DOCUMENT IMAGE SKEW DETECTION: SURVEY AND ANNOTATED BIBLIOGRAPHY
Jonathan J. Hull · Series in machine perception and artificial intelligence · 1998
Algorithms that estimate the angle at which a document image is rotated (called a document’s skew) are surveyed. Four broad classes of technique are identified. These include methods that calculate skew from a horizontal projection profile, a distribution of feature locations, a Hough transform, or the distribution of responses from local, directionally sensitive masks. The basic method used by each class of technique is presented and the contributions of individual algorithms within each class are discussed. 1