说明：  大津法（OTSU）是一种确定图像二值化分割阈值的算法，由日本学者大津于1979年提出。从大津法的原理上来讲，该方法又称作最大类间方差法，因为按照大津法求得的阈值进行图像二值化分割后，前景与背景图像的类间方差最大（何为类间方差？原理中有介绍）。
(Otsu method (OTSU) is a set of image binarization threshold segmentation algorithm, proposed by Japanese scholars ohtsu in 1979. From the principle of Otsu method speaking, this method is also called Otsu method, because in accordance with the Otsu binarization method of threshold image segmentation, foreground and background image (what is the maximum variance between class variance? The principle is introduced).)