1 /* 2 LodePNG version 20201017 3 4 Copyright (c) 2005-2020 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 #include "../../../lvgl.h" 32 #if LV_USE_PNG 33 extern const char* LODEPNG_VERSION_STRING; 34 35 /* 36 The following #defines are used to create code sections. They can be disabled 37 to disable code sections, which can give faster compile time and smaller binary. 38 The "NO_COMPILE" defines are designed to be used to pass as defines to the 39 compiler command to disable them without modifying this header, e.g. 40 -DLODEPNG_NO_COMPILE_ZLIB for gcc. 41 In addition to those below, you can also define LODEPNG_NO_COMPILE_CRC to 42 allow implementing a custom lodepng_crc32. 43 */ 44 /*deflate & zlib. If disabled, you must specify alternative zlib functions in 45 the custom_zlib field of the compress and decompress settings*/ 46 #ifndef LODEPNG_NO_COMPILE_ZLIB 47 #define LODEPNG_COMPILE_ZLIB 48 #endif 49 50 /*png encoder and png decoder*/ 51 #ifndef LODEPNG_NO_COMPILE_PNG 52 #define LODEPNG_COMPILE_PNG 53 #endif 54 55 /*deflate&zlib decoder and png decoder*/ 56 #ifndef LODEPNG_NO_COMPILE_DECODER 57 #define LODEPNG_COMPILE_DECODER 58 #endif 59 60 /*deflate&zlib encoder and png encoder*/ 61 #ifndef LODEPNG_NO_COMPILE_ENCODER 62 #define LODEPNG_COMPILE_ENCODER 63 #endif 64 65 /*the optional built in harddisk file loading and saving functions*/ 66 #ifndef LODEPNG_NO_COMPILE_DISK 67 #define LODEPNG_COMPILE_DISK 68 #endif 69 70 /*support for chunks other than IHDR, IDAT, PLTE, tRNS, IEND: ancillary and unknown chunks*/ 71 #ifndef LODEPNG_NO_COMPILE_ANCILLARY_CHUNKS 72 #define LODEPNG_COMPILE_ANCILLARY_CHUNKS 73 #endif 74 75 /*ability to convert error numerical codes to English text string*/ 76 #ifndef LODEPNG_NO_COMPILE_ERROR_TEXT 77 #define LODEPNG_COMPILE_ERROR_TEXT 78 #endif 79 80 /*Compile the default allocators (C's free, malloc and realloc). If you disable this, 81 you can define the functions lodepng_free, lodepng_malloc and lodepng_realloc in your 82 source files with custom allocators.*/ 83 #ifndef LODEPNG_NO_COMPILE_ALLOCATORS 84 #define LODEPNG_COMPILE_ALLOCATORS 85 #endif 86 87 /*compile the C++ version (you can disable the C++ wrapper here even when compiling for C++)*/ 88 #ifdef __cplusplus 89 #ifndef LODEPNG_NO_COMPILE_CPP 90 #define LODEPNG_COMPILE_CPP 91 #endif 92 #endif 93 94 #ifdef LODEPNG_COMPILE_CPP 95 #include <vector> 96 #include <string> 97 #endif /*LODEPNG_COMPILE_CPP*/ 98 99 #ifdef LODEPNG_COMPILE_PNG 100 /*The PNG color types (also used for raw image).*/ 101 typedef enum LodePNGColorType { 102 LCT_GREY = 0, /*grayscale: 1,2,4,8,16 bit*/ 103 LCT_RGB = 2, /*RGB: 8,16 bit*/ 104 LCT_PALETTE = 3, /*palette: 1,2,4,8 bit*/ 105 LCT_GREY_ALPHA = 4, /*grayscale with alpha: 8,16 bit*/ 106 LCT_RGBA = 6, /*RGB with alpha: 8,16 bit*/ 107 /*LCT_MAX_OCTET_VALUE lets the compiler allow this enum to represent any invalid 108 byte value from 0 to 255 that could be present in an invalid PNG file header. Do 109 not use, compare with or set the name LCT_MAX_OCTET_VALUE, instead either use 110 the valid color type names above, or numeric values like 1 or 7 when checking for 111 particular disallowed color type byte values, or cast to integer to print it.*/ 112 LCT_MAX_OCTET_VALUE = 255 113 } LodePNGColorType; 114 115 #ifdef LODEPNG_COMPILE_DECODER 116 /* 117 Converts PNG data in memory to raw pixel data. 118 out: Output parameter. Pointer to buffer that will contain the raw pixel data. 119 After decoding, its size is w * h * (bytes per pixel) bytes larger than 120 initially. Bytes per pixel depends on colortype and bitdepth. 121 Must be freed after usage with free(*out). 122 Note: for 16-bit per channel colors, uses big endian format like PNG does. 123 w: Output parameter. Pointer to width of pixel data. 124 h: Output parameter. Pointer to height of pixel data. 125 in: Memory buffer with the PNG file. 126 insize: size of the in buffer. 127 colortype: the desired color type for the raw output image. See explanation on PNG color types. 128 bitdepth: the desired bit depth for the raw output image. See explanation on PNG color types. 129 Return value: LodePNG error code (0 means no error). 130 */ 131 unsigned lodepng_decode_memory(unsigned char** out, unsigned* w, unsigned* h, 132 const unsigned char* in, size_t insize, 133 LodePNGColorType colortype, unsigned bitdepth); 134 135 /*Same as lodepng_decode_memory, but always decodes to 32-bit RGBA raw image*/ 136 unsigned lodepng_decode32(unsigned char** out, unsigned* w, unsigned* h, 137 const unsigned char* in, size_t insize); 138 139 /*Same as lodepng_decode_memory, but always decodes to 24-bit RGB raw image*/ 140 unsigned lodepng_decode24(unsigned char** out, unsigned* w, unsigned* h, 141 const unsigned char* in, size_t insize); 142 143 #ifdef LODEPNG_COMPILE_DISK 144 /* 145 Load PNG from disk, from file with given name. 146 Same as the other decode functions, but instead takes a filename as input. 147 */ 148 unsigned lodepng_decode_file(unsigned char** out, unsigned* w, unsigned* h, 149 const char* filename, 150 LodePNGColorType colortype, unsigned bitdepth); 151 152 /*Same as lodepng_decode_file, but always decodes to 32-bit RGBA raw image.*/ 153 unsigned lodepng_decode32_file(unsigned char** out, unsigned* w, unsigned* h, 154 const char* filename); 155 156 /*Same as lodepng_decode_file, but always decodes to 24-bit RGB raw image.*/ 157 unsigned lodepng_decode24_file(unsigned char** out, unsigned* w, unsigned* h, 158 const char* filename); 159 #endif /*LODEPNG_COMPILE_DISK*/ 160 #endif /*LODEPNG_COMPILE_DECODER*/ 161 162 163 #ifdef LODEPNG_COMPILE_ENCODER 164 /* 165 Converts raw pixel data into a PNG image in memory. The colortype and bitdepth 166 of the output PNG image cannot be chosen, they are automatically determined 167 by the colortype, bitdepth and content of the input pixel data. 168 Note: for 16-bit per channel colors, needs big endian format like PNG does. 169 out: Output parameter. Pointer to buffer that will contain the PNG image data. 170 Must be freed after usage with free(*out). 171 outsize: Output parameter. Pointer to the size in bytes of the out buffer. 172 image: The raw pixel data to encode. The size of this buffer should be 173 w * h * (bytes per pixel), bytes per pixel depends on colortype and bitdepth. 174 w: width of the raw pixel data in pixels. 175 h: height of the raw pixel data in pixels. 176 colortype: the color type of the raw input image. See explanation on PNG color types. 177 bitdepth: the bit depth of the raw input image. See explanation on PNG color types. 178 Return value: LodePNG error code (0 means no error). 179 */ 180 unsigned lodepng_encode_memory(unsigned char** out, size_t* outsize, 181 const unsigned char* image, unsigned w, unsigned h, 182 LodePNGColorType colortype, unsigned bitdepth); 183 184 /*Same as lodepng_encode_memory, but always encodes from 32-bit RGBA raw image.*/ 185 unsigned lodepng_encode32(unsigned char** out, size_t* outsize, 186 const unsigned char* image, unsigned w, unsigned h); 187 188 /*Same as lodepng_encode_memory, but always encodes from 24-bit RGB raw image.*/ 189 unsigned lodepng_encode24(unsigned char** out, size_t* outsize, 190 const unsigned char* image, unsigned w, unsigned h); 191 192 #ifdef LODEPNG_COMPILE_DISK 193 /* 194 Converts raw pixel data into a PNG file on disk. 195 Same as the other encode functions, but instead takes a filename as output. 196 NOTE: This overwrites existing files without warning! 197 */ 198 unsigned lodepng_encode_file(const char* filename, 199 const unsigned char* image, unsigned w, unsigned h, 200 LodePNGColorType colortype, unsigned bitdepth); 201 202 /*Same as lodepng_encode_file, but always encodes from 32-bit RGBA raw image.*/ 203 unsigned lodepng_encode32_file(const char* filename, 204 const unsigned char* image, unsigned w, unsigned h); 205 206 /*Same as lodepng_encode_file, but always encodes from 24-bit RGB raw image.*/ 207 unsigned lodepng_encode24_file(const char* filename, 208 const unsigned char* image, unsigned w, unsigned h); 209 #endif /*LODEPNG_COMPILE_DISK*/ 210 #endif /*LODEPNG_COMPILE_ENCODER*/ 211 212 213 #ifdef LODEPNG_COMPILE_CPP 214 namespace lodepng { 215 #ifdef LODEPNG_COMPILE_DECODER 216 /*Same as lodepng_decode_memory, but decodes to an std::vector. The colortype 217 is the format to output the pixels to. Default is RGBA 8-bit per channel.*/ 218 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h, 219 const unsigned char* in, size_t insize, 220 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8); 221 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h, 222 const std::vector<unsigned char>& in, 223 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8); 224 #ifdef LODEPNG_COMPILE_DISK 225 /* 226 Converts PNG file from disk to raw pixel data in memory. 227 Same as the other decode functions, but instead takes a filename as input. 228 */ 229 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h, 230 const std::string& filename, 231 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8); 232 #endif /* LODEPNG_COMPILE_DISK */ 233 #endif /* LODEPNG_COMPILE_DECODER */ 234 235 #ifdef LODEPNG_COMPILE_ENCODER 236 /*Same as lodepng_encode_memory, but encodes to an std::vector. colortype 237 is that of the raw input data. The output PNG color type will be auto chosen.*/ 238 unsigned encode(std::vector<unsigned char>& out, 239 const unsigned char* in, unsigned w, unsigned h, 240 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8); 241 unsigned encode(std::vector<unsigned char>& out, 242 const std::vector<unsigned char>& in, unsigned w, unsigned h, 243 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8); 244 #ifdef LODEPNG_COMPILE_DISK 245 /* 246 Converts 32-bit RGBA raw pixel data into a PNG file on disk. 247 Same as the other encode functions, but instead takes a filename as output. 248 NOTE: This overwrites existing files without warning! 249 */ 250 unsigned encode(const std::string& filename, 251 const unsigned char* in, unsigned w, unsigned h, 252 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8); 253 unsigned encode(const std::string& filename, 254 const std::vector<unsigned char>& in, unsigned w, unsigned h, 255 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8); 256 #endif /* LODEPNG_COMPILE_DISK */ 257 #endif /* LODEPNG_COMPILE_ENCODER */ 258 } /* namespace lodepng */ 259 #endif /*LODEPNG_COMPILE_CPP*/ 260 #endif /*LODEPNG_COMPILE_PNG*/ 261 262 #ifdef LODEPNG_COMPILE_ERROR_TEXT 263 /*Returns an English description of the numerical error code.*/ 264 const char* lodepng_error_text(unsigned code); 265 #endif /*LODEPNG_COMPILE_ERROR_TEXT*/ 266 267 #ifdef LODEPNG_COMPILE_DECODER 268 /*Settings for zlib decompression*/ 269 typedef struct LodePNGDecompressSettings LodePNGDecompressSettings; 270 struct LodePNGDecompressSettings { 271 /* Check LodePNGDecoderSettings for more ignorable errors such as ignore_crc */ 272 unsigned ignore_adler32; /*if 1, continue and don't give an error message if the Adler32 checksum is corrupted*/ 273 unsigned ignore_nlen; /*ignore complement of len checksum in uncompressed blocks*/ 274 275 /*Maximum decompressed size, beyond this the decoder may (and is encouraged to) stop decoding, 276 return an error, output a data size > max_output_size and all the data up to that point. This is 277 not hard limit nor a guarantee, but can prevent excessive memory usage. This setting is 278 ignored by the PNG decoder, but is used by the deflate/zlib decoder and can be used by custom ones. 279 Set to 0 to impose no limit (the default).*/ 280 size_t max_output_size; 281 282 /*use custom zlib decoder instead of built in one (default: null). 283 Should return 0 if success, any non-0 if error (numeric value not exposed).*/ 284 unsigned (*custom_zlib)(unsigned char**, size_t*, 285 const unsigned char*, size_t, 286 const LodePNGDecompressSettings*); 287 /*use custom deflate decoder instead of built in one (default: null) 288 if custom_zlib is not null, custom_inflate is ignored (the zlib format uses deflate). 289 Should return 0 if success, any non-0 if error (numeric value not exposed).*/ 290 unsigned (*custom_inflate)(unsigned char**, size_t*, 291 const unsigned char*, size_t, 292 const LodePNGDecompressSettings*); 293 294 const void* custom_context; /*optional custom settings for custom functions*/ 295 }; 296 297 extern const LodePNGDecompressSettings lodepng_default_decompress_settings; 298 void lodepng_decompress_settings_init(LodePNGDecompressSettings* settings); 299 #endif /*LODEPNG_COMPILE_DECODER*/ 300 301 #ifdef LODEPNG_COMPILE_ENCODER 302 /* 303 Settings for zlib compression. Tweaking these settings tweaks the balance 304 between speed and compression ratio. 