Set filter_palette_zero to 0 to ensure always using your chosen strategy. Default: LFS_MINSUM*/
523  LodePNGFilterStrategy filter_strategy;
524  /*used if filter_strategy is LFS_PREDEFINED. In that case, this must point to a buffer with
525  the same length as the amount of scanlines in the image, and each value must <= 5. You
526  have to cleanup this buffer, LodePNG will never free it. Don't forget that filter_palette_zero
527  must be set to 0 to ensure this is also used on palette or low bitdepth images.*/
528  const unsigned char* predefined_filters;
530  /*force creating a PLTE chunk if colortype is 2 or 6 (= a suggested palette).
531  If colortype is 3, PLTE is _always_ created.*/
532  unsigned force_palette;
534  /*add LodePNG identifier and version as a text chunk, for debugging*/
535  unsigned add_id;
536  /*encode text chunks as zTXt chunks instead of tEXt chunks, and use compression in iTXt chunks*/
537  unsigned text_compression;
539 } LodePNGEncoderSettings;
541 void lodepng_encoder_settings_init(LodePNGEncoderSettings* settings);
546 /*The settings, state and information for extended encoding and decoding.*/
547 typedef struct LodePNGState
548 {
550  LodePNGDecoderSettings decoder; /*the decoding settings*/
553  LodePNGEncoderSettings encoder; /*the encoding settings*/
555  LodePNGColorMode info_raw; /*specifies the format in which you would like to get the raw pixel buffer*/
556  LodePNGInfo info_png; /*info of the PNG image obtained after decoding*/
557  unsigned error;
558 } LodePNGState;
560 /*init, cleanup and copy functions to use with this struct*/
561 void lodepng_state_init(LodePNGState* state);
562 void lodepng_state_cleanup(LodePNGState* state);
563 void lodepng_state_copy(LodePNGState* dest, const LodePNGState* source);
564 #endif /* defined(LODEPNG_COMPILE_DECODER) || defined(LODEPNG_COMPILE_ENCODER) */
567 /*
568 Same as lodepng_decode_memory, but uses a LodePNGState to allow custom settings and
569 getting much more information about the PNG image and color mode.
570 */
571 unsigned lodepng_decode(unsigned char** out, unsigned* w, unsigned* h,
572  LodePNGState* state,
573  const unsigned char* in, size_t insize);
575 /*
576 Read the PNG header, but not the actual data. This returns only the information
577 that is in the header chunk of the PNG, such as width, height and color type. The
578 information is placed in the info_png field of the LodePNGState.
579 */
580 unsigned lodepng_inspect(unsigned* w, unsigned* h,
581  LodePNGState* state,
582  const unsigned char* in, size_t insize);
587 /*This function allocates the out buffer with standard malloc and stores the size in *outsize.*/
588 unsigned lodepng_encode(unsigned char** out, size_t* outsize,
589  const unsigned char* image, unsigned w, unsigned h,
590  LodePNGState* state);
593 /*
594 The lodepng_chunk functions are normally not needed, except to traverse the
595 unknown chunks stored in the LodePNGInfo struct, or add new ones to it.
596 It also allows traversing the chunks of an encoded PNG file yourself.
598 PNG standard chunk naming conventions:
599 First byte: uppercase = critical, lowercase = ancillary
600 Second byte: uppercase = public, lowercase = private
601 Third byte: must be uppercase
602 Fourth byte: uppercase = unsafe to copy, lowercase = safe to copy
603 */
605 /*
606 Gets the length of the data of the chunk. Total chunk length has 12 bytes more.
607 There must be at least 4 bytes to read from. If the result value is too large,
608 it may be corrupt data.
609 */
610 unsigned lodepng_chunk_length(const unsigned char* chunk);
612 /*puts the 4-byte type in null terminated string*/
613 void lodepng_chunk_type(char type[5], const unsigned char* chunk);
615 /*check if the type is the given type*/
616 unsigned char lodepng_chunk_type_equals(const unsigned char* chunk, const char* type);
618 /*0: it's one of the critical chunk types, 1: it's an ancillary chunk (see PNG standard)*/
619 unsigned char lodepng_chunk_ancillary(const unsigned char* chunk);
621 /*0: public, 1: private (see PNG standard)*/
622 unsigned char lodepng_chunk_private(const unsigned char* chunk);
624 /*0: the chunk is unsafe to copy, 1: the chunk is safe to copy (see PNG standard)*/
625 unsigned char lodepng_chunk_safetocopy(const unsigned char* chunk);
627 /*get pointer to the data of the chunk, where the input points to the header of the chunk*/
628 unsigned char* lodepng_chunk_data(unsigned char* chunk);
629 const unsigned char* lodepng_chunk_data_const(const unsigned char* chunk);
631 /*returns 0 if the crc is correct, 1 if it's incorrect (0 for OK as usual!)*/
632 unsigned lodepng_chunk_check_crc(const unsigned char* chunk);
634 /*generates the correct CRC from the data and puts it in the last 4 bytes of the chunk*/
635 void lodepng_chunk_generate_crc(unsigned char* chunk);
637 /*iterate to next chunks. don't use on IEND chunk, as there is no next chunk then*/
638 unsigned char* lodepng_chunk_next(unsigned char* chunk);
639 const unsigned char* lodepng_chunk_next_const(const unsigned char* chunk);
641 /*
642 Appends chunk to the data in out. The given chunk should already have its chunk header.
643 The out variable and outlength are updated to reflect the new reallocated buffer.
644 Returns error code (0 if it went ok)
645 */
646 unsigned lodepng_chunk_append(unsigned char** out, size_t* outlength, const unsigned char* chunk);
648 /*
649 Appends new chunk to out. The chunk to append is given by giving its length, type
650 and data separately. The type is a 4-letter string.
