1 /* 2 LodePNG version 20191109 3 4 Copyright (c) 2005-2019 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 extern const char* LODEPNG_VERSION_STRING; 32 33 /* 34 The following #defines are used to create code sections. They can be disabled 35 to disable code sections, which can give faster compile time and smaller binary. 36 The "NO_COMPILE" defines are designed to be used to pass as defines to the 37 compiler command to disable them without modifying this header, e.g. 38 -DLODEPNG_NO_COMPILE_ZLIB for gcc. 39 In addition to those below, you can also define LODEPNG_NO_COMPILE_CRC to 40 allow implementing a custom lodepng_crc32. 41 */ 42 /*deflate & zlib. If disabled, you must specify alternative zlib functions in 43 the custom_zlib field of the compress and decompress settings*/ 44 #ifndef LODEPNG_NO_COMPILE_ZLIB 45 #define LODEPNG_COMPILE_ZLIB 46 #endif 47 48 /*png encoder and png decoder*/ 49 #ifndef LODEPNG_NO_COMPILE_PNG 50 #define LODEPNG_COMPILE_PNG 51 #endif 52 53 /*deflate&zlib decoder and png decoder*/ 54 #ifndef LODEPNG_NO_COMPILE_DECODER 55 #define LODEPNG_COMPILE_DECODER 56 #endif 57 58 /*deflate&zlib encoder and png encoder*/ 59 #ifndef LODEPNG_NO_COMPILE_ENCODER 60 #define LODEPNG_COMPILE_ENCODER 61 #endif 62 63 /*the optional built in harddisk file loading and saving functions*/ 64 #ifndef LODEPNG_NO_COMPILE_DISK 65 #define LODEPNG_COMPILE_DISK 66 #endif 67 68 /*support for chunks other than IHDR, IDAT, PLTE, tRNS, IEND: ancillary and unknown chunks*/ 69 #ifndef LODEPNG_NO_COMPILE_ANCILLARY_CHUNKS 70 #define LODEPNG_COMPILE_ANCILLARY_CHUNKS 71 #endif 72 73 /*ability to convert error numerical codes to English text string*/ 74 #ifndef LODEPNG_NO_COMPILE_ERROR_TEXT 75 #define LODEPNG_COMPILE_ERROR_TEXT 76 #endif 77 78 /*Compile the default allocators (C's free, malloc and realloc). If you disable this, 79 you can define the functions lodepng_free, lodepng_malloc and lodepng_realloc in your 80 source files with custom allocators.*/ 81 #ifndef LODEPNG_NO_COMPILE_ALLOCATORS 82 #define LODEPNG_COMPILE_ALLOCATORS 83 #endif 84 85 /*compile the C++ version (you can disable the C++ wrapper here even when compiling for C++)*/ 86 #ifdef __cplusplus 87 #ifndef LODEPNG_NO_COMPILE_CPP 88 #define LODEPNG_COMPILE_CPP 89 #endif 90 #endif 91 92 #ifdef LODEPNG_COMPILE_CPP 93 #include <vector> 94 #include <string> 95 #endif /*LODEPNG_COMPILE_CPP*/ 96 97 #ifdef LODEPNG_COMPILE_PNG 98 /*The PNG color types (also used for raw image).*/ 99 typedef enum LodePNGColorType { 100 LCT_GREY = 0, /*grayscale: 1,2,4,8,16 bit*/ 101 LCT_RGB = 2, /*RGB: 8,16 bit*/ 102 LCT_PALETTE = 3, /*palette: 1,2,4,8 bit*/ 103 LCT_GREY_ALPHA = 4, /*grayscale with alpha: 8,16 bit*/ 104 LCT_RGBA = 6, /*RGB with alpha: 8,16 bit*/ 105 /*LCT_MAX_OCTET_VALUE lets the compiler allow this enum to represent any invalid 106 byte value from 0 to 255 that could be present in an invalid PNG file header. Do 107 not use, compare with or set the name LCT_MAX_OCTET_VALUE, instead either use 108 the valid color type names above, or numeric values like 1 or 7 when checking for 109 particular disallowed color type byte values, or cast to integer to print it.*/ 110 LCT_MAX_OCTET_VALUE = 255 111 } LodePNGColorType; 112 113 #ifdef LODEPNG_COMPILE_DECODER 114 /* 115 Converts PNG data in memory to raw pixel data. 116 out: Output parameter. Pointer to buffer that will contain the raw pixel data. 117 After decoding, its size is w * h * (bytes per pixel) bytes larger than 118 initially. Bytes per pixel depends on colortype and bitdepth. 119 Must be freed after usage with free(*out). 120 Note: for 16-bit per channel colors, uses big endian format like PNG does. 121 w: Output parameter. Pointer to width of pixel data. 122 h: Output parameter. Pointer to height of pixel data. 123 in: Memory buffer with the PNG file. 124 insize: size of the in buffer. 125 colortype: the desired color type for the raw output image. See explanation on PNG color types. 126 bitdepth: the desired bit depth for the raw output image. See explanation on PNG color types. 127 Return value: LodePNG error code (0 means no error). 128 */ 129 unsigned lodepng_decode_memory(unsigned char** out, unsigned* w, unsigned* h, 130 const unsigned char* in, size_t insize, 131 LodePNGColorType colortype, unsigned bitdepth); 132 133 /*Same as lodepng_decode_memory, but always decodes to 32-bit RGBA raw image*/ 134 unsigned lodepng_decode32(unsigned char** out, unsigned* w, unsigned* h, 135 const unsigned char* in, size_t insize); 136 137 /*Same as lodepng_decode_memory, but always decodes to 24-bit RGB raw image*/ 138 unsigned lodepng_decode24(unsigned char** out, unsigned* w, unsigned* h, 139 const unsigned char* in, size_t insize); 140 141 #ifdef LODEPNG_COMPILE_DISK 142 /* 143 Load PNG from disk, from file with given name. 144 Same as the other decode functions, but instead takes a filename as input. 145 */ 146 unsigned lodepng_decode_file(unsigned char** out, unsigned* w, unsigned* h, 147 const char* filename, 148 LodePNGColorType colortype, unsigned bitdepth); 149 150 /*Same as lodepng_decode_file, but always decodes to 32-bit RGBA raw image.*/ 151 unsigned lodepng_decode32_file(unsigned char** out, unsigned* w, unsigned* h, 152 const char* filename); 153 154 /*Same as lodepng_decode_file, but always decodes to 24-bit RGB raw image.*/ 155 unsigned lodepng_decode24_file(unsigned char** out, unsigned* w, unsigned* h, 156 const char* filename); 157 #endif /*LODEPNG_COMPILE_DISK*/ 158 #endif /*LODEPNG_COMPILE_DECODER*/ 159 160 161 #ifdef LODEPNG_COMPILE_ENCODER 162 /* 163 Converts raw pixel data into a PNG image in memory. The colortype and bitdepth 164 of the output PNG image cannot be chosen, they are automatically determined 165 by the colortype, bitdepth and content of the input pixel data. 166 Note: for 16-bit per channel colors, needs big endian format like PNG does. 167 out: Output parameter. Pointer to buffer that will contain the PNG image data. 168 Must be freed after usage with free(*out). 169 outsize: Output parameter. Pointer to the size in bytes of the out buffer. 170 image: The raw pixel data to encode. The size of this buffer should be 171 w * h * (bytes per pixel), bytes per pixel depends on colortype and bitdepth. 172 w: width of the raw pixel data in pixels. 173 h: height of the raw pixel data in pixels. 174 colortype: the color type of the raw input image. See explanation on PNG color types. 175 bitdepth: the bit depth of the raw input image. See explanation on PNG color types. 176 Return value: LodePNG error code (0 means no error). 177 */ 178 unsigned lodepng_encode_memory(unsigned char** out, size_t* outsize, 179 const unsigned char* image, unsigned w, unsigned h, 180 LodePNGColorType colortype, unsigned bitdepth); 181 182 /*Same as lodepng_encode_memory, but always encodes from 32-bit RGBA raw image.*/ 183 unsigned lodepng_encode32(unsigned char** out, size_t* outsize, 184 const unsigned char* image, unsigned w, unsigned h); 185 186 /*Same as lodepng_encode_memory, but always encodes from 24-bit RGB raw image.*/ 187 unsigned lodepng_encode24(unsigned char** out, size_t* outsize, 188 const unsigned char* image, unsigned w, unsigned h); 189 190 #ifdef LODEPNG_COMPILE_DISK 191 /* 192 Converts raw pixel data into a PNG file on disk. 193 Same as the other encode functions, but instead takes a filename as output. 194 NOTE: This overwrites existing files without warning! 195 */ 196 unsigned lodepng_encode_file(const char* filename, 197 const unsigned char* image, unsigned w, unsigned h, 198 LodePNGColorType colortype, unsigned bitdepth); 199 200 /*Same as lodepng_encode_file, but always encodes from 32-bit RGBA raw image.*/ 201 unsigned lodepng_encode32_file(const char* filename, 202 const unsigned char* image, unsigned w, unsigned h); 203 204 /*Same as lodepng_encode_file, but always encodes from 24-bit RGB raw image.*/ 205 unsigned lodepng_encode24_file(const char* filename, 206 const unsigned char* image, unsigned w, unsigned h); 207 #endif /*LODEPNG_COMPILE_DISK*/ 208 #endif /*LODEPNG_COMPILE_ENCODER*/ 209 210 211 #ifdef LODEPNG_COMPILE_CPP 212 namespace lodepng { 213 #ifdef LODEPNG_COMPILE_DECODER 214 /*Same as lodepng_decode_memory, but decodes to an std::vector. The colortype 215 is the format to output the pixels to. Default is RGBA 8-bit per channel.*/ 216 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h, 217 const unsigned char* in, size_t insize, 218 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8); 219 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h, 220 const std::vector<unsigned char>& in, 221 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8); 222 #ifdef LODEPNG_COMPILE_DISK 223 /* 224 Converts PNG file from disk to raw pixel data in memory. 225 Same as the other decode functions, but instead takes a filename as input. 226 */ 227 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h, 228 const std::string& filename, 229 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8); 230 #endif /* LODEPNG_COMPILE_DISK */ 231 #endif /* LODEPNG_COMPILE_DECODER */ 232 233 #ifdef LODEPNG_COMPILE_ENCODER 234 /*Same as lodepng_encode_memory, but encodes to an std::vector. colortype 235 is that of the raw input data. The output PNG color type will be auto chosen.*/ 236 unsigned encode(std::vector<unsigned char>& out, 237 const unsigned char* in, unsigned w, unsigned h, 238 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8); 239 unsigned encode(std::vector<unsigned char>& out, 240 const std::vector<unsigned char>& in, unsigned w, unsigned h, 241 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8); 242 #ifdef LODEPNG_COMPILE_DISK 243 /* 244 Converts 32-bit RGBA raw pixel data into a PNG file on disk. 245 Same as the other encode functions, but instead takes a filename as output. 246 NOTE: This overwrites existing files without warning! 247 */ 248 unsigned encode(const std::string& filename, 249 const unsigned char* in, unsigned w, unsigned h, 250 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8); 251 unsigned encode(const std::string& filename, 252 const std::vector<unsigned char>& in, unsigned w, unsigned h, 253 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8); 254 #endif /* LODEPNG_COMPILE_DISK */ 255 #endif /* LODEPNG_COMPILE_ENCODER */ 256 } /* namespace lodepng */ 257 #endif /*LODEPNG_COMPILE_CPP*/ 258 #endif /*LODEPNG_COMPILE_PNG*/ 259 260 #ifdef LODEPNG_COMPILE_ERROR_TEXT 261 /*Returns an English description of the numerical error code.*/ 262 const char* lodepng_error_text(unsigned code); 263 #endif /*LODEPNG_COMPILE_ERROR_TEXT*/ 264 265 #ifdef LODEPNG_COMPILE_DECODER 266 /*Settings for zlib decompression*/ 267 typedef struct LodePNGDecompressSettings LodePNGDecompressSettings; 268 struct LodePNGDecompressSettings { 269 /* Check LodePNGDecoderSettings for more ignorable errors such as ignore_crc */ 270 unsigned ignore_adler32; /*if 1, continue and don't give an error message if the Adler32 checksum is corrupted*/ 271 unsigned ignore_nlen; /*ignore complement of len checksum in uncompressed blocks*/ 272 273 /*use custom zlib decoder instead of built in one (default: null)*/ 274 unsigned (*custom_zlib)(unsigned char**, size_t*, 275 const unsigned char*, size_t, 276 const LodePNGDecompressSettings*); 277 /*use custom deflate decoder instead of built in one (default: null) 278 if custom_zlib is not null, custom_inflate is ignored (the zlib format uses deflate)*/ 279 unsigned (*custom_inflate)(unsigned char**, size_t*, 280 const unsigned char*, size_t, 281 const LodePNGDecompressSettings*); 282 283 const void* custom_context; /*optional custom settings for custom functions*/ 284 }; 285 286 extern const LodePNGDecompressSettings lodepng_default_decompress_settings; 287 void lodepng_decompress_settings_init(LodePNGDecompressSettings* settings); 288 #endif /*LODEPNG_COMPILE_DECODER*/ 289 290 #ifdef LODEPNG_COMPILE_ENCODER 291 /* 292 Settings for zlib compression. Tweaking these settings tweaks the balance 293 between speed and compression ratio. 294 */ 295 typedef struct LodePNGCompressSettings LodePNGCompressSettings; 296 struct LodePNGCompressSettings /*deflate = compress*/ { 297 /*LZ77 related settings*/ 298 unsigned btype; /*the block type for LZ (0, 1, 2 or 3, see zlib standard). Should be 2 for proper compression.