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From: russotto@eng.umd.edu (Matthew T. Russotto)
Newsgroups: comp.sys.apple2
Subject: Re: //gs graphics/music
Message-ID: <1990Nov30.063819.2814@eng.umd.edu>
Date: 30 Nov 90 06:38:19 GMT
References: <234@generic.UUCP>
Sender: news@eng.umd.edu (C-News)
Organization: College of Engineering, Maryversity of Uniland, College Park
Lines: 21

In article <234@generic.UUCP> taob@pnet91.cts.com (Brian Tao) writes:
>> If anyone KNOWS what this means to PD/Freeware implementations of LZW (such
>> as all our favourite GIF decoders and Shrinkit), please pass this on.
>>
>> John MacLean. 
>
>    Andy Nicholas uses a modified version of LZW called LZW/2 in GS/ShrinkIt
>(and presumably ShrinkIt 3.03).  Whether or not this is compatible with normal
>LZW is a different question.  What about all those PD GIF viewers on MS-DOS
>machines?  Do they all have the GIF/LZW algorithm licensed?

Unisys seems to think so.  IMO, they can take their patent, fold it until it
is all corners....

LZW/1 and LZW/2 are both minor variants on LZW-- they just are broken into
4096 byte blocks, essentially.  LZW/1 clears after 4096 bytes, LZW/2 has
an explicit clear code.  There is some header information in front of each
block.
--
Matthew T. Russotto	russotto@eng.umd.edu	russotto@wam.umd.edu
     .sig under construction, like the rest of this campus.