利用水平集函数来检测物体轮廓，一般水平集收敛用到signed distance function的，但是这里实现的程序不用每次都要进行reinitialization就可以使水平集函数趋于收敛。-The use of level set function to detect an object contour, the general level set signed distance function used in the convergence, but the program here do not realize every time to be able to make the level set reinitialization functions tend to converge.