зеркало из https://github.com/stride3d/msdfgen.git
1760 строки
80 KiB
C++
1760 строки
80 KiB
C++
/*
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LodePNG version 20160418
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Copyright (c) 2005-2016 Lode Vandevenne
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be
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misrepresented as being the original software.
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3. This notice may not be removed or altered from any source
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distribution.
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*/
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#ifndef LODEPNG_H
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#define LODEPNG_H
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#include <string.h> /*for size_t*/
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extern const char* LODEPNG_VERSION_STRING;
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/*
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The following #defines are used to create code sections. They can be disabled
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to disable code sections, which can give faster compile time and smaller binary.
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The "NO_COMPILE" defines are designed to be used to pass as defines to the
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compiler command to disable them without modifying this header, e.g.
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-DLODEPNG_NO_COMPILE_ZLIB for gcc.
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In addition to those below, you can also define LODEPNG_NO_COMPILE_CRC to
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allow implementing a custom lodepng_crc32.
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*/
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/*deflate & zlib. If disabled, you must specify alternative zlib functions in
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the custom_zlib field of the compress and decompress settings*/
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#ifndef LODEPNG_NO_COMPILE_ZLIB
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#define LODEPNG_COMPILE_ZLIB
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#endif
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/*png encoder and png decoder*/
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#ifndef LODEPNG_NO_COMPILE_PNG
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#define LODEPNG_COMPILE_PNG
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#endif
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/*deflate&zlib decoder and png decoder*/
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#ifndef LODEPNG_NO_COMPILE_DECODER
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#define LODEPNG_COMPILE_DECODER
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#endif
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/*deflate&zlib encoder and png encoder*/
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#ifndef LODEPNG_NO_COMPILE_ENCODER
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#define LODEPNG_COMPILE_ENCODER
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#endif
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/*the optional built in harddisk file loading and saving functions*/
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#ifndef LODEPNG_NO_COMPILE_DISK
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#define LODEPNG_COMPILE_DISK
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#endif
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/*support for chunks other than IHDR, IDAT, PLTE, tRNS, IEND: ancillary and unknown chunks*/
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#ifndef LODEPNG_NO_COMPILE_ANCILLARY_CHUNKS
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#define LODEPNG_COMPILE_ANCILLARY_CHUNKS
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#endif
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/*ability to convert error numerical codes to English text string*/
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#ifndef LODEPNG_NO_COMPILE_ERROR_TEXT
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#define LODEPNG_COMPILE_ERROR_TEXT
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#endif
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/*Compile the default allocators (C's free, malloc and realloc). If you disable this,
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you can define the functions lodepng_free, lodepng_malloc and lodepng_realloc in your
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source files with custom allocators.*/
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#ifndef LODEPNG_NO_COMPILE_ALLOCATORS
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#define LODEPNG_COMPILE_ALLOCATORS
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#endif
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/*compile the C++ version (you can disable the C++ wrapper here even when compiling for C++)*/
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#ifdef __cplusplus
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#ifndef LODEPNG_NO_COMPILE_CPP
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#define LODEPNG_COMPILE_CPP
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#endif
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#endif
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#ifdef LODEPNG_COMPILE_CPP
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#include <vector>
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#include <string>
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#endif /*LODEPNG_COMPILE_CPP*/
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#ifdef LODEPNG_COMPILE_PNG
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/*The PNG color types (also used for raw).*/
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typedef enum LodePNGColorType
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{
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LCT_GREY = 0, /*greyscale: 1,2,4,8,16 bit*/
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LCT_RGB = 2, /*RGB: 8,16 bit*/
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LCT_PALETTE = 3, /*palette: 1,2,4,8 bit*/
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LCT_GREY_ALPHA = 4, /*greyscale with alpha: 8,16 bit*/
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LCT_RGBA = 6 /*RGB with alpha: 8,16 bit*/
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} LodePNGColorType;
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#ifdef LODEPNG_COMPILE_DECODER
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/*
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Converts PNG data in memory to raw pixel data.
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out: Output parameter. Pointer to buffer that will contain the raw pixel data.
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After decoding, its size is w * h * (bytes per pixel) bytes larger than
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initially. Bytes per pixel depends on colortype and bitdepth.
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Must be freed after usage with free(*out).
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Note: for 16-bit per channel colors, uses big endian format like PNG does.
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w: Output parameter. Pointer to width of pixel data.
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h: Output parameter. Pointer to height of pixel data.
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in: Memory buffer with the PNG file.
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insize: size of the in buffer.
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colortype: the desired color type for the raw output image. See explanation on PNG color types.
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bitdepth: the desired bit depth for the raw output image. See explanation on PNG color types.
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Return value: LodePNG error code (0 means no error).
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*/
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unsigned lodepng_decode_memory(unsigned char** out, unsigned* w, unsigned* h,
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const unsigned char* in, size_t insize,
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LodePNGColorType colortype, unsigned bitdepth);
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/*Same as lodepng_decode_memory, but always decodes to 32-bit RGBA raw image*/
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unsigned lodepng_decode32(unsigned char** out, unsigned* w, unsigned* h,
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const unsigned char* in, size_t insize);
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/*Same as lodepng_decode_memory, but always decodes to 24-bit RGB raw image*/
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unsigned lodepng_decode24(unsigned char** out, unsigned* w, unsigned* h,
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const unsigned char* in, size_t insize);
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#ifdef LODEPNG_COMPILE_DISK
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/*
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Load PNG from disk, from file with given name.
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Same as the other decode functions, but instead takes a filename as input.
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*/
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unsigned lodepng_decode_file(unsigned char** out, unsigned* w, unsigned* h,
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const char* filename,
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LodePNGColorType colortype, unsigned bitdepth);
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/*Same as lodepng_decode_file, but always decodes to 32-bit RGBA raw image.*/
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unsigned lodepng_decode32_file(unsigned char** out, unsigned* w, unsigned* h,
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const char* filename);
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/*Same as lodepng_decode_file, but always decodes to 24-bit RGB raw image.*/
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unsigned lodepng_decode24_file(unsigned char** out, unsigned* w, unsigned* h,
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const char* filename);
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#endif /*LODEPNG_COMPILE_DISK*/
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#endif /*LODEPNG_COMPILE_DECODER*/
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#ifdef LODEPNG_COMPILE_ENCODER
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/*
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Converts raw pixel data into a PNG image in memory. The colortype and bitdepth
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of the output PNG image cannot be chosen, they are automatically determined
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by the colortype, bitdepth and content of the input pixel data.
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Note: for 16-bit per channel colors, needs big endian format like PNG does.
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out: Output parameter. Pointer to buffer that will contain the PNG image data.
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Must be freed after usage with free(*out).
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outsize: Output parameter. Pointer to the size in bytes of the out buffer.
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image: The raw pixel data to encode. The size of this buffer should be
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w * h * (bytes per pixel), bytes per pixel depends on colortype and bitdepth.
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w: width of the raw pixel data in pixels.
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h: height of the raw pixel data in pixels.
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colortype: the color type of the raw input image. See explanation on PNG color types.
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bitdepth: the bit depth of the raw input image. See explanation on PNG color types.
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Return value: LodePNG error code (0 means no error).
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*/
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unsigned lodepng_encode_memory(unsigned char** out, size_t* outsize,
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const unsigned char* image, unsigned w, unsigned h,
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LodePNGColorType colortype, unsigned bitdepth);
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/*Same as lodepng_encode_memory, but always encodes from 32-bit RGBA raw image.*/
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unsigned lodepng_encode32(unsigned char** out, size_t* outsize,
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const unsigned char* image, unsigned w, unsigned h);
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/*Same as lodepng_encode_memory, but always encodes from 24-bit RGB raw image.*/
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unsigned lodepng_encode24(unsigned char** out, size_t* outsize,
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const unsigned char* image, unsigned w, unsigned h);
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#ifdef LODEPNG_COMPILE_DISK
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/*
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Converts raw pixel data into a PNG file on disk.
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Same as the other encode functions, but instead takes a filename as output.
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NOTE: This overwrites existing files without warning!
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*/
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unsigned lodepng_encode_file(const char* filename,
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const unsigned char* image, unsigned w, unsigned h,
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LodePNGColorType colortype, unsigned bitdepth);
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/*Same as lodepng_encode_file, but always encodes from 32-bit RGBA raw image.*/
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unsigned lodepng_encode32_file(const char* filename,
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const unsigned char* image, unsigned w, unsigned h);
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/*Same as lodepng_encode_file, but always encodes from 24-bit RGB raw image.*/
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unsigned lodepng_encode24_file(const char* filename,
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const unsigned char* image, unsigned w, unsigned h);
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#endif /*LODEPNG_COMPILE_DISK*/
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#endif /*LODEPNG_COMPILE_ENCODER*/
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#ifdef LODEPNG_COMPILE_CPP
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namespace lodepng
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{
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#ifdef LODEPNG_COMPILE_DECODER
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/*Same as lodepng_decode_memory, but decodes to an std::vector. The colortype
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is the format to output the pixels to. Default is RGBA 8-bit per channel.*/
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unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
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const unsigned char* in, size_t insize,
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LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
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unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
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const std::vector<unsigned char>& in,
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LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
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#ifdef LODEPNG_COMPILE_DISK
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/*
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Converts PNG file from disk to raw pixel data in memory.
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Same as the other decode functions, but instead takes a filename as input.
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*/
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unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
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const std::string& filename,
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LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
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#endif /* LODEPNG_COMPILE_DISK */
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#endif /* LODEPNG_COMPILE_DECODER */
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#ifdef LODEPNG_COMPILE_ENCODER
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/*Same as lodepng_encode_memory, but encodes to an std::vector. colortype
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is that of the raw input data. The output PNG color type will be auto chosen.*/
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unsigned encode(std::vector<unsigned char>& out,
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const unsigned char* in, unsigned w, unsigned h,
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LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
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unsigned encode(std::vector<unsigned char>& out,
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const std::vector<unsigned char>& in, unsigned w, unsigned h,
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LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
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#ifdef LODEPNG_COMPILE_DISK
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/*
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Converts 32-bit RGBA raw pixel data into a PNG file on disk.
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Same as the other encode functions, but instead takes a filename as output.
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NOTE: This overwrites existing files without warning!
