If you haven’t tried opening a .jpg or .bmp in Lulzbot’s free/ open source Cura printer management software, give it a try!
– Open Cura
– Click “Load Model”
– Select your picture file
– Select (usually) lighter is higher to get convex “selfies”.
– For “lithophanes”, “mirror” the image in X, (typically) select “darker is higher” to achieve a concave effect, flip the printed image over so the bed side is facing you, and backlight for a cool effect!
Other tips:
Light smoothing is usually good.
Scale the print uniformly to get the X or Y size you want, then unlock uniform scaling and reduce Z to 10mm or so.