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Re: [css3-images] A specified algorithm for premultiplied gradients

From: Leif Arne Storset <lstorset@opera.com>
Date: Tue, 07 Dec 2010 14:58:04 +0100
To: "Tab Atkins Jr." <jackalmage@gmail.com>
Cc: "www-style@w3.org" <www-style@w3.org>, Fredrik Söderquist <fs@opera.com>
Message-ID: <op.vncjq2njtmo5g6@nynorsk>
Tab Atkins Jr. <jackalmage@gmail.com> skreiv Tue, 07 Dec 2010 14:51:01  

> On Tue, Dec 7, 2010 at 5:42 AM, Leif Arne Storset <lstorset@opera.com>  
> wrote:
>> The color stop section [0] of the gradients spec currently reads:
>>> Between two color-stops, the line's color is linearly interpolated  
>>> between
>>> the colors of the two color-stops, with the interpolation taking place  
>>> in
>>> premultiplied RGBA space.
>> Our graphics people have requested that a specific algorithm be  
>> specified
>> for this interpolation.
>> 0. http://dev.w3.org/csswg/css3-images/#color-stop-syntax

> Sure.  Would something like this be sufficient?
> """
> To transition colors in premultiplied space, first convert each color
> to rgba() notation.  Then, convert each to a 4-tuple where the first
> three elements are the red, green, and blue components multiplied by
> the alpha, and the fourth element is the alpha.  Then, linearly
> interpolate the respective components of these 4-tuples.  At each
> point, the color expressed in the 4-tuple can be extracted back into
> rgba() format by dividing the first three components by the alpha to
> regain the red, green, and blue component.
> """

Turns out I misunderstood the graphics people, and we don't really need  
this. Personally, though, I wouldn't object to it being specified, so keep  
it if you like.

Leif Arne Storset
Core Technology Developer, Opera Software
Oslo, Norway
Received on Tuesday, 7 December 2010 13:58:50 UTC

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