1. A system comprising: at least one integrated circuit configured to: receive pixels of an image; divide the image into a plurality of blocks of pixels; determine numbers of islands within each of the plurality of blocks of pixels of the image, wherein determining a particular number of islands within a particular block of the plurality of blocks includes identifying at least one of a single dark pixel bordered by at least one of (i) a plurality of light pixels of the particular block and (ii) one or more edges of the particular block, or two or more contiguous dark pixels bordered by at least one of (i) a plurality of light pixels of the particular block and (ii) one or more edges of the particular block; determine categorizations of each of the plurality of blocks of pixels based on the numbers of islands within each of the plurality of blocks of pixels; and set, based at least on the categorizations of each of the plurality of blocks of pixels, filter indices for regions of the image, each of the regions including different subsets of the plurality of blocks of pixels; and filter based on the filter indices, the regions of the image.