A fast algorithm for maximum-minimum image filtering

This paper proposes a method for fast operation by software for a certain kind of filtering, e.g., maximum, minimum, logical sum and logical product, among the nonlinear filtering for the image. The computation time of the proposed filtering is independent of the filter size or the content of the image. The computation for an output for the two-dimensional gray-scale image can be completed by at most two times of 2-term operations. When the image to be processed is a binary image. Then, the computation time can be reduced by a factor of more than 20 by the actual measurement of the computation time for the whole image, compared to the case of the gray-scale image. In the proposed method, the ring-type buffer is connected in multistages, so that the computation can be executed without storing the whole image in the main memory. This property is suited to the largescale image filtering, as in the cases of a satellite image or drawn diagram. The proposed method is actually programmed. Using the gray-scale and binary images, the method is compared by experiment to the conventional method, and the high speed of the proposed method is verified.