Re: GIF encoding

Roedy Green wrote:
On Tue, 25 Sep 2007 16:04:43 GMT, "Andrew Thompson" <u32984@uwe>
wrote, quoted or indirectly quoted someone who said :

I had not realised GIF's could have 'compression'.

This is a sore point Unisys got hold of the patent to LZW compression
used in GIF and they started threatening people with it. It is
expired now, though you never know what a lawyer could do.

I think though your code does do LZW, thumbing its nose at Unisys.

The US LZW patent expired on June 20, 2003. The counterpart patents in the United Kingdom, France, Germany and Italy expired on June 18, 2004, the Japanese counterpart patents expired on June 20, 2004 and the counterpart Canadian patent expired on July 7, 2004. Consequently, while Unisys has further patents and patent applications relating to improvements to the LZW technique, the GIF format may now be used freely.

I believe Sun added in to Java 6 full GIF compatibility in ImageIO because the patents had long since expired by then.

LZW compression as implemented in GIF is now fully free!

--
Beware of bugs in the above code; I have only proved it correct, not tried it. -- Donald E. Knuth
.

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