Printing the pixel coordinates of the mouse pointer on the image while hovering on it using OpenCV

Question

#include <iostream>
#include <stdio.h>
#include <opencv2/opencv.hpp>
#include <highgui.h>

using namespace cv;
using namespace std;

Mat image;
char window_name[20]="Get coordinates";

static void onMouse( int event, int x, int y, int f, void* ){
    cout << x << " " << y << endl;
    //putText(image, "point", Point(x,y), CV_FONT_HERSHEY_PLAIN, 1.0, CV_RGB(255,0,0));
}

int main() {
    namedWindow( window_name, CV_WINDOW_AUTOSIZE );
    image = imread("image.png");
    imshow( window_name, image );    
    setMouseCallback( window_name, onMouse, 0 );
    waitKey(0);
    return 0;
}

This is the code that prints the value of coordinates of the mouse pointer, while hovering on the image, on the console. If I wish to print the coordinates similarly on the image, how am I supposed to do it ?

Answer 1

#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <stdio.h>

using namespace cv;

Mat img;

void onMouse(int event, int x, int y, int flags, void* param)
{
    char text[100];
    Mat img2, img3;

    img2 = img.clone();

    if (event == CV_EVENT_LBUTTONDOWN)
    {
        Vec3b p = img2.at<Vec3b>(y,x);
        sprintf(text, "R=%d, G=%d, B=%d", p[2], p[1], p[0]);
    }
    else if (event == CV_EVENT_RBUTTONDOWN)
    {
        cvtColor(img, img3, CV_BGR2HSV);
        Vec3b p = img3.at<Vec3b>(y,x);
        sprintf(text, "H=%d, S=%d, V=%d", p[0], p[1], p[2]);
    }
    else
        sprintf(text, "x=%d, y=%d", x, y);

    putText(img2, text, Point(5,15), FONT_HERSHEY_PLAIN, 1.0, CV_RGB(0,255,0));
    imshow("image", img2);
}

int main(int argc, char** argv)
{
    img = imread(argc == 2 ? argv[1] : "lena.jpg");
    if (img.empty())
        return -1;

    namedWindow("image");
    setMouseCallback("image", onMouse, 0);
    imshow("image", img);
    waitKey(0);

    return 0;
}

Shall do the work..