[Image-SIG] RGB to CMYK color conversion

[kevin]

I was wondering if anyone has a better matrix for converting RGB to CMYK...
the default conversion maps RGB directly to CMY, but does nothing with the
black channel, leaving images very flat.

I know you can provide a matrix to the Image.convert function, but my matrix
algebra isn't too good... q:]


>From Fred's manual:

----------------------------------------------------
Example: Convert RGB to XYZ

    rgb2xyz = (
        0.412453, 0.357580, 0.180423, 0,
        0.212671, 0.715160, 0.072169, 0,
        0.019334, 0.119193, 0.950227, 0 )
    out = im.convert("RGB", rgb2xyz)
-----------------------------------------------------


Does anyone have a suitable matrix for converting using UCR or GCR, or
something similar?  (It would make sense to implement such a matrix for the
default conversion... straight RGB->CMY conversion is not very useful)

Thanks!

Kevin Cazabon.



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