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Re: [css-backgrounds][Editorial] Color transition length in blurred shadows

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Wed, 19 Feb 2014 09:01:51 -0800
Message-ID: <CAAWBYDDvGZPi-phAXrfmX8NJUouBkk2SyBDEH=iQDTd3GXe=vw@mail.gmail.com>
To: Lea Verou <lea@verou.me>
Cc: www-style list <www-style@w3.org>
On Wed, Feb 19, 2014 at 4:12 AM, Lea Verou <lea@verou.me> wrote:
> In [1] there's a note that says:
>> Note this means for a long, straight shadow edge, the blur radius will
>> create a visibly apparent color transition approximately the twice length of
>> the blur radius that is perpendicular to and centered on the shadow's edge,
>> and that ranges from almost the full shadow color at the endpoint inside the
>> shadow to almost fully transparent at the endpoint outside it.
>
> Shouldn’t this be “the length of the blur radius” instead of “twice the
> length of the blur radius”?

Nope, the blur radius says how far out from the original sharp edge
the blur will extend.  But the blur is symmetric, so it affects the
color *within* the original shape as well, by the same distance.  Thus
the total area affected by blurring is twice the blur radius.

~TJ
Received on Wednesday, 19 February 2014 17:02:38 UTC

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