I'll wear that; I'd heard of Lightroom in the context of Lua, but I've never used it and don't know what it's for. Looks like its plugin architecture is a major selling point? Seems like a great fit for Lua.

The UI widget toolkit and the low-level image processing code are in C++ but the people involved have said that the remaining half of the application is written in Lua. Nothing to do with plugins, really.

Cool! I'd be curious how large the codebase is, but it's cool to hear that something like Lightroom exists at all.

Given that it's made by the people who created a printable document format that supports embedded videos, I'm going to assume that it's an alarming large codebase.

The name PDF stands for portable document format (the name itself isn't that relevant, but also the intention).