COPYRIGHT

pngquant and libimagequant are derived from code by Jef Poskanzer and Greg Roelofs
licensed under pngquant's original licenses (near the end of this file),
and contain extensive changes and additions by Kornel Lesiński
licensed under GPL v3 or later.

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pngquant © 2009-2018 by Kornel Lesiński.

                    GNU GENERAL PUBLIC LICENSE
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The quantization and dithering code in pngquant is lifted from Jef Poskanzer's
'ppmquant', part of his wonderful PBMPLUS tool suite.

Greg Roelofs hacked it into a (in his words) "slightly cheesy" 'pamquant' back
in 1997 (see http://pobox.com/~newt/greg_rgba.html) and finally he ripped out
the cheesy file-I/O parts and replaced them with nice PNG code in December
2000. The PNG reading and writing code is a merged and slightly simplified
version of readpng, readpng2, and writepng from his book "PNG: The Definitive
Guide."
In 2014 Greg has relicensed the code under the simplified BSD license.

Note that both licenses are basically BSD-like; that is, use the code however
you like, as long as you acknowledge its origins.

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pngquant.c:

   © 1989, 1991 by Jef Poskanzer.

   Permission to use, copy, modify, and distribute this software and its
   documentation for any purpose and without fee is hereby granted, provided
   that the above copyright notice appear in all copies and that both that
   copyright notice and this permission notice appear in supporting
   documentation.  This software is provided "as is" without express or
   implied warranty.

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pngquant.c and rwpng.c/h:

   © 1997-2002 by Greg Roelofs; based on an idea by Stefan Schneider.

   All rights reserved.

   Redistribution and use in source and binary forms, with or without modification,
   are permitted provided that the following conditions are met:

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