Image processing apparatus

An image processing apparatus, comprising:

• an edge image generating unit configured to detect edge pixels in an original image and generate an edge image that includes the detected edge pixels;
• a reduction processing unit configured to (a) set a reduction direction as one of a horizontal direction and a vertical direction, and (b) reduce the edge image along the reduction direction by a predetermined reduction ratio without reducing the original image along a direction perpendicular to the reduction direction and thereby generate a reduced image;
• a connecting pixel group detecting unit configured to detect a connecting pixel group in the reduced image, the connecting pixel group continuously extending along the reduction direction;
• and
• a ruled line determining unit configured to (a) associate two connecting pixel groups with each other as a connecting pixel group pair among connecting pixel groups detected in the reduced image, and (b) determine a position of a ruled line in the original image from a position of the connecting pixel group pair on the basis of the reduction ratio.