<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>js_canvas_download</title>
<script type='text/javascript' src='http://cdn.staticfile.org/jquery/2.1.1/jquery.min.js'></script>
<script type="text/javascript" src="http://cdn.staticfile.org/jquery.qrcode/1.0/jquery.qrcode.min.js"></script>
</head>
<body>
<div id="qrcode"></div>
<a id="download" download="qrcode.jpg"></a>
<button id="save">save</button>
</body>
</html>
<script>
jQuery('#qrcode').qrcode({ 500,height: 500,text: "http://www.baidu.com"});
$("#save").click(function(){
var canvas = $('#qrcode').find("canvas").get(0);
var url = canvas.toDataURL('image/jpeg');
$("#download").attr('href', url).get(0).click();
return false;
});
</script>