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

From: Lea Verou <lea@verou.me>
Date: Wed, 19 Feb 2014 19:19:13 +0200
Cc: www-style list <www-style@w3.org>
Message-Id: <AACF93DB-A1D1-45F2-9137-21A6CBE82D35@verou.me>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
That’s not why I was confused, but I tested it in UAs and it is double indeed. I guess I was confused because the color transition is not linear, so it *seemed* smaller. 

On Feb 19, 2014, at 19:01, Tab Atkins Jr. <jackalmage@gmail.com> wrote:

> 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 17:19:37 UTC

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