again, to achieve what ? please explain
at least, make a short exp., and try to detect kps in your patches – if you cant find any, you already have a hint, that this is a bad idea (10x10 might also be too small to get a single kp/desc, iirc, there’s a minimal patch size, but idk for SIFT)
also be aware, that compute() may reject ‘bad’ kp’s, so you may end up with less or even zero descriptors here !