you could do in this approach is just take your test data point and compare it to each of the the data points in your training data basically do nearest neighbors by by comparing to each of the images the this is a quite a simple opportunity quite valid for these types of problems the key question is in what space do you compare these images and with what distance metric I for example you could do pixel space or l2 distance but that probably wouldn't give you an effective metric over the similarity between these