Automatic similar image detection

[russss]

It would be great to automatically group similar images. Recent ISS missions have got especially good at taking dozens of photos of the same subject, and this is especially tedious if you're rating images.

We might be able to do this simply by looking at the photo timestamp, and I'd suggest this might be the most useful first step.

ImgHash could be worth a look, but I'm a bit concerned about how well it'll work with our images.