lodepng.h

00001 /*
00002 LodePNG version 20131222
00003 
00004 Copyright (c) 2005-2013 Lode Vandevenne
00005 
00006 This software is provided 'as-is', without any express or implied
00007 warranty. In no event will the authors be held liable for any damages
00008 arising from the use of this software.
00009 
00010 Permission is granted to anyone to use this software for any purpose,
00011 including commercial applications, and to alter it and redistribute it
00012 freely, subject to the following restrictions:
00013 
00014     1. The origin of this software must not be misrepresented; you must not
00015     claim that you wrote the original software. If you use this software
00016     in a product, an acknowledgment in the product documentation would be
00017     appreciated but is not required.
00018 
00019     2. Altered source versions must be plainly marked as such, and must not be
00020     misrepresented as being the original software.
00021 
00022     3. This notice may not be removed or altered from any source
00023     distribution.
00024 */
00025 
00026 #ifndef LODEPNG_H
00027 #define LODEPNG_H
00028 
00029 #include <string.h> /*for size_t*/
00030 
00031 #ifdef __cplusplus
00032 #include <vector>
00033 #include <string>
00034 #endif /*__cplusplus*/
00035 
00036 
00037 // Settings modified by Embedded Artists
00038 #define LODEPNG_NO_COMPILE_ENCODER
00039 #define LODEPNG_NO_COMPILE_DISK
00040 #define LODEPNG_NO_COMPILE_ANCILLARY_CHUNKS
00041 #define LODEPNG_NO_COMPILE_ERROR_TEXT
00042 #define LODEPNG_NO_COMPILE_CPP
00043 
00044 
00045 /*
00046 The following #defines are used to create code sections. They can be disabled
00047 to disable code sections, which can give faster compile time and smaller binary.
00048 The "NO_COMPILE" defines are designed to be used to pass as defines to the
00049 compiler command to disable them without modifying this header, e.g.
00050 -DLODEPNG_NO_COMPILE_ZLIB for gcc.
00051 */
00052 /*deflate & zlib. If disabled, you must specify alternative zlib functions in
00053 the custom_zlib field of the compress and decompress settings*/
00054 #ifndef LODEPNG_NO_COMPILE_ZLIB
00055 #define LODEPNG_COMPILE_ZLIB
00056 #endif
00057 /*png encoder and png decoder*/
00058 #ifndef LODEPNG_NO_COMPILE_PNG
00059 #define LODEPNG_COMPILE_PNG
00060 #endif
00061 /*deflate&zlib decoder and png decoder*/
00062 #ifndef LODEPNG_NO_COMPILE_DECODER
00063 #define LODEPNG_COMPILE_DECODER
00064 #endif
00065 /*deflate&zlib encoder and png encoder*/
00066 #ifndef LODEPNG_NO_COMPILE_ENCODER
00067 #define LODEPNG_COMPILE_ENCODER
00068 #endif
00069 /*the optional built in harddisk file loading and saving functions*/
00070 #ifndef LODEPNG_NO_COMPILE_DISK
00071 #define LODEPNG_COMPILE_DISK
00072 #endif
00073 /*support for chunks other than IHDR, IDAT, PLTE, tRNS, IEND: ancillary and unknown chunks*/
00074 #ifndef LODEPNG_NO_COMPILE_ANCILLARY_CHUNKS
00075 #define LODEPNG_COMPILE_ANCILLARY_CHUNKS
00076 #endif
00077 /*ability to convert error numerical codes to English text string*/
00078 #ifndef LODEPNG_NO_COMPILE_ERROR_TEXT
00079 #define LODEPNG_COMPILE_ERROR_TEXT
00080 #endif
00081 /*Compile the default allocators (C's free, malloc and realloc). If you disable this,
00082 you can define the functions lodepng_free, lodepng_malloc and lodepng_realloc in your
00083 source files with custom allocators.*/
00084 #ifndef LODEPNG_NO_COMPILE_ALLOCATORS
00085 #define LODEPNG_COMPILE_ALLOCATORS
00086 #endif
00087 /*compile the C++ version (you can disable the C++ wrapper here even when compiling for C++)*/
00088 #ifdef __cplusplus
00089 #ifndef LODEPNG_NO_COMPILE_CPP
00090 #define LODEPNG_COMPILE_CPP
00091 #endif
00092 #endif
00093 
00094 #ifdef LODEPNG_COMPILE_PNG
00095 /*The PNG color types (also used for raw).*/
00096 typedef enum LodePNGColorType
00097 {
00098   LCT_GREY = 0, /*greyscale: 1,2,4,8,16 bit*/
00099   LCT_RGB = 2, /*RGB: 8,16 bit*/
00100   LCT_PALETTE = 3, /*palette: 1,2,4,8 bit*/
00101   LCT_GREY_ALPHA = 4, /*greyscale with alpha: 8,16 bit*/
00102   LCT_RGBA = 6 /*RGB with alpha: 8,16 bit*/
00103 } LodePNGColorType;
00104 
00105 #ifdef LODEPNG_COMPILE_DECODER
00106 /*
00107 Converts PNG data in memory to raw pixel data.
00108 out: Output parameter. Pointer to buffer that will contain the raw pixel data.
00109      After decoding, its size is w * h * (bytes per pixel) bytes larger than
00110      initially. Bytes per pixel depends on colortype and bitdepth.
00111      Must be freed after usage with free(*out).
00112      Note: for 16-bit per channel colors, uses big endian format like PNG does.
00113 w: Output parameter. Pointer to width of pixel data.
00114 h: Output parameter. Pointer to height of pixel data.
00115 in: Memory buffer with the PNG file.
00116 insize: size of the in buffer.
00117 colortype: the desired color type for the raw output image. See explanation on PNG color types.
00118 bitdepth: the desired bit depth for the raw output image. See explanation on PNG color types.
00119 Return value: LodePNG error code (0 means no error).
00120 */
00121 unsigned lodepng_decode_memory(unsigned char** out, unsigned* w, unsigned* h,
00122                                const unsigned char* in, size_t insize,
00123                                LodePNGColorType colortype, unsigned bitdepth);
00124 
00125 /*Same as lodepng_decode_memory, but always decodes to 32-bit RGBA raw image*/
00126 unsigned lodepng_decode32(unsigned char** out, unsigned* w, unsigned* h,
00127                           const unsigned char* in, size_t insize);
00128 
00129 /*Same as lodepng_decode_memory, but always decodes to 24-bit RGB raw image*/
00130 unsigned lodepng_decode24(unsigned char** out, unsigned* w, unsigned* h,
00131                           const unsigned char* in, size_t insize);
00132 
00133 #ifdef LODEPNG_COMPILE_DISK
00134 /*
00135 Load PNG from disk, from file with given name.
00136 Same as the other decode functions, but instead takes a filename as input.
00137 */
00138 unsigned lodepng_decode_file(unsigned char** out, unsigned* w, unsigned* h,
00139                              const char* filename,
00140                              LodePNGColorType colortype, unsigned bitdepth);
00141 
00142 /*Same as lodepng_decode_file, but always decodes to 32-bit RGBA raw image.*/
00143 unsigned lodepng_decode32_file(unsigned char** out, unsigned* w, unsigned* h,
00144                                const char* filename);
00145 
00146 /*Same as lodepng_decode_file, but always decodes to 24-bit RGB raw image.*/
00147 unsigned lodepng_decode24_file(unsigned char** out, unsigned* w, unsigned* h,
00148                                const char* filename);
00149 #endif /*LODEPNG_COMPILE_DISK*/
00150 #endif /*LODEPNG_COMPILE_DECODER*/
00151 
00152 
00153 #ifdef LODEPNG_COMPILE_ENCODER
00154 /*
00155 Converts raw pixel data into a PNG image in memory. The colortype and bitdepth
00156   of the output PNG image cannot be chosen, they are automatically determined
00157   by the colortype, bitdepth and content of the input pixel data.
00158   Note: for 16-bit per channel colors, needs big endian format like PNG does.
00159 out: Output parameter. Pointer to buffer that will contain the PNG image data.
00160      Must be freed after usage with free(*out).
00161 outsize: Output parameter. Pointer to the size in bytes of the out buffer.
00162 image: The raw pixel data to encode. The size of this buffer should be
00163        w * h * (bytes per pixel), bytes per pixel depends on colortype and bitdepth.
00164 w: width of the raw pixel data in pixels.
00165 h: height of the raw pixel data in pixels.
00166 colortype: the color type of the raw input image. See explanation on PNG color types.
00167 bitdepth: the bit depth of the raw input image. See explanation on PNG color types.
00168 Return value: LodePNG error code (0 means no error).
00169 */
00170 unsigned lodepng_encode_memory(unsigned char** out, size_t* outsize,
00171                                const unsigned char* image, unsigned w, unsigned h,
00172                                LodePNGColorType colortype, unsigned bitdepth);
00173 
00174 /*Same as lodepng_encode_memory, but always encodes from 32-bit RGBA raw image.*/
00175 unsigned lodepng_encode32(unsigned char** out, size_t* outsize,
00176                           const unsigned char* image, unsigned w, unsigned h);
00177 
00178 /*Same as lodepng_encode_memory, but always encodes from 24-bit RGB raw image.*/
00179 unsigned lodepng_encode24(unsigned char** out, size_t* outsize,
00180                           const unsigned char* image, unsigned w, unsigned h);
00181 
00182 #ifdef LODEPNG_COMPILE_DISK
00183 /*
00184 Converts raw pixel data into a PNG file on disk.
00185 Same as the other encode functions, but instead takes a filename as output.
00186 NOTE: This overwrites existing files without warning!
00187 */
00188 unsigned lodepng_encode_file(const char* filename,
00189                              const unsigned char* image, unsigned w, unsigned h,
00190                              LodePNGColorType colortype, unsigned bitdepth);
00191 
00192 /*Same as lodepng_encode_file, but always encodes from 32-bit RGBA raw image.*/
00193 unsigned lodepng_encode32_file(const char* filename,
00194                                const unsigned char* image, unsigned w, unsigned h);
00195 
00196 /*Same as lodepng_encode_file, but always encodes from 24-bit RGB raw image.*/
00197 unsigned lodepng_encode24_file(const char* filename,
00198                                const unsigned char* image, unsigned w, unsigned h);
