Re: [css-gcpm][css-color] device-cmyk() interaction with RGB-space colors.

On Tue, Sep 24, 2013 at 2:58 PM, Tab Atkins Jr. <jackalmage@gmail.com>wrote:

> On Tue, Sep 24, 2013 at 2:31 PM, Rik Cabanier <cabanier@gmail.com> wrote:
> > The compositing/blending spec doesn't talk about converting colors [1]
> All
> > the formulas (except for 4 special ones) work on individual color
> channels,
> > regardless of what they represent.
>
> Those channels appear to be assumed to be RGB.


Can you point out where that is so I can update the spec?


> If it's compatible
> with CMYK, cool, but that needs to be specified (and again, needs to
> be defined how you blend/composite between RGB and CMYK).
>
> I doubt that this "just use the channels" approach is compatible with
> some other color spaces, like Lab, though.
>

It is compatible. You can try it in PhotoShop :-)


>
> > I agree we need to define a way how and when individual elements are
> > converted to the document's color space.
>
> Sure, something more advanced than just "always convert to RGB
> immediately" might be worthwhile.  We talked about this at the f2f,
> though, and some of the ideas (like converting individual pixels to
> RGB as necessary, or converting entire elements to RGB as soon as you
> need to convert some part of it) were all horrible and not worth the
> benefit, so I didn't put those ideas into the spec.


It seems we could define something simple. People have a tendency to
overcomplicate color management...