Message-ID: 3AFEA017.A6F1A473@pobox.com
To: "Rishel,Wes" <wes.rishel@gartner.com>
Subject: Re: TIFF/CCITT Group 4 Compression uses LZW??
From: Frank Warmerdam <warmerdam@pobox.com>
Date: Sun, 13 May 2001 10:54:15 -0400
Cc: "'tiff@olympiakos.com'" <tiff@olympiakos.com>
References: <8647AD35DEC2D411A4DD0002A513481A397D82@mammoth.gartner.com>
Reply-To: warmerdam@pobox.com
Sender: owner-tiff@olympiakos.com


"Rishel,Wes" wrote:
> 
> 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?

Wes,

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,

---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam@pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

