To clarify my use case: my app is an e-reader app focused on Biblical materials, with a cross-referencing system that can surface content from any downloaded books related to any verse or entity (people, places, things, ideas). There are lots of atlas-like resources with maps of the ancient near east in Biblical times, and it would be amazing to be able to select the name of a city on a map image and feed it into my existing functionality to find content related to that city name - verses, encyclopedia articles, etc.
[edit: this should have been a comment, but now I can't find a way to delete this "reply"]