Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!elroy.jpl.nasa.gov!sdd.hp.com!spool.mu.edu!uunet!viusys!alembic!csu From: csu@alembic.acs.com (Dave Mack) Newsgroups: comp.compression Subject: Re: looking for info on image compression Message-ID: <1991Apr2.003452.27382@alembic.acs.com> Date: 2 Apr 91 00:34:52 GMT References: <5043@ns-mx.uiowa.edu> <1991Mar25.215830.5200@nntp-server.caltech.edu> Organization: Alembic Computer Services, McLean VA Lines: 29 In article jaffer@zurich.ai.mit.edu (Aubrey Jaffer) writes: >>jones@pyrite.cs.uiowa.edu writes: >> >>>(PS: Does the use of Ziv-Lempel compression for GIF images mean that >>>the question of patent rights for the Ziv-Lempel algorithm applies to >>>GIF images? > >It definitely does, assuming GIF format uses LZ compression and the >patent is considered valid. Only a lawsuit will determine actual >coverage. If the algorithm differs somewhat from LZ you may be safe >(but consult a lawyer). Much better would be to distribute >replacements for GIF and LZ that are not covered by patents. Except that the patent-holder (Unisys, I believe) has publicly stated that it does not intend to enforce the patent on software implementations, only on hardware implementations of the algorithm. This issue was hacked to death in news.admin a couple of months ago, since LZW compression is also used by the "compress" program which most versions of news use to compress news batches. There is *no* problem with using software implementations of LZW compression for anything, be it GIF encoding or news transport. And your favorite modem manufacturer is already paying royalties to Unisys. Don't sweat it. -- Dave Mack