[cairo] Spot colors (and CMYK)

Kai-Uwe Behrmann ku.b at gmx.de
Thu Feb 18 08:52:03 PST 2010

Am 18.02.10, 17:08 +0100 schrieb ecir hana:
> On Thu, Feb 18, 2010 at 8:36 AM, Kai-Uwe Behrmann <ku.b at gmx.de> wrote:
>> Yes, it is needed. But not directly by blending RGB over Cmyk. I would not
>> know how to directly do this.
>> The app must decide, which space is prefered for blending and then after
>> colour conversion of on element the blending can be done in one common color
>> space.
> Can't you use the space of destination surface per default? That way
> there would be no need of setting the blending space.

The editing and blending space is a typical user setting througout a 
decided upon colour workflow. So I would honour that decission and use 

>> I would choose Cmyk as blending space and convert Rgb to that and put all
>> the resulting Cmyk with the ICC profile into PDF.
>> For screen simulation Cmyk would have to be converted to monitor RGB.
> So if I want to draw CMYK image over RGB surface, I should first
> convert the surface to the space of image, blend, and then convert the
> whole result back to RGB. Right? (I really like the idea of blending
> in CMYK, btw.)

This all highly depends on what the concrete user prefers as editing space 
or the special application. But for editing in Cmyk and displaying on 
monitor I would guess you are right.

kind regards
Kai-Uwe Behrmann
developing for colour management 
www.behrmann.name + www.oyranos.org

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