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Re: [css3-background] vastly different takes on "blur"

From: Brad Kemper <brad.kemper@gmail.com>
Date: Mon, 14 Jun 2010 15:55:51 -0700
Message-Id: <CFB305E8-7183-4E09-80DE-A8012E646998@gmail.com>
To: Brendan Kenny <bckenny@gmail.com>
Cc: fantasai <fantasai.lists@inkedblade.net>, Simon Fraser <smfr@me.com>, "L. David Baron" <dbaron@dbaron.org>, Brian Manthos <brianman@microsoft.com>, "www-style@w3.org" <www-style@w3.org>


On Jun 14, 2010, at 2:56 PM, Brendan Kenny <bckenny@gmail.com> wrote:


>
> To me, the new text actually seems more "you know what I
> mean"/"hand-waving" than before.

I don't understand why spec text that describes the required results  
is a bad thing. I don't think the steps taken to get there are nearly  
as important as clearly and precisely describing how it needs to end  
up. It is a visual effect, so we need to say something about what it  
should look like.

> This might not be tenable, but thinking of Simon's SVG filter
> suggestion and looking at the spec for feGaussianBlur
> http://www.w3.org/TR/SVG/filters.html#feGaussianBlur
> this whole conversation might be made a lot simpler by simply
> specifying the blur used rather than leaving it undefined.
>
> If the shadow is blurred by a Gaussian blur (or its box filter
> approximation) with a standard deviation of the blur-radius divided by
> 3 (or the "blur width" divided by 6), the effect will be exactly what
> we all seem to mean while still leaving room for efficient
> implementations.

I don't understand enough about Guassian math or whatever to say if  
that is enough or not. Is it? The Guassian blur filter in Photoshop  
gave me a much different blur width than Safari did with the same input.

> Based on what Rob posted, this is what Gecko is
> already doing.

Gecko gives me a blur width that is about twice as wide as the  
authored amount, so I still want to change that to be a more  
straightforward 1:1 relationship.

> This leaves the problem of defining the allowable approximation
> without a dependency on SVG, but since AFAIK all the major UAs already
> support this effect (either through SVG filters or IE's Blur filter),
> it seems like there should be a simple way to do this.
Received on Monday, 14 June 2010 22:56:40 GMT

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