Snake 算法或Active Contour Models。这类算法需要给出初始的轮廓，然后进行迭代，使轮廓沿能量降低的方向靠近，最后得到一个优化的边界。-Snake algorithm or Active Contour Models. Such algorithms need to give the initial profile, and then proceed to iteration, so that contours along the direction of lower en