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Re: [css3-background] Where we are with Blur value discussion

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Tue, 27 Jul 2010 07:50:23 -0700
Message-ID: <AANLkTinf_zgYSY_jww20397rNZfpLExFpDgLm2eKZ3u-@mail.gmail.com>
To: Sylvain Galineau <sylvaing@microsoft.com>
Cc: Brad Kemper <brad.kemper@gmail.com>, Dennis Amrouche <dennis@screenlabor.de>, Brian Manthos <brianman@microsoft.com>, Aryeh Gregor <Simetrical+w3c@gmail.com>, "L. David Baron" <dbaron@dbaron.org>, Simon Fraser <smfr@me.com>, Brendan Kenny <bckenny@gmail.com>, www-style list <www-style@w3.org>
On Mon, Jul 26, 2010 at 8:58 PM, Sylvain Galineau
<sylvaing@microsoft.com> wrote:
>> From: www-style-request@w3.org [mailto:www-style-request@w3.org] On
>> Behalf Of Tab Atkins Jr.
>
>
>> So, yeah, like Brad says, if the "range of pixels within which the
>> shadow becomes effectively invisible to the human eye" is a bit off at
>> very high shadow blur lengths, you'll never notice.  It's a pretty
>> unimportant point.
>
> To the human eye, sure. Now, can we  talk about testing implementations
> for conformance ?

I've suggested precisely what I think the criteria should be already.
The shadow must approximate a gaussian blur with a stdev equal to half
the length, with each pixel being within 5% (of the whole color space,
so about 12 "color units" to each side) of the color that a true
gaussian would be.

That should fix behavior sufficiently to make everyone that conforms
"look the same", while allowing enough wiggle room for the current
approximations to a gaussian (triple box blur, generally) to fit.  The
Skia blur that Chrome uses on some platforms will not be conformant.

~TJ
Received on Tuesday, 27 July 2010 14:59:26 GMT

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