opencv/samples/cpp/tutorial_code/ImgTrans/Sobel_Demo.cpp

/**
 * @file Sobel_Demo.cpp
 * @brief Sample code using Sobel and/or Scharr OpenCV functions to make a simple Edge Detector
 * @author OpenCV team
 */

#include "opencv2/imgproc.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"

using namespace cv;

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

  //![load]
  String imageName("../data/lena.jpg"); // by default
  if (argc > 1)
  {
      imageName = argv[1];
  }
  src = imread( imageName, IMREAD_COLOR ); // Load an image

  if( src.empty() )
    { return -1; }
  //![load]

  //![reduce_noise]
  GaussianBlur( src, src, Size(3,3), 0, 0, BORDER_DEFAULT );
  //![reduce_noise]

  //![convert_to_gray]
  cvtColor( src, src_gray, COLOR_BGR2GRAY );
  //![convert_to_gray]

  //![sobel]
  /// 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 );

  /// 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 );
  //![sobel]

  //![convert]
  convertScaleAbs( grad_x, abs_grad_x );
  convertScaleAbs( grad_y, abs_grad_y );
  //![convert]

  //![blend]
  /// Total Gradient (approximate)
  addWeighted( abs_grad_x, 0.5, abs_grad_y, 0.5, 0, grad );
  //![blend]

  //![display]
  imshow( window_name, grad );
  waitKey(0);
  //![display]

  return 0;
}