I unsure that printer is able to dither and then print a colored image. Seems image needs get dithered before sending to a printer.
Also it may worth to switch from EPL to ZPL as more advanced language.
Also I unsure you can embed Zebra Designer application into your application. Moreover, I unsure you need to do it.
Zebra Designer typically is used to create a label design that can contain graphic fields. And then one can send resulted ZPL code of label with all respective respective field values to a printer via Link-OS SDK or via direct communication.
You can use this response as example on how images can be printed and how to dither them without Zebra Designer:
Here you can find details on ^GF ZPL command:
Software Engineer, Kutir Mobility
Posted on behalf of Zebra Technologies