00199 #endif /*LODEPNG_COMPILE_DISK*/
00200 #endif /*LODEPNG_COMPILE_ENCODER*/
00201 
00202 
00203 #ifdef LODEPNG_COMPILE_CPP
00204 namespace lodepng
00205 {
00206 #ifdef LODEPNG_COMPILE_DECODER
00207 /*Same as lodepng_decode_memory, but decodes to an std::vector.*/
00208 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
00209                 const unsigned char* in, size_t insize,
00210                 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
00211 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
00212                 const std::vector<unsigned char>& in,
00213                 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
00214 #ifdef LODEPNG_COMPILE_DISK
00215 /*
00216 Converts PNG file from disk to raw pixel data in memory.
00217 Same as the other decode functions, but instead takes a filename as input.
00218 */
00219 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
00220                 const std::string& filename,
00221                 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
00222 #endif //LODEPNG_COMPILE_DISK
00223 #endif //LODEPNG_COMPILE_DECODER
00224 
00225 #ifdef LODEPNG_COMPILE_ENCODER
00226 /*Same as lodepng_encode_memory, but encodes to an std::vector.*/
00227 unsigned encode(std::vector<unsigned char>& out,
00228                 const unsigned char* in, unsigned w, unsigned h,
00229                 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
00230 unsigned encode(std::vector<unsigned char>& out,
00231                 const std::vector<unsigned char>& in, unsigned w, unsigned h,
00232                 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
00233 #ifdef LODEPNG_COMPILE_DISK
00234 /*
00235 Converts 32-bit RGBA raw pixel data into a PNG file on disk.
00236 Same as the other encode functions, but instead takes a filename as output.
00237 NOTE: This overwrites existing files without warning!
00238 */
00239 unsigned encode(const std::string& filename,
00240                 const unsigned char* in, unsigned w, unsigned h,
00241                 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
00242 unsigned encode(const std::string& filename,
00243                 const std::vector<unsigned char>& in, unsigned w, unsigned h,
00244                 LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
00245 #endif //LODEPNG_COMPILE_DISK
00246 #endif //LODEPNG_COMPILE_ENCODER
00247 } //namespace lodepng
00248 #endif /*LODEPNG_COMPILE_CPP*/
00249 #endif /*LODEPNG_COMPILE_PNG*/
00250 
00251 #ifdef LODEPNG_COMPILE_ERROR_TEXT
00252 /*Returns an English description of the numerical error code.*/
00253 const char* lodepng_error_text(unsigned code);
00254 #endif /*LODEPNG_COMPILE_ERROR_TEXT*/
00255 
00256 #ifdef LODEPNG_COMPILE_DECODER
00257 /*Settings for zlib decompression*/
00258 typedef struct LodePNGDecompressSettings LodePNGDecompressSettings;
00259 struct LodePNGDecompressSettings
00260 {
00261   unsigned ignore_adler32; /*if 1, continue and don't give an error message if the Adler32 checksum is corrupted*/
00262 
00263   /*use custom zlib decoder instead of built in one (default: null)*/
00264   unsigned (*custom_zlib)(unsigned char**, size_t*,
00265                           const unsigned char*, size_t,
00266                           const LodePNGDecompressSettings*);
00267   /*use custom deflate decoder instead of built in one (default: null)
00268   if custom_zlib is used, custom_deflate is ignored since only the built in
00269   zlib function will call custom_deflate*/
00270   unsigned (*custom_inflate)(unsigned char**, size_t*,
00271                              const unsigned char*, size_t,
00272                              const LodePNGDecompressSettings*);
00273 
00274   const void* custom_context; /*optional custom settings for custom functions*/
00275 };
00276 
00277 extern const LodePNGDecompressSettings lodepng_default_decompress_settings;
00278 void lodepng_decompress_settings_init(LodePNGDecompressSettings* settings);
00279 #endif /*LODEPNG_COMPILE_DECODER*/
00280 
00281 #ifdef LODEPNG_COMPILE_ENCODER
00282 /*
00283 Settings for zlib compression. Tweaking these settings tweaks the balance
00284 between speed and compression ratio.
00285 */
00286 typedef struct LodePNGCompressSettings LodePNGCompressSettings;
00287 struct LodePNGCompressSettings /*deflate = compress*/
00288 {
00289   /*LZ77 related settings*/
00290   unsigned btype; /*the block type for LZ (0, 1, 2 or 3, see zlib standard). Should be 2 for proper compression.*/
00291   unsigned use_lz77; /*whether or not to use LZ77. Should be 1 for proper compression.*/
00292   unsigned windowsize; /*must be a power of two <= 32768. higher compresses more but is slower. Typical value: 2048.*/
00293   unsigned minmatch; /*mininum lz77 length. 3 is normally best, 6 can be better for some PNGs. Default: 0*/
00294   unsigned nicematch; /*stop searching if >= this length found. Set to 258 for best compression. Default: 128*/
00295   unsigned lazymatching; /*use lazy matching: better compression but a bit slower. Default: true*/
00296 
00297   /*use custom zlib encoder instead of built in one (default: null)*/
00298   unsigned (*custom_zlib)(unsigned char**, size_t*,
00299                           const unsigned char*, size_t,
00300                           const LodePNGCompressSettings*);
00301   /*use custom deflate encoder instead of built in one (default: null)
00302   if custom_zlib is used, custom_deflate is ignored since only the built in
00303   zlib function will call custom_deflate*/
00304   unsigned (*custom_deflate)(unsigned char**, size_t*,
00305                              const unsigned char*, size_t,
00306                              const LodePNGCompressSettings*);
00307 
00308   const void* custom_context; /*optional custom settings for custom functions*/
00309 };
00310 
00311 extern const LodePNGCompressSettings lodepng_default_compress_settings;
00312 void lodepng_compress_settings_init(LodePNGCompressSettings* settings);
00313 #endif /*LODEPNG_COMPILE_ENCODER*/
00314 
00315 #ifdef LODEPNG_COMPILE_PNG
00316 /*
00317 Color mode of an image. Contains all information required to decode the pixel
00318 bits to RGBA colors. This information is the same as used in the PNG file
00319 format, and is used both for PNG and raw image data in LodePNG.
00320 */
00321 typedef struct LodePNGColorMode
00322 {
00323   /*header (IHDR)*/
00324   LodePNGColorType colortype; /*color type, see PNG standard or documentation further in this header file*/
00325   unsigned bitdepth;  /*bits per sample, see PNG standard or documentation further in this header file*/
00326 
00327   /*
00328   palette (PLTE and tRNS)
00329 
00330   Dynamically allocated with the colors of the palette, including alpha.
00331   When encoding a PNG, to store your colors in the palette of the LodePNGColorMode, first use
00332   lodepng_palette_clear, then for each color use lodepng_palette_add.
00333   If you encode an image without alpha with palette, don't forget to put value 255 in each A byte of the palette.
00334 
00335   When decoding, by default you can ignore this palette, since LodePNG already
00336   fills the palette colors in the pixels of the raw RGBA output.
00337 
00338   The palette is only supported for color type 3.
00339   */
00340   unsigned char* palette; /*palette in RGBARGBA... order. When allocated, must be either 0, or have size 1024*/
00341   size_t palettesize; /*palette size in number of colors (amount of bytes is 4 * palettesize)*/
00342 
00343   /*
00344   transparent color key (tRNS)
00345 
00346   This color uses the same bit depth as the bitdepth value in this struct, which can be 1-bit to 16-bit.
00347   For greyscale PNGs, r, g and b will all 3 be set to the same.
00348 
00349   When decoding, by default you can ignore this information, since LodePNG sets
00350   pixels with this key to transparent already in the raw RGBA output.
00351 
00352   The color key is only supported for color types 0 and 2.
00353   */
00354   unsigned key_defined; /*is a transparent color key given? 0 = false, 1 = true*/
00355   unsigned key_r;       /*red/greyscale component of color key*/
00356   unsigned key_g;       /*green component of color key*/
00357   unsigned key_b;       /*blue component of color key*/
00358 } LodePNGColorMode;
00359 
00360 /*init, cleanup and copy functions to use with this struct*/
00361 void lodepng_color_mode_init(LodePNGColorMode* info);
00362 void lodepng_color_mode_cleanup(LodePNGColorMode* info);
00363 /*return value is error code (0 means no error)*/
00364 unsigned lodepng_color_mode_copy(LodePNGColorMode* dest, const LodePNGColorMode* source);
00365 
00366 void lodepng_palette_clear(LodePNGColorMode* info);
00367 /*add 1 color to the palette*/
00368 unsigned lodepng_palette_add(LodePNGColorMode* info,
00369                              unsigned char r, unsigned char g, unsigned char b, unsigned char a);
00370 
00371 /*get the total amount of bits per pixel, based on colortype and bitdepth in the struct*/
00372 unsigned lodepng_get_bpp(const LodePNGColorMode* info);
00373 /*get the amount of color channels used, based on colortype in the struct.
00374 If a palette is used, it counts as 1 channel.*/
00375 unsigned lodepng_get_channels(const LodePNGColorMode* info);
00376 /*is it a greyscale type? (only colortype 0 or 4)*/
00377 unsigned lodepng_is_greyscale_type(const LodePNGColorMode* info);
00378 /*has it got an alpha channel? (only colortype 2 or 6)*/
00379 unsigned lodepng_is_alpha_type(const LodePNGColorMode* info);
00380 /*has it got a palette? (only colortype 3)*/
00381 unsigned lodepng_is_palette_type(const LodePNGColorMode* info);
00382 /*only returns true if there is a palette and there is a value in the palette with alpha < 255.
00383 Loops through the palette to check this.*/
00384 unsigned lodepng_has_palette_alpha(const LodePNGColorMode* info);
00385 /*
00386 Check if the given color info indicates the possibility of having non-opaque pixels in the PNG image.
00387 Returns true if the image can have translucent or invisible pixels (it still be opaque if it doesn't use such pixels).
00388 Returns false if the image can only have opaque pixels.
00389 In detail, it returns true only if it's a color type with alpha, or has a palette with non-opaque values,
00390 or if "key_defined" is true.
00391 */
00392 unsigned lodepng_can_have_alpha(const LodePNGColorMode* info);
00393 /*Returns the byte size of a raw image buffer with given width, height and color mode*/
00394 size_t lodepng_get_raw_size(unsigned w, unsigned h, const LodePNGColorMode* color);
00395 
00396 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
00397 /*The information of a Time chunk in PNG.*/
00398 typedef struct LodePNGTime
00399 {
00400   unsigned year;    /*2 bytes used (0-65535)*/
00401   unsigned month;   /*1-12*/
00402   unsigned day;     /*1-31*/
00403   unsigned hour;    /*0-23*/
00404   unsigned minute;  /*0-59*/
00405   unsigned second;  /*0-60 (to allow for leap seconds)*/
00406 } LodePNGTime;
00407 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
00408 
00409 /*Information about the PNG image, except pixels, width and height.*/
00410 typedef struct LodePNGInfo
00411 {
00412   /*header (IHDR), palette (PLTE) and transparency (tRNS) chunks*/
00413   unsigned compression_method;/*compression method of the original file. Always 0.*/
00414   unsigned filter_method;     /*filter method of the original file*/
00415   unsigned interlace_method;  /*interlace method of the original file*/
00416   LodePNGColorMode color;     /*color type and bits, palette and transparency of the PNG file*/
00417 
00418 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
00419   /*
00420   suggested background color chunk (bKGD)
00421   This color uses the same color mode as the PNG (except alpha channel), which can be 1-bit to 16-bit.
00422 
00423   For greyscale PNGs, r, g and b will all 3 be set to the same. When encoding
00424   the encoder writes the red one. For palette PNGs: When decoding, the RGB value
00425   will be stored, not a palette index. But when encoding, specify the index of
00426   the palette in background_r, the other two are then ignored.
