lachezar/index.html

## index.html
<!DOCTYPE html>
<html>
<head>
    <title>Mandelbrot + Web Workers!</title>
</head>
<body>

<canvas id="canvas" width="800" height="600" style="float: left">There should be a canvas here?!</canvas>

<script type="text/javascript">
    var workers = [];
    const poolCount = 8*6;
    var busyWorkers = 0;
    for (var i = 0; i < poolCount; i++) {
        var worker = new Worker('worker.js');
        worker.id = i;

        worker.onmessage = function(e) {
            var pixels = e.data;
            putPixels(this.id, pixels);
            busyWorkers--;
            updateWorkersCount();
        }

        workers.push(worker);
    }

    var canvas = document.getElementById('canvas');
    var context = canvas.getContext('2d');

    context.fillStyle = "rgb(0,0,0)";
    context.fillRect(0, 0, canvas.width, canvas.height);

    const maxWidth = 100;
    const maxHeight = 100;
    const columns = canvas.width / maxWidth;
    const rows = canvas.height / maxHeight;

    var zoomLevel = 1.0;
    var lastZoom = 1.0;
    var cx = 0;
    var cy = 0;
    var cxz = 0;
    var cyz = 0;

    draw(zoomLevel, 0, 0);

    function putPixels(id, pixels) {
        context.putImageData(pixels, (id%columns)*maxWidth, parseInt(id/columns)*maxHeight);
    }

    function draw(zoomLevel, cx, cy) {

        for (var i = 0; i < rows; i++) {
            for (var j = 0; j < columns; j++) {
                var pixels = context.getImageData(j*maxWidth, i*maxHeight, maxWidth, maxHeight);
                workers[i*columns+j].postMessage({pixels: pixels, sx: j*maxWidth+cx, sy: i*maxHeight+cy, w: maxWidth, h: maxHeight, canvasWidth: canvas.width, canvasHeight: canvas.height, zoom: zoomLevel});
                busyWorkers++;
            }
        }
    }

    canvas.onmousedown = function(e) {
        if (cxz != 0 && cyz != 0) {
            cx = cy = 0;
            lastZoom = 1;
        }
        cx += cxz+(e.pageX-canvas.width/2);
        cy += cyz+(e.pageY-canvas.height/2);

        draw(zoomLevel, cx, cy);
        cxz = cyz = 0;
    }

    canvas.addEventListener('DOMMouseScroll', zoom, false);

    function zoom(e) {
        var k = e.detail < 0 ? 2 : 0.5;
        zoomLevel *= k;
        lastZoom *= k;
        cxz = (cx+canvas.width/2)*lastZoom-canvas.width/2;
        cyz = (cy+canvas.height/2)*lastZoom-canvas.height/2;

        context.save();
        if (e.detail < 0) {
            context.scale(k, k);
            context.drawImage(canvas, -canvas.width/4, -canvas.height/4);
        }
        draw(zoomLevel, cxz, cyz);
        context.restore();

        updateZoomLevel();
    }

    function updateWorkersCount() {
        document.getElementById('workers_count').innerHTML = busyWorkers;
    }

    function updateZoomLevel() {
        document.getElementById('zoom_level').innerHTML = zoomLevel;
    }

</script>
<div style="float: left; margin-left: 10px;">
    <div>
        Workers: <span id="workers_count">0</span>
    </div>
    <div>
        Zoom: <span id="zoom_level">1</span>
    </div>
    <div>
        Click on the image to navigate through it. Scroll with the mouse for zoom.
    </div>
    <div>
        <a href="http://en.wikipedia.org/wiki/Mandelbrot_set" target="_blank">About Mandelbrot set</a>
    </div>
</div>
</body>
</html>

## worker.js
function onmessage(e) {
    var newPixels = calc(e.data);
    postMessage(newPixels);
}

function calc(data) {

    var pixels = data.pixels;
    var sx = data.sx;
    var sy = data.sy;
    var w = data.w;
    var h = data.h;
    var canvasWidth = data.canvasWidth;
    var canvasHeight = data.canvasHeight;
    var zoom = data.zoom;

    var minRe = -2.0;
    var maxRe = 1.0;
    var minIm = -1.2;
    var maxIm = minIm + (maxRe - minRe) * canvasHeight / canvasWidth;
    var reFactor = (maxRe - minRe) / (canvasWidth - 1);
    var imFactor = (maxIm - minIm) / (canvasHeight - 1);
    var maxIterations = 4096;

    for (var y = sy; y < sy+h; y++) {
        var cim = maxIm - ((y) * imFactor)/zoom;
        for (var x = sx; x < sx+w; x++) {
            var cre = minRe + ((x) * reFactor)/zoom;

            var zre = cre;
            var zim = cim;
            var k = 0;

            for(k = 0; k < maxIterations; k++) {
                if (zre*zre + zim*zim > 4) {
                    break;
                }

                var tempZre = zre*zre - zim*zim + cre;
                zim = 2 * zre * zim + cim;
                zre = tempZre;
            }


            plot(pixels, x-sx, y-sy, 4096 - Math.min(k, maxIterations));
        }

    }

    return pixels;
}

function plot(pixels, x, y, color) {
    var offset = 4 * pixels.width * y + 4 * x;

    pixels.data[offset+0] = (color & 16)*16;
    pixels.data[offset+1] = ((color >> 4) & 16)*16;
    pixels.data[offset+2] = ((color >> 8) & 16)*16;

