[cairo] Spot colors (and CMYK)

Chris Murphy lists at colorremedies.com
Tue Feb 23 11:33:32 PST 2010

On Feb 23, 2010, at 12:03 PM, Bill Spitzak wrote:

> 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 aren't many such spot colors. There are many more common spot colors that can be defined as LAB just fine and displayed well.

> 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.

Yes, fine.

> 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.'

Yes, that would be insane. I haven't gotten the impression anyone is proposing it.

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

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