Created
May 29, 2012 21:31
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| <html> | |
| <head> | |
| <title>Canvas bootstrap</title> | |
| <style>body { text-align: center; } canvas { border: 1px solid black; margin: auto;}</style> | |
| <script src="raf.js"></script> | |
| </head> | |
| <body> | |
| <canvas id="canvas" width="500" height="500"></canvas> | |
| <script> | |
| var helpers = { | |
| getMouse: function(e, canvas) { | |
| return { | |
| x: e.pageX - canvas.offsetLeft, | |
| y: e.pageY - canvas.offsetTop | |
| } | |
| } | |
| }; | |
| var canvas = document.getElementById("canvas"), | |
| context = canvas.getContext('2d'), | |
| lastPosition = null, | |
| currentPosition = null; | |
| canvas.addEventListener('mousemove', function(ev) { | |
| currentPosition = helpers.getMouse(ev, canvas); | |
| }); | |
| draw(); | |
| function draw() { | |
| requestAnimationFrame(draw); | |
| if (!currentPosition) return; | |
| if (!lastPosition) | |
| lastPosition = currentPosition; | |
| var d = dist(lastPosition, currentPosition); | |
| context.beginPath(); | |
| context.moveTo(lastPosition.x, lastPosition.y); | |
| context.lineTo(currentPosition.x, currentPosition.y); | |
| context.strokeStyle = rndColor(); | |
| context.lineWidth = Math.max(1, d); | |
| context.lineCap = 'butt'; | |
| context.lineJoin = 'bevel'; | |
| context.stroke(); | |
| context.closePath(); | |
| lastPosition = currentPosition; | |
| } | |
| function rndColor() { | |
| var s = '#', n; | |
| for (var i = 0; i < 3; i++) { | |
| n = Math.floor(Math.random() * 256).toString(16); | |
| s += (n.length == 1 ? '0' : '') + n; | |
| } | |
| return s; | |
| } | |
| function dist(a, b) { | |
| return Math.sqrt(Math.pow(b.x - a.x, 2) + (Math.pow(b.y - a.y, 2))); | |
| } | |
| </script> | |
| </body> | |
| </html> |
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| (function() { | |
| var lastTime = 0; | |
| var vendors = ['ms', 'moz', 'webkit', 'o']; | |
| for(var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) { | |
| window.requestAnimationFrame = window[vendors[x]+'RequestAnimationFrame']; | |
| window.cancelAnimationFrame = | |
| window[vendors[x]+'CancelAnimationFrame'] || window[vendors[x]+'CancelRequestAnimationFrame']; | |
| } | |
| if (!window.requestAnimationFrame) | |
| window.requestAnimationFrame = function(callback, element) { | |
| var currTime = new Date().getTime(); | |
| var timeToCall = Math.max(0, 16 - (currTime - lastTime)); | |
| var id = window.setTimeout(function() { callback(currTime + timeToCall); }, | |
| timeToCall); | |
| lastTime = currTime + timeToCall; | |
| return id; | |
| }; | |
| if (!window.cancelAnimationFrame) | |
| window.cancelAnimationFrame = function(id) { | |
| clearTimeout(id); | |
| }; | |
| }()); |
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