651 The out variable and outlength are updated to reflect the new reallocated buffer.
652 Returne error code (0 if it went ok)
653 */
654 unsigned lodepng_chunk_create(unsigned char** out, size_t* outlength, unsigned length,
655  const char* type, const unsigned char* data);
658 /*Calculate CRC32 of buffer*/
659 unsigned lodepng_crc32(const unsigned char* buf, size_t len);
660 #endif /*LODEPNG_COMPILE_PNG*/
664 /*
665 This zlib part can be used independently to zlib compress and decompress a
666 buffer. It cannot be used to create gzip files however, and it only supports the
667 part of zlib that is required for PNG, it does not support dictionaries.
668 */
671 /*Inflate a buffer. Inflate is the decompression step of deflate. Out buffer must be freed after use.*/
672 unsigned lodepng_inflate(unsigned char** out, size_t* outsize,
673  const unsigned char* in, size_t insize,
674  const LodePNGDecompressSettings* settings);
676 /*
677 Decompresses Zlib data. Reallocates the out buffer and appends the data. The
678 data must be according to the zlib specification.
679 Either, *out must be NULL and *outsize must be 0, or, *out must be a valid
680 buffer and *outsize its size in bytes. out must be freed by user after usage.
681 */
682 unsigned lodepng_zlib_decompress(unsigned char** out, size_t* outsize,
683  const unsigned char* in, size_t insize,
684  const LodePNGDecompressSettings* settings);
688 /*
689 Compresses data with Zlib. Reallocates the out buffer and appends the data.
690 Zlib adds a small header and trailer around the deflate data.
691 The data is output in the format of the zlib specification.
692 Either, *out must be NULL and *outsize must be 0, or, *out must be a valid
693 buffer and *outsize its size in bytes. out must be freed by user after usage.
694 */
695 unsigned lodepng_zlib_compress(unsigned char** out, size_t* outsize,
696  const unsigned char* in, size_t insize,
697  const LodePNGCompressSettings* settings);
699 /*
700 Find length-limited Huffman code for given frequencies. This function is in the
701 public interface only for tests, it's used internally by lodepng_deflate.
702 */
703 unsigned lodepng_huffman_code_lengths(unsigned* lengths, const unsigned* frequencies,
704  size_t numcodes, unsigned maxbitlen);
706 /*Compress a buffer with deflate. See RFC 1951. Out buffer must be freed after use.*/
707 unsigned lodepng_deflate(unsigned char** out, size_t* outsize,
708  const unsigned char* in, size_t insize,
709  const LodePNGCompressSettings* settings);
715 /*
716 Load a file from disk into buffer. The function allocates the out buffer, and
717 after usage you should free it.
718 out: output parameter, contains pointer to loaded buffer.
719 outsize: output parameter, size of the allocated out buffer
720 filename: the path to the file to load
721 return value: error code (0 means ok)
722 */
723 unsigned lodepng_load_file(unsigned char** out, size_t* outsize, const char* filename);
725 /*
726 Save a file from buffer to disk. Warning, if it exists, this function overwrites
727 the file without warning!
728 buffer: the buffer to write
729 buffersize: size of the buffer to write
730 filename: the path to the file to save to
731 return value: error code (0 means ok)
732 */
733 unsigned lodepng_save_file(const unsigned char* buffer, size_t buffersize, const char* filename);
736 /*
737 TODO:
738 [.] test if there are no memory leaks or security exploits - done a lot but needs to be checked often
739 [.] check compatibility with vareous compilers - done but needs to be redone for every newer version
740 [X] converting color to 16-bit per channel types
741 [ ] read all public PNG chunk types (but never let the color profile and gamma ones touch RGB values)
742 [ ] make sure encoder generates no chunks with size > (2^31)-1
743 [ ] partial decoding (stream processing)
744 [X] let the "isFullyOpaque" function check color keys and transparent palettes too
745 [X] better name for the variables "codes", "codesD", "codelengthcodes", "clcl" and "lldl"
746 [ ] don't stop decoding on errors like 69, 57, 58 (make warnings)
747 [ ] let the C++ wrapper catch exceptions coming from the standard library and return LodePNG error codes
748 [ ] allow user to provide custom color conversion functions, e.g. for premultiplied alpha, padding bits or not, ...
749 */
751 #endif /*LODEPNG_H inclusion guard*/
753 /*
754 LodePNG Documentation
755 ---------------------
757 0. table of contents
758 --------------------
760  1. about
761  1.1. supported features
762  1.2. features not supported
763  2. C and C++ version
764  3. security
765  4. decoding
766  5. encoding
767  6. color conversions
768  6.1. PNG color types
769  6.2. color conversions
770  6.3. padding bits
771  6.4. A note about 16-bits per channel and endianness
772  7. error values
773  8. chunks and PNG editing
774  9. compiler support
775  10. examples
776  10.1. decoder C++ example
777  10.2. decoder C example
778  11. changes
779  12. contact information
782 1. about
783 --------
785 PNG is a file format to store raster images losslessly with good compression,
786 supporting different color types and alpha channel.
788 LodePNG is a PNG codec according to the Portable Network Graphics (PNG)
789 Specification (Second Edition) - W3C Recommendation 10 November 2003.
791 The specifications used are:
793 *) Portable Network Graphics (PNG) Specification (Second Edition):
794  http://www.w3.org/TR/2003/REC-PNG-20031110
795 *) RFC 1950 ZLIB Compressed Data Format version 3.3:
796  http://www.gzip.org/zlib/rfc-zlib.html
797 *) RFC 1951 DEFLATE Compressed Data Format Specification ver 1.3:
798  http://www.gzip.org/zlib/rfc-deflate.html
800 The most recent version of LodePNG can currently be found at
801 http://lodev.org/lodepng/
803 LodePNG works both in C (ISO C90) and C++, with a C++ wrapper that adds
804 extra functionality.
806 LodePNG exists out of two files:
807 -lodepng.h: the header file for both C and C++
808 -lodepng.c(pp): give it the name lodepng.c depending on your usage
810 If you want to start using LodePNG right away without reading this doc, get the
811 examples from the LodePNG website to see how to use it in code, or check the
812 smaller examples in chapter 13 here.
