opencv求平均值，方差

opencv求平均值，方差

    cv::Mat   img = (cv::Mat_<float>(3, 1) << 7, 8, 9);  
    cv::Scalar     mean;  
    cv::Scalar     dev;  

    cv::meanStdDev ( img, mean, dev );  
    float       m = mean.val[0];  
    float       s = dev.val[0];  
    std::cout << m << ",\t" << s; 

    cv::Mat   img = (cv::Mat_<uchar>(3, 1) << 7, 8, 9);  
    cv::Scalar     mean;  
    cv::Scalar     dev;  

    cv::meanStdDev ( img, mean, dev );  
    float       m = mean.val[0];  
    float       s = dev.val[0];  
    std::cout << m << ",\t" << s;