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

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Tue, 27 Jul 2010 17:12:30 -0700
Message-ID: <AANLkTi=zwHYX1+KXS9uzPj98j4UBd7-RNhDLKgQ0NKPb@mail.gmail.com>
To: Brad Kemper <brad.kemper@gmail.com>
Cc: Sylvain Galineau <sylvaing@microsoft.com>, Dennis Amrouche <dennis@screenlabor.de>, Brian Manthos <brianman@microsoft.com>, Aryeh Gregor <Simetrical+w3c@gmail.com>, "L. David Baron" <dbaron@dbaron.org>, SimonFraser <smfr@me.com>, Brendan Kenny <bckenny@gmail.com>, www-style list <www-style@w3.org>
On Tue, Jul 27, 2010 at 4:55 PM, Brad Kemper <brad.kemper@gmail.com> wrote:
> If you have a picture of what it is supposed to look like, with
> the predicted values rendered, then you could more easily make an initial
> visual comparison.

Sure, there's nothing *wrong* with making an extra picture and doing
pixel comparisons that way.  It's just not necessary for the actual
conformance testing.


> But the approximation would fail your test, because you're comparing each
> pixel's value against the value of an actual gaussian distribution. Firefox
> would fail, because it has noticeable banding, whereas an actual gaussian
> distribution presumably wouldn't.

I think you might be confused - Firefox passes my suggested
conformance criteria just fine (if we pretend that it treats the blur
length properly).  It is, at worst, 6 color units away from a true
gaussian, which is within the 5% boundary.

The conformance criteria is that each pixel must be within some
percentage of a true gaussian.  Banding like you see in Firefox near
the edges is perfectly acceptable as long as it remains within the
specified percentage of the reference value.

~TJ
Received on Wednesday, 28 July 2010 00:13:22 GMT

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