814 LodePNG is simple but only supports the basic requirements. To achieve
815 simplicity, the following design choices were made: There are no dependencies
816 on any external library. There are functions to decode and encode a PNG with
817 a single function call, and extended versions of these functions taking a
818 LodePNGState struct allowing to specify or get more information. By default
819 the colors of the raw image are always RGB or RGBA, no matter what color type
820 the PNG file uses. To read and write files, there are simple functions to
821 convert the files to/from buffers in memory.
823 This all makes LodePNG suitable for loading textures in games, demos and small
824 programs, ... It's less suitable for full fledged image editors, loading PNGs
825 over network (it requires all the image data to be available before decoding can
826 begin), life-critical systems, ...
828 1.1. supported features
829 -----------------------
831 The following features are supported by the decoder:
833 *) decoding of PNGs with any color type, bit depth and interlace mode, to a 24- or 32-bit color raw image,
834  or the same color type as the PNG
835 *) encoding of PNGs, from any raw image to 24- or 32-bit color, or the same color type as the raw image
836 *) Adam7 interlace and deinterlace for any color type
837 *) loading the image from harddisk or decoding it from a buffer from other sources than harddisk
838 *) support for alpha channels, including RGBA color model, translucent palettes and color keying
839 *) zlib decompression (inflate)
840 *) zlib compression (deflate)
841 *) CRC32 and ADLER32 checksums
842 *) handling of unknown chunks, allowing making a PNG editor that stores custom and unknown chunks.
843 *) the following chunks are supported (generated/interpreted) by both encoder and decoder:
844  IHDR: header information
845  PLTE: color palette
846  IDAT: pixel data
847  IEND: the final chunk
848  tRNS: transparency for palettized images
849  tEXt: textual information
850  zTXt: compressed textual information
851  iTXt: international textual information
852  bKGD: suggested background color
853  pHYs: physical dimensions
854  tIME: modification time
856 1.2. features not supported
857 ---------------------------
859 The following features are _not_ supported:
861 *) some features needed to make a conformant PNG-Editor might be still missing.
862 *) partial loading/stream processing. All data must be available and is processed in one call.
863 *) The following public chunks are not supported but treated as unknown chunks by LodePNG
864  cHRM, gAMA, iCCP, sRGB, sBIT, hIST, sPLT
865  Some of these are not supported on purpose: LodePNG wants to provide the RGB values
866  stored in the pixels, not values modified by system dependent gamma or color models.
869 2. C and C++ version
870 --------------------
872 The C version uses buffers allocated with alloc that you need to free()
873 yourself. You need to use init and cleanup functions for each struct whenever
874 using a struct from the C version to avoid exploits and memory leaks.
876 The C++ version has extra functions with std::vectors in the interface and the
877 lodepng::State class which is a LodePNGState with constructor and destructor.
879 These files work without modification for both C and C++ compilers because all
880 the additional C++ code is in "#ifdef __cplusplus" blocks that make C-compilers
881 ignore it, and the C code is made to compile both with strict ISO C90 and C++.
883 To use the C++ version, you need to rename the source file to lodepng.c
884 (instead of lodepng.c), and compile it with a C++ compiler.
886 To use the C version, you need to rename the source file to lodepng.c (instead
887 of lodepng.c), and compile it with a C compiler.
890 3. Security
891 -----------
893 Even if carefully designed, it's always possible that LodePNG contains possible
894 exploits. If you discover one, please let me know, and it will be fixed.
896 When using LodePNG, care has to be taken with the C version of LodePNG, as well
897 as the C-style structs when working with C++. The following conventions are used
898 for all C-style structs:
900 -if a struct has a corresponding init function, always call the init function when making a new one
901 -if a struct has a corresponding cleanup function, call it before the struct disappears to avoid memory leaks
902 -if a struct has a corresponding copy function, use the copy function instead of "=".
903  The destination must also be inited already.
906 4. Decoding
907 -----------
909 Decoding converts a PNG compressed image to a raw pixel buffer.
911 Most documentation on using the decoder is at its declarations in the header
912 above. For C, simple decoding can be done with functions such as
913 lodepng_decode32, and more advanced decoding can be done with the struct
914 LodePNGState and lodepng_decode. For C++, all decoding can be done with the
915 various lodepng::decode functions, and lodepng::State can be used for advanced
916 features.
918 When using the LodePNGState, it uses the following fields for decoding:
919 *) LodePNGInfo info_png: it stores extra information about the PNG (the input) in here
920 *) LodePNGColorMode info_raw: here you can say what color mode of the raw image (the output) you want to get
921 *) LodePNGDecoderSettings decoder: you can specify a few extra settings for the decoder to use
923 LodePNGInfo info_png
924 --------------------
926 After decoding, this contains extra information of the PNG image, except the actual
927 pixels, width and height because these are already gotten directly from the decoder
928 functions.
930 It contains for example the original color type of the PNG image, text comments,
931 suggested background color, etc... More details about the LodePNGInfo struct are
932 at its declaration documentation.
934 LodePNGColorMode info_raw
935 -------------------------
937 When decoding, here you can specify which color type you want
938 the resulting raw image to be. If this is different from the colortype of the
939 PNG, then the decoder will automatically convert the result. This conversion
940 always works, except if you want it to convert a color PNG to greyscale or to
941 a palette with missing colors.
943 By default, 32-bit color is used for the result.
945 LodePNGDecoderSettings decoder
946 ------------------------------
948 The settings can be used to ignore the errors created by invalid CRC and Adler32
949 chunks, and to disable the decoding of tEXt chunks.
951 There's also a setting color_convert, true by default. If false, no conversion
952 is done, the resulting data will be as it was in the PNG (after decompression)
953 and you'll have to puzzle the colors of the pixels together yourself using the
954 color type information in the LodePNGInfo.
957 5. Encoding
958 -----------
960 Encoding converts a raw pixel buffer to a PNG compressed image.
962 Most documentation on using the encoder is at its declarations in the header
963 above. For C, simple encoding can be done with functions such as
964 lodepng_encode32, and more advanced decoding can be done with the struct
965 LodePNGState and lodepng_encode. For C++, all encoding can be done with the
966 various lodepng::encode functions, and lodepng::State can be used for advanced
967 features.
