说明：  类间方差阈值分割是在最小二乘法原理基础上推导出来的,其基本思路是将直方图在某一阈值处理分割成两组,当被分成的两组的方差为最大时,决定阈值。
(Otsu threshold segmentation is based on the principle of least square method derived, and its basic idea is to be a threshold in the histogram is separated into two groups of treatment, when the two groups were divided into the variance was the largest, the decision thresholds.)