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April 2010
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2010.04.26 20:59 "Re: Bug in tif_print.c for TIFFTAG_REFERENCEBLACKWHITE", by Olivier Paquet
On Mon, Apr 26, 2010 at 4:12 PM, Edward Lam <edward@sidefx.com> wrote: > Edward Lam wrote: > > I have an 6-Bit RGBA image and using tiffinfo on it gives: > > Er, I meant 8-bit here of course. > > I also noticed another problem with the number of expected floats for > TIFFTAG_REFERENCEBLACKWHITE in the documentation for TIFFSetField: > http://libtiff.maptools.org/man/TIFFSetField.3tiff.html > where it says: > 2*SamplesPerPixel That's also what the TIFF spec says in appendix A. Of course, other mentions of the tag specify 6 float. The spec also says: The ordering of pairs is the same as those for pixel components of the PhotometricInterpretation type. ReferenceBlackWhite can be applied to images with a PhotometricInterpretation value of RGB or YCbCr. ReferenceBlackWhite is not used with other PhotometricInterpretation values. Which implies the tag will only ever have 6 values as both RGB and YCbCr have 3 components. libtiff always reads/writes 6 floats so it is definitely wrong to try to display 8 values. Are there any objections to hardcoding the output of 6 values? Olivier