969 Like the decoder, the encoder can also give errors. However it gives less errors
970 since the encoder input is trusted, the decoder input (a PNG image that could
971 be forged by anyone) is not trusted.
973 When using the LodePNGState, it uses the following fields for encoding:
974 *) LodePNGInfo info_png: here you specify how you want the PNG (the output) to be.
975 *) LodePNGColorMode info_raw: here you say what color type of the raw image (the input) has
976 *) LodePNGEncoderSettings encoder: you can specify a few settings for the encoder to use
978 LodePNGInfo info_png
979 --------------------
981 When encoding, you use this the opposite way as when decoding: for encoding,
982 you fill in the values you want the PNG to have before encoding. By default it's
983 not needed to specify a color type for the PNG since it's automatically chosen,
984 but it's possible to choose it yourself given the right settings.
986 The encoder will not always exactly match the LodePNGInfo struct you give,
987 it tries as close as possible. Some things are ignored by the encoder. The
988 encoder uses, for example, the following settings from it when applicable:
989 colortype and bitdepth, text chunks, time chunk, the color key, the palette, the
990 background color, the interlace method, unknown chunks, ...
992 When encoding to a PNG with colortype 3, the encoder will generate a PLTE chunk.
993 If the palette contains any colors for which the alpha channel is not 255 (so
994 there are translucent colors in the palette), it'll add a tRNS chunk.
996 LodePNGColorMode info_raw
997 -------------------------
999 You specify the color type of the raw image that you give to the input here,
1000 including a possible transparent color key and palette you happen to be using in
1001 your raw image data.
1003 By default, 32-bit color is assumed, meaning your input has to be in RGBA
1004 format with 4 bytes (unsigned chars) per pixel.
1006 LodePNGEncoderSettings encoder
1007 ------------------------------
1009 The following settings are supported (some are in sub-structs):
1010 *) auto_convert: when this option is enabled, the encoder will
1011 automatically choose the smallest possible color mode (including color key) that
1012 can encode the colors of all pixels without information loss.
1013 *) btype: the block type for LZ77. 0 = uncompressed, 1 = fixed huffman tree,
1014  2 = dynamic huffman tree (best compression). Should be 2 for proper
1015  compression.
1016 *) use_lz77: whether or not to use LZ77 for compressed block types. Should be
1017  true for proper compression.
1018 *) windowsize: the window size used by the LZ77 encoder (1 - 32768). Has value
1019  2048 by default, but can be set to 32768 for better, but slow, compression.
1020 *) force_palette: if colortype is 2 or 6, you can make the encoder write a PLTE
1021  chunk if force_palette is true. This can used as suggested palette to convert
1022  to by viewers that don't support more than 256 colors (if those still exist)
1023 *) add_id: add text chunk "Encoder: LodePNG <version>" to the image.
1024 *) text_compression: default 1. If 1, it'll store texts as zTXt instead of tEXt chunks.
1025  zTXt chunks use zlib compression on the text. This gives a smaller result on
1026  large texts but a larger result on small texts (such as a single program name).
1027  It's all tEXt or all zTXt though, there's no separate setting per text yet.
1030 6. color conversions
1031 --------------------
1033 An important thing to note about LodePNG, is that the color type of the PNG, and
1034 the color type of the raw image, are completely independent. By default, when
1035 you decode a PNG, you get the result as a raw image in the color type you want,
1036 no matter whether the PNG was encoded with a palette, greyscale or RGBA color.
1037 And if you encode an image, by default LodePNG will automatically choose the PNG
1038 color type that gives good compression based on the values of colors and amount
1039 of colors in the image. It can be configured to let you control it instead as
1040 well, though.
1042 To be able to do this, LodePNG does conversions from one color mode to another.
1043 It can convert from almost any color type to any other color type, except the
1044 following conversions: RGB to greyscale is not supported, and converting to a
1045 palette when the palette doesn't have a required color is not supported. This is
1046 not supported on purpose: this is information loss which requires a color
1047 reduction algorithm that is beyong the scope of a PNG encoder (yes, RGB to grey
1048 is easy, but there are multiple ways if you want to give some channels more
1049 weight).
1051 By default, when decoding, you get the raw image in 32-bit RGBA or 24-bit RGB
1052 color, no matter what color type the PNG has. And by default when encoding,
1053 LodePNG automatically picks the best color model for the output PNG, and expects
1054 the input image to be 32-bit RGBA or 24-bit RGB. So, unless you want to control
1055 the color format of the images yourself, you can skip this chapter.
1057 6.1. PNG color types
1058 --------------------
1060 A PNG image can have many color types, ranging from 1-bit color to 64-bit color,
1061 as well as palettized color modes. After the zlib decompression and unfiltering
1062 in the PNG image is done, the raw pixel data will have that color type and thus
1063 a certain amount of bits per pixel. If you want the output raw image after
1064 decoding to have another color type, a conversion is done by LodePNG.
1066 The PNG specification gives the following color types:
1068 0: greyscale, bit depths 1, 2, 4, 8, 16
1069 2: RGB, bit depths 8 and 16
1070 3: palette, bit depths 1, 2, 4 and 8
1071 4: greyscale with alpha, bit depths 8 and 16
1072 6: RGBA, bit depths 8 and 16
1074 Bit depth is the amount of bits per pixel per color channel. So the total amount
1075 of bits per pixel is: amount of channels * bitdepth.
1077 6.2. color conversions
1078 ----------------------
1080 As explained in the sections about the encoder and decoder, you can specify
1081 color types and bit depths in info_png and info_raw to change the default
1082 behaviour.
1084 If, when decoding, you want the raw image to be something else than the default,
1085 you need to set the color type and bit depth you want in the LodePNGColorMode,
1086 or the parameters colortype and bitdepth of the simple decoding function.
1088 If, when encoding, you use another color type than the default in the raw input
1089 image, you need to specify its color type and bit depth in the LodePNGColorMode
1090 of the raw image, or use the parameters colortype and bitdepth of the simple
1091 encoding function.
