I wouldn't be too sure. On the one hand, US Copyright is very explicitly attached to a piece of work, not the facts or ideas contained in it. Per 17 USC 102: >

I wouldn't be too sure. On the one hand, US Copyright is very explicitly attached to a piece of work, not the facts or ideas contained in it. Per 17 USC 102: > In no case does copyright protection for an original work > of authorship extend to any idea, procedure, process, > system, method of operation, concept, principle, or > discovery, regardless of the form in which it is described, > explained, illustrated, or embodied in such work. You are therefore free to create works of your own that analyze facts contained in others' copyrighted works, comment on their ideas, and so on. This is always true if you don't include any of their copyrighted work, and often true, via fair use, if you only include the small pieces needed for your commentary. Accordingly, it seems pretty clear that you could analyze a huge collection of copyrighted portraits and do whatever you want with the results (distribution of hair colors, eye positions relative to nose, how these vary within/across individuals, and so on). The counterargument would appear to be that derivative works include the "abridgment, condensation, or any other form in which a work may be recast, transformed, or adapted." Neural networks do seem to store their training data, at least in some form, and there's a fuzzy line between extracting some facts from data (which is fine) and omitting data to create an abridged version (which isn't). I wouldn't want to bet much either way, but I do think it would be a little odd for copyright to limit how much you can "learn" from something, either manually or via machine.