1. A machine-implemented image processing method, comprising: computing a first set of pixel neighborhood values (PNVs) from respective sets of pixel values of a first image corresponding to different spatially-shifted pixel neighborhoods each encompassing a mutual target pixel in the first image; computing a second set of PNVs from respective sets of pixel values of a second image corresponding to different spatially-shifted pixel neighborhoods each encompassing a mutual target pixel in the second image; computing a measure of dissimilarity based at least in part on the first and second sets of computed PNVs; and storing the computed dissimilarity measure on a machine-readable medium.