backdrop-filter-basic-blur-ref.html

<!DOCTYPE html>
<title>'backdrop-filter'</title>
<link rel="help" href="https://drafts.fxtf.org/filter-effects-2/#BackdropFilterProperty">
<script src="../support/simulate-backdrop-blur.js"></script>
<div>
  <p>Expected: A red box with three blurred boxes on top of it.</p>
  <p>All three should have similar levels of blur and opacity applied.</p>
</div>
<div class="colorbox">
  <div class="filterbox box1"></div>
  <div class="filterbox box2"></div>
  <div class="filterbox box3"></div>
</div>

<style>
.colorbox {
    width: 200px; height: 200px;
    background: red;
    position: absolute;
    left: 150px;
    top: 150px;
}
.filterbox {
    display: block;
    position: absolute;
    left: 100px;
    width: 150px;
    height: 100px;
    margin: 0px auto;
    border: 1px solid blue;
}
.box1 {
    top: -50px;
    background: #0000ff7f;
}
.box2 {
    top: 150px;
}
.box3 {
    top: 50px;
    left: -100px;
    opacity: 0.6;
}
</style>
<script>
  for (let box of document.querySelectorAll('.filterbox')) {
    simulateBackdropBlur(box, [document.querySelector('.colorbox')], 10);
  }
</script>

chromium/third_party/blink/web_tests/external/wpt/css/filter-effects/reference/backdrop-filter-basic-blur-ref.html