Line segment detector and line segment detecting method

摘要

A line segment detector comprises a vertical line detecting part, a horizontal line detecting part, a left-to-right downward slanting line detecting part, a left-to-right upward slanting line detecting part, and a line-segment detecting/synthesizing section that calculates OR operation of output values from the vertical line detecting part, the horizontal line detecting part, the left-to-right downward slanting line detecting part, and the left-to-right upward slanting line detecting part. The line segment detector further comprises a re-determining unit comprising a second line-segment detecting part that sets a window to the detection result near the target pixel, counts the number of pixels whose detection result is determined as the line segment in the set window, determines, when the counted value is not smaller than a predetermined threshold value, that the pixel is a line segment.