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1998.11.18 13:50 "Re: lzw decompression.", by James Palo
Some companies early on did try to take them to court and Unisys spent a large sum to enforce the patent. There is no justice , in the legal system its who has the most money. Most companies have just paid Unisys since it was cheaper than fighting the patent. For the record the patent states: The compression of a serial character stream for transmission. Which should not really apply to Gif or lzw reading of images. But this is a fight you will not win win Unisys. Most companies have just not used the lzw. Lzw is not lz the w is Welch at Unisys added using a string table when compressing. There are a large number of patents on all sorts of variants of LZ, LZW and even the zlib compression is LZ77 which is supposed to be patent free. We do need a good lossless compression, but zlib used in the PNG format is to complicated for general widespread use. Jim Palo Snowbound Software At 11:50 AM 11/17/98 -0500, Larry Jones wrote: >Adam Rybicki writes: >> >> "Eric J. Schwertfeger" wrote: >> > >> > The patent only covers compression, not decompression. >> >> Sorry, but I don't think Unisys would agree with you: >> http://corp2.unisys.com/LeadStory/lzwfaq.html > >It doesn't really matter whether Unisys agrees or not -- LZW >decompression is *exactly* the same as LZ decompression, which is not >patented. > >It's really too bad that Unisys can't make money any other way than by >trying to extort license revenue out of an invalid patent. It's also >too bad that someone with deep pockets hasn't cared enough to take them >to court and get it officially declared invalid. > >-Larry Jones > >Sheesh. Who can fathom the feminine mind? -- Calvin > Best regards Jim Palo <palo@snowbnd.com> Snowbound Software tel: 617 630-9495 fax 617 630-0210 website: http://www.snowbnd.com Imaging Software - Powerful, fast, reliable