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*/
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unsigned encode(const std::string& filename,
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const unsigned char* in, unsigned w, unsigned h,
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LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
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unsigned encode(const std::string& filename,
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const std::vector<unsigned char>& in, unsigned w, unsigned h,
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LodePNGColorType colortype = LCT_RGBA, unsigned bitdepth = 8);
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#endif /* LODEPNG_COMPILE_DISK */
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#endif /* LODEPNG_COMPILE_ENCODER */
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} /* namespace lodepng */
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#endif /*LODEPNG_COMPILE_CPP*/
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#endif /*LODEPNG_COMPILE_PNG*/
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#ifdef LODEPNG_COMPILE_ERROR_TEXT
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/*Returns an English description of the numerical error code.*/
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const char* lodepng_error_text(unsigned code);
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#endif /*LODEPNG_COMPILE_ERROR_TEXT*/
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#ifdef LODEPNG_COMPILE_DECODER
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/*Settings for zlib decompression*/
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typedef struct LodePNGDecompressSettings LodePNGDecompressSettings;
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struct LodePNGDecompressSettings
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{
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unsigned ignore_adler32; /*if 1, continue and don't give an error message if the Adler32 checksum is corrupted*/
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/*use custom zlib decoder instead of built in one (default: null)*/
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unsigned (*custom_zlib)(unsigned char**, size_t*,
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const unsigned char*, size_t,
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const LodePNGDecompressSettings*);
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/*use custom deflate decoder instead of built in one (default: null)
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if custom_zlib is used, custom_deflate is ignored since only the built in
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zlib function will call custom_deflate*/
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unsigned (*custom_inflate)(unsigned char**, size_t*,
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const unsigned char*, size_t,
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const LodePNGDecompressSettings*);
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const void* custom_context; /*optional custom settings for custom functions*/
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};
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extern const LodePNGDecompressSettings lodepng_default_decompress_settings;
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void lodepng_decompress_settings_init(LodePNGDecompressSettings* settings);
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#endif /*LODEPNG_COMPILE_DECODER*/
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#ifdef LODEPNG_COMPILE_ENCODER
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/*
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Settings for zlib compression. Tweaking these settings tweaks the balance
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between speed and compression ratio.
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*/
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typedef struct LodePNGCompressSettings LodePNGCompressSettings;
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struct LodePNGCompressSettings /*deflate = compress*/
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{
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/*LZ77 related settings*/
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unsigned btype; /*the block type for LZ (0, 1, 2 or 3, see zlib standard). Should be 2 for proper compression.*/
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unsigned use_lz77; /*whether or not to use LZ77. Should be 1 for proper compression.*/
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unsigned windowsize; /*must be a power of two <= 32768. higher compresses more but is slower. Default value: 2048.*/
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unsigned minmatch; /*mininum lz77 length. 3 is normally best, 6 can be better for some PNGs. Default: 0*/
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unsigned nicematch; /*stop searching if >= this length found. Set to 258 for best compression. Default: 128*/
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unsigned lazymatching; /*use lazy matching: better compression but a bit slower. Default: true*/
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/*use custom zlib encoder instead of built in one (default: null)*/
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unsigned (*custom_zlib)(unsigned char**, size_t*,
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const unsigned char*, size_t,
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const LodePNGCompressSettings*);
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/*use custom deflate encoder instead of built in one (default: null)
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if custom_zlib is used, custom_deflate is ignored since only the built in
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zlib function will call custom_deflate*/
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unsigned (*custom_deflate)(unsigned char**, size_t*,
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const unsigned char*, size_t,
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const LodePNGCompressSettings*);
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const void* custom_context; /*optional custom settings for custom functions*/
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};
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extern const LodePNGCompressSettings lodepng_default_compress_settings;
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void lodepng_compress_settings_init(LodePNGCompressSettings* settings);
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#endif /*LODEPNG_COMPILE_ENCODER*/
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#ifdef LODEPNG_COMPILE_PNG
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/*
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Color mode of an image. Contains all information required to decode the pixel
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bits to RGBA colors. This information is the same as used in the PNG file
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format, and is used both for PNG and raw image data in LodePNG.
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*/
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typedef struct LodePNGColorMode
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{
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/*header (IHDR)*/
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LodePNGColorType colortype; /*color type, see PNG standard or documentation further in this header file*/
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unsigned bitdepth; /*bits per sample, see PNG standard or documentation further in this header file*/
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/*
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palette (PLTE and tRNS)
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Dynamically allocated with the colors of the palette, including alpha.
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When encoding a PNG, to store your colors in the palette of the LodePNGColorMode, first use
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lodepng_palette_clear, then for each color use lodepng_palette_add.
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If you encode an image without alpha with palette, don't forget to put value 255 in each A byte of the palette.
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When decoding, by default you can ignore this palette, since LodePNG already
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fills the palette colors in the pixels of the raw RGBA output.
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The palette is only supported for color type 3.
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*/
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unsigned char* palette; /*palette in RGBARGBA... order. When allocated, must be either 0, or have size 1024*/
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size_t palettesize; /*palette size in number of colors (amount of bytes is 4 * palettesize)*/
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/*
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transparent color key (tRNS)
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This color uses the same bit depth as the bitdepth value in this struct, which can be 1-bit to 16-bit.
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For greyscale PNGs, r, g and b will all 3 be set to the same.
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When decoding, by default you can ignore this information, since LodePNG sets
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pixels with this key to transparent already in the raw RGBA output.
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The color key is only supported for color types 0 and 2.
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*/
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unsigned key_defined; /*is a transparent color key given? 0 = false, 1 = true*/
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unsigned key_r; /*red/greyscale component of color key*/
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unsigned key_g; /*green component of color key*/
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unsigned key_b; /*blue component of color key*/
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} LodePNGColorMode;
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/*init, cleanup and copy functions to use with this struct*/
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void lodepng_color_mode_init(LodePNGColorMode* info);
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void lodepng_color_mode_cleanup(LodePNGColorMode* info);
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/*return value is error code (0 means no error)*/
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unsigned lodepng_color_mode_copy(LodePNGColorMode* dest, const LodePNGColorMode* source);
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void lodepng_palette_clear(LodePNGColorMode* info);
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/*add 1 color to the palette*/
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unsigned lodepng_palette_add(LodePNGColorMode* info,
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unsigned char r, unsigned char g, unsigned char b, unsigned char a);
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/*get the total amount of bits per pixel, based on colortype and bitdepth in the struct*/
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unsigned lodepng_get_bpp(const LodePNGColorMode* info);
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/*get the amount of color channels used, based on colortype in the struct.
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If a palette is used, it counts as 1 channel.*/
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unsigned lodepng_get_channels(const LodePNGColorMode* info);
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/*is it a greyscale type? (only colortype 0 or 4)*/
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unsigned lodepng_is_greyscale_type(const LodePNGColorMode* info);
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/*has it got an alpha channel? (only colortype 2 or 6)*/
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unsigned lodepng_is_alpha_type(const LodePNGColorMode* info);
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/*has it got a palette? (only colortype 3)*/
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unsigned lodepng_is_palette_type(const LodePNGColorMode* info);
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/*only returns true if there is a palette and there is a value in the palette with alpha < 255.
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Loops through the palette to check this.*/
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unsigned lodepng_has_palette_alpha(const LodePNGColorMode* info);
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/*
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Check if the given color info indicates the possibility of having non-opaque pixels in the PNG image.
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Returns true if the image can have translucent or invisible pixels (it still be opaque if it doesn't use such pixels).
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Returns false if the image can only have opaque pixels.
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In detail, it returns true only if it's a color type with alpha, or has a palette with non-opaque values,
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or if "key_defined" is true.
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*/
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unsigned lodepng_can_have_alpha(const LodePNGColorMode* info);
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/*Returns the byte size of a raw image buffer with given width, height and color mode*/
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size_t lodepng_get_raw_size(unsigned w, unsigned h, const LodePNGColorMode* color);
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#ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
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/*The information of a Time chunk in PNG.*/
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typedef struct LodePNGTime
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{
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unsigned year; /*2 bytes used (0-65535)*/
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unsigned month; /*1-12*/
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unsigned day; /*1-31*/
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unsigned hour; /*0-23*/
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unsigned minute; /*0-59*/
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unsigned second; /*0-60 (to allow for leap seconds)*/
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} LodePNGTime;
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#endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
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/*Information about the PNG image, except pixels, width and height.*/
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typedef struct LodePNGInfo
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{
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/*header (IHDR), palette (PLTE) and transparency (tRNS) chunks*/
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unsigned compression_method;/*compression method of the original file. Always 0.*/
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unsigned filter_method; /*filter method of the original file*/
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unsigned interlace_method; /*interlace method of the original file*/
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|
LodePNGColorMode color; /*color type and bits, palette and transparency of the PNG file*/
|
|
|
|
#ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
|
|
/*
|
|
suggested background color chunk (bKGD)
|
|
This color uses the same color mode as the PNG (except alpha channel), which can be 1-bit to 16-bit.
|
|
|
|
For greyscale PNGs, r, g and b will all 3 be set to the same. When encoding
|
|
the encoder writes the red one. For palette PNGs: When decoding, the RGB value
|
|
will be stored, not a palette index. But when encoding, specify the index of
|
|
the palette in background_r, the other two are then ignored.
|
|
|
|
The decoder does not use this background color to edit the color of pixels.
|
|
*/
|
|
unsigned background_defined; /*is a suggested background color given?*/
|
|
unsigned background_r; /*red component of suggested background color*/
|
|
unsigned background_g; /*green component of suggested background color*/
|
|
unsigned background_b; /*blue component of suggested background color*/
|
|
|
|
/*
|
|
non-international text chunks (tEXt and zTXt)
|
|
|
|
The char** arrays each contain num strings. The actual messages are in
|
|
text_strings, while text_keys are keywords that give a short description what
|
|
the actual text represents, e.g. Title, Author, Description, or anything else.
|
|
|
|
A keyword is minimum 1 character and maximum 79 characters long. It's
|
|
discouraged to use a single line length longer than 79 characters for texts.
|
|
|
|
Don't allocate these text buffers yourself. Use the init/cleanup functions
|
|
correctly and use lodepng_add_text and lodepng_clear_text.
|
|
*/
|
|
size_t text_num; /*the amount of texts in these char** buffers (there may be more texts in itext)*/
|
|
char** text_keys; /*the keyword of a text chunk (e.g. "Comment")*/
|
|
char** text_strings; /*the actual text*/
|
|
|
|
/*
|
|
international text chunks (iTXt)
|
|
Similar to the non-international text chunks, but with additional strings
|
|
"langtags" and "transkeys".
|
|
*/
|
|
size_t itext_num; /*the amount of international texts in this PNG*/
|
|
char** itext_keys; /*the English keyword of the text chunk (e.g. "Comment")*/
|
|
char** itext_langtags; /*language tag for this text's language, ISO/IEC 646 string, e.g. ISO 639 language tag*/
|
|
char** itext_transkeys; /*keyword translated to the international language - UTF-8 string*/
|
|
char** itext_strings; /*the actual international text - UTF-8 string*/
|
|
|
|
/*time chunk (tIME)*/
|
|
unsigned time_defined; /*set to 1 to make the encoder generate a tIME chunk*/
|
|
LodePNGTime time;
|
|
|
|
/*phys chunk (pHYs)*/
|
|
unsigned phys_defined; /*if 0, there is no pHYs chunk and the values below are undefined, if 1 else there is one*/
|
|
unsigned phys_x; /*pixels per unit in x direction*/
|
|
unsigned phys_y; /*pixels per unit in y direction*/
|
|
unsigned phys_unit; /*may be 0 (unknown unit) or 1 (metre)*/
|
|
|
|
/*
|
|
unknown chunks
|
|
There are 3 buffers, one for each position in the PNG where unknown chunks can appear
|
|
each buffer contains all unknown chunks for that position consecutively
|
|
The 3 buffers are the unknown chunks between certain critical chunks:
|
|
0: IHDR-PLTE, 1: PLTE-IDAT, 2: IDAT-IEND
|
|
Do not allocate or traverse this data yourself. Use the chunk traversing functions declared
|
|
later, such as lodepng_chunk_next and lodepng_chunk_append, to read/write this struct.
