PNG: The Definitive Guide

 A free book about the PNG image format.
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 This book was published by O'Reilly and it has three parts:
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   - Part I, Using PNG, consists of six chapters and covers the main categories
     of PNG-supporting applications: image editors, viewers, converters, web
     browsers and servers, and 3D apps.
   - Part II, The Design of PNG, also consists of six chapters and looks in
     more detail at PNG as a file format. It covers not only PNG's fundamental
     chunk structure and compression technology but also its history, its
     animated cousin MNG, and some of the intricacies of cross-platform gamma
     and color correction.
   - Part III, Programming with PNG, steps the reader through the design of
     three functional demo programs based on the free libpng C library: rpng,
     a very simple PNG viewer; rpng2, a progressive PNG viewer such as might be
     found in a web browser; and wpng, a basic program to convert RGB image
     data from binary PBMPLUS / NetPBM format into PNG format. The final chapter
     in this section lists a number of other PNG-supporting programming toolkits
     for various languages, including C, C++, Java, Perl, Python, tcl/tk, and
     Visual Basic.