I hope some day this will generalize to video. I don't care about the exact shape of background trees in an action movie - with this approach, they could be compressed to just a few bytes, regardless of resolution.
This would of course not give you any space savings when you want to distribute 1 movie. There would be some minimum number of movies where the training set + actual movies would be smaller than the sum of the sizes of the individual movies compressed.
I'm not saying this would be a net space saver, or necessarily a good technique at all, but the concept is intriguing.