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October 2000

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2000.10.01 15:43 "Gamma Correction for LogLuv Format, why?", by Stefan Maass

hi all,

there is a gammacorrection in the XYZ->RGB conversation when reading a
tifflogluv file and asking for RGB values (file tif_luv.c). What
is the reason for that? I could't find a gammacorrection in the writing
case.

I have a second question about the LogLuv format:
Converting from XYZ -> RGB (file tif_luv.c) the used transformation matrix
is the same as in the article from Greg Ward Larson: "LogLuv Encoding for
Full-Gammut, High-Dynamic Range Images" (journal of graphics tools, Vol3,
Nr.1) But the maticies XYZ->RGB and RGB->XYZ are not fully inverse each to
another. So if a have a rgb-image as as result of global illumination
computation, and writing it as a Tiff-LogLuv file with the proposed
RGB->XYZ matrix and open it again with libtiff, i will make a little
error. Is this true?

Many Thanks in advance

Stefan Maass