Check out SSCD from Meta https://github.com/facebookresearch/sscd-copy-detection

(full disclosure: I am an employee who has worked with this team before internally, but I was not associated with this paper)

perceptual hashing is one approach to image similarity, there are many others. The au courant way of doing ANN search is to use embeddings from the powerful pre-trained models. In this tool the creator uses OpenAI's CLIP.

TIL of "au courant".

the author mentions CLIP, but it looks like he made his own variant. i wish i knew what it was since it seems he is now AWOL

Look at the papers of Andrew Zhai (Pinterest) and how they do it.