浅谈利用缓存来优化HTML5 Canvas程序的性能

var testBox = function(){ var canvas = document.getElementById("cas"),

ctx = canvas.getContext('2d'), borderWidth = 2,

Balls = []; var ball = function(x , y , vx , vy , useCache){

this.x = x; this.y = y;

this.vx = vx; this.vy = vy;

this.r = getZ(getRandom(20,40)); this.color = [];

this.cacheCanvas = document.createElement("canvas"); thisthis.cacheCtx = this.cacheCanvas.getContext("2d");

this.cacheCanvas.width = 2*this.r; this.cacheCanvas.height = 2*this.r;

var num = getZ(this.r/borderWidth); for(var j=0;j<num;j++){

this.color.push("rgba("+getZ(getRandom(0,255))+","+getZ(getRandom(0,255))+","+getZ(getRandom(0,255))+",1)"); }