|
|
*/
|
|
unsigned char* unknown_chunks_data[3];
|
|
size_t unknown_chunks_size[3]; /*size in bytes of the unknown chunks, given for protection*/
|
|
#endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
|
|
} LodePNGInfo;
|
|
|
|
/*init, cleanup and copy functions to use with this struct*/
|
|
void lodepng_info_init(LodePNGInfo* info);
|
|
void lodepng_info_cleanup(LodePNGInfo* info);
|
|
/*return value is error code (0 means no error)*/
|
|
unsigned lodepng_info_copy(LodePNGInfo* dest, const LodePNGInfo* source);
|
|
|
|
#ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
|
|
void lodepng_clear_text(LodePNGInfo* info); /*use this to clear the texts again after you filled them in*/
|
|
unsigned lodepng_add_text(LodePNGInfo* info, const char* key, const char* str); /*push back both texts at once*/
|
|
|
|
void lodepng_clear_itext(LodePNGInfo* info); /*use this to clear the itexts again after you filled them in*/
|
|
unsigned lodepng_add_itext(LodePNGInfo* info, const char* key, const char* langtag,
|
|
const char* transkey, const char* str); /*push back the 4 texts of 1 chunk at once*/
|
|
#endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
|
|
|
|
/*
|
|
Converts raw buffer from one color type to another color type, based on
|
|
LodePNGColorMode structs to describe the input and output color type.
|
|
See the reference manual at the end of this header file to see which color conversions are supported.
|
|
return value = LodePNG error code (0 if all went ok, an error if the conversion isn't supported)
|
|
The out buffer must have size (w * h * bpp + 7) / 8, where bpp is the bits per pixel
|
|
of the output color type (lodepng_get_bpp).
|
|
For < 8 bpp images, there should not be padding bits at the end of scanlines.
|
|
For 16-bit per channel colors, uses big endian format like PNG does.
|
|
Return value is LodePNG error code
|
|
*/
|
|
unsigned lodepng_convert(unsigned char* out, const unsigned char* in,
|
|
const LodePNGColorMode* mode_out, const LodePNGColorMode* mode_in,
|
|
unsigned w, unsigned h);
|
|
|
|
#ifdef LODEPNG_COMPILE_DECODER
|
|
/*
|
|
Settings for the decoder. This contains settings for the PNG and the Zlib
|
|
decoder, but not the Info settings from the Info structs.
|
|
*/
|
|
typedef struct LodePNGDecoderSettings
|
|
{
|
|
LodePNGDecompressSettings zlibsettings; /*in here is the setting to ignore Adler32 checksums*/
|
|
|
|
unsigned ignore_crc; /*ignore CRC checksums*/
|
|
|
|
unsigned color_convert; /*whether to convert the PNG to the color type you want. Default: yes*/
|
|
|
|
#ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
|
|
unsigned read_text_chunks; /*if false but remember_unknown_chunks is true, they're stored in the unknown chunks*/
|
|
/*store all bytes from unknown chunks in the LodePNGInfo (off by default, useful for a png editor)*/
|
|
unsigned remember_unknown_chunks;
|
|
#endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
|
|
} LodePNGDecoderSettings;
|
|
|
|
void lodepng_decoder_settings_init(LodePNGDecoderSettings* settings);
|
|
#endif /*LODEPNG_COMPILE_DECODER*/
|
|
|
|
#ifdef LODEPNG_COMPILE_ENCODER
|
|
/*automatically use color type with less bits per pixel if losslessly possible. Default: AUTO*/
|
|
typedef enum LodePNGFilterStrategy
|
|
{
|
|
/*every filter at zero*/
|
|
LFS_ZERO,
|
|
/*Use filter that gives minimum sum, as described in the official PNG filter heuristic.*/
|
|
LFS_MINSUM,
|
|
/*Use the filter type that gives smallest Shannon entropy for this scanline. Depending
|
|
on the image, this is better or worse than minsum.*/
|
|
LFS_ENTROPY,
|
|
/*
|
|
Brute-force-search PNG filters by compressing each filter for each scanline.
|
|
Experimental, very slow, and only rarely gives better compression than MINSUM.
|
|
*/
|
|
LFS_BRUTE_FORCE,
|
|
/*use predefined_filters buffer: you specify the filter type for each scanline*/
|
|
LFS_PREDEFINED
|
|
} LodePNGFilterStrategy;
|
|
|
|
/*Gives characteristics about the colors of the image, which helps decide which color model to use for encoding.
|
|
Used internally by default if "auto_convert" is enabled. Public because it's useful for custom algorithms.*/
|
|
typedef struct LodePNGColorProfile
|
|
{
|
|
unsigned colored; /*not greyscale*/
|
|
unsigned key; /*if true, image is not opaque. Only if true and alpha is false, color key is possible.*/
|
|
unsigned short key_r; /*these values are always in 16-bit bitdepth in the profile*/
|
|
unsigned short key_g;
|
|
unsigned short key_b;
|
|
unsigned alpha; /*alpha channel or alpha palette required*/
|
|
unsigned numcolors; /*amount of colors, up to 257. Not valid if bits == 16.*/
|
|
unsigned char palette[1024]; /*Remembers up to the first 256 RGBA colors, in no particular order*/
|
|
unsigned bits; /*bits per channel (not for palette). 1,2 or 4 for greyscale only. 16 if 16-bit per channel required.*/
|
|
} LodePNGColorProfile;
|
|
|
|
void lodepng_color_profile_init(LodePNGColorProfile* profile);
|
|
|
|
/*Get a LodePNGColorProfile of the image.*/
|
|
unsigned lodepng_get_color_profile(LodePNGColorProfile* profile,
|
|
const unsigned char* image, unsigned w, unsigned h,
|
|
const LodePNGColorMode* mode_in);
|
|
/*The function LodePNG uses internally to decide the PNG color with auto_convert.
|
|
Chooses an optimal color model, e.g. grey if only grey pixels, palette if < 256 colors, ...*/
|
|
unsigned lodepng_auto_choose_color(LodePNGColorMode* mode_out,
|
|
const unsigned char* image, unsigned w, unsigned h,
|
|
const LodePNGColorMode* mode_in);
|
|
|
|
/*Settings for the encoder.*/
|
|
typedef struct LodePNGEncoderSettings
|
|
{
|
|
LodePNGCompressSettings zlibsettings; /*settings for the zlib encoder, such as window size, ...*/
|
|
|
|
unsigned auto_convert; /*automatically choose output PNG color type. Default: true*/
|
|
|
|
/*If true, follows the official PNG heuristic: if the PNG uses a palette or lower than
|
|
8 bit depth, set all filters to zero. Otherwise use the filter_strategy. Note that to
|
|
completely follow the official PNG heuristic, filter_palette_zero must be true and
|
|
filter_strategy must be LFS_MINSUM*/
|
|
unsigned filter_palette_zero;
|
|
/*Which filter strategy to use when not using zeroes due to filter_palette_zero.
|
|
Set filter_palette_zero to 0 to ensure always using your chosen strategy. Default: LFS_MINSUM*/
|
|
LodePNGFilterStrategy filter_strategy;
|
|
/*used if filter_strategy is LFS_PREDEFINED. In that case, this must point to a buffer with
|
|
the same length as the amount of scanlines in the image, and each value must <= 5. You
|
|
have to cleanup this buffer, LodePNG will never free it. Don't forget that filter_palette_zero
|
|
must be set to 0 to ensure this is also used on palette or low bitdepth images.*/
|
|
const unsigned char* predefined_filters;
|
|
|
|
/*force creating a PLTE chunk if colortype is 2 or 6 (= a suggested palette).
|
|
If colortype is 3, PLTE is _always_ created.*/
|
|
unsigned force_palette;
|
|
#ifdef LODEPNG_COMPILE_ANCILLARY_CHUNKS
|
|
/*add LodePNG identifier and version as a text chunk, for debugging*/
|
|
unsigned add_id;
|
|
/*encode text chunks as zTXt chunks instead of tEXt chunks, and use compression in iTXt chunks*/
|
|
unsigned text_compression;
|
|
#endif /*LODEPNG_COMPILE_ANCILLARY_CHUNKS*/
|
|
} LodePNGEncoderSettings;
|
|
|
|
void lodepng_encoder_settings_init(LodePNGEncoderSettings* settings);
|
|
#endif /*LODEPNG_COMPILE_ENCODER*/
|
|
|
|
|
|
#if defined(LODEPNG_COMPILE_DECODER) || defined(LODEPNG_COMPILE_ENCODER)
|
|
/*The settings, state and information for extended encoding and decoding.*/
|
|
typedef struct LodePNGState
|
|
{
|
|
#ifdef LODEPNG_COMPILE_DECODER
|
|
LodePNGDecoderSettings decoder; /*the decoding settings*/
|
|
#endif /*LODEPNG_COMPILE_DECODER*/
|
|
#ifdef LODEPNG_COMPILE_ENCODER
|
|
LodePNGEncoderSettings encoder; /*the encoding settings*/
|
|
#endif /*LODEPNG_COMPILE_ENCODER*/
|
|
LodePNGColorMode info_raw; /*specifies the format in which you would like to get the raw pixel buffer*/
|
|
LodePNGInfo info_png; /*info of the PNG image obtained after decoding*/
|
|
unsigned error;
|
|
#ifdef LODEPNG_COMPILE_CPP
|
|
/* For the lodepng::State subclass. */
|
|
virtual ~LodePNGState(){}
|
|
#endif
|
|
} LodePNGState;
|
|
|
|
/*init, cleanup and copy functions to use with this struct*/
|
|
void lodepng_state_init(LodePNGState* state);
|
|
void lodepng_state_cleanup(LodePNGState* state);
|
|
void lodepng_state_copy(LodePNGState* dest, const LodePNGState* source);
|
|
#endif /* defined(LODEPNG_COMPILE_DECODER) || defined(LODEPNG_COMPILE_ENCODER) */
|
|
|
|
#ifdef LODEPNG_COMPILE_DECODER
|
|
/*
|
|
Same as lodepng_decode_memory, but uses a LodePNGState to allow custom settings and
|
|
getting much more information about the PNG image and color mode.
|
|
*/
|
|
unsigned lodepng_decode(unsigned char** out, unsigned* w, unsigned* h,
|
|
LodePNGState* state,
|
|
const unsigned char* in, size_t insize);
|
|
|
|
/*
|
|
Read the PNG header, but not the actual data. This returns only the information
|
|
that is in the header chunk of the PNG, such as width, height and color type. The
|
|
information is placed in the info_png field of the LodePNGState.
|
|
*/
|
|
unsigned lodepng_inspect(unsigned* w, unsigned* h,
|
|
LodePNGState* state,
|
|
const unsigned char* in, size_t insize);
|
|
#endif /*LODEPNG_COMPILE_DECODER*/
|
|
|
|
|
|
#ifdef LODEPNG_COMPILE_ENCODER
|
|
/*This function allocates the out buffer with standard malloc and stores the size in *outsize.*/
|
|
unsigned lodepng_encode(unsigned char** out, size_t* outsize,
|
|
const unsigned char* image, unsigned w, unsigned h,
|
|
LodePNGState* state);
|
|
#endif /*LODEPNG_COMPILE_ENCODER*/
|
|
|
|
/*
|
|
The lodepng_chunk functions are normally not needed, except to traverse the
|
|
unknown chunks stored in the LodePNGInfo struct, or add new ones to it.
