Threshold demo in OpenCV

Threshold test for
0: Binary
1: Binary Inverted
2: Threshold Truncated
3: Threshold to Zero
4: Threshold to Zero Inverted

...

#include "opencv2/opencv.hpp"
#include "opencv2/highgui.hpp"
#include "opencv2/cudaarithm.hpp"
#include <iostream>
#include <vector>

#ifdef _DEBUG               
#pragma comment(lib, "opencv_core331d.lib")       
#pragma comment(lib, "opencv_highgui331d.lib")    
#pragma comment(lib, "opencv_imgcodecs331d.lib")  
#pragma comment(lib, "opencv_objdetect331d.lib")  
#pragma comment(lib, "opencv_imgproc331d.lib")  
#pragma comment(lib, "opencv_videoio331d.lib")  
#pragma comment(lib, "opencv_cudaarithm331d.lib")  
#else       
#pragma comment(lib, "opencv_core331.lib")       
#pragma comment(lib, "opencv_highgui331.lib")    
#pragma comment(lib, "opencv_imgcodecs331.lib")    
#pragma comment(lib, "opencv_objdetect331.lib")  
#pragma comment(lib, "opencv_imgproc331.lib")  
#pragma comment(lib, "opencv_videoio331.lib")
#pragma comment(lib, "opencv_cudaarithm331.lib")
#endif        


using namespace std;
using namespace cv;


int threshold_value = 0;
int threshold_type = 3;;
int const max_value = 255;
int const max_type = 4;
int const max_BINARY_value = 255;

Mat src, src_gray, dst;
char* window_name = "Threshold Demo";

char* trackbar_type = "Type: \n 0: Binary \n 1: Binary Inverted \n 2: Truncate \n 3: To Zero \n 4: To Zero Inverted";
char* trackbar_value = "Value";

/// Function headers
void Threshold_Demo(int, void*);



void main()
{
    /// Load an image
    src = imread("blade.jpg", 1);

    /// Convert the image to Gray
    cvtColor(src, src_gray, CV_BGR2GRAY);

    /// Create a window to display results
    namedWindow(window_name, 0);
    resizeWindow(window_name, 500, 500);

    /// Create Trackbar to choose type of Threshold
    printf("%s", trackbar_type);
    createTrackbar(trackbar_type,
        window_name, &threshold_type,
        max_type, Threshold_Demo);

    createTrackbar(trackbar_value,
        window_name, &threshold_value,
        max_value, Threshold_Demo);

    /// Call the function to initialize
    Threshold_Demo(0, 0);

    //origin 
    namedWindow("origin", 0);
    imshow("origin", src);

    /// Wait until user finishes program
    while (true)
    {
        int c;
        c = waitKey(20);
        if ((char)c == 27)
        {
            break;
        }
    }

}


void Threshold_Demo(int, void*)
{
    // 0: Binary
    //1: Binary Inverted
    //2: Threshold Truncated
    //3: Threshold to Zero
    //4: Threshold to Zero Inverted


    threshold(src_gray, dst, threshold_value, max_BINARY_value, threshold_type);

    imshow(window_name, dst);
}

...