计算图片主题颜色

计算图片主题颜色，附件是例子图片和执行效果图。

[代码][HTML]代码 
<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title>图片主题色</title>
    <script src="../../lib/jquery.js"></script>
    <script>
        function calcThemeColor(image){
            var context=document.createElement('canvas').getContext("2d");
            context.drawImage(image,0,0);
            var imageData=context.getImageData(0,0,image.width,image.height);
            var worker=new Worker("calcColor.js");
            worker.postMessage(imageData);
            worker.onmessage=function(event){
                var themeColor=event.data;
                $("body").css("background","rgb("+themeColor.red+","+themeColor.green+","+themeColor.blue+")");
                console.log(themeColor);
            };
        }
    </script>
</head>
<body>
    <img id="image" onload="calcThemeColor(this)" src="images/1.jpg" alt="" />
</body>
</html>
[代码][JavaScript]代码 
onmessage=function(event){
    var imageData=event.data;
    var rSum=0;
    var gSum=0;
    var bSum=0;
    var dataCount=imageData.data.length/4;
    for(var i=0,n=imageData.data.length;i<n;i+=4){
        var num=i/4;
        var redColor=imageData.data[i+0];
        var greenColor=imageData.data[i+1];
        var blueColor=imageData.data[i+2];
 
        var avgR=num>0?rSum/num:redColor;
        if(Math.abs(redColor-avgR)<250){
            rSum+=avgR;
        }else{
            rSum+=redColor; //red
        }
        var avgG=num>0?gSum/num:greenColor;
        if(Math.abs(greenColor-avgG)<250){
            gSum+=avgG;
        }else{
            gSum+=greenColor; //green
        }
        var avgB=num>0?bSum/num:blueColor;
        if(Math.abs(blueColor-avgB)<250){
            bSum+=avgB;
        }else{
            bSum+=blueColor; //blue
        }
        //var a=imageData.data[i+3]; //alpha
    }
    var themeColor={
        red:Math.round(rSum/dataCount),
        green:Math.round(gSum/dataCount),
        blue:Math.round(bSum/dataCount)
    };
    postMessage(themeColor);
}