C++ opencv Sobel

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

using namespace cv;

/** @function main */
int main(int argc, char** argv)
{
Mat frame, src_gray;
Mat grad;
char* window_name = "Sobel Demo - Simple Edge Detector";
int scale = 1;
int delta = 0;
int ddepth = CV_16S;

int c;

VideoCapture cap(0);
while (1)
{
cap >> frame;
GaussianBlur(frame, frame, Size(3, 3), 0, 0, BORDER_DEFAULT);
/// Convert it to gray
cvtColor(frame, src_gray, CV_BGR2GRAY);

/// Create window
namedWindow(window_name, CV_WINDOW_AUTOSIZE);

/// Generate grad_x and grad_y
Mat grad_x, grad_y;
Mat abs_grad_x, abs_grad_y;

/// Gradient X
//Scharr( src_gray, grad_x, ddepth, 1, 0, scale, delta, BORDER_DEFAULT );
Sobel(src_gray, grad_x, ddepth, 1, 0, 3, scale, delta, BORDER_DEFAULT);
convertScaleAbs(grad_x, abs_grad_x);

/// Gradient Y
//Scharr( src_gray, grad_y, ddepth, 0, 1, scale, delta, BORDER_DEFAULT );
Sobel(src_gray, grad_y, ddepth, 0, 1, 3, scale, delta, BORDER_DEFAULT);
convertScaleAbs(grad_y, abs_grad_y);

/// Total Gradient (approximate)
addWeighted(abs_grad_x, 0.5, abs_grad_y, 0.5, 50, grad);

imshow(window_name, grad);
if (waitKey(30) == 27)
break;
}
return 0;
}