(OpenCV Study) setMouseCallback function example source code, get rectangle coordinate of mouse drag on image.

This  source code is useful when you need retangle coordinate of mouse drag.
The rectangle coordinate is applied initial region for tracking.

refer to video and source code.

#include < stdio.h>
#include < iostream>

#include < opencv2\opencv.hpp>
//#include < opencv2/core/core.hpp>
//#include < opencv2/highgui/highgui.hpp>
//#include < opencv2/video/background_segm.hpp>
//#include < opencv2\gpu\gpu.hpp>
//#include < opencv2\legacy\legacy.hpp>

#ifdef _DEBUG        
#pragma comment(lib, "opencv_core247d.lib")
//#pragma comment(lib, "opencv_imgproc247d.lib")   //MAT processing
//#pragma comment(lib, "opencv_objdetect247d.lib") //HOGDescriptor
//#pragma comment(lib, "opencv_gpu247d.lib")
//#pragma comment(lib, "opencv_features2d247d.lib")
#pragma comment(lib, "opencv_highgui247d.lib")
//#pragma comment(lib, "opencv_ml247d.lib")
//#pragma comment(lib, "opencv_stitching247d.lib");
//#pragma comment(lib, "opencv_nonfree247d.lib");
//#pragma comment(lib, "opencv_video247d.lib")
//#pragma comment(lib, "opencv_legacy247d.lib")
#else
#pragma comment(lib, "opencv_core247.lib")
//#pragma comment(lib, "opencv_imgproc247.lib")
//#pragma comment(lib, "opencv_objdetect247.lib")
//#pragma comment(lib, "opencv_gpu247.lib")
//#pragma comment(lib, "opencv_features2d247.lib")
#pragma comment(lib, "opencv_highgui247.lib")
//#pragma comment(lib, "opencv_ml247.lib")
//#pragma comment(lib, "opencv_stitching247.lib");
//#pragma comment(lib, "opencv_nonfree247.lib");
//#pragma comment(lib, "opencv_video247.lib")
//#pragma comment(lib, "opencv_legacy247.lib")
#endif 

using namespace std;
using namespace cv;

bool selectObject = false;
Rect selection;
Point origin;
int trackObject = 0;
Mat image;


static void onMouse( int event, int x, int y, int, void* )
{
    if( selectObject )
    {
        selection.x = MIN(x, origin.x);
        selection.y = MIN(y, origin.y);
        selection.width = std::abs(x - origin.x);
        selection.height = std::abs(y - origin.y);

        selection &= Rect(0, 0, image.cols, image.rows);
    }

    switch( event )
    {
    case CV_EVENT_LBUTTONDOWN:
        origin = Point(x,y);
        selection = Rect(x,y,0,0);
        selectObject = true;
        break;
    case CV_EVENT_LBUTTONUP:
        selectObject = false;
        if( selection.width > 0 && selection.height > 0 )
            trackObject = -1;
        break;
    }
}


int main (void)  
{  
 

 VideoCapture cap(0);
 Mat frame;
 namedWindow( "Demo", 0 );
 setMouseCallback( "Demo", onMouse, 0 );

    for(;;)
    {
        
  cap >> frame;
        if( frame.empty() )
   break;

        frame.copyTo(image);
  

  if( selectObject && selection.width > 0 && selection.height > 0 )
        {
            Mat roi(image, selection);
            bitwise_not(roi, roi);
   printf("%d %d %d %d\n", selection.x, selection.y, selection.width, selection.height);
        }

  imshow( "Demo", image );

  if( waitKey(10) > 10 )
   break;
 }

 return 0;  
}