说明：  otsu自适应阈值分割OTSU算法也称最大类间方差法，是图像分割里基于点的全局阈值选取方法中的一种，诞生于1978年，作者是Otsu。这种方法以其计算简单、稳定有效，一直广为使用，至今仍在matlab的图像处理工具箱里作为灰度图像单阈值自动选取的标准算法
(Otsu adaptive threshold segmentation algorithm OTSU also known Otsu method is based on the point of image segmentation in the global threshold selection methods, was born in 1978, the author is Otsu. This method of its calculation is simple, stable and efficient, has been widely used in still image processing toolbox matlab as a gray image is automatically selected a single threshold value of the standard algorithm)