So is there anyone with such a tool, or the basic transformation rules so
that I can write my own?
Hi Uwe,
The map from RGB to CMYK is not unique because it depends on a
printing policy that specifies the percentage black that should be in
a pixel. This is often referred to as GCR (or gray componenet
replacement). It is important for a variety of reasons including how
much ink is needed to print an image (and thus the speed at with the
print will dry) the size of printable dots on a page, etc.
However, the conversion from CMYK to RGB is unique and is described by
the following formulas:
Presuming that C, M, Y, and K are expressed with values in [0,1] then:
R = 1-(C+K)
G = 1-(M+K)
B = 1-(Y+K)
If C, M, Y, and K are not in [0,1], normalize the equations so they
are.
Best regards,
Carey
PS You may want to read the discussion on CMYK given here:
http://gimp-savvy.com/BOOK/node53.html
I also recommend this section to those attending GimpCon as it
describes those features needed in the GIMP for it to become CMYK
capable. This would finally make the GIMP a viable tool for the
pre-press world.
------------------------------------
Dr. Carey Bunks
Senior Scientist
BBN Technologies
70 Fawcett St, 15/2A
Cambridge, MA 02138
tel: 617-873-3028 fax: 617-873-2918
email: [EMAIL PROTECTED]
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