|
|
It also allows traversing the chunks of an encoded PNG file yourself.
|
|
|
|
PNG standard chunk naming conventions:
|
|
First byte: uppercase = critical, lowercase = ancillary
|
|
Second byte: uppercase = public, lowercase = private
|
|
Third byte: must be uppercase
|
|
Fourth byte: uppercase = unsafe to copy, lowercase = safe to copy
|
|
*/
|
|
|
|
/*
|
|
Gets the length of the data of the chunk. Total chunk length has 12 bytes more.
|
|
There must be at least 4 bytes to read from. If the result value is too large,
|
|
it may be corrupt data.
|
|
*/
|
|
unsigned lodepng_chunk_length(const unsigned char* chunk);
|
|
|
|
/*puts the 4-byte type in null terminated string*/
|
|
void lodepng_chunk_type(char type[5], const unsigned char* chunk);
|
|
|
|
/*check if the type is the given type*/
|
|
unsigned char lodepng_chunk_type_equals(const unsigned char* chunk, const char* type);
|
|
|
|
/*0: it's one of the critical chunk types, 1: it's an ancillary chunk (see PNG standard)*/
|
|
unsigned char lodepng_chunk_ancillary(const unsigned char* chunk);
|
|
|
|
/*0: public, 1: private (see PNG standard)*/
|
|
unsigned char lodepng_chunk_private(const unsigned char* chunk);
|
|
|
|
/*0: the chunk is unsafe to copy, 1: the chunk is safe to copy (see PNG standard)*/
|
|
unsigned char lodepng_chunk_safetocopy(const unsigned char* chunk);
|
|
|
|
/*get pointer to the data of the chunk, where the input points to the header of the chunk*/
|
|
unsigned char* lodepng_chunk_data(unsigned char* chunk);
|
|
const unsigned char* lodepng_chunk_data_const(const unsigned char* chunk);
|
|
|
|
/*returns 0 if the crc is correct, 1 if it's incorrect (0 for OK as usual!)*/
|
|
unsigned lodepng_chunk_check_crc(const unsigned char* chunk);
|
|
|
|
/*generates the correct CRC from the data and puts it in the last 4 bytes of the chunk*/
|
|
void lodepng_chunk_generate_crc(unsigned char* chunk);
|
|
|
|
/*iterate to next chunks. don't use on IEND chunk, as there is no next chunk then*/
|
|
unsigned char* lodepng_chunk_next(unsigned char* chunk);
|
|
const unsigned char* lodepng_chunk_next_const(const unsigned char* chunk);
|
|
|
|
/*
|
|
Appends chunk to the data in out. The given chunk should already have its chunk header.
|
|
The out variable and outlength are updated to reflect the new reallocated buffer.
|
|
Returns error code (0 if it went ok)
|
|
*/
|
|
unsigned lodepng_chunk_append(unsigned char** out, size_t* outlength, const unsigned char* chunk);
|
|
|
|
/*
|
|
Appends new chunk to out. The chunk to append is given by giving its length, type
|
|
and data separately. The type is a 4-letter string.
|
|
The out variable and outlength are updated to reflect the new reallocated buffer.
|
|
Returne error code (0 if it went ok)
|
|
*/
|
|
unsigned lodepng_chunk_create(unsigned char** out, size_t* outlength, unsigned length,
|
|
const char* type, const unsigned char* data);
|
|
|
|
|
|
/*Calculate CRC32 of buffer*/
|
|
unsigned lodepng_crc32(const unsigned char* buf, size_t len);
|
|
#endif /*LODEPNG_COMPILE_PNG*/
|
|
|
|
|
|
#ifdef LODEPNG_COMPILE_ZLIB
|
|
/*
|
|
This zlib part can be used independently to zlib compress and decompress a
|
|
buffer. It cannot be used to create gzip files however, and it only supports the
|
|
part of zlib that is required for PNG, it does not support dictionaries.
|
|
*/
|
|
|
|
#ifdef LODEPNG_COMPILE_DECODER
|
|
/*Inflate a buffer. Inflate is the decompression step of deflate. Out buffer must be freed after use.*/
|
|
unsigned lodepng_inflate(unsigned char** out, size_t* outsize,
|
|
const unsigned char* in, size_t insize,
|
|
const LodePNGDecompressSettings* settings);
|
|
|
|
/*
|
|
Decompresses Zlib data. Reallocates the out buffer and appends the data. The
|
|
data must be according to the zlib specification.
|
|
Either, *out must be NULL and *outsize must be 0, or, *out must be a valid
|
|
buffer and *outsize its size in bytes. out must be freed by user after usage.
|
|
*/
|
|
unsigned lodepng_zlib_decompress(unsigned char** out, size_t* outsize,
|
|
const unsigned char* in, size_t insize,
|
|
const LodePNGDecompressSettings* settings);
|
|
#endif /*LODEPNG_COMPILE_DECODER*/
|
|
|
|
#ifdef LODEPNG_COMPILE_ENCODER
|
|
/*
|
|
Compresses data with Zlib. Reallocates the out buffer and appends the data.
|
|
Zlib adds a small header and trailer around the deflate data.
|
|
The data is output in the format of the zlib specification.
|
|
Either, *out must be NULL and *outsize must be 0, or, *out must be a valid
|
|
buffer and *outsize its size in bytes. out must be freed by user after usage.
|
|
*/
|
|
unsigned lodepng_zlib_compress(unsigned char** out, size_t* outsize,
|
|
const unsigned char* in, size_t insize,
|
|
const LodePNGCompressSettings* settings);
|
|
|
|
/*
|
|
Find length-limited Huffman code for given frequencies. This function is in the
|
|
public interface only for tests, it's used internally by lodepng_deflate.
|
|
*/
|
|
unsigned lodepng_huffman_code_lengths(unsigned* lengths, const unsigned* frequencies,
|
|
size_t numcodes, unsigned maxbitlen);
|
|
|
|
/*Compress a buffer with deflate. See RFC 1951. Out buffer must be freed after use.*/
|
|
unsigned lodepng_deflate(unsigned char** out, size_t* outsize,
|
|
const unsigned char* in, size_t insize,
|
|
const LodePNGCompressSettings* settings);
|
|
|
|
#endif /*LODEPNG_COMPILE_ENCODER*/
|
|
#endif /*LODEPNG_COMPILE_ZLIB*/
|
|
|
|
#ifdef LODEPNG_COMPILE_DISK
|
|
/*
|
|
Load a file from disk into buffer. The function allocates the out buffer, and
|
|
after usage you should free it.
|
|
out: output parameter, contains pointer to loaded buffer.
|
|
outsize: output parameter, size of the allocated out buffer
|
|
filename: the path to the file to load
|
|
return value: error code (0 means ok)
|
|
*/
|
|
unsigned lodepng_load_file(unsigned char** out, size_t* outsize, const char* filename);
|
|
|
|
/*
|
|
Save a file from buffer to disk. Warning, if it exists, this function overwrites
|
|
the file without warning!
|
|
buffer: the buffer to write
|
|
buffersize: size of the buffer to write
|
|
filename: the path to the file to save to
|
|
return value: error code (0 means ok)
|
|
*/
|
|
unsigned lodepng_save_file(const unsigned char* buffer, size_t buffersize, const char* filename);
|
|
#endif /*LODEPNG_COMPILE_DISK*/
|
|
|
|
#ifdef LODEPNG_COMPILE_CPP
|
|
/* The LodePNG C++ wrapper uses std::vectors instead of manually allocated memory buffers. */
|
|
namespace lodepng
|
|
{
|
|
#ifdef LODEPNG_COMPILE_PNG
|
|
class State : public LodePNGState
|
|
{
|
|
public:
|
|
State();
|
|
State(const State& other);
|
|
virtual ~State();
|
|
State& operator=(const State& other);
|
|
};
|
|
|
|
#ifdef LODEPNG_COMPILE_DECODER
|
|
/* Same as other lodepng::decode, but using a State for more settings and information. */
|
|
unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
|
|
State& state,
|
|
const unsigned char* in, size_t insize);
|
|
unsigned decode(std::vector<unsigned char>& out, unsigned& w, unsigned& h,
|
|
State& state,
|
|
const std::vector<unsigned char>& in);
|
|
#endif /*LODEPNG_COMPILE_DECODER*/
|
|
|
|
#ifdef LODEPNG_COMPILE_ENCODER
|
|
/* Same as other lodepng::encode, but using a State for more settings and information. */
|
|
unsigned encode(std::vector<unsigned char>& out,
|
|
const unsigned char* in, unsigned w, unsigned h,
|
|
State& state);
|
|
unsigned encode(std::vector<unsigned char>& out,
|
|
const std::vector<unsigned char>& in, unsigned w, unsigned h,
|
|
State& state);
|
|
#endif /*LODEPNG_COMPILE_ENCODER*/
|
|
|
|
#ifdef LODEPNG_COMPILE_DISK
|
|
/*
|
|
Load a file from disk into an std::vector.
|
|
return value: error code (0 means ok)
|
|
*/
|
|
unsigned load_file(std::vector<unsigned char>& buffer, const std::string& filename);
|
|
|
|
/*
|
|
Save the binary data in an std::vector to a file on disk. The file is overwritten
|
|
without warning.
|
|
*/
|
|
unsigned save_file(const std::vector<unsigned char>& buffer, const std::string& filename);
|
|
#endif /* LODEPNG_COMPILE_DISK */
|
|
#endif /* LODEPNG_COMPILE_PNG */
|
|
|
|
#ifdef LODEPNG_COMPILE_ZLIB
|
|
#ifdef LODEPNG_COMPILE_DECODER
|
|
/* Zlib-decompress an unsigned char buffer */
|
|
unsigned decompress(std::vector<unsigned char>& out, const unsigned char* in, size_t insize,
|
|
const LodePNGDecompressSettings& settings = lodepng_default_decompress_settings);
|
|
|
|
/* Zlib-decompress an std::vector */
|
|
unsigned decompress(std::vector<unsigned char>& out, const std::vector<unsigned char>& in,
|
|
const LodePNGDecompressSettings& settings = lodepng_default_decompress_settings);
|
|
#endif /* LODEPNG_COMPILE_DECODER */
|
|
|
|
#ifdef LODEPNG_COMPILE_ENCODER
|
|
/* Zlib-compress an unsigned char buffer */
|
|
unsigned compress(std::vector<unsigned char>& out, const unsigned char* in, size_t insize,
|
|
const LodePNGCompressSettings& settings = lodepng_default_compress_settings);
|
|
|
|
/* Zlib-compress an std::vector */
|
|
unsigned compress(std::vector<unsigned char>& out, const std::vector<unsigned char>& in,
|
|
const LodePNGCompressSettings& settings = lodepng_default_compress_settings);
|
|
#endif /* LODEPNG_COMPILE_ENCODER */
|
|
#endif /* LODEPNG_COMPILE_ZLIB */
|
|
} /* namespace lodepng */
|
|
#endif /*LODEPNG_COMPILE_CPP*/
|
|
|
|
/*
|
|
TODO:
|
|
[.] test if there are no memory leaks or security exploits - done a lot but needs to be checked often
|
|
[.] check compatibility with various compilers - done but needs to be redone for every newer version
|
|
[X] converting color to 16-bit per channel types
|
|
[ ] read all public PNG chunk types (but never let the color profile and gamma ones touch RGB values)
|
|
[ ] make sure encoder generates no chunks with size > (2^31)-1
|
|
[ ] partial decoding (stream processing)
|
|
[X] let the "isFullyOpaque" function check color keys and transparent palettes too
|
|
[X] better name for the variables "codes", "codesD", "codelengthcodes", "clcl" and "lldl"
|
|
[ ] don't stop decoding on errors like 69, 57, 58 (make warnings)
|
|
[ ] let the C++ wrapper catch exceptions coming from the standard library and return LodePNG error codes
|
|
[ ] allow user to provide custom color conversion functions, e.g. for premultiplied alpha, padding bits or not, ...
