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Date: Wed, 31 Jan 2007 11:06:36 -0600 (CST)
From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
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To: Toby Thain <toby@smartgames.ca>
Subject: Re: [Tiff] 16bit grayscale with colormap
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Status:   

On Wed, 31 Jan 2007, Toby Thain wrote:
>> 
>> I deal with 16bit grayscale TIFFs. The files originate from a 12bit CCD, 
>> so the linear conversion 16bit->8bit turns my image almost black.
>
> Maybe I'm missing something, but why don't you just multiply by 16 before 
> storing in TIFF?

It is worth mentioning that some companies dealing with these 12bit 
CCDs write TIFFs using 12-bit samples.  This is pretty rare in TIFF 
but seems acceptable if you have control over the reader.  I have been 
provided with a number of sample files.  GraphicsMagick 1.2 can 
read/write them.

Converting from 16-bits (or 12-bits) to 8 bits is very bad since even 
though the image may appear 'black' upon initial viewing, there is 
actually far more detail in the image than could be represented in 8 
bits and converting to fewer bits loses the original levels (which may 
have some scientific value).

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

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