Constant-Work-Space Image Scan with a Given Angle

In this paper we present a linear-time constant-memory algorithm for scanning a rotated grid image. The algorithm transforms the grid data into a stream data where the pixels are output in the increasing order of the distances to the line y=ax giving the rotated axis. We first deal with the special case where the slope a of the rotated axis is a quotient number of two small integers, then extend the method to the general case where the slope is an arbitrary real number.