GIMP has a feature built-in called Python-Fu, and you can automate processes with it.

Bonus: Using scripts for advanced batch processing If you need more advanced batch processing options, GIMP supports scripting through languages like Python and Script-Fu.

I think this is the right forum, since it is a gimp question more than a programming question.I simply need to batch convert a large number (1k+) of JPG images (all same size) to grey scale XPM ...