[cairo] Subtractive API, part 0

[Chris Murphy]

On Feb 3, 2010, at 2:27 AM, Christoph Lindemann wrote:

> Hi,
> 
> I have not contributed to cairo yet, but have read this thread with much
> interest.
> The following might read dumb or silly, as I am not very familiar with
> color spaces, CMS and the lot. But I will try to come with my ideas and
> questions, at least so that I could understand the problem area better.
> 
> --------------------------------------------------------
> 1) Could not the color profile conversion stuff (CMS) simply be provided
> by the surface implementation?
> Then the surface knows best how to handle the color profiles. 
> -The GDI surface for instance, could use the Windows CMS. 
> -The PDF surface, could just embed the profiles into the PDF stream,
> then the PDF consumer would do the actual CMS. If it is a printer, the
> RIP would be responsible, or the print operator could tweak/change the
> profiles in his workflow.
> -Other surfaces could do the same.

Seems reasonable.


> 
> --------------------------------------------------------
> 2) Can spot colors and similar be expressed in RGB with attached color
> profile?
> I was thinking, that you could handle (in the code) all color in cairo
> with RGB (or whatever is used right now) and for the color handling be
> able to attach a color profile.
> So the inner workings and API of cairo would not need to be changed, but
> would be backwards compatible.

The RGB color space would need a large enough color gamut in order to contain the spot colors. 

> 
> --------------------------------------------------------
> 3) You could at some API, so you could add an input color profile, and
> select an input profile. After you select a profile, the following
> drawing operations would uses that profile:

Technically that would be source profile. Input profile is short for "input device class" profile which is a profile for scanners and digital cameras.


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