content: /**
   * @file SobelDemo.java
   * @brief Sample code using Sobel and/or Scharr OpenCV functions to make a simple Edge Detector
   */
  
  import org.opencv.core.*;
  import org.opencv.highgui.HighGui;
  import org.opencv.imgcodecs.Imgcodecs;
  import org.opencv.imgproc.Imgproc;
  
  class SobelDemoRun {
  
      public void run(String[] args) {
  
          //! [declare_variables]
          // First we declare the variables we are going to use
          Mat src, src_gray = new Mat();
          Mat grad = new Mat();
          String window_name = "Sobel Demo - Simple Edge Detector";
          int scale = 1;
          int delta = 0;
          int ddepth = CvType.CV_16S;
          //! [declare_variables]
  
          //! [load]
          // As usual we load our source image (src)
          // Check number of arguments
          if (args.length == 0){
              System.out.println("Not enough parameters!");
              System.out.println("Program Arguments: [image_path]");
              System.exit(-1);
          }
  
          // Load the image
          src = Imgcodecs.imread(args[0]);
  
          // Check if image is loaded fine
          if( src.empty() ) {
              System.out.println("Error opening image: " + args[0]);
              System.exit(-1);
          }
          //! [load]
  
          //! [reduce_noise]
          // Remove noise by blurring with a Gaussian filter ( kernel size = 3 )
          Imgproc.GaussianBlur( src, src, new Size(3, 3), 0, 0, Core.BORDER_DEFAULT );
          //! [reduce_noise]
  
          //! [convert_to_gray]
          // Convert the image to grayscale
          Imgproc.cvtColor( src, src_gray, Imgproc.COLOR_RGB2GRAY );
          //! [convert_to_gray]
  
          //! [sobel]
          /// Generate grad_x and grad_y
          Mat grad_x = new Mat(), grad_y = new Mat();
          Mat abs_grad_x = new Mat(), abs_grad_y = new Mat();
  
          /// Gradient X
          //Imgproc.Scharr( src_gray, grad_x, ddepth, 1, 0, scale, delta, Core.BORDER_DEFAULT );
          Imgproc.Sobel( src_gray, grad_x, ddepth, 1, 0, 3, scale, delta, Core.BORDER_DEFAULT );
  
          /// Gradient Y
          //Imgproc.Scharr( src_gray, grad_y, ddepth, 0, 1, scale, delta, Core.BORDER_DEFAULT );
          Imgproc.Sobel( src_gray, grad_y, ddepth, 0, 1, 3, scale, delta, Core.BORDER_DEFAULT );
          //! [sobel]
  
          //![convert]
          // converting back to CV_8U
          Core.convertScaleAbs( grad_x, abs_grad_x );
          Core.convertScaleAbs( grad_y, abs_grad_y );
          //![convert]
  
          //! [add_weighted]
          /// Total Gradient (approximate)
          Core.addWeighted( abs_grad_x, 0.5, abs_grad_y, 0.5, 0, grad );
          //! [add_weighted]
  
          //! [display]
          HighGui.imshow( window_name, grad );
          HighGui.waitKey(0);
          //! [display]
  
          System.exit(0);
      }
  }
  
  public class SobelDemo {
      public static void main(String[] args) {
          // Load the native library.
          System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
          new SobelDemoRun().run(args);
      }
  }
  