[cairo] Spot colors (and CMYK)

[Jon Cruz]

On Jan 21, 2010, at 6:59 PM, Bill Spitzak wrote:

> The only real reason I could see is that CMYK is 4-dimensional, thus  
> it cannot be converted to sRGB which only has 3 dimensions. However  
> from the descriptions here this is not considered a problem by color  
> management, since there are repeated claims that XYZ is acceptable  
> (other than spot colors which are really an N-dimensional space). But  
> none of the color management experts here have mentioned the only  
> mathematically sound argument, so I think it actually is not a problem.

But in use those are not really just n-dimensional problems.

One of the more common uses for CMYK tweaking is to get text and sharp areas of an image to pure K only, and to leave black areas of images that are fin to be left as mixtures of more inks.

Other times, a nice mix of roughly 40% cyan and 100% black will get the final result the artist wants from the print house via "rich black". Trapping also comes in to be a major factor for a graphic designer trying to get proper print output. Trapping control, "cool black", "warm black" and other such concerns are major reasons explicit CMYK input might be needed.

Of course, if one were to say "Cairo need never output results suitable for professional printing", then it could probably be cut. Removing PDF output might be a good way to achieve that.