How do I translate data to a spinning axis?

I've been using linuxcnc for years as a standard 3-axis x,y,z controller with good success. Recently I found a youtube video where someone claims to use linuxcnc to raster a laser image, spinning a laser on a stepper motor to burn image to a uv-emulsion pcb.

spinning laser axis

Obviously, this setup does not use standard g-code for positioning gantry x,y,z. I would like to build one of these for myself, I was wondering if anyone knew how it was done. I can write my own visual basic code to translate a bitmap image, and output data in anyway possible. But I don't know how I would start going about to to translate the data into something I would use Linuxcnc to drive the system. Please advise.