1// Copyright (c) 2012 The Chromium Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style license that can be 3// found in the LICENSE file. 4 5var sprites = (function() { 6 var objs; 7 var width; 8 var height; 9 var SPRITE_SPEED = 2; 10 11 var sprites = {}; 12 sprites.init = function(w, h) { 13 objs = []; 14 width = w; 15 height = h; 16 }; 17 sprites.add = function(img) { 18 var obj = { img: img, 19 x: Math.random() * (width - img.width), 20 y: Math.random() * (height - img.height), 21 dx: SPRITE_SPEED * (Math.random() < .5 ? -1 : 1), 22 dy: SPRITE_SPEED * (Math.random() < .5 ? -1 : 1) }; 23 objs.push(obj); 24 }; 25 sprites.draw = function(context) { 26 for (var i = 0, len = objs.length; i < len; ++i) { 27 var obj = objs[i]; 28 29 obj.x += obj.dx; 30 if ((obj.x > (width - obj.img.width)) || (obj.x < 0)) 31 obj.dx *= -1; 32 33 obj.y += obj.dy; 34 if ((obj.y > (height - obj.img.height)) || (obj.y < 0)) 35 obj.dy *= -1; 36 37 context.drawImage(obj.img, obj.x, obj.y); 38 }; 39 }; 40 return sprites; 41})(); 42