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Proposed 'color-correction' property

From: L. David Baron <dbaron@dbaron.org>
Date: Thu, 12 Nov 2009 15:41:53 -0800
To: www-style@w3.org
Message-ID: <20091112234153.GA16880@pickering.dbaron.org>
At the working group's face-to-face meeting last week, we discussed
the issue that existing implementations do not conform to the
statement in CSS1, CSS 2.1, and css3-color that colors specified in
CSS should be presumed to be in the sRGB color space. [1]

It would be good for implementations to progress towards following
that part of the specification.  However, implementations are
currently blocked from doing that due to issues related to plugins.

We have to worry about two issues:
 * consistency of the relationship between colors
   on a single computer (most importantly, on a single page)
 * consistency of the colors on a page between computers
And we'd like a way to improve the second without hurting the first.

Therefore, we agreed to add a property that would allow authors to
opt in to what has previously been defined as the correct behavior.
(Simultaneously, I hope that we can get the plugin situation to
improve so that browsers can always do the correct behavior.)

A proposal for this property follows; this differs a little bit from
what we agreed on in terms of the definition of the 'auto' value
(providing stronger conformance criteria), based on discussions I
had later in the week.

I wrote this pretty quickly and I'm sure it needs more work, but I'd
like to start getting feedback on this proposal.


Name: color-correction
Value: auto | sRGB
Initial: auto
Applies to: all elements
Inherited: yes
Percentages: N/A
Media: visual
Computed value: as specified

The color-correction property specifies the color space that colors
specified in CSS and colors in images whose color space is undefined
according to the rules for the relevant image format (<dfn>untagged
images</dfn>) are in.  It does not apply to videos, since untagged
video should be presumed to be in CCIR 601.

sRGB
  Colors specified in CSS and colors in untagged images are in the
  sRGB color space, and must be displayed accordingly.

auto
  The color space for colors specified in CSS and colors in untagged
  images is not defined.  However, implementations must use a single
  color space for such colors so that they match each other.  When
  doing so would not cause color mismatches with content such as
  plugins, implementations should treat 'auto' the same as 'sRGB'.

-David

[1] http://www.w3.org/2009/11/03-CSS-irc.html#T19-35-25

-- 
L. David Baron                                 http://dbaron.org/
Mozilla Corporation                       http://www.mozilla.com/
Received on Thursday, 12 November 2009 23:42:21 GMT

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