}
	<!DOCTYPE html>
	<html>
	<head>
	<title>Mandelbrot + Web Workers!</title>
	</head>
	<body>

	<canvas id="canvas" width="800" height="600" style="float: left">There should be a canvas here?!</canvas>

	<script type="text/javascript">
	var workers = [];
	const poolCount = 8*6;
	var busyWorkers = 0;
	for (var i = 0; i < poolCount; i++) {
	var worker = new Worker('worker.js');
	worker.id = i;

	worker.onmessage = function(e) {
	var pixels = e.data;
	putPixels(this.id, pixels);
	busyWorkers--;
	updateWorkersCount();
	}

	workers.push(worker);
	}

	var canvas = document.getElementById('canvas');
	var context = canvas.getContext('2d');

	context.fillStyle = "rgb(0,0,0)";
	context.fillRect(0, 0, canvas.width, canvas.height);

	const maxWidth = 100;
	const maxHeight = 100;
	const columns = canvas.width / maxWidth;
	const rows = canvas.height / maxHeight;

	var zoomLevel = 1.0;
	var lastZoom = 1.0;
	var cx = 0;
	var cy = 0;
	var cxz = 0;
	var cyz = 0;

	draw(zoomLevel, 0, 0);

	function putPixels(id, pixels) {
	context.putImageData(pixels, (id%columns)maxWidth, parseInt(id/columns)maxHeight);
	}

	function draw(zoomLevel, cx, cy) {

	for (var i = 0; i < rows; i++) {
	for (var j = 0; j < columns; j++) {
	var pixels = context.getImageData(jmaxWidth, imaxHeight, maxWidth, maxHeight);
	workers[icolumns+j].postMessage({pixels: pixels, sx: jmaxWidth+cx, sy: i*maxHeight+cy, w: maxWidth, h: maxHeight, canvasWidth: canvas.width, canvasHeight: canvas.height, zoom: zoomLevel});
	busyWorkers++;
	}
	}
	}

	canvas.onmousedown = function(e) {
	if (cxz != 0 && cyz != 0) {
	cx = cy = 0;
	lastZoom = 1;
	}
	cx += cxz+(e.pageX-canvas.width/2);
	cy += cyz+(e.pageY-canvas.height/2);

	draw(zoomLevel, cx, cy);
	cxz = cyz = 0;
	}

	canvas.addEventListener('DOMMouseScroll', zoom, false);

	function zoom(e) {
	var k = e.detail < 0 ? 2 : 0.5;
	zoomLevel *= k;
	lastZoom *= k;
	cxz = (cx+canvas.width/2)*lastZoom-canvas.width/2;
	cyz = (cy+canvas.height/2)*lastZoom-canvas.height/2;

	context.save();
	if (e.detail < 0) {
	context.scale(k, k);
	context.drawImage(canvas, -canvas.width/4, -canvas.height/4);
	}
	draw(zoomLevel, cxz, cyz);
	context.restore();

	updateZoomLevel();
	}

	function updateWorkersCount() {
	document.getElementById('workers_count').innerHTML = busyWorkers;
	}

	function updateZoomLevel() {
	document.getElementById('zoom_level').innerHTML = zoomLevel;
	}

	</script>
	<div style="float: left; margin-left: 10px;">
	<div>
	Workers: <span id="workers_count">0</span>
	</div>
	<div>
	Zoom: <span id="zoom_level">1</span>
	</div>
	<div>
	Click on the image to navigate through it. Scroll with the mouse for zoom.
	</div>
	<div>
	<a href="http://en.wikipedia.org/wiki/Mandelbrot_set" target="_blank">About Mandelbrot set</a>
	</div>
	</div>
	</body>
	</html>
	function onmessage(e) {
	var newPixels = calc(e.data);
	postMessage(newPixels);
	}

	function calc(data) {

	var pixels = data.pixels;
	var sx = data.sx;
	var sy = data.sy;
	var w = data.w;
	var h = data.h;
	var canvasWidth = data.canvasWidth;
	var canvasHeight = data.canvasHeight;
	var zoom = data.zoom;

	var minRe = -2.0;
	var maxRe = 1.0;
	var minIm = -1.2;
	var maxIm = minIm + (maxRe - minRe) * canvasHeight / canvasWidth;
	var reFactor = (maxRe - minRe) / (canvasWidth - 1);
	var imFactor = (maxIm - minIm) / (canvasHeight - 1);
	var maxIterations = 4096;

	for (var y = sy; y < sy+h; y++) {
	var cim = maxIm - ((y) * imFactor)/zoom;
	for (var x = sx; x < sx+w; x++) {
	var cre = minRe + ((x) * reFactor)/zoom;

	var zre = cre;
	var zim = cim;
	var k = 0;

	for(k = 0; k < maxIterations; k++) {
	if (zrezre + zimzim > 4) {
	break;
	}

	var tempZre = zrezre - zimzim + cre;
	zim = 2 * zre * zim + cim;
	zre = tempZre;
	}


	plot(pixels, x-sx, y-sy, 4096 - Math.min(k, maxIterations));
	}

	}

	return pixels;
	}

	function plot(pixels, x, y, color) {
	var offset = 4 * pixels.width * y + 4 * x;

	pixels.data[offset+0] = (color & 16)*16;
	pixels.data[offset+1] = ((color >> 4) & 16)*16;
	pixels.data[offset+2] = ((color >> 8) & 16)*16;

	}