RGB图片取大于阈值部分

 #include<opencv2\opencv.hpp>
 #include <iostream>
 using namespace cv;
 using namespace std;
 int main()
 {

     //int threshval = 100;
     Mat img = imread("33.jpg");
     img = img >;
     namedWindow("Img", );
     imshow("Img", img);
     waitKey();
     return ;
 }