[cairo] Spot colors (and CMYK)

[Bill Spitzak]

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.

So you are saying that ALL cairo back ends must know how to blend CMYK 
and must know how to convert their color information to CMYK just in 
case the program sends a partially-transparent CMYK image?

That is insane!

I recommend that ALL blending be done in "device space" with the caveat 
that "device space" must somewhat resemble sRGB in gamma response. The 
only guarantees with spot colors (including CMYK) is that if the image 
is 100% opaque and does not have any antialiased pixels that you get 
exactly the spot color you specified.