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Last Updated: Sunday, 22 June, 2003, 11:26 GMT 12:26 UK
Graphics format wins freedom
Suitcase full of cash, BBC/Corbis
Friday 20 June has been dubbed Gif Liberation Day as net users the world over celebrate the end of a costly patent agreement.

The patent for the Lempel-Ziv-Welch, or LZW, compression algorithm is set to expire in the US on Friday. It also expires in Europe, Canada and Japan in June of 2004.

The patent claiming ownership of the file squashing format was lodged by Unisys in 1994 and underpins one of the web's most popular ways of encoding graphics files.

LZW forms the basis of the popular Gif format (Graphics Interchange Format), a way of storing and sending images on the internet.

Controversial call

The Unisys patent, which has the number 4,558,302, has caused a fair share of controversy over the years.

Web developers were dismayed when Unisys began demanding fees for the already hugely popular format in 1994.

Some commentators believe the expiry of the patent could lead to the price of image editing applications such as Adobe's Photoshop falling slightly as software makers will no longer be paying licensing fees to Unisys.

It could also sound the death knell for a rival format called the Portable Network Graphics (PNG) format, which was developed specifically to provide a free alternative to royalty-laden Gifs.

The PNG format has never been as popular as Gifs and has now lost a substantial part of its raison d'etre, say experts.

Anti-patent activists are likely to maintain their allegiance to PNG as a symbolic gesture against patent holders such as Unisys.

The Gif patent has been likened to an internet tax and activists have, over the years, organised a series of "Burn All Gifs Days"' in protest over Unisys' patent demands.

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