305 */ 306 typedef struct LodePNGCompressSettings LodePNGCompressSettings; 307 struct LodePNGCompressSettings /*deflate = compress*/ { 308 /*LZ77 related settings*/ 309 unsigned btype; /*the block type for LZ (0, 1, 2 or 3, see zlib standard). Should be 2 for proper compression.*/ 310 unsigned use_lz77; /*whether or not to use LZ77. Should be 1 for proper compression.*/ 311 unsigned windowsize; /*must be a power of two <= 32768. higher compresses more but is slower. Default value: 2048.*/ 312 unsigned minmatch; /*minimum lz77 length. 3 is normally best, 6 can be better for some PNGs. Default: 0*/ 313 unsigned nicematch; /*stop searching if >= this length found. Set to 258 for best compression. Default: 128*/ 314 unsigned lazymatching; /*use lazy matching: better compression but a bit slower. Default: true*/ 315 316 /*use custom zlib encoder instead of built in one (default: null)*/ 317 unsigned (*custom_zlib)(unsigned char**, size_t*, 318 const unsigned char*, size_t, 319 const LodePNGCompressSettings*); 320 /*use custom deflate encoder instead of built in one (default: null) 321 if custom_zlib is used, custom_deflate is ignored since only the built in 322 zlib function will call custom_deflate*/ 323 unsigned (*custom_deflate)(unsigned char**, size_t*, 324 const unsigned char*, size_t, 325 const LodePNGCompressSettings*); 326 327 const void* custom_context; /*optional custom settings for custom functions*/ 328 }; 329 330 extern const LodePNGCompressSettings lodepng_default_compress_settings; 331 void lodepng_compress_settings_init(LodePNGCompressSettings* settings); 332 #endif /*LODEPNG_COMPILE_ENCODER*/ 333 334 #ifdef LODEPNG_COMPILE_PNG 335 /* 336 Color mode of an image. Contains all information required to decode the pixel 337 bits to RGBA colors. This information is the same as used in the PNG file 338 format, and is used both for PNG and raw image data in LodePNG. 339 */ 340 typedef struct LodePNGColorMode { 341 /*header (IHDR)*/ 342 LodePNGColorType colortype; /*color type, see PNG standard or documentation further in this header file*/ 343 unsigned bitdepth; /*bits per sample, see PNG standard or documentation further in this header file*/ 344 345 /* 346 palette (PLTE and tRNS) 347 348 Dynamically allocated with the colors of the palette, including alpha. 349 This field may not be allocated directly, use lodepng_color_mode_init first, 350 then lodepng_palette_add per color to correctly initialize it (to ensure size 351 of exactly 1024 bytes). 352 353 The alpha channels must be set as well, set them to 255 for opaque images. 354 355 When decoding, by default you can ignore this palette, since LodePNG already 356 fills the palette colors in the pixels of the raw RGBA output. 357 358 The palette is only supported for color type 3. 359 */ 360 unsigned char* palette; /*palette in RGBARGBA... order. Must be either 0, or when allocated must have 1024 bytes*/ 361 size_t palettesize; /*palette size in number of colors (amount of used bytes is 4 * palettesize)*/ 362 363 /* 364 transparent color key (tRNS) 365 366 This color uses the same bit depth as the bitdepth value in this struct, which can be 1-bit to 16-bit. 367 For grayscale PNGs, r, g and b will all 3 be set to the same. 368 369 When decoding, by default you can ignore this information, since LodePNG sets 370 pixels with this key to transparent already in the raw RGBA output. 371 372 The color key is only supported for color types 0 and 2. 373 */ 374 unsigned key_defined; /*is a transparent color key given? 0 = false, 1 = true*/ 375 unsigned key_r; /*red/grayscale component of color key*/ 376 unsigned key_g; /*green component of color key*/ 377 unsigned key_b; /*blue component of color key*/ 378 } LodePNGColorMode; 379 380 /*init, cleanup and copy functions to use with this struct*/ 381 void lodepng_color_mode_init(LodePNGColorMode* info); 382 void lodepng_color_mode_cleanup(LodePNGColorMode* info); 383 /*return value is error code (0 means no error)*/ 384 unsigned lodepng_color_mode_copy(LodePNGColorMode* dest, const LodePNGColorMode* source); 385 /* Makes a temporary LodePNGColorMode that does not need cleanup (no palette) */ 386 LodePNGColorMode lodepng_color_mode_make(LodePNGColorType colortype, unsigned bitdepth); 387 388 void lodepng_palette_clear(LodePNGColorMode* info); 389 /*add 1 color to the palette*/ 390 unsigned lodepng_palette_add(LodePNGColorMode* info, 391 unsigned char r, unsigned char g, unsigned char b, unsigned char a); 392 393 /*get the total amount of bits per pixel, based on colortype and bitdepth in the struct*/ 394 unsigned lodepng_get_bpp(const LodePNGColorMode* info); 395 /*get the amount of color channels used, based on colortype in the struct. 396 If a palette is used, it counts as 1 channel.*/ 397 unsigned lodepng_get_channels(const LodePNGColorMode* info); 398 /*is it a grayscale type? (only colortype 0 or 4)*/ 399 unsigned lodepng_is_greyscale_type(const LodePNGColorMode* info); 400 /*has it got an alpha channel? (only colortype 2 or 6)*/ 401 unsigned lodepng_is_alpha_type(const LodePNGColorMode* info); 402 /*has it got a palette? (only colortype 3)*/ 403 unsigned lodepng_is_palette_type(const LodePNGColorMode* info); 404 /*only returns true if there is a palette and there is a value in the palette with alpha < 255. 405 Loops through the palette to check this.*/ 406 unsigned lodepng_has_palette_alpha(const LodePNGColorMode* info); 407 /* 408 Check if the given color info indicates the possibility of having non-opaque pixels in the PNG image. 409 Returns true if the image can have translucent or invisible pixels (it still be opaque if it doesn't use such pixels). 410 Returns false if the image can only have opaque pixels. 411 In detail, it returns true only if it's a color type with alpha, or has a palette with non-opaque values, 412 or if "key_defined" is true. 413 */ 414 unsigned lodepng_can_have_alpha(const LodePNGColorMode* info); 415 /*Returns the byte size of a raw image buffer with given width, height and color mode*/ 416 size_t lodepng_get_raw_size(unsigned w, unsigned h, const LodePNGColorMode* color); 417 418 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS 419 /*The information of a Time chunk in PNG.*/ 420 typedef struct LodePNGTime { 421 unsigned year; /*2 bytes used (0-65535)*/ 422 unsigned month; /*1-12*/ 423 unsigned day; /*1-31*/ 424 unsigned hour; /*0-23*/ 425 unsigned minute; /*0-59*/ 426 unsigned second; /*0-60 (to allow for leap seconds)*/ 427 } LodePNGTime; 428 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/ 429 430 /*Information about the PNG image, except pixels, width and height.*/ 431 typedef struct LodePNGInfo { 432 /*header (IHDR), palette (PLTE) and transparency (tRNS) chunks*/ 433 unsigned compression_method;/*compression method of the original file. Always 0.*/ 434 unsigned filter_method; /*filter method of the original file*/ 435 unsigned interlace_method; /*interlace method of the original file: 0=none, 1=Adam7*/ 436 LodePNGColorMode color; /*color type and bits, palette and transparency of the PNG file*/ 437 438 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS 439 /* 440 Suggested background color chunk (bKGD) 441 442 This uses the same color mode and bit depth as the PNG (except no alpha channel), 443 with values truncated to the bit depth in the unsigned integer. 444 445 For grayscale and palette PNGs, the value is stored in background_r. The values 446 in background_g and background_b are then unused. 447 448 So when decoding, you may get these in a different color mode than the one you requested 449 for the raw pixels. 450 451 When encoding with auto_convert, you must use the color model defined in info_png.color for 452 these values. The encoder normally ignores info_png.color when auto_convert is on, but will 453 use it to interpret these values (and convert copies of them to its chosen color model). 454 455 When encoding, avoid setting this to an expensive color, such as a non-gray value 456 when the image is gray, or the compression will be worse since it will be forced to 457 write the PNG with a more expensive color mode (when auto_convert is on). 458 459 The decoder does not use this background color to edit the color of pixels. This is a 460 completely optional metadata feature. 461 */ 462 unsigned background_defined; /*is a suggested background color given?*/ 463 unsigned background_r; /*red/gray/palette component of suggested background color*/ 464 unsigned background_g; /*green component of suggested background color*/ 465 unsigned background_b; /*blue component of suggested background color*/ 466 467 /* 468 Non-international text chunks (tEXt and zTXt) 469 470 The char** arrays each contain num strings. The actual messages are in 471 text_strings, while text_keys are keywords that give a short description what 472 the actual text represents, e.g. Title, Author, Description, or anything else. 473 474 All the string fields below including strings, keys, names and language tags are null terminated. 475 The PNG specification uses null characters for the keys, names and tags, and forbids null 476 characters to appear in the main text which is why we can use null termination everywhere here. 477 478 A keyword is minimum 1 character and maximum 79 characters long (plus the 479 additional null terminator). It's discouraged to use a single line length 480 longer than 79 characters for texts. 481 482 Don't allocate these text buffers yourself. Use the init/cleanup functions 483 correctly and use lodepng_add_text and lodepng_clear_text. 484 485 Standard text chunk keywords and strings are encoded using Latin-1. 486 */ 487 size_t text_num; /*the amount of texts in these char** buffers (there may be more texts in itext)*/ 488 char** text_keys; /*the keyword of a text chunk (e.g. "Comment")*/ 489 char** text_strings; /*the actual text*/ 490 491 /* 492 International text chunks (iTXt) 493 Similar to the non-international text chunks, but with additional strings 494 "langtags" and "transkeys", and the following text encodings are used: 495 keys: Latin-1, langtags: ASCII, transkeys and strings: UTF-8. 496 keys must be 1-79 characters (plus the additional null terminator), the other 497 strings are any length. 498 */ 499 size_t itext_num; /*the amount of international texts in this PNG*/ 500 char** itext_keys; /*the English keyword of the text chunk (e.g. "Comment")*/ 501 char** itext_langtags; /*language tag for this text's language, ISO/IEC 646 string, e.g. ISO 639 language tag*/ 502 char** itext_transkeys; /*keyword translated to the international language - UTF-8 string*/ 503 char** itext_strings; /*the actual international text - UTF-8 string*/ 504 505 /*time chunk (tIME)*/ 506 unsigned time_defined; /*set to 1 to make the encoder generate a tIME chunk*/ 507 LodePNGTime time; 508 509 /*phys chunk (pHYs)*/ 510 unsigned phys_defined; /*if 0, there is no pHYs chunk and the values below are undefined, if 1 else there is one*/ 511 unsigned phys_x; /*pixels per unit in x direction*/ 512 unsigned phys_y; /*pixels per unit in y direction*/ 513 unsigned phys_unit; /*may be 0 (unknown unit) or 1 (metre)*/ 514 515 /* 516 Color profile related chunks: gAMA, cHRM, sRGB, iCPP 517 518 LodePNG does not apply any color conversions on pixels in the encoder or decoder and does not interpret these color 519 profile values. It merely passes on the information. If you wish to use color profiles and convert colors, please 520 use these values with a color management library. 521 522 See the PNG, ICC and sRGB specifications for more information about the meaning of these values. 523 */ 524 525 /* gAMA chunk: optional, overridden by sRGB or iCCP if those are present. */ 526 unsigned gama_defined; /* Whether a gAMA chunk is present (0 = not present, 1 = present). */ 527 unsigned gama_gamma; /* Gamma exponent times 100000 */ 528 529 /* cHRM chunk: optional, overridden by sRGB or iCCP if those are present. */ 530 unsigned chrm_defined; /* Whether a cHRM chunk is present (0 = not present, 1 = present). */ 531 unsigned chrm_white_x; /* White Point x times 100000 */ 532 unsigned chrm_white_y; /* White Point y times 100000 */ 533 unsigned chrm_red_x; /* Red x times 100000 */ 534 unsigned chrm_red_y; /* Red y times 100000 */ 535 unsigned chrm_green_x; /* Green x times 100000 */ 536 unsigned chrm_green_y; /* Green y times 100000 */ 537 unsigned chrm_blue_x; /* Blue x times 100000 */ 538 unsigned chrm_blue_y; /* Blue y times 100000 */ 539 540 /* 541 sRGB chunk: optional. May not appear at the same time as iCCP. 542 If gAMA is also present gAMA must contain value 45455. 