Re: programmatically decompress lzw data
Re: programmatically decompress lzw data
- Subject: Re: programmatically decompress lzw data
- From: "Alastair J.Houghton" <email@hidden>
- Date: Fri, 5 Sep 2003 13:00:57 +0100
On Friday, September 5, 2003, at 03:43 am, Dennis C.De Mars wrote:
I believe that your belief is wrong and that in fact both compression
and decompression are covered by patents (except in the U.S., but still
covered in other places for awhile: see below).
Here's some more information I gleaned with Google which might be of
general interest:
http://www.unisys.com/about__unisys/lzw
has the hard information on patent expiration. You still have to be a
little careful, since it is the U.S. Patent only that has expired.
There are separate patents in Canada, Japan and the U.K. and various
other European countries that all expire within a few days of each
other in the middle of 2004. (Late June - early July)
I don't know about Canada or Japan, but LZW patents in the EU have
dubious legality; the European patent office and its counterparts in
the various member states aren't actually allowed to issue patents on
software algorithms (sadly, it hasn't stopped them from doing it).
There is currently considerable pressure from the UK Patent Office and
a group of large software companies (notably IBM and Microsoft) to make
the issuing of such patents legal, which is a bit unfortunate given the
effect they often seem to have (LZW is a good example).
I was slightly disturbed to note that using Microsoft APIs to
read/write GIF images (or for any other LZW-related purpose) was
regarded by Unisys as an application of its patent for which you need a
license; I wonder if they have the same opinion regarding Apple's APIs?
Still, you'd need to consult a patent lawyer before coming to a
conclusion regarding patent liability.
Kind regards,
Alastair.
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