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Re: [css4-images] non-premultiplied gradients and in the wild

From: Alan Gresley <alan@css-class.com>
Date: Thu, 30 Aug 2012 00:07:43 +1000
Message-ID: <503E222F.3090401@css-class.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
CC: www-style list <www-style@w3.org>
On 9/08/2012 6:53 PM, Alan Gresley wrote:
> On 7/08/2012 10:02 AM, Tab Atkins Jr. wrote:
>> Heya, I've finished up the first draft of Image Values level 4
>> <http://dev.w3.org/csswg/css4-images>, incorporating several of the
>> features we punted from level 3 and a few new ones.  I'd greatly
>> appreciate feedback on the changes so we can potentially do a FPWD
>> after the f2f.

Am I going to get a response to the message?

With every single reason why non-premultiplied gradients were rejected, 
I was able to show how it could be done with slightly different syntax.

To have a gradient from 'transparent' to 'yellow' and have the midway 
point as ##FFFF79 (light yellow), all an author needs to do is use 
transparent-yellow to yellow.

   linear-gradient(rgba(255,255,0,0), rgba(255,255,0,1))

To use 'transparent' as a midway point between two colors, all an author 
needs to do is repeat the transparent part two times at 50% (i.e. red to 
transparent-red against transparent-blue to blue)

   linear-gradient(rgba(255,0,0,1), rgba(255,0,0,0) 50%, rgba(0,0,255,0) 
50%, rgba(0,0,255,1))

Now after a year, Firefox 15 and Chrome 21 shows the following demo the 


This behavior is now going onto well over a year in the wild.

> Does this version attend to address interpolation of gradients in
> non-premultiplied space? You're reply to me last year.
> http://lists.w3.org/Archives/Public/www-style/2011Aug/0109.html
>    | I don't believe we should select the color-space based
>    | on the syntax of the colors used, because a color should
>    | be independent of the syntax used for it.  Instead, I
>    | believe this should be done either by defining SVG's
>    | color-interpolation property to apply more widely to
>    | all CSS values, or by giving gradients a specialized
>    | switch to control the color-space they transition in.
>    | I'll address this in a later level of Image Values.
> Also in example 29 is found the text.
>    | In premultiplied space, transitions to or from
>    | "transparent" always look nice:
> Can this be changed to something like this.
>    # In premultiplied space, transitions to or from
>    # "transparent" look more natural when composite
>    # near white backgrounds.

Alan Gresley
Received on Wednesday, 29 August 2012 14:08:16 UTC

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