effect-reference-source-alpha-001.html

<!DOCTYPE html>
<html>
<title>CSS Filters: feMergeNode with SourceAlpha</title>
<link rel="author" title="Fredrik Söderquist" href="mailto:[email protected]">
<link rel="help" href="https://drafts.fxtf.org/filter-effects-1/#feMergeElement">
<link rel="help" href="https://drafts.fxtf.org/filter-effects-1/#attr-valuedef-in-sourcealpha">
<link rel="help" href="https://crbug.com/109224">
<link rel="match" href="reference/effect-reference-source-alpha-001-ref.html">
<meta name="assert" content="Check that SourceAlpha is correctly derived from SourceGraphic which is the output of the opacity(0) filter function which essentially sets all pixels to transparent."/>

<style>
div {
  position: absolute;
  width: 100px;
  height: 100px;
}
#test {
  background-color: red;
  filter: opacity(0) url(#f);
}
</style>
<div style="background-color: green"></div>
<div id="test">
<svg height="0">
  <filter id="f">
    <feMerge><feMergeNode in="SourceAlpha"></feMergeNode></feMerge>
  </filter>
</svg>
</div>

chromium/third_party/blink/web_tests/external/wpt/css/filter-effects/effect-reference-source-alpha-001.html