543 If cHRM is also present cHRM must contain respectively 31270,32900,64000,33000,30000,60000,15000,6000. 544 */ 545 unsigned srgb_defined; /* Whether an sRGB chunk is present (0 = not present, 1 = present). */ 546 unsigned srgb_intent; /* Rendering intent: 0=perceptual, 1=rel. colorimetric, 2=saturation, 3=abs. colorimetric */ 547 548 /* 549 iCCP chunk: optional. May not appear at the same time as sRGB. 550 551 LodePNG does not parse or use the ICC profile (except its color space header field for an edge case), a 552 separate library to handle the ICC data (not included in LodePNG) format is needed to use it for color 553 management and conversions. 554 555 For encoding, if iCCP is present, gAMA and cHRM are recommended to be added as well with values that match the ICC 556 profile as closely as possible, if you wish to do this you should provide the correct values for gAMA and cHRM and 557 enable their '_defined' flags since LodePNG will not automatically compute them from the ICC profile. 558 559 For encoding, the ICC profile is required by the PNG specification to be an "RGB" profile for non-gray 560 PNG color types and a "GRAY" profile for gray PNG color types. If you disable auto_convert, you must ensure 561 the ICC profile type matches your requested color type, else the encoder gives an error. If auto_convert is 562 enabled (the default), and the ICC profile is not a good match for the pixel data, this will result in an encoder 563 error if the pixel data has non-gray pixels for a GRAY profile, or a silent less-optimal compression of the pixel 564 data if the pixels could be encoded as grayscale but the ICC profile is RGB. 565 566 To avoid this do not set an ICC profile in the image unless there is a good reason for it, and when doing so 567 make sure you compute it carefully to avoid the above problems. 568 */ 569 unsigned iccp_defined; /* Whether an iCCP chunk is present (0 = not present, 1 = present). */ 570 char* iccp_name; /* Null terminated string with profile name, 1-79 bytes */ 571 /* 572 The ICC profile in iccp_profile_size bytes. 573 Don't allocate this buffer yourself. Use the init/cleanup functions 574 correctly and use lodepng_set_icc and lodepng_clear_icc. 575 */ 576 unsigned char* iccp_profile; 577 unsigned iccp_profile_size; /* The size of iccp_profile in bytes */ 578 579 /* End of color profile related chunks */ 580 581 582 /* 583 unknown chunks: chunks not known by LodePNG, passed on byte for byte. 584 585 There are 3 buffers, one for each position in the PNG where unknown chunks can appear. 586 Each buffer contains all unknown chunks for that position consecutively. 587 The 3 positions are: 588 0: between IHDR and PLTE, 1: between PLTE and IDAT, 2: between IDAT and IEND. 589 590 For encoding, do not store critical chunks or known chunks that are enabled with a "_defined" flag 591 above in here, since the encoder will blindly follow this and could then encode an invalid PNG file 592 (such as one with two IHDR chunks or the disallowed combination of sRGB with iCCP). But do use 593 this if you wish to store an ancillary chunk that is not supported by LodePNG (such as sPLT or hIST), 594 or any non-standard PNG chunk. 595 596 Do not allocate or traverse this data yourself. Use the chunk traversing functions declared 597 later, such as lodepng_chunk_next and lodepng_chunk_append, to read/write this struct. 598 */ 599 unsigned char* unknown_chunks_data[3]; 600 size_t unknown_chunks_size[3]; /*size in bytes of the unknown chunks, given for protection*/ 601 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/ 602 } LodePNGInfo; 603 604 /*init, cleanup and copy functions to use with this struct*/ 605 void lodepng_info_init(LodePNGInfo* info); 606 void lodepng_info_cleanup(LodePNGInfo* info); 607 /*return value is error code (0 means no error)*/ 608 unsigned lodepng_info_copy(LodePNGInfo* dest, const LodePNGInfo* source); 609 610 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS 611 unsigned lodepng_add_text(LodePNGInfo* info, const char* key, const char* str); /*push back both texts at once*/ 612 void lodepng_clear_text(LodePNGInfo* info); /*use this to clear the texts again after you filled them in*/ 613 614 unsigned lodepng_add_itext(LodePNGInfo* info, const char* key, const char* langtag, 615 const char* transkey, const char* str); /*push back the 4 texts of 1 chunk at once*/ 616 void lodepng_clear_itext(LodePNGInfo* info); /*use this to clear the itexts again after you filled them in*/ 617 618 /*replaces if exists*/ 619 unsigned lodepng_set_icc(LodePNGInfo* info, const char* name, const unsigned char* profile, unsigned profile_size); 620 void lodepng_clear_icc(LodePNGInfo* info); /*use this to clear the texts again after you filled them in*/ 621 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/ 622 623 /* 624 Converts raw buffer from one color type to another color type, based on 625 LodePNGColorMode structs to describe the input and output color type. 626 See the reference manual at the end of this header file to see which color conversions are supported. 627 return value = LodePNG error code (0 if all went ok, an error if the conversion isn't supported) 628 The out buffer must have size (w * h * bpp + 7) / 8, where bpp is the bits per pixel 629 of the output color type (lodepng_get_bpp). 630 For < 8 bpp images, there should not be padding bits at the end of scanlines. 631 For 16-bit per channel colors, uses big endian format like PNG does. 632 Return value is LodePNG error code 633 */ 634 unsigned lodepng_convert(unsigned char* out, const unsigned char* in, 635 const LodePNGColorMode* mode_out, const LodePNGColorMode* mode_in, 636 unsigned w, unsigned h); 637 638 #ifdef LODEPNG_COMPILE_DECODER 639 /* 640 Settings for the decoder. This contains settings for the PNG and the Zlib 641 decoder, but not the Info settings from the Info structs. 642 */ 643 typedef struct LodePNGDecoderSettings { 644 LodePNGDecompressSettings zlibsettings; /*in here is the setting to ignore Adler32 checksums*/ 645 646 /* Check LodePNGDecompressSettings for more ignorable errors such as ignore_adler32 */ 647 unsigned ignore_crc; /*ignore CRC checksums*/ 648 unsigned ignore_critical; /*ignore unknown critical chunks*/ 649 unsigned ignore_end; /*ignore issues at end of file if possible (missing IEND chunk, too large chunk, ...)*/ 650 /* TODO: make a system involving warnings with levels and a strict mode instead. Other potentially recoverable 651 errors: srgb rendering intent value, size of content of ancillary chunks, more than 79 characters for some 652 strings, placement/combination rules for ancillary chunks, crc of unknown chunks, allowed characters 653 in string keys, etc... */ 654 655 unsigned color_convert; /*whether to convert the PNG to the color type you want. Default: yes*/ 656 657 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS 658 unsigned read_text_chunks; /*if false but remember_unknown_chunks is true, they're stored in the unknown chunks*/ 659 660 /*store all bytes from unknown chunks in the LodePNGInfo (off by default, useful for a png editor)*/ 661 unsigned remember_unknown_chunks; 662 663 /* maximum size for decompressed text chunks. If a text chunk's text is larger than this, an error is returned, 664 unless reading text chunks is disabled or this limit is set higher or disabled. Set to 0 to allow any size. 665 By default it is a value that prevents unreasonably large strings from hogging memory. */ 666 size_t max_text_size; 667 668 /* maximum size for compressed ICC chunks. If the ICC profile is larger than this, an error will be returned. Set to 669 0 to allow any size. By default this is a value that prevents ICC profiles that would be much larger than any 670 legitimate profile could be to hog memory. */ 671 size_t max_icc_size; 672 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/ 673 } LodePNGDecoderSettings; 674 675 void lodepng_decoder_settings_init(LodePNGDecoderSettings* settings); 676 #endif /*LODEPNG_COMPILE_DECODER*/ 677 678 #ifdef LODEPNG_COMPILE_ENCODER 679 /*automatically use color type with less bits per pixel if losslessly possible. Default: AUTO*/ 680 typedef enum LodePNGFilterStrategy { 681 /*every filter at zero*/ 682 LFS_ZERO = 0, 683 /*every filter at 1, 2, 3 or 4 (paeth), unlike LFS_ZERO not a good choice, but for testing*/ 684 LFS_ONE = 1, 685 LFS_TWO = 2, 686 LFS_THREE = 3, 687 LFS_FOUR = 4, 688 /*Use filter that gives minimum sum, as described in the official PNG filter heuristic.*/ 689 LFS_MINSUM, 690 /*Use the filter type that gives smallest Shannon entropy for this scanline. Depending 691 on the image, this is better or worse than minsum.*/ 692 LFS_ENTROPY, 693 /* 694 Brute-force-search PNG filters by compressing each filter for each scanline. 695 Experimental, very slow, and only rarely gives better compression than MINSUM. 696 */ 697 LFS_BRUTE_FORCE, 698 /*use predefined_filters buffer: you specify the filter type for each scanline*/ 699 LFS_PREDEFINED 700 } LodePNGFilterStrategy; 701 702 /*Gives characteristics about the integer RGBA colors of the image (count, alpha channel usage, bit depth, ...), 703 which helps decide which color model to use for encoding. 704 Used internally by default if "auto_convert" is enabled. Public because it's useful for custom algorithms.*/ 705 typedef struct LodePNGColorStats { 706 unsigned colored; /*not grayscale*/ 707 unsigned key; /*image is not opaque and color key is possible instead of full alpha*/ 708 unsigned short key_r; /*key values, always as 16-bit, in 8-bit case the byte is duplicated, e.g. 65535 means 255*/ 709 unsigned short key_g; 710 unsigned short key_b; 711 unsigned alpha; /*image is not opaque and alpha channel or alpha palette required*/ 712 unsigned numcolors; /*amount of colors, up to 257. Not valid if bits == 16 or allow_palette is disabled.*/ 713 unsigned char palette[1024]; /*Remembers up to the first 256 RGBA colors, in no particular order, only valid when numcolors is valid*/ 714 unsigned bits; /*bits per channel (not for palette). 1,2 or 4 for grayscale only. 16 if 16-bit per channel required.*/ 715 size_t numpixels; 716 717 /*user settings for computing/using the stats*/ 718 unsigned allow_palette; /*default 1. if 0, disallow choosing palette colortype in auto_choose_color, and don't count numcolors*/ 719 unsigned allow_greyscale; /*default 1. if 0, choose RGB or RGBA even if the image only has gray colors*/ 720 } LodePNGColorStats; 721 722 void lodepng_color_stats_init(LodePNGColorStats* stats); 723 724 /*Get a LodePNGColorStats of the image. The stats must already have been inited. 725 Returns error code (e.g. alloc fail) or 0 if ok.*/ 726 unsigned lodepng_compute_color_stats(LodePNGColorStats* stats, 727 const unsigned char* image, unsigned w, unsigned h, 728 const LodePNGColorMode* mode_in); 729 730 /*Settings for the encoder.*/ 731 typedef struct LodePNGEncoderSettings { 732 LodePNGCompressSettings zlibsettings; /*settings for the zlib encoder, such as window size, ...*/ 733 734 unsigned auto_convert; /*automatically choose output PNG color type. Default: true*/ 735 736 /*If true, follows the official PNG heuristic: if the PNG uses a palette or lower than 737 8 bit depth, set all filters to zero. Otherwise use the filter_strategy. Note that to 738 completely follow the official PNG heuristic, filter_palette_zero must be true and 739 filter_strategy must be LFS_MINSUM*/ 740 unsigned filter_palette_zero; 741 /*Which filter strategy to use when not using zeroes due to filter_palette_zero. 742 Set filter_palette_zero to 0 to ensure always using your chosen strategy. Default: LFS_MINSUM*/ 743 LodePNGFilterStrategy filter_strategy; 744 /*used if filter_strategy is LFS_PREDEFINED. In that case, this must point to a buffer with 745 the same length as the amount of scanlines in the image, and each value must <= 5. You 746 have to cleanup this buffer, LodePNG will never free it. Don't forget that filter_palette_zero 747 must be set to 0 to ensure this is also used on palette or low bitdepth images.*/ 748 const unsigned char* predefined_filters; 749 750 /*force creating a PLTE chunk if colortype is 2 or 6 (= a suggested palette). 751 If colortype is 3, PLTE is _always_ created.