jquery帆布圈

工作代码：http://jsfiddle.net/ajFsx/

window.onload = function() {
    canvas  = document.getElementById('timer'),seconds = document.getElementById('counter'),ctx     = canvas.getContext('2d'),sec     = 180,countdown = sec;
    ctx.lineWidth = 8;
    ctx.strokeStyle = "#528f20";
    var 
    startAngle = 0,time       = 0,intv       = setInterval(function(){
        var endAngle = (Math.PI * time * 2 / sec);
        ctx.arc(65,35,30,startAngle,endAngle,false);   
        startAngle = endAngle;
        ctx.stroke();

        countdown--;
        if ( countdown > 60){
            seconds.innerHTML = Math.floor(countdown/60);
            seconds.innerHTML += ":" + countdown%60;
        }
        else{
            seconds.innerHTML = countdown;
        }
        if (++time > sec,countdown == 0 ) { clearInterval(intv),$("#timer,#counter").remove(),$("#timers").prepend('<img id="theImg" src="#" />'); }
    },10);
}​

我的问题是以下如何让这张图更好看,所以没有像素？

我在jquery画布上搜索了很多,但我似乎无法找到我正在寻找的地方.