<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink= "http://www.w3.org/1999/xlink">
  <defs>
    <filter id="filter" filterUnits="objectBoundingBox" x="0%" y="0%" width="100%" height="100%">
      <feConvolveMatrix order="3 1" kernelMatrix="0.3333 0.3333 0.3333" edgeMode="none"/>
    </filter>
  </defs>
  <!-- Use the filter (otherwise, scour discards it before it trips over it) -->
  <image id="png" x="10" y="30" width="150" height="50" xlink:href="raster.png"
         filter="url(#filter)"/>
</svg>

Use number-optional-number variant of kernelUnitLength
test: Use number-optional-number variant of kernelUnitLength

Signed-off-by: Niels Thykier <a802a5730c0da02a06106670cc12c7838c6e90dc@thykier.net>
