Raving mad is quite easy. You just chew up the scenery or something. It's quiet mad that's hard.
The painter sees the semblance of things and repeats it. That is, without fabricating the things himself, he fabricates their semblance; and, if that no longer recalls any object, this artificially produced semblance functions only because it is scrutinized for likeness to a familiar - that is, object-related - semblance.