This (+ d3.js) is magic.

gistfile1.js

$('svg').each(function() {
    var XMLS = new XMLSerializer();
    var content = XMLS.serializeToString(this).trim();
    var parent = $(this).parent();
    var canvas = $('<canvas style="width: 400px; height: 200px;"/>')[0];
    parent.append(canvas);
    canvg(canvas, content);
    var theImage = canvas.toDataURL('image/png');
    $('svg, canvas', parent).hide();
    parent.append("<a href='"+theImage+"' download='chart.png'><img src='"+theImage+"' /></a>");
});