Yep, it's indeed a trivial idea. I'd say I probably seen it mentioned in the exp...

Yep, it's indeed a trivial idea. I'd say I probably seen it mentioned in the explanation of convnets: they compress the images more and more as you go deeper in the network (i.e. they extract the features).

Compression+decompression is basically what an autoencoder does. See https://en.wikipedia.org/wiki/Autoencoder .