OpenCV图像的全局阈值二值化函数（OTSU）

cv::threshold(GrayImg, Bw, 0, 255, CV_THRESH_BINARY | CV_THRESH_OTSU);//灰度图像二值化

CV_THRESH_OTSU是提取图像最佳阈值算法。该方法在类间方差最大的情况下是最佳的，就图像的灰度值而言，OTSU给出最好的类间分离的阈值。

OpenCV阈值分割的几种方法（types_c.h中的定义):

/* Threshold types */
enum
{
    CV_THRESH_BINARY      =0,  /* value = value > threshold ? max_value : 0       */
    CV_THRESH_BINARY_INV  =1,  /* value = value > threshold ? 0 : max_value       */
    CV_THRESH_TRUNC       =2,  /* value = value > threshold ? threshold : value   */
    CV_THRESH_TOZERO      =3,  /* value = value > threshold ? value : 0           */
    CV_THRESH_TOZERO_INV  =4,  /* value = value > threshold ? 0 : value           */
    CV_THRESH_MASK        =7,
    CV_THRESH_OTSU        =8  /* use Otsu algorithm to choose the optimal threshold value;
                                 combine the flag with one of the above CV_THRESH_* values */
}