W3C home > Mailing lists > Public > www-style@w3.org > December 2013

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

From: Rik Cabanier <cabanier@gmail.com>
Date: Sat, 7 Dec 2013 09:03:40 -0800
Message-ID: <CAGN7qDCYMw3rqp9C4HMFZ=ruzV9aSTwQwAZZqs0Anm8G4N8reQ@mail.gmail.com>
To: Zack Weinberg <zackw@panix.com>
Cc: "Tab Atkins Jr." <jackalmage@gmail.com>, www-style list <www-style@w3.org>
On Sat, Dec 7, 2013 at 6:47 AM, Zack Weinberg <zackw@panix.com> wrote:

> On Sat, Dec 7, 2013 at 1:22 AM, Tab Atkins Jr. <jackalmage@gmail.com>
> wrote:
> > On Sat, Dec 7, 2013 at 4:39 PM, Rik Cabanier <cabanier@gmail.com> wrote:
> >>
> >> So, should [a tagged image] go directly to the monitor profile, or use
> sRGB as an
> >> in-between? It makes a big difference.
> >
> > Sorry, my answer had a parallel structure to your question, so I
> > assumed it was clear.
> >
> > The colors should be sRGB internally, until the last moment when
> > they're sent to the display.
> >
> > Trying to store colors in a monitor profile before that is just
> > terrible, as it means you have to do tricky things when a window moves
> > between monitors (or crosses them!).
> >
> > It also means that things that can examine the colors, like a <canvas>
> > with an image painted into it, see a weird result, which is also a
> > pretty major entropy link for fingerprinting purposes.
> If everything is mapped through sRGB internally, doesn't that mean
> wide-gamut images will be compressed to the sRGB space even when the
> monitor profile would accommodate them?  That seems unlikely to be
> what authors of wide-gamut content would want (consider high-end
> photographic galleries, for instance).
> It would seem more appropriate to me to store images in the *image*
> color space until the last moment and then map them directly to the
> display space.

That is one way of doing it. However, then you as an author would not be
able to tell what the image is going to look like. It would look dull on an
sRGB device but bright on a high quality device or a 5 color printer.

If you want to display a web page in a higher gamut, the right way to do so
is to change the device profile from sRGB to one that has the higher gamut.
If you then display this on an sRGB device, the colors will become dull
again but since the mapping is perceptual, the general impression of the
page colors will stay the same.

(For <canvas>, at least right now, mapping to sRGB upon pixel readback
> does seem like the Right Thing, but down the road we may want a way to
> establish a different working space...)

I don't think you want to do that. Canvas pixels should be in the device
color space so there's no mapping on reading or writing.
Received on Saturday, 7 December 2013 17:04:08 UTC

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