Fast median filtering algorithms for mesh computers

Two fast algorithms for median filtering of images using parallel computers having 2-D mesh interconnections are given. Both algorithms assume that an n x n image is loaded onto the mesh with one processing element per pixel. One algorithm performs median filtering over d x d neighborhoods in O(d(2)) time and works with pixel values in an arbitrarily large range. This algorithm, while theoretically suboptimal, achieves a lower constant than a previously published asymptotically-optimal algorithm and is simpler to program. The second algorithm assumes that the range of pixel values is limited and relatively small, and it accomplishes median filtering in O(d) time.