Hi @ all
This function is really great!
Have a look to our german 3D-druck-community.de http://www.3d-druck-community.de/thread-404.html.
There I have posted some samples how it works. The best of all ist to create so easy writings . (the german word "Muster" ist not the same as the amerk.-english word, will say example i.e.) Only written with a marker on white paper, I took a picture (png), that's all.
Try out with pics high contrast, positv and negativ, light up well, you will find many solutions.
horst,w GER