|
|
[ ] allow user to give data (void*) to custom allocator
|
|
*/
|
|
|
|
#endif /*LODEPNG_H inclusion guard*/
|
|
|
|
/*
|
|
LodePNG Documentation
|
|
---------------------
|
|
|
|
0. table of contents
|
|
--------------------
|
|
|
|
1. about
|
|
1.1. supported features
|
|
1.2. features not supported
|
|
2. C and C++ version
|
|
3. security
|
|
4. decoding
|
|
5. encoding
|
|
6. color conversions
|
|
6.1. PNG color types
|
|
6.2. color conversions
|
|
6.3. padding bits
|
|
6.4. A note about 16-bits per channel and endianness
|
|
7. error values
|
|
8. chunks and PNG editing
|
|
9. compiler support
|
|
10. examples
|
|
10.1. decoder C++ example
|
|
10.2. decoder C example
|
|
11. state settings reference
|
|
12. changes
|
|
13. contact information
|
|
|
|
|
|
1. about
|
|
--------
|
|
|
|
PNG is a file format to store raster images losslessly with good compression,
|
|
supporting different color types and alpha channel.
|
|
|
|
LodePNG is a PNG codec according to the Portable Network Graphics (PNG)
|
|
Specification (Second Edition) - W3C Recommendation 10 November 2003.
|
|
|
|
The specifications used are:
|
|
|
|
*) Portable Network Graphics (PNG) Specification (Second Edition):
|
|
http://www.w3.org/TR/2003/REC-PNG-20031110
|
|
*) RFC 1950 ZLIB Compressed Data Format version 3.3:
|
|
http://www.gzip.org/zlib/rfc-zlib.html
|
|
*) RFC 1951 DEFLATE Compressed Data Format Specification ver 1.3:
|
|
http://www.gzip.org/zlib/rfc-deflate.html
|
|
|
|
The most recent version of LodePNG can currently be found at
|
|
http://lodev.org/lodepng/
|
|
|
|
LodePNG works both in C (ISO C90) and C++, with a C++ wrapper that adds
|
|
extra functionality.
|
|
|
|
LodePNG exists out of two files:
|
|
-lodepng.h: the header file for both C and C++
|
|
-lodepng.c(pp): give it the name lodepng.c or lodepng.cpp (or .cc) depending on your usage
|
|
|
|
If you want to start using LodePNG right away without reading this doc, get the
|
|
examples from the LodePNG website to see how to use it in code, or check the
|
|
smaller examples in chapter 13 here.
|
|
|
|
LodePNG is simple but only supports the basic requirements. To achieve
|
|
simplicity, the following design choices were made: There are no dependencies
|
|
on any external library. There are functions to decode and encode a PNG with
|
|
a single function call, and extended versions of these functions taking a
|
|
LodePNGState struct allowing to specify or get more information. By default
|
|
the colors of the raw image are always RGB or RGBA, no matter what color type
|
|
the PNG file uses. To read and write files, there are simple functions to
|
|
convert the files to/from buffers in memory.
|
|
|
|
This all makes LodePNG suitable for loading textures in games, demos and small
|
|
programs, ... It's less suitable for full fledged image editors, loading PNGs
|
|
over network (it requires all the image data to be available before decoding can
|
|
begin), life-critical systems, ...
|
|
|
|
1.1. supported features
|
|
-----------------------
|
|
|
|
The following features are supported by the decoder:
|
|
|
|
*) decoding of PNGs with any color type, bit depth and interlace mode, to a 24- or 32-bit color raw image,
|
|
or the same color type as the PNG
|
|
*) encoding of PNGs, from any raw image to 24- or 32-bit color, or the same color type as the raw image
|
|
*) Adam7 interlace and deinterlace for any color type
|
|
*) loading the image from harddisk or decoding it from a buffer from other sources than harddisk
|
|
*) support for alpha channels, including RGBA color model, translucent palettes and color keying
|
|
*) zlib decompression (inflate)
|
|
*) zlib compression (deflate)
|
|
*) CRC32 and ADLER32 checksums
|
|
*) handling of unknown chunks, allowing making a PNG editor that stores custom and unknown chunks.
|
|
*) the following chunks are supported (generated/interpreted) by both encoder and decoder:
|
|
IHDR: header information
|
|
PLTE: color palette
|
|
IDAT: pixel data
|
|
IEND: the final chunk
|
|
tRNS: transparency for palettized images
|
|
tEXt: textual information
|
|
zTXt: compressed textual information
|
|
iTXt: international textual information
|
|
bKGD: suggested background color
|
|
pHYs: physical dimensions
|
|
tIME: modification time
|
|
|
|
1.2. features not supported
|
|
---------------------------
|
|
|
|
The following features are _not_ supported:
|
|
|
|
*) some features needed to make a conformant PNG-Editor might be still missing.
|
|
*) partial loading/stream processing. All data must be available and is processed in one call.
|
|
*) The following public chunks are not supported but treated as unknown chunks by LodePNG
|
|
cHRM, gAMA, iCCP, sRGB, sBIT, hIST, sPLT
|
|
Some of these are not supported on purpose: LodePNG wants to provide the RGB values
|
|
stored in the pixels, not values modified by system dependent gamma or color models.
|
|
|
|
|
|
2. C and C++ version
|
|
--------------------
|
|
|
|
The C version uses buffers allocated with alloc that you need to free()
|
|
yourself. You need to use init and cleanup functions for each struct whenever
|
|
using a struct from the C version to avoid exploits and memory leaks.
|
|
|
|
The C++ version has extra functions with std::vectors in the interface and the
|
|
lodepng::State class which is a LodePNGState with constructor and destructor.
|
|
|
|
These files work without modification for both C and C++ compilers because all
|
|
the additional C++ code is in "#ifdef __cplusplus" blocks that make C-compilers
|
|
ignore it, and the C code is made to compile both with strict ISO C90 and C++.
|
|
|
|
To use the C++ version, you need to rename the source file to lodepng.cpp
|
|
(instead of lodepng.c), and compile it with a C++ compiler.
|
|
|
|
To use the C version, you need to rename the source file to lodepng.c (instead
|
|
of lodepng.cpp), and compile it with a C compiler.
|
|
|
|
|
|
3. Security
|
|
-----------
|
|
|
|
Even if carefully designed, it's always possible that LodePNG contains possible
|
|
exploits. If you discover one, please let me know, and it will be fixed.
|
|
|
|
When using LodePNG, care has to be taken with the C version of LodePNG, as well
|
|
as the C-style structs when working with C++. The following conventions are used
|
|
for all C-style structs:
|
|
|
|
-if a struct has a corresponding init function, always call the init function when making a new one
|
|
-if a struct has a corresponding cleanup function, call it before the struct disappears to avoid memory leaks
|
|
-if a struct has a corresponding copy function, use the copy function instead of "=".
|
|
The destination must also be inited already.
|
|
|
|
|
|
4. Decoding
|
|
-----------
|
|
|
|
Decoding converts a PNG compressed image to a raw pixel buffer.
|
|
|
|
Most documentation on using the decoder is at its declarations in the header
|
|
above. For C, simple decoding can be done with functions such as
|
|
lodepng_decode32, and more advanced decoding can be done with the struct
|
|
LodePNGState and lodepng_decode. For C++, all decoding can be done with the
|
|
various lodepng::decode functions, and lodepng::State can be used for advanced
|
|
features.
|
|
|
|
When using the LodePNGState, it uses the following fields for decoding:
|
|
*) LodePNGInfo info_png: it stores extra information about the PNG (the input) in here
|
|
*) LodePNGColorMode info_raw: here you can say what color mode of the raw image (the output) you want to get
|
|
*) LodePNGDecoderSettings decoder: you can specify a few extra settings for the decoder to use
|
|
|
|
LodePNGInfo info_png
|
|
--------------------
|
|
|
|
After decoding, this contains extra information of the PNG image, except the actual
|
|
pixels, width and height because these are already gotten directly from the decoder
|
|
functions.
|
|
|
|
It contains for example the original color type of the PNG image, text comments,
|
|
suggested background color, etc... More details about the LodePNGInfo struct are
|
|
at its declaration documentation.
|
|
|
|
LodePNGColorMode info_raw
|
|
-------------------------
|
|
|
|
When decoding, here you can specify which color type you want
|
|
the resulting raw image to be. If this is different from the colortype of the
|
|
PNG, then the decoder will automatically convert the result. This conversion
|
|
always works, except if you want it to convert a color PNG to greyscale or to
|
|
a palette with missing colors.
|
|
|
|
By default, 32-bit color is used for the result.
|
|
|
|
LodePNGDecoderSettings decoder
|
|
------------------------------
|
|
|
|
The settings can be used to ignore the errors created by invalid CRC and Adler32
|
|
chunks, and to disable the decoding of tEXt chunks.
|
|
|
|
There's also a setting color_convert, true by default. If false, no conversion
|
|
is done, the resulting data will be as it was in the PNG (after decompression)
|
|
and you'll have to puzzle the colors of the pixels together yourself using the
|
|
color type information in the LodePNGInfo.
|
|
|
|
|
|
5. Encoding
|
|
-----------
|
|
|
|
Encoding converts a raw pixel buffer to a PNG compressed image.
|
|
|
|
Most documentation on using the encoder is at its declarations in the header
|
|
above. For C, simple encoding can be done with functions such as
|
|
lodepng_encode32, and more advanced decoding can be done with the struct
|
|
LodePNGState and lodepng_encode. For C++, all encoding can be done with the
|
|
various lodepng::encode functions, and lodepng::State can be used for advanced
|
|
features.
|
|
|
|
Like the decoder, the encoder can also give errors. However it gives less errors
|
|
since the encoder input is trusted, the decoder input (a PNG image that could
|
|
be forged by anyone) is not trusted.
|
|
|
|
When using the LodePNGState, it uses the following fields for encoding:
|
|
*) LodePNGInfo info_png: here you specify how you want the PNG (the output) to be.
|
|
*) LodePNGColorMode info_raw: here you say what color type of the raw image (the input) has
|
|
*) LodePNGEncoderSettings encoder: you can specify a few settings for the encoder to use
|
|
|
|
LodePNGInfo info_png
|
|
--------------------
|
|
|
|
When encoding, you use this the opposite way as when decoding: for encoding,
|
|
you fill in the values you want the PNG to have before encoding. By default it's
|
|
not needed to specify a color type for the PNG since it's automatically chosen,
|
|
but it's possible to choose it yourself given the right settings.
