Patent ID: 7440618

Claim:
A ruled line extraction apparatus, comprising: an extraction device extracting from a page an area containing a pattern to be determined from a multiple-valued image; a determination device selecting each of a plurality of pixels in a contour portion of the area as a target pixel, selecting a first compared pixel in a direction vertical to the ruled line with respect to the target pixel, computing a first amount of the target pixel that is a gray level difference between the target pixel and the first compared pixel, computing an evaluation value based on the respective first amounts respectively computed for the plurality of pixels in the contour portion of the area, and determining, based on the evaluation value corresponding to a gray level change in a direction vertical to the tangent direction of the contour portion of the ruled line, whether the ruled line is written on a front side or a reverse side of the page in such a way that the area is determined to contain the ruled line written on the front side of the page if the evaluation value is equal to or larger than a predetermined value and the area is determined to contain the ruled line written on the reverse side of the page if the evaluation value is smaller than the predetermined value; and an output device outputting information about the area determined to contain the ruled line written on the front side of the page.