1093 If, when encoding, you don't want LodePNG to choose the output PNG color type
1094 but control it yourself, you need to set auto_convert in the encoder settings
1095 to false, and specify the color type you want in the LodePNGInfo of the
1096 encoder (including palette: it can generate a palette if auto_convert is true,
1097 otherwise not).
1099 If the input and output color type differ (whether user chosen or auto chosen),
1100 LodePNG will do a color conversion, which follows the rules below, and may
1101 sometimes result in an error.
1103 To avoid some confusion:
1104 -the decoder converts from PNG to raw image
1105 -the encoder converts from raw image to PNG
1106 -the colortype and bitdepth in LodePNGColorMode info_raw, are those of the raw image
1107 -the colortype and bitdepth in the color field of LodePNGInfo info_png, are those of the PNG
1108 -when encoding, the color type in LodePNGInfo is ignored if auto_convert
1109  is enabled, it is automatically generated instead
1110 -when decoding, the color type in LodePNGInfo is set by the decoder to that of the original
1111  PNG image, but it can be ignored since the raw image has the color type you requested instead
1112 -if the color type of the LodePNGColorMode and PNG image aren't the same, a conversion
1113  between the color types is done if the color types are supported. If it is not
1114  supported, an error is returned. If the types are the same, no conversion is done.
1115 -even though some conversions aren't supported, LodePNG supports loading PNGs from any
1116  colortype and saving PNGs to any colortype, sometimes it just requires preparing
1117  the raw image correctly before encoding.
1118 -both encoder and decoder use the same color converter.
1120 Non supported color conversions:
1121 -color to greyscale: no error is thrown, but the result will look ugly because
1122 only the red channel is taken
1123 -anything to palette when that palette does not have that color in it: in this
1124 case an error is thrown
1126 Supported color conversions:
1127 -anything to 8-bit RGB, 8-bit RGBA, 16-bit RGB, 16-bit RGBA
1128 -any grey or grey+alpha, to grey or grey+alpha
1129 -anything to a palette, as long as the palette has the requested colors in it
1130 -removing alpha channel
1131 -higher to smaller bitdepth, and vice versa
1133 If you want no color conversion to be done (e.g. for speed or control):
1134 -In the encoder, you can make it save a PNG with any color type by giving the
1135 raw color mode and LodePNGInfo the same color mode, and setting auto_convert to
1136 false.
1137 -In the decoder, you can make it store the pixel data in the same color type
1138 as the PNG has, by setting the color_convert setting to false. Settings in
1139 info_raw are then ignored.
1141 The function lodepng_convert does the color conversion. It is available in the
1142 interface but normally isn't needed since the encoder and decoder already call
1143 it.
1145 6.3. padding bits
1146 -----------------
1148 In the PNG file format, if a less than 8-bit per pixel color type is used and the scanlines
1149 have a bit amount that isn't a multiple of 8, then padding bits are used so that each
1150 scanline starts at a fresh byte. But that is NOT true for the LodePNG raw input and output.
1151 The raw input image you give to the encoder, and the raw output image you get from the decoder
1152 will NOT have these padding bits, e.g. in the case of a 1-bit image with a width
1153 of 7 pixels, the first pixel of the second scanline will the the 8th bit of the first byte,
1154 not the first bit of a new byte.
1156 6.4. A note about 16-bits per channel and endianness
1157 ----------------------------------------------------
1159 LodePNG uses unsigned char arrays for 16-bit per channel colors too, just like
1160 for any other color format. The 16-bit values are stored in big endian (most
1161 significant byte first) in these arrays. This is the opposite order of the
1162 little endian used by x86 CPU's.
1164 LodePNG always uses big endian because the PNG file format does so internally.
1165 Conversions to other formats than PNG uses internally are not supported by
1166 LodePNG on purpose, there are myriads of formats, including endianness of 16-bit
1167 colors, the order in which you store R, G, B and A, and so on. Supporting and
1168 converting to/from all that is outside the scope of LodePNG.
1170 This may mean that, depending on your use case, you may want to convert the big
1171 endian output of LodePNG to little endian with a for loop. This is certainly not
1172 always needed, many applications and libraries support big endian 16-bit colors
1173 anyway, but it means you cannot simply cast the unsigned char* buffer to an
1174 unsigned short* buffer on x86 CPUs.
1177 7. error values
1178 ---------------
1180 All functions in LodePNG that return an error code, return 0 if everything went
1181 OK, or a non-zero code if there was an error.
1183 The meaning of the LodePNG error values can be retrieved with the function
1184 lodepng_error_text: given the numerical error code, it returns a description
1185 of the error in English as a string.
1187 Check the implementation of lodepng_error_text to see the meaning of each code.
1190 8. chunks and PNG editing
1191 -------------------------
1193 If you want to add extra chunks to a PNG you encode, or use LodePNG for a PNG
1194 editor that should follow the rules about handling of unknown chunks, or if your
1195 program is able to read other types of chunks than the ones handled by LodePNG,
1196 then that's possible with the chunk functions of LodePNG.
1198 A PNG chunk has the following layout:
1200 4 bytes length
1201 4 bytes type name
1202 length bytes data
1203 4 bytes CRC
1205 8.1. iterating through chunks
1206 -----------------------------
1208 If you have a buffer containing the PNG image data, then the first chunk (the
1209 IHDR chunk) starts at byte number 8 of that buffer. The first 8 bytes are the
1210 signature of the PNG and are not part of a chunk. But if you start at byte 8
1211 then you have a chunk, and can check the following things of it.
1213 NOTE: none of these functions check for memory buffer boundaries. To avoid
1214 exploits, always make sure the buffer contains all the data of the chunks.
1215 When using lodepng_chunk_next, make sure the returned value is within the
1216 allocated memory.
