QRcode generation base64 - BI Publisher

We are trying to implement QR code by using the function

<?qrcode: <DATA>; <SIZE>[; <CHARSET>]?> from Doc ID 2382839.1

The "DATA" in that function should be a JSON string in base64 format.

We are generating that JSON string by formatting variables in the RTF template.

Question is, is there a way to format that JSON string to base64 so we can then generate the QR code as well?