*/ 299 unsigned use_lz77; /*whether or not to use LZ77. Should be 1 for proper compression.*/ 300 unsigned windowsize; /*must be a power of two <= 32768. higher compresses more but is slower. Default value: 2048.*/ 301 unsigned minmatch; /*minimum lz77 length. 3 is normally best, 6 can be better for some PNGs. Default: 0*/ 302 unsigned nicematch; /*stop searching if >= this length found. Set to 258 for best compression. Default: 128*/ 303 unsigned lazymatching; /*use lazy matching: better compression but a bit slower. Default: true*/ 304 305 /*use custom zlib encoder instead of built in one (default: null)*/ 306 unsigned (*custom_zlib)(unsigned char**, size_t*, 307 const unsigned char*, size_t, 308 const LodePNGCompressSettings*); 309 /*use custom deflate encoder instead of built in one (default: null) 310 if custom_zlib is used, custom_deflate is ignored since only the built in 311 zlib function will call custom_deflate*/ 312 unsigned (*custom_deflate)(unsigned char**, size_t*, 313 const unsigned char*, size_t, 314 const LodePNGCompressSettings*); 315 316 const void* custom_context; /*optional custom settings for custom functions*/ 317 }; 318 319 extern const LodePNGCompressSettings lodepng_default_compress_settings; 320 void lodepng_compress_settings_init(LodePNGCompressSettings* settings); 321 #endif /*LODEPNG_COMPILE_ENCODER*/ 322 323 #ifdef LODEPNG_COMPILE_PNG 324 /* 325 Color mode of an image. Contains all information required to decode the pixel 326 bits to RGBA colors. This information is the same as used in the PNG file 327 format, and is used both for PNG and raw image data in LodePNG. 328 */ 329 typedef struct LodePNGColorMode { 330 /*header (IHDR)*/ 331 LodePNGColorType colortype; /*color type, see PNG standard or documentation further in this header file*/ 332 unsigned bitdepth; /*bits per sample, see PNG standard or documentation further in this header file*/ 333 334 /* 335 palette (PLTE and tRNS) 336 337 Dynamically allocated with the colors of the palette, including alpha. 338 This field may not be allocated directly, use lodepng_color_mode_init first, 339 then lodepng_palette_add per color to correctly initialize it (to ensure size 340 of exactly 1024 bytes). 341 342 The alpha channels must be set as well, set them to 255 for opaque images. 343 344 When decoding, by default you can ignore this palette, since LodePNG already 345 fills the palette colors in the pixels of the raw RGBA output. 346 347 The palette is only supported for color type 3. 348 */ 349 unsigned char* palette; /*palette in RGBARGBA... order. When allocated, must be either 0, or have size 1024*/ 350 size_t palettesize; /*palette size in number of colors (amount of bytes is 4 * palettesize)*/ 351 352 /* 353 transparent color key (tRNS) 354 355 This color uses the same bit depth as the bitdepth value in this struct, which can be 1-bit to 16-bit. 356 For grayscale PNGs, r, g and b will all 3 be set to the same. 357 358 When decoding, by default you can ignore this information, since LodePNG sets 359 pixels with this key to transparent already in the raw RGBA output. 360 361 The color key is only supported for color types 0 and 2. 362 */ 363 unsigned key_defined; /*is a transparent color key given? 0 = false, 1 = true*/ 364 unsigned key_r; /*red/grayscale component of color key*/ 365 unsigned key_g; /*green component of color key*/ 366 unsigned key_b; /*blue component of color key*/ 367 } LodePNGColorMode; 368 369 /*init, cleanup and copy functions to use with this struct*/ 370 void lodepng_color_mode_init(LodePNGColorMode* info); 371 void lodepng_color_mode_cleanup(LodePNGColorMode* info); 372 /*return value is error code (0 means no error)*/ 373 unsigned lodepng_color_mode_copy(LodePNGColorMode* dest, const LodePNGColorMode* source); 374 /* Makes a temporary LodePNGColorMode that does not need cleanup (no palette) */ 375 LodePNGColorMode lodepng_color_mode_make(LodePNGColorType colortype, unsigned bitdepth); 376 377 void lodepng_palette_clear(LodePNGColorMode* info); 378 /*add 1 color to the palette*/ 379 unsigned lodepng_palette_add(LodePNGColorMode* info, 380 unsigned char r, unsigned char g, unsigned char b, unsigned char a); 381 382 /*get the total amount of bits per pixel, based on colortype and bitdepth in the struct*/ 383 unsigned lodepng_get_bpp(const LodePNGColorMode* info); 384 /*get the amount of color channels used, based on colortype in the struct. 385 If a palette is used, it counts as 1 channel.*/ 386 unsigned lodepng_get_channels(const LodePNGColorMode* info); 387 /*is it a grayscale type? (only colortype 0 or 4)*/ 388 unsigned lodepng_is_greyscale_type(const LodePNGColorMode* info); 389 /*has it got an alpha channel? (only colortype 2 or 6)*/ 390 unsigned lodepng_is_alpha_type(const LodePNGColorMode* info); 391 /*has it got a palette? (only colortype 3)*/ 392 unsigned lodepng_is_palette_type(const LodePNGColorMode* info); 393 /*only returns true if there is a palette and there is a value in the palette with alpha < 255. 394 Loops through the palette to check this.*/ 395 unsigned lodepng_has_palette_alpha(const LodePNGColorMode* info); 396 /* 397 Check if the given color info indicates the possibility of having non-opaque pixels in the PNG image. 398 Returns true if the image can have translucent or invisible pixels (it still be opaque if it doesn't use such pixels). 399 Returns false if the image can only have opaque pixels. 400 In detail, it returns true only if it's a color type with alpha, or has a palette with non-opaque values, 401 or if "key_defined" is true. 402 */ 403 unsigned lodepng_can_have_alpha(const LodePNGColorMode* info); 404 /*Returns the byte size of a raw image buffer with given width, height and color mode*/ 405 size_t lodepng_get_raw_size(unsigned w, unsigned h, const LodePNGColorMode* color); 406 407 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS 408 /*The information of a Time chunk in PNG.*/ 409 typedef struct LodePNGTime { 410 unsigned year; /*2 bytes used (0-65535)*/ 411 unsigned month; /*1-12*/ 412 unsigned day; /*1-31*/ 413 unsigned hour; /*0-23*/ 414 unsigned minute; /*0-59*/ 415 unsigned second; /*0-60 (to allow for leap seconds)*/ 416 } LodePNGTime; 417 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/ 418 419 /*Information about the PNG image, except pixels, width and height.*/ 420 typedef struct LodePNGInfo { 421 /*header (IHDR), palette (PLTE) and transparency (tRNS) chunks*/ 422 unsigned compression_method;/*compression method of the original file. Always 0.*/ 423 unsigned filter_method; /*filter method of the original file*/ 424 unsigned interlace_method; /*interlace method of the original file: 0=none, 1=Adam7*/ 425 LodePNGColorMode color; /*color type and bits, palette and transparency of the PNG file*/ 426 427 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS 428 /* 429 Suggested background color chunk (bKGD) 430 431 This uses the same color mode and bit depth as the PNG (except no alpha channel), 432 with values truncated to the bit depth in the unsigned integer. 433 434 For grayscale and palette PNGs, the value is stored in background_r. The values 435 in background_g and background_b are then unused. 436 437 So when decoding, you may get these in a different color mode than the one you requested 438 for the raw pixels. 439 440 When encoding with auto_convert, you must use the color model defined in info_png.color for 441 these values. The encoder normally ignores info_png.color when auto_convert is on, but will 442 use it to interpret these values (and convert copies of them to its chosen color model). 443 444 When encoding, avoid setting this to an expensive color, such as a non-gray value 445 when the image is gray, or the compression will be worse since it will be forced to 446 write the PNG with a more expensive color mode (when auto_convert is on). 447 448 The decoder does not use this background color to edit the color of pixels. This is a 449 completely optional metadata feature. 450 */ 451 unsigned background_defined; /*is a suggested background color given?*/ 452 unsigned background_r; /*red/gray/palette component of suggested background color*/ 453 unsigned background_g; /*green component of suggested background color*/ 454 unsigned background_b; /*blue component of suggested background color*/ 455 456 /* 457 non-international text chunks (tEXt and zTXt) 458 459 The char** arrays each contain num strings. The actual messages are in 460 text_strings, while text_keys are keywords that give a short description what 461 the actual text represents, e.g. Title, Author, Description, or anything else. 462 463 All the string fields below including keys, names and language tags are null terminated. 464 The PNG specification uses null characters for the keys, names and tags, and forbids null 465 characters to appear in the main text which is why we can use null termination everywhere here. 466 467 A keyword is minimum 1 character and maximum 79 characters long. It's 468 discouraged to use a single line length longer than 79 characters for texts. 469 470 Don't allocate these text buffers yourself. Use the init/cleanup functions 471 correctly and use lodepng_add_text and lodepng_clear_text. 472 */ 473 size_t text_num; /*the amount of texts in these char** buffers (there may be more texts in itext)*/ 474 char** text_keys; /*the keyword of a text chunk (e.g. "Comment")*/ 475 char** text_strings; /*the actual text*/ 476 477 /* 478 international text chunks (iTXt) 479 Similar to the non-international text chunks, but with additional strings 480 "langtags" and "transkeys". 481 */ 482 size_t itext_num; /*the amount of international texts in this PNG*/ 483 char** itext_keys; /*the English keyword of the text chunk (e.g. "Comment")*/ 484 char** itext_langtags; /*language tag for this text's language, ISO/IEC 646 string, e.g. ISO 639 language tag*/ 485 char** itext_transkeys; /*keyword translated to the international language - UTF-8 string*/ 486 char** itext_strings; /*the actual international text - UTF-8 string*/ 487 488 /*time chunk (tIME)*/ 489 unsigned time_defined; /*set to 1 to make the encoder generate a tIME chunk*/ 490 LodePNGTime time; 491 492 /*phys chunk (pHYs)*/ 493 unsigned phys_defined; /*if 0, there is no pHYs chunk and the values below are undefined, if 1 else there is one*/ 494 unsigned phys_x; /*pixels per unit in x direction*/ 495 unsigned phys_y; /*pixels per unit in y direction*/ 496 unsigned phys_unit; /*may be 0 (unknown unit) or 1 (metre)*/ 497 498 /* 499 Color profile related chunks: gAMA, cHRM, sRGB, iCPP 500 501 LodePNG does not apply any color conversions on pixels in the encoder or decoder and does not interpret these color 502 profile values. It merely passes on the information. If you wish to use color profiles and convert colors, please 503 use these values with a color management library. 504 505 See the PNG, ICC and sRGB specifications for more information about the meaning of these values. 506 */ 507 508 /* gAMA chunk: optional, overridden by sRGB or iCCP if those are present. */ 509 unsigned gama_defined; /* Whether a gAMA chunk is present (0 = not present, 1 = present). */ 510 unsigned gama_gamma; /* Gamma exponent times 100000 */ 511 512 /* cHRM chunk: optional, overridden by sRGB or iCCP if those are present. */ 513 unsigned chrm_defined; /* Whether a cHRM chunk is present (0 = not present, 1 = present). */ 514 unsigned chrm_white_x; /* White Point x times 100000 */ 515 unsigned chrm_white_y; /* White Point y times 100000 */ 516 unsigned chrm_red_x; /* Red x times 100000 */ 517 unsigned chrm_red_y; /* Red y times 100000 */ 518 unsigned chrm_green_x; /* Green x times 100000 */ 519 unsigned chrm_green_y; /* Green y times 100000 */ 520 unsigned chrm_blue_x; /* Blue x times 100000 */ 521 unsigned chrm_blue_y; /* Blue y times 100000 */ 522 523 /* 524 sRGB chunk: optional. May not appear at the same time as iCCP. 525 If gAMA is also present gAMA must contain value 45455. 526 If cHRM is also present cHRM must contain respectively 31270,32900,64000,33000,30000,60000,15000,6000. 