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Date: Wed, 31 Jan 2007 13:04:57 -0600 (CST)
From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
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To: Reinhard Mayr aka Czerwinski <czerwinski1977@gmx.net>
Subject: Re: [Tiff] 16bit grayscale with colormap
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Status:   

On Wed, 31 Jan 2007, Reinhard Mayr aka Czerwinski wrote:

> Hmmm ... I go the same message with ImageMagick's imdisplay.exe. 
> Maybe the error message is just a bit too un-exact: the color map is 
> there (according to the dump), maybe it's just about the unexpected 
> length of 192kB instead of 256 byte? The values of the dump 
> represent exactly what I have in the color map (repeated ASCII 
> "0123456789ABCDEF").
>
> Does GraphMagick do a length check for that tag?

No, initially GraphicsMagick just requests the tag from libtiff.  It 
is libtiff producing the error before GraphicsMagick has a chance to 
do anything with it.  Maybe libtiff includes length checks or maybe 
there is some other issue.  A wrong length could be used to 'trojan' 
or crash some applications so assuring the correct length is 
important.

Joris has a TIFF inspection tool which should help to diagnose the 
issue with your file.

Bob
======================================
Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

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