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[css4-color] unclamped values for RGB

From: Rik Cabanier <cabanier@gmail.com>
Date: Fri, 15 Jun 2012 21:07:26 +0200
Message-ID: <CAGN7qDAh4=SygJPu1iKhWywxUGzxOQLBWGQU-5yRJFTfQzKgRQ@mail.gmail.com>
To: www-style list <www-style@w3.org>

currently the CSS color allows color values larger than 1 and smaller than
0 (see the bottom section of
http://www.w3.org/TR/CSS21/syndata.html#value-def-color). I'm unsure if
anyone has actually implemented this.

The spec currently defines that all non-image colors are defined in sRGB
which is a simplistic profile. It's gamma correction + a simple translate
function. Clamping to [0..1] is part of the definition (see

The problem with this is:
a. This is breaking the profile math.  Are all out of gamut colors possible
or only a subsection?
b. Colors with out of gamut colors will display different than they print
c. What if we want to improve color on the web later on? sRGB used to make
sense but current displays are capable of a wider gamut (ie Super OLED)
which currently goes unused or abused to show colors that are too vibrant.
New displays will probably have table based profiles where unclamped input
makes no sense.

I think this feature should be dropped and replaced with something that is
colorimetrically correct. This could be Lab or the ability to specify what
profile the author intends to use (or both :-0)

Received on Friday, 15 June 2012 19:07:56 UTC

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