PNG is designed to work well in online viewing applications, such as the World Wide Web, so it is fully streamable with a progressive display option. PNG is robust, providing both full file integrity checking and fast, simple detection of common transmission errors. Also, PNG can store gamma and chromaticity data for improved color matching on heterogeneous platforms.
PNG 1.2 specification, July 1999:
http://www.libpng.org/pub/png
or ftp://ftp.uu.net/graphics/png/documents
PNG 1.0 specification, October 1996:
RFC 2083
ftp://ds.internic.net/rfc/rfc2083.txt
or (as a W3C Recommendation) at
http://www.w3.org/TR/REC-png.html
Portable Network Graphics (PNG) Specification Version 1.2 (July 8, 1999): Glenn Randers-Pehrson and others (png-list@ccrc.wustl.edu).
Portable Network Graphics (PNG) Specification Version 1.0 (October 1, 1996): Thomas Boutell and others (png-list@ccrc.wustl.edu).
The PNG-1.0 specification is copyright (c) 1996 Massachusetts Institute of Technology. See the specification for conditions of use and distribution.
end of man page