1. A method comprising: determining a set of candidate keypoints based on a first image captured with a camera; determining, for each candidate keypoint in the set of candidate keypoints, a corresponding first similarity score, wherein the first similarity score corresponding to each candidate keypoint is determined, in part, by comparing an image patch associated with the corresponding candidate keypoint to a plurality of corresponding image sections in a region around the image patch; and selecting a first subset of the candidate keypoints, wherein the first subset comprises a predefined number of candidate keypoints with lowest similarity scores.