There are some programs that allow for exporting STL CAD files used in 3D printing as simple PNG images - in so called slices. What this does, is basically slice the 3D model of the part and save each slice as a PNG image. It should be default function in CAD programs, but you can also probably find some 3rd party utilities or scripts designed exactly for this job.
Open STL file Open PNG fileA 3D CAD translation software