| 摘要 |
PURPOSE:To extremely increase the processing speed for detection of an image tilt angle by detecting each side of a circumscribed tetragon enclosing the document part of an input original with linear approximation and obtaining the angle between said straight line and the contour of an image so that the tilt can be detected just with partial image data. CONSTITUTION:A distance up to a first black picture element is detected for each line in the entire area of the subscanning direction from the left side LL of an image in the main scanning direction. Thus a black picture element A is obtained. Then the average distance Ay from the side LL is obtained for all subject picture elements and a regression straight line (y) is obtained for linear approximation by the minimum square method only for the black picture elements within a range of a fixed value My set on the basis of the distance Ay. Thus the left side 1' of a character string part is subjected to the linear approximation. Then approximate straight lines are obtained as the right side 2', upper side 3' and lower side 4' of the character string part from the right side RL, upper side UL and lower side DL of the image in the same procedure. Thus a tetragon circumscribed to the character string part is obtained. This tetragon is moved horizontally. Thus the angles formed among the sides 1'-4' and the main scanning and subscanning directions are obtained as the tilt angles thetaof the picture.
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