Code to equalize a photograph in c++?

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

    using namespace cv;
    using namespace std;

    int main(int argc, char** argv)
    {

        Mat img = imread("../images/cat.jpg");
        if (img.empty())
        {
            cout << "Failed to open the image" << endl;
            return -1;
        }

        Mat ycrcb;
        cvtColor(img, ycrcb, COLOR_BGR2YCrCb);

        vector<Mat> channels;
        split(ycrcb, channels);

        equalizeHist(channels[0], channels[0]);

        Mat result;
        merge(channels, ycrcb);

        cvtColor(ycrcb, result, COLOR_YCrCb2BGR);

        imshow("image", img);
        imshow("result", result);

        waitKey();
        return 0;
    }