<!--
     Any copyright is dedicated to the Public Domain.
     http://creativecommons.org/publicdomain/zero/1.0/
-->
<svg xmlns="http://www.w3.org/2000/svg" width="200" height="200">

  <title>Testcase for alpha mask</title>

  <!-- From https://bugzilla.mozilla.org/show_bug.cgi?id=793617 -->

  <mask id="m" maskContentUnits="objectBoundingBox" style="mask-type: alpha">
    <rect x=".1" y=".1" width=".8" height=".8" fill="black" fill-opacity="0.5"/>
  </mask>
  <rect width="100" height="100" fill="blue" mask="url(#m)"/>
</svg>