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<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Spray Paint</title>
<link rel="stylesheet" href="../include/style.css">
</head>
<body>
<header>
Example from <a href="http://amzn.com/1430236655?tag=html5anim-20"><em>Foundation HTML5 Animation with JavaScript</em></a>
</header>
<canvas id="canvas" width="400" height="400"></canvas>
<aside>Click and draw with the mouse.</aside>
<script src="../include/utils.js"></script>
<script>
window.onload = function () {
var canvas = document.getElementById('canvas'),
context = canvas.getContext('2d'),
mouse = utils.captureMouse(canvas),
imagedata = context.getImageData(0, 0, canvas.width, canvas.height),
pixels = imagedata.data,
brush_size = 25,
brush_density = 50,
brush_color;
canvas.addEventListener('mousedown', function () {
brush_color = utils.parseColor(Math.random() * 0xffffff, true); //to number
canvas.addEventListener('mousemove', onMouseMove, false);
}, false);
canvas.addEventListener('mouseup', function () {
canvas.removeEventListener('mousemove', onMouseMove, false);
}, false);
function onMouseMove () {
//loop over each brush bristle
for (var i = 0; i < brush_density; i++) {
var angle = Math.random() * Math.PI * 2,
radius = Math.random() * brush_size,
xpos = (mouse.x + Math.cos(angle) * radius) | 0,
ypos = (mouse.y + Math.sin(angle) * radius) | 0,
offset = (xpos + ypos * imagedata.width) * 4; //array index of canvas coordinate
//set the color of a pixel using its component colors: r,g,b,a (0-255)
pixels[offset] = brush_color >> 16 & 0xff; //red
pixels[offset + 1] = brush_color >> 8 & 0xff; //green
pixels[offset + 2] = brush_color & 0xff; //blue
pixels[offset + 3] = 255; //alpha
}
context.putImageData(imagedata, 0, 0);
}
};
</script>
</body>
</html>