527 */ 528 unsigned srgb_defined; /* Whether an sRGB chunk is present (0 = not present, 1 = present). */ 529 unsigned srgb_intent; /* Rendering intent: 0=perceptual, 1=rel. colorimetric, 2=saturation, 3=abs. colorimetric */ 530 531 /* 532 iCCP chunk: optional. May not appear at the same time as sRGB. 533 534 LodePNG does not parse or use the ICC profile (except its color space header field for an edge case), a 535 separate library to handle the ICC data (not included in LodePNG) format is needed to use it for color 536 management and conversions. 537 538 For encoding, if iCCP is present, gAMA and cHRM are recommended to be added as well with values that match the ICC 539 profile as closely as possible, if you wish to do this you should provide the correct values for gAMA and cHRM and 540 enable their '_defined' flags since LodePNG will not automatically compute them from the ICC profile. 541 542 For encoding, the ICC profile is required by the PNG specification to be an "RGB" profile for non-gray 543 PNG color types and a "GRAY" profile for gray PNG color types. If you disable auto_convert, you must ensure 544 the ICC profile type matches your requested color type, else the encoder gives an error. If auto_convert is 545 enabled (the default), and the ICC profile is not a good match for the pixel data, this will result in an encoder 546 error if the pixel data has non-gray pixels for a GRAY profile, or a silent less-optimal compression of the pixel 547 data if the pixels could be encoded as grayscale but the ICC profile is RGB. 548 549 To avoid this do not set an ICC profile in the image unless there is a good reason for it, and when doing so 550 make sure you compute it carefully to avoid the above problems. 551 */ 552 unsigned iccp_defined; /* Whether an iCCP chunk is present (0 = not present, 1 = present). */ 553 char* iccp_name; /* Null terminated string with profile name, 1-79 bytes */ 554 /* 555 The ICC profile in iccp_profile_size bytes. 556 Don't allocate this buffer yourself. Use the init/cleanup functions 557 correctly and use lodepng_set_icc and lodepng_clear_icc. 558 */ 559 unsigned char* iccp_profile; 560 unsigned iccp_profile_size; /* The size of iccp_profile in bytes */ 561 562 /* End of color profile related chunks */ 563 564 565 /* 566 unknown chunks: chunks not known by LodePNG, passed on byte for byte. 567 568 There are 3 buffers, one for each position in the PNG where unknown chunks can appear. 569 Each buffer contains all unknown chunks for that position consecutively. 570 The 3 positions are: 571 0: between IHDR and PLTE, 1: between PLTE and IDAT, 2: between IDAT and IEND. 572 573 For encoding, do not store critical chunks or known chunks that are enabled with a "_defined" flag 574 above in here, since the encoder will blindly follow this and could then encode an invalid PNG file 575 (such as one with two IHDR chunks or the disallowed combination of sRGB with iCCP). But do use 576 this if you wish to store an ancillary chunk that is not supported by LodePNG (such as sPLT or hIST), 577 or any non-standard PNG chunk. 578 579 Do not allocate or traverse this data yourself. Use the chunk traversing functions declared 580 later, such as lodepng_chunk_next and lodepng_chunk_append, to read/write this struct. 581 */ 582 unsigned char* unknown_chunks_data[3]; 583 size_t unknown_chunks_size[3]; /*size in bytes of the unknown chunks, given for protection*/ 584 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/ 585 } LodePNGInfo; 586 587 /*init, cleanup and copy functions to use with this struct*/ 588 void lodepng_info_init(LodePNGInfo* info); 589 void lodepng_info_cleanup(LodePNGInfo* info); 590 /*return value is error code (0 means no error)*/ 591 unsigned lodepng_info_copy(LodePNGInfo* dest, const LodePNGInfo* source); 592 593 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS 594 unsigned lodepng_add_text(LodePNGInfo* info, const char* key, const char* str); /*push back both texts at once*/ 595 void lodepng_clear_text(LodePNGInfo* info); /*use this to clear the texts again after you filled them in*/ 596 597 unsigned lodepng_add_itext(LodePNGInfo* info, const char* key, const char* langtag, 598 const char* transkey, const char* str); /*push back the 4 texts of 1 chunk at once*/ 599 void lodepng_clear_itext(LodePNGInfo* info); /*use this to clear the itexts again after you filled them in*/ 600 601 /*replaces if exists*/ 602 unsigned lodepng_set_icc(LodePNGInfo* info, const char* name, const unsigned char* profile, unsigned profile_size); 603 void lodepng_clear_icc(LodePNGInfo* info); /*use this to clear the texts again after you filled them in*/ 604 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/ 605 606 /* 607 Converts raw buffer from one color type to another color type, based on 608 LodePNGColorMode structs to describe the input and output color type. 609 See the reference manual at the end of this header file to see which color conversions are supported. 610 return value = LodePNG error code (0 if all went ok, an error if the conversion isn't supported) 611 The out buffer must have size (w * h * bpp + 7) / 8, where bpp is the bits per pixel 612 of the output color type (lodepng_get_bpp). 613 For < 8 bpp images, there should not be padding bits at the end of scanlines. 614 For 16-bit per channel colors, uses big endian format like PNG does. 615 Return value is LodePNG error code 616 */ 617 unsigned lodepng_convert(unsigned char* out, const unsigned char* in, 618 const LodePNGColorMode* mode_out, const LodePNGColorMode* mode_in, 619 unsigned w, unsigned h); 620 621 #ifdef LODEPNG_COMPILE_DECODER 622 /* 623 Settings for the decoder. This contains settings for the PNG and the Zlib 624 decoder, but not the Info settings from the Info structs. 625 */ 626 typedef struct LodePNGDecoderSettings { 627 LodePNGDecompressSettings zlibsettings; /*in here is the setting to ignore Adler32 checksums*/ 628 629 /* Check LodePNGDecompressSettings for more ignorable errors such as ignore_adler32 */ 630 unsigned ignore_crc; /*ignore CRC checksums*/ 631 unsigned ignore_critical; /*ignore unknown critical chunks*/ 632 unsigned ignore_end; /*ignore issues at end of file if possible (missing IEND chunk, too large chunk, ...)*/ 633 /* TODO: make a system involving warnings with levels and a strict mode instead. Other potentially recoverable 634 errors: srgb rendering intent value, size of content of ancillary chunks, more than 79 characters for some 635 strings, placement/combination rules for ancillary chunks, crc of unknown chunks, allowed characters 636 in string keys, etc... */ 637 638 unsigned color_convert; /*whether to convert the PNG to the color type you want. Default: yes*/ 639 640 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS 641 unsigned read_text_chunks; /*if false but remember_unknown_chunks is true, they're stored in the unknown chunks*/ 642 /*store all bytes from unknown chunks in the LodePNGInfo (off by default, useful for a png editor)*/ 643 unsigned remember_unknown_chunks; 644 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/ 645 } LodePNGDecoderSettings; 646 647 void lodepng_decoder_settings_init(LodePNGDecoderSettings* settings); 648 #endif /*LODEPNG_COMPILE_DECODER*/ 649 650 #ifdef LODEPNG_COMPILE_ENCODER 651 /*automatically use color type with less bits per pixel if losslessly possible. Default: AUTO*/ 652 typedef enum LodePNGFilterStrategy { 653 /*every filter at zero*/ 654 LFS_ZERO = 0, 655 /*every filter at 1, 2, 3 or 4 (paeth), unlike LFS_ZERO not a good choice, but for testing*/ 656 LFS_ONE = 1, 657 LFS_TWO = 2, 658 LFS_THREE = 3, 659 LFS_FOUR = 4, 660 /*Use filter that gives minimum sum, as described in the official PNG filter heuristic.*/ 661 LFS_MINSUM, 662 /*Use the filter type that gives smallest Shannon entropy for this scanline. Depending 663 on the image, this is better or worse than minsum.*/ 664 LFS_ENTROPY, 665 /* 666 Brute-force-search PNG filters by compressing each filter for each scanline. 667 Experimental, very slow, and only rarely gives better compression than MINSUM. 668 */ 669 LFS_BRUTE_FORCE, 670 /*use predefined_filters buffer: you specify the filter type for each scanline*/ 671 LFS_PREDEFINED 672 } LodePNGFilterStrategy; 673 674 /*Gives characteristics about the integer RGBA colors of the image (count, alpha channel usage, bit depth, ...), 675 which helps decide which color model to use for encoding. 676 Used internally by default if "auto_convert" is enabled. Public because it's useful for custom algorithms.*/ 677 typedef struct LodePNGColorStats { 678 unsigned colored; /*not grayscale*/ 679 unsigned key; /*image is not opaque and color key is possible instead of full alpha*/ 680 unsigned short key_r; /*key values, always as 16-bit, in 8-bit case the byte is duplicated, e.g. 65535 means 255*/ 681 unsigned short key_g; 682 unsigned short key_b; 683 unsigned alpha; /*image is not opaque and alpha channel or alpha palette required*/ 684 unsigned numcolors; /*amount of colors, up to 257. Not valid if bits == 16 or allow_palette is disabled.*/ 685 unsigned char palette[1024]; /*Remembers up to the first 256 RGBA colors, in no particular order, only valid when numcolors is valid*/ 686 unsigned bits; /*bits per channel (not for palette). 1,2 or 4 for grayscale only. 16 if 16-bit per channel required.*/ 687 size_t numpixels; 688 689 /*user settings for computing/using the stats*/ 690 unsigned allow_palette; /*default 1. if 0, disallow choosing palette colortype in auto_choose_color, and don't count numcolors*/ 691 unsigned allow_greyscale; /*default 1. if 0, choose RGB or RGBA even if the image only has gray colors*/ 692 } LodePNGColorStats; 693 694 void lodepng_color_stats_init(LodePNGColorStats* stats); 695 696 /*Get a LodePNGColorStats of the image. The stats must already have been inited.*/ 697 void lodepng_compute_color_stats(LodePNGColorStats* stats, 698 const unsigned char* image, unsigned w, unsigned h, 699 const LodePNGColorMode* mode_in); 700 701 /*Settings for the encoder.*/ 702 typedef struct LodePNGEncoderSettings { 703 LodePNGCompressSettings zlibsettings; /*settings for the zlib encoder, such as window size, ...*/ 704 705 unsigned auto_convert; /*automatically choose output PNG color type. Default: true*/ 706 707 /*If true, follows the official PNG heuristic: if the PNG uses a palette or lower than 708 8 bit depth, set all filters to zero. Otherwise use the filter_strategy. Note that to 709 completely follow the official PNG heuristic, filter_palette_zero must be true and 710 filter_strategy must be LFS_MINSUM*/ 711 unsigned filter_palette_zero; 712 /*Which filter strategy to use when not using zeroes due to filter_palette_zero. 713 Set filter_palette_zero to 0 to ensure always using your chosen strategy. Default: LFS_MINSUM*/ 714 LodePNGFilterStrategy filter_strategy; 715 /*used if filter_strategy is LFS_PREDEFINED. In that case, this must point to a buffer with 716 the same length as the amount of scanlines in the image, and each value must <= 5. You 717 have to cleanup this buffer, LodePNG will never free it. Don't forget that filter_palette_zero 718 must be set to 0 to ensure this is also used on palette or low bitdepth images.*/ 719 const unsigned char* predefined_filters; 720 721 /*force creating a PLTE chunk if colortype is 2 or 6 (= a suggested palette). 722 If colortype is 3, PLTE is _always_ created.*/ 723 unsigned force_palette; 724 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS 725 /*add LodePNG identifier and version as a text chunk, for debugging*/ 726 unsigned add_id; 727 /*encode text chunks as zTXt chunks instead of tEXt chunks, and use compression in iTXt chunks*/ 728 unsigned text_compression; 729 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/ 730 } LodePNGEncoderSettings; 731 732 void lodepng_encoder_settings_init(LodePNGEncoderSettings* settings); 733 #endif /*LODEPNG_COMPILE_ENCODER*/ 734 735 736 #if defined(LODEPNG_COMPILE_DECODER) || defined(LODEPNG_COMPILE_ENCODER) 737 /*The settings, state and information for extended encoding and decoding.