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

From: fantasai <fantasai.lists@inkedblade.net>
Date: Fri, 11 Jun 2010 17:21:34 -0700
Message-ID: <4C12D30E.7010503@inkedblade.net>
To: Brian Manthos <brianman@microsoft.com>
CC: Brad Kemper <brad.kemper@gmail.com>, Simon Fraser <smfr@me.com>, "L. David Baron" <dbaron@dbaron.org>, "www-style@w3.org" <www-style@w3.org>
On 06/11/2010 04:58 PM, Brian Manthos wrote:
> Testability question.
>
> As we converge on the final language, can we make sure that it expresses where --
> regardless  of specifics of blur algorithm -- a test harness could check for fully
> transparent or fully  opaque pixels?
>
> What I mean is that there should be a no-man's-land beyond the edge of the
> specified blur region where no blurred pixels should be found.
>
>
> My impression is that the intentional flexibility in the specification is
> (a) about how the blur ramps up / down -- linear, exponential, etc. -- and
> the impact of neighboring pixels and (b) NOT about allowing the blur to
> bleed off to infinity or to shrink to barely perceptible.

The current spec wording was the best I could come up with when someone told
me "it's underspecified what blur means". As Simon points out, it's not
actually correct wrt the original spec's intention.

I don't know enough about graphics to tell whether we can actually check for
fully transparent or fully opaque pixels under a blur algorithm. Someone
else will have to answer that.

But as far as testability is concerned, even if we allow algorithms that
have an infinite die-off, we can (and probably should) restrict it to a
certain percentage, e.g. check for < 1% or < 0.1% opaque in the "transparent"
region, and > 99% or > 99.9% opaque in the "opaque" region.

~fantasai
Received on Saturday, 12 June 2010 00:22:12 GMT

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