OpenCV/opencv/samples/java/tutorial_code/ImgTrans/LaPlace/LaplaceDemo.java

/**
 * @file LaplaceDemo.java
 * @brief Sample code showing how to detect edges using the Laplace operator
 */

import org.opencv.core.*;
import org.opencv.highgui.HighGui;
import org.opencv.imgcodecs.Imgcodecs;
import org.opencv.imgproc.Imgproc;

class LaplaceDemoRun {

    public void run(String[] args) {
        //! [variables]
        // Declare the variables we are going to use
        Mat src, src_gray = new Mat(), dst = new Mat();
        int kernel_size = 3;
        int scale = 1;
        int delta = 0;
        int ddepth = CvType.CV_16S;
        String window_name = "Laplace Demo";
        //! [variables]

        //! [load]
        String imageName = ((args.length > 0) ? args[0] : "../data/lena.jpg");

        src = Imgcodecs.imread(imageName, Imgcodecs.IMREAD_COLOR); // Load an image

        // Check if image is loaded fine
        if( src.empty() ) {
            System.out.println("Error opening image");
            System.out.println("Program Arguments: [image_name -- default ../data/lena.jpg] \n");
            System.exit(-1);
        }
        //! [load]

        //! [reduce_noise]
        // Reduce 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]

        /// Apply Laplace function
        Mat abs_dst = new Mat();
        //! [laplacian]
        Imgproc.Laplacian( src_gray, dst, ddepth, kernel_size, scale, delta, Core.BORDER_DEFAULT );
        //! [laplacian]

        //! [convert]
        // converting back to CV_8U
        Core.convertScaleAbs( dst, abs_dst );
        //! [convert]

        //! [display]
        HighGui.imshow( window_name, abs_dst );
        HighGui.waitKey(0);
        //! [display]

        System.exit(0);
    }
}

public class LaplaceDemo {
    public static void main(String[] args) {
        // Load the native library.
        System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
        new LaplaceDemoRun().run(args);
    }
}