TIFF and LibTiff Mail List Archive


1999.11.30 22:23 "libtiff 3.5.3 release.", by Michael L. Welles
1999.11.30 22:53 "Re: libtiff 3.5.3 release.", by Izumi Ohzawa
1999.11.30 23:07 "Re: libtiff 3.5.3 release.", by Tom Lane
1999.12.01 00:08 "Re: libtiff 3.5.3 release.", by Michael L. Welles
1999.11.30 23:22 "Re: libtiff 3.5.3 release.", by Daniel McCoy
1999.12.01 03:15 "Re: libtiff 3.5.3 release.", by Bob Friesenhahn

1999.11.30 23:07 "Re: libtiff 3.5.3 release.", by Tom Lane

Now, I need a solid reference that LZW decompression is not covered by the LZW patent. Nothing I have read, except for opinions or second-hand quotes at various forums, clearly indicates that decompression is not part of the patent.

Especially, does anyone have written views from the Unisys itself on this?

Unisys' view is perfectly clear: they claim that decompression-only software *is* covered by the patent. (They have a webpage giving their version of reality at, check there for an exact quote.)

There are a number of qualified people who think that Unisys' interpretation wouldn't hold up in court, and that a court would say that decompression-only software isn't covered. But AFAIK there's been no test case to find out. Do you want to be the test case?

Regardless of what court may or may not rule in the end, that doesn't matter. Most of us here, I think, just don't want to hear from Unisys counsels, ever.

Yup. That's why I'm not shipping either LZW compression or decompression code in libjpeg these days. It was a relatively painless decision for me, because GIF-reading was never a critical part of libjpeg, but I can see that dropping the LZW decompressor would be crippling for libtiff :-(. Don't have any good advice...

regards, tom lane
organizer, Independent JPEG Group