*/ 738 typedef struct LodePNGState { 739 #ifdef LODEPNG_COMPILE_DECODER 740 LodePNGDecoderSettings decoder; /*the decoding settings*/ 741 #endif /*LODEPNG_COMPILE_DECODER*/ 742 #ifdef LODEPNG_COMPILE_ENCODER 743 LodePNGEncoderSettings encoder; /*the encoding settings*/ 744 #endif /*LODEPNG_COMPILE_ENCODER*/ 745 LodePNGColorMode info_raw; /*specifies the format in which you would like to get the raw pixel buffer*/ 746 LodePNGInfo info_png; /*info of the PNG image obtained after decoding*/ 747 unsigned error; 748 } LodePNGState; 749 750 /*init, cleanup and copy functions to use with this struct*/ 751 void lodepng_state_init(LodePNGState* state); 752 void lodepng_state_cleanup(LodePNGState* state); 753 void lodepng_state_copy(LodePNGState* dest, const LodePNGState* source); 754 #endif /* defined(LODEPNG_COMPILE_DECODER) || defined(LODEPNG_COMPILE_ENCODER) */ 755 756 #ifdef LODEPNG_COMPILE_DECODER 757 /* 758 Same as lodepng_decode_memory, but uses a LodePNGState to allow custom settings and 759 getting much more information about the PNG image and color mode. 760 */ 761 unsigned lodepng_decode(unsigned char** out, unsigned* w, unsigned* h, 762 LodePNGState* state, 763 const unsigned char* in, size_t insize); 764 765 /* 766 Read the PNG header, but not the actual data. This returns only the information 767 that is in the IHDR chunk of the PNG, such as width, height and color type. The 768 information is placed in the info_png field of the LodePNGState. 769 */ 770 unsigned lodepng_inspect(unsigned* w, unsigned* h, 771 LodePNGState* state, 772 const unsigned char* in, size_t insize); 773 #endif /*LODEPNG_COMPILE_DECODER*/ 774 775 /* 776 Reads one metadata chunk (other than IHDR) of the PNG file and outputs what it 777 read in the state. Returns error code on failure. 778 Use lodepng_inspect first with a new state, then e.g. lodepng_chunk_find_const 779 to find the desired chunk type, and if non null use lodepng_inspect_chunk (with 780 chunk_pointer - start_of_file as pos). 781 Supports most metadata chunks from the PNG standard (gAMA, bKGD, tEXt, ...). 782 Ignores unsupported, unknown, non-metadata or IHDR chunks (without error). 783 Requirements: &in[pos] must point to start of a chunk, must use regular 784 lodepng_inspect first since format of most other chunks depends on IHDR, and if 785 there is a PLTE chunk, that one must be inspected before tRNS or bKGD. 786 */ 787 unsigned lodepng_inspect_chunk(LodePNGState* state, size_t pos, 788 const unsigned char* in, size_t insize); 789 790 #ifdef LODEPNG_COMPILE_ENCODER 791 /*This function allocates the out buffer with standard malloc and stores the size in *outsize.*/ 792 unsigned lodepng_encode(unsigned char** out, size_t* outsize, 793 const unsigned char* image, unsigned w, unsigned h, 794 LodePNGState* state); 795 #endif /*LODEPNG_COMPILE_ENCODER*/ 796 797 /* 798 The lodepng_chunk functions are normally not needed, except to traverse the 799 unknown chunks stored in the LodePNGInfo struct, or add new ones to it. 800 It also allows traversing the chunks of an encoded PNG file yourself. 801 802 The chunk pointer always points to the beginning of the chunk itself, that is 803 the first byte of the 4 length bytes. 804 805 In the PNG file format, chunks have the following format: 806 -4 bytes length: length of the data of the chunk in bytes (chunk itself is 12 bytes longer) 807 -4 bytes chunk type (ASCII a-z,A-Z only, see below) 808 -length bytes of data (may be 0 bytes if length was 0) 809 -4 bytes of CRC, computed on chunk name + data 810 811 The first chunk starts at the 8th byte of the PNG file, the entire rest of the file 812 exists out of concatenated chunks with the above format. 813 814 PNG standard chunk ASCII naming conventions: 815 -First byte: uppercase = critical, lowercase = ancillary 816 -Second byte: uppercase = public, lowercase = private 817 -Third byte: must be uppercase 818 -Fourth byte: uppercase = unsafe to copy, lowercase = safe to copy 819 */ 820 821 /* 822 Gets the length of the data of the chunk. Total chunk length has 12 bytes more. 823 There must be at least 4 bytes to read from. If the result value is too large, 824 it may be corrupt data. 825 */ 826 unsigned lodepng_chunk_length(const unsigned char* chunk); 827 828 /*puts the 4-byte type in null terminated string*/ 829 void lodepng_chunk_type(char type[5], const unsigned char* chunk); 830 831 /*check if the type is the given type*/ 832 unsigned char lodepng_chunk_type_equals(const unsigned char* chunk, const char* type); 833 834 /*0: it's one of the critical chunk types, 1: it's an ancillary chunk (see PNG standard)*/ 835 unsigned char lodepng_chunk_ancillary(const unsigned char* chunk); 836 837 /*0: public, 1: private (see PNG standard)*/ 838 unsigned char lodepng_chunk_private(const unsigned char* chunk); 839 840 /*0: the chunk is unsafe to copy, 1: the chunk is safe to copy (see PNG standard)*/ 841 unsigned char lodepng_chunk_safetocopy(const unsigned char* chunk); 842 843 /*get pointer to the data of the chunk, where the input points to the header of the chunk*/ 844 unsigned char* lodepng_chunk_data(unsigned char* chunk); 845 const unsigned char* lodepng_chunk_data_const(const unsigned char* chunk); 846 847 /*returns 0 if the crc is correct, 1 if it's incorrect (0 for OK as usual!)*/ 848 unsigned lodepng_chunk_check_crc(const unsigned char* chunk); 849 850 /*generates the correct CRC from the data and puts it in the last 4 bytes of the chunk*/ 851 void lodepng_chunk_generate_crc(unsigned char* chunk); 852 853 /* 854 Iterate to next chunks, allows iterating through all chunks of the PNG file. 855 Input must be at the beginning of a chunk (result of a previous lodepng_chunk_next call, 856 or the 8th byte of a PNG file which always has the first chunk), or alternatively may 857 point to the first byte of the PNG file (which is not a chunk but the magic header, the 858 function will then skip over it and return the first real chunk). 859 Expects at least 8 readable bytes of memory in the input pointer. 860 Will output pointer to the start of the next chunk or the end of the file if there 861 is no more chunk after this. Start this process at the 8th byte of the PNG file. 862 In a non-corrupt PNG file, the last chunk should have name "IEND". 863 */ 864 unsigned char* lodepng_chunk_next(unsigned char* chunk); 865 const unsigned char* lodepng_chunk_next_const(const unsigned char* chunk); 866 867 /*Finds the first chunk with the given type in the range [chunk, end), or returns NULL if not found.*/ 868 unsigned char* lodepng_chunk_find(unsigned char* chunk, const unsigned char* end, const char type[5]); 869 const unsigned char* lodepng_chunk_find_const(const unsigned char* chunk, const unsigned char* end, const char type[5]); 870 871 /* 872 Appends chunk to the data in out. The given chunk should already have its chunk header. 873 The out variable and outlength are updated to reflect the new reallocated buffer. 874 Returns error code (0 if it went ok) 875 */ 876 unsigned lodepng_chunk_append(unsigned char** out, size_t* outlength, const unsigned char* chunk); 877 878 /* 879 Appends new chunk to out. The chunk to append is given by giving its length, type 880 and data separately. The type is a 4-letter string. 881 The out variable and outlength are updated to reflect the new reallocated buffer. 882 Returne error code (0 if it went ok) 883 */ 884 unsigned lodepng_chunk_create(unsigned char** out, size_t* outlength, unsigned length, 885 const char* type, const unsigned char* data); 886 887 888 /*Calculate CRC32 of buffer*/ 889 unsigned lodepng_crc32(const unsigned char* buf, size_t len); 890 #endif /*LODEPNG_COMPILE_PNG*/ 891 892 893 #ifdef LODEPNG_COMPILE_ZLIB 894 /* 895 This zlib part can be used independently to zlib compress and decompress a 896 buffer. It cannot be used to create gzip files however, and it only supports the 897 part of zlib that is required for PNG, it does not support dictionaries. 898 */ 899 900 #ifdef LODEPNG_COMPILE_DECODER 901 /*Inflate a buffer. Inflate is the decompression step of deflate. Out buffer must be freed after use.*/ 902 unsigned lodepng_inflate(unsigned char** out, size_t* outsize, 903 const unsigned char* in, size_t insize, 904 const LodePNGDecompressSettings* settings); 905 906 /* 907 Decompresses Zlib data. Reallocates the out buffer and appends the data. The 908 data must be according to the zlib specification. 909 Either, *out must be NULL and *outsize must be 0, or, *out must be a valid 910 buffer and *outsize its size in bytes. out must be freed by user after usage. 911 */ 912 unsigned lodepng_zlib_decompress(unsigned char** out, size_t* outsize, 913 const unsigned char* in, size_t insize, 914 const LodePNGDecompressSettings* settings); 915 #endif /*LODEPNG_COMPILE_DECODER*/ 916 917 #ifdef LODEPNG_COMPILE_ENCODER 918 /* 919 Compresses data with Zlib. Reallocates the out buffer and appends the data. 920 Zlib adds a small header and trailer around the deflate data. 921 The data is output in the format of the zlib specification. 922 Either, *out must be NULL and *outsize must be 0, or, *out must be a valid 923 buffer and *outsize its size in bytes. out must be freed by user after usage. 924 */ 925 unsigned lodepng_zlib_compress(unsigned char** out, size_t* outsize, 926 const unsigned char* in, size_t insize, 927 const LodePNGCompressSettings* settings); 928 929 /* 930 Find length-limited Huffman code for given frequencies. This function is in the 931 public interface only for tests, it's used internally by lodepng_deflate. 932 */ 933 unsigned lodepng_huffman_code_lengths(unsigned* lengths, const unsigned* frequencies, 934 size_t numcodes, unsigned maxbitlen); 935 936 /*Compress a buffer with deflate. See RFC 1951. Out buffer must be freed after use.*/ 937 unsigned lodepng_deflate(unsigned char** out, size_t* outsize, 938 const unsigned char* in, size_t insize, 939 const LodePNGCompressSettings* settings); 940 941 #endif /*LODEPNG_COMPILE_ENCODER*/ 942 #endif /*LODEPNG_COMPILE_ZLIB*/ 943 944 #ifdef LODEPNG_COMPILE_DISK 945 /* 946 Load a file from disk into buffer. The function allocates the out buffer, and 947 after usage you should free it. 948 out: output parameter, contains pointer to loaded buffer. 949 outsize: output parameter, size of the allocated out buffer 950 filename: the path to the file to load 951 return value: error code (0 means ok) 952 */ 953 unsigned lodepng_load_file(unsigned char** out, size_t* outsize, const char* filename); 954 955 /* 956 Save a file from buffer to disk. Warning, if it exists, this function overwrites 957 the file without warning! 958 buffer: the buffer to write 959 buffersize: size of the buffer to write 960 filename: the path to the file to save to 961 return value: error code (0 means ok) 962 */ 963 unsigned lodepng_save_file(const unsigned char* buffer, size_t buffersize, const char* filename); 964 #endif /*LODEPNG_COMPILE_DISK*/ 965 966 #ifdef LODEPNG_COMPILE_CPP 967 /* The LodePNG C++ wrapper uses std::vectors instead of manually allocated memory buffers. */ 968 namespace lodepng { 969 #ifdef LODEPNG_COMPILE_PNG 970 class State : public LodePNGState { 971 public: 972 State(); 973 State(const State& other); 974 ~State(); 975 State& operator=(const State& other); 976 }; 977 978 #ifdef LODEPNG_COMPILE_DECODER 979 /* Same as other lodepng::decode, but using a State for more settings and information. */ 980 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h, 981 State& state, 982 const unsigned char* in, size_t insize); 983 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h, 984 State& state, 985 const std::vector<unsigned char>& in); 986 #endif /*LODEPNG_COMPILE_DECODER*/ 987 988 #ifdef LODEPNG_COMPILE_ENCODER 989 /* Same as other lodepng::encode, but using a State for more settings and information. */ 990 unsigned encode(std::vector<unsigned char>& out, 991 const unsigned char* in, unsigned w, unsigned h, 992 State& state); 993 unsigned encode(std::vector<unsigned char>& out, 994 const std::vector<unsigned char>& in, unsigned w, unsigned h, 995 State& state); 996 #endif /*LODEPNG_COMPILE_ENCODER*/ 997 998 #ifdef LODEPNG_COMPILE_DISK 999 /* 1000 Load a file from disk into an std::vector. 1001 return value: error code (0 means ok) 1002 */ 1003 unsigned load_file(std::vector<unsigned char>& buffer, const std::string& filename); 1004 1005 /* 1006 Save the binary data in an std::vector to a file on disk. The file is overwritten 1007 without warning. 