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Date: Wed, 16 Apr 2008 19:13:52 -0400
From: Frank Warmerdam <warmerdam@pobox.com>
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To: Fred Weinhaus <fmw@alink.net>
Subject: Re: [Tiff] Floating Point Tiff Format?
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Status:   

Fred Weinhaus wrote:
> Hello,
> 
> I am new to this list.
> 
> I was wondering if libtiff supports floating point format tiff?  I am 
> interested in both floating point grayscale images and floating point 
> RGB images?
> 
> If there is support for this, how does one go about enabling it - does 
> anything special need to be done in the configure/build for libtiff?
> 
> Is there some documentation for the floating point format and if so 
> where might I find that. I see nothing about floating point format in 
> the TIFF 6.0 Specs.
> 
> I also saw an old post about the potential for a complex (real and 
> imaginary) tiff format? Did anything come from that.
> 
> My questions relate to the use of a floating point or complex format for 
> generating FFT of images using the FFTW package and storing the results 
> in a relevant TIFF format.

Fred,

libtiff supports floating point files by default; however, I don't think
it includes any default visual interpretation of floating point images.
So the "read as RGBA" interfaces likely fail for floating point images.

In any event, I use libtiff often to read and write floating point tiff
files without any problems.  This is via the TIFFReadEncodedStrip/Tile
functions.

There is also support in libtiff for reading and writing complex floating
point values, but this is ideosyncratic to libtiff, and not part of the
TIFF specification.  I extended libtiff with the sample formats:

#define	    SAMPLEFORMAT_COMPLEXINT	5	/* !complex signed int */
#define	    SAMPLEFORMAT_COMPLEXIEEEFP	6	/* !complex ieee floating */

To the best of my knowledge there are few applications that support these
types, though my GDAL library does.

Best regards,
-- 
---------------------------------------+--------------------------------------
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    | President OSGeo, http://osgeo.org

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