2001.05.12 23:08 "TIFF/CCITT Group 4 Compression uses LZW??", by Wes Rishel

2001.05.13 14:54 "Re: TIFF/CCITT Group 4 Compression uses LZW??", by Frank Warmerdam

I have a file which, according to the GNU utility tiffinfo is a Group 4 TIFF (see below).

When I run the utility thumbnail against the image I get the message "thumb.tif: LZW compression no longer supported due to Unisys patent enforcement."

I am a bit surprised find that Group 4 compression would use LZW or be reliant on any patented algorithm. Does anyone know if that is, indeed the case? Or is it more likely that the error message is incorrect, perhaps triggered by the unknown field identified by tiffinfo?


I looked at thumbnail and I see it defaults to using LZW compression for the generated thumbnails. This is what triggers the error report, not any LZWishness of G4. I have corrected this in CVS, but if you want to use thumbnail you will need to change COMPRESSION_LZW to something else like COMPRESSION_PACKBITS and recompile the program.

Thanks for the report.

Best regards,

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