2011.03.22 03:29 "Re: [Tiff] Lab based colormaps", by Bob Friesenhahn

If I use libtiff to read the colormap it gives me three arrays, each 256 elements long, just as would happen for an RGB colour map. If I try to interpret these as the L, a, and b arrays, I get crazy colours. If, however, I reorder the data as if the TIFF file contains the colour table in the order L[0], a[0], b[0], L[1], a[1], b[1], etc. the resulting image looks OK. I can't see in the TIFF spec, or the extension specs, where the order of Lab colormap data is defined. However, it would seem bizarre if it is not in the same order as RGB data.

Has anyone had similar experiences? The test files are supposed to have been used for interworking tests with several FAX makers, so I would have expected anything as blatantly wrong as this to have been caught and fixed.

What does 'tiffinfo' say for one of these files? Are these files available for download from somewhere?

Bob
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Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/