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[Bug 10169] The discontinuity at shadowBlur = 8 here is weird. We have no interop on exact shadow algorithms right now anyway, so maybe it could be fixed in the spec? Clearly authors aren't depending on pixel-perfect canvas shadows. Maybe it should just be the num

From: <bugzilla@jessica.w3.org>
Date: Wed, 14 Jul 2010 21:01:17 +0000
To: public-html-bugzilla@w3.org
Message-Id: <E1OZ94v-0007U9-Q2@jessica.w3.org>
http://www.w3.org/Bugs/Public/show_bug.cgi?id=10169


Aryeh Gregor <Simetrical+w3cbug@gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |Simetrical+w3cbug@gmail.com




--- Comment #1 from Aryeh Gregor <Simetrical+w3cbug@gmail.com>  2010-07-14 21:01:17 ---
Document showing lack of interop:

data:text/html,<!doctype html>
<canvas height="300" width="300"></canvas>
<script>
window.addEventListener('load', function () {
context = document.getElementsByTagName("canvas")[0].getContext("2d");
context.shadowBlur = 50;
context.shadowColor = 'black';
context.fillRect(100, 100, 100, 100); }, false);
</script>

This looks distinctly different in fairly recent WebKit, Gecko, and Presto
(Chrome dev, Firefox 4b1, Opera 10.60).  From reading the specs, not knowing
anything about Gaussian blurs, I'd think it should look the same as:

<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
<svg xmlns="http://www.w3.org/2000/svg"><defs>
<filter id="Gaussian_Blur"><feGaussianBlur in="SourceGraphic"
stdDeviation="5"/></filter>
</defs>
<rect x="100" y="100" width="100" height="100"
style="fill:black;filter:url(#Gaussian_Blur)"/>
</svg>

which Chrome and Opera render identically to one another, but very different to
how they render the canvas.  So it should be safe to change the algorithm here
substantially.  Although probably not to the point of matching SVG, on second
thought, since that's very different from what anyone does now for canvas (by
an order of magnitude in this case).

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Received on Wednesday, 14 July 2010 21:01:19 UTC

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