PSNR

#include<opencv2/opencv.hpp>
#include<iostream>

using namespace std;
using namespace cv;

int main(){
    Mat src = imread("1.jpg",0);
	if (!src.data){
		std::cout << "no image input!!!" << std::endl;
		return -1;
	}    
	Scalar mean, stddev;
	meanStdDev(src, mean, stddev);
	double psnr = 20 * log10(255 / stddev.val[0]);
	cout << "======" << psnr << endl;

    return 0;
}