Mutual NN Matcher (numpy)

mutual_nn_matcher.py

import numpy as np

def mutual_nn_matcher(descriptors1, descriptors2):
    descriptors1 = descriptors1 / np.linalg.norm(descriptors1, axis=1)[:, np.newaxis]
    descriptors2 = descriptors2 / np.linalg.norm(descriptors2, axis=1)[:, np.newaxis]
    similarity = descriptors1 @ descriptors2.transpose()
    nn12 = np.argmax(similarity, axis=1)
    nn21 = np.argmax(similarity, axis=0)
    ids1 = np.arange(similarity.shape[0])
    valid_matches = (ids1 == nn21[nn12])
    return np.vstack([
        ids1[valid_matches], nn12[valid_matches]
    ]).transpose()