[cairo] [RFC] Color space API (partial proposal)

Chris Murphy lists at colorremedies.com
Wed Mar 3 13:21:40 PST 2010

On Feb 28, 2010, at 8:24 PM, Bill Spitzak wrote:

> Kai-Uwe Behrmann wrote:
>> Again I do not think than ICC colour spaces have some configuration of blending. The user app has to select a blending space, convert each colour to that and then do the blending and store the result in the surface. So I would tent to 1) with the irritation that I miss the term blending space. But perhaps you mean destination space there as blending space.
> It sounds like it works like I was assuming and hoping. The "blending space" is "a space whereby the numbers are linearly added to combine colors". Ie all the magic is done in the conversion to this blending space, not in the space itself.

I'm not sure if this stuff is documented in the PDF spec, but Adobe has documented their blending modes, many (most?) of which don't have linear function. The way multispace PDF works, objects need to be normalized to a specific color space prior to blending. Conceptually this what Kai-Uwe is referring to. This blending space is simply used as the space all objects must be in, prior to blending, otherwise the blending algorithm will be misapplied to one (or more) objects leading to improper results.

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

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