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

using namespace cv;
using namespace std;

int main()
{
    Mat original = imread("res.jpg",0);//0 because we need a grayscale image by default
    Mat modified;
    threshold(original, modified,200 ,255, CV_8UC1);//this is called a threshold function //8UC1 means single channel grey scale image(200 for center and 255 for outer circle)
    float sumx=0, sumy=0;
    float num_pixel = 0;
    for(int x=0; x<modified.cols; x++) {
        for(int y=0; y<modified.rows; y++) {
            int val = modified.at<uchar>(y,x);// a single channel grey scale image (type 8UC1) and pixel coordinates x and y
            if( val>0) {//after thresholding,the picture will become black and white. Therefore,we will easily identify the white pixels(255) with the black pixels(0)

                sumx += x;
                sumy += y;
                num_pixel++;
            }
        }
    }
    Point p(sumx/num_pixel, sumy/num_pixel);

    Moments m = moments(modified, false);
    Point p1(m.m10/m.m00, m.m01/m.m00);
    cout << Mat(p1) << endl;

    circle(modified, p, 5, Scalar(128,0,0), -1); //5 is the size of the centroid to be displayed //Scalar(red,green,blue)

    namedWindow("before",WINDOW_NORMAL);
    imshow("before",original);
    namedWindow("after",WINDOW_NORMAL);
    imshow("after", modified);
    waitKey(0);
    return 0;
}