[cairo] Spot colors (and CMYK)

[Francois Robert]

Kai-Uwe Behrmann wrote :
[...]
> 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.

Just a side note: In PDF, the blending space is _explicitely specified_
(see section 7 on transparency), and it can be any flavor or gray, RGB
or CMYK (but not L*a*b*). Not sure if it is something that Cairo must
care about ?