00427 
00428   The decoder does not use this background color to edit the color of pixels.
00429   */
00430   unsigned background_defined; /*is a suggested background color given?*/
00431   unsigned background_r;       /*red component of suggested background color*/
00432   unsigned background_g;       /*green component of suggested background color*/
00433   unsigned background_b;       /*blue component of suggested background color*/
00434 
00435   /*
00436   non-international text chunks (tEXt and zTXt)
00437 
00438   The char** arrays each contain num strings. The actual messages are in
00439   text_strings, while text_keys are keywords that give a short description what
00440   the actual text represents, e.g. Title, Author, Description, or anything else.
00441 
00442   A keyword is minimum 1 character and maximum 79 characters long. It's
00443   discouraged to use a single line length longer than 79 characters for texts.
00444 
00445   Don't allocate these text buffers yourself. Use the init/cleanup functions
00446   correctly and use lodepng_add_text and lodepng_clear_text.
00447   */
00448   size_t text_num; /*the amount of texts in these char** buffers (there may be more texts in itext)*/
00449   char** text_keys; /*the keyword of a text chunk (e.g. "Comment")*/
00450   char** text_strings; /*the actual text*/
00451 
00452   /*
00453   international text chunks (iTXt)
00454   Similar to the non-international text chunks, but with additional strings
00455   "langtags" and "transkeys".
00456   */
00457   size_t itext_num; /*the amount of international texts in this PNG*/
00458   char** itext_keys; /*the English keyword of the text chunk (e.g. "Comment")*/
00459   char** itext_langtags; /*language tag for this text's language, ISO/IEC 646 string, e.g. ISO 639 language tag*/
00460   char** itext_transkeys; /*keyword translated to the international language - UTF-8 string*/
00461   char** itext_strings; /*the actual international text - UTF-8 string*/
00462 
00463   /*time chunk (tIME)*/
00464   unsigned time_defined; /*set to 1 to make the encoder generate a tIME chunk*/
00465   LodePNGTime time;
00466 
00467   /*phys chunk (pHYs)*/
00468   unsigned phys_defined; /*if 0, there is no pHYs chunk and the values below are undefined, if 1 else there is one*/
00469   unsigned phys_x; /*pixels per unit in x direction*/
00470   unsigned phys_y; /*pixels per unit in y direction*/
00471   unsigned phys_unit; /*may be 0 (unknown unit) or 1 (metre)*/
00472 
00473   /*
00474   unknown chunks
00475   There are 3 buffers, one for each position in the PNG where unknown chunks can appear
00476   each buffer contains all unknown chunks for that position consecutively
00477   The 3 buffers are the unknown chunks between certain critical chunks:
00478   0: IHDR-PLTE, 1: PLTE-IDAT, 2: IDAT-IEND
00479   Do not allocate or traverse this data yourself. Use the chunk traversing functions declared
00480   later, such as lodepng_chunk_next and lodepng_chunk_append, to read/write this struct.
00481   */
00482   unsigned char* unknown_chunks_data[3];
00483   size_t unknown_chunks_size[3]; /*size in bytes of the unknown chunks, given for protection*/
00484 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
00485 } LodePNGInfo;
00486 
00487 /*init, cleanup and copy functions to use with this struct*/
00488 void lodepng_info_init(LodePNGInfo* info);
00489 void lodepng_info_cleanup(LodePNGInfo* info);
00490 /*return value is error code (0 means no error)*/
00491 unsigned lodepng_info_copy(LodePNGInfo* dest, const LodePNGInfo* source);
00492 
00493 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
00494 void lodepng_clear_text(LodePNGInfo* info); /*use this to clear the texts again after you filled them in*/
00495 unsigned lodepng_add_text(LodePNGInfo* info, const char* key, const char* str); /*push back both texts at once*/
00496 
00497 void lodepng_clear_itext(LodePNGInfo* info); /*use this to clear the itexts again after you filled them in*/
00498 unsigned lodepng_add_itext(LodePNGInfo* info, const char* key, const char* langtag,
00499                            const char* transkey, const char* str); /*push back the 4 texts of 1 chunk at once*/
00500 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
00501 
00502 /*
00503 Converts raw buffer from one color type to another color type, based on
00504 LodePNGColorMode structs to describe the input and output color type.
00505 See the reference manual at the end of this header file to see which color conversions are supported.
00506 return value = LodePNG error code (0 if all went ok, an error if the conversion isn't supported)
00507 The out buffer must have size (w * h * bpp + 7) / 8, where bpp is the bits per pixel
00508 of the output color type (lodepng_get_bpp)
00509 The fix_png value works as described in struct LodePNGDecoderSettings.
00510 Note: for 16-bit per channel colors, uses big endian format like PNG does.
00511 */
00512 unsigned lodepng_convert(unsigned char* out, const unsigned char* in,
00513                          LodePNGColorMode* mode_out, const LodePNGColorMode* mode_in,
00514                          unsigned w, unsigned h, unsigned fix_png);
00515 
00516 #ifdef LODEPNG_COMPILE_DECODER
00517 /*
00518 Settings for the decoder. This contains settings for the PNG and the Zlib
00519 decoder, but not the Info settings from the Info structs.
00520 */
00521 typedef struct LodePNGDecoderSettings
00522 {
00523   LodePNGDecompressSettings zlibsettings; /*in here is the setting to ignore Adler32 checksums*/
00524 
00525   unsigned ignore_crc; /*ignore CRC checksums*/
00526   /*
00527   The fix_png setting, if 1, makes the decoder tolerant towards some PNG images
00528   that do not correctly follow the PNG specification. This only supports errors
00529   that are fixable, were found in images that are actually used on the web, and
00530   are silently tolerated by other decoders as well. Currently only one such fix
00531   is implemented: if a palette index is out of bounds given the palette size,
00532   interpret it as opaque black.
00533   By default this value is 0, which makes it stop with an error on such images.
00534   */
00535   unsigned fix_png;
00536   unsigned color_convert; /*whether to convert the PNG to the color type you want. Default: yes*/
00537 
00538 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
00539   unsigned read_text_chunks; /*if false but remember_unknown_chunks is true, they're stored in the unknown chunks*/
00540   /*store all bytes from unknown chunks in the LodePNGInfo (off by default, useful for a png editor)*/
00541   unsigned remember_unknown_chunks;
00542 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
00543 } LodePNGDecoderSettings;
00544 
00545 void lodepng_decoder_settings_init(LodePNGDecoderSettings* settings);
00546 #endif /*LODEPNG_COMPILE_DECODER*/
00547 
00548 #ifdef LODEPNG_COMPILE_ENCODER
00549 /*automatically use color type with less bits per pixel if losslessly possible. Default: AUTO*/
00550 typedef enum LodePNGFilterStrategy
00551 {
00552   /*every filter at zero*/
00553   LFS_ZERO,
00554   /*Use filter that gives minumum sum, as described in the official PNG filter heuristic.*/
00555   LFS_MINSUM,
00556   /*Use the filter type that gives smallest Shannon entropy for this scanline. Depending
00557   on the image, this is better or worse than minsum.*/
00558   LFS_ENTROPY,
00559   /*
00560   Brute-force-search PNG filters by compressing each filter for each scanline.
00561   Experimental, very slow, and only rarely gives better compression than MINSUM.
00562   */
00563   LFS_BRUTE_FORCE,
00564   /*use predefined_filters buffer: you specify the filter type for each scanline*/
00565   LFS_PREDEFINED
00566 } LodePNGFilterStrategy;
00567 
00568 /*automatically use color type with less bits per pixel if losslessly possible. Default: LAC_AUTO*/
00569 typedef enum LodePNGAutoConvert
00570 {
00571   LAC_NO, /*use color type user requested*/
00572   LAC_ALPHA, /*use color type user requested, but if only opaque pixels and RGBA or grey+alpha, use RGB or grey*/
00573   LAC_AUTO, /*use PNG color type that can losslessly represent the uncompressed image the smallest possible*/
00574   /*
00575   like AUTO, but do not choose 1, 2 or 4 bit per pixel types.
00576   sometimes a PNG image compresses worse if less than 8 bits per pixels.
00577   */
00578   LAC_AUTO_NO_NIBBLES,
00579   /*
00580   like AUTO, but never choose palette color type. For small images, encoding
00581   the palette may take more bytes than what is gained. Note that AUTO also
00582   already prevents encoding the palette for extremely small images, but that may
00583   not be sufficient because due to the compression it cannot predict when to
00584   switch.
00585   */
00586   LAC_AUTO_NO_PALETTE,
00587   LAC_AUTO_NO_NIBBLES_NO_PALETTE
00588 } LodePNGAutoConvert;
00589 
00590 
00591 /*
00592 Automatically chooses color type that gives smallest amount of bits in the
00593 output image, e.g. grey if there are only greyscale pixels, palette if there
00594 are less than 256 colors, ...
00595 The auto_convert parameter allows limiting it to not use palette, ...
00596 */
00597 unsigned lodepng_auto_choose_color(LodePNGColorMode* mode_out,
00598                                    const unsigned char* image, unsigned w, unsigned h,
00599                                    const LodePNGColorMode* mode_in,
00600                                    LodePNGAutoConvert auto_convert);
00601 
00602 /*Settings for the encoder.*/
00603 typedef struct LodePNGEncoderSettings
00604 {
00605   LodePNGCompressSettings zlibsettings; /*settings for the zlib encoder, such as window size, ...*/
00606 
00607   LodePNGAutoConvert auto_convert; /*how to automatically choose output PNG color type, if at all*/
00608 
00609   /*If true, follows the official PNG heuristic: if the PNG uses a palette or lower than
00610   8 bit depth, set all filters to zero. Otherwise use the filter_strategy. Note that to
00611   completely follow the official PNG heuristic, filter_palette_zero must be true and
00612   filter_strategy must be LFS_MINSUM*/
00613   unsigned filter_palette_zero;
00614   /*Which filter strategy to use when not using zeroes due to filter_palette_zero.
00615   Set filter_palette_zero to 0 to ensure always using your chosen strategy. Default: LFS_MINSUM*/
00616   LodePNGFilterStrategy filter_strategy;
00617   /*used if filter_strategy is LFS_PREDEFINED. In that case, this must point to a buffer with
00618   the same length as the amount of scanlines in the image, and each value must <= 5. You
00619   have to cleanup this buffer, LodePNG will never free it. Don't forget that filter_palette_zero
00620   must be set to 0 to ensure this is also used on palette or low bitdepth images.*/
00621   const unsigned char* predefined_filters;
00622 
00623   /*force creating a PLTE chunk if colortype is 2 or 6 (= a suggested palette).
