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March 2004
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2004.03.03 19:59 "Re: Reading caspian.tif", by Chris Cox
At 4:17 PM -0500 3/2/04, Simon Granger wrote: > Hello, > > I downloaded the TIFF test images at > ftp://ftp.remotesensing.org/pub/libtiff/pics-3.6.1.tar.gz , loaded > caspian.tif with my own code using libtiff and saw the following > problem: > > The samples in caspian.tif are double-precision IEEE floating point > with no SMINSAMPLEVALUE and SMAXSAMPLEVALUE tags. So when I read the > samples, I'm expecting that they'll be in the range [0.0, 1.0]. But > they're not: the actual range of all the samples in caspian.tif is > [9.0, 946.0]. > > I would like to know if there's a standard way to process images > like caspian.tif. Well, if caspian.tif is in the set of test images, > I guess there must be a standard way to read it. I searched the TIFF > 6.0 specs but found no hint about what to do in this particular case. Yes - you process it like any HDR image and use a toning algorithm to bring the values into a "normal" range for viewing. There is nothing in the TIFF spec. regarding this sort of case (or any HDR). Chris