GIF

The GIF image format is widely used on the World Wide Web. To make a GIF image, the LZW algorithm is required. Until 2004, this algorithm had problems with patent problems that were aggressively used.

After this format became widely used, a company called Unisys began threatening developers and distributors with patent infringement based on a 1983 patent, US-4,464,650. (patent ambush)

As of 2004, that patent is expired and GIF is generally considered to be free of patent problems.

Related pages on en.swpat.org

• Harm to standards
• Campaigns to avoid patented ideas

External links

• Burn All Gifs - an old LPF project encouraging people not to use .gif images
• Wikipedia: GIF - Unisys_and_LZW_patent_enforcement
• James S. Huggins' summary
• The story of PostScript, GIF, and PNG, told by Richard Stallman
• Wikipedia: Submarine patents and Patent ambush

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