Algorithm for extracting ellipses using weighted center points map
Junji Yamato, Ikuo Ishii, Hideo Makino, Kazuyoshi Irisawa · Systems and Computers in Japan · 1990
Abstract When a group of parallel lines pass through an ellipse, the center point between two intersecting points of each straight line is on another straight line passing through the center of the ellipse. Furthermore, a graphical plot of the distance between the two intersecting points vs. a coordinate value (either x or y) of the center point will form an elliptical shape. These two characteristics of the ellipse are exploited by an algorithm for ellipse extraction. Given an input image of ellipses, a center point map is constructed. Then a Hough transform is used to detect the center line that represents the ellipse. Next, the center line so detected is used to estimate the parameters and to obtain sample pixels of the ellipse. This is followed by a least‐square fitting and high precision parameter value computation. Numerous experiments were conducted which demonstrated the effectiveness of our algorithm.