*/ 752 unsigned force_palette; 753 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS 754 /*add LodePNG identifier and version as a text chunk, for debugging*/ 755 unsigned add_id; 756 /*encode text chunks as zTXt chunks instead of tEXt chunks, and use compression in iTXt chunks*/ 757 unsigned text_compression; 758 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/ 759 } LodePNGEncoderSettings; 760 761 void lodepng_encoder_settings_init(LodePNGEncoderSettings* settings); 762 #endif /*LODEPNG_COMPILE_ENCODER*/ 763 764 765 #if defined(LODEPNG_COMPILE_DECODER) || defined(LODEPNG_COMPILE_ENCODER) 766 /*The settings, state and information for extended encoding and decoding.*/ 767 typedef struct LodePNGState { 768 #ifdef LODEPNG_COMPILE_DECODER 769 LodePNGDecoderSettings decoder; /*the decoding settings*/ 770 #endif /*LODEPNG_COMPILE_DECODER*/ 771 #ifdef LODEPNG_COMPILE_ENCODER 772 LodePNGEncoderSettings encoder; /*the encoding settings*/ 773 #endif /*LODEPNG_COMPILE_ENCODER*/ 774 LodePNGColorMode info_raw; /*specifies the format in which you would like to get the raw pixel buffer*/ 775 LodePNGInfo info_png; /*info of the PNG image obtained after decoding*/ 776 unsigned error; 777 } LodePNGState; 778 779 /*init, cleanup and copy functions to use with this struct*/ 780 void lodepng_state_init(LodePNGState* state); 781 void lodepng_state_cleanup(LodePNGState* state); 782 void lodepng_state_copy(LodePNGState* dest, const LodePNGState* source); 783 #endif /* defined(LODEPNG_COMPILE_DECODER) || defined(LODEPNG_COMPILE_ENCODER) */ 784 785 #ifdef LODEPNG_COMPILE_DECODER 786 /* 787 Same as lodepng_decode_memory, but uses a LodePNGState to allow custom settings and 788 getting much more information about the PNG image and color mode. 789 */ 790 unsigned lodepng_decode(unsigned char** out, unsigned* w, unsigned* h, 791 LodePNGState* state, 792 const unsigned char* in, size_t insize); 793 794 /* 795 Read the PNG header, but not the actual data. This returns only the information 796 that is in the IHDR chunk of the PNG, such as width, height and color type. The 797 information is placed in the info_png field of the LodePNGState. 798 */ 799 unsigned lodepng_inspect(unsigned* w, unsigned* h, 800 LodePNGState* state, 801 const unsigned char* in, size_t insize); 802 #endif /*LODEPNG_COMPILE_DECODER*/ 803 804 /* 805 Reads one metadata chunk (other than IHDR) of the PNG file and outputs what it 806 read in the state. Returns error code on failure. 807 Use lodepng_inspect first with a new state, then e.g. lodepng_chunk_find_const 808 to find the desired chunk type, and if non null use lodepng_inspect_chunk (with 809 chunk_pointer - start_of_file as pos). 810 Supports most metadata chunks from the PNG standard (gAMA, bKGD, tEXt, ...). 811 Ignores unsupported, unknown, non-metadata or IHDR chunks (without error). 812 Requirements: &in[pos] must point to start of a chunk, must use regular 813 lodepng_inspect first since format of most other chunks depends on IHDR, and if 814 there is a PLTE chunk, that one must be inspected before tRNS or bKGD. 815 */ 816 unsigned lodepng_inspect_chunk(LodePNGState* state, size_t pos, 817 const unsigned char* in, size_t insize); 818 819 #ifdef LODEPNG_COMPILE_ENCODER 820 /*This function allocates the out buffer with standard malloc and stores the size in *outsize.*/ 821 unsigned lodepng_encode(unsigned char** out, size_t* outsize, 822 const unsigned char* image, unsigned w, unsigned h, 823 LodePNGState* state); 824 #endif /*LODEPNG_COMPILE_ENCODER*/ 825 826 /* 827 The lodepng_chunk functions are normally not needed, except to traverse the 828 unknown chunks stored in the LodePNGInfo struct, or add new ones to it. 829 It also allows traversing the chunks of an encoded PNG file yourself. 830 831 The chunk pointer always points to the beginning of the chunk itself, that is 832 the first byte of the 4 length bytes. 833 834 In the PNG file format, chunks have the following format: 835 -4 bytes length: length of the data of the chunk in bytes (chunk itself is 12 bytes longer) 836 -4 bytes chunk type (ASCII a-z,A-Z only, see below) 837 -length bytes of data (may be 0 bytes if length was 0) 838 -4 bytes of CRC, computed on chunk name + data 839 840 The first chunk starts at the 8th byte of the PNG file, the entire rest of the file 841 exists out of concatenated chunks with the above format. 842 843 PNG standard chunk ASCII naming conventions: 844 -First byte: uppercase = critical, lowercase = ancillary 845 -Second byte: uppercase = public, lowercase = private 846 -Third byte: must be uppercase 847 -Fourth byte: uppercase = unsafe to copy, lowercase = safe to copy 848 */ 849 850 /* 851 Gets the length of the data of the chunk. Total chunk length has 12 bytes more. 852 There must be at least 4 bytes to read from. If the result value is too large, 853 it may be corrupt data. 854 */ 855 unsigned lodepng_chunk_length(const unsigned char* chunk); 856 857 /*puts the 4-byte type in null terminated string*/ 858 void lodepng_chunk_type(char type[5], const unsigned char* chunk); 859 860 /*check if the type is the given type*/ 861 unsigned char lodepng_chunk_type_equals(const unsigned char* chunk, const char* type); 862 863 /*0: it's one of the critical chunk types, 1: it's an ancillary chunk (see PNG standard)*/ 864 unsigned char lodepng_chunk_ancillary(const unsigned char* chunk); 865 866 /*0: public, 1: private (see PNG standard)*/ 867 unsigned char lodepng_chunk_private(const unsigned char* chunk); 868 869 /*0: the chunk is unsafe to copy, 1: the chunk is safe to copy (see PNG standard)*/ 870 unsigned char lodepng_chunk_safetocopy(const unsigned char* chunk); 871 872 /*get pointer to the data of the chunk, where the input points to the header of the chunk*/ 873 unsigned char* lodepng_chunk_data(unsigned char* chunk); 874 const unsigned char* lodepng_chunk_data_const(const unsigned char* chunk); 875 876 /*returns 0 if the crc is correct, 1 if it's incorrect (0 for OK as usual!)*/ 877 unsigned lodepng_chunk_check_crc(const unsigned char* chunk); 878 879 /*generates the correct CRC from the data and puts it in the last 4 bytes of the chunk*/ 880 void lodepng_chunk_generate_crc(unsigned char* chunk); 881 882 /* 883 Iterate to next chunks, allows iterating through all chunks of the PNG file. 884 Input must be at the beginning of a chunk (result of a previous lodepng_chunk_next call, 885 or the 8th byte of a PNG file which always has the first chunk), or alternatively may 886 point to the first byte of the PNG file (which is not a chunk but the magic header, the 887 function will then skip over it and return the first real chunk). 888 Will output pointer to the start of the next chunk, or at or beyond end of the file if there 889 is no more chunk after this or possibly if the chunk is corrupt. 890 Start this process at the 8th byte of the PNG file. 891 In a non-corrupt PNG file, the last chunk should have name "IEND". 892 */ 893 unsigned char* lodepng_chunk_next(unsigned char* chunk, unsigned char* end); 894 const unsigned char* lodepng_chunk_next_const(const unsigned char* chunk, const unsigned char* end); 895 896 /*Finds the first chunk with the given type in the range [chunk, end), or returns NULL if not found.*/ 897 unsigned char* lodepng_chunk_find(unsigned char* chunk, unsigned char* end, const char type[5]); 898 const unsigned char* lodepng_chunk_find_const(const unsigned char* chunk, const unsigned char* end, const char type[5]); 899 900 /* 901 Appends chunk to the data in out. The given chunk should already have its chunk header. 902 The out variable and outsize are updated to reflect the new reallocated buffer. 903 Returns error code (0 if it went ok) 904 */ 905 unsigned lodepng_chunk_append(unsigned char** out, size_t* outsize, const unsigned char* chunk); 906 907 /* 908 Appends new chunk to out. The chunk to append is given by giving its length, type 909 and data separately. The type is a 4-letter string. 910 The out variable and outsize are updated to reflect the new reallocated buffer. 911 Returne error code (0 if it went ok) 912 */ 913 unsigned lodepng_chunk_create(unsigned char** out, size_t* outsize, unsigned length, 914 const char* type, const unsigned char* data); 915 916 917 /*Calculate CRC32 of buffer*/ 918 unsigned lodepng_crc32(const unsigned char* buf, size_t len); 919 #endif /*LODEPNG_COMPILE_PNG*/ 920 921 922 #ifdef LODEPNG_COMPILE_ZLIB 923 /* 924 This zlib part can be used independently to zlib compress and decompress a 925 buffer. It cannot be used to create gzip files however, and it only supports the 926 part of zlib that is required for PNG, it does not support dictionaries. 927 */ 928 929 #ifdef LODEPNG_COMPILE_DECODER 930 /*Inflate a buffer. Inflate is the decompression step of deflate. Out buffer must be freed after use.*/ 931 unsigned lodepng_inflate(unsigned char** out, size_t* outsize, 932 const unsigned char* in, size_t insize, 933 const LodePNGDecompressSettings* settings); 934 935 /* 936 Decompresses Zlib data. Reallocates the out buffer and appends the data. The 937 data must be according to the zlib specification. 938 Either, *out must be NULL and *outsize must be 0, or, *out must be a valid 939 buffer and *outsize its size in bytes. out must be freed by user after usage. 940 */ 941 unsigned lodepng_zlib_decompress(unsigned char** out, size_t* outsize, 942 const unsigned char* in, size_t insize, 943 const LodePNGDecompressSettings* settings); 944 #endif /*LODEPNG_COMPILE_DECODER*/ 945 946 #ifdef LODEPNG_COMPILE_ENCODER 947 /* 948 Compresses data with Zlib. Reallocates the out buffer and appends the data. 949 Zlib adds a small header and trailer around the deflate data. 950 The data is output in the format of the zlib specification. 951 Either, *out must be NULL and *outsize must be 0, or, *out must be a valid 952 buffer and *outsize its size in bytes. out must be freed by user after usage. 953 */ 954 unsigned lodepng_zlib_compress(unsigned char** out, size_t* outsize, 955 const unsigned char* in, size_t insize, 956 const LodePNGCompressSettings* settings); 957 958 /* 959 Find length-limited Huffman code for given frequencies. This function is in the 960 public interface only for tests, it's used internally by lodepng_deflate. 961 */ 962 unsigned lodepng_huffman_code_lengths(unsigned* lengths, const unsigned* frequencies, 963 size_t numcodes, unsigned maxbitlen); 964 965 /*Compress a buffer with deflate. See RFC 1951. Out buffer must be freed after use.*/ 966 unsigned lodepng_deflate(unsigned char** out, size_t* outsize, 967 const unsigned char* in, size_t insize, 968 const LodePNGCompressSettings* settings); 969 970 #endif /*LODEPNG_COMPILE_ENCODER*/ 971 #endif /*LODEPNG_COMPILE_ZLIB*/ 972 973 #ifdef LODEPNG_COMPILE_DISK 974 /* 975 Load a file from disk into buffer. The function allocates the out buffer, and 976 after usage you should free it. 977 out: output parameter, contains pointer to loaded buffer. 978 outsize: output parameter, size of the allocated out buffer 979 filename: the path to the file to load 980 return value: error code (0 means ok) 981 */ 982 unsigned lodepng_load_file(unsigned char** out, size_t* outsize, const char* filename); 983 984 /* 985 Save a file from buffer to disk. Warning, if it exists, this function overwrites 986 the file without warning! 987 buffer: the buffer to write 988 buffersize: size of the buffer to write 989 filename: the path to the file to save to 990 return value: error code (0 means ok) 991 */ 992 unsigned lodepng_save_file(const unsigned char* buffer, size_t buffersize, const char* filename); 993 #endif /*LODEPNG_COMPILE_DISK*/ 994 995 #ifdef LODEPNG_COMPILE_CPP 996 /* The LodePNG C++ wrapper uses std::vectors instead of manually allocated memory buffers. */ 997 namespace lodepng { 998 #ifdef LODEPNG_COMPILE_PNG 999 class State : public LodePNGState { 1000 public: 1001 State(); 1002 State(const State& other); 1003 ~State(); 1004 State& operator=(const State& other); 1005 }; 1006 1007 #ifdef LODEPNG_COMPILE_DECODER 1008 /* Same as other lodepng::decode, but using a State for more settings and information. */ 1009 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h, 1010 State& state, 1011 const unsigned char* in, size_t insize); 1012 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h, 1013 State& state, 1014 const std::vector<unsigned char>& in); 1015 #endif /*LODEPNG_COMPILE_DECODER*/ 1016 1017 #ifdef LODEPNG_COMPILE_ENCODER 1018 /* Same as other lodepng::encode, but using a State for more settings and information. */ 1019 unsigned encode(std::vector<unsigned char>& out, 1020 const unsigned char* in, unsigned w, unsigned h, 1021 State& state); 1022 unsigned encode(std::vector<unsigned char>& out, 1023 const std::vector<unsigned char>& in, unsigned w, unsigned h, 1024 State& state); 1025 #endif /*LODEPNG_COMPILE_ENCODER*/ 1026 1027 #ifdef LODEPNG_COMPILE_DISK 1028 /* 1029 Load a file from disk into an std::vector. 