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Date: Wed, 17 Jan 2007 10:08:14 -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:
>
> It makes sense for floating point grayscale data, or any data under that
> Photometric tag, to assume the range of 0.0 to 1.0, simply because there
> is no other intrinsic range on this. For example, 0.0 to 255.0, makes no
> sense, unless there is something intrinsic in the concept of grayscale
> that binds it to 8 bit ranges in particular. Amongst the few testfiles I

It seems that the 0.0 to 1.0 range is "popular".  A 0 to 100 range 
seems just as useful.  Other ranges may make better use of the 
floating point values and avoid unnecessary quantization.

When original values are obtained from physical sensors (natural 
integer producers) and stored as floating point, it may make sense to 
use a floating point range which matches the sensor's range since 
doing so avoids any possiblity of quantization error due to storage.

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

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