Document image inclination detection method and apparatus

摘要

PURPOSE:To detect the tilt of a document picture in a stable and easy way by detecting the direction where the projection, i.e, the width of the black picture element showing a character row and a table frame when the character row and a table, etc., are projected in the tilt direction. CONSTITUTION:A pattern memory 1 stores the document pictures as the quantized picture information. A binary projection information extracting part 2 sets (m) pieces of partial information (i) of a fixed size in the prescribed direction, scans each partial area (i), and extracts the binary projection information showing the presence/absence of black picture elements on each scan line to store them in sequence into a binary projection information storage part 3. Then the adjacent binary projection information are shifted in steps in the vertical and horizontal shift direction by a prescribed extent and read out. At the same time, an OR is obtained among plural binary projections and the cumulative binary projection information are extracted. Then the shift value is changed for detection of the shift value and the shift direction where the number of black picture elements of the cumulative binary projection information is minimized. Thus the tilt of a document picture can be detected in an easy and stable way.