Method and apparatus for document skew and size/shape detection

Abstract

The present invention relates in general to optical scanning and image processing, and relates more particularly to a document imaging system which detects skew and/or detects size/shape of a document image. Preferred embodiments utilize a background with optical characteristics which contrast with those of the scanned document. In one embodiment, a document imaging system generates scanning signals in response to optical characteristics of a medium such as a sheet of paper, detects transitions in the scanning signal which define points along one or more edges of the medium, establishes a skew angle between the detected edges and a reference orientation, and compensates for skew by modifying the scanning signals as required such that the resultant skew angle is substantially equal to zero. In another embodiment, a document imaging system detects one or more edges of a document, defines a polygon having sides substantially congruent with the detected edges, and establishes the size of the document in response to the polygon.