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	Thu, 22 Dec 2005 18:02:26 EST
Date: Thu, 22 Dec 2005 18:02:26 -0500 (EST)
From: David Scriven <davidwriter@yahoo.com>
Subject: Re: [Tiff] Custom Tags, Private Ifds and other questions
To: Frank Warmerdam <warmerdam@pobox.com>
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Status:   

> On 12/22/05, Chris Cox <ccox@adobe.com> wrote:
> > The other option is to register a single tag, and put multiple
> values in
> > there.
> 
> This would be my suggestion too, without knowing too much
> about what you are actually trying to save.  Private IFDs are
> a bit of a hassle to manipulate with libtiff.
> 
> Best regards,
> --
> 
When I first started using TIFFs for this application, I 
appended a long string to the Description, which 
my program could then sort out. The problem, I
found, is that unlike having a specific tag 
(eg., wavelength or filter settings) which immediately
connected you to what the value meant, you had 
a long string containing a lot of numbers
which were impossible to interpret without
the right program. This is the reason I wanted
to have specific tags. I do realise that a
private Ifd would hide values from people 
using tiffinfo, and not work when copying images,
but I can't say that the single tag is a solution 
I like, either.

If you look at TIFF images produced by various 
confocal microscopes they often contain unregistered
tags with strings of numbers whose meaning one
can only guess at. They also often generate companion
files with important information relating to the
state under which the data was collected, which, alas
often gets separated from the image.     

Having suffered in trying to interpret such data,
I didn't want to be responsible for inflicting
another such botch on the community at large.
I would have no problem in sharing the contents
of a private Ifd if this is the route I take.

  
--- Frank Warmerdam <warmerdam@pobox.com> wrote:

---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam,
> warmerdam@pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush    | Geospatial Programmer for
> Rent
> 



	

	
		
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