Error Analysis of Ellipse Fitting for Incomplete Contour

Abstract

In computer image processing, owing to the influence of lighting conditions and camera installation locations, incomplete ellipse contour extraction often occurs after the edge extraction of the image. By fitting this residual contour, the result deviates from the original elliptical shape and the fitting error is large, which affects the fitting accuracy. The degree of influence of the characteristics of the incomplete contour on the error was studied, and a numerical simulation method in MATLAB was used to perform incomplete elliptical arc segments at different positions, edge extraction on the arc segment, and ellipse fitting on the arc segment based on the least squares method. The influence of multiple factors, such as the phase angle, the arc length integrity, and the axis ratio of the ellipse on the ellipse fitting error was analyzed, which was significant in understanding the causes of error generation and improving the fitting accuracy. The curves of the fitting error with the three factors yield that all three factors have a significant effect on the fitting error. The effect of contour fitting at different phase angles varies greatly, and the greater the arc length integrity and the smaller the axis ratio of the ellipse, the smaller the fitting error.

Keywords

simulation method / least squares method / ellipse fitting / fitting error

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Funding

National Key Research and Development Program of China(2017YFB1304001)