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Re: [CSS4 color][CSS4 transition] color pre-multiplied vs non pre-multiplied was (Re: [CSSWG] Minutes TPAC Tue 2012-10-30 AM I: Abstract Directions, Transforms, Transitions)

From: Simon Sapin <simon.sapin@kozea.fr>
Date: Fri, 01 Feb 2013 17:42:19 +0100
Message-ID: <510BF06B.4020004@kozea.fr>
To: Rik Cabanier <cabanier@gmail.com>
CC: Brad Kemper <brad.kemper@gmail.com>, Simon Fraser <smfr@me.com>, Alan Gresley <alan@css-class.com>, fantasai <fantasai.lists@inkedblade.net>, "www-style@w3.org" <www-style@w3.org>
Le 01/02/2013 17:34, Rik Cabanier a écrit :
>
>
> On Fri, Feb 1, 2013 at 6:50 AM, Brad Kemper <brad.kemper@gmail.com
> <mailto:brad.kemper@gmail.com>> wrote:
>
>     On Jan 31, 2013, at 11:18 PM, Simon Fraser <smfr@me.com
>     <mailto:smfr@me.com>> wrote:
>
>      > We rely on Core Graphics to render gradients on Mac, and that
>     can't do pre-multiplied. That's the main reason why gradients don't
>     match transitions.
>
>     If I understand correctly, this means that if an author wants a nice
>     clean-looking 3-stop gradient that goes from yellow to transparent
>     to blue, he will have to use two same-position transparent color
>     stops, so that it is actually yellow to transparent-yellow, and then
>     transparent-blue to blue. Couldn't WebKit just perform this extra
>     conversion step for us before passing it on to Core Graphics?
>
>
> This is why I would do under the hood.

Is this equivalent to pre-multiplied with transparent being always 
rgba(0,0,0,0)?

-- 
Simon Sapin
Received on Friday, 1 February 2013 16:42:46 GMT

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