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zopflib/src/zopflipng/lodepng/lodepng.h  view on Meta::CPAN

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.

*) 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