How do I automatically generate thumbnails for every file in a particular directory and all its subdirectories?

[inhahe]

The "The markup" section of https://github.com/sachinchoolur/lightGallery seems to indicate that you have to make an index file that already has links to every image/video you want lightGallery to index. I don't want to do that, because I'd have to make a program to index every file in all the subdirectories (and I'm not even sure if subdirectories would work right that way?).

I want to just run lightGallery on a particular directory and have it detect all the files in that directory and all subdirectories by itself and then make thumbnails in separate categories for each subdirectory. I could have sworn I did this before, years ago, but I have no idea how I did it. Is there a way?

[inhahe]

I found out how I did it before. With https://github.com/thumbsup/thumbsup. It doesn't mention lightgallery anywhere in the docs, but the resulting directory structure has lightgallery directories so I guess it uses it.