png

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 color space data for improved color matching on heterogeneous platforms.

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

Portable Network Graphics (PNG) Specification (Third Edition):

W3C Recommendation 24 June 2025
https://www.w3.org/TR/2025/REC-png-3-20250624/

Portable Network Graphics (PNG) Specification (Second Edition):

ISO/IEC 15948:2004(E)
https://www.iso.org/standard/29581.html

W3C Recommendation 10 November 2003
https://www.w3.org/TR/2003/REC-PNG-20031110/

Portable Network Graphics (PNG) Specification Version 1.2:

Published by the PNG Development Group on 14 July 1999
https://www.libpng.org/pub/png/spec/1.2/

Portable Network Graphics (PNG) Specification Version 1.1:

Published by the PNG Development Group on 15 February 1999
https://www.libpng.org/pub/png/spec/1.1/

Portable Network Graphics (PNG) Specification Version 1.0:

IETF RFC 2083, March 1997
https://www.ietf.org/rfc/rfc2083.txt

W3C Recommendation 1 October 1996
https://www.w3.org/TR/REC-png-961001

This man page: Glenn Randers-Pehrson, Cosmin Truta, Chris Lilley.

PNG Specification (Third Edition): Chris Blume et al.

PNG Specification (Second Edition): David Duce et al.

PNG Specification Version 1.2: Glenn Randers-Pehrson et al.

PNG Specification Version 1.1: Glenn Randers-Pehrson et al.

PNG Specification Version 1.0: Thomas Boutell et al.