A method and apparatus incorporating a binary function correlation of run edges for compressing periodic halftoned digital images while increasing compression ratios over currently known one- and two-dimensional and adaptive arithmetic methods and decreasing the time required to perform the operation. In one embodiment, the invention horizontally encodes an image's run edges located at or near least &tgr; pixels ahead of a reference run edge in raster sequential image data. After the image is divided into lines of digital bits containing digital information indicative of binary values, the lines are encoded. A value for &tgr;—where &tgr; is independent of the width of the image and represents the periodicity for an edge of a run—is selected. Thereafter, run edges located &tgr;±n pixels ahead of a designated run edge of a reference run are encoded.