trns-chunk.html - mozsearch

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This test has a WPT meta file that expects 1 subtest issues.
This WPT test may be referenced by the following Test IDs:
- /png/trns-chunk.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<title>PNG test: tRNS chunk</title>

<link rel="help" href="https://w3c.github.io/PNG-spec/#11tRNS">

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

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

<script src="/html/canvas/resources/canvas-tests.js"></script>

<body>

<h1>tRNS chunk handling</h1>

<p class="desc">test ignored high bits on lower bit depth tRNS</p>

<p class="output">Actual output:</p>

<canvas id="c" class="output" width="100" height="50"><p class="fallback">FAIL (fallback content)</p></canvas>

<ul id="d"></ul>

<script>

var t = async_test("test ignored high bits on lower bit depth tRNS");

const img = new Image();

img.onload = () => {

  _addTest(function(canvas, ctx) {

    ctx.drawImage(img, 0, 0);

    var pixel = ctx.getImageData(5, 5, 1, 1, {colorSpace: "srgb", storageFormat: "uint8"}).data;

    const pixel_expected = [255, 0, 0, 0];

    const epsilon = 2;

    _assertSame(pixel.length, pixel_expected.length, "pixel.length", "pixel_expected.length");

    // Ignore the color channel comparisons.

    // The image itself stores 255 red, 0 green, 0 blue.

    // But there may not be a requirement that this be preserved

    // while decoding or through canvas processing.

    assert_approx_equals(pixel[3], pixel_expected[3], epsilon);

});

};

img.src = "support/trns-high-bits-set.png";

</script>