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[SVG11] filter subregion

From: T Rowley <tor@cs.brown.edu>
Date: Fri, 27 Jan 2006 11:14:42 -0600
Message-ID: <43DA5502.1010805@cs.brown.edu>
To: www-svg@w3.org

Working on implementing feFlood for mozilla SVG, I created a simple 
testcase and tried it on a number of SVG viewers.  Five implementations 
gave three different results.  Two of these appear only to differentiate 
due to a bug in subregion calculation.

My implementation appeared to interpret the filter subregion portion of 
the specification differently than all the others.  I read section 
15.7.3 to say that filter element only modifies the indicated portion of 
the input image, leaving the rest of the image alone.  Thus in the 
following example I'd expect to see a green circle with a translucent 
red rectangle punched out.  Other implementations seem to read the 
section as the element only outputs in the subregion, so they only give 
a translucent rectangle.

Which interpretation is intended, and can the language be clarified in 
an errata?

The testcase:

<svg width="200" height="200" xmlns="http://www.w3.org/2000/svg">

<filter id="flood">
   <feFlood x="25%" y="25%" width="50%" height="50%"
            flood-color="#ff0000" flood-opacity="0.75"/>
</filter>

<g fill="none" stroke="blue" stroke-width="4">
   <rect width="200" height="200"/>
   <line x2="200" y2="200"/>
   <line x1="200" y2="200"/>
</g>

<circle fill="green" filter="url(#flood)" cx="100" cy="100" r="90"/>

</svg>
Received on Friday, 27 January 2006 17:15:58 GMT

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