00624   If colortype is 3, PLTE is _always_ created.*/
00625   unsigned force_palette;
00626 #ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
00627   /*add LodePNG identifier and version as a text chunk, for debugging*/
00628   unsigned add_id;
00629   /*encode text chunks as zTXt chunks instead of tEXt chunks, and use compression in iTXt chunks*/
00630   unsigned text_compression;
00631 #endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
00632 } LodePNGEncoderSettings;
00633 
00634 void lodepng_encoder_settings_init(LodePNGEncoderSettings* settings);
00635 #endif /*LODEPNG_COMPILE_ENCODER*/
00636 
00637 
00638 #if defined(LODEPNG_COMPILE_DECODER) || defined(LODEPNG_COMPILE_ENCODER)
00639 /*The settings, state and information for extended encoding and decoding.*/
00640 typedef struct LodePNGState
00641 {
00642 #ifdef LODEPNG_COMPILE_DECODER
00643   LodePNGDecoderSettings decoder; /*the decoding settings*/
00644 #endif /*LODEPNG_COMPILE_DECODER*/
00645 #ifdef LODEPNG_COMPILE_ENCODER
00646   LodePNGEncoderSettings encoder; /*the encoding settings*/
00647 #endif /*LODEPNG_COMPILE_ENCODER*/
00648   LodePNGColorMode info_raw; /*specifies the format in which you would like to get the raw pixel buffer*/
00649   LodePNGInfo info_png; /*info of the PNG image obtained after decoding*/
00650   unsigned error;
00651 #ifdef LODEPNG_COMPILE_CPP
00652   //For the lodepng::State subclass.
00653   virtual ~LodePNGState(){}
00654 #endif
00655 } LodePNGState;
00656 
00657 /*init, cleanup and copy functions to use with this struct*/
00658 void lodepng_state_init(LodePNGState* state);
00659 void lodepng_state_cleanup(LodePNGState* state);
00660 void lodepng_state_copy(LodePNGState* dest, const LodePNGState* source);
00661 #endif /* defined(LODEPNG_COMPILE_DECODER) || defined(LODEPNG_COMPILE_ENCODER) */
00662 
00663 #ifdef LODEPNG_COMPILE_DECODER
00664 /*
00665 Same as lodepng_decode_memory, but uses a LodePNGState to allow custom settings and
00666 getting much more information about the PNG image and color mode.
00667 */
00668 unsigned lodepng_decode(unsigned char** out, unsigned* w, unsigned* h,
00669                         LodePNGState* state,
00670                         const unsigned char* in, size_t insize);
00671 
00672 /*
00673 Read the PNG header, but not the actual data. This returns only the information
00674 that is in the header chunk of the PNG, such as width, height and color type. The
00675 information is placed in the info_png field of the LodePNGState.
00676 */
00677 unsigned lodepng_inspect(unsigned* w, unsigned* h,
00678                          LodePNGState* state,
00679                          const unsigned char* in, size_t insize);
00680 #endif /*LODEPNG_COMPILE_DECODER*/
00681 
00682 
00683 #ifdef LODEPNG_COMPILE_ENCODER
00684 /*This function allocates the out buffer with standard malloc and stores the size in *outsize.*/
00685 unsigned lodepng_encode(unsigned char** out, size_t* outsize,
00686                         const unsigned char* image, unsigned w, unsigned h,
00687                         LodePNGState* state);
00688 #endif /*LODEPNG_COMPILE_ENCODER*/
00689 
00690 /*
00691 The lodepng_chunk functions are normally not needed, except to traverse the
00692 unknown chunks stored in the LodePNGInfo struct, or add new ones to it.
00693 It also allows traversing the chunks of an encoded PNG file yourself.
00694 
00695 PNG standard chunk naming conventions:
00696 First byte: uppercase = critical, lowercase = ancillary
00697 Second byte: uppercase = public, lowercase = private
00698 Third byte: must be uppercase
00699 Fourth byte: uppercase = unsafe to copy, lowercase = safe to copy
00700 */
00701 
00702 /*get the length of the data of the chunk. Total chunk length has 12 bytes more.*/
00703 unsigned lodepng_chunk_length(const unsigned char* chunk);
00704 
00705 /*puts the 4-byte type in null terminated string*/
00706 void lodepng_chunk_type(char type[5], const unsigned char* chunk);
00707 
00708 /*check if the type is the given type*/
00709 unsigned char lodepng_chunk_type_equals(const unsigned char* chunk, const char* type);
00710 
00711 /*0: it's one of the critical chunk types, 1: it's an ancillary chunk (see PNG standard)*/
00712 unsigned char lodepng_chunk_ancillary(const unsigned char* chunk);
00713 
00714 /*0: public, 1: private (see PNG standard)*/
00715 unsigned char lodepng_chunk_private(const unsigned char* chunk);
00716 
00717 /*0: the chunk is unsafe to copy, 1: the chunk is safe to copy (see PNG standard)*/
00718 unsigned char lodepng_chunk_safetocopy(const unsigned char* chunk);
00719 
00720 /*get pointer to the data of the chunk, where the input points to the header of the chunk*/
00721 unsigned char* lodepng_chunk_data(unsigned char* chunk);
00722 const unsigned char* lodepng_chunk_data_const(const unsigned char* chunk);
00723 
00724 /*returns 0 if the crc is correct, 1 if it's incorrect (0 for OK as usual!)*/
00725 unsigned lodepng_chunk_check_crc(const unsigned char* chunk);
00726 
00727 /*generates the correct CRC from the data and puts it in the last 4 bytes of the chunk*/
00728 void lodepng_chunk_generate_crc(unsigned char* chunk);
00729 
00730 /*iterate to next chunks. don't use on IEND chunk, as there is no next chunk then*/
00731 unsigned char* lodepng_chunk_next(unsigned char* chunk);
00732 const unsigned char* lodepng_chunk_next_const(const unsigned char* chunk);
00733 
00734 /*
00735 Appends chunk to the data in out. The given chunk should already have its chunk header.
00736 The out variable and outlength are updated to reflect the new reallocated buffer.
00737 Returns error code (0 if it went ok)
00738 */
00739 unsigned lodepng_chunk_append(unsigned char** out, size_t* outlength, const unsigned char* chunk);
00740 
00741 /*
00742 Appends new chunk to out. The chunk to append is given by giving its length, type
00743 and data separately. The type is a 4-letter string.
00744 The out variable and outlength are updated to reflect the new reallocated buffer.
00745 Returne error code (0 if it went ok)
00746 */
00747 unsigned lodepng_chunk_create(unsigned char** out, size_t* outlength, unsigned length,
00748                               const char* type, const unsigned char* data);
00749 
00750 
00751 /*Calculate CRC32 of buffer*/
00752 unsigned lodepng_crc32(const unsigned char* buf, size_t len);
00753 #endif /*LODEPNG_COMPILE_PNG*/
00754 
00755 
00756 #ifdef LODEPNG_COMPILE_ZLIB
00757 /*
00758 This zlib part can be used independently to zlib compress and decompress a
00759 buffer. It cannot be used to create gzip files however, and it only supports the
00760 part of zlib that is required for PNG, it does not support dictionaries.
00761 */
00762 
00763 #ifdef LODEPNG_COMPILE_DECODER
00764 /*Inflate a buffer. Inflate is the decompression step of deflate. Out buffer must be freed after use.*/
00765 unsigned lodepng_inflate(unsigned char** out, size_t* outsize,
00766                          const unsigned char* in, size_t insize,
00767                          const LodePNGDecompressSettings* settings);
00768 
00769 /*
00770 Decompresses Zlib data. Reallocates the out buffer and appends the data. The
00771 data must be according to the zlib specification.
00772 Either, *out must be NULL and *outsize must be 0, or, *out must be a valid
00773 buffer and *outsize its size in bytes. out must be freed by user after usage.
00774 */
00775 unsigned lodepng_zlib_decompress(unsigned char** out, size_t* outsize,
00776                                  const unsigned char* in, size_t insize,
00777                                  const LodePNGDecompressSettings* settings);
00778 #endif /*LODEPNG_COMPILE_DECODER*/
00779 
00780 #ifdef LODEPNG_COMPILE_ENCODER
00781 /*
00782 Compresses data with Zlib. Reallocates the out buffer and appends the data.
00783 Zlib adds a small header and trailer around the deflate data.
00784 The data is output in the format of the zlib specification.
00785 Either, *out must be NULL and *outsize must be 0, or, *out must be a valid
00786 buffer and *outsize its size in bytes. out must be freed by user after usage.
00787 */
00788 unsigned lodepng_zlib_compress(unsigned char** out, size_t* outsize,
00789                                const unsigned char* in, size_t insize,
00790                                const LodePNGCompressSettings* settings);
00791 
00792 /*
00793 Find length-limited Huffman code for given frequencies. This function is in the
00794 public interface only for tests, it's used internally by lodepng_deflate.
00795 */
00796 unsigned lodepng_huffman_code_lengths(unsigned* lengths, const unsigned* frequencies,
00797                                       size_t numcodes, unsigned maxbitlen);
00798 
00799 /*Compress a buffer with deflate. See RFC 1951. Out buffer must be freed after use.*/
00800 unsigned lodepng_deflate(unsigned char** out, size_t* outsize,
00801                          const unsigned char* in, size_t insize,
00802                          const LodePNGCompressSettings* settings);
00803 
00804 #endif /*LODEPNG_COMPILE_ENCODER*/
00805 #endif /*LODEPNG_COMPILE_ZLIB*/
00806 
00807 #ifdef LODEPNG_COMPILE_DISK
00808 /*
00809 Load a file from disk into buffer. The function allocates the out buffer, and
00810 after usage you should free it.
00811 out: output parameter, contains pointer to loaded buffer.
00812 outsize: output parameter, size of the allocated out buffer
00813 filename: the path to the file to load
00814 return value: error code (0 means ok)
00815 */
00816 unsigned lodepng_load_file(unsigned char** out, size_t* outsize, const char* filename);
00817 
00818 /*
00819 Save a file from buffer to disk. Warning, if it exists, this function overwrites
00820 the file without warning!
00821 buffer: the buffer to write
00822 buffersize: size of the buffer to write
00823 filename: the path to the file to save to
00824 return value: error code (0 means ok)
00825 */
00826 unsigned lodepng_save_file(const unsigned char* buffer, size_t buffersize, const char* filename);
00827 #endif /*LODEPNG_COMPILE_DISK*/
00828 
00829 #ifdef LODEPNG_COMPILE_CPP
00830 //The LodePNG C++ wrapper uses std::vectors instead of manually allocated memory buffers.
00831 namespace lodepng
00832 {
00833 #ifdef LODEPNG_COMPILE_PNG
00834 class State : public LodePNGState
00835 {
00836   public:
00837     State();
00838     State(const State& other);
00839     virtual ~State();
00840     State& operator=(const State& other);
00841 };
00842 
00843 #ifdef LODEPNG_COMPILE_DECODER
00844 //Same as other lodepng::decode, but using a State for more settings and information.
