> ... when I use my memory of having seen someone else's copyrighted materials to produce my own wholly new but similar looking works.

That's called "non-literal" copyright infringement. Plaintiffs win on the claims and appeals courts uphold the judgments. (See, e.g., the "Blurred Lines" case. https://www.nbcnews.com/pop-culture/music/robin-thicke-pharr...).

A person could infringe the copyright in an original image if they painted their own version by hand. The AI is basically irrelevant.