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March 2011
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2011.03.22 03:29 "Re: Lab based colormaps", by Bob Friesenhahn
On Tue, 22 Mar 2011, Steve Underwood wrote: > > 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 -- Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/