1008 */ 1009 unsigned save_file(const std::vector<unsigned char>& buffer, const std::string& filename); 1010 #endif /* LODEPNG_COMPILE_DISK */ 1011 #endif /* LODEPNG_COMPILE_PNG */ 1012 1013 #ifdef LODEPNG_COMPILE_ZLIB 1014 #ifdef LODEPNG_COMPILE_DECODER 1015 /* Zlib-decompress an unsigned char buffer */ 1016 unsigned decompress(std::vector<unsigned char>& out, const unsigned char* in, size_t insize, 1017 const LodePNGDecompressSettings& settings = lodepng_default_decompress_settings); 1018 1019 /* Zlib-decompress an std::vector */ 1020 unsigned decompress(std::vector<unsigned char>& out, const std::vector<unsigned char>& in, 1021 const LodePNGDecompressSettings& settings = lodepng_default_decompress_settings); 1022 #endif /* LODEPNG_COMPILE_DECODER */ 1023 1024 #ifdef LODEPNG_COMPILE_ENCODER 1025 /* Zlib-compress an unsigned char buffer */ 1026 unsigned compress(std::vector<unsigned char>& out, const unsigned char* in, size_t insize, 1027 const LodePNGCompressSettings& settings = lodepng_default_compress_settings); 1028 1029 /* Zlib-compress an std::vector */ 1030 unsigned compress(std::vector<unsigned char>& out, const std::vector<unsigned char>& in, 1031 const LodePNGCompressSettings& settings = lodepng_default_compress_settings); 1032 #endif /* LODEPNG_COMPILE_ENCODER */ 1033 #endif /* LODEPNG_COMPILE_ZLIB */ 1034 } /* namespace lodepng */ 1035 #endif /*LODEPNG_COMPILE_CPP*/ 1036 1037 /* 1038 TODO: 1039 [.] test if there are no memory leaks or security exploits - done a lot but needs to be checked often 1040 [.] check compatibility with various compilers - done but needs to be redone for every newer version 1041 [X] converting color to 16-bit per channel types 1042 [X] support color profile chunk types (but never let them touch RGB values by default) 1043 [ ] support all public PNG chunk types (almost done except sBIT, sPLT and hIST) 1044 [ ] make sure encoder generates no chunks with size > (2^31)-1 1045 [ ] partial decoding (stream processing) 1046 [X] let the "isFullyOpaque" function check color keys and transparent palettes too 1047 [X] better name for the variables "codes", "codesD", "codelengthcodes", "clcl" and "lldl" 1048 [ ] allow treating some errors like warnings, when image is recoverable (e.g. 69, 57, 58) 1049 [ ] make warnings like: oob palette, checksum fail, data after iend, wrong/unknown crit chunk, no null terminator in text, ... 1050 [ ] error messages with line numbers (and version) 1051 [ ] errors in state instead of as return code? 1052 [ ] new errors/warnings like suspiciously big decompressed ztxt or iccp chunk 1053 [ ] let the C++ wrapper catch exceptions coming from the standard library and return LodePNG error codes 1054 [ ] allow user to provide custom color conversion functions, e.g. for premultiplied alpha, padding bits or not, ... 1055 [ ] allow user to give data (void*) to custom allocator 1056 [ ] provide alternatives for C library functions not present on some platforms (memcpy, ...) 1057 [ ] rename "grey" to "gray" everywhere since "color" also uses US spelling (keep "grey" copies for backwards compatibility) 1058 */ 1059 1060 #endif /*LODEPNG_H inclusion guard*/ 1061 1062 /* 1063 LodePNG Documentation 1064 --------------------- 1065 1066 0. table of contents 1067 -------------------- 1068 1069 1. about 1070 1.1. supported features 1071 1.2. features not supported 1072 2. C and C++ version 1073 3. security 1074 4. decoding 1075 5. encoding 1076 6. color conversions 1077 6.1. PNG color types 1078 6.2. color conversions 1079 6.3. padding bits 1080 6.4. A note about 16-bits per channel and endianness 1081 7. error values 1082 8. chunks and PNG editing 1083 9. compiler support 1084 10. examples 1085 10.1. decoder C++ example 1086 10.2. decoder C example 1087 11. state settings reference 1088 12. changes 1089 13. contact information 1090 1091 1092 1. about 1093 -------- 1094 1095 PNG is a file format to store raster images losslessly with good compression, 1096 supporting different color types and alpha channel. 1097 1098 LodePNG is a PNG codec according to the Portable Network Graphics (PNG) 1099 Specification (Second Edition) - W3C Recommendation 10 November 2003. 1100 1101 The specifications used are: 1102 1103 *) Portable Network Graphics (PNG) Specification (Second Edition): 1104 http://www.w3.org/TR/2003/REC-PNG-20031110 1105 *) RFC 1950 ZLIB Compressed Data Format version 3.3: 1106 http://www.gzip.org/zlib/rfc-zlib.html 1107 *) RFC 1951 DEFLATE Compressed Data Format Specification ver 1.3: 1108 http://www.gzip.org/zlib/rfc-deflate.html 1109 1110 The most recent version of LodePNG can currently be found at 1111 http://lodev.org/lodepng/ 1112 1113 LodePNG works both in C (ISO C90) and C++, with a C++ wrapper that adds 1114 extra functionality. 1115 1116 LodePNG exists out of two files: 1117 -lodepng.h: the header file for both C and C++ 1118 -lodepng.c(pp): give it the name lodepng.c or lodepng.cpp (or .cc) depending on your usage 1119 1120 If you want to start using LodePNG right away without reading this doc, get the 1121 examples from the LodePNG website to see how to use it in code, or check the 1122 smaller examples in chapter 13 here. 1123 1124 LodePNG is simple but only supports the basic requirements. To achieve 1125 simplicity, the following design choices were made: There are no dependencies 1126 on any external library. There are functions to decode and encode a PNG with 1127 a single function call, and extended versions of these functions taking a 1128 LodePNGState struct allowing to specify or get more information. By default 1129 the colors of the raw image are always RGB or RGBA, no matter what color type 1130 the PNG file uses. To read and write files, there are simple functions to 1131 convert the files to/from buffers in memory. 1132 1133 This all makes LodePNG suitable for loading textures in games, demos and small 1134 programs, ... It's less suitable for full fledged image editors, loading PNGs 1135 over network (it requires all the image data to be available before decoding can 1136 begin), life-critical systems, ... 1137 1138 1.1. supported features 1139 ----------------------- 1140 1141 The following features are supported by the decoder: 1142 1143 *) decoding of PNGs with any color type, bit depth and interlace mode, to a 24- or 32-bit color raw image, 1144 or the same color type as the PNG 1145 *) encoding of PNGs, from any raw image to 24- or 32-bit color, or the same color type as the raw image 1146 *) Adam7 interlace and deinterlace for any color type 1147 *) loading the image from harddisk or decoding it from a buffer from other sources than harddisk 1148 *) support for alpha channels, including RGBA color model, translucent palettes and color keying 1149 *) zlib decompression (inflate) 1150 *) zlib compression (deflate) 1151 *) CRC32 and ADLER32 checksums 1152 *) colorimetric color profile conversions: currently experimentally available in lodepng_util.cpp only, 1153 plus alternatively ability to pass on chroma/gamma/ICC profile information to other color management system. 1154 *) handling of unknown chunks, allowing making a PNG editor that stores custom and unknown chunks. 1155 *) the following chunks are supported by both encoder and decoder: 1156 IHDR: header information 1157 PLTE: color palette 1158 IDAT: pixel data 1159 IEND: the final chunk 1160 tRNS: transparency for palettized images 1161 tEXt: textual information 1162 zTXt: compressed textual information 1163 iTXt: international textual information 1164 bKGD: suggested background color 1165 pHYs: physical dimensions 1166 tIME: modification time 1167 cHRM: RGB chromaticities 1168 gAMA: RGB gamma correction 1169 iCCP: ICC color profile 1170 sRGB: rendering intent 1171 1172 1.2. features not supported 1173 --------------------------- 1174 1175 The following features are _not_ supported: 1176 1177 *) some features needed to make a conformant PNG-Editor might be still missing. 1178 *) partial loading/stream processing. All data must be available and is processed in one call. 1179 *) The following public chunks are not (yet) supported but treated as unknown chunks by LodePNG: 1180 sBIT 1181 hIST 1182 sPLT 1183 1184 1185 2. C and C++ version 1186 -------------------- 1187 1188 The C version uses buffers allocated with alloc that you need to free() 1189 yourself. You need to use init and cleanup functions for each struct whenever 1190 using a struct from the C version to avoid exploits and memory leaks. 1191 1192 The C++ version has extra functions with std::vectors in the interface and the 1193 lodepng::State class which is a LodePNGState with constructor and destructor. 1194 1195 These files work without modification for both C and C++ compilers because all 1196 the additional C++ code is in "#ifdef __cplusplus" blocks that make C-compilers 1197 ignore it, and the C code is made to compile both with strict ISO C90 and C++. 1198 1199 To use the C++ version, you need to rename the source file to lodepng.cpp 1200 (instead of lodepng.c), and compile it with a C++ compiler. 1201 1202 To use the C version, you need to rename the source file to lodepng.c (instead 1203 of lodepng.cpp), and compile it with a C compiler. 1204 1205 1206 3. Security 1207 ----------- 1208 1209 Even if carefully designed, it's always possible that LodePNG contains possible 1210 exploits. If you discover one, please let me know, and it will be fixed. 1211 1212 When using LodePNG, care has to be taken with the C version of LodePNG, as well 1213 as the C-style structs when working with C++. The following conventions are used 1214 for all C-style structs: 1215 1216 -if a struct has a corresponding init function, always call the init function when making a new one 1217 -if a struct has a corresponding cleanup function, call it before the struct disappears to avoid memory leaks 1218 -if a struct has a corresponding copy function, use the copy function instead of "=". 1219 The destination must also be inited already. 1220 1221 1222 4. Decoding 1223 ----------- 1224 1225 Decoding converts a PNG compressed image to a raw pixel buffer. 1226 1227 Most documentation on using the decoder is at its declarations in the header 1228 above. For C, simple decoding can be done with functions such as 1229 lodepng_decode32, and more advanced decoding can be done with the struct 1230 LodePNGState and lodepng_decode. For C++, all decoding can be done with the 1231 various lodepng::decode functions, and lodepng::State can be used for advanced 1232 features. 1233 1234 When using the LodePNGState, it uses the following fields for decoding: 1235 *) LodePNGInfo info_png: it stores extra information about the PNG (the input) in here 1236 *) LodePNGColorMode info_raw: here you can say what color mode of the raw image (the output) you want to get 1237 *) LodePNGDecoderSettings decoder: you can specify a few extra settings for the decoder to use 1238 1239 LodePNGInfo info_png 1240 -------------------- 1241 1242 After decoding, this contains extra information of the PNG image, except the actual 1243 pixels, width and height because these are already gotten directly from the decoder 1244 functions. 1245 1246 It contains for example the original color type of the PNG image, text comments, 1247 suggested background color, etc... More details about the LodePNGInfo struct are 1248 at its declaration documentation. 1249 1250 LodePNGColorMode info_raw 1251 ------------------------- 1252 1253 When decoding, here you can specify which color type you want 1254 the resulting raw image to be. If this is different from the colortype of the 1255 PNG, then the decoder will automatically convert the result. This conversion 1256 always works, except if you want it to convert a color PNG to grayscale or to 1257 a palette with missing colors. 1258 1259 By default, 32-bit color is used for the result. 1260 1261 LodePNGDecoderSettings decoder 1262 ------------------------------ 1263 1264 The settings can be used to ignore the errors created by invalid CRC and Adler32 1265 chunks, and to disable the decoding of tEXt chunks. 