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

From: L. David Baron <dbaron@dbaron.org>
Date: Tue, 13 Jul 2010 13:21:17 -0700
To: Brad Kemper <brad.kemper@gmail.com>
Cc: www-style list <www-style@w3.org>, fantasai <fantasai.lists@inkedblade.net>, Brian Manthos <brianman@microsoft.com>, Simon Fraser <smfr@me.com>
Message-ID: <20100713202117.GA1554@pickering.dbaron.org>
On Tuesday 2010-07-13 07:15 -0700, Brad Kemper wrote:
> Arguments in favor of the distance measuring the Entire blur region width (current spec language):
> 
> 1) The entire perimeter is blurred, outer and inner, not just
> outer, so it is logical that the width of the entire blur effect
> width should match the authored value. 

However, for 'text-shadow' the value is called the "blur radius",
not the "blur diameter" (and has been called "blur radius" since
http://www.w3.org/TR/1998/REC-CSS2-19980512/text.html#text-shadow-props ).

(I'm not sure when the definition of 'box-shadow' changed from using
the commonly-used term "blur radius" to using the new term "blur
distance".)

I'd also note that blurring is implemented as a generic
transformation of images; it's not just something applied to edges.
In that form, I think measuring in terms of the radius
(approximating the concept of how far away from its original
location can the color of a point can get) makes more sense than
using the diameter (approximating the distance between the two
farthest points in opposite directions that the color of a pixel can
reach).

So I also favor switching the definition of box-shadow to match
text-shadow and to describe a blur radius rather than a diameter.

-David

-- 
L. David Baron                                 http://dbaron.org/
Mozilla Corporation                       http://www.mozilla.com/
Received on Tuesday, 13 July 2010 20:21:53 GMT

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