|
|
|
|
The encoder will not always exactly match the LodePNGInfo struct you give,
|
|
it tries as close as possible. Some things are ignored by the encoder. The
|
|
encoder uses, for example, the following settings from it when applicable:
|
|
colortype and bitdepth, text chunks, time chunk, the color key, the palette, the
|
|
background color, the interlace method, unknown chunks, ...
|
|
|
|
When encoding to a PNG with colortype 3, the encoder will generate a PLTE chunk.
|
|
If the palette contains any colors for which the alpha channel is not 255 (so
|
|
there are translucent colors in the palette), it'll add a tRNS chunk.
|
|
|
|
LodePNGColorMode info_raw
|
|
-------------------------
|
|
|
|
You specify the color type of the raw image that you give to the input here,
|
|
including a possible transparent color key and palette you happen to be using in
|
|
your raw image data.
|
|
|
|
By default, 32-bit color is assumed, meaning your input has to be in RGBA
|
|
format with 4 bytes (unsigned chars) per pixel.
|
|
|
|
LodePNGEncoderSettings encoder
|
|
------------------------------
|
|
|
|
The following settings are supported (some are in sub-structs):
|
|
*) auto_convert: when this option is enabled, the encoder will
|
|
automatically choose the smallest possible color mode (including color key) that
|
|
can encode the colors of all pixels without information loss.
|
|
*) btype: the block type for LZ77. 0 = uncompressed, 1 = fixed huffman tree,
|
|
2 = dynamic huffman tree (best compression). Should be 2 for proper
|
|
compression.
|
|
*) use_lz77: whether or not to use LZ77 for compressed block types. Should be
|
|
true for proper compression.
|
|
*) windowsize: the window size used by the LZ77 encoder (1 - 32768). Has value
|
|
2048 by default, but can be set to 32768 for better, but slow, compression.
|
|
*) force_palette: if colortype is 2 or 6, you can make the encoder write a PLTE
|
|
chunk if force_palette is true. This can used as suggested palette to convert
|
|
to by viewers that don't support more than 256 colors (if those still exist)
|
|
*) add_id: add text chunk "Encoder: LodePNG <version>" to the image.
|
|
*) text_compression: default 1. If 1, it'll store texts as zTXt instead of tEXt chunks.
|
|
zTXt chunks use zlib compression on the text. This gives a smaller result on
|
|
large texts but a larger result on small texts (such as a single program name).
|
|
It's all tEXt or all zTXt though, there's no separate setting per text yet.
|
|
|
|
|
|
6. color conversions
|
|
--------------------
|
|
|
|
An important thing to note about LodePNG, is that the color type of the PNG, and
|
|
the color type of the raw image, are completely independent. By default, when
|
|
you decode a PNG, you get the result as a raw image in the color type you want,
|
|
no matter whether the PNG was encoded with a palette, greyscale or RGBA color.
|
|
And if you encode an image, by default LodePNG will automatically choose the PNG
|
|
color type that gives good compression based on the values of colors and amount
|
|
of colors in the image. It can be configured to let you control it instead as
|
|
well, though.
|
|
|
|
To be able to do this, LodePNG does conversions from one color mode to another.
|
|
It can convert from almost any color type to any other color type, except the
|
|
following conversions: RGB to greyscale is not supported, and converting to a
|
|
palette when the palette doesn't have a required color is not supported. This is
|
|
not supported on purpose: this is information loss which requires a color
|
|
reduction algorithm that is beyong the scope of a PNG encoder (yes, RGB to grey
|
|
is easy, but there are multiple ways if you want to give some channels more
|
|
weight).
|
|
|
|
By default, when decoding, you get the raw image in 32-bit RGBA or 24-bit RGB
|
|
color, no matter what color type the PNG has. And by default when encoding,
|
|
LodePNG automatically picks the best color model for the output PNG, and expects
|
|
the input image to be 32-bit RGBA or 24-bit RGB. So, unless you want to control
|
|
the color format of the images yourself, you can skip this chapter.
|
|
|
|
6.1. PNG color types
|
|
--------------------
|
|
|
|
A PNG image can have many color types, ranging from 1-bit color to 64-bit color,
|
|
as well as palettized color modes. After the zlib decompression and unfiltering
|
|
in the PNG image is done, the raw pixel data will have that color type and thus
|
|
a certain amount of bits per pixel. If you want the output raw image after
|
|
decoding to have another color type, a conversion is done by LodePNG.
|
|
|
|
The PNG specification gives the following color types:
|
|
|
|
0: greyscale, bit depths 1, 2, 4, 8, 16
|
|
2: RGB, bit depths 8 and 16
|
|
3: palette, bit depths 1, 2, 4 and 8
|
|
4: greyscale with alpha, bit depths 8 and 16
|
|
6: RGBA, bit depths 8 and 16
|
|
|
|
Bit depth is the amount of bits per pixel per color channel. So the total amount
|
|
of bits per pixel is: amount of channels * bitdepth.
|
|
|
|
6.2. color conversions
|
|
----------------------
|
|
|
|
As explained in the sections about the encoder and decoder, you can specify
|
|
color types and bit depths in info_png and info_raw to change the default
|
|
behaviour.
|
|
|
|
If, when decoding, you want the raw image to be something else than the default,
|
|
you need to set the color type and bit depth you want in the LodePNGColorMode,
|
|
or the parameters colortype and bitdepth of the simple decoding function.
|
|
|
|
If, when encoding, you use another color type than the default in the raw input
|
|
image, you need to specify its color type and bit depth in the LodePNGColorMode
|
|
of the raw image, or use the parameters colortype and bitdepth of the simple
|
|
encoding function.
|
|
|
|
If, when encoding, you don't want LodePNG to choose the output PNG color type
|
|
but control it yourself, you need to set auto_convert in the encoder settings
|
|
to false, and specify the color type you want in the LodePNGInfo of the
|
|
encoder (including palette: it can generate a palette if auto_convert is true,
|
|
otherwise not).
|
|
|
|
If the input and output color type differ (whether user chosen or auto chosen),
|
|
LodePNG will do a color conversion, which follows the rules below, and may
|
|
sometimes result in an error.
|
|
|
|
To avoid some confusion:
|
|
-the decoder converts from PNG to raw image
|
|
-the encoder converts from raw image to PNG
|
|
-the colortype and bitdepth in LodePNGColorMode info_raw, are those of the raw image
|
|
-the colortype and bitdepth in the color field of LodePNGInfo info_png, are those of the PNG
|
|
-when encoding, the color type in LodePNGInfo is ignored if auto_convert
|
|
is enabled, it is automatically generated instead
|
|
-when decoding, the color type in LodePNGInfo is set by the decoder to that of the original
|
|
PNG image, but it can be ignored since the raw image has the color type you requested instead
|
|
-if the color type of the LodePNGColorMode and PNG image aren't the same, a conversion
|
|
between the color types is done if the color types are supported. If it is not
|
|
supported, an error is returned. If the types are the same, no conversion is done.
|
|
-even though some conversions aren't supported, LodePNG supports loading PNGs from any
|
|
colortype and saving PNGs to any colortype, sometimes it just requires preparing
|
|
the raw image correctly before encoding.
|
|
-both encoder and decoder use the same color converter.
|
|
|
|
Non supported color conversions:
|
|
-color to greyscale: no error is thrown, but the result will look ugly because
|
|
only the red channel is taken
|
|
-anything to palette when that palette does not have that color in it: in this
|
|
case an error is thrown
|
|
|
|
Supported color conversions:
|
|
-anything to 8-bit RGB, 8-bit RGBA, 16-bit RGB, 16-bit RGBA
|
|
-any grey or grey+alpha, to grey or grey+alpha
|
|
-anything to a palette, as long as the palette has the requested colors in it
|
|
-removing alpha channel
|
|
-higher to smaller bitdepth, and vice versa
|
|
|
|
If you want no color conversion to be done (e.g. for speed or control):
|
|
-In the encoder, you can make it save a PNG with any color type by giving the
|
|
raw color mode and LodePNGInfo the same color mode, and setting auto_convert to
|
|
false.
|
|
-In the decoder, you can make it store the pixel data in the same color type
|
|
as the PNG has, by setting the color_convert setting to false. Settings in
|
|
info_raw are then ignored.
|
|
|
|
The function lodepng_convert does the color conversion. It is available in the
|
|
interface but normally isn't needed since the encoder and decoder already call
|
|
it.
|
|
|
|
6.3. padding bits
|
|
-----------------
|
|
|
|
In the PNG file format, if a less than 8-bit per pixel color type is used and the scanlines
|
|
have a bit amount that isn't a multiple of 8, then padding bits are used so that each
|
|
scanline starts at a fresh byte. But that is NOT true for the LodePNG raw input and output.
|
|
The raw input image you give to the encoder, and the raw output image you get from the decoder
|
|
will NOT have these padding bits, e.g. in the case of a 1-bit image with a width
|
|
of 7 pixels, the first pixel of the second scanline will the the 8th bit of the first byte,
|
|
not the first bit of a new byte.
|
|
|
|
6.4. A note about 16-bits per channel and endianness
|
|
----------------------------------------------------
|
|
|
|
LodePNG uses unsigned char arrays for 16-bit per channel colors too, just like
|
|
for any other color format. The 16-bit values are stored in big endian (most
|
|
significant byte first) in these arrays. This is the opposite order of the
|
|
little endian used by x86 CPU's.
|
|
|
|
LodePNG always uses big endian because the PNG file format does so internally.
|
|
Conversions to other formats than PNG uses internally are not supported by
|
|
LodePNG on purpose, there are myriads of formats, including endianness of 16-bit
|
|
colors, the order in which you store R, G, B and A, and so on. Supporting and
|
|
converting to/from all that is outside the scope of LodePNG.
|
|
|
|
This may mean that, depending on your use case, you may want to convert the big
|
|
endian output of LodePNG to little endian with a for loop. This is certainly not
|
|
always needed, many applications and libraries support big endian 16-bit colors
|
|
anyway, but it means you cannot simply cast the unsigned char* buffer to an
|
|
unsigned short* buffer on x86 CPUs.
|
|
|
|
|
|
7. error values
|
|
---------------
|
|
|
|
All functions in LodePNG that return an error code, return 0 if everything went
|
|
OK, or a non-zero code if there was an error.
|
|
|
|
The meaning of the LodePNG error values can be retrieved with the function
|
|
lodepng_error_text: given the numerical error code, it returns a description
|
|
of the error in English as a string.
|
|
|
|
Check the implementation of lodepng_error_text to see the meaning of each code.
|
|
|
|
|
|
8. chunks and PNG editing
|
|
-------------------------
|
|
|
|
If you want to add extra chunks to a PNG you encode, or use LodePNG for a PNG
|
|
editor that should follow the rules about handling of unknown chunks, or if your
|
|
program is able to read other types of chunks than the ones handled by LodePNG,
|
|
then that's possible with the chunk functions of LodePNG.
