ECC proxy to HCI: decode Base 64 encoded images in HCI

Hi Experts

I have a requirement where i will be getting below fields from the ECC proxy

Header 1..1
refnumber
Invoices 1..Unbounded
duedate
productcode
productimagefilename
Images 1..Unbounded
productimage

I have to create a txt or csv file from invoices fields and productimage(1...Unbounded) are Base64 encoded images that i need to decode in binary and then save both file and images in an SFTP folder.

What should be the approach for this...mapping level UDF for Base 64 decoding or base 64 decoder i can use from HCI pallate

Regards

naina