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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.

Received on Wednesday, 28 July 2010 00:13:22 UTC

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