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Re: [css-color] Add HCL (aka Lch) color scheme

From: Chris Lilley <chris@w3.org>
Date: Wed, 22 Jul 2015 11:56:51 +0200
Message-ID: <1255982932.20150722115651@w3.org>
To: "Tab Atkins Jr." <jackalmage@gmail.com>, Nikita Vasilyev <me@elv1s.ru>
CC: www-style list <www-style@w3.org>
Hello Tab,

Monday, July 13, 2015, 10:16:51 PM, you wrote:

> Amusingly, Mike Bostock has another page describing the HCL rainbow as
> "ugly" <http://bl.ocks.org/mbostock/310c99e53880faec2434> ^_^

Not really seeing the relevance of that to this issue, which is about
adding LCH (and of course Lab) to css4 color. LCH(ab) is simply the
polar form of Lab:

C = sqrt(a^2 + b^2)
H = atan2(b, a)

Frankly the main obstacle to my putting these in CSS color 4 - which I
intend to do - is what would be a good syntactic form, how to do
fallback, etc. SVG had these already, with an sRGB fallback. It was
dropped from SVG2 because they would be better in CSS so they could be
used for HTML/CSS as well.

Having got such a space, *one* of the things one can then do with it
is produce an even-perceptual-spacing color scale for scientific
visualisation. Note the scientific - the point there is to avoid
hiding or exaggerating small changes in the underlying visualized
values.

"Prettiness" is a non-goal in that situation - and if desired, with
bright saturated non-evenly-spaced colors, its easy to do in RGB or
HSL.

> I am currently (slowly) working on turning the CubeHelix rainbow into
> something usable as a CSS color system.  It's intended to be the basis
> of a new named color system, but it should be useful as an HCL-like
> system as well, that's hopefully a bit more attractive.

You would need to demonstrate perceptual uniformity for it to be
useful as an LCH-like or Lab-like system.


-- 
Best regards,
 Chris  Lilley
 Technical Director, W3C Interaction Domain
Received on Wednesday, 22 July 2015 09:56:57 UTC

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