To satisfy my curiosity, I succeeded in changing the hash value of an image I downloaded from a website merely by opening and then saving it with an image editor. I didn't have to modify any pixels at all.
That won't affect the software they're using.
If you're patient enough to try it, get the original indexed by TinEye.
Then reverse search your "modified" one. Then crop it and try again, then change some pixels and try again.
You will most likely find that TinEye correctly returns the original every time. When they say hashing, they don't mean filehashes.