Merge cropping-resistant hash from imagehash

[JohannesBuchner]

Hi all,

I just found out about thorn. Very happy that you open-source your code as well.

We just had a collaborator merge a PR implementing a efficient cropping-resistant image hash. Perhaps you also would like to pick it up?

You can find it in the latest imagehash release (4.2) at https://github.com/JohannesBuchner/imagehash/

[BradKML]

Seconding this, bud. Would like to help.

[faustomorales]

Thanks so much for raising! A PR with an ImageHasher subclass implementing this algorithm would be more than welcome. Otherwise, okay to leave this issue open for when there's time available for implementation.