Technical articles on the PNG file format and the related compression technologies

This site contains a collection of comments, impressions, comparisons, experiments and ideas regarding the PNG (Portable Network Graphics) file format, and the related technologies: ZLIB (Data Compression Format and Library), and MNG (Multiple-Image Network Graphics). It is focused on the compression algorithms used in PNG.
PNG uses ZLIB streams [RFC1950] as compressed datastreams. The compression algorithm, called Deflate [RFC1951], was designed by Phil Katz and used initially in PKZIP.
Jean-loup Gailly and Mark Adler rewrote the code, avoiding any patented algorithms. This code, freely available in source, can be found here. Additional technical details are provided here.
A good explanation of the Deflate algorithm by Antaeus Feldspar is available here.
We use the term ZLIB (written with capital letters) when we refer to the standard or to standard-compliant streams, and the term zlib (written with small letters) when we refer to the reference implementation.

ZLIB-related articles
PNG-related articles
MNG-related articles

Valid HTML 4.0! PNG Now!
Copyright © 2000-2011 Cosmin TruĊ£a.
Appeared: 16 Jan 2000. Last updated: 31 Mar 2011.