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September 14, 1995


By CBR Staff Writer

Remember all the fuss at the end of last year when Unisys Corp got all proprietorial about the GIF Graphics Interchange Format and its underlying Lemple-Ziv & Welch compression routine (CI No 2,574)? Unisys revived an elderly patent and said it would require royalties for any new software supporting the .GIF format. The move was widely interpreted at the time as a dubious use of patent law and software developers vowed to establish a genuinely free standard to avoid paying royalties. In January (CI No 2,538) a consortium of Internet graphics developers led by Seattle-based programmer and author Thomas Boutell, and including Jean-Loup Gailly and Mark Adler, the developers of Deflate and Inflate, got together to draft what it called the Portable Network Graphics specification – to be known as PNG (pronounced ‘ping’). The move was supported by CompuServe Inc, the company most directly affected by the Unisys decision. CompuServe abandoned its own GIF24 effort in favour of PNG and contributed technical resources to its completion. By May, the specification was complete. PNG improves on GIF by supporting a true 24-bit lossless format giving users a 16m colour palette, along with faster compression and other improvements. CompuServe has a free tool kit for creating graphics that meet the PNG specification, which it is freely distributing. Because of the patent issues, PNG is not backwards-compatible with GIF, but CompuServe has a conversion utility for use in conjunction with the CompuServe Information Services. Since then support for the new format has grown steadily, including the National Center for Supercomputing Applications (the people that developed Mosaic), Spyglass Inc, NetScape Communications Corp and the WWW Consortium. In July, PNG made it onto the cover of Dr Dobb’s Journal. To date, nearly 80 applications support the format, including browsers, image viewers and editors, image conversion applications and various utilities. The whole thing illustrates how quickly new open systems standards can be established nowadays, at least away from the more formal standards bodies. And it looks as if Unisys won’t be getting the benefit of a royalty stream that many feel it did not deserve in the first place.

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