2004.03.03 19:59 "Re: [Tiff] Reading caspian.tif", by Chris Cox
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).