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RGB to CMYK

• To: mathgroup at smc.vnet.net
• Subject: [mg25493] RGB to CMYK
• From: bernd at bio.vu.nl (Bernd Brandt)
• Date: Thu, 5 Oct 2000 23:50:13 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

Hi Group,

I am looking for a conversion function between RGB and CMYK.
I thought this would not be a problem but i have not found one good function.

The Mathematica book (examples) includes:

CMYKfromRGB[RGBColor[r_, g_, b_]] :=
CMYKColor[b, r  b, 1 - b, (r + g + b)/3]

But this is not correct. 
RGBColor[1,0,0] really red, is converted to CMYKColor[0, 0, 1, 0.5],
which is clearly not red.

Does someone have a correct function?


Regards,
Bernd