<!--
     Any copyright is dedicated to the Public Domain.
     http://creativecommons.org/publicdomain/zero/1.0/
-->
<svg xmlns="http://www.w3.org/2000/svg"
     width="50%"
     viewBox="0 0 4 64"
     preserveAspectRatio="none">
  <title>Image with percent width, omitted height, viewbox</title>
  <rect y="0" width="100%" height="50%" fill="lime"/>
  <rect y="50%" width="100%" height="50%" fill="aqua"/>
</svg>