[cairo] colour management

Carl Worth cworth at cworth.org
Wed Mar 5 14:38:43 PST 2008

On Wed, 5 Mar 2008 20:28:11 +0100, "Aubanel MONNIER" wrote:
> Just to let you know you cairo developers that I setup an inkscape "Blue
> print" about color management.
> https://blueprints.launchpad.net/inkscape/+spec/icc-for-cairo
> It tries to precise use cases and proposes a draft API for cairo. I hope it
> helps to get this supported quicker.
> It's a wiki, so feel free to discuss/edit.

Hello there!

Thanks so much for sharing this with us.

I'd definitely love to see cairo pick up the necessary functionality
so that it can generate PDF suitable for pre-press needs.

You mentioned elsewhere in this thread that you would expect to see
cairo grow a dependence on littleCMS. Personally, that sounds like
exactly the right thing to me. Color management should be a problem
that is handled well by a separate tool rather than something that
cairo should try to grow and take over on its own.

As for platforms that have "native" color management systems, can
littleCMS sit on top of them already or be made to do so?

So the first thing I'm surprised by is that the API proposal so far
isn't using littleCMS types in the interfaces. Shouldn't things like a
color profile just be created with existing littleCMS APIs and then
passed to cairo?

Oh, and if I haven't made it perfectly clear already, I'm a total
idiot when it comes to color. In the API proposal so far I see three
separate notions being proposed to cairo:

	color intent

	color profile

	color profile mapping

Can you explain (or provide a reference for me) for what the three
notions are? In particular, this function confuses me considerably:

cairo_surface_add_profile_mapping(cairo_surface_t *surf,
                                  cairo_color_profile_t *in,
                                  cairo_color_profile_t *out);

What in the world does that mean? What is the user asking cairo to do
by calling that?

And is "color intent" fundamentally separate from "color profile"?
That is, is there a reason we couldn't simplify this API down to one
new concept being added to cairo (a color profile) and then preferably
just use a littleCMS datatype to express it?

Again, thanks in advance for your patience with this color idiot.

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