1999.02.11 18:09 "LZW Encoding and Decoding", by Frank Warmerdam


The LZW issue has been extensively discussed with regard to GIF (which also uses it). On the GIFLIB web page (http://prtr-13.ucsc.edu/~badger/software/giflib.shtml) I see:

``Patent lawyers seem to agree that the wording of the Unisys patent is such that code which does decoding only (and not encoding) is not covered by the patent, so you may be safe using this library. [Note: Unisys has at times expressed views which seem to disagree with this interpretation. If you're concerned, speak to a lawyer yourself.]''

The page ``The GIF Controversy: A Software Developer's Perspective'' may also be of interest:


I would suggest that applications written with libtiff should not allow users to compress with LZW if you want to be safe, but that allowing the decompression should be safe.

Best regards,

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