[cairo] Spot colors (and CMYK)

[Jon Cruz]

On Feb 16, 2010, at 9:58 AM, Bill Spitzak wrote:

> 
> 
> ecir hana wrote:
>> Hello,
>> just a quick one: what do you think should happen when you have one
>> surface in duotone (or CMYK or any other non-3D space, as Bill Spitzak
>> calls them) and you want to paint it over (copy, multiply) 3D color
>> space? In other words, what do you think, who should do the conversion
>> - Cairo or the application? But perhaps you, or someone else, see
>> another possibility?
> 
> Cairo should mix the sRGB values together using normal math. The back 
> end will have a final result of a given sRGB triplet, plus the fact that 
> a given spot color contributed to the result. It can then try to extract 
> the additive contribution of this spot color and figure out how to print 
> the given sRGB using as much of the spot color as possible.

Again, the first problem encountered here will be with overprint, etc. sRGB will lose the precise control of the black channel that artists switch to CMYK or duotone in order to control.