description("Ensure correct behavior of canvas with drawImage+shadow after scaling. A blue and red checkered pattern should be displayed.");

function print(message, color)
{
    var paragraph = document.createElement("div");
    paragraph.appendChild(document.createTextNode(message));
    paragraph.style.fontFamily = "monospace";
    if (color)
        paragraph.style.color = color;
    document.getElementById("console").appendChild(paragraph);
}

function shouldBeAround(a, b)
{
    var evalA;
    try {
        evalA = eval(a);
    } catch(e) {
        evalA = e;
    }

    if (Math.abs(evalA - b) < 10)
        print("PASS " + a + " is around " + b , "green")
    else
        print("FAIL " + a + " is not around " + b + " (actual: " + evalA + ")", "red");
}

// Create auxiliary canvas to draw to and create an image from.
// This is done instead of simply loading an image from the file system
// because that would throw a SECURITY_ERR DOM Exception.
var aCanvas = document.createElement('canvas');
aCanvas.setAttribute('width', '50');
aCanvas.setAttribute('height', '50');
var aCtx = aCanvas.getContext('2d');

// Fill the same canvas.
aCtx.fillStyle = 'rgba(0, 0, 255, 1)';
aCtx.fillRect(0, 0, 50, 50);

// Create the image object to be drawn on the master canvas.
var img = new Image();
img.onload = drawImageToCanvasAndCheckPixels;
img.src = aCanvas.toDataURL(); // set a data URI of the base64 encoded image as the source

// Create master canvas.
var canvas = document.createElement('canvas');
document.body.appendChild(canvas);
canvas.setAttribute('width', '1000');
canvas.setAttribute('height', '1000');
var ctx = canvas.getContext('2d');

function drawImageToCanvasAndCheckPixels() {
    ctx.scale(2, 2);
    ctx.shadowOffsetX = 100;
    ctx.shadowOffsetY = 100;
    ctx.fillStyle = 'rgba(0, 0, 255, 1)';

    ctx.shadowColor = 'rgba(255, 0, 0, 1.0)';
    ctx.drawImage(img, 50, 50);

    ctx.shadowColor = 'rgba(255, 0, 0, 0.3)';
    ctx.drawImage(img, 50, 150);

    ctx.shadowColor = 'rgba(255, 0, 0, 1.0)';
    ctx.shadowBlur = 10;
    ctx.drawImage(img, 150, 50);

    ctx.shadowColor = 'rgba(255, 0, 0, 0.3)';
    ctx.drawImage(img, 150, 150);

    checkPixels();
}

var d; // imageData.data

function checkPixels() {

    // Verify solid shadow.
    d = ctx.getImageData(205, 205, 1, 1).data;
    shouldBe('d[0]', '255');
    shouldBe('d[1]', '0');
    shouldBe('d[2]', '0');
    shouldBe('d[3]', '255');

    d = ctx.getImageData(295, 295, 1, 1).data;
    shouldBe('d[0]', '255');
    shouldBe('d[1]', '0');
    shouldBe('d[2]', '0');
    shouldBe('d[3]', '255');

    d = ctx.getImageData(205, 295, 1, 1).data;
    shouldBe('d[0]', '255');
    shouldBe('d[1]', '0');
    shouldBe('d[2]', '0');
    shouldBe('d[3]', '255');

    // Verify solid alpha shadow.
    d = ctx.getImageData(201, 401, 1, 1).data;
    shouldBe('d[0]', '255');
    shouldBe('d[1]', '0');
    shouldBe('d[2]', '0');
    shouldBeAround('d[3]', '76');

    d = ctx.getImageData(290, 401, 1, 1).data;
    shouldBe('d[0]', '255');
    shouldBe('d[1]', '0');
    shouldBe('d[2]', '0');
    shouldBeAround('d[3]', '76');

    d = ctx.getImageData(290, 498, 1, 1).data;
    shouldBe('d[0]', '255');
    shouldBe('d[1]', '0');
    shouldBe('d[2]', '0');
    shouldBeAround('d[3]', '76');

    // Verify blurry shadow.
    d = ctx.getImageData(398, 205, 1, 1).data;
    shouldBe('d[0]', '255');
    shouldBe('d[1]', '0');
    shouldBe('d[2]', '0');
    shouldBeAround('d[3]', '83');

    d = ctx.getImageData(501, 205, 1, 1).data;
    shouldBe('d[0]', '255');
    shouldBe('d[1]', '0');
    shouldBe('d[2]', '0');
    shouldBeAround('d[3]', '83');

    d = ctx.getImageData(500, 300, 1, 1).data;
    shouldBe('d[0]', '255');
    shouldBe('d[1]', '0');
    shouldBe('d[2]', '0');
    shouldBeAround('d[3]', '53');

    // Verify blurry alpha shadow.
    d = ctx.getImageData(398, 405, 1, 1).data;
    shouldBe('d[0]', '255');
    shouldBe('d[1]', '0');
    shouldBe('d[2]', '0');
    shouldBeAround('d[3]', '24');

    d = ctx.getImageData(405, 501, 1, 1).data;
    shouldBe('d[0]', '255');
    shouldBe('d[1]', '0');
    shouldBe('d[2]', '0');
    shouldBeAround('d[3]', '24');

    d = ctx.getImageData(405, 501, 1, 1).data;
    shouldBe('d[0]', '255');
    shouldBe('d[1]', '0');
    shouldBe('d[2]', '0');
    shouldBeAround('d[3]', '24');
}