I thought that similar inputs do not give similar hashes..but apparently that is cryptographic hashing. Locality-Sensitive Hashing methods (e.g. Perceptual hashing[1]) makes similar inputs have similar hashes.
I immediately did a little exploration for potential utility in neuroimaging analyses...not that anything was immediately obvious to me, but I love learning about things like this.
[1] https://en.wikipedia.org/wiki/Perceptual_hashing