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

From: Brad Kemper <brad.kemper@gmail.com>
Date: Tue, 27 Jul 2010 08:50:27 -0700
Cc: Sylvain Galineau <sylvaing@microsoft.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>
Message-Id: <6E3C6096-3881-48F6-91C8-4288FE0EEA9F@gmail.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>

On Jul 27, 2010, at 7:50 AM, Tab Atkins Jr. wrote:


> 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.

I prefer it in language that gave the guassian blur you mention as the example, but with more precise language (similar to how we currently word it) about which part of the resultant blur will match the authored value. Something like this:

The exact algorithm is not defined; however for a long, straight shadow edge, this should create a color transition of twice the length of the blur distance that is perpendicular to and centered on the shadow's edge, and that ranges from the full shadow color at the radius endpoint inside the shadow to fully transparent at the endpoint outside it. Within the blur transition area, as defined by the authored blur value, no pixel should be less than 2% opacity or more than 98% opacity. Such pixels would fall outside the distance specified by the author, as they would be when using a guassian blur with a stdev equal to half the authored length.

Or something like that.
Received on Tuesday, 27 July 2010 15:51:03 GMT

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