Canvas dataURL to Blob

HTMLCanvasElement.prototype.toBlob = function(type) {
    var dataURL = this.toDataURL(type),
        binary = atob( dataURL.substr( dataURL.indexOf(',') + 1 ) ),
        i = binary.length,
        view = new Uint8Array(i);

    while (i--) {
        view[i] = binary.charCodeAt(i);
    }

    return new Blob([view]);
};