[cairo] Spot colors (and CMYK)

[Chris Murphy]

On Feb 20, 2010, at 4:19 AM, ecir hana wrote:
> 
> What do you mean by "current cairo colour toy API"?
> "cairo_set_source_rgb()"? That doesn't handle CMYK and spots. Are you
> saying that in order to use CMYK I have to use CMS and have the needed
> profiles? Because that's something I don't really like because
> sometimes I just know that the text should be CMYK(0, 0, 0, 100) or
> that I want to use exactly 100% of this Pantone - I shouldn't be
> required to have a profile for it.

Both RGB and CMYK and spot values are meaningless without being tagged. You may specify CMYK values directly, rather than needing a CMS to produce them, however those CMYK values should be tagged with a profile so that their color meaning is usable downstream: for display, for proofing, and for preflight purposes to confirm the proper printing conditions are applied.

Metadata describing "black text" rather than "this generic object is C0M0Y0K100" is superior. Because how black text should be handled is different depending on the output process. For a printing press, it would need to be 100K only. But for a billboard, you'd print rich black because 100K is often a dark gray, and its perfect register makes rich black text feasible. Leaving devicedependent data floating around in the world is a pretty bad idea. Even for printing to known destinations, the PDF/X-1a model should be chosen, which is to tag all CMYK content.


Chris Murphy
Color Remedies (TM)
New York, NY
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Co-author "Real World Color Management, 2nd Ed"