While printing values from a 16-bit Mat I'm getting only the lower 8-bit part of the number. For example if the number is 324, I'm getting the printed value as 68 which is 324-256. In the code below Ix_Ix is the element-wise multiplication of Ix, but it does not print values greater than 255. Instead it gives the lower 8 bits. Is there a problem with my code? How do I get the correct values?

include "opencv2/imgproc/imgproc.hpp"

include "opencv2/highgui/highgui.hpp"

include <stdlib.h>

include <stdio.h>

using namespace cv;

int main() { Mat orig_img, img_blur, img_gray;

orig_img = imread("Lenna.png");

GaussianBlur(orig_img, img_blur, Size(3,3), 0, 0, BORDER_DEFAULT);

cvtColor(img_blur, img_gray, CV_RGB2GRAY);

namedWindow("features", CV_WINDOW_AUTOSIZE);

Mat Ix, Iy;

Sobel(img_gray, Ix, CV_16U, 1, 0, 3, 1, 0, BORDER_DEFAULT);
Sobel(img_gray, Iy, CV_16U, 0, 1, 3, 1, 0, BORDER_DEFAULT);

Mat Ix_Ix, Iy_Iy, Ix_Iy;

Ix_Ix = Ix.mul(Ix);
Iy_Iy = Iy.mul(Iy);
Ix_Iy = Ix.mul(Iy);

int i, j;

for(i = 0; i < Ix_Ix.rows; i++)
{
    for(j = 0; j < Ix_Ix.cols; j++)
    {
        printf("%d\n", Ix.data[Ix.step[0]*i + Ix.step[1]*j]);
        printf("%d\n", Ix_Ix.data[Ix_Ix.step[0]*i + Ix_Ix.step[1]*j]);
        printf("\n");
    }
}

Mat Ix_Ix_blur, Iy_Iy_blur, Ix_Iy_blur;

GaussianBlur(Ix_Ix, Ix_Ix_blur, Size(5,5), 0, 0, BORDER_DEFAULT);
GaussianBlur(Iy_Iy, Iy_Iy_blur, Size(5,5), 0, 0, BORDER_DEFAULT);
GaussianBlur(Ix_Iy, Ix_Iy_blur, Size(5,5), 0, 0, BORDER_DEFAULT);

imshow("feature", Ix_Ix);

waitKey(0);

return 0;

}

While printing values from a 16-bit Mat I'm getting only the lower 8-bit part of the number. For example if the number is 324, I'm getting the printed value as 68 which is 324-256. In the code below Ix_Ix is the element-wise multiplication of Ix, but it does not print values greater than 255. Instead it gives the lower 8 bits. Is there a problem with my code? How do I get the correct values?

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

using namespace cv;
 
cv;

int main()
{
    Mat orig_img, img_blur, img_gray;
 
img_gray;

    orig_img = imread("Lenna.png");

 GaussianBlur(orig_img, img_blur, Size(3,3), 0, 0, BORDER_DEFAULT);

 cvtColor(img_blur, img_gray, CV_RGB2GRAY);

 namedWindow("features", CV_WINDOW_AUTOSIZE);

 Mat Ix, Iy;

 Sobel(img_gray, Ix, CV_16U, 1, 0, 3, 1, 0, BORDER_DEFAULT);
 Sobel(img_gray, Iy, CV_16U, 0, 1, 3, 1, 0, BORDER_DEFAULT);

 Mat Ix_Ix, Iy_Iy, Ix_Iy;

 Ix_Ix = Ix.mul(Ix);
 Iy_Iy = Iy.mul(Iy);
 Ix_Iy = Ix.mul(Iy);

 int i, j;

 for(i = 0; i < Ix_Ix.rows; i++)
 {
     for(j = 0; j < Ix_Ix.cols; j++)
     {
         printf("%d\n", Ix.data[Ix.step[0]*i + Ix.step[1]*j]);
         printf("%d\n", Ix_Ix.data[Ix_Ix.step[0]*i + Ix_Ix.step[1]*j]);
         printf("\n");
     }
 }

 Mat Ix_Ix_blur, Iy_Iy_blur, Ix_Iy_blur;

 GaussianBlur(Ix_Ix, Ix_Ix_blur, Size(5,5), 0, 0, BORDER_DEFAULT);
 GaussianBlur(Iy_Iy, Iy_Iy_blur, Size(5,5), 0, 0, BORDER_DEFAULT);
 GaussianBlur(Ix_Iy, Ix_Iy_blur, Size(5,5), 0, 0, BORDER_DEFAULT);

 imshow("feature", Ix_Ix);

 waitKey(0);

 return 0;
}
  
}