Your own VST plugin. Need a custom piano roll. Where to begin?

Question

MIDI

For the most part interested in the work of MIDI (notes).
1. By holding down a key (midi keyboard) you need to display a picture.
2. When playing a midi track, also display a photo.
I want to program a picture output for each key when playing.
Simply put, make a custom piano roll
. Advise in which direction to dig. Perhaps there are ready-made libs for working with midi
I would be grateful for any links.
I will mark everyone with the decision (as part of this issue)

Answer 1

What are the technical requirements (OS, host application, use case)?