1030 return value: error code (0 means ok) 1031 */ 1032 unsigned load_file(std::vector<unsigned char>& buffer, const std::string& filename); 1033 1034 /* 1035 Save the binary data in an std::vector to a file on disk. The file is overwritten 1036 without warning. 1037 */ 1038 unsigned save_file(const std::vector<unsigned char>& buffer, const std::string& filename); 1039 #endif /* LODEPNG_COMPILE_DISK */ 1040 #endif /* LODEPNG_COMPILE_PNG */ 1041 1042 #ifdef LODEPNG_COMPILE_ZLIB 1043 #ifdef LODEPNG_COMPILE_DECODER 1044 /* Zlib-decompress an unsigned char buffer */ 1045 unsigned decompress(std::vector<unsigned char>& out, const unsigned char* in, size_t insize, 1046 const LodePNGDecompressSettings& settings = lodepng_default_decompress_settings); 1047 1048 /* Zlib-decompress an std::vector */ 1049 unsigned decompress(std::vector<unsigned char>& out, const std::vector<unsigned char>& in, 1050 const LodePNGDecompressSettings& settings = lodepng_default_decompress_settings); 1051 #endif /* LODEPNG_COMPILE_DECODER */ 1052 1053 #ifdef LODEPNG_COMPILE_ENCODER 1054 /* Zlib-compress an unsigned char buffer */ 1055 unsigned compress(std::vector<unsigned char>& out, const unsigned char* in, size_t insize, 1056 const LodePNGCompressSettings& settings = lodepng_default_compress_settings); 1057 1058 /* Zlib-compress an std::vector */ 1059 unsigned compress(std::vector<unsigned char>& out, const std::vector<unsigned char>& in, 1060 const LodePNGCompressSettings& settings = lodepng_default_compress_settings); 1061 #endif /* LODEPNG_COMPILE_ENCODER */ 1062 #endif /* LODEPNG_COMPILE_ZLIB */ 1063 } /* namespace lodepng */ 1064 #endif /*LODEPNG_COMPILE_CPP*/ 1065 1066 /* 1067 TODO: 1068 [.] test if there are no memory leaks or security exploits - done a lot but needs to be checked often 1069 [.] check compatibility with various compilers - done but needs to be redone for every newer version 1070 [X] converting color to 16-bit per channel types 1071 [X] support color profile chunk types (but never let them touch RGB values by default) 1072 [ ] support all public PNG chunk types (almost done except sBIT, sPLT and hIST) 1073 [ ] make sure encoder generates no chunks with size > (2^31)-1 1074 [ ] partial decoding (stream processing) 1075 [X] let the "isFullyOpaque" function check color keys and transparent palettes too 1076 [X] better name for the variables "codes", "codesD", "codelengthcodes", "clcl" and "lldl" 1077 [ ] allow treating some errors like warnings, when image is recoverable (e.g. 69, 57, 58) 1078 [ ] make warnings like: oob palette, checksum fail, data after iend, wrong/unknown crit chunk, no null terminator in text, ... 1079 [ ] error messages with line numbers (and version) 1080 [ ] errors in state instead of as return code? 1081 [ ] new errors/warnings like suspiciously big decompressed ztxt or iccp chunk 1082 [ ] let the C++ wrapper catch exceptions coming from the standard library and return LodePNG error codes 1083 [ ] allow user to provide custom color conversion functions, e.g. for premultiplied alpha, padding bits or not, ... 1084 [ ] allow user to give data (void*) to custom allocator 1085 [X] provide alternatives for C library functions not present on some platforms (memcpy, ...) 1086 */ 1087 1088 #endif /*LV_USE_PNG*/ 1089 1090 #endif /*LODEPNG_H inclusion guard*/ 1091 1092 /* 1093 LodePNG Documentation 1094 --------------------- 1095 1096 0. table of contents 1097 -------------------- 1098 1099 1. about 1100 1.1. supported features 1101 1.2. features not supported 1102 2. C and C++ version 1103 3. security 1104 4. decoding 1105 5. encoding 1106 6. color conversions 1107 6.1. PNG color types 1108 6.2. color conversions 1109 6.3. padding bits 1110 6.4. A note about 16-bits per channel and endianness 1111 7. error values 1112 8. chunks and PNG editing 1113 9. compiler support 1114 10. examples 1115 10.1. decoder C++ example 1116 10.2. decoder C example 1117 11. state settings reference 1118 12. changes 1119 13. contact information 1120 1121 1122 1. about 1123 -------- 1124 1125 PNG is a file format to store raster images losslessly with good compression, 1126 supporting different color types and alpha channel. 1127 1128 LodePNG is a PNG codec according to the Portable Network Graphics (PNG) 1129 Specification (Second Edition) - W3C Recommendation 10 November 2003. 1130 1131 The specifications used are: 1132 1133 *) Portable Network Graphics (PNG) Specification (Second Edition): 1134 http://www.w3.org/TR/2003/REC-PNG-20031110 1135 *) RFC 1950 ZLIB Compressed Data Format version 3.3: 1136 http://www.gzip.org/zlib/rfc-zlib.html 1137 *) RFC 1951 DEFLATE Compressed Data Format Specification ver 1.3: 1138 http://www.gzip.org/zlib/rfc-deflate.html 1139 1140 The most recent version of LodePNG can currently be found at 1141 http://lodev.org/lodepng/ 1142 1143 LodePNG works both in C (ISO C90) and C++, with a C++ wrapper that adds 1144 extra functionality. 1145 1146 LodePNG exists out of two files: 1147 -lodepng.h: the header file for both C and C++ 1148 -lodepng.c(pp): give it the name lodepng.c or lodepng.cpp (or .cc) depending on your usage 1149 1150 If you want to start using LodePNG right away without reading this doc, get the 1151 examples from the LodePNG website to see how to use it in code, or check the 1152 smaller examples in chapter 13 here. 1153 1154 LodePNG is simple but only supports the basic requirements. To achieve 1155 simplicity, the following design choices were made: There are no dependencies 1156 on any external library. There are functions to decode and encode a PNG with 1157 a single function call, and extended versions of these functions taking a 1158 LodePNGState struct allowing to specify or get more information. By default 1159 the colors of the raw image are always RGB or RGBA, no matter what color type 1160 the PNG file uses. To read and write files, there are simple functions to 1161 convert the files to/from buffers in memory. 1162 1163 This all makes LodePNG suitable for loading textures in games, demos and small 1164 programs, ... It's less suitable for full fledged image editors, loading PNGs 1165 over network (it requires all the image data to be available before decoding can 1166 begin), life-critical systems, ... 1167 1168 1.1. supported features 1169 ----------------------- 1170 1171 The following features are supported by the decoder: 1172 1173 *) decoding of PNGs with any color type, bit depth and interlace mode, to a 24- or 32-bit color raw image, 1174 or the same color type as the PNG 1175 *) encoding of PNGs, from any raw image to 24- or 32-bit color, or the same color type as the raw image 1176 *) Adam7 interlace and deinterlace for any color type 1177 *) loading the image from harddisk or decoding it from a buffer from other sources than harddisk 1178 *) support for alpha channels, including RGBA color model, translucent palettes and color keying 1179 *) zlib decompression (inflate) 1180 *) zlib compression (deflate) 1181 *) CRC32 and ADLER32 checksums 1182 *) colorimetric color profile conversions: currently experimentally available in lodepng_util.cpp only, 1183 plus alternatively ability to pass on chroma/gamma/ICC profile information to other color management system. 1184 *) handling of unknown chunks, allowing making a PNG editor that stores custom and unknown chunks. 1185 *) the following chunks are supported by both encoder and decoder: 1186 IHDR: header information 1187 PLTE: color palette 1188 IDAT: pixel data 1189 IEND: the final chunk 1190 tRNS: transparency for palettized images 1191 tEXt: textual information 1192 zTXt: compressed textual information 1193 iTXt: international textual information 1194 bKGD: suggested background color 1195 pHYs: physical dimensions 1196 tIME: modification time 1197 cHRM: RGB chromaticities 1198 gAMA: RGB gamma correction 1199 iCCP: ICC color profile 1200 sRGB: rendering intent 1201 1202 1.2. features not supported 1203 --------------------------- 1204 1205 The following features are _not_ supported: 1206 1207 *) some features needed to make a conformant PNG-Editor might be still missing. 1208 *) partial loading/stream processing. All data must be available and is processed in one call. 1209 *) The following public chunks are not (yet) supported but treated as unknown chunks by LodePNG: 1210 sBIT 1211 hIST 1212 sPLT 1213 1214 1215 2. C and C++ version 1216 -------------------- 1217 1218 The C version uses buffers allocated with alloc that you need to free() 1219 yourself. You need to use init and cleanup functions for each struct whenever 1220 using a struct from the C version to avoid exploits and memory leaks. 1221 1222 The C++ version has extra functions with std::vectors in the interface and the 1223 lodepng::State class which is a LodePNGState with constructor and destructor. 1224 1225 These files work without modification for both C and C++ compilers because all 1226 the additional C++ code is in "#ifdef __cplusplus" blocks that make C-compilers 1227 ignore it, and the C code is made to compile both with strict ISO C90 and C++. 1228 1229 To use the C++ version, you need to rename the source file to lodepng.cpp 1230 (instead of lodepng.c), and compile it with a C++ compiler. 1231 1232 To use the C version, you need to rename the source file to lodepng.c (instead 1233 of lodepng.cpp), and compile it with a C compiler. 1234 1235 1236 3. Security 1237 ----------- 1238 1239 Even if carefully designed, it's always possible that LodePNG contains possible 1240 exploits. If you discover one, please let me know, and it will be fixed. 1241 1242 When using LodePNG, care has to be taken with the C version of LodePNG, as well 1243 as the C-style structs when working with C++. The following conventions are used 1244 for all C-style structs: 1245 1246 -if a struct has a corresponding init function, always call the init function when making a new one 1247 -if a struct has a corresponding cleanup function, call it before the struct disappears to avoid memory leaks 1248 -if a struct has a corresponding copy function, use the copy function instead of "=". 1249 The destination must also be inited already. 1250 1251 1252 4. Decoding 1253 ----------- 1254 1255 Decoding converts a PNG compressed image to a raw pixel buffer. 1256 1257 Most documentation on using the decoder is at its declarations in the header 1258 above. For C, simple decoding can be done with functions such as 1259 lodepng_decode32, and more advanced decoding can be done with the struct 1260 LodePNGState and lodepng_decode. For C++, all decoding can be done with the 1261 various lodepng::decode functions, and lodepng::State can be used for advanced 1262 features. 1263 1264 When using the LodePNGState, it uses the following fields for decoding: 1265 *) LodePNGInfo info_png: it stores extra information about the PNG (the input) in here 1266 *) LodePNGColorMode info_raw: here you can say what color mode of the raw image (the output) you want to get 1267 *) LodePNGDecoderSettings decoder: you can specify a few extra settings for the decoder to use 1268 1269 LodePNGInfo info_png 1270 -------------------- 1271 1272 After decoding, this contains extra information of the PNG image, except the actual 1273 pixels, width and height because these are already gotten directly from the decoder 1274 functions. 1275 1276 It contains for example the original color type of the PNG image, text comments, 1277 suggested background color, etc... More details about the LodePNGInfo struct are 1278 at its declaration documentation. 1279 1280 LodePNGColorMode info_raw 1281 ------------------------- 1282 1283 When decoding, here you can specify which color type you want 1284 the resulting raw image to be. If this is different from the colortype of the 1285 PNG, then the decoder will automatically convert the result. This conversion 1286 always works, except if you want it to convert a color PNG to grayscale or to 1287 a palette with missing colors. 1288 1289 By default, 32-bit color is used for the result. 