png - Man Page

PNG (Portable Network Graphics) is an extensible file format for the lossless, portable, well-compressed storage of raster images.  PNG provides a patent-free replacement for GIF, and can also replace many common uses of TIFF. Indexed-color, grayscale, and truecolor images are supported, plus an optional alpha channel.  Sample depths range from 1 to 16 bits.
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.

libpng(3), zlib(3), deflate(5), and zlib(5)

PNG Specification (Second Edition), November 2003:

https://www.w3.org/TR/2003/REC-PNG-20031110/

PNG 1.2 Specification, July 1999:

https://png-mng.sourceforge.io/pub/png/spec/1.2/

PNG 1.0 Specification, October 1996:

RFC 2083
https://www.ietf.org/rfc/rfc2083.txt

or W3C Recommendation
https://www.w3.org/TR/REC-png-961001

This man page: Glenn Randers-Pehrson, Cosmin Truta

Portable Network Graphics (PNG) Specification (Second Edition) Information technology - Computer graphics and image processing - Portable Network Graphics (PNG): Functional specification. ISO/IEC 15948:2003 (E) (November 10, 2003): David Duce and others.

Portable Network Graphics (PNG) Specification Version 1.2 (July 8, 1999): Glenn Randers-Pehrson and others.

Portable Network Graphics (PNG) Specification Version 1.0 (October 1, 1996): Thomas Boutell and others.

jng(5), libmng(3), libpng(3), libpngpf(3), mng(5), optipng(1), pngcrush(1), pngnq(1), tuxpaint-import(1).