This is the mail archive of the cygwin mailing list for the Cygwin project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: Patent question, libtiff, LZW -- Attn: Corinna

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
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

the fedora core 2 version of netpbm
netpbm-10.19-7.src.rpm in

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.


-- Unsubscribe info: Problem reports: Documentation: FAQ:

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]