Store as Png Image from Signature pad?

i have implemented signature-pad and its working perfectly..!
now, I want to store the Signature as .png image to local/cloudinary.

$scope.saveCanvas = function() {
var sigImg = signaturePad.toDataURL('image/png');
$scope.signature = sigImg;
console.log("$scope.signature :",$scope.signature);
}

above code gives base64 string like :
data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAASwAAACWCAYAAABkW7XSAAAY

How can I convert the base64 into .png image?

i have asked on StackOverFlow also..?