Uploaded Image File Names Transliteration

I notice that uploaded images get renamed to all lowercase and hyphens are added where there were spaces. That’s fine but where is this controlled? I found the upload_translit setting but that mentions ‘global transliteration rules’. Where are those rules set?

I believe it uses the same settings as for friendly URLs.
So probably all the system setting that start with friendly_alias...

Thanks Harry - that seems an odd way of doing that though.