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Re: [css3-images] Premultiplication switch (was: gradient pre-multiplied interpolation)

From: Chris Lilley <chris@w3.org>
Date: Wed, 27 Jul 2011 19:16:53 +0200
Message-ID: <1108471817.20110727191653@w3.org>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
CC: Leif Arne Storset <lstorset@opera.com>, "www-style@w3.org" <www-style@w3.org>
On Wednesday, July 27, 2011, 6:03:52 PM, Tab wrote:

TAJ> On Wed, Jul 27, 2011 at 5:37 AM, Leif Arne Storset <lstorset@opera.com> wrote:
>> I agree with Alan that the effects demonstrated at [0] are desirable, but
>> premultiplied is a much better default. The switching idea is worth
>> considering, however. I think use of the rgba() and hsla() are potentially
>> confusing as switches, but an explicit 'unpremultiplied' switch wouldn't
>> be: 'linear-gradient(left, unpremultiplied, rgba(255,255,0,0), yellow)'.

TAJ> I believe a better approach would be to augment SVG's
TAJ> color-interpolation property with options for switching between
TAJ> premultiplied and non-premultiplied.  That way other things could
TAJ> potentially switch as well, like transitions.

I agree that is a better approach. Currently the color-interpolation property selects between colour spaces. It would be possible to add a premultipliedRGB value. Note that conversion into a premultiplied colourspace does result in loss of colour precision as the opicity decreases.




-- 
 Chris Lilley   Technical Director, Interaction Domain                 
 W3C Graphics Activity Lead, Fonts Activity Lead
 Co-Chair, W3C Hypertext CG
 Member, CSS, WebFonts, SVG Working Groups
Received on Wednesday, 27 July 2011 17:17:05 GMT

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