1218 unsigned lodepng_chunk_length(const unsigned char* chunk):
1220 Get the length of the chunk's data. The total chunk length is this length + 12.
1222 void lodepng_chunk_type(char type[5], const unsigned char* chunk):
1223 unsigned char lodepng_chunk_type_equals(const unsigned char* chunk, const char* type):
1225 Get the type of the chunk or compare if it's a certain type
1227 unsigned char lodepng_chunk_critical(const unsigned char* chunk):
1228 unsigned char lodepng_chunk_private(const unsigned char* chunk):
1229 unsigned char lodepng_chunk_safetocopy(const unsigned char* chunk):
1231 Check if the chunk is critical in the PNG standard (only IHDR, PLTE, IDAT and IEND are).
1232 Check if the chunk is private (public chunks are part of the standard, private ones not).
1233 Check if the chunk is safe to copy. If it's not, then, when modifying data in a critical
1234 chunk, unsafe to copy chunks of the old image may NOT be saved in the new one if your
1235 program doesn't handle that type of unknown chunk.
1237 unsigned char* lodepng_chunk_data(unsigned char* chunk):
1238 const unsigned char* lodepng_chunk_data_const(const unsigned char* chunk):
1240 Get a pointer to the start of the data of the chunk.
1242 unsigned lodepng_chunk_check_crc(const unsigned char* chunk):
1243 void lodepng_chunk_generate_crc(unsigned char* chunk):
1245 Check if the crc is correct or generate a correct one.
1247 unsigned char* lodepng_chunk_next(unsigned char* chunk):
1248 const unsigned char* lodepng_chunk_next_const(const unsigned char* chunk):
1250 Iterate to the next chunk. This works if you have a buffer with consecutive chunks. Note that these
1251 functions do no boundary checking of the allocated data whatsoever, so make sure there is enough
1252 data available in the buffer to be able to go to the next chunk.
1254 unsigned lodepng_chunk_append(unsigned char** out, size_t* outlength, const unsigned char* chunk):
1255 unsigned lodepng_chunk_create(unsigned char** out, size_t* outlength, unsigned length,
1256  const char* type, const unsigned char* data):
1258 These functions are used to create new chunks that are appended to the data in *out that has
1259 length *outlength. The append function appends an existing chunk to the new data. The create
1260 function creates a new chunk with the given parameters and appends it. Type is the 4-letter
1261 name of the chunk.
1263 8.2. chunks in info_png
1264 -----------------------
1266 The LodePNGInfo struct contains fields with the unknown chunk in it. It has 3
1267 buffers (each with size) to contain 3 types of unknown chunks:
1268 the ones that come before the PLTE chunk, the ones that come between the PLTE
1269 and the IDAT chunks, and the ones that come after the IDAT chunks.
1270 It's necessary to make the distionction between these 3 cases because the PNG
1271 standard forces to keep the ordering of unknown chunks compared to the critical
1272 chunks, but does not force any other ordering rules.
1274 info_png.unknown_chunks_data[0] is the chunks before PLTE
1275 info_png.unknown_chunks_data[1] is the chunks after PLTE, before IDAT
1276 info_png.unknown_chunks_data[2] is the chunks after IDAT
1278 The chunks in these 3 buffers can be iterated through and read by using the same
1279 way described in the previous subchapter.
1281 When using the decoder to decode a PNG, you can make it store all unknown chunks
1282 if you set the option settings.remember_unknown_chunks to 1. By default, this
1283 option is off (0).
1285 The encoder will always encode unknown chunks that are stored in the info_png.
1286 If you need it to add a particular chunk that isn't known by LodePNG, you can
1287 use lodepng_chunk_append or lodepng_chunk_create to the chunk data in
1288 info_png.unknown_chunks_data[x].
1290 Chunks that are known by LodePNG should not be added in that way. E.g. to make
1291 LodePNG add a bKGD chunk, set background_defined to true and add the correct
1292 parameters there instead.
1295 9. compiler support
1296 -------------------
1298 No libraries other than the current standard C library are needed to compile
1299 LodePNG. For the C++ version, only the standard C++ library is needed on top.
1300 Add the files lodepng.c(pp) and lodepng.h to your project, include
1301 lodepng.h where needed, and your program can read/write PNG files.
1303 It is compatible with C90 and up, and C++03 and up.
1305 If performance is important, use optimization when compiling! For both the
1306 encoder and decoder, this makes a large difference.
1308 Make sure that LodePNG is compiled with the same compiler of the same version
1309 and with the same settings as the rest of the program, or the interfaces with
1310 std::vectors and std::strings in C++ can be incompatible.
1312 CHAR_BITS must be 8 or higher, because LodePNG uses unsigned chars for octets.
1314 *) gcc and g++
1316 LodePNG is developed in gcc so this compiler is natively supported. It gives no
1317 warnings with compiler options "-Wall -Wextra -pedantic -ansi", with gcc and g++
1318 version 4.7.1 on Linux, 32-bit and 64-bit.
1320 *) Clang
1322 Fully supported and warning-free.
1324 *) Mingw
1326 The Mingw compiler (a port of gcc for Windows) should be fully supported by
1327 LodePNG.
1329 *) Visual Studio and Visual C++ Express Edition
1331 LodePNG should be warning-free with warning level W4. Two warnings were disabled
1332 with pragmas though: warning 4244 about implicit conversions, and warning 4996
1333 where it wants to use a non-standard function fopen_s instead of the standard C
1334 fopen.
1336 Visual Studio may want "stdafx.h" files to be included in each source file and
1337 give an error "unexpected end of file while looking for precompiled header".
1338 This is not standard C++ and will not be added to the stock LodePNG. You can
1339 disable it for lodepng.c only by right clicking it, Properties, C/C++,
1340 Precompiled Headers, and set it to Not Using Precompiled Headers there.
1342 NOTE: Modern versions of VS should be fully supported, but old versions, e.g.
1343 VS6, are not guaranteed to work.
1345 *) Compilers on Macintosh
1347 LodePNG has been reported to work both with gcc and LLVM for Macintosh, both for
1348 C and C++.
1350 *) Other Compilers
1352 If you encounter problems on any compilers, feel free to let me know and I may
1353 try to fix it if the compiler is modern and standards complient.
1356 10. examples
1357 ------------
1359 This decoder example shows the most basic usage of LodePNG. More complex
1360 examples can be found on the LodePNG website.
