Detecting Ellipses in Elongated Shapes Using the Thickness Profile

This paper presents a method that detects elliptical parts of a given elongated shape. For this purpose, first, the shape is represented by its skeleton. In case of branches, the skeleton is partitioned into a set of lines/curves. Second, the ellipse parameters are estimated using the thickness profile along each line/curve, and the properties of its first and second derivatives. The proposed method requires no prior information about the model, number of ellipses and their parameter values. The detected ellipses are then used in our second proposed approach for ellipse-based shape description. It can be applied for analysing motion and deformation of biological objects like roots, worms, and diatoms.