1266 1267 There's also a setting color_convert, true by default. If false, no conversion 1268 is done, the resulting data will be as it was in the PNG (after decompression) 1269 and you'll have to puzzle the colors of the pixels together yourself using the 1270 color type information in the LodePNGInfo. 1271 1272 1273 5. Encoding 1274 ----------- 1275 1276 Encoding converts a raw pixel buffer to a PNG compressed image. 1277 1278 Most documentation on using the encoder is at its declarations in the header 1279 above. For C, simple encoding can be done with functions such as 1280 lodepng_encode32, and more advanced decoding can be done with the struct 1281 LodePNGState and lodepng_encode. For C++, all encoding can be done with the 1282 various lodepng::encode functions, and lodepng::State can be used for advanced 1283 features. 1284 1285 Like the decoder, the encoder can also give errors. However it gives less errors 1286 since the encoder input is trusted, the decoder input (a PNG image that could 1287 be forged by anyone) is not trusted. 1288 1289 When using the LodePNGState, it uses the following fields for encoding: 1290 *) LodePNGInfo info_png: here you specify how you want the PNG (the output) to be. 1291 *) LodePNGColorMode info_raw: here you say what color type of the raw image (the input) has 1292 *) LodePNGEncoderSettings encoder: you can specify a few settings for the encoder to use 1293 1294 LodePNGInfo info_png 1295 -------------------- 1296 1297 When encoding, you use this the opposite way as when decoding: for encoding, 1298 you fill in the values you want the PNG to have before encoding. By default it's 1299 not needed to specify a color type for the PNG since it's automatically chosen, 1300 but it's possible to choose it yourself given the right settings. 1301 1302 The encoder will not always exactly match the LodePNGInfo struct you give, 1303 it tries as close as possible. Some things are ignored by the encoder. The 1304 encoder uses, for example, the following settings from it when applicable: 1305 colortype and bitdepth, text chunks, time chunk, the color key, the palette, the 1306 background color, the interlace method, unknown chunks, ... 1307 1308 When encoding to a PNG with colortype 3, the encoder will generate a PLTE chunk. 1309 If the palette contains any colors for which the alpha channel is not 255 (so 1310 there are translucent colors in the palette), it'll add a tRNS chunk. 1311 1312 LodePNGColorMode info_raw 1313 ------------------------- 1314 1315 You specify the color type of the raw image that you give to the input here, 1316 including a possible transparent color key and palette you happen to be using in 1317 your raw image data. 1318 1319 By default, 32-bit color is assumed, meaning your input has to be in RGBA 1320 format with 4 bytes (unsigned chars) per pixel. 1321 1322 LodePNGEncoderSettings encoder 1323 ------------------------------ 1324 1325 The following settings are supported (some are in sub-structs): 1326 *) auto_convert: when this option is enabled, the encoder will 1327 automatically choose the smallest possible color mode (including color key) that 1328 can encode the colors of all pixels without information loss. 1329 *) btype: the block type for LZ77. 0 = uncompressed, 1 = fixed huffman tree, 1330 2 = dynamic huffman tree (best compression). Should be 2 for proper 1331 compression. 1332 *) use_lz77: whether or not to use LZ77 for compressed block types. Should be 1333 true for proper compression. 1334 *) windowsize: the window size used by the LZ77 encoder (1 - 32768). Has value 1335 2048 by default, but can be set to 32768 for better, but slow, compression. 1336 *) force_palette: if colortype is 2 or 6, you can make the encoder write a PLTE 1337 chunk if force_palette is true. This can used as suggested palette to convert 1338 to by viewers that don't support more than 256 colors (if those still exist) 1339 *) add_id: add text chunk "Encoder: LodePNG <version>" to the image. 1340 *) text_compression: default 1. If 1, it'll store texts as zTXt instead of tEXt chunks. 1341 zTXt chunks use zlib compression on the text. This gives a smaller result on 1342 large texts but a larger result on small texts (such as a single program name). 1343 It's all tEXt or all zTXt though, there's no separate setting per text yet. 1344 1345 1346 6. color conversions 1347 -------------------- 1348 1349 An important thing to note about LodePNG, is that the color type of the PNG, and 1350 the color type of the raw image, are completely independent. By default, when 1351 you decode a PNG, you get the result as a raw image in the color type you want, 1352 no matter whether the PNG was encoded with a palette, grayscale or RGBA color. 1353 And if you encode an image, by default LodePNG will automatically choose the PNG 1354 color type that gives good compression based on the values of colors and amount 1355 of colors in the image. It can be configured to let you control it instead as 1356 well, though. 1357 1358 To be able to do this, LodePNG does conversions from one color mode to another. 1359 It can convert from almost any color type to any other color type, except the 1360 following conversions: RGB to grayscale is not supported, and converting to a 1361 palette when the palette doesn't have a required color is not supported. This is 1362 not supported on purpose: this is information loss which requires a color 1363 reduction algorithm that is beyond the scope of a PNG encoder (yes, RGB to gray 1364 is easy, but there are multiple ways if you want to give some channels more 1365 weight). 1366 1367 By default, when decoding, you get the raw image in 32-bit RGBA or 24-bit RGB 1368 color, no matter what color type the PNG has. And by default when encoding, 1369 LodePNG automatically picks the best color model for the output PNG, and expects 1370 the input image to be 32-bit RGBA or 24-bit RGB. So, unless you want to control 1371 the color format of the images yourself, you can skip this chapter. 1372 1373 6.1. PNG color types 1374 -------------------- 1375 1376 A PNG image can have many color types, ranging from 1-bit color to 64-bit color, 1377 as well as palettized color modes. After the zlib decompression and unfiltering 1378 in the PNG image is done, the raw pixel data will have that color type and thus 1379 a certain amount of bits per pixel. If you want the output raw image after 1380 decoding to have another color type, a conversion is done by LodePNG. 1381 1382 The PNG specification gives the following color types: 1383 1384 0: grayscale, bit depths 1, 2, 4, 8, 16 1385 2: RGB, bit depths 8 and 16 1386 3: palette, bit depths 1, 2, 4 and 8 1387 4: grayscale with alpha, bit depths 8 and 16 1388 6: RGBA, bit depths 8 and 16 1389 1390 Bit depth is the amount of bits per pixel per color channel. So the total amount 1391 of bits per pixel is: amount of channels * bitdepth. 1392 1393 6.2. color conversions 1394 ---------------------- 1395 1396 As explained in the sections about the encoder and decoder, you can specify 1397 color types and bit depths in info_png and info_raw to change the default 1398 behaviour. 1399 1400 If, when decoding, you want the raw image to be something else than the default, 1401 you need to set the color type and bit depth you want in the LodePNGColorMode, 1402 or the parameters colortype and bitdepth of the simple decoding function. 1403 1404 If, when encoding, you use another color type than the default in the raw input 1405 image, you need to specify its color type and bit depth in the LodePNGColorMode 1406 of the raw image, or use the parameters colortype and bitdepth of the simple 1407 encoding function. 1408 1409 If, when encoding, you don't want LodePNG to choose the output PNG color type 1410 but control it yourself, you need to set auto_convert in the encoder settings 1411 to false, and specify the color type you want in the LodePNGInfo of the 1412 encoder (including palette: it can generate a palette if auto_convert is true, 1413 otherwise not). 1414 1415 If the input and output color type differ (whether user chosen or auto chosen), 1416 LodePNG will do a color conversion, which follows the rules below, and may 1417 sometimes result in an error. 1418 1419 To avoid some confusion: 1420 -the decoder converts from PNG to raw image 1421 -the encoder converts from raw image to PNG 1422 -the colortype and bitdepth in LodePNGColorMode info_raw, are those of the raw image 1423 -the colortype and bitdepth in the color field of LodePNGInfo info_png, are those of the PNG 1424 -when encoding, the color type in LodePNGInfo is ignored if auto_convert 1425 is enabled, it is automatically generated instead 1426 -when decoding, the color type in LodePNGInfo is set by the decoder to that of the original 1427 PNG image, but it can be ignored since the raw image has the color type you requested instead 1428 -if the color type of the LodePNGColorMode and PNG image aren't the same, a conversion 1429 between the color types is done if the color types are supported. If it is not 1430 supported, an error is returned. If the types are the same, no conversion is done. 1431 -even though some conversions aren't supported, LodePNG supports loading PNGs from any 1432 colortype and saving PNGs to any colortype, sometimes it just requires preparing 1433 the raw image correctly before encoding. 1434 -both encoder and decoder use the same color converter. 1435 1436 The function lodepng_convert does the color conversion. It is available in the 1437 interface but normally isn't needed since the encoder and decoder already call 1438 it. 1439 1440 Non supported color conversions: 1441 -color to grayscale when non-gray pixels are present: no error is thrown, but 1442 the result will look ugly because only the red channel is taken (it assumes all 1443 three channels are the same in this case so ignores green and blue). The reason 1444 no error is given is to allow converting from three-channel grayscale images to 1445 one-channel even if there are numerical imprecisions. 1446 -anything to palette when the palette does not have an exact match for a from-color 1447 in it: in this case an error is thrown 1448 1449 Supported color conversions: 1450 -anything to 8-bit RGB, 8-bit RGBA, 16-bit RGB, 16-bit RGBA 1451 -any gray or gray+alpha, to gray or gray+alpha 1452 -anything to a palette, as long as the palette has the requested colors in it 1453 -removing alpha channel 1454 -higher to smaller bitdepth, and vice versa 1455 1456 If you want no color conversion to be done (e.g. for speed or control): 1457 -In the encoder, you can make it save a PNG with any color type by giving the 1458 raw color mode and LodePNGInfo the same color mode, and setting auto_convert to 1459 false. 1460 -In the decoder, you can make it store the pixel data in the same color type 1461 as the PNG has, by setting the color_convert setting to false. Settings in 1462 info_raw are then ignored. 1463 1464 6.3. padding bits 1465 ----------------- 1466 1467 In the PNG file format, if a less than 8-bit per pixel color type is used and the scanlines 1468 have a bit amount that isn't a multiple of 8, then padding bits are used so that each 1469 scanline starts at a fresh byte. But that is NOT true for the LodePNG raw input and output. 1470 The raw input image you give to the encoder, and the raw output image you get from the decoder 1471 will NOT have these padding bits, e.g. in the case of a 1-bit image with a width 1472 of 7 pixels, the first pixel of the second scanline will the 8th bit of the first byte, 1473 not the first bit of a new byte. 1474 1475 6.4. A note about 16-bits per channel and endianness 1476 ---------------------------------------------------- 1477 1478 LodePNG uses unsigned char arrays for 16-bit per channel colors too, just like 1479 for any other color format. The 16-bit values are stored in big endian (most 1480 significant byte first) in these arrays. This is the opposite order of the 1481 little endian used by x86 CPU's. 1482 1483 LodePNG always uses big endian because the PNG file format does so internally. 1484 Conversions to other formats than PNG uses internally are not supported by 1485 LodePNG on purpose, there are myriads of formats, including endianness of 16-bit 1486 colors, the order in which you store R, G, B and A, and so on. Supporting and 1487 converting to/from all that is outside the scope of LodePNG. 