Multistage Combined Ellipse and Line Detection

This paper describes an algorithm for the detection of ellipses and lines in image edge data. Connected edge pixels are transformed into polygonal approximations by a two stage algorithm. Then a second two stage algorithm replaces combinations of lines by ellipses if the ellipse fit is better. For each algorithm a combination of splitting and merging of the data is used to enable global and local constraints to fit different representations to the pixel data. All merging decisions use a significance measure to replace a number of representations by a single representation which removes the need for thresholds in the algorithms. The structure of the algorithm allows any particular representation to describe the data e.g. parabolae, splines, etc. instead of ellipses.