1. A device readable medium, with instructions thereon, to cause an information-processing device to: generate a plurality of detail maps of a reference image at each of a plurality of resolutions, wherein the reference image detail maps represent changes between adjacent pixels; generate a plurality of detail maps of a scanned image at each of the plurality resolutions, wherein the scanned image is generated by scanning a print of the reference image, further wherein the scanned image detail maps represent changes between adjacent pixels; break each detail map into blocks of equal proportion; calculate an activity measure of each block in each detail map; measure similarities between respective detail map blocks to derive similarity maps; and combine the similarity maps into a single map of similarity measures, wherein a higher similarity measure indicates a higher probability of a print defect.