1362 10.1. decoder C++ example
1363 -------------------------
1365 #include "lodepng.h"
1366 #include <iostream>
1368 int main(int argc, char *argv[])
1369 {
1370  const char* filename = argc > 1 ? argv[1] : "test.png";
1372  //load and decode
1373  std::vector<unsigned char> image;
1374  unsigned width, height;
1375  unsigned error = lodepng::decode(image, width, height, filename);
1377  //if there's an error, display it
1378  if(error) std::cout << "decoder error " << error << ": " << lodepng_error_text(error) << std::endl;
1380  //the pixels are now in the vector "image", 4 bytes per pixel, ordered RGBARGBA..., use it as texture, draw it, ...
1381 }
1383 10.2. decoder C example
1384 -----------------------
1386 #include "lodepng.h"
1388 int main(int argc, char *argv[])
1389 {
1390  unsigned error;
1391  unsigned char* image;
1392  size_t width, height;
1393  const char* filename = argc > 1 ? argv[1] : "test.png";
1395  error = lodepng_decode32_file(&image, &width, &height, filename);
1397  if(error) printf("decoder error %u: %s\n", error, lodepng_error_text(error));
1399  / * use image here * /
1401  free(image);
1402  return 0;
1403 }
1406 11. changes
1407 -----------
1409 The version number of LodePNG is the date of the change given in the format
1410 yyyymmdd.
1412 Some changes aren't backwards compatible. Those are indicated with a (!)
1413 symbol.
1415 *) 18 apr 2015: Boundary PM instead of just package-merge for faster encoding.
1416 *) 23 aug 2014: Reduced needless memory usage of decoder.
1417 *) 28 jun 2014: Removed fix_png setting, always support palette OOB for
1418  simplicity. Made ColorProfile public.
1419 *) 09 jun 2014: Faster encoder by fixing hash bug and more zeros optimization.
1420 *) 22 dec 2013: Power of two windowsize required for optimization.
1421 *) 15 apr 2013: Fixed bug with LAC_ALPHA and color key.
1422 *) 25 mar 2013: Added an optional feature to ignore some PNG errors (fix_png).
1423 *) 11 mar 2013 (!): Bugfix with custom free. Changed from "my" to "lodepng_"
1424  prefix for the custom allocators and made it possible with a new #define to
1425  use custom ones in your project without needing to change lodepng's code.
1426 *) 28 jan 2013: Bugfix with color key.
1427 *) 27 okt 2012: Tweaks in text chunk keyword length error handling.
1428 *) 8 okt 2012 (!): Added new filter strategy (entropy) and new auto color mode.
1429  (no palette). Better deflate tree encoding. New compression tweak settings.
1430  Faster color conversions while decoding. Some internal cleanups.
1431 *) 23 sep 2012: Reduced warnings in Visual Studio a little bit.
1432 *) 1 sep 2012 (!): Removed #define's for giving custom (de)compression functions
1433  and made it work with function pointers instead.
1434 *) 23 jun 2012: Added more filter strategies. Made it easier to use custom alloc
1435  and free functions and toggle #defines from compiler flags. Small fixes.
1436 *) 6 may 2012 (!): Made plugging in custom zlib/deflate functions more flexible.
1437 *) 22 apr 2012 (!): Made interface more consistent, renaming a lot. Removed
1438  redundant C++ codec classes. Reduced amount of structs. Everything changed,
1439  but it is cleaner now imho and functionality remains the same. Also fixed
1440  several bugs and shrinked the implementation code. Made new samples.
1441 *) 6 nov 2011 (!): By default, the encoder now automatically chooses the best
1442  PNG color model and bit depth, based on the amount and type of colors of the
1443  raw image. For this, autoLeaveOutAlphaChannel replaced by auto_choose_color.
1444 *) 9 okt 2011: simpler hash chain implementation for the encoder.
1445 *) 8 sep 2011: lz77 encoder lazy matching instead of greedy matching.
1446 *) 23 aug 2011: tweaked the zlib compression parameters after benchmarking.
1447  A bug with the PNG filtertype heuristic was fixed, so that it chooses much
1448  better ones (it's quite significant). A setting to do an experimental, slow,
1449  brute force search for PNG filter types is added.
1450 *) 17 aug 2011 (!): changed some C zlib related function names.
1451 *) 16 aug 2011: made the code less wide (max 120 characters per line).
1452 *) 17 apr 2011: code cleanup. Bugfixes. Convert low to 16-bit per sample colors.
1453 *) 21 feb 2011: fixed compiling for C90. Fixed compiling with sections disabled.
1454 *) 11 dec 2010: encoding is made faster, based on suggestion by Peter Eastman
1455  to optimize long sequences of zeros.
1456 *) 13 nov 2010: added LodePNG_InfoColor_hasPaletteAlpha and
1457  LodePNG_InfoColor_canHaveAlpha functions for convenience.
1458 *) 7 nov 2010: added LodePNG_error_text function to get error code description.
1459 *) 30 okt 2010: made decoding slightly faster
1460 *) 26 okt 2010: (!) changed some C function and struct names (more consistent).
1461  Reorganized the documentation and the declaration order in the header.
1462 *) 08 aug 2010: only changed some comments and external samples.
1463 *) 05 jul 2010: fixed bug thanks to warnings in the new gcc version.
1464 *) 14 mar 2010: fixed bug where too much memory was allocated for char buffers.
1465 *) 02 sep 2008: fixed bug where it could create empty tree that linux apps could
1466  read by ignoring the problem but windows apps couldn't.
1467 *) 06 jun 2008: added more error checks for out of memory cases.
1468 *) 26 apr 2008: added a few more checks here and there to ensure more safety.
1469 *) 06 mar 2008: crash with encoding of strings fixed
1470 *) 02 feb 2008: support for international text chunks added (iTXt)
1471 *) 23 jan 2008: small cleanups, and #defines to divide code in sections
1472 *) 20 jan 2008: support for unknown chunks allowing using LodePNG for an editor.
