Earlier quoted context omitted.
>How will you be aware of it? And what prevents someone from tweaking one pixel by one bit, changing the hash of the new image? I suspect this would be solved by visually comparing the two images and noticing that they are one in the same. Than you can just see which had their hash published on the block-chain first to see which is the real one.
Yes, but if you can identify an image in that way then you can claim the copyright anyway. Searching for copyright violation is the challenge.
Just identifying the images are the same doesn't prove which was the original though. The hashes being publicly available is the key, because you can easily tell which came first.