[cairo] Spot colors (and CMYK)

[Bill Spitzak]

Kai-Uwe Behrmann wrote:

> What the colour management thread here is about to propose a clearly 
> useable API, which integrates well with the style of typical unaltered 
> input used for cairo for different output. If I have to sort every input 
> for the appropriate backend, then possibly more dedicated libraries are 
> better useable.

I'm talking about spot colors, such as "metallic gold" which CANNOT be 
represented by any RGB or LAB or XYZ triplet. Perhaps I have the terms 
wrong, but that is what "spot color" means to me. The user is saying 
"USE THIS EXACT INK THAT MY PRINTER CAN PRINT".

There is also "device independent color" which can be an XYZ triplet 
plus viewing conditions, or some other space with a defined or attached 
color profile.

What I am proposing is that a "spot color" have attached to it a "device 
independent color", but there is NOTHING in Cairo to force these to 
somehow match. It is the application's responsibility to choose a device 
independent color that resembles the spot color. As far as I can tell 
you are proposing that Cairo know about every single manufactured ink 
(or other "spot color" such as 6-channel display primaries and CMYK) so 
that it can choose a display equivalent. That sounds insane to me.