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Re: [css3-images] Proposed Gradients changes

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Tue, 23 Nov 2010 11:06:03 -0800
Message-ID: <AANLkTi=-v4vb+ru0YbdMKJ0Bs782bvNXaWeYXVrGUFRm@mail.gmail.com>
To: Anne van Kesteren <annevk@opera.com>
Cc: Brad Kemper <brad.kemper@gmail.com>, www-style list <www-style@w3.org>
On Tue, Nov 23, 2010 at 8:08 AM, Anne van Kesteren <annevk@opera.com> wrote:
> On Tue, 23 Nov 2010 16:58:06 +0100, Anne van Kesteren <annevk@opera.com>
> wrote:
>> Sorry, I meant whether colors are premultiplied or not. (For some reason I
>> thought it was about interpolation.) It's not a syntax issue, but a model
>> issue. And I would very much like the model to be shared with SVG/<canvas>
>> so we do not need multiple codepaths.
>
> Apparently we already went through the trouble to make this work and are
> happy with it. Sorry about that!

I'm explicitly matching the behavior of Transitions, based on feedback
from Simon.  This also matches SVG by default, because SVG doesn't
composite alpha with their colors - they track and transition color
and opacity independently, so they don't have to worry about the issue
(going from yellow to transparent in premultiplied colors is basically
equivalent to going from yellow;opacity:1 to yellow;opacity:0 in SVG,
modulo possibly some precision loss in the CSS colors).

It looks like <canvas> is specifying non-premultiplied for its
gradients, though.  Hm.  I suspect we could change this if we got some
implementor agreement.  Right now it's the odd-man-out on the
platform, and that's unfortunate.

~TJ
Received on Tuesday, 23 November 2010 19:07:01 GMT

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