Desktop : OpenCV Laplacian Filter GrayScale

<h5>Goal</h5>
Test OpenCV Laplacian Filter with a GrayScale image.

```OpenCV_Laplacian_Filter_GrayScale.java
import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.imgcodecs.Imgcodecs;
import org.opencv.imgproc.Imgproc;

import javax.swing.*;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import java.awt.*;
import java.awt.image.BufferedImage;

public class OpenCV_Laplacian_Filter_GrayScale {

    static{System.loadLibrary(Core.NATIVE_LIBRARY_NAME);}
    private JFrame frmjavaSwing;

    /**
        *  Launch the application.
        */
    public static void main(String[] args){
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try{
                    OpenCV_Laplacian_Filter_GrayScale window = new OpenCV_Laplacian_Filter_GrayScale();
                    window.frmjavaSwing.setVisible(true);
                }catch (Exception e){
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     *  Create the application.
     */
    public OpenCV_Laplacian_Filter_GrayScale() {
        init();
    }
    private void init() {
        final Mat src = Imgcodecs.imread(
                "D:\\projects\\Java\\OpenCV_Samples\\resource\\imgs\\lena.jpg");
        final Mat temp = new Mat(src.rows(), src.cols(), src.type());
        Imgproc.cvtColor(src, temp, Imgproc.COLOR_RGB2GRAY);
        BufferedImage image = matToBufferedImage(temp);

        frmjavaSwing = new JFrame();
        frmjavaSwing.setTitle("opencv Laplacian灰階影像練習");
        frmjavaSwing.setBounds(100, 100, 560, 620);
        frmjavaSwing.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frmjavaSwing.getContentPane().setLayout(null);

        final JLabel lblNewLabel = new JLabel("");
        lblNewLabel.setBounds(5, 60, image.getHeight() + 10, image.getWidth() + 10);
        lblNewLabel.setIcon(new ImageIcon(image));
        frmjavaSwing.getContentPane().add(lblNewLabel);

        JLabel lblKsize = new JLabel("Ksize:");
        lblKsize.setBounds(10, 10, 46, 15);
        frmjavaSwing.getContentPane().add(lblKsize);

        final JSlider slider_