Am I doing the mean filter correct? What do i need to change to make it work?

Question

The problem is i dont know how to get the math done properly when using a mean filter. 3x3 kernel with a weight value of 1 in all 9 kernels. I got some help to use the sum part, but i do not know if it works correctly, i certainly cant build.

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <iostream>

using namespace cv;
using namespace std;

int main()

{
    Mat gray_image, convolued_image;

    gray_image = imread( "C:/1.jpg", CV_LOAD_IMAGE_GRAYSCALE);   // Read the file
    convolued_image = gray_image;


    if(!gray_image.data )                                     // Check for invalid input

    {
        cout <<  "Could not open or find the image" << std::endl ;
        return -1;
    }

    namedWindow( "RGB Input", CV_WINDOW_AUTOSIZE );    
    imshow( "RGB Input", gray_image );                 



     Mat meanImg;
       gray_image.copyTo(meanImg);

      namedWindow( "meanImg", CV_WINDOW_AUTOSIZE );    
    imshow( "meanImg", meanImg );  


        waitKey(0);    

        for (int y = 0; y < gray_image.rows; y++)
       {
               for (int x = 0; x < gray_image.cols; y++)
              {
                      int intesity = gray_image.at<uchar>(y,x);       
                      int sum = gray_image.at<uchar>(y+1,x+1);
                            sum = gray_image.at<uchar>(y+1,x);
                            sum = gray_image.at<uchar>(y+1,x-1);
                            sum = gray_image.at<uchar>(y,x-1);
                            sum = gray_image.at<uchar>(y,x+1);
                            sum = gray_image.at<uchar>(y-1,x-1);
                            sum = gray_image.at<uchar>(y+1,x);
                            sum = gray_image.at<uchar>(y+1,x+1);

                    int mean = sum/9;

                meanImg.at<uchar>(y,x) = mean;


              }
       }


    return 0;
}

Answer 1

sum = gray_image.at<uchar>(y+1,x);
sum = gray_image.at<uchar>(y+1,x-1);
sum = gray_image.at<uchar>(y,x-1);

Your variable is named sum , but you aren't actually adding anything here.

You also start off your loop by reading outside the bounds of the image.

Answer 2

Once you get it to build, you'll have these bugs to attend to:

You left out a character in

sum = gray_image.at<uchar>(y+1,x);

These lines replace the value of sum with a new value.

To actually add them together, do

sum += gray_image.at<uchar>(y+1,x);

You're also indexing outside the image bounds - you need to handle the cases where x or y are 0 or their respective maximum properly.

And in the inner loop, you say y++ where you should say x++ .