|
|
|
|
A PNG chunk has the following layout:
|
|
|
|
4 bytes length
|
|
4 bytes type name
|
|
length bytes data
|
|
4 bytes CRC
|
|
|
|
8.1. iterating through chunks
|
|
-----------------------------
|
|
|
|
If you have a buffer containing the PNG image data, then the first chunk (the
|
|
IHDR chunk) starts at byte number 8 of that buffer. The first 8 bytes are the
|
|
signature of the PNG and are not part of a chunk. But if you start at byte 8
|
|
then you have a chunk, and can check the following things of it.
|
|
|
|
NOTE: none of these functions check for memory buffer boundaries. To avoid
|
|
exploits, always make sure the buffer contains all the data of the chunks.
|
|
When using lodepng_chunk_next, make sure the returned value is within the
|
|
allocated memory.
|
|
|
|
unsigned lodepng_chunk_length(const unsigned char* chunk):
|
|
|
|
Get the length of the chunk's data. The total chunk length is this length + 12.
|
|
|
|
void lodepng_chunk_type(char type[5], const unsigned char* chunk):
|
|
unsigned char lodepng_chunk_type_equals(const unsigned char* chunk, const char* type):
|
|
|
|
Get the type of the chunk or compare if it's a certain type
|
|
|
|
unsigned char lodepng_chunk_critical(const unsigned char* chunk):
|
|
unsigned char lodepng_chunk_private(const unsigned char* chunk):
|
|
unsigned char lodepng_chunk_safetocopy(const unsigned char* chunk):
|
|
|
|
Check if the chunk is critical in the PNG standard (only IHDR, PLTE, IDAT and IEND are).
|
|
Check if the chunk is private (public chunks are part of the standard, private ones not).
|
|
Check if the chunk is safe to copy. If it's not, then, when modifying data in a critical
|
|
chunk, unsafe to copy chunks of the old image may NOT be saved in the new one if your
|
|
program doesn't handle that type of unknown chunk.
|
|
|
|
unsigned char* lodepng_chunk_data(unsigned char* chunk):
|
|
const unsigned char* lodepng_chunk_data_const(const unsigned char* chunk):
|
|
|
|
Get a pointer to the start of the data of the chunk.
|
|
|
|
unsigned lodepng_chunk_check_crc(const unsigned char* chunk):
|
|
void lodepng_chunk_generate_crc(unsigned char* chunk):
|
|
|
|
Check if the crc is correct or generate a correct one.
|
|
|
|
unsigned char* lodepng_chunk_next(unsigned char* chunk):
|
|
const unsigned char* lodepng_chunk_next_const(const unsigned char* chunk):
|
|
|
|
Iterate to the next chunk. This works if you have a buffer with consecutive chunks. Note that these
|
|
functions do no boundary checking of the allocated data whatsoever, so make sure there is enough
|
|
data available in the buffer to be able to go to the next chunk.
|
|
|
|
unsigned lodepng_chunk_append(unsigned char** out, size_t* outlength, const unsigned char* chunk):
|
|
unsigned lodepng_chunk_create(unsigned char** out, size_t* outlength, unsigned length,
|
|
const char* type, const unsigned char* data):
|
|
|
|
These functions are used to create new chunks that are appended to the data in *out that has
|
|
length *outlength. The append function appends an existing chunk to the new data. The create
|
|
function creates a new chunk with the given parameters and appends it. Type is the 4-letter
|
|
name of the chunk.
|
|
|
|
8.2. chunks in info_png
|
|
-----------------------
|
|
|
|
The LodePNGInfo struct contains fields with the unknown chunk in it. It has 3
|
|
buffers (each with size) to contain 3 types of unknown chunks:
|
|
the ones that come before the PLTE chunk, the ones that come between the PLTE
|
|
and the IDAT chunks, and the ones that come after the IDAT chunks.
|
|
It's necessary to make the distionction between these 3 cases because the PNG
|
|
standard forces to keep the ordering of unknown chunks compared to the critical
|
|
chunks, but does not force any other ordering rules.
|
|
|
|
info_png.unknown_chunks_data[0] is the chunks before PLTE
|
|
info_png.unknown_chunks_data[1] is the chunks after PLTE, before IDAT
|
|
info_png.unknown_chunks_data[2] is the chunks after IDAT
|
|
|
|
The chunks in these 3 buffers can be iterated through and read by using the same
|
|
way described in the previous subchapter.
|
|
|
|
When using the decoder to decode a PNG, you can make it store all unknown chunks
|
|
if you set the option settings.remember_unknown_chunks to 1. By default, this
|
|
option is off (0).
|
|
|
|
The encoder will always encode unknown chunks that are stored in the info_png.
|
|
If you need it to add a particular chunk that isn't known by LodePNG, you can
|
|
use lodepng_chunk_append or lodepng_chunk_create to the chunk data in
|
|
info_png.unknown_chunks_data[x].
|
|
|
|
Chunks that are known by LodePNG should not be added in that way. E.g. to make
|
|
LodePNG add a bKGD chunk, set background_defined to true and add the correct
|
|
parameters there instead.
|
|
|
|
|
|
9. compiler support
|
|
-------------------
|
|
|
|
No libraries other than the current standard C library are needed to compile
|
|
LodePNG. For the C++ version, only the standard C++ library is needed on top.
|
|
Add the files lodepng.c(pp) and lodepng.h to your project, include
|
|
lodepng.h where needed, and your program can read/write PNG files.
|
|
|
|
It is compatible with C90 and up, and C++03 and up.
|
|
|
|
If performance is important, use optimization when compiling! For both the
|
|
encoder and decoder, this makes a large difference.
|
|
|
|
Make sure that LodePNG is compiled with the same compiler of the same version
|
|
and with the same settings as the rest of the program, or the interfaces with
|
|
std::vectors and std::strings in C++ can be incompatible.
|
|
|
|
CHAR_BITS must be 8 or higher, because LodePNG uses unsigned chars for octets.
|
|
|
|
*) gcc and g++
|
|
|
|
LodePNG is developed in gcc so this compiler is natively supported. It gives no
|
|
warnings with compiler options "-Wall -Wextra -pedantic -ansi", with gcc and g++
|
|
version 4.7.1 on Linux, 32-bit and 64-bit.
|
|
|
|
*) Clang
|
|
|
|
Fully supported and warning-free.
|
|
|
|
*) Mingw
|
|
|
|
The Mingw compiler (a port of gcc for Windows) should be fully supported by
|
|
LodePNG.
|
|
|
|
*) Visual Studio and Visual C++ Express Edition
|
|
|
|
LodePNG should be warning-free with warning level W4. Two warnings were disabled
|
|
with pragmas though: warning 4244 about implicit conversions, and warning 4996
|
|
where it wants to use a non-standard function fopen_s instead of the standard C
|
|
fopen.
|
|
|
|
Visual Studio may want "stdafx.h" files to be included in each source file and
|
|
give an error "unexpected end of file while looking for precompiled header".
|
|
This is not standard C++ and will not be added to the stock LodePNG. You can
|
|
disable it for lodepng.cpp only by right clicking it, Properties, C/C++,
|
|
Precompiled Headers, and set it to Not Using Precompiled Headers there.
|
|
|
|
NOTE: Modern versions of VS should be fully supported, but old versions, e.g.
|
|
VS6, are not guaranteed to work.
|
|
|
|
*) Compilers on Macintosh
|
|
|
|
LodePNG has been reported to work both with gcc and LLVM for Macintosh, both for
|
|
C and C++.
|
|
|
|
*) Other Compilers
|
|
|
|
If you encounter problems on any compilers, feel free to let me know and I may
|
|
try to fix it if the compiler is modern and standards complient.
|
|
|
|
|
|
10. examples
|
|
------------
|
|
|
|
This decoder example shows the most basic usage of LodePNG. More complex
|
|
examples can be found on the LodePNG website.
|
|
|
|
10.1. decoder C++ example
|
|
-------------------------
|
|
|
|
#include "lodepng.h"
|
|
#include <iostream>
|
|
|
|
int main(int argc, char *argv[])
|
|
{
|
|
const char* filename = argc > 1 ? argv[1] : "test.png";
|
|
|
|
//load and decode
|
|
std::vector<unsigned char> image;
|
|
unsigned width, height;
|
|
unsigned error = lodepng::decode(image, width, height, filename);
|
|
|
|
//if there's an error, display it
|
|
if(error) std::cout << "decoder error " << error << ": " << lodepng_error_text(error) << std::endl;
|
|
|
|
//the pixels are now in the vector "image", 4 bytes per pixel, ordered RGBARGBA..., use it as texture, draw it, ...
|
|
}
|
|
|
|
10.2. decoder C example
|
|
-----------------------
|
|
|
|
#include "lodepng.h"
|
|
|
|
int main(int argc, char *argv[])
|
|
{
|
|
unsigned error;
|
|
unsigned char* image;
|
|
size_t width, height;
|
|
const char* filename = argc > 1 ? argv[1] : "test.png";
|
|
|
|
error = lodepng_decode32_file(&image, &width, &height, filename);
|
|
|
|
if(error) printf("decoder error %u: %s\n", error, lodepng_error_text(error));
|
|
|
|
/ * use image here * /
|
|
|
|
free(image);
|
|
return 0;
|
|
}
|
|
|
|
11. state settings reference
|
|
----------------------------
|
|
|
|
A quick reference of some settings to set on the LodePNGState
|
|
|
|
For decoding:
|
|
|
|
state.decoder.zlibsettings.ignore_adler32: ignore ADLER32 checksums
|
|
state.decoder.zlibsettings.custom_...: use custom inflate function
|
|
state.decoder.ignore_crc: ignore CRC checksums
|
|
state.decoder.color_convert: convert internal PNG color to chosen one
|
|
state.decoder.read_text_chunks: whether to read in text metadata chunks
|
|
state.decoder.remember_unknown_chunks: whether to read in unknown chunks
|
|
state.info_raw.colortype: desired color type for decoded image
|
|
state.info_raw.bitdepth: desired bit depth for decoded image
|
|
state.info_raw....: more color settings, see struct LodePNGColorMode
|
|
state.info_png....: no settings for decoder but ouput, see struct LodePNGInfo
|
|
|
|
For encoding:
|
|
|
|
state.encoder.zlibsettings.btype: disable compression by setting it to 0
|
|
state.encoder.zlibsettings.use_lz77: use LZ77 in compression
|
|
state.encoder.zlibsettings.windowsize: tweak LZ77 windowsize
|
|
state.encoder.zlibsettings.minmatch: tweak min LZ77 length to match
|
|
state.encoder.zlibsettings.nicematch: tweak LZ77 match where to stop searching
|
|
state.encoder.zlibsettings.lazymatching: try one more LZ77 matching
|
|
state.encoder.zlibsettings.custom_...: use custom deflate function
|
|
state.encoder.auto_convert: choose optimal PNG color type, if 0 uses info_png
|
|
state.encoder.filter_palette_zero: PNG filter strategy for palette
|
|
state.encoder.filter_strategy: PNG filter strategy to encode with
|
|
state.encoder.force_palette: add palette even if not encoding to one
|
|
state.encoder.add_id: add LodePNG identifier and version as a text chunk
|
|
state.encoder.text_compression: use compressed text chunks for metadata
|
|
state.info_raw.colortype: color type of raw input image you provide
|
|
state.info_raw.bitdepth: bit depth of raw input image you provide
|
|
state.info_raw: more color settings, see struct LodePNGColorMode
|
|
state.info_png.color.colortype: desired color type if auto_convert is false
|
|
state.info_png.color.bitdepth: desired bit depth if auto_convert is false
|
|
state.info_png.color....: more color settings, see struct LodePNGColorMode
|
|
state.info_png....: more PNG related settings, see struct LodePNGInfo
|
|
|
|
|
|
12. changes
|
|
-----------
|
|
|
|
The version number of LodePNG is the date of the change given in the format
|
|
yyyymmdd.