1290 1291 LodePNGDecoderSettings decoder 1292 ------------------------------ 1293 1294 The settings can be used to ignore the errors created by invalid CRC and Adler32 1295 chunks, and to disable the decoding of tEXt chunks. 1296 1297 There's also a setting color_convert, true by default. If false, no conversion 1298 is done, the resulting data will be as it was in the PNG (after decompression) 1299 and you'll have to puzzle the colors of the pixels together yourself using the 1300 color type information in the LodePNGInfo. 1301 1302 1303 5. Encoding 1304 ----------- 1305 1306 Encoding converts a raw pixel buffer to a PNG compressed image. 1307 1308 Most documentation on using the encoder is at its declarations in the header 1309 above. For C, simple encoding can be done with functions such as 1310 lodepng_encode32, and more advanced decoding can be done with the struct 1311 LodePNGState and lodepng_encode. For C++, all encoding can be done with the 1312 various lodepng::encode functions, and lodepng::State can be used for advanced 1313 features. 1314 1315 Like the decoder, the encoder can also give errors. However it gives less errors 1316 since the encoder input is trusted, the decoder input (a PNG image that could 1317 be forged by anyone) is not trusted. 1318 1319 When using the LodePNGState, it uses the following fields for encoding: 1320 *) LodePNGInfo info_png: here you specify how you want the PNG (the output) to be. 1321 *) LodePNGColorMode info_raw: here you say what color type of the raw image (the input) has 1322 *) LodePNGEncoderSettings encoder: you can specify a few settings for the encoder to use 1323 1324 LodePNGInfo info_png 1325 -------------------- 1326 1327 When encoding, you use this the opposite way as when decoding: for encoding, 1328 you fill in the values you want the PNG to have before encoding. By default it's 1329 not needed to specify a color type for the PNG since it's automatically chosen, 1330 but it's possible to choose it yourself given the right settings. 1331 1332 The encoder will not always exactly match the LodePNGInfo struct you give, 1333 it tries as close as possible. Some things are ignored by the encoder. The 1334 encoder uses, for example, the following settings from it when applicable: 1335 colortype and bitdepth, text chunks, time chunk, the color key, the palette, the 1336 background color, the interlace method, unknown chunks, ... 1337 1338 When encoding to a PNG with colortype 3, the encoder will generate a PLTE chunk. 1339 If the palette contains any colors for which the alpha channel is not 255 (so 1340 there are translucent colors in the palette), it'll add a tRNS chunk. 1341 1342 LodePNGColorMode info_raw 1343 ------------------------- 1344 1345 You specify the color type of the raw image that you give to the input here, 1346 including a possible transparent color key and palette you happen to be using in 1347 your raw image data. 1348 1349 By default, 32-bit color is assumed, meaning your input has to be in RGBA 1350 format with 4 bytes (unsigned chars) per pixel. 1351 1352 LodePNGEncoderSettings encoder 1353 ------------------------------ 1354 1355 The following settings are supported (some are in sub-structs): 1356 *) auto_convert: when this option is enabled, the encoder will 1357 automatically choose the smallest possible color mode (including color key) that 1358 can encode the colors of all pixels without information loss. 1359 *) btype: the block type for LZ77. 0 = uncompressed, 1 = fixed huffman tree, 1360 2 = dynamic huffman tree (best compression). Should be 2 for proper 1361 compression. 1362 *) use_lz77: whether or not to use LZ77 for compressed block types. Should be 1363 true for proper compression. 1364 *) windowsize: the window size used by the LZ77 encoder (1 - 32768). Has value 1365 2048 by default, but can be set to 32768 for better, but slow, compression. 1366 *) force_palette: if colortype is 2 or 6, you can make the encoder write a PLTE 1367 chunk if force_palette is true. This can used as suggested palette to convert 1368 to by viewers that don't support more than 256 colors (if those still exist) 1369 *) add_id: add text chunk "Encoder: LodePNG <version>" to the image. 1370 *) text_compression: default 1. If 1, it'll store texts as zTXt instead of tEXt chunks. 1371 zTXt chunks use zlib compression on the text. This gives a smaller result on 1372 large texts but a larger result on small texts (such as a single program name). 1373 It's all tEXt or all zTXt though, there's no separate setting per text yet. 1374 1375 1376 6. color conversions 1377 -------------------- 1378 1379 An important thing to note about LodePNG, is that the color type of the PNG, and 1380 the color type of the raw image, are completely independent. By default, when 1381 you decode a PNG, you get the result as a raw image in the color type you want, 1382 no matter whether the PNG was encoded with a palette, grayscale or RGBA color. 1383 And if you encode an image, by default LodePNG will automatically choose the PNG 1384 color type that gives good compression based on the values of colors and amount 1385 of colors in the image. It can be configured to let you control it instead as 1386 well, though. 1387 1388 To be able to do this, LodePNG does conversions from one color mode to another. 1389 It can convert from almost any color type to any other color type, except the 1390 following conversions: RGB to grayscale is not supported, and converting to a 1391 palette when the palette doesn't have a required color is not supported. This is 1392 not supported on purpose: this is information loss which requires a color 1393 reduction algorithm that is beyond the scope of a PNG encoder (yes, RGB to gray 1394 is easy, but there are multiple ways if you want to give some channels more 1395 weight). 1396 1397 By default, when decoding, you get the raw image in 32-bit RGBA or 24-bit RGB 1398 color, no matter what color type the PNG has. And by default when encoding, 1399 LodePNG automatically picks the best color model for the output PNG, and expects 1400 the input image to be 32-bit RGBA or 24-bit RGB. So, unless you want to control 1401 the color format of the images yourself, you can skip this chapter. 1402 1403 6.1. PNG color types 1404 -------------------- 1405 1406 A PNG image can have many color types, ranging from 1-bit color to 64-bit color, 1407 as well as palettized color modes. After the zlib decompression and unfiltering 1408 in the PNG image is done, the raw pixel data will have that color type and thus 1409 a certain amount of bits per pixel. If you want the output raw image after 1410 decoding to have another color type, a conversion is done by LodePNG. 1411 1412 The PNG specification gives the following color types: 1413 1414 0: grayscale, bit depths 1, 2, 4, 8, 16 1415 2: RGB, bit depths 8 and 16 1416 3: palette, bit depths 1, 2, 4 and 8 1417 4: grayscale with alpha, bit depths 8 and 16 1418 6: RGBA, bit depths 8 and 16 1419 1420 Bit depth is the amount of bits per pixel per color channel. So the total amount 1421 of bits per pixel is: amount of channels * bitdepth. 1422 1423 6.2. color conversions 1424 ---------------------- 1425 1426 As explained in the sections about the encoder and decoder, you can specify 1427 color types and bit depths in info_png and info_raw to change the default 1428 behaviour. 1429 1430 If, when decoding, you want the raw image to be something else than the default, 1431 you need to set the color type and bit depth you want in the LodePNGColorMode, 1432 or the parameters colortype and bitdepth of the simple decoding function. 1433 1434 If, when encoding, you use another color type than the default in the raw input 1435 image, you need to specify its color type and bit depth in the LodePNGColorMode 1436 of the raw image, or use the parameters colortype and bitdepth of the simple 1437 encoding function. 1438 1439 If, when encoding, you don't want LodePNG to choose the output PNG color type 1440 but control it yourself, you need to set auto_convert in the encoder settings 1441 to false, and specify the color type you want in the LodePNGInfo of the 1442 encoder (including palette: it can generate a palette if auto_convert is true, 1443 otherwise not). 1444 1445 If the input and output color type differ (whether user chosen or auto chosen), 1446 LodePNG will do a color conversion, which follows the rules below, and may 1447 sometimes result in an error. 1448 1449 To avoid some confusion: 1450 -the decoder converts from PNG to raw image 1451 -the encoder converts from raw image to PNG 1452 -the colortype and bitdepth in LodePNGColorMode info_raw, are those of the raw image 1453 -the colortype and bitdepth in the color field of LodePNGInfo info_png, are those of the PNG 1454 -when encoding, the color type in LodePNGInfo is ignored if auto_convert 1455 is enabled, it is automatically generated instead 1456 -when decoding, the color type in LodePNGInfo is set by the decoder to that of the original 1457 PNG image, but it can be ignored since the raw image has the color type you requested instead 1458 -if the color type of the LodePNGColorMode and PNG image aren't the same, a conversion 1459 between the color types is done if the color types are supported. If it is not 1460 supported, an error is returned. If the types are the same, no conversion is done. 1461 -even though some conversions aren't supported, LodePNG supports loading PNGs from any 1462 colortype and saving PNGs to any colortype, sometimes it just requires preparing 1463 the raw image correctly before encoding. 1464 -both encoder and decoder use the same color converter. 1465 1466 The function lodepng_convert does the color conversion. It is available in the 1467 interface but normally isn't needed since the encoder and decoder already call 1468 it. 1469 1470 Non supported color conversions: 1471 -color to grayscale when non-gray pixels are present: no error is thrown, but 1472 the result will look ugly because only the red channel is taken (it assumes all 1473 three channels are the same in this case so ignores green and blue). The reason 1474 no error is given is to allow converting from three-channel grayscale images to 1475 one-channel even if there are numerical imprecisions. 1476 -anything to palette when the palette does not have an exact match for a from-color 1477 in it: in this case an error is thrown 1478 1479 Supported color conversions: 1480 -anything to 8-bit RGB, 8-bit RGBA, 16-bit RGB, 16-bit RGBA 1481 -any gray or gray+alpha, to gray or gray+alpha 1482 -anything to a palette, as long as the palette has the requested colors in it 1483 -removing alpha channel 1484 -higher to smaller bitdepth, and vice versa 1485 1486 If you want no color conversion to be done (e.g. for speed or control): 1487 -In the encoder, you can make it save a PNG with any color type by giving the 1488 raw color mode and LodePNGInfo the same color mode, and setting auto_convert to 1489 false. 1490 -In the decoder, you can make it store the pixel data in the same color type 1491 as the PNG has, by setting the color_convert setting to false. Settings in 1492 info_raw are then ignored. 1493 1494 6.3. padding bits 1495 ----------------- 1496 1497 In the PNG file format, if a less than 8-bit per pixel color type is used and the scanlines 1498 have a bit amount that isn't a multiple of 8, then padding bits are used so that each 1499 scanline starts at a fresh byte. But that is NOT true for the LodePNG raw input and output. 1500 The raw input image you give to the encoder, and the raw output image you get from the decoder 1501 will NOT have these padding bits, e.g. in the case of a 1-bit image with a width 1502 of 7 pixels, the first pixel of the second scanline will the 8th bit of the first byte, 1503 not the first bit of a new byte. 1504 1505 6.4. A note about 16-bits per channel and endianness 1506 ---------------------------------------------------- 1507 1508 LodePNG uses unsigned char arrays for 16-bit per channel colors too, just like 1509 for any other color format. The 16-bit values are stored in big endian (most 1510 significant byte first) in these arrays. This is the opposite order of the 1511 little endian used by x86 CPU's. 1512 1513 LodePNG always uses big endian because the PNG file format does so internally. 1514 Conversions to other formats than PNG uses internally are not supported by 1515 LodePNG on purpose, there are myriads of formats, including endianness of 16-bit 1516 colors, the order in which you store R, G, B and A, and so on. Supporting and 1517 converting to/from all that is outside the scope of LodePNG. 