A New Reptile Method for Contour Tracing Based on an Extended Freeman Code and an Alterable Window

The reptile method with an alterable window is often used to trace the contours for image recognition in machine vision. But sometimes a wrong result will be gotten if searching all the outermost pixels of the window. This paper proposes a new reptile method based on an extended Freeman code and an alterable window. In the method, the extended Freeman code is designed to determine the initial searching direction of a contour and the rule of filling breakpoints. In the course of tracing, the contour direction is used for reducing the searched pixels in the alterable window. The experimental results show the new method is superior to the traditional one.