1488 1489 This may mean that, depending on your use case, you may want to convert the big 1490 endian output of LodePNG to little endian with a for loop. This is certainly not 1491 always needed, many applications and libraries support big endian 16-bit colors 1492 anyway, but it means you cannot simply cast the unsigned char* buffer to an 1493 unsigned short* buffer on x86 CPUs. 1494 1495 1496 7. error values 1497 --------------- 1498 1499 All functions in LodePNG that return an error code, return 0 if everything went 1500 OK, or a non-zero code if there was an error. 1501 1502 The meaning of the LodePNG error values can be retrieved with the function 1503 lodepng_error_text: given the numerical error code, it returns a description 1504 of the error in English as a string. 1505 1506 Check the implementation of lodepng_error_text to see the meaning of each code. 1507 1508 1509 8. chunks and PNG editing 1510 ------------------------- 1511 1512 If you want to add extra chunks to a PNG you encode, or use LodePNG for a PNG 1513 editor that should follow the rules about handling of unknown chunks, or if your 1514 program is able to read other types of chunks than the ones handled by LodePNG, 1515 then that's possible with the chunk functions of LodePNG. 1516 1517 A PNG chunk has the following layout: 1518 1519 4 bytes length 1520 4 bytes type name 1521 length bytes data 1522 4 bytes CRC 1523 1524 8.1. iterating through chunks 1525 ----------------------------- 1526 1527 If you have a buffer containing the PNG image data, then the first chunk (the 1528 IHDR chunk) starts at byte number 8 of that buffer. The first 8 bytes are the 1529 signature of the PNG and are not part of a chunk. But if you start at byte 8 1530 then you have a chunk, and can check the following things of it. 1531 1532 NOTE: none of these functions check for memory buffer boundaries. To avoid 1533 exploits, always make sure the buffer contains all the data of the chunks. 1534 When using lodepng_chunk_next, make sure the returned value is within the 1535 allocated memory. 1536 1537 unsigned lodepng_chunk_length(const unsigned char* chunk): 1538 1539 Get the length of the chunk's data. The total chunk length is this length + 12. 1540 1541 void lodepng_chunk_type(char type[5], const unsigned char* chunk): 1542 unsigned char lodepng_chunk_type_equals(const unsigned char* chunk, const char* type): 1543 1544 Get the type of the chunk or compare if it's a certain type 1545 1546 unsigned char lodepng_chunk_critical(const unsigned char* chunk): 1547 unsigned char lodepng_chunk_private(const unsigned char* chunk): 1548 unsigned char lodepng_chunk_safetocopy(const unsigned char* chunk): 1549 1550 Check if the chunk is critical in the PNG standard (only IHDR, PLTE, IDAT and IEND are). 1551 Check if the chunk is private (public chunks are part of the standard, private ones not). 1552 Check if the chunk is safe to copy. If it's not, then, when modifying data in a critical 1553 chunk, unsafe to copy chunks of the old image may NOT be saved in the new one if your 1554 program doesn't handle that type of unknown chunk. 1555 1556 unsigned char* lodepng_chunk_data(unsigned char* chunk): 1557 const unsigned char* lodepng_chunk_data_const(const unsigned char* chunk): 1558 1559 Get a pointer to the start of the data of the chunk. 1560 1561 unsigned lodepng_chunk_check_crc(const unsigned char* chunk): 1562 void lodepng_chunk_generate_crc(unsigned char* chunk): 1563 1564 Check if the crc is correct or generate a correct one. 1565 1566 unsigned char* lodepng_chunk_next(unsigned char* chunk): 1567 const unsigned char* lodepng_chunk_next_const(const unsigned char* chunk): 1568 1569 Iterate to the next chunk. This works if you have a buffer with consecutive chunks. Note that these 1570 functions do no boundary checking of the allocated data whatsoever, so make sure there is enough 1571 data available in the buffer to be able to go to the next chunk. 1572 1573 unsigned lodepng_chunk_append(unsigned char** out, size_t* outlength, const unsigned char* chunk): 1574 unsigned lodepng_chunk_create(unsigned char** out, size_t* outlength, unsigned length, 1575 const char* type, const unsigned char* data): 1576 1577 These functions are used to create new chunks that are appended to the data in *out that has 1578 length *outlength. The append function appends an existing chunk to the new data. The create 1579 function creates a new chunk with the given parameters and appends it. Type is the 4-letter 1580 name of the chunk. 1581 1582 8.2. chunks in info_png 1583 ----------------------- 1584 1585 The LodePNGInfo struct contains fields with the unknown chunk in it. It has 3 1586 buffers (each with size) to contain 3 types of unknown chunks: 1587 the ones that come before the PLTE chunk, the ones that come between the PLTE 1588 and the IDAT chunks, and the ones that come after the IDAT chunks. 1589 It's necessary to make the distinction between these 3 cases because the PNG 1590 standard forces to keep the ordering of unknown chunks compared to the critical 1591 chunks, but does not force any other ordering rules. 1592 1593 info_png.unknown_chunks_data[0] is the chunks before PLTE 1594 info_png.unknown_chunks_data[1] is the chunks after PLTE, before IDAT 1595 info_png.unknown_chunks_data[2] is the chunks after IDAT 1596 1597 The chunks in these 3 buffers can be iterated through and read by using the same 1598 way described in the previous subchapter. 1599 1600 When using the decoder to decode a PNG, you can make it store all unknown chunks 1601 if you set the option settings.remember_unknown_chunks to 1. By default, this 1602 option is off (0). 1603 1604 The encoder will always encode unknown chunks that are stored in the info_png. 1605 If you need it to add a particular chunk that isn't known by LodePNG, you can 1606 use lodepng_chunk_append or lodepng_chunk_create to the chunk data in 1607 info_png.unknown_chunks_data[x]. 1608 1609 Chunks that are known by LodePNG should not be added in that way. E.g. to make 1610 LodePNG add a bKGD chunk, set background_defined to true and add the correct 1611 parameters there instead. 1612 1613 1614 9. compiler support 1615 ------------------- 1616 1617 No libraries other than the current standard C library are needed to compile 1618 LodePNG. For the C++ version, only the standard C++ library is needed on top. 1619 Add the files lodepng.c(pp) and lodepng.h to your project, include 1620 lodepng.h where needed, and your program can read/write PNG files. 1621 1622 It is compatible with C90 and up, and C++03 and up. 1623 1624 If performance is important, use optimization when compiling! For both the 1625 encoder and decoder, this makes a large difference. 1626 1627 Make sure that LodePNG is compiled with the same compiler of the same version 1628 and with the same settings as the rest of the program, or the interfaces with 1629 std::vectors and std::strings in C++ can be incompatible. 1630 1631 CHAR_BITS must be 8 or higher, because LodePNG uses unsigned chars for octets. 1632 1633 *) gcc and g++ 1634 1635 LodePNG is developed in gcc so this compiler is natively supported. It gives no 1636 warnings with compiler options "-Wall -Wextra -pedantic -ansi", with gcc and g++ 1637 version 4.7.1 on Linux, 32-bit and 64-bit. 1638 1639 *) Clang 1640 1641 Fully supported and warning-free. 1642 1643 *) Mingw 1644 1645 The Mingw compiler (a port of gcc for Windows) should be fully supported by 1646 LodePNG. 1647 1648 *) Visual Studio and Visual C++ Express Edition 1649 1650 LodePNG should be warning-free with warning level W4. Two warnings were disabled 1651 with pragmas though: warning 4244 about implicit conversions, and warning 4996 1652 where it wants to use a non-standard function fopen_s instead of the standard C 1653 fopen. 1654 1655 Visual Studio may want "stdafx.h" files to be included in each source file and 1656 give an error "unexpected end of file while looking for precompiled header". 1657 This is not standard C++ and will not be added to the stock LodePNG. You can 1658 disable it for lodepng.cpp only by right clicking it, Properties, C/C++, 1659 Precompiled Headers, and set it to Not Using Precompiled Headers there. 1660 1661 NOTE: Modern versions of VS should be fully supported, but old versions, e.g. 1662 VS6, are not guaranteed to work. 1663 1664 *) Compilers on Macintosh 1665 1666 LodePNG has been reported to work both with gcc and LLVM for Macintosh, both for 1667 C and C++. 1668 1669 *) Other Compilers 1670 1671 If you encounter problems on any compilers, feel free to let me know and I may 1672 try to fix it if the compiler is modern and standards compliant. 1673 1674 1675 10. examples 1676 ------------ 1677 1678 This decoder example shows the most basic usage of LodePNG. More complex 1679 examples can be found on the LodePNG website. 1680 1681 10.1. decoder C++ example 1682 ------------------------- 1683 1684 #include "lodepng.h" 1685 #include <iostream> 1686 1687 int main(int argc, char *argv[]) { 1688 const char* filename = argc > 1 ? argv[1] : "test.png"; 1689 1690 //load and decode 1691 std::vector<unsigned char> image; 1692 unsigned width, height; 1693 unsigned error = lodepng::decode(image, width, height, filename); 1694 1695 //if there's an error, display it 1696 if(error) std::cout << "decoder error " << error << ": " << lodepng_error_text(error) << std::endl; 1697 1698 //the pixels are now in the vector "image", 4 bytes per pixel, ordered RGBARGBA..., use it as texture, draw it, ... 1699 } 1700 1701 10.2. decoder C example 1702 ----------------------- 1703 1704 #include "lodepng.h" 1705 1706 int main(int argc, char *argv[]) { 1707 unsigned error; 1708 unsigned char* image; 1709 size_t width, height; 1710 const char* filename = argc > 1 ? argv[1] : "test.png"; 1711 1712 error = lodepng_decode32_file(&image, &width, &height, filename); 1713 1714 if(error) printf("decoder error %u: %s\n", error, lodepng_error_text(error)); 1715 1716 / * use image here * / 1717 1718 free(image); 1719 return 0; 1720 } 1721 1722 11. state settings reference 1723 ---------------------------- 1724 1725 A quick reference of some settings to set on the LodePNGState 1726 1727 For decoding: 1728 1729 state.decoder.zlibsettings.ignore_adler32: ignore ADLER32 checksums 1730 state.decoder.zlibsettings.custom_...: use custom inflate function 1731 state.decoder.ignore_crc: ignore CRC checksums 1732 state.decoder.ignore_critical: ignore unknown critical chunks 1733 state.decoder.ignore_end: ignore missing IEND chunk. May fail if this corruption causes other errors 1734 state.decoder.color_convert: convert internal PNG color to chosen one 1735 state.decoder.read_text_chunks: whether to read in text metadata chunks 1736 state.decoder.remember_unknown_chunks: whether to read in unknown chunks 1737 state.info_raw.colortype: desired color type for decoded image 1738 state.info_raw.bitdepth: desired bit depth for decoded image 1739 state.info_raw....: more color settings, see struct LodePNGColorMode 1740 state.info_png....: no settings for decoder but ouput, see struct LodePNGInfo 1741 1742 For encoding: 1743 1744 state.encoder.zlibsettings.btype: disable compression by setting it to 0 1745 state.encoder.zlibsettings.use_lz77: use LZ77 in compression 1746 state.encoder.zlibsettings.windowsize: tweak LZ77 windowsize 1747 state.encoder.zlibsettings.minmatch: tweak min LZ77 length to match 1748 state.encoder.zlibsettings.nicematch: tweak LZ77 match where to stop searching 1749 state.encoder.zlibsettings.lazymatching: try one more LZ77 matching 1750 state.encoder.zlibsettings.custom_...: use custom deflate function 1751 state.encoder.auto_convert: choose optimal PNG color type, if 0 uses info_png 1752 state.encoder.filter_palette_zero: PNG filter strategy for palette 1753 state.encoder.filter_strategy: PNG filter strategy to encode with 1754 state.encoder.force_palette: add palette even if not encoding to one 1755 state.encoder.add_id: add LodePNG identifier and version as a text chunk 1756 state.encoder.text_compression: use compressed text chunks for metadata 1757 state.info_raw.colortype: color type of raw input image you provide 1758 state.info_raw.bitdepth: bit depth of raw input image you provide 1759 state.info_raw: more color settings, see struct LodePNGColorMode 1760 state.info_png.color.colortype: desired color type if auto_convert is false 1761 state.info_png.color.bitdepth: desired bit depth if auto_convert is false 1762 state.info_png.color....: more color settings, see struct LodePNGColorMode 1763 state.info_png....: more PNG related settings, see struct LodePNGInfo 1764 1765 1766 12. changes 1767 ----------- 1768 1769 The version number of LodePNG is the date of the change given in the format 1770 yyyymmdd. 