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Date: Tue, 25 Oct 2005 09:37:16 -0500 (CDT)
From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
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To: ryuki_dono <ryuki_dono@yahoo.de>
Subject: Re: [Tiff] Re: checking test images
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Status:   

On Tue, 25 Oct 2005, ryuki_dono wrote:

> Since there was no reply yet I debuged the problem. Here are the tifflib 
> warnings and errors for the testimages 
> (http://www.remotesensing.org/libtiff/images.html).

[ stuff removed ]

> I didn't know that libtiff was so limited. Or did I something wrong? I think 
> quad-jpeg and zackthecat can't
> be decoded because of my missing JPEG support in my build. But whats with all 
> the 2 to 64 Bit pixeldepth?
> What's with the contig files?

Libtiff does a good job of supporting "normal" TIFF files on its own. 
The more exotic sample TIFF files were written using libtiff, but with 
the assistance of higher-level software (development GraphicsMagick 
1.2).  It is only a minor libtiff deficiency that these files are not 
supported out of the box by libtiff although it would be useful for 
libtiff to support reading 12 bit data via the 8-bit RGB interfaces 
(with obvious loss of precision).  There is partial support in libtiff 
now for reading 12-bit JPEG data in TIFF (12-bit data can be returned 
to the user).

The libtiff "RGB" APIs are simplified interfaces which assume that all 
images can be converted to 8-bit RGB.  This fails miserably for 16-bit 
TIFFs, and is terribly inefficient for bilevel images.  However, it is 
not necessary to use these simplified interfaces.  These interfaces 
should only be used by trivial applications, or for applications where 
TIFF is only a minor format.

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