To interface between the one-dimensional scanning of an image, and the applications of a two-dimensional operator, an intermediate storage is required. For a square image of size n2, and a square operator of size m2, the minimum intermediate storage is shown to be n .(m-1). An interface of this size can be conveniently realized by using a serpentine delay line. New kinds of imagers would be required to reduce the size of the intermediate storage below n.(m-1).