I developed a little utility to massively manage overlays and other config files for RetroArch.
Current feature list:
It can detect the “viewport” area inside the overlay and generate RetroArch config files so that a game runs (almost) perfectly inside it.
It can resize overlays to the desired size keeping the aspect ratio.
The resize operation can be based on the full size of the overlay or the viewport, thus maximizing the game playable area and cropping “excess” overlay.
You can find it on GitHub. It’s a command line utility written in Python so it should easily running any system, provided you have Python 3.* installed.
It’s still very rough and I’d like to have feedback to fix and improve it.