中文说明：基于像素点的全局阈值法求图像的分割实现方法有五种：最小极值法，最优阈值法，最大方差方法，最大熵法，迭代法
English Description：
There are five methods of image segmentation based on global threshold method: minimum extremum method, optimal threshold method, maximum variance method, maximum entropy method and iterative method