canvas保存为图片，兼容IE9+，chrome，Firefox

<title>javascript将canvas对象保存为图片示例</title>
<canvas id="c"></canvas><br />
<input type="button" value="保存canvas为图片" onclick="saveImg(c, 'save-canvas-to-image.png')" />
<script>
    var ct = c.getContext('2d');
    ct.fillRect(0, 0, 100, 100);
    var saveImg = function (canvas, filename) {//canvas保存为图片
        if (canvas.msToBlob) {//IE9+浏览器
            var blob = canvas.msToBlob();
            window.navigator.msSaveBlob(blob, filename);
        } else {//firefox,chrome
            var save_link = document.createElementNS('http://www.w3.org/1999/xhtml', 'a');
            save_link.href = canvas.toDataURL('image/png');
            save_link.download = filename;
            var event = document.createEvent('MouseEvents');
            event.initMouseEvent('click', true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
            save_link.dispatchEvent(event);
        }
    };
   
</script>