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<!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>
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