You have created overlays in .png format, for your systems or your games, with transparency zone and you want to generate the configuration files? ARRM can do this for you.
Video Tutorial
Here's the procedure to follow :
If your overlays are system overlays you will need to name them the same as your systems (eg : 3do.png)
If your overlays are game overlays you will have to name them the same way as the rom file (eg : Ace of Aces (USA).png)