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context-creation-offscreen-with-alpha.html
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context-creation-offscreen-with-alpha.html
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<!DOCTYPE html>
<meta charset="utf-8">
<title>Canvas's ImageBitmapRenderingContext test</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<link rel="help" href="https://html.spec.whatwg.org/multipage/scripting.html#the-imagebitmap-rendering-context">
<script>
var width = 10;
var height = 10;
function testImageBitmap(image, opts, expectedR, expectedG, expectedB, expectedA)
{
var dstCanvas = new OffscreenCanvas(width,height);
var dstCtx = dstCanvas.getContext('bitmaprenderer', opts);
dstCtx.transferFromImageBitmap(image);
var myCanvas = document.createElement('canvas');
myCanvas.width = width;
myCanvas.height = height;
var myCtx = myCanvas.getContext('2d');
myCtx.drawImage(dstCanvas, 0, 0);
var color = myCtx.getImageData(5, 5, 1, 1).data;
assert_array_approx_equals(color, [expectedR, expectedG, expectedB, expectedA],1);
}
promise_test(function() {
var srcCanvas = document.createElement('canvas');
srcCanvas.width = width;
srcCanvas.height = height;
var ctx = srcCanvas.getContext('2d');
ctx.fillStyle = 'rgba(0, 255, 0, 0.5)';
ctx.fillRect(0, 0, width, height);
return createImageBitmap(srcCanvas).then(function(image) {
testImageBitmap(image, {alpha: false}, 0, 255, 0, 128);
});
}, "Test that an ImageBitmapRenderingContext with alpha disabled makes the canvas opaque");
promise_test(function() {
var srcCanvas = document.createElement('canvas');
srcCanvas.width = width;
srcCanvas.height = height;
var ctx = srcCanvas.getContext('2d');
ctx.fillStyle = 'rgba(0, 255, 0, 0.5)';
ctx.fillRect(0, 0, width, height);
return createImageBitmap(srcCanvas).then(function(image) {
testImageBitmap(image, {alpha: true}, 0, 255, 0, 128);
});
}, "Test that an ImageBitmapRenderingContext with alpha enabled preserves the alpha");
promise_test(function() {
var srcCanvas = document.createElement('canvas');
srcCanvas.width = width;
srcCanvas.height = height;
var ctx = srcCanvas.getContext('2d');
ctx.fillStyle = 'rgba(0, 255, 0, 0.5)';
ctx.fillRect(0, 0, width, height);
return createImageBitmap(srcCanvas).then(function(image) {
testImageBitmap(image, {}, 0, 255, 0, 128);
});
}, "Test that the 'alpha' context creation attribute is true by default");
</script>