Mat temp_1_mat,temp_2_mat,temp_3_mat;

    temp_1_mat = imread("./img_1.jpg",CV_LOAD_IMAGE_COLOR);
    imwrite("temp_1_mat_before.jpg", temp_1_mat);
    //temp_2_mat = cv::Mat::zeros(cv::Size(temp_1_mat.rows, temp_1_mat.cols), CV_8UC3);
    try {
        std::cout << "cvtColor being\n";
        std::cout << "rows = " << temp_1_mat.rows << std::endl;
        std::cout << "cols = " << temp_1_mat.cols << std::endl;
        std::cout << "channels = " << temp_1_mat.channels() << std::endl;
        cv::cvtColor(temp_1_mat, temp_2_mat, CV_BGR2GRAY);
        imwrite("temp_1_mat_after.jpg", temp_1_mat);
        imwrite("temp_2_mat_1.jpg", temp_2_mat);
        cv::cvtColor(temp_1_mat, temp_2_mat, CV_BGR2GRAY);
        imwrite("temp_2_mat_2.jpg", temp_2_mat);
        std::cout << "cvtColor end\n";
    } catch (const std::exception& e) {
        std::cout << "CVTCOLOR EXCEPTION :: " << e.what() << std::endl;
    }