1518 1519 This may mean that, depending on your use case, you may want to convert the big 1520 endian output of LodePNG to little endian with a for loop. This is certainly not 1521 always needed, many applications and libraries support big endian 16-bit colors 1522 anyway, but it means you cannot simply cast the unsigned char* buffer to an 1523 unsigned short* buffer on x86 CPUs. 1524 1525 1526 7. error values 1527 --------------- 1528 1529 All functions in LodePNG that return an error code, return 0 if everything went 1530 OK, or a non-zero code if there was an error. 1531 1532 The meaning of the LodePNG error values can be retrieved with the function 1533 lodepng_error_text: given the numerical error code, it returns a description 1534 of the error in English as a string. 1535 1536 Check the implementation of lodepng_error_text to see the meaning of each code. 1537 1538 It is not recommended to use the numerical values to programmatically make 1539 different decisions based on error types as the numbers are not guaranteed to 1540 stay backwards compatible. They are for human consumption only. Programmatically 1541 only 0 or non-0 matter. 1542 1543 1544 8. chunks and PNG editing 1545 ------------------------- 1546 1547 If you want to add extra chunks to a PNG you encode, or use LodePNG for a PNG 1548 editor that should follow the rules about handling of unknown chunks, or if your 1549 program is able to read other types of chunks than the ones handled by LodePNG, 1550 then that's possible with the chunk functions of LodePNG. 1551 1552 A PNG chunk has the following layout: 1553 1554 4 bytes length 1555 4 bytes type name 1556 length bytes data 1557 4 bytes CRC 1558 1559 8.1. iterating through chunks 1560 ----------------------------- 1561 1562 If you have a buffer containing the PNG image data, then the first chunk (the 1563 IHDR chunk) starts at byte number 8 of that buffer. The first 8 bytes are the 1564 signature of the PNG and are not part of a chunk. But if you start at byte 8 1565 then you have a chunk, and can check the following things of it. 1566 1567 NOTE: none of these functions check for memory buffer boundaries. To avoid 1568 exploits, always make sure the buffer contains all the data of the chunks. 1569 When using lodepng_chunk_next, make sure the returned value is within the 1570 allocated memory. 1571 1572 unsigned lodepng_chunk_length(const unsigned char* chunk): 1573 1574 Get the length of the chunk's data. The total chunk length is this length + 12. 1575 1576 void lodepng_chunk_type(char type[5], const unsigned char* chunk): 1577 unsigned char lodepng_chunk_type_equals(const unsigned char* chunk, const char* type): 1578 1579 Get the type of the chunk or compare if it's a certain type 1580 1581 unsigned char lodepng_chunk_critical(const unsigned char* chunk): 1582 unsigned char lodepng_chunk_private(const unsigned char* chunk): 1583 unsigned char lodepng_chunk_safetocopy(const unsigned char* chunk): 1584 1585 Check if the chunk is critical in the PNG standard (only IHDR, PLTE, IDAT and IEND are). 1586 Check if the chunk is private (public chunks are part of the standard, private ones not). 1587 Check if the chunk is safe to copy. If it's not, then, when modifying data in a critical 1588 chunk, unsafe to copy chunks of the old image may NOT be saved in the new one if your 1589 program doesn't handle that type of unknown chunk. 1590 1591 unsigned char* lodepng_chunk_data(unsigned char* chunk): 1592 const unsigned char* lodepng_chunk_data_const(const unsigned char* chunk): 1593 1594 Get a pointer to the start of the data of the chunk. 1595 1596 unsigned lodepng_chunk_check_crc(const unsigned char* chunk): 1597 void lodepng_chunk_generate_crc(unsigned char* chunk): 1598 1599 Check if the crc is correct or generate a correct one. 1600 1601 unsigned char* lodepng_chunk_next(unsigned char* chunk): 1602 const unsigned char* lodepng_chunk_next_const(const unsigned char* chunk): 1603 1604 Iterate to the next chunk. This works if you have a buffer with consecutive chunks. Note that these 1605 functions do no boundary checking of the allocated data whatsoever, so make sure there is enough 1606 data available in the buffer to be able to go to the next chunk. 1607 1608 unsigned lodepng_chunk_append(unsigned char** out, size_t* outsize, const unsigned char* chunk): 1609 unsigned lodepng_chunk_create(unsigned char** out, size_t* outsize, unsigned length, 1610 const char* type, const unsigned char* data): 1611 1612 These functions are used to create new chunks that are appended to the data in *out that has 1613 length *outsize. The append function appends an existing chunk to the new data. The create 1614 function creates a new chunk with the given parameters and appends it. Type is the 4-letter 1615 name of the chunk. 1616 1617 8.2. chunks in info_png 1618 ----------------------- 1619 1620 The LodePNGInfo struct contains fields with the unknown chunk in it. It has 3 1621 buffers (each with size) to contain 3 types of unknown chunks: 1622 the ones that come before the PLTE chunk, the ones that come between the PLTE 1623 and the IDAT chunks, and the ones that come after the IDAT chunks. 1624 It's necessary to make the distinction between these 3 cases because the PNG 1625 standard forces to keep the ordering of unknown chunks compared to the critical 1626 chunks, but does not force any other ordering rules. 1627 1628 info_png.unknown_chunks_data[0] is the chunks before PLTE 1629 info_png.unknown_chunks_data[1] is the chunks after PLTE, before IDAT 1630 info_png.unknown_chunks_data[2] is the chunks after IDAT 1631 1632 The chunks in these 3 buffers can be iterated through and read by using the same 1633 way described in the previous subchapter. 1634 1635 When using the decoder to decode a PNG, you can make it store all unknown chunks 1636 if you set the option settings.remember_unknown_chunks to 1. By default, this 1637 option is off (0). 1638 1639 The encoder will always encode unknown chunks that are stored in the info_png. 1640 If you need it to add a particular chunk that isn't known by LodePNG, you can 1641 use lodepng_chunk_append or lodepng_chunk_create to the chunk data in 1642 info_png.unknown_chunks_data[x]. 1643 1644 Chunks that are known by LodePNG should not be added in that way. E.g. to make 1645 LodePNG add a bKGD chunk, set background_defined to true and add the correct 1646 parameters there instead. 1647 1648 1649 9. compiler support 1650 ------------------- 1651 1652 No libraries other than the current standard C library are needed to compile 1653 LodePNG. For the C++ version, only the standard C++ library is needed on top. 1654 Add the files lodepng.c(pp) and lodepng.h to your project, include 1655 lodepng.h where needed, and your program can read/write PNG files. 1656 1657 It is compatible with C90 and up, and C++03 and up. 1658 1659 If performance is important, use optimization when compiling! For both the 1660 encoder and decoder, this makes a large difference. 1661 1662 Make sure that LodePNG is compiled with the same compiler of the same version 1663 and with the same settings as the rest of the program, or the interfaces with 1664 std::vectors and std::strings in C++ can be incompatible. 1665 1666 CHAR_BITS must be 8 or higher, because LodePNG uses unsigned chars for octets. 1667 1668 *) gcc and g++ 1669 1670 LodePNG is developed in gcc so this compiler is natively supported. It gives no 1671 warnings with compiler options "-Wall -Wextra -pedantic -ansi", with gcc and g++ 1672 version 4.7.1 on Linux, 32-bit and 64-bit. 1673 1674 *) Clang 1675 1676 Fully supported and warning-free. 1677 1678 *) Mingw 1679 1680 The Mingw compiler (a port of gcc for Windows) should be fully supported by 1681 LodePNG. 1682 1683 *) Visual Studio and Visual C++ Express Edition 1684 1685 LodePNG should be warning-free with warning level W4. Two warnings were disabled 1686 with pragmas though: warning 4244 about implicit conversions, and warning 4996 1687 where it wants to use a non-standard function fopen_s instead of the standard C 1688 fopen. 1689 1690 Visual Studio may want "stdafx.h" files to be included in each source file and 1691 give an error "unexpected end of file while looking for precompiled header". 1692 This is not standard C++ and will not be added to the stock LodePNG. You can 1693 disable it for lodepng.cpp only by right clicking it, Properties, C/C++, 1694 Precompiled Headers, and set it to Not Using Precompiled Headers there. 1695 1696 NOTE: Modern versions of VS should be fully supported, but old versions, e.g. 1697 VS6, are not guaranteed to work. 1698 1699 *) Compilers on Macintosh 1700 1701 LodePNG has been reported to work both with gcc and LLVM for Macintosh, both for 1702 C and C++. 1703 1704 *) Other Compilers 1705 1706 If you encounter problems on any compilers, feel free to let me know and I may 1707 try to fix it if the compiler is modern and standards compliant. 1708 1709 1710 10. examples 1711 ------------ 1712 1713 This decoder example shows the most basic usage of LodePNG. More complex 1714 examples can be found on the LodePNG website. 1715 1716 10.1. decoder C++ example 1717 ------------------------- 1718 1719 #include "lodepng.h" 1720 #include <iostream> 1721 1722 int main(int argc, char *argv[]) { 1723 const char* filename = argc > 1 ? argv[1] : "test.png"; 1724 1725 //load and decode 1726 std::vector<unsigned char> image; 1727 unsigned width, height; 1728 unsigned error = lodepng::decode(image, width, height, filename); 1729 1730 //if there's an error, display it 1731 if(error) std::cout << "decoder error " << error << ": " << lodepng_error_text(error) << std::endl; 1732 1733 //the pixels are now in the vector "image", 4 bytes per pixel, ordered RGBARGBA..., use it as texture, draw it, ... 1734 } 1735 1736 10.2. decoder C example 1737 ----------------------- 1738 1739 #include "lodepng.h" 1740 1741 int main(int argc, char *argv[]) { 1742 unsigned error; 1743 unsigned char* image; 1744 size_t width, height; 1745 const char* filename = argc > 1 ? argv[1] : "test.png"; 1746 1747 error = lodepng_decode32_file(&image, &width, &height, filename); 1748 1749 if(error) printf("decoder error %u: %s\n", error, lodepng_error_text(error)); 1750 1751 / * use image here * / 1752 1753 free(image); 1754 return 0; 1755 } 1756 1757 11. state settings reference 1758 ---------------------------- 1759 1760 A quick reference of some settings to set on the LodePNGState 1761 1762 For decoding: 1763 1764 state.decoder.zlibsettings.ignore_adler32: ignore ADLER32 checksums 1765 state.decoder.zlibsettings.custom_...: use custom inflate function 1766 state.decoder.ignore_crc: ignore CRC checksums 1767 state.decoder.ignore_critical: ignore unknown critical chunks 1768 state.decoder.ignore_end: ignore missing IEND chunk. May fail if this corruption causes other errors 1769 state.decoder.color_convert: convert internal PNG color to chosen one 1770 state.decoder.read_text_chunks: whether to read in text metadata chunks 1771 state.decoder.remember_unknown_chunks: whether to read in unknown chunks 1772 state.info_raw.colortype: desired color type for decoded image 1773 state.info_raw.bitdepth: desired bit depth for decoded image 1774 state.info_raw....: more color settings, see struct LodePNGColorMode 1775 state.info_png....: no settings for decoder but ouput, see struct LodePNGInfo 1776 1777 For encoding: 1778 1779 state.encoder.zlibsettings.btype: disable compression by setting it to 0 1780 state.encoder.zlibsettings.use_lz77: use LZ77 in compression 1781 state.encoder.zlibsettings.windowsize: tweak LZ77 windowsize 1782 state.encoder.zlibsettings.minmatch: tweak min LZ77 length to match 1783 state.encoder.zlibsettings.nicematch: tweak LZ77 match where to stop searching 1784 state.encoder.zlibsettings.lazymatching: try one more LZ77 matching 1785 state.encoder.zlibsettings.custom_...: use custom deflate function 1786 state.encoder.auto_convert: choose optimal PNG color type, if 0 uses info_png 1787 state.encoder.filter_palette_zero: PNG filter strategy for palette 1788 state.encoder.filter_strategy: PNG filter strategy to encode with 1789 state.encoder.force_palette: add palette even if not encoding to one 1790 state.encoder.add_id: add LodePNG identifier and version as a text chunk 1791 state.encoder.text_compression: use compressed text chunks for metadata 1792 state.info_raw.colortype: color type of raw input image you provide 1793 state.info_raw.bitdepth: bit depth of raw input image you provide 1794 state.info_raw: more color settings, see struct LodePNGColorMode 1795 state.info_png.color.colortype: desired color type if auto_convert is false 1796 state.info_png.color.bitdepth: desired bit depth if auto_convert is false 1797 state.info_png.color....: more color settings, see struct LodePNGColorMode 1798 state.info_png....: more PNG related settings, see struct LodePNGInfo 1799 1800 1801 12. changes 1802 ----------- 1803 1804 The version number of LodePNG is the date of the change given in the format 1805 yyyymmdd. 