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Date: Wed, 17 Jan 2007 11:01:07 -0600 (CST)
From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
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To: Joris <joris.at.lebbeke@skynet.be>
Subject: Re: [Tiff] Elevation Data
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Status:   

On Wed, 17 Jan 2007, Joris wrote:
>
> Grissom, Ed wrote:
>> But....  I don't see any disclaimer on SMin/Smax   (Min/Max, sure, but
>> not SMin/SMax)
>
> I should have double-checked first. From the spec parts you've quoted,
> it seems there is indeed no 'disclaimer' on SMin/SMax. So, my bad.
>
> Though, still, have you seen many actual use of these tags in the
> implied sense? If you've test images that do use them this way, I'd be
> very grateful for a copy.

I believe that development GraphicsMagick 1.2 uses these tags when it 
outputs (and reads) floating point TIFFs.  The tags are assumed to 
indicate min and max values that bound the data range.  They don't 
need to specify the actual min/max values of the pixels for the image 
itself.

Other applications may treat them as a form of black-point and 
white-point so that viewing applications can feel free to clip values 
outside of that range.

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

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