|
|
|
|
Some changes aren't backwards compatible. Those are indicated with a (!)
|
|
symbol.
|
|
|
|
*) 18 apr 2016: Changed qsort to custom stable sort (for platforms w/o qsort).
|
|
*) 09 apr 2016: Fixed colorkey usage detection, and better file loading (within
|
|
the limits of pure C90).
|
|
*) 08 dec 2015: Made load_file function return error if file can't be opened.
|
|
*) 24 okt 2015: Bugfix with decoding to palette output.
|
|
*) 18 apr 2015: Boundary PM instead of just package-merge for faster encoding.
|
|
*) 23 aug 2014: Reduced needless memory usage of decoder.
|
|
*) 28 jun 2014: Removed fix_png setting, always support palette OOB for
|
|
simplicity. Made ColorProfile public.
|
|
*) 09 jun 2014: Faster encoder by fixing hash bug and more zeros optimization.
|
|
*) 22 dec 2013: Power of two windowsize required for optimization.
|
|
*) 15 apr 2013: Fixed bug with LAC_ALPHA and color key.
|
|
*) 25 mar 2013: Added an optional feature to ignore some PNG errors (fix_png).
|
|
*) 11 mar 2013 (!): Bugfix with custom free. Changed from "my" to "lodepng_"
|
|
prefix for the custom allocators and made it possible with a new #define to
|
|
use custom ones in your project without needing to change lodepng's code.
|
|
*) 28 jan 2013: Bugfix with color key.
|
|
*) 27 okt 2012: Tweaks in text chunk keyword length error handling.
|
|
*) 8 okt 2012 (!): Added new filter strategy (entropy) and new auto color mode.
|
|
(no palette). Better deflate tree encoding. New compression tweak settings.
|
|
Faster color conversions while decoding. Some internal cleanups.
|
|
*) 23 sep 2012: Reduced warnings in Visual Studio a little bit.
|
|
*) 1 sep 2012 (!): Removed #define's for giving custom (de)compression functions
|
|
and made it work with function pointers instead.
|
|
*) 23 jun 2012: Added more filter strategies. Made it easier to use custom alloc
|
|
and free functions and toggle #defines from compiler flags. Small fixes.
|
|
*) 6 may 2012 (!): Made plugging in custom zlib/deflate functions more flexible.
|
|
*) 22 apr 2012 (!): Made interface more consistent, renaming a lot. Removed
|
|
redundant C++ codec classes. Reduced amount of structs. Everything changed,
|
|
but it is cleaner now imho and functionality remains the same. Also fixed
|
|
several bugs and shrunk the implementation code. Made new samples.
|
|
*) 6 nov 2011 (!): By default, the encoder now automatically chooses the best
|
|
PNG color model and bit depth, based on the amount and type of colors of the
|
|
raw image. For this, autoLeaveOutAlphaChannel replaced by auto_choose_color.
|
|
*) 9 okt 2011: simpler hash chain implementation for the encoder.
|
|
*) 8 sep 2011: lz77 encoder lazy matching instead of greedy matching.
|
|
*) 23 aug 2011: tweaked the zlib compression parameters after benchmarking.
|
|
A bug with the PNG filtertype heuristic was fixed, so that it chooses much
|
|
better ones (it's quite significant). A setting to do an experimental, slow,
|
|
brute force search for PNG filter types is added.
|
|
*) 17 aug 2011 (!): changed some C zlib related function names.
|
|
*) 16 aug 2011: made the code less wide (max 120 characters per line).
|
|
*) 17 apr 2011: code cleanup. Bugfixes. Convert low to 16-bit per sample colors.
|
|
*) 21 feb 2011: fixed compiling for C90. Fixed compiling with sections disabled.
|
|
*) 11 dec 2010: encoding is made faster, based on suggestion by Peter Eastman
|
|
to optimize long sequences of zeros.
|
|
*) 13 nov 2010: added LodePNG_InfoColor_hasPaletteAlpha and
|
|
LodePNG_InfoColor_canHaveAlpha functions for convenience.
|
|
*) 7 nov 2010: added LodePNG_error_text function to get error code description.
|
|
*) 30 okt 2010: made decoding slightly faster
|
|
*) 26 okt 2010: (!) changed some C function and struct names (more consistent).
|
|
Reorganized the documentation and the declaration order in the header.
|
|
*) 08 aug 2010: only changed some comments and external samples.
|
|
*) 05 jul 2010: fixed bug thanks to warnings in the new gcc version.
|
|
*) 14 mar 2010: fixed bug where too much memory was allocated for char buffers.
|
|
*) 02 sep 2008: fixed bug where it could create empty tree that linux apps could
|
|
read by ignoring the problem but windows apps couldn't.
|
|
*) 06 jun 2008: added more error checks for out of memory cases.
|
|
*) 26 apr 2008: added a few more checks here and there to ensure more safety.
|
|
*) 06 mar 2008: crash with encoding of strings fixed
|
|
*) 02 feb 2008: support for international text chunks added (iTXt)
|
|
*) 23 jan 2008: small cleanups, and #defines to divide code in sections
|
|
*) 20 jan 2008: support for unknown chunks allowing using LodePNG for an editor.
|
|
*) 18 jan 2008: support for tIME and pHYs chunks added to encoder and decoder.
|
|
*) 17 jan 2008: ability to encode and decode compressed zTXt chunks added
|
|
Also various fixes, such as in the deflate and the padding bits code.
|
|
*) 13 jan 2008: Added ability to encode Adam7-interlaced images. Improved
|
|
filtering code of encoder.
|
|
*) 07 jan 2008: (!) changed LodePNG to use ISO C90 instead of C++. A
|
|
C++ wrapper around this provides an interface almost identical to before.
|
|
Having LodePNG be pure ISO C90 makes it more portable. The C and C++ code
|
|
are together in these files but it works both for C and C++ compilers.
|
|
*) 29 dec 2007: (!) changed most integer types to unsigned int + other tweaks
|
|
*) 30 aug 2007: bug fixed which makes this Borland C++ compatible
|
|
*) 09 aug 2007: some VS2005 warnings removed again
|
|
*) 21 jul 2007: deflate code placed in new namespace separate from zlib code
|
|
*) 08 jun 2007: fixed bug with 2- and 4-bit color, and small interlaced images
|
|
*) 04 jun 2007: improved support for Visual Studio 2005: crash with accessing
|
|
invalid std::vector element [0] fixed, and level 3 and 4 warnings removed
|
|
*) 02 jun 2007: made the encoder add a tag with version by default
|
|
*) 27 may 2007: zlib and png code separated (but still in the same file),
|
|
simple encoder/decoder functions added for more simple usage cases
|
|
*) 19 may 2007: minor fixes, some code cleaning, new error added (error 69),
|
|
moved some examples from here to lodepng_examples.cpp
|
|
*) 12 may 2007: palette decoding bug fixed
|
|
*) 24 apr 2007: changed the license from BSD to the zlib license
|
|
*) 11 mar 2007: very simple addition: ability to encode bKGD chunks.
|
|
*) 04 mar 2007: (!) tEXt chunk related fixes, and support for encoding
|
|
palettized PNG images. Plus little interface change with palette and texts.
|
|
*) 03 mar 2007: Made it encode dynamic Huffman shorter with repeat codes.
|
|
Fixed a bug where the end code of a block had length 0 in the Huffman tree.
|
|
*) 26 feb 2007: Huffman compression with dynamic trees (BTYPE 2) now implemented
|
|
and supported by the encoder, resulting in smaller PNGs at the output.
|
|
*) 27 jan 2007: Made the Adler-32 test faster so that a timewaste is gone.
|
|
*) 24 jan 2007: gave encoder an error interface. Added color conversion from any
|
|
greyscale type to 8-bit greyscale with or without alpha.
|
|
*) 21 jan 2007: (!) Totally changed the interface. It allows more color types
|
|
to convert to and is more uniform. See the manual for how it works now.
|
|
*) 07 jan 2007: Some cleanup & fixes, and a few changes over the last days:
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encode/decode custom tEXt chunks, separate classes for zlib & deflate, and
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at last made the decoder give errors for incorrect Adler32 or Crc.
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*) 01 jan 2007: Fixed bug with encoding PNGs with less than 8 bits per channel.
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*) 29 dec 2006: Added support for encoding images without alpha channel, and
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cleaned out code as well as making certain parts faster.
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*) 28 dec 2006: Added "Settings" to the encoder.
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*) 26 dec 2006: The encoder now does LZ77 encoding and produces much smaller files now.
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Removed some code duplication in the decoder. Fixed little bug in an example.
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*) 09 dec 2006: (!) Placed output parameters of public functions as first parameter.
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Fixed a bug of the decoder with 16-bit per color.
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*) 15 okt 2006: Changed documentation structure
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*) 09 okt 2006: Encoder class added. It encodes a valid PNG image from the
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given image buffer, however for now it's not compressed.
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*) 08 sep 2006: (!) Changed to interface with a Decoder class
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*) 30 jul 2006: (!) LodePNG_InfoPng , width and height are now retrieved in different
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way. Renamed decodePNG to decodePNGGeneric.
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*) 29 jul 2006: (!) Changed the interface: image info is now returned as a
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struct of type LodePNG::LodePNG_Info, instead of a vector, which was a bit clumsy.
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*) 28 jul 2006: Cleaned the code and added new error checks.
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Corrected terminology "deflate" into "inflate".
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*) 23 jun 2006: Added SDL example in the documentation in the header, this
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example allows easy debugging by displaying the PNG and its transparency.
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*) 22 jun 2006: (!) Changed way to obtain error value. Added
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loadFile function for convenience. Made decodePNG32 faster.
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*) 21 jun 2006: (!) Changed type of info vector to unsigned.
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Changed position of palette in info vector. Fixed an important bug that
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happened on PNGs with an uncompressed block.
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*) 16 jun 2006: Internally changed unsigned into unsigned where
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needed, and performed some optimizations.
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*) 07 jun 2006: (!) Renamed functions to decodePNG and placed them
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in LodePNG namespace. Changed the order of the parameters. Rewrote the
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documentation in the header. Renamed files to lodepng.cpp and lodepng.h
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*) 22 apr 2006: Optimized and improved some code
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*) 07 sep 2005: (!) Changed to std::vector interface
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*) 12 aug 2005: Initial release (C++, decoder only)
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13. contact information
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-----------------------
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Feel free to contact me with suggestions, problems, comments, ... concerning
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LodePNG. If you encounter a PNG image that doesn't work properly with this
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decoder, feel free to send it and I'll use it to find and fix the problem.
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My email address is (puzzle the account and domain together with an @ symbol):
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Domain: gmail dot com.
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Account: lode dot vandevenne.
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Copyright (c) 2005-2016 Lode Vandevenne
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*/
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