context-creation-offscreen-with-alpha.html

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This WPT test may be referenced by the following Test IDs:
- /imagebitmap-renderingcontext/context-creation-offscreen-with-alpha.html - WPT Dashboard Interop Dashboard

<!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>