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April 2008
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2008.04.16 23:13 "Re: Floating Point Tiff Format?", by Frank Warmerdam
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