00845 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
00846                 State& state,
00847                 const unsigned char* in, size_t insize);
00848 unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
00849                 State& state,
00850                 const std::vector<unsigned char>& in);
00851 #endif /*LODEPNG_COMPILE_DECODER*/
00852 
00853 #ifdef LODEPNG_COMPILE_ENCODER
00854 //Same as other lodepng::encode, but using a State for more settings and information.
00855 unsigned encode(std::vector<unsigned char>& out,
00856                 const unsigned char* in, unsigned w, unsigned h,
00857                 State& state);
00858 unsigned encode(std::vector<unsigned char>& out,
00859                 const std::vector<unsigned char>& in, unsigned w, unsigned h,
00860                 State& state);
00861 #endif /*LODEPNG_COMPILE_ENCODER*/
00862 
00863 #ifdef LODEPNG_COMPILE_DISK
00864 /*
00865 Load a file from disk into an std::vector. If the vector is empty, then either
00866 the file doesn't exist or is an empty file.
00867 */
00868 void load_file(std::vector<unsigned char>& buffer, const std::string& filename);
00869 
00870 /*
00871 Save the binary data in an std::vector to a file on disk. The file is overwritten
00872 without warning.
00873 */
00874 void save_file(const std::vector<unsigned char>& buffer, const std::string& filename);
00875 #endif //LODEPNG_COMPILE_DISK
00876 #endif //LODEPNG_COMPILE_PNG
00877 
00878 #ifdef LODEPNG_COMPILE_ZLIB
00879 #ifdef LODEPNG_COMPILE_DECODER
00880 //Zlib-decompress an unsigned char buffer
00881 unsigned decompress(std::vector<unsigned char>& out, const unsigned char* in, size_t insize,
00882                     const LodePNGDecompressSettings& settings = lodepng_default_decompress_settings);
00883 
00884 //Zlib-decompress an std::vector
00885 unsigned decompress(std::vector<unsigned char>& out, const std::vector<unsigned char>& in,
00886                     const LodePNGDecompressSettings& settings = lodepng_default_decompress_settings);
00887 #endif //LODEPNG_COMPILE_DECODER
00888 
00889 #ifdef LODEPNG_COMPILE_ENCODER
00890 //Zlib-compress an unsigned char buffer
00891 unsigned compress(std::vector<unsigned char>& out, const unsigned char* in, size_t insize,
00892                   const LodePNGCompressSettings& settings = lodepng_default_compress_settings);
00893 
00894 //Zlib-compress an std::vector
00895 unsigned compress(std::vector<unsigned char>& out, const std::vector<unsigned char>& in,
00896                   const LodePNGCompressSettings& settings = lodepng_default_compress_settings);
00897 #endif //LODEPNG_COMPILE_ENCODER
00898 #endif //LODEPNG_COMPILE_ZLIB
00899 } //namespace lodepng
00900 #endif /*LODEPNG_COMPILE_CPP*/
00901 
00902 /*
00903 TODO:
00904 [.] test if there are no memory leaks or security exploits - done a lot but needs to be checked often
00905 [.] check compatibility with vareous compilers  - done but needs to be redone for every newer version
00906 [X] converting color to 16-bit per channel types
00907 [ ] read all public PNG chunk types (but never let the color profile and gamma ones touch RGB values)
00908 [ ] make sure encoder generates no chunks with size > (2^31)-1
00909 [ ] partial decoding (stream processing)
00910 [X] let the "isFullyOpaque" function check color keys and transparent palettes too
00911 [X] better name for the variables "codes", "codesD", "codelengthcodes", "clcl" and "lldl"
00912 [ ] don't stop decoding on errors like 69, 57, 58 (make warnings)
00913 [ ] make option to choose if the raw image with non multiple of 8 bits per scanline should have padding bits or not
00914 [ ] let the C++ wrapper catch exceptions coming from the standard library and return LodePNG error codes
00915 */
00916 
00917 #endif /*LODEPNG_H inclusion guard*/
00918 
00919 /*
00920 LodePNG Documentation
00921 ---------------------
00922 
00923 0. table of contents
00924 --------------------
00925 
00926   1. about
00927    1.1. supported features
00928    1.2. features not supported
00929   2. C and C++ version
00930   3. security
00931   4. decoding
00932   5. encoding
00933   6. color conversions
00934     6.1. PNG color types
00935     6.2. color conversions
00936     6.3. padding bits
00937     6.4. A note about 16-bits per channel and endianness
00938   7. error values
00939   8. chunks and PNG editing
00940   9. compiler support
00941   10. examples
00942    10.1. decoder C++ example
00943    10.2. decoder C example
00944   11. changes
00945   12. contact information
00946 
00947 
00948 1. about
00949 --------
00950 
00951 PNG is a file format to store raster images losslessly with good compression,
00952 supporting different color types and alpha channel.
00953 
00954 LodePNG is a PNG codec according to the Portable Network Graphics (PNG)
00955 Specification (Second Edition) - W3C Recommendation 10 November 2003.
00956 
00957 The specifications used are:
00958 
00959 *) Portable Network Graphics (PNG) Specification (Second Edition):
00960      http://www.w3.org/TR/2003/REC-PNG-20031110
00961 *) RFC 1950 ZLIB Compressed Data Format version 3.3:
00962      http://www.gzip.org/zlib/rfc-zlib.html
00963 *) RFC 1951 DEFLATE Compressed Data Format Specification ver 1.3:
00964      http://www.gzip.org/zlib/rfc-deflate.html
00965 
00966 The most recent version of LodePNG can currently be found at
00967 http://lodev.org/lodepng/
00968 
00969 LodePNG works both in C (ISO C90) and C++, with a C++ wrapper that adds
00970 extra functionality.
00971 
00972 LodePNG exists out of two files:
00973 -lodepng.h: the header file for both C and C++
00974 -lodepng.c(pp): give it the name lodepng.c or lodepng.cpp (or .cc) depending on your usage
00975 
00976 If you want to start using LodePNG right away without reading this doc, get the
00977 examples from the LodePNG website to see how to use it in code, or check the
00978 smaller examples in chapter 13 here.
00979 
00980 LodePNG is simple but only supports the basic requirements. To achieve
00981 simplicity, the following design choices were made: There are no dependencies
00982 on any external library. There are functions to decode and encode a PNG with
00983 a single function call, and extended versions of these functions taking a
00984 LodePNGState struct allowing to specify or get more information. By default
00985 the colors of the raw image are always RGB or RGBA, no matter what color type
00986 the PNG file uses. To read and write files, there are simple functions to
00987 convert the files to/from buffers in memory.
00988 
00989 This all makes LodePNG suitable for loading textures in games, demos and small
00990 programs, ... It's less suitable for full fledged image editors, loading PNGs
00991 over network (it requires all the image data to be available before decoding can
00992 begin), life-critical systems, ...
00993 
00994 1.1. supported features
00995 -----------------------
00996 
00997 The following features are supported by the decoder:
00998 
00999 *) decoding of PNGs with any color type, bit depth and interlace mode, to a 24- or 32-bit color raw image,
01000    or the same color type as the PNG
01001 *) encoding of PNGs, from any raw image to 24- or 32-bit color, or the same color type as the raw image
01002 *) Adam7 interlace and deinterlace for any color type
01003 *) loading the image from harddisk or decoding it from a buffer from other sources than harddisk
01004 *) support for alpha channels, including RGBA color model, translucent palettes and color keying
01005 *) zlib decompression (inflate)
01006 *) zlib compression (deflate)
01007 *) CRC32 and ADLER32 checksums
01008 *) handling of unknown chunks, allowing making a PNG editor that stores custom and unknown chunks.
01009 *) the following chunks are supported (generated/interpreted) by both encoder and decoder:
01010     IHDR: header information
01011     PLTE: color palette
01012     IDAT: pixel data
01013     IEND: the final chunk
01014     tRNS: transparency for palettized images
01015     tEXt: textual information
01016     zTXt: compressed textual information
01017     iTXt: international textual information
01018     bKGD: suggested background color
01019     pHYs: physical dimensions
01020     tIME: modification time
01021 
01022 1.2. features not supported
01023 ---------------------------
01024 
01025 The following features are _not_ supported:
01026 
01027 *) some features needed to make a conformant PNG-Editor might be still missing.
01028 *) partial loading/stream processing. All data must be available and is processed in one call.
01029 *) The following public chunks are not supported but treated as unknown chunks by LodePNG
01030     cHRM, gAMA, iCCP, sRGB, sBIT, hIST, sPLT
01031    Some of these are not supported on purpose: LodePNG wants to provide the RGB values
01032    stored in the pixels, not values modified by system dependent gamma or color models.
01033 
01034 
01035 2. C and C++ version
01036 --------------------
01037 
01038 The C version uses buffers allocated with alloc that you need to free()
01039 yourself. You need to use init and cleanup functions for each struct whenever
01040 using a struct from the C version to avoid exploits and memory leaks.
01041 
01042 The C++ version has extra functions with std::vectors in the interface and the
01043 lodepng::State class which is a LodePNGState with constructor and destructor.
01044 
01045 These files work without modification for both C and C++ compilers because all
01046 the additional C++ code is in "#ifdef __cplusplus" blocks that make C-compilers
01047 ignore it, and the C code is made to compile both with strict ISO C90 and C++.
01048 
01049 To use the C++ version, you need to rename the source file to lodepng.cpp
01050 (instead of lodepng.c), and compile it with a C++ compiler.
01051 
01052 To use the C version, you need to rename the source file to lodepng.c (instead
01053 of lodepng.cpp), and compile it with a C compiler.
01054 
01055 
01056 3. Security
01057 -----------
01058 
01059 Even if carefully designed, it's always possible that LodePNG contains possible
01060 exploits. If you discover one, please let me know, and it will be fixed.
01061 
01062 When using LodePNG, care has to be taken with the C version of LodePNG, as well
01063 as the C-style structs when working with C++. The following conventions are used
01064 for all C-style structs:
01065 
01066 -if a struct has a corresponding init function, always call the init function when making a new one
01067 -if a struct has a corresponding cleanup function, call it before the struct disappears to avoid memory leaks
01068 -if a struct has a corresponding copy function, use the copy function instead of "=".
01069  The destination must also be inited already.
01070 
01071 
01072 4. Decoding
01073 -----------
01074 
01075 Decoding converts a PNG compressed image to a raw pixel buffer.
01076 
01077 Most documentation on using the decoder is at its declarations in the header
01078 above. For C, simple decoding can be done with functions such as
01079 lodepng_decode32, and more advanced decoding can be done with the struct
01080 LodePNGState and lodepng_decode. For C++, all decoding can be done with the
01081 various lodepng::decode functions, and lodepng::State can be used for advanced
01082 features.
01083 
01084 When using the LodePNGState, it uses the following fields for decoding:
01085 *) LodePNGInfo info_png: it stores extra information about the PNG (the input) in here
01086 *) LodePNGColorMode info_raw: here you can say what color mode of the raw image (the output) you want to get
01087 *) LodePNGDecoderSettings decoder: you can specify a few extra settings for the decoder to use
01088 
01089 LodePNGInfo info_png
01090 --------------------
01091 
01092 After decoding, this contains extra information of the PNG image, except the actual
01093 pixels, width and height because these are already gotten directly from the decoder
01094 functions.
