Skew Correction for Scanned Japanese/English Document Images

摘要

Bit data is encoded into characters in an input image by providing different darkness levels for pixels in either half of a text character. In order to detect document skew angle error prior to attempting to extract an encoded message, the orientation angle of text line(s) in the input image is determined, and a document skew angle is estimated from the line orientation angle(s). A Hough transform may be used to estimate line orientation angle. To determine if an input image of a document is orientated horizontally or vertically, the input image may be scanned for text characters along a first reference angle, and along a second angle 90° to the first angle. The scan that provides the higher number of potential text character is selected as the correct orientation for the input image.