1771 1772 Some changes aren't backwards compatible. Those are indicated with a (!) 1773 symbol. 1774 1775 Not all changes are listed here, the commit history in github lists more: 1776 https://github.com/lvandeve/lodepng 1777 1778 *) 14 aug 2019: around 25% faster decoding thanks to huffman lookup tables. 1779 *) 15 jun 2019 (!): auto_choose_color API changed (for bugfix: don't use palette 1780 if gray ICC profile) and non-ICC LodePNGColorProfile renamed to LodePNGColorStats. 1781 *) 30 dec 2018: code style changes only: removed newlines before opening braces. 1782 *) 10 sep 2018: added way to inspect metadata chunks without full decoding. 1783 *) 19 aug 2018 (!): fixed color mode bKGD is encoded with and made it use 1784 palette index in case of palette. 1785 *) 10 aug 2018 (!): added support for gAMA, cHRM, sRGB and iCCP chunks. This 1786 change is backwards compatible unless you relied on unknown_chunks for those. 1787 *) 11 jun 2018: less restrictive check for pixel size integer overflow 1788 *) 14 jan 2018: allow optionally ignoring a few more recoverable errors 1789 *) 17 sep 2017: fix memory leak for some encoder input error cases 1790 *) 27 nov 2016: grey+alpha auto color model detection bugfix 1791 *) 18 apr 2016: Changed qsort to custom stable sort (for platforms w/o qsort). 1792 *) 09 apr 2016: Fixed colorkey usage detection, and better file loading (within 1793 the limits of pure C90). 1794 *) 08 dec 2015: Made load_file function return error if file can't be opened. 1795 *) 24 okt 2015: Bugfix with decoding to palette output. 1796 *) 18 apr 2015: Boundary PM instead of just package-merge for faster encoding. 1797 *) 24 aug 2014: Moved to github 1798 *) 23 aug 2014: Reduced needless memory usage of decoder. 1799 *) 28 jun 2014: Removed fix_png setting, always support palette OOB for 1800 simplicity. Made ColorProfile public. 1801 *) 09 jun 2014: Faster encoder by fixing hash bug and more zeros optimization. 1802 *) 22 dec 2013: Power of two windowsize required for optimization. 1803 *) 15 apr 2013: Fixed bug with LAC_ALPHA and color key. 1804 *) 25 mar 2013: Added an optional feature to ignore some PNG errors (fix_png). 1805 *) 11 mar 2013 (!): Bugfix with custom free. Changed from "my" to "lodepng_" 1806 prefix for the custom allocators and made it possible with a new #define to 1807 use custom ones in your project without needing to change lodepng's code. 1808 *) 28 jan 2013: Bugfix with color key. 1809 *) 27 okt 2012: Tweaks in text chunk keyword length error handling. 1810 *) 8 okt 2012 (!): Added new filter strategy (entropy) and new auto color mode. 1811 (no palette). Better deflate tree encoding. New compression tweak settings. 1812 Faster color conversions while decoding. Some internal cleanups. 1813 *) 23 sep 2012: Reduced warnings in Visual Studio a little bit. 1814 *) 1 sep 2012 (!): Removed #define's for giving custom (de)compression functions 1815 and made it work with function pointers instead. 1816 *) 23 jun 2012: Added more filter strategies. Made it easier to use custom alloc 1817 and free functions and toggle #defines from compiler flags. Small fixes. 1818 *) 6 may 2012 (!): Made plugging in custom zlib/deflate functions more flexible. 1819 *) 22 apr 2012 (!): Made interface more consistent, renaming a lot. Removed 1820 redundant C++ codec classes. Reduced amount of structs. Everything changed, 1821 but it is cleaner now imho and functionality remains the same. Also fixed 1822 several bugs and shrunk the implementation code. Made new samples. 1823 *) 6 nov 2011 (!): By default, the encoder now automatically chooses the best 1824 PNG color model and bit depth, based on the amount and type of colors of the 1825 raw image. For this, autoLeaveOutAlphaChannel replaced by auto_choose_color. 1826 *) 9 okt 2011: simpler hash chain implementation for the encoder. 1827 *) 8 sep 2011: lz77 encoder lazy matching instead of greedy matching. 1828 *) 23 aug 2011: tweaked the zlib compression parameters after benchmarking. 1829 A bug with the PNG filtertype heuristic was fixed, so that it chooses much 1830 better ones (it's quite significant). A setting to do an experimental, slow, 1831 brute force search for PNG filter types is added. 1832 *) 17 aug 2011 (!): changed some C zlib related function names. 1833 *) 16 aug 2011: made the code less wide (max 120 characters per line). 1834 *) 17 apr 2011: code cleanup. Bugfixes. Convert low to 16-bit per sample colors. 1835 *) 21 feb 2011: fixed compiling for C90. Fixed compiling with sections disabled. 1836 *) 11 dec 2010: encoding is made faster, based on suggestion by Peter Eastman 1837 to optimize long sequences of zeros. 1838 *) 13 nov 2010: added LodePNG_InfoColor_hasPaletteAlpha and 1839 LodePNG_InfoColor_canHaveAlpha functions for convenience. 1840 *) 7 nov 2010: added LodePNG_error_text function to get error code description. 1841 *) 30 okt 2010: made decoding slightly faster 1842 *) 26 okt 2010: (!) changed some C function and struct names (more consistent). 1843 Reorganized the documentation and the declaration order in the header. 1844 *) 08 aug 2010: only changed some comments and external samples. 1845 *) 05 jul 2010: fixed bug thanks to warnings in the new gcc version. 1846 *) 14 mar 2010: fixed bug where too much memory was allocated for char buffers. 1847 *) 02 sep 2008: fixed bug where it could create empty tree that linux apps could 1848 read by ignoring the problem but windows apps couldn't. 1849 *) 06 jun 2008: added more error checks for out of memory cases. 1850 *) 26 apr 2008: added a few more checks here and there to ensure more safety. 1851 *) 06 mar 2008: crash with encoding of strings fixed 1852 *) 02 feb 2008: support for international text chunks added (iTXt) 1853 *) 23 jan 2008: small cleanups, and #defines to divide code in sections 1854 *) 20 jan 2008: support for unknown chunks allowing using LodePNG for an editor. 1855 *) 18 jan 2008: support for tIME and pHYs chunks added to encoder and decoder. 1856 *) 17 jan 2008: ability to encode and decode compressed zTXt chunks added 1857 Also various fixes, such as in the deflate and the padding bits code. 1858 *) 13 jan 2008: Added ability to encode Adam7-interlaced images. Improved 1859 filtering code of encoder. 1860 *) 07 jan 2008: (!) changed LodePNG to use ISO C90 instead of C++. A 1861 C++ wrapper around this provides an interface almost identical to before. 1862 Having LodePNG be pure ISO C90 makes it more portable. The C and C++ code 1863 are together in these files but it works both for C and C++ compilers. 1864 *) 29 dec 2007: (!) changed most integer types to unsigned int + other tweaks 1865 *) 30 aug 2007: bug fixed which makes this Borland C++ compatible 1866 *) 09 aug 2007: some VS2005 warnings removed again 1867 *) 21 jul 2007: deflate code placed in new namespace separate from zlib code 1868 *) 08 jun 2007: fixed bug with 2- and 4-bit color, and small interlaced images 1869 *) 04 jun 2007: improved support for Visual Studio 2005: crash with accessing 1870 invalid std::vector element [0] fixed, and level 3 and 4 warnings removed 1871 *) 02 jun 2007: made the encoder add a tag with version by default 1872 *) 27 may 2007: zlib and png code separated (but still in the same file), 1873 simple encoder/decoder functions added for more simple usage cases 1874 *) 19 may 2007: minor fixes, some code cleaning, new error added (error 69), 1875 moved some examples from here to lodepng_examples.cpp 1876 *) 12 may 2007: palette decoding bug fixed 1877 *) 24 apr 2007: changed the license from BSD to the zlib license 1878 *) 11 mar 2007: very simple addition: ability to encode bKGD chunks. 1879 *) 04 mar 2007: (!) tEXt chunk related fixes, and support for encoding 1880 palettized PNG images. Plus little interface change with palette and texts. 1881 *) 03 mar 2007: Made it encode dynamic Huffman shorter with repeat codes. 1882 Fixed a bug where the end code of a block had length 0 in the Huffman tree. 1883 *) 26 feb 2007: Huffman compression with dynamic trees (BTYPE 2) now implemented 1884 and supported by the encoder, resulting in smaller PNGs at the output. 1885 *) 27 jan 2007: Made the Adler-32 test faster so that a timewaste is gone. 1886 *) 24 jan 2007: gave encoder an error interface. Added color conversion from any 1887 greyscale type to 8-bit greyscale with or without alpha. 1888 *) 21 jan 2007: (!) Totally changed the interface. It allows more color types 1889 to convert to and is more uniform. See the manual for how it works now. 1890 *) 07 jan 2007: Some cleanup & fixes, and a few changes over the last days: 1891 encode/decode custom tEXt chunks, separate classes for zlib & deflate, and 1892 at last made the decoder give errors for incorrect Adler32 or Crc. 1893 *) 01 jan 2007: Fixed bug with encoding PNGs with less than 8 bits per channel. 1894 *) 29 dec 2006: Added support for encoding images without alpha channel, and 1895 cleaned out code as well as making certain parts faster. 1896 *) 28 dec 2006: Added "Settings" to the encoder. 1897 *) 26 dec 2006: The encoder now does LZ77 encoding and produces much smaller files now. 1898 Removed some code duplication in the decoder. Fixed little bug in an example. 1899 *) 09 dec 2006: (!) Placed output parameters of public functions as first parameter. 1900 Fixed a bug of the decoder with 16-bit per color. 1901 *) 15 okt 2006: Changed documentation structure 1902 *) 09 okt 2006: Encoder class added. It encodes a valid PNG image from the 1903 given image buffer, however for now it's not compressed. 1904 *) 08 sep 2006: (!) Changed to interface with a Decoder class 1905 *) 30 jul 2006: (!) LodePNG_InfoPng , width and height are now retrieved in different 1906 way. Renamed decodePNG to decodePNGGeneric. 1907 *) 29 jul 2006: (!) Changed the interface: image info is now returned as a 1908 struct of type LodePNG::LodePNG_Info, instead of a vector, which was a bit clumsy. 1909 *) 28 jul 2006: Cleaned the code and added new error checks. 1910 Corrected terminology "deflate" into "inflate". 1911 *) 23 jun 2006: Added SDL example in the documentation in the header, this 1912 example allows easy debugging by displaying the PNG and its transparency. 1913 *) 22 jun 2006: (!) Changed way to obtain error value. Added 1914 loadFile function for convenience. Made decodePNG32 faster. 1915 *) 21 jun 2006: (!) Changed type of info vector to unsigned. 1916 Changed position of palette in info vector. Fixed an important bug that 1917 happened on PNGs with an uncompressed block. 1918 *) 16 jun 2006: Internally changed unsigned into unsigned where 1919 needed, and performed some optimizations. 1920 *) 07 jun 2006: (!) Renamed functions to decodePNG and placed them 1921 in LodePNG namespace. Changed the order of the parameters. Rewrote the 1922 documentation in the header. Renamed files to lodepng.cpp and lodepng.h 1923 *) 22 apr 2006: Optimized and improved some code 1924 *) 07 sep 2005: (!) Changed to std::vector interface 1925 *) 12 aug 2005: Initial release (C++, decoder only) 1926 1927 1928 13. contact information 1929 ----------------------- 1930 1931 Feel free to contact me with suggestions, problems, comments, ... concerning 1932 LodePNG. If you encounter a PNG image that doesn't work properly with this 1933 decoder, feel free to send it and I'll use it to find and fix the problem. 1934 1935 My email address is (puzzle the account and domain together with an @ symbol): 1936 Domain: gmail dot com. 1937 Account: lode dot vandevenne. 1938 1939 1940 Copyright (c) 2005-2019 Lode Vandevenne 1941 */ 1942