A computer-implemented method includes receiving a set of basis fingerprints corresponding to image chunks within a basis set of image regions wherein each image region within the basis set of image regions comprises one or more image chunks, and generating a fingerprint for each image chunk of a plurality of selected image chunks within an unprocessed region of a machine image to produce a plurality of sampled fingerprints. The method also includes determining a similarity metric for the unprocessed region from the sampled fingerprints and the basis fingerprints, comparing the similarity metric for the unprocessed region with a selected threshold, and including the unprocessed region within the basis set of image regions in response to determining that the similarity metric is less than the selected threshold. A corresponding computer program product and computer system are also disclosed herein.