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May 2005
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2005.05.30 10:31 "Re: Jpeg and YCbCr", by Marti Maria
Hi, > Have someone seen a ICC profile, a EXIF object, a BROUZOUF object, > make something else than adding ambiguity ? > ( Don't say waste CPU cycles and RAID cylinders, I know ) > :-))) ICC profiles, many times. Of course if you embed the wrong profile, then it is going to mess out your image, but used properly works quite well. > > is probably by using the L* component of L*a*b*. > > If we were to say that Photometric=YCbCr and SamplesPerPixel=1 is not legit... I > > don't think we have a legit way to store L* rasters, either. > > > > That may be a to pragmatic argument to be convincing, but I would like to add to > > that, again, that Photometric=YCbCr and SamplesPerPixel=1, or > > Photometric=whateverLab and SamplesPerPixel=1 is really unambigious. YCbCr is a device space, Lab is a colorimetric space. You can use YCbCr based on Rec.601 or Rec. 709, to enumerate a few. But there is only one Lab. Well, you can argue Lab depends of white point, but this is another story. Photometric=Lab and Samples per pixel=1 is legal as it is documented in the TIFF Technote #2 (March 22, 2002), see page 13: SamplesPerPixel - ExtraSamples: 3 for L*a*b*, 1 implies L* only, for monochrome data. Regards, Marti Maria.