Patent question, libtiff, LZW -- Attn: Corinna

[Charles Wilson]

Corinna Vinschen wrote:

> On Oct 10 17:48, Charles Wilson wrote:
> 
>>So, to release the latest version of libtiff (3.7.0beta2) I need to do 
>>one of the following:
>>  (1) get permission from Red Hat (it's their server, after all) to 
>>publish an LZW-enabled libtiff
>>  (2) rip the LZW stuff back out
>>
>>I'd prefer (1).  Corinna?
> 
> 
> Fedora is using 3.6.1 right now.

For libtiff.  But LZW as employed by gif, Red Hat is already 
distributing in fedora via netpbm.  See below.

>  I'd feel better if we're not on the
> bleeding edge of patenting issues...

Horse has already left the barn.

Yeesh.  In 3.6.x and earlier, if you did not apply the lzw patch, then 
libtiff could decode lzw-compressed tiff, but could not encode them (if 
I am reading the code correctly).  However, with 3.7.x and later, if you 
configure using
   --disable-lzw
then ALL lzw support is turned off.  So to make 3.7.x "like before" 
requires a lot of work.

And this won't get any better.  libtiff development will keep marching 
forward, until that 2006 IBM patent expiration.  I really don't want to 
maintain an out-of-tree patch for that long -- which is necessary to 
preserve current functionality (e.g. continue to allow lzw reading).

It seems that the relevant issues for a lawyer to verify are:

   (1) UniSys patent was on the LZW algorithm, a derivative of LZ78.
   (2) IBM patent was on the LZMW algorithm, a different derivative of LZ78.
   (3) GIF and TIFF use LZW, which was covered by the UniSys patent.
   (4) GIF and TIFF are not (?? verify ??) covered by the IBM patent.
   (5) UniSys patent is expired.
   (6) IBM patent expires in two years.
   (7) LZW decompression is not covered under any existing patent 
(Actually, legal opinions here vary, but see below)

In any case,

the fedora core 1 version of netpbm netpbm-9.24-12.1.1.src.rpm in
http://download.fedora.redhat.com/pub/fedora/linux/core/updates/1/SRPMS/
and

the fedora core 2 version of netpbm
netpbm-10.19-7.src.rpm in
http://download.fedora.redhat.com/pub/fedora/linux/core/2/SRPMS/

both contain giftopnm and ppmtogif, which are LZW-enabled for both 
decompression (giftopnm) and compression (ppmtogif).

So it seems that this is really a moot point.  Red Hat is already 
distributing LZW-enabled code.

--
Chuck


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