In 1977 and 1978, two Israeli researchers, Jacob Ziv and Abraham Lempel worked on a set of compression algorithms, which were later named LZ77 and LZ78. Later, in 1983, Terry Welch from Sperry (which later merged with Burroughs to form Unisys) developed a very fast variant of LZ78 called LZW. Welch, together with two IBM researchers, Victor Miller and Mark Wegman, filled for a patent for LZW.
At the same time, Compuserve, specifically Bob Berry, was designing a new algorithm for a compressed image format, where they used the LZW
The PNG format is a format for lossless raster images, which is able to replace such classic formats as TIFF and GIF. It was designed to work mainly with WWW applications; it is robust and provides integrity checks for the file.
It was designed for the purpose of replacing the GIF format, but it also has additional design properties that were added with small effort from the designers. The features that are implemented in PNG and are absent in GIF format include:
Support for images with up to 48 bits per pixel, in True Color.
The story of PNG actually begins way back in 1977 and 1978 when two Israeli researchers, Jacob Ziv and Abraham Lempel, first published a pair of papers on a new class of lossless data compression algorithms, now collectively referred to as "LZ77'' and "LZ78.'' Some years later, in 1983, Terry Welch of Sperry (which later merged with Burroughs to form Unisys) developed a very fast variant of LZ78 called LZW. Welch also filed for a patent on LZW, as did two IBM researchers, Victor Miller and Mark Wegman. The result was--you guessed it--the USPTO granted
This document has been reviewed by W3C members and other interested parties and has been endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited as a normative reference from another document. W3C's role in making the Recommendation is to draw attention to the specification and to promote its widespread deployment. This enhances the functionality and interoperability of the Web.
A list of current W3C Recommendations and other technical documents can be found at
Status of this Document
This is a revision of the PNG 1.0 specification, which has been published as RFC-2083 and as a W3C Recommendation. The revision has been released by the PNG Development Group but has not been approved by any standards body.
The PNG specification is on a standards track under the purview of ISO/IEC JTC 1 SC 24 and is expected to be released eventually as ISO/IEC International Standard 15948. It is the intent of the standards bodies to maintain backward compatibility with this specification. Implementors should periodically
Portable Network Graphic (PNG, pronounced "ping") is an image format developed by a consortium of graphic software developers as a nonproprietary alternative to the GIF image format. As mentioned earlier, CompuServe developed the GIF format, and GIF uses the proprietary LZW compression scheme owned by Unisys Corporation. Any graphics tool developer who makes software that saves in GIF format must pay a royalty to Unisys and CompuServe.
PNG graphics were designed specifically for use on Web pages, and they offer a range of attractive features that
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