js怎么把图标变成灰色

var imgObj = document.getElementById('js-image');
function gray(imgObj) {

    var canvas = document.createElement('canvas');
    var canvasContext = canvas.getContext('2d');
    var imgW = imgObj.width;
    var imgH = imgObj.height;
    canvas.width = imgW;
    canvas.height = imgH;
    canvasContext.drawImage(imgObj, 0, 0);
    var imgPixels = canvasContext.getImageData(0, 0, imgW, imgH);
    for(var y = 0; y < imgPixels.height; y++){
        for(var x = 0; x < imgPixels.width; x++){
            var i = (y * 4) * imgPixels.width + x * 4;
            var avg = (imgPixels.data[i] + imgPixels.data[i + 1] + imgPixels.data[i + 2]) / 3;
            imgPixels.data[i] = avg;
            imgPixels.data[i + 1] = avg;
            imgPixels.data[i + 2] = avg;
        }
    }
    canvasContext.putImageData(imgPixels, 0, 0, 0, 0, imgPixels.width, imgPixels.height);
    return canvas.toDataURL();

}
imgObj.src = gray(imgObj);

通过使用JavaScript技术上应该支持所有JavaScript的浏览器,包括IE6以下
代码来自Ajax Blender.