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Re: [fxtf-drafts] [filter-effects] Clarify what happens with failing pre-conditions on feConvolveMatrix

From: Dirk Schulze via GitHub <sysbot+gh@w3.org>
Date: Sun, 31 Dec 2017 19:56:45 +0000
To: public-fxtf-archive@w3.org
Message-ID: <issue_comment.created-354621234-1514750203-sysbot+gh@w3.org>
I used this simple example to verify the behavior in implementations:

```xml
<svg width="100%" height="220" style="outline: 1px solid red" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
 <defs>
   <filter id="convolve">
      <feFlood flood-color="green" result="flood"/>
      <feConvolveMatrix kernelMatrix="1 0 0 0 1 0 0 0 -1 0" in="SourceGraphic" result="kernel"/>
      <feComposite operator="over" in="kernel" in2="flood"/>
   </filter>
 </defs> 

 <g font-size="3em">
   <text x="225" y="75">Convolve</text>
   <text x="225" y="150" filter="url(#convolve)">Convolve</text>
 </g>
</svg>
```

* Firefox and Chrome treat the result of `feConvolveMatrix` as transparent black on failing preconditions.
* Safari does not render the entire element.
* Adobe Illustrator/PS makes the filter a pass through.

The pass through seems to be more in line to the behavior of browsers with failing preconditions on `feColorMatrix`'s `values` attribute. Here all browsers use the "initial value" instead which makes the filter a pass-through.

I couldn't verify Edge yet.

-- 
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Received on Sunday, 31 December 2017 19:56:47 UTC

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