printing png with ^GF command (C# app)


I'm writing small app which convert PDF files int PNG and then stuff it into ZPL. My printer is industrial ZE500, which is not accepting anything else then ZPL.

So far, I'm able to achieve this by converting PNG into hexadecimal and use it with ~DY command but when it comes to printing, it works slow. I want to send my bitmap using ^GF command, but example i have of working ^GF use non-hexadecimal representation which i can't figure out what it is (it looks like "...,mUFC8mT04:::8I0F30060E19F0FCI03..." )

When i try to use my hex with ^GF it shows something what looks like noise or snow.

What are, step by step, best methods to use png inside ^GF? or maybe png is not proper format for this? What exactly shoul i do with PNG file?