Yes, it is doable. Steep learning curve if you need to learn both Python and Gimp scripting. Some hints:
- Use os.walk(topdir) to list the contents of the top directories. This produces sperat lists of directories and files
- All the API documentation is available via Filters>Python-fu>Console>Browse.... It is dynamically generated, you'll even see your black-to-alpha plugin there.
- The Python-specific bit of the API (using Python ibjects instead of the PDB calls) is documented here: http://www.gimp.org/docs/python/index.html
- Load the files with layer=pdb.gimp_file_load_layer(image, filename). Once loaded you have to explicitly add the layer to the image (image.add_layer(layer,pos), pos=0 for the top of the stack, pos=len(image.layers) for the bottom).
- You can make a special case and load the first file with image=pdb.gimp_file_load(filename,filename) to create the image.
- Try to get at least the file walk working by using Python outside of Gimp (you can run the python executable that comes with Gimp in a terminal/console, it is much easier to debug that way, but this is only possible for code that doesn't interact with Gimp).
- To debug under Gimp, several hints there: https://www.gimp-forum.net/Thread-Debugg...in-Windows
- As long as you don't change the registration data, you can modify the script file and execute the new version without needing to restart Gimp.