问如何下载css-3滤镜应用的图像

EN

 $(document).ready(function () {
        var img = document.getElementById("image1");
        // filters
        var grayValue = "0.2";
        var blurValue = "1px";
        var brightnessValue = "150%";
        var saturateValue = "0.2";
        var contrastValue = "0.2";
        var sepiaValue = "0.2";
        // `filterVal`
        var filterVal = "grayscale(" + grayValue + ") "
                        + "blur(" + blurValue + ") "
                        + "brightness(" + brightnessValue + ") "
                        + "saturate(" + saturateValue + ") "
                        + "contrast(" + contrastValue + ") "
                        + "sepia(" + sepiaValue + ")";
        // set `img` `filter` to `filterVal`
        $(img)
        .css({
            "webkit-filter": filterVal,
            "moz-filter": filterVal,
            "ms-filter": filterVal,
            "o-filter": filterVal
        });
        function downloadCanvas(link, canvas, filename) {
            link.href = document.getElementsByTagName(canvas)[0].toDataURL();
            link.download = filename;
        }

        document.getElementById('download').addEventListener('click', function () {
            html2canvas(document.body, {
                onrendered: function (canvas) {
                    var image = canvas.toDataURL("image/png").replace("image/png", "image/octet-stream"); //Convert image to 'octet-stream' (Just a download, really)
                    window.location.href = image;
                }
            });

        }, false);
});