errors occuring while compiling the code for histogram equalization : <p>I'm trying to implement my own Histogram equalization without using the library routine for histogram equalization in opencv c++ 2.4.13.2 version.
I compiled the program in terminal as follows:</p>

<pre><code>g++ `pkg-config --cflags opencv` histogram_Equalization.cpp `pkg-config --libs opencv` -o histeq
</code></pre>

<p>i'm getting the errors as given below:<a href="https://i.stack.imgur.com/DQU02.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/DQU02.png" alt="errors"></a></p>

<p>Here is the code of mine:</p>

<pre><code>#include &lt;opencv2/opencv.hpp&gt;
#include &lt;opencv2/imgproc/imgproc.hpp&gt;
#include&lt;opencv2/highgui/highgui.hpp&gt;
#include&lt;opencv2/core/core.hpp&gt;
#include&lt;iostream&gt;
#include&lt;stdio.h&gt;
#include&lt;stdlib.h&gt;
using namespace std;
using namespace cv;
Mat *calculateHist(Mat &amp;M, Mat &amp;He)
{
    float P[256]={0};
    int i, j, k, r;
    float sum = 0.0;
    float T[256]={0}; 
    int S[256]={0};
    for(i=0;i&lt;M.rows;i++)
    {
        for(j=0;j&lt;M.cols;j++)
        {
            int tmp = M.at&lt;uchar&gt;(i,j); 
            P[tmp] = P[tmp] +1; //[(M.at&lt;uchar&gt;(i,j))] + 1;
        }
    }
    for (i=0;i&lt;M.rows;i++)
    {
        for(j=0;j&lt;M.cols;j++)
        {
            sum = sum + P[(M.at&lt;uchar&gt;(i,j))];
        }
    }
    //int num_pixel = (M.rows)*(M.cols)
    for(i=0;i&lt;256;i++)
    {
        P[i] = P[i]/(sum); 
    }
    T[0] = P[0];
    for( k=1; k&lt;256;k++)
    {
        T[k] = T[k-1] + P[k];
    }
    for( r=0; r&lt; 256; r++)
    {
        S[r] = cvRound(T[r]*255);
    }
    for(i=0;i&lt;M.rows;i++)
    {
        for(j=0;j&lt;M.cols;j++)
        {
            r = M.at&lt;uchar&gt;(i, j);
            He.at&lt;uchar&gt;(i,j) = S[r];
        }
    }
    return (&amp;He);
}
int main(int argc, char *argv[])
{

    Mat image = imread(argv[1],0);
    Mat He(image.size,image.type);

    He = calculateHist(image, He);
    imshow("original_image", image);
    imshow( "histogram_equalized", He );


    waitKey(0);
    return 0;
}
</code></pre>
