Create a Blob from a Base64 string

Question

I am unsuccessfully trying to create a blob from an base64 string.

The variable base64 has an image(encoded in base64).

var blob = new Blob([window.atob(base64)], {type : 'image/png'});
var url = URL.createObjectURL(blob);

I have created the following jsfiddle as well

http://jsfiddle.net/83PQs/6/