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: cbunks@xxxxxxx ------------------------------------