01095 
01096 It contains for example the original color type of the PNG image, text comments,
01097 suggested background color, etc... More details about the LodePNGInfo struct are
01098 at its declaration documentation.
01099 
01100 LodePNGColorMode info_raw
01101 -------------------------
01102 
01103 When decoding, here you can specify which color type you want
01104 the resulting raw image to be. If this is different from the colortype of the
01105 PNG, then the decoder will automatically convert the result. This conversion
01106 always works, except if you want it to convert a color PNG to greyscale or to
01107 a palette with missing colors.
01108 
01109 By default, 32-bit color is used for the result.
01110 
01111 LodePNGDecoderSettings decoder
01112 ------------------------------
01113 
01114 The settings can be used to ignore the errors created by invalid CRC and Adler32
01115 chunks, and to disable the decoding of tEXt chunks.
01116 
01117 There's also a setting color_convert, true by default. If false, no conversion
01118 is done, the resulting data will be as it was in the PNG (after decompression)
01119 and you'll have to puzzle the colors of the pixels together yourself using the
01120 color type information in the LodePNGInfo.
01121 
01122 
01123 5. Encoding
01124 -----------
01125 
01126 Encoding converts a raw pixel buffer to a PNG compressed image.
01127 
01128 Most documentation on using the encoder is at its declarations in the header
01129 above. For C, simple encoding can be done with functions such as
01130 lodepng_encode32, and more advanced decoding can be done with the struct
01131 LodePNGState and lodepng_encode. For C++, all encoding can be done with the
01132 various lodepng::encode functions, and lodepng::State can be used for advanced
01133 features.
01134 
01135 Like the decoder, the encoder can also give errors. However it gives less errors
01136 since the encoder input is trusted, the decoder input (a PNG image that could
01137 be forged by anyone) is not trusted.
01138 
01139 When using the LodePNGState, it uses the following fields for encoding:
01140 *) LodePNGInfo info_png: here you specify how you want the PNG (the output) to be.
01141 *) LodePNGColorMode info_raw: here you say what color type of the raw image (the input) has
01142 *) LodePNGEncoderSettings encoder: you can specify a few settings for the encoder to use
01143 
01144 LodePNGInfo info_png
01145 --------------------
01146 
01147 When encoding, you use this the opposite way as when decoding: for encoding,
01148 you fill in the values you want the PNG to have before encoding. By default it's
01149 not needed to specify a color type for the PNG since it's automatically chosen,
01150 but it's possible to choose it yourself given the right settings.
01151 
01152 The encoder will not always exactly match the LodePNGInfo struct you give,
01153 it tries as close as possible. Some things are ignored by the encoder. The
01154 encoder uses, for example, the following settings from it when applicable:
01155 colortype and bitdepth, text chunks, time chunk, the color key, the palette, the
01156 background color, the interlace method, unknown chunks, ...
01157 
01158 When encoding to a PNG with colortype 3, the encoder will generate a PLTE chunk.
01159 If the palette contains any colors for which the alpha channel is not 255 (so
01160 there are translucent colors in the palette), it'll add a tRNS chunk.
01161 
01162 LodePNGColorMode info_raw
01163 -------------------------
01164 
01165 You specify the color type of the raw image that you give to the input here,
01166 including a possible transparent color key and palette you happen to be using in
01167 your raw image data.
01168 
01169 By default, 32-bit color is assumed, meaning your input has to be in RGBA
01170 format with 4 bytes (unsigned chars) per pixel.
01171 
01172 LodePNGEncoderSettings encoder
01173 ------------------------------
01174 
01175 The following settings are supported (some are in sub-structs):
01176 *) auto_convert: when this option is enabled, the encoder will
01177 automatically choose the smallest possible color mode (including color key) that
01178 can encode the colors of all pixels without information loss.
01179 *) btype: the block type for LZ77. 0 = uncompressed, 1 = fixed huffman tree,
01180    2 = dynamic huffman tree (best compression). Should be 2 for proper
01181    compression.
01182 *) use_lz77: whether or not to use LZ77 for compressed block types. Should be
01183    true for proper compression.
01184 *) windowsize: the window size used by the LZ77 encoder (1 - 32768). Has value
01185    2048 by default, but can be set to 32768 for better, but slow, compression.
01186 *) force_palette: if colortype is 2 or 6, you can make the encoder write a PLTE
01187    chunk if force_palette is true. This can used as suggested palette to convert
01188    to by viewers that don't support more than 256 colors (if those still exist)
01189 *) add_id: add text chunk "Encoder: LodePNG <version>" to the image.
01190 *) text_compression: default 1. If 1, it'll store texts as zTXt instead of tEXt chunks.
01191   zTXt chunks use zlib compression on the text. This gives a smaller result on
01192   large texts but a larger result on small texts (such as a single program name).
01193   It's all tEXt or all zTXt though, there's no separate setting per text yet.
01194 
01195 
01196 6. color conversions
01197 --------------------
01198 
01199 An important thing to note about LodePNG, is that the color type of the PNG, and
01200 the color type of the raw image, are completely independent. By default, when
01201 you decode a PNG, you get the result as a raw image in the color type you want,
01202 no matter whether the PNG was encoded with a palette, greyscale or RGBA color.
01203 And if you encode an image, by default LodePNG will automatically choose the PNG
01204 color type that gives good compression based on the values of colors and amount
01205 of colors in the image. It can be configured to let you control it instead as
01206 well, though.
01207 
01208 To be able to do this, LodePNG does conversions from one color mode to another.
01209 It can convert from almost any color type to any other color type, except the
01210 following conversions: RGB to greyscale is not supported, and converting to a
01211 palette when the palette doesn't have a required color is not supported. This is
01212 not supported on purpose: this is information loss which requires a color
01213 reduction algorithm that is beyong the scope of a PNG encoder (yes, RGB to grey
01214 is easy, but there are multiple ways if you want to give some channels more
01215 weight).
01216 
01217 By default, when decoding, you get the raw image in 32-bit RGBA or 24-bit RGB
01218 color, no matter what color type the PNG has. And by default when encoding,
01219 LodePNG automatically picks the best color model for the output PNG, and expects
01220 the input image to be 32-bit RGBA or 24-bit RGB. So, unless you want to control
01221 the color format of the images yourself, you can skip this chapter.
01222 
01223 6.1. PNG color types
01224 --------------------
01225 
01226 A PNG image can have many color types, ranging from 1-bit color to 64-bit color,
01227 as well as palettized color modes. After the zlib decompression and unfiltering
01228 in the PNG image is done, the raw pixel data will have that color type and thus
01229 a certain amount of bits per pixel. If you want the output raw image after
01230 decoding to have another color type, a conversion is done by LodePNG.
01231 
01232 The PNG specification gives the following color types:
01233 
01234 0: greyscale, bit depths 1, 2, 4, 8, 16
01235 2: RGB, bit depths 8 and 16
01236 3: palette, bit depths 1, 2, 4 and 8
01237 4: greyscale with alpha, bit depths 8 and 16
01238 6: RGBA, bit depths 8 and 16
01239 
01240 Bit depth is the amount of bits per pixel per color channel. So the total amount
01241 of bits per pixel is: amount of channels * bitdepth.
01242 
01243 6.2. color conversions
01244 ----------------------
01245 
01246 As explained in the sections about the encoder and decoder, you can specify
01247 color types and bit depths in info_png and info_raw to change the default
01248 behaviour.
01249 
01250 If, when decoding, you want the raw image to be something else than the default,
01251 you need to set the color type and bit depth you want in the LodePNGColorMode,
01252 or the parameters of the simple function of LodePNG you're using.
01253 
01254 If, when encoding, you use another color type than the default in the input
01255 image, you need to specify its color type and bit depth in the LodePNGColorMode
01256 of the raw image, or use the parameters of the simplefunction of LodePNG you're
01257 using.
01258 
01259 If, when encoding, you don't want LodePNG to choose the output PNG color type
01260 but control it yourself, you need to set auto_convert in the encoder settings
01261 to LAC_NONE, and specify the color type you want in the LodePNGInfo of the
01262 encoder.
01263 
01264 If you do any of the above, LodePNG may need to do a color conversion, which
01265 follows the rules below, and may sometimes not be allowed.
01266 
01267 To avoid some confusion:
01268 -the decoder converts from PNG to raw image
01269 -the encoder converts from raw image to PNG
01270 -the colortype and bitdepth in LodePNGColorMode info_raw, are those of the raw image
01271 -the colortype and bitdepth in the color field of LodePNGInfo info_png, are those of the PNG
01272 -when encoding, the color type in LodePNGInfo is ignored if auto_convert
01273  is enabled, it is automatically generated instead
01274 -when decoding, the color type in LodePNGInfo is set by the decoder to that of the original
01275  PNG image, but it can be ignored since the raw image has the color type you requested instead
01276 -if the color type of the LodePNGColorMode and PNG image aren't the same, a conversion
01277  between the color types is done if the color types are supported. If it is not
01278  supported, an error is returned. If the types are the same, no conversion is done.
01279 -even though some conversions aren't supported, LodePNG supports loading PNGs from any
01280  colortype and saving PNGs to any colortype, sometimes it just requires preparing
01281  the raw image correctly before encoding.
01282 -both encoder and decoder use the same color converter.
01283 
01284 Non supported color conversions:
01285 -color to greyscale: no error is thrown, but the result will look ugly because
01286 only the red channel is taken
01287 -anything, to palette when that palette does not have that color in it: in this
01288 case an error is thrown
01289 
01290 Supported color conversions:
01291 -anything to 8-bit RGB, 8-bit RGBA, 16-bit RGB, 16-bit RGBA
01292 -any grey or grey+alpha, to grey or grey+alpha
01293 -anything to a palette, as long as the palette has the requested colors in it
01294 -removing alpha channel
01295 -higher to smaller bitdepth, and vice versa
01296 
01297 If you want no color conversion to be done:
01298 -In the encoder, you can make it save a PNG with any color type by giving the
01299 raw color mode and LodePNGInfo the same color mode, and setting auto_convert to
01300 LAC_NO.
01301 -In the decoder, you can make it store the pixel data in the same color type
01302 as the PNG has, by setting the color_convert setting to false. Settings in
01303 info_raw are then ignored.
01304 
01305 The function lodepng_convert does the color conversion. It is available in the
01306 interface but normally isn't needed since the encoder and decoder already call
01307 it.
01308 
01309 6.3. padding bits
01310 -----------------
01311 
01312 In the PNG file format, if a less than 8-bit per pixel color type is used and the scanlines
01313 have a bit amount that isn't a multiple of 8, then padding bits are used so that each
01314 scanline starts at a fresh byte. But that is NOT true for the LodePNG raw input and output.
