I don't and have never owned a Garmin device. All I've got is Basecamp on Windows.
I've got these files on my hard drive:
Laos_Map.img - 22MB
gmapsupp.img - 22MB (oddly, *exactly* the same filesize as the above)
Southeast_Asia.img - 490MB
These don't open in Basecamp and apps like MAPC2MAPC can't open them.
I'd like to take these maps and, at least,
1) get them to open on a desktop app like Basecamp, and ideally
2) convert and load them into an Android mapping app like OsmAnd (conversion into an .sqlitedb file or some other non-proprietary standard)
I'm completely unfamiliar with Garmin .img files, what the various files are, and how to use them. Are the maps this person has spent a decade making basically locked to Garmin devices?