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Re: [css-color] Safari 7 is color-managing CSS colors?

From: Rik Cabanier <cabanier@gmail.com>
Date: Fri, 6 Dec 2013 21:39:17 -0800
Message-ID: <CAGN7qDB4m93gpcZosfiD_Q0Zcj800wK1yL-Lg-CDEvgvdvBfXQ@mail.gmail.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
Cc: Dean Jackson <dino@apple.com>, Chris Lilley <chris@w3.org>, www-style list <www-style@w3.org>
On Fri, Dec 6, 2013 at 9:07 PM, Tab Atkins Jr. <jackalmage@gmail.com> wrote:

> On Sat, Dec 7, 2013 at 3:31 PM, Rik Cabanier <cabanier@gmail.com> wrote:
> > Can you tell me where the color workflow is defined?
> > For instance, it is defined that all CSS colors should be tagged with an
> > sRGB profile. Image can optionally have a tag as well.
>
> Not quite.  It's currently allowed for CSS colors to be unmanaged, if
> untagged images are also unmanaged, and so they just get blasted into
> the monitor's gamut without adjustment.  It's just tagged images that
> have to be managed right now.
>
> > How are those colors actually mapped when going to screen?
> > I believe that in the case of Core Graphics, everything is drawn into a
> sRGB
> > device which is then mapped to the output device.
> > So, a tagged imaged would go: Image profile -> sRGB -> monitor profile.
> > Assuming that the output device is properly calibrated, you would get the
> > same colors everywhere.
> >
> > Is this how it's supposed to work? Or is a tagged image supposed to go to
> > the monitor profile directly?
>
> That's how it's supposed to work, yes.  Anything else is really bad,
> because it means you're leaking color profiles all over intermediate
> stages.
>

So, should it go directly to the monitor profile, or use sRGB as an
in-between?
It makes a big difference.


>
> Colors should be treated like Unicode is.  Good hygiene means
> converting bytes to codepoints as soon as they enter the system, and
> not turning them back into bytes until they leave.  Same with colors -
> bytes should be turned into a managed colorspace as soon as they
> enter, and not turned into monitor profile until they leave the
> system.
>

Yes, colors should always be tagged. They don't really become 'monitor
profiles' though; that happens (or should happen) to the intermediate
bitmap/displaylist.


>
> > Can you specify the rendering intent anywhere?
>
> I don't think there's a need to?
>

Maybe not, but you need to define it somewhere if there's mapping between
colorspaces. Perceptual is probably a reasonable default.
Received on Saturday, 7 December 2013 05:39:45 UTC

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