[cairo] Spot colors (and CMYK)

Chris Murphy lists at colorremedies.com
Sun Jan 24 17:19:06 PST 2010

With respect to Cairo allowing applications to do soft proofing, this really requires ICC based color management. Soft porofing is a rather specific thing that also implies rather specific ambient and print viewing conditions, in addition to getting other things correct. But certainly we also need to take into account the specific CMYK source space (and optional spots), and convert those to display RGB, or we simply do not have soft proofing. A simple CMYK to RGB conversion is completely inadequate for soft proofing. So if soft proofing is a goal, something is going to need to use ICC profiles.

If Cairo is responsible for/capable of interpreting PDF, then the color management functionality belongs in Cairo. The flavors of PDF used for printing: PDF/X-1a, PDF/X-3, PDF/X-4, etc. all have an output intent specified in the PDF. By default, any application should use this output intent as the assumed source profile for any CMYK content in the PDF, or it's simply being displayed wrong.

The way Acrobat works on both platforms, by default - it always honors embedded ICC profiles in the PDF, there is no way for them to not be used. Embedded profiles are the source space for an object, and the destination profile is the display profile. Further, objects that are untagged have assumed source profiles, which is configurable.

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

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