transferFromImageBitmap-ToBlob-offscreen.html

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This WPT test may be referenced by the following Test IDs:
- /imagebitmap-renderingcontext/transferFromImageBitmap-ToBlob-offscreen.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 testCanvas(ctx, r, g, b, a)

    var color = ctx.getImageData(5, 5, 1, 1).data;

    assert_array_equals(color, [r, g, b, a]);

promise_test(function() {

    function transferFromImageBitmapToBlobOffscreen(greenImage) {

        var bitmapCanvas = new OffscreenCanvas(width,height);

        var bitmapCtx = bitmapCanvas.getContext('bitmaprenderer');

        bitmapCtx.transferFromImageBitmap(greenImage);

        return bitmapCanvas.convertToBlob();

    function drawBlobToCanvas(blob) {

        // Make sure the bitmap renderer canvas is filled correctly.

        var pngImage = new Image();

        var myCanvasToTest = document.createElement('canvas');

        myCanvasToTest.width = width;

        myCanvasToTest.height = height;

        // Wait for the blob img to load.

        return new Promise(function(resolve) {

            pngImage.src = URL.createObjectURL(blob);

            pngImage.onload = function() {

                var myCtxToTest = myCanvasToTest.getContext('2d');

                myCtxToTest.drawImage(pngImage, 0, 0);

                resolve(myCtxToTest);

};

});

    var greenCanvas = document.createElement('canvas');

    greenCanvas.width = width;

    greenCanvas.height = height;

    var greenCtx = greenCanvas.getContext('2d');

    greenCtx.fillStyle = '#0f0';

    greenCtx.fillRect(0, 0, width, height);

    return createImageBitmap(greenCanvas).then(

        greenImage => transferFromImageBitmapToBlobOffscreen(greenImage)

    ).then(

        blob => drawBlobToCanvas(blob)

    ).then(

        ctx => testCanvas(ctx, 0, 255, 0, 255)

);

},'Test that convertToBlob works and produce the expected image');

</script>