imgproxy/testdata/test1.drop-shadow.svg

<svg width="200" height="100">
  <defs>
    <filter id="dropShadow">
      <feDropShadow in="SourceGraphic" dx="2" dy="1" stdDeviation="3" flood-opacity="0.8" flood-color="#0f0" width="200%" height="200%"/>
    </filter>
  </defs>
  <rect width="200" height="100" fill="#fff" />
  <rect x="50" y="25" width="100" height="50" fill="#f00" filter="url(#dropShadow)" />
</svg>