1806 1807 Some changes aren't backwards compatible. Those are indicated with a (!) 1808 symbol. 1809 1810 Not all changes are listed here, the commit history in github lists more: 1811 https://github.com/lvandeve/lodepng 1812 1813 *) 17 okt 2020: prevent decoding too large text/icc chunks by default. 1814 *) 06 mar 2020: simplified some of the dynamic memory allocations. 1815 *) 12 jan 2020: (!) added 'end' argument to lodepng_chunk_next to allow correct 1816 overflow checks. 1817 *) 14 aug 2019: around 25% faster decoding thanks to huffman lookup tables. 1818 *) 15 jun 2019: (!) auto_choose_color API changed (for bugfix: don't use palette 1819 if gray ICC profile) and non-ICC LodePNGColorProfile renamed to 1820 LodePNGColorStats. 1821 *) 30 dec 2018: code style changes only: removed newlines before opening braces. 1822 *) 10 sep 2018: added way to inspect metadata chunks without full decoding. 1823 *) 19 aug 2018: (!) fixed color mode bKGD is encoded with and made it use 1824 palette index in case of palette. 1825 *) 10 aug 2018: (!) added support for gAMA, cHRM, sRGB and iCCP chunks. This 1826 change is backwards compatible unless you relied on unknown_chunks for those. 1827 *) 11 jun 2018: less restrictive check for pixel size integer overflow 1828 *) 14 jan 2018: allow optionally ignoring a few more recoverable errors 1829 *) 17 sep 2017: fix memory leak for some encoder input error cases 1830 *) 27 nov 2016: grey+alpha auto color model detection bugfix 1831 *) 18 apr 2016: Changed qsort to custom stable sort (for platforms w/o qsort). 1832 *) 09 apr 2016: Fixed colorkey usage detection, and better file loading (within 1833 the limits of pure C90). 1834 *) 08 dec 2015: Made load_file function return error if file can't be opened. 1835 *) 24 okt 2015: Bugfix with decoding to palette output. 1836 *) 18 apr 2015: Boundary PM instead of just package-merge for faster encoding. 1837 *) 24 aug 2014: Moved to github 1838 *) 23 aug 2014: Reduced needless memory usage of decoder. 1839 *) 28 jun 2014: Removed fix_png setting, always support palette OOB for 1840 simplicity. Made ColorProfile public. 1841 *) 09 jun 2014: Faster encoder by fixing hash bug and more zeros optimization. 1842 *) 22 dec 2013: Power of two windowsize required for optimization. 1843 *) 15 apr 2013: Fixed bug with LAC_ALPHA and color key. 1844 *) 25 mar 2013: Added an optional feature to ignore some PNG errors (fix_png). 1845 *) 11 mar 2013: (!) Bugfix with custom free. Changed from "my" to "lodepng_" 1846 prefix for the custom allocators and made it possible with a new #define to 1847 use custom ones in your project without needing to change lodepng's code. 1848 *) 28 jan 2013: Bugfix with color key. 1849 *) 27 okt 2012: Tweaks in text chunk keyword length error handling. 1850 *) 8 okt 2012: (!) Added new filter strategy (entropy) and new auto color mode. 1851 (no palette). Better deflate tree encoding. New compression tweak settings. 1852 Faster color conversions while decoding. Some internal cleanups. 1853 *) 23 sep 2012: Reduced warnings in Visual Studio a little bit. 1854 *) 1 sep 2012: (!) Removed #define's for giving custom (de)compression functions 1855 and made it work with function pointers instead. 1856 *) 23 jun 2012: Added more filter strategies. Made it easier to use custom alloc 1857 and free functions and toggle #defines from compiler flags. Small fixes. 1858 *) 6 may 2012: (!) Made plugging in custom zlib/deflate functions more flexible. 1859 *) 22 apr 2012: (!) Made interface more consistent, renaming a lot. Removed 1860 redundant C++ codec classes. Reduced amount of structs. Everything changed, 1861 but it is cleaner now imho and functionality remains the same. Also fixed 1862 several bugs and shrunk the implementation code. Made new samples. 1863 *) 6 nov 2011: (!) By default, the encoder now automatically chooses the best 1864 PNG color model and bit depth, based on the amount and type of colors of the 1865 raw image. For this, autoLeaveOutAlphaChannel replaced by auto_choose_color. 1866 *) 9 okt 2011: simpler hash chain implementation for the encoder. 1867 *) 8 sep 2011: lz77 encoder lazy matching instead of greedy matching. 1868 *) 23 aug 2011: tweaked the zlib compression parameters after benchmarking. 1869 A bug with the PNG filtertype heuristic was fixed, so that it chooses much 1870 better ones (it's quite significant). A setting to do an experimental, slow, 1871 brute force search for PNG filter types is added. 1872 *) 17 aug 2011: (!) changed some C zlib related function names. 1873 *) 16 aug 2011: made the code less wide (max 120 characters per line). 1874 *) 17 apr 2011: code cleanup. Bugfixes. Convert low to 16-bit per sample colors. 1875 *) 21 feb 2011: fixed compiling for C90. Fixed compiling with sections disabled. 1876 *) 11 dec 2010: encoding is made faster, based on suggestion by Peter Eastman 1877 to optimize long sequences of zeros. 1878 *) 13 nov 2010: added LodePNG_InfoColor_hasPaletteAlpha and 1879 LodePNG_InfoColor_canHaveAlpha functions for convenience. 1880 *) 7 nov 2010: added LodePNG_error_text function to get error code description. 1881 *) 30 okt 2010: made decoding slightly faster 1882 *) 26 okt 2010: (!) changed some C function and struct names (more consistent). 1883 Reorganized the documentation and the declaration order in the header. 1884 *) 08 aug 2010: only changed some comments and external samples. 1885 *) 05 jul 2010: fixed bug thanks to warnings in the new gcc version. 1886 *) 14 mar 2010: fixed bug where too much memory was allocated for char buffers. 1887 *) 02 sep 2008: fixed bug where it could create empty tree that linux apps could 1888 read by ignoring the problem but windows apps couldn't. 1889 *) 06 jun 2008: added more error checks for out of memory cases. 1890 *) 26 apr 2008: added a few more checks here and there to ensure more safety. 1891 *) 06 mar 2008: crash with encoding of strings fixed 1892 *) 02 feb 2008: support for international text chunks added (iTXt) 1893 *) 23 jan 2008: small cleanups, and #defines to divide code in sections 1894 *) 20 jan 2008: support for unknown chunks allowing using LodePNG for an editor. 1895 *) 18 jan 2008: support for tIME and pHYs chunks added to encoder and decoder. 1896 *) 17 jan 2008: ability to encode and decode compressed zTXt chunks added 1897 Also various fixes, such as in the deflate and the padding bits code. 1898 *) 13 jan 2008: Added ability to encode Adam7-interlaced images. Improved 1899 filtering code of encoder. 1900 *) 07 jan 2008: (!) changed LodePNG to use ISO C90 instead of C++. A 1901 C++ wrapper around this provides an interface almost identical to before. 1902 Having LodePNG be pure ISO C90 makes it more portable. The C and C++ code 1903 are together in these files but it works both for C and C++ compilers. 1904 *) 29 dec 2007: (!) changed most integer types to unsigned int + other tweaks 1905 *) 30 aug 2007: bug fixed which makes this Borland C++ compatible 1906 *) 09 aug 2007: some VS2005 warnings removed again 1907 *) 21 jul 2007: deflate code placed in new namespace separate from zlib code 1908 *) 08 jun 2007: fixed bug with 2- and 4-bit color, and small interlaced images 1909 *) 04 jun 2007: improved support for Visual Studio 2005: crash with accessing 1910 invalid std::vector element [0] fixed, and level 3 and 4 warnings removed 1911 *) 02 jun 2007: made the encoder add a tag with version by default 1912 *) 27 may 2007: zlib and png code separated (but still in the same file), 1913 simple encoder/decoder functions added for more simple usage cases 1914 *) 19 may 2007: minor fixes, some code cleaning, new error added (error 69), 1915 moved some examples from here to lodepng_examples.cpp 1916 *) 12 may 2007: palette decoding bug fixed 1917 *) 24 apr 2007: changed the license from BSD to the zlib license 1918 *) 11 mar 2007: very simple addition: ability to encode bKGD chunks. 1919 *) 04 mar 2007: (!) tEXt chunk related fixes, and support for encoding 1920 palettized PNG images. Plus little interface change with palette and texts. 1921 *) 03 mar 2007: Made it encode dynamic Huffman shorter with repeat codes. 1922 Fixed a bug where the end code of a block had length 0 in the Huffman tree. 1923 *) 26 feb 2007: Huffman compression with dynamic trees (BTYPE 2) now implemented 1924 and supported by the encoder, resulting in smaller PNGs at the output. 1925 *) 27 jan 2007: Made the Adler-32 test faster so that a timewaste is gone. 1926 *) 24 jan 2007: gave encoder an error interface. Added color conversion from any 1927 greyscale type to 8-bit greyscale with or without alpha. 1928 *) 21 jan 2007: (!) Totally changed the interface. It allows more color types 1929 to convert to and is more uniform. See the manual for how it works now. 1930 *) 07 jan 2007: Some cleanup & fixes, and a few changes over the last days: 1931 encode/decode custom tEXt chunks, separate classes for zlib & deflate, and 1932 at last made the decoder give errors for incorrect Adler32 or Crc. 1933 *) 01 jan 2007: Fixed bug with encoding PNGs with less than 8 bits per channel. 1934 *) 29 dec 2006: Added support for encoding images without alpha channel, and 1935 cleaned out code as well as making certain parts faster. 1936 *) 28 dec 2006: Added "Settings" to the encoder. 1937 *) 26 dec 2006: The encoder now does LZ77 encoding and produces much smaller files now. 1938 Removed some code duplication in the decoder. Fixed little bug in an example. 1939 *) 09 dec 2006: (!) Placed output parameters of public functions as first parameter. 1940 Fixed a bug of the decoder with 16-bit per color. 1941 *) 15 okt 2006: Changed documentation structure 1942 *) 09 okt 2006: Encoder class added. It encodes a valid PNG image from the 1943 given image buffer, however for now it's not compressed. 1944 *) 08 sep 2006: (!) Changed to interface with a Decoder class 1945 *) 30 jul 2006: (!) LodePNG_InfoPng , width and height are now retrieved in different 1946 way. Renamed decodePNG to decodePNGGeneric. 1947 *) 29 jul 2006: (!) Changed the interface: image info is now returned as a 1948 struct of type LodePNG::LodePNG_Info, instead of a vector, which was a bit clumsy. 1949 *) 28 jul 2006: Cleaned the code and added new error checks. 1950 Corrected terminology "deflate" into "inflate". 1951 *) 23 jun 2006: Added SDL example in the documentation in the header, this 1952 example allows easy debugging by displaying the PNG and its transparency. 1953 *) 22 jun 2006: (!) Changed way to obtain error value. Added 1954 loadFile function for convenience. Made decodePNG32 faster. 1955 *) 21 jun 2006: (!) Changed type of info vector to unsigned. 1956 Changed position of palette in info vector. Fixed an important bug that 1957 happened on PNGs with an uncompressed block. 1958 *) 16 jun 2006: Internally changed unsigned into unsigned where 1959 needed, and performed some optimizations. 1960 *) 07 jun 2006: (!) Renamed functions to decodePNG and placed them 1961 in LodePNG namespace. Changed the order of the parameters. Rewrote the 1962 documentation in the header. Renamed files to lodepng.cpp and lodepng.h 1963 *) 22 apr 2006: Optimized and improved some code 1964 *) 07 sep 2005: (!) Changed to std::vector interface 1965 *) 12 aug 2005: Initial release (C++, decoder only) 1966 1967 1968 13. contact information 1969 ----------------------- 1970 1971 Feel free to contact me with suggestions, problems, comments, ... concerning 1972 LodePNG. If you encounter a PNG image that doesn't work properly with this 1973 decoder, feel free to send it and I'll use it to find and fix the problem. 1974 1975 My email address is (puzzle the account and domain together with an @ symbol): 1976 Domain: gmail dot com. 1977 Account: lode dot vandevenne. 1978 1979 1980 Copyright (c) 2005-2020 Lode Vandevenne 1981 */ 1982