01315 The raw input image you give to the encoder, and the raw output image you get from the decoder
01316 will NOT have these padding bits, e.g. in the case of a 1-bit image with a width
01317 of 7 pixels, the first pixel of the second scanline will the the 8th bit of the first byte,
01318 not the first bit of a new byte.
01319 
01320 6.4. A note about 16-bits per channel and endianness
01321 ----------------------------------------------------
01322 
01323 LodePNG uses unsigned char arrays for 16-bit per channel colors too, just like
01324 for any other color format. The 16-bit values are stored in big endian (most
01325 significant byte first) in these arrays. This is the opposite order of the
01326 little endian used by x86 CPU's.
01327 
01328 LodePNG always uses big endian because the PNG file format does so internally.
01329 Conversions to other formats than PNG uses internally are not supported by
01330 LodePNG on purpose, there are myriads of formats, including endianness of 16-bit
01331 colors, the order in which you store R, G, B and A, and so on. Supporting and
01332 converting to/from all that is outside the scope of LodePNG.
01333 
01334 This may mean that, depending on your use case, you may want to convert the big
01335 endian output of LodePNG to little endian with a for loop. This is certainly not
01336 always needed, many applications and libraries support big endian 16-bit colors
01337 anyway, but it means you cannot simply cast the unsigned char* buffer to an
01338 unsigned short* buffer on x86 CPUs.
01339 
01340 
01341 7. error values
01342 ---------------
01343 
01344 All functions in LodePNG that return an error code, return 0 if everything went
01345 OK, or a non-zero code if there was an error.
01346 
01347 The meaning of the LodePNG error values can be retrieved with the function
01348 lodepng_error_text: given the numerical error code, it returns a description
01349 of the error in English as a string.
01350 
01351 Check the implementation of lodepng_error_text to see the meaning of each code.
01352 
01353 
01354 8. chunks and PNG editing
01355 -------------------------
01356 
01357 If you want to add extra chunks to a PNG you encode, or use LodePNG for a PNG
01358 editor that should follow the rules about handling of unknown chunks, or if your
01359 program is able to read other types of chunks than the ones handled by LodePNG,
01360 then that's possible with the chunk functions of LodePNG.
01361 
01362 A PNG chunk has the following layout:
01363 
01364 4 bytes length
01365 4 bytes type name
01366 length bytes data
01367 4 bytes CRC
01368 
01369 8.1. iterating through chunks
01370 -----------------------------
01371 
01372 If you have a buffer containing the PNG image data, then the first chunk (the
01373 IHDR chunk) starts at byte number 8 of that buffer. The first 8 bytes are the
01374 signature of the PNG and are not part of a chunk. But if you start at byte 8
01375 then you have a chunk, and can check the following things of it.
01376 
01377 NOTE: none of these functions check for memory buffer boundaries. To avoid
01378 exploits, always make sure the buffer contains all the data of the chunks.
01379 When using lodepng_chunk_next, make sure the returned value is within the
01380 allocated memory.
01381 
01382 unsigned lodepng_chunk_length(const unsigned char* chunk):
01383 
01384 Get the length of the chunk's data. The total chunk length is this length + 12.
01385 
01386 void lodepng_chunk_type(char type[5], const unsigned char* chunk):
01387 unsigned char lodepng_chunk_type_equals(const unsigned char* chunk, const char* type):
01388 
01389 Get the type of the chunk or compare if it's a certain type
01390 
01391 unsigned char lodepng_chunk_critical(const unsigned char* chunk):
01392 unsigned char lodepng_chunk_private(const unsigned char* chunk):
01393 unsigned char lodepng_chunk_safetocopy(const unsigned char* chunk):
01394 
01395 Check if the chunk is critical in the PNG standard (only IHDR, PLTE, IDAT and IEND are).
01396 Check if the chunk is private (public chunks are part of the standard, private ones not).
01397 Check if the chunk is safe to copy. If it's not, then, when modifying data in a critical
01398 chunk, unsafe to copy chunks of the old image may NOT be saved in the new one if your
01399 program doesn't handle that type of unknown chunk.
01400 
01401 unsigned char* lodepng_chunk_data(unsigned char* chunk):
01402 const unsigned char* lodepng_chunk_data_const(const unsigned char* chunk):
01403 
01404 Get a pointer to the start of the data of the chunk.
01405 
01406 unsigned lodepng_chunk_check_crc(const unsigned char* chunk):
01407 void lodepng_chunk_generate_crc(unsigned char* chunk):
01408 
01409 Check if the crc is correct or generate a correct one.
01410 
01411 unsigned char* lodepng_chunk_next(unsigned char* chunk):
01412 const unsigned char* lodepng_chunk_next_const(const unsigned char* chunk):
01413 
01414 Iterate to the next chunk. This works if you have a buffer with consecutive chunks. Note that these
01415 functions do no boundary checking of the allocated data whatsoever, so make sure there is enough
01416 data available in the buffer to be able to go to the next chunk.
01417 
01418 unsigned lodepng_chunk_append(unsigned char** out, size_t* outlength, const unsigned char* chunk):
01419 unsigned lodepng_chunk_create(unsigned char** out, size_t* outlength, unsigned length,
01420                               const char* type, const unsigned char* data):
01421 
01422 These functions are used to create new chunks that are appended to the data in *out that has
01423 length *outlength. The append function appends an existing chunk to the new data. The create
01424 function creates a new chunk with the given parameters and appends it. Type is the 4-letter
01425 name of the chunk.
01426 
01427 8.2. chunks in info_png
01428 -----------------------
01429 
01430 The LodePNGInfo struct contains fields with the unknown chunk in it. It has 3
01431 buffers (each with size) to contain 3 types of unknown chunks:
01432 the ones that come before the PLTE chunk, the ones that come between the PLTE
01433 and the IDAT chunks, and the ones that come after the IDAT chunks.
01434 It's necessary to make the distionction between these 3 cases because the PNG
01435 standard forces to keep the ordering of unknown chunks compared to the critical
01436 chunks, but does not force any other ordering rules.
01437 
01438 info_png.unknown_chunks_data[0] is the chunks before PLTE
01439 info_png.unknown_chunks_data[1] is the chunks after PLTE, before IDAT
01440 info_png.unknown_chunks_data[2] is the chunks after IDAT
01441 
01442 The chunks in these 3 buffers can be iterated through and read by using the same
01443 way described in the previous subchapter.
01444 
01445 When using the decoder to decode a PNG, you can make it store all unknown chunks
01446 if you set the option settings.remember_unknown_chunks to 1. By default, this
01447 option is off (0).
01448 
01449 The encoder will always encode unknown chunks that are stored in the info_png.
01450 If you need it to add a particular chunk that isn't known by LodePNG, you can
01451 use lodepng_chunk_append or lodepng_chunk_create to the chunk data in
01452 info_png.unknown_chunks_data[x].
01453 
01454 Chunks that are known by LodePNG should not be added in that way. E.g. to make
01455 LodePNG add a bKGD chunk, set background_defined to true and add the correct
01456 parameters there instead.
01457 
01458 
01459 9. compiler support
01460 -------------------
01461 
01462 No libraries other than the current standard C library are needed to compile
01463 LodePNG. For the C++ version, only the standard C++ library is needed on top.
01464 Add the files lodepng.c(pp) and lodepng.h to your project, include
01465 lodepng.h where needed, and your program can read/write PNG files.
01466 
01467 If performance is important, use optimization when compiling! For both the
01468 encoder and decoder, this makes a large difference.
01469 
01470 Make sure that LodePNG is compiled with the same compiler of the same version
01471 and with the same settings as the rest of the program, or the interfaces with
01472 std::vectors and std::strings in C++ can be incompatible.
01473 
01474 CHAR_BITS must be 8 or higher, because LodePNG uses unsigned chars for octets.
01475 
01476 *) gcc and g++
01477 
01478 LodePNG is developed in gcc so this compiler is natively supported. It gives no
01479 warnings with compiler options "-Wall -Wextra -pedantic -ansi", with gcc and g++
01480 version 4.7.1 on Linux, 32-bit and 64-bit.
01481 
01482 *) Mingw
01483 
01484 The Mingw compiler (a port of gcc) for Windows is fully supported by LodePNG.
01485 
01486 *) Visual Studio 2005 and up, Visual C++ Express Edition 2005 and up
01487 
01488 Visual Studio may give warnings about 'fopen' being deprecated. A multiplatform library
01489 can't support the proposed Visual Studio alternative however, so LodePNG keeps using
01490 fopen. If you don't want to see the deprecated warnings, put this on top of lodepng.h
01491 before the inclusions:
01492 #define _CRT_SECURE_NO_DEPRECATE
01493 
01494 Other than the above warnings, LodePNG should be warning-free with warning
01495 level 3 (W3). Warning level 4 (W4) will give warnings about integer conversions.
01496 I'm not planning to resolve these warnings. To get rid of them, let Visual
01497 Studio use warning level W3 for lodepng.cpp only: right click lodepng.cpp,
01498 Properties, C/C++, General, Warning Level: Level 3 (/W3).
01499 
01500 Visual Studio may want "stdafx.h" files to be included in each source file and
01501 give an error "unexpected end of file while looking for precompiled header".
01502 That is not standard C++ and will not be added to the stock LodePNG. You can
01503 disable it for lodepng.cpp only by right clicking it, Properties, C/C++,
01504 Precompiled Headers, and set it to Not Using Precompiled Headers there.
01505 
01506 *) Visual Studio 6.0
01507 
01508 LodePNG support for Visual Studio 6.0 is not guaranteed because VS6 doesn't
01509 follow the C++ standard correctly.
01510 
01511 *) Comeau C/C++
01512 
01513 Vesion 20070107 compiles without problems on the Comeau C/C++ Online Test Drive
01514 at http://www.comeaucomputing.com/tryitout in both C90 and C++ mode.
01515 
01516 *) Compilers on Macintosh
01517 
01518 LodePNG has been reported to work both with the gcc and LLVM for Macintosh, both
01519 for C and C++.
01520 
01521 *) Other Compilers
01522 
01523 If you encounter problems on other compilers, feel free to let me know and I may
01524 try to fix it if the compiler is modern standards complient.
01525 
01526 
01527 10. examples
01528 ------------
01529 
01530 This decoder example shows the most basic usage of LodePNG. More complex
01531 examples can be found on the LodePNG website.
01532 
01533 10.1. decoder C++ example
01534 -------------------------
01535 
01536 #include "lodepng.h"
01537 #include <iostream>
01538 
01539 int main(int argc, char *argv[])
01540 {
01541   const char* filename = argc > 1 ? argv[1] : "test.png";
01542 
01543   //load and decode
01544   std::vector<unsigned char> image;
01545   unsigned width, height;
01546   unsigned error = lodepng::decode(image, width, height, filename);
01547 
01548   //if there's an error, display it
01549   if(error) std::cout << "decoder error " << error << ": " << lodepng_error_text(error) << std::endl;
01550 
01551   //the pixels are now in the vector "image", 4 bytes per pixel, ordered RGBARGBA..., use it as texture, draw it, ...
