Finding duplicated photo

[Fulvio]

Dave Angel wrote:

> If your real problem is identifying a renamed file amongst thousands of
> others, why not just compare the metadata?  it'll be much faster.
> 
This was the primer situation, then to get into the dirt I tought something 
more sophisticated.
There was a program some year's back which was brilliant an fast to find 
similar pictures on several thousand of them.
Now I can't recall what was the program name and very interesting to do some 
of mine experiments.