GIF

GIF (Graphics Interchange Format) is a bitmap image format for pictures that use 256 (or fewer) distinct colors (though there is a workaround for this limitation). and animations that use 256 (or fewer) distinct colors per frame. GIFs are compressed files, and are employed specifically to reduce the amount of time it takes to transfer images over a network connection. The format was introduced by CompuServe in 1987 and has since come into widespread usage on the World Wide Web.

Unisys and LZW patent enforcement

The LZW compression algorithm on which GIF is based, was covered by {{US patent|4,558,302}} owned by Unisys. When Compuserve first developed the GIF they did not know that LZW was covered by a patent. In December 1994, after Unisys discovered that GIF used the LZW, they announced that they would be seeking royalties on that patent; all commercial programs capable of producing GIF files would be required to pay a license fee to Unisys.

Related Topics:
Unisys - Patent - 1994

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By this time, GIF was in such widespread use that most companies producing these programs had little choice but to pay. In late August 1999, Unisys terminated its royalty-free LZW technology licenses for free software and non-commercial proprietary software and even for individual users of unlicensed programs, prompting the League for Programming Freedom to launch the Burn All GIFs campaign to inform the public of the alternatives.

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On June 20, 2003, the United States patent on the LZW algorithm expired http://www.unisys.com/about__unisys/lzw, which means that Unisys and Compuserve can no longer collect royalties for use of the GIF format in that country. Those bothered with the patent enforcement dubbed this day GIF Liberation Day. The equivalent patents in Europe and Japan expired on June 18 and June 20 2004 respectively, with the Canada patent following on July 7.

Related Topics:
June 20 - 2003 - June 18 - 2004 - July 7

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IBM has also patented the LZW algorithm, but has never enforced this patent. According to the Free Software Foundation that patent will expire on August 11 2006 in the United States.

Related Topics:
Free Software Foundation - August 11 - 2006

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