01552 }
01553 
01554 10.2. decoder C example
01555 -----------------------
01556 
01557 #include "lodepng.h"
01558 
01559 int main(int argc, char *argv[])
01560 {
01561   unsigned error;
01562   unsigned char* image;
01563   size_t width, height;
01564   const char* filename = argc > 1 ? argv[1] : "test.png";
01565 
01566   error = lodepng_decode32_file(&image, &width, &height, filename);
01567 
01568   if(error) printf("decoder error %u: %s\n", error, lodepng_error_text(error));
01569 
01570   / * use image here * /
01571 
01572   free(image);
01573   return 0;
01574 }
01575 
01576 
01577 11. changes
01578 -----------
01579 
01580 The version number of LodePNG is the date of the change given in the format
01581 yyyymmdd.
01582 
01583 Some changes aren't backwards compatible. Those are indicated with a (!)
01584 symbol.
01585 
01586 *) 22 dec 2013: Power of two windowsize required for optimization.
01587 *) 15 apr 2013: Fixed bug with LAC_ALPHA and color key.
01588 *) 25 mar 2013: Added an optional feature to ignore some PNG errors (fix_png).
01589 *) 11 mar 2013 (!): Bugfix with custom free. Changed from "my" to "lodepng_"
01590     prefix for the custom allocators and made it possible with a new #define to
01591     use custom ones in your project without needing to change lodepng's code.
01592 *) 28 jan 2013: Bugfix with color key.
01593 *) 27 okt 2012: Tweaks in text chunk keyword length error handling.
01594 *) 8 okt 2012 (!): Added new filter strategy (entropy) and new auto color mode.
01595     (no palette). Better deflate tree encoding. New compression tweak settings.
01596     Faster color conversions while decoding. Some internal cleanups.
01597 *) 23 sep 2012: Reduced warnings in Visual Studio a little bit.
01598 *) 1 sep 2012 (!): Removed #define's for giving custom (de)compression functions
01599     and made it work with function pointers instead.
01600 *) 23 jun 2012: Added more filter strategies. Made it easier to use custom alloc
01601     and free functions and toggle #defines from compiler flags. Small fixes.
01602 *) 6 may 2012 (!): Made plugging in custom zlib/deflate functions more flexible.
01603 *) 22 apr 2012 (!): Made interface more consistent, renaming a lot. Removed
01604     redundant C++ codec classes. Reduced amount of structs. Everything changed,
01605     but it is cleaner now imho and functionality remains the same. Also fixed
01606     several bugs and shrinked the implementation code. Made new samples.
01607 *) 6 nov 2011 (!): By default, the encoder now automatically chooses the best
01608     PNG color model and bit depth, based on the amount and type of colors of the
01609     raw image. For this, autoLeaveOutAlphaChannel replaced by auto_choose_color.
01610 *) 9 okt 2011: simpler hash chain implementation for the encoder.
01611 *) 8 sep 2011: lz77 encoder lazy matching instead of greedy matching.
01612 *) 23 aug 2011: tweaked the zlib compression parameters after benchmarking.
01613     A bug with the PNG filtertype heuristic was fixed, so that it chooses much
01614     better ones (it's quite significant). A setting to do an experimental, slow,
01615     brute force search for PNG filter types is added.
01616 *) 17 aug 2011 (!): changed some C zlib related function names.
01617 *) 16 aug 2011: made the code less wide (max 120 characters per line).
01618 *) 17 apr 2011: code cleanup. Bugfixes. Convert low to 16-bit per sample colors.
01619 *) 21 feb 2011: fixed compiling for C90. Fixed compiling with sections disabled.
01620 *) 11 dec 2010: encoding is made faster, based on suggestion by Peter Eastman
01621     to optimize long sequences of zeros.
01622 *) 13 nov 2010: added LodePNG_InfoColor_hasPaletteAlpha and
01623     LodePNG_InfoColor_canHaveAlpha functions for convenience.
01624 *) 7 nov 2010: added LodePNG_error_text function to get error code description.
01625 *) 30 okt 2010: made decoding slightly faster
01626 *) 26 okt 2010: (!) changed some C function and struct names (more consistent).
01627      Reorganized the documentation and the declaration order in the header.
01628 *) 08 aug 2010: only changed some comments and external samples.
01629 *) 05 jul 2010: fixed bug thanks to warnings in the new gcc version.
01630 *) 14 mar 2010: fixed bug where too much memory was allocated for char buffers.
01631 *) 02 sep 2008: fixed bug where it could create empty tree that linux apps could
01632     read by ignoring the problem but windows apps couldn't.
01633 *) 06 jun 2008: added more error checks for out of memory cases.
01634 *) 26 apr 2008: added a few more checks here and there to ensure more safety.
01635 *) 06 mar 2008: crash with encoding of strings fixed
01636 *) 02 feb 2008: support for international text chunks added (iTXt)
01637 *) 23 jan 2008: small cleanups, and #defines to divide code in sections
01638 *) 20 jan 2008: support for unknown chunks allowing using LodePNG for an editor.
01639 *) 18 jan 2008: support for tIME and pHYs chunks added to encoder and decoder.
01640 *) 17 jan 2008: ability to encode and decode compressed zTXt chunks added
01641     Also vareous fixes, such as in the deflate and the padding bits code.
01642 *) 13 jan 2008: Added ability to encode Adam7-interlaced images. Improved
01643     filtering code of encoder.
01644 *) 07 jan 2008: (!) changed LodePNG to use ISO C90 instead of C++. A
01645     C++ wrapper around this provides an interface almost identical to before.
01646     Having LodePNG be pure ISO C90 makes it more portable. The C and C++ code
01647     are together in these files but it works both for C and C++ compilers.
01648 *) 29 dec 2007: (!) changed most integer types to unsigned int + other tweaks
01649 *) 30 aug 2007: bug fixed which makes this Borland C++ compatible
01650 *) 09 aug 2007: some VS2005 warnings removed again
01651 *) 21 jul 2007: deflate code placed in new namespace separate from zlib code
01652 *) 08 jun 2007: fixed bug with 2- and 4-bit color, and small interlaced images
01653 *) 04 jun 2007: improved support for Visual Studio 2005: crash with accessing
01654     invalid std::vector element [0] fixed, and level 3 and 4 warnings removed
01655 *) 02 jun 2007: made the encoder add a tag with version by default
01656 *) 27 may 2007: zlib and png code separated (but still in the same file),
01657     simple encoder/decoder functions added for more simple usage cases
01658 *) 19 may 2007: minor fixes, some code cleaning, new error added (error 69),
01659     moved some examples from here to lodepng_examples.cpp
01660 *) 12 may 2007: palette decoding bug fixed
01661 *) 24 apr 2007: changed the license from BSD to the zlib license
01662 *) 11 mar 2007: very simple addition: ability to encode bKGD chunks.
01663 *) 04 mar 2007: (!) tEXt chunk related fixes, and support for encoding
01664     palettized PNG images. Plus little interface change with palette and texts.
01665 *) 03 mar 2007: Made it encode dynamic Huffman shorter with repeat codes.
01666     Fixed a bug where the end code of a block had length 0 in the Huffman tree.
01667 *) 26 feb 2007: Huffman compression with dynamic trees (BTYPE 2) now implemented
01668     and supported by the encoder, resulting in smaller PNGs at the output.
01669 *) 27 jan 2007: Made the Adler-32 test faster so that a timewaste is gone.
01670 *) 24 jan 2007: gave encoder an error interface. Added color conversion from any
01671     greyscale type to 8-bit greyscale with or without alpha.
01672 *) 21 jan 2007: (!) Totally changed the interface. It allows more color types
01673     to convert to and is more uniform. See the manual for how it works now.
01674 *) 07 jan 2007: Some cleanup & fixes, and a few changes over the last days:
01675     encode/decode custom tEXt chunks, separate classes for zlib & deflate, and
01676     at last made the decoder give errors for incorrect Adler32 or Crc.
01677 *) 01 jan 2007: Fixed bug with encoding PNGs with less than 8 bits per channel.
01678 *) 29 dec 2006: Added support for encoding images without alpha channel, and
01679     cleaned out code as well as making certain parts faster.
01680 *) 28 dec 2006: Added "Settings" to the encoder.
01681 *) 26 dec 2006: The encoder now does LZ77 encoding and produces much smaller files now.
01682     Removed some code duplication in the decoder. Fixed little bug in an example.
01683 *) 09 dec 2006: (!) Placed output parameters of public functions as first parameter.
01684     Fixed a bug of the decoder with 16-bit per color.
01685 *) 15 okt 2006: Changed documentation structure
01686 *) 09 okt 2006: Encoder class added. It encodes a valid PNG image from the
01687     given image buffer, however for now it's not compressed.
01688 *) 08 sep 2006: (!) Changed to interface with a Decoder class
01689 *) 30 jul 2006: (!) LodePNG_InfoPng , width and height are now retrieved in different
01690     way. Renamed decodePNG to decodePNGGeneric.
01691 *) 29 jul 2006: (!) Changed the interface: image info is now returned as a
01692     struct of type LodePNG::LodePNG_Info, instead of a vector, which was a bit clumsy.
01693 *) 28 jul 2006: Cleaned the code and added new error checks.
01694     Corrected terminology "deflate" into "inflate".
01695 *) 23 jun 2006: Added SDL example in the documentation in the header, this
01696     example allows easy debugging by displaying the PNG and its transparency.
01697 *) 22 jun 2006: (!) Changed way to obtain error value. Added
01698     loadFile function for convenience. Made decodePNG32 faster.
01699 *) 21 jun 2006: (!) Changed type of info vector to unsigned.
01700     Changed position of palette in info vector. Fixed an important bug that
01701     happened on PNGs with an uncompressed block.
01702 *) 16 jun 2006: Internally changed unsigned into unsigned where
01703     needed, and performed some optimizations.
01704 *) 07 jun 2006: (!) Renamed functions to decodePNG and placed them
01705     in LodePNG namespace. Changed the order of the parameters. Rewrote the
01706     documentation in the header. Renamed files to lodepng.cpp and lodepng.h
01707 *) 22 apr 2006: Optimized and improved some code
01708 *) 07 sep 2005: (!) Changed to std::vector interface
01709 *) 12 aug 2005: Initial release (C++, decoder only)
01710 
01711 
01712 12. contact information
01713 -----------------------
01714 
01715 Feel free to contact me with suggestions, problems, comments, ... concerning
01716 LodePNG. If you encounter a PNG image that doesn't work properly with this
01717 decoder, feel free to send it and I'll use it to find and fix the problem.
01718 
01719 My email address is (puzzle the account and domain together with an @ symbol):
01720 Domain: gmail dot com.
01721 Account: lode dot vandevenne.
01722 
01723 
01724 Copyright (c) 2005-2013 Lode Vandevenne
01725 */