canvas-transparency-and-composite.html

<script src="../../resources/testharness.js"></script>
<script src="../../resources/testharnessreport.js"></script>
<body>

<script>
test(function(t) {

    var ctx = document.createElement('canvas').getContext('2d');
    ctx.globalCompositeOperation = "source-over";
    ctx.fillStyle = 'rgba(0, 0, 0, 0)';
    ctx.fillRect(0, 0, 100, 100);

    ctx.save();
    ctx.translate(0, 100);
    ctx.scale(1, -1);
    ctx.fillStyle = 'green';
    ctx.fillRect(0, 0, 100, 100);
    ctx.restore();

    assert_array_equals(ctx.getImageData(2, 1, 1, 1).data.slice(0, 3), [0, 128, 0]);

}, "Series of tests to ensure correct behaviour of composite on a fully transparent color.");
</script>
</body>

chromium/third_party/blink/web_tests/fast/canvas/canvas-transparency-and-composite.html