On Computing Histograms of Images in Log n Time Using Fat Pyramids.

Abstract : This paper presents an algorithm for the log n computation of the complete histogram of an n x n gray-level image. It uses a fat pyramid implemented on an SIMD hypercube multiprocessor with very high processor utilization. A fat pyramid is a pyramid in which the size of a processor associated with a node in the pyramid depends on the level of the pyramid in which the node appears. We describe how to embed fat pyramids in hypercubes using Gray codes, and then describe the histogramming algorithm. (Author)