Thanks to Wiebke Dittmer again. Here's a 1950 photograph by Dmitri Kessel:
and here's another Bob Dylan painting from the Asia Series:
The most striking thing is that Dylan has not merely used a photograph to inspire a painting: he has taken the photographer's shot composition and copied it exactly. He hasn't painted the group from any kind of different angle, or changed what he puts along the top edge, or either side edge, or the bottom edge of the picture. He's replicated everything as closely as possible. That may be a (very self-enriching) game he's playing with his followers, but it's not a very imaginative approach to painting. It may not be plagiarism but it's surely copying rather a lot.