判断分析法从图象灰度直方图中把灰度值的集合用阀值 T分成两类，然后根据两个类的均值方差(类间方差)和各类的方差(类内方差)的比为最大来确定阀值。-Analysis to determine from the image histogram of the gray value threshold with the set T into two categories, and then based on two types of mean-variance (between-class varian