[cairo] Spot colors (and CMYK)

[Bill Spitzak]

Chris Murphy wrote:
>> re: color profiles convert to 3D
>
> True for device class profiles, i.e. display device, input device, output device (there are commonalities, but these are different profile classes).
> 
> There is yet another profile class that can be used to preserve aspects of 4D color spaces (or more channels even). That is the DeviceLink class. It does not make use of a PCS, so there isn't, in effect, a conversion to LAB or XYZ. So such profiles can be built to do things like preserving 100%K only (e.g. for black text).

However this sounds like the proposed "spot color" api. Ie "use exactly 
this ink on the output device, and here is a portable simulation in case 
you are not the specific output device".