Portable Network Graphics - History and Development

History and Development

See also: Graphics Interchange Format#Unisys and LZW patent enforcement

The motivation for creating the PNG format was in early 1995, after it became known that the Lempel–Ziv–Welch (LZW) data compression algorithm used in the Graphics Interchange Format (GIF) format was patented by Unisys. There were also other problems with the GIF format that made a replacement desirable, notably its limit of 256 colors at a time when computers able to display far more than 256 colors were growing common. Although GIF allows for animation, it was decided that PNG should be a single-image format. A companion format called Multiple-image Network Graphics (MNG) has been defined for animation, whereas a competing format, Animated Portable Network Graphics (APNG), supports backward-compatibility with PNG (which MNG does not).

A January 1995 precursory discussion thread, on the usenet newsgroup "comp.graphics" with the subject Thoughts on a GIF-replacement file format, had many propositions, which would later be part of the PNG file format. In this thread, Oliver Fromme, author of the popular DOS JPEG viewer QPEG, proposed the PING name, meaning PING is not GIF, and also the PNG extension.

• 1 October 1996: Version 1.0 of the PNG specification was released, and later appeared as RFC 2083. It became a W3C Recommendation on 1 October 1996.
• 31 December 1998: Version 1.1, with some small changes and the addition of three new chunks, was released.
• 11 August 1999: Version 1.2, adding one extra chunk, was released.
• 10 November 2003: PNG became an International Standard (ISO/IEC 15948:2003). This version of PNG differs only slightly from version 1.2 and adds no new chunks.
• 3 March 2004: ISO/IEC 15948:2004.