1473 *) 18 jan 2008: support for tIME and pHYs chunks added to encoder and decoder.
1474 *) 17 jan 2008: ability to encode and decode compressed zTXt chunks added
1475  Also vareous fixes, such as in the deflate and the padding bits code.
1476 *) 13 jan 2008: Added ability to encode Adam7-interlaced images. Improved
1477  filtering code of encoder.
1478 *) 07 jan 2008: (!) changed LodePNG to use ISO C90 instead of C++. A
1479  C++ wrapper around this provides an interface almost identical to before.
1480  Having LodePNG be pure ISO C90 makes it more portable. The C and C++ code
1481  are together in these files but it works both for C and C++ compilers.
1482 *) 29 dec 2007: (!) changed most integer types to unsigned int + other tweaks
1483 *) 30 aug 2007: bug fixed which makes this Borland C++ compatible
1484 *) 09 aug 2007: some VS2005 warnings removed again
1485 *) 21 jul 2007: deflate code placed in new namespace separate from zlib code
1486 *) 08 jun 2007: fixed bug with 2- and 4-bit color, and small interlaced images
1487 *) 04 jun 2007: improved support for Visual Studio 2005: crash with accessing
1488  invalid std::vector element [0] fixed, and level 3 and 4 warnings removed
1489 *) 02 jun 2007: made the encoder add a tag with version by default
1490 *) 27 may 2007: zlib and png code separated (but still in the same file),
1491  simple encoder/decoder functions added for more simple usage cases
1492 *) 19 may 2007: minor fixes, some code cleaning, new error added (error 69),
1493  moved some examples from here to lodepng_examples.c
1494 *) 12 may 2007: palette decoding bug fixed
1495 *) 24 apr 2007: changed the license from BSD to the zlib license
1496 *) 11 mar 2007: very simple addition: ability to encode bKGD chunks.
1497 *) 04 mar 2007: (!) tEXt chunk related fixes, and support for encoding
1498  palettized PNG images. Plus little interface change with palette and texts.
1499 *) 03 mar 2007: Made it encode dynamic Huffman shorter with repeat codes.
1500  Fixed a bug where the end code of a block had length 0 in the Huffman tree.
1501 *) 26 feb 2007: Huffman compression with dynamic trees (BTYPE 2) now implemented
1502  and supported by the encoder, resulting in smaller PNGs at the output.
1503 *) 27 jan 2007: Made the Adler-32 test faster so that a timewaste is gone.
1504 *) 24 jan 2007: gave encoder an error interface. Added color conversion from any
1505  greyscale type to 8-bit greyscale with or without alpha.
1506 *) 21 jan 2007: (!) Totally changed the interface. It allows more color types
1507  to convert to and is more uniform. See the manual for how it works now.
1508 *) 07 jan 2007: Some cleanup & fixes, and a few changes over the last days:
1509  encode/decode custom tEXt chunks, separate classes for zlib & deflate, and
1510  at last made the decoder give errors for incorrect Adler32 or Crc.
1511 *) 01 jan 2007: Fixed bug with encoding PNGs with less than 8 bits per channel.
1512 *) 29 dec 2006: Added support for encoding images without alpha channel, and
1513  cleaned out code as well as making certain parts faster.
1514 *) 28 dec 2006: Added "Settings" to the encoder.
1515 *) 26 dec 2006: The encoder now does LZ77 encoding and produces much smaller files now.
1516  Removed some code duplication in the decoder. Fixed little bug in an example.
1517 *) 09 dec 2006: (!) Placed output parameters of public functions as first parameter.
1518  Fixed a bug of the decoder with 16-bit per color.
1519 *) 15 okt 2006: Changed documentation structure
1520 *) 09 okt 2006: Encoder class added. It encodes a valid PNG image from the
1521  given image buffer, however for now it's not compressed.
1522 *) 08 sep 2006: (!) Changed to interface with a Decoder class
1523 *) 30 jul 2006: (!) LodePNG_InfoPng , width and height are now retrieved in different
1524  way. Renamed decodePNG to decodePNGGeneric.
1525 *) 29 jul 2006: (!) Changed the interface: image info is now returned as a
1526  struct of type LodePNG::LodePNG_Info, instead of a vector, which was a bit clumsy.
1527 *) 28 jul 2006: Cleaned the code and added new error checks.
1528  Corrected terminology "deflate" into "inflate".
1529 *) 23 jun 2006: Added SDL example in the documentation in the header, this
1530  example allows easy debugging by displaying the PNG and its transparency.
1531 *) 22 jun 2006: (!) Changed way to obtain error value. Added
1532  loadFile function for convenience. Made decodePNG32 faster.
1533 *) 21 jun 2006: (!) Changed type of info vector to unsigned.
1534  Changed position of palette in info vector. Fixed an important bug that
1535  happened on PNGs with an uncompressed block.
1536 *) 16 jun 2006: Internally changed unsigned into unsigned where
1537  needed, and performed some optimizations.
1538 *) 07 jun 2006: (!) Renamed functions to decodePNG and placed them
1539  in LodePNG namespace. Changed the order of the parameters. Rewrote the
1540  documentation in the header. Renamed files to lodepng.c and lodepng.h
1541 *) 22 apr 2006: Optimized and improved some code
1542 *) 07 sep 2005: (!) Changed to std::vector interface
1543 *) 12 aug 2005: Initial release (C++, decoder only)
1546 12. contact information
1547 -----------------------
1549 Feel free to contact me with suggestions, problems, comments, ... concerning
1550 LodePNG. If you encounter a PNG image that doesn't work properly with this
1551 decoder, feel free to send it and I'll use it to find and fix the problem.
1553 My email address is (puzzle the account and domain together with an @ symbol):
1554 Domain: gmail dot com.
1555 Account: lode dot vandevenne.
1558 Copyright (c) 2005-2015 Lode Vandevenne
1559 */
1561 #endif
Definition: m65-memcontent-generator.py:119
Uint32 * palette
Definition: vic4_palette.c:33
def r
Definition: compress_sd_image.py:76
Uint8 buf[512]
Definition: fat32.c:155