SKEW DETECTOR FOR DIGITAL IMAGE PROCESSING SYSTEM

Each line in a frame of video data is organized into continuous runs of white pixels, and those runs having lengths below a given threshold are transformed to black pixels. The data is then organized into runs of black pixels, and the start position of the longest black pixel run is noted for each horizontal line. Skew angle is computed from the offset distance between the noted black run start positions of successive lines. The offset angle is computed from the mean of a set of offset distances, the set being large enough to minimize the RMS standard deviation of offset distances below a predetermined value. The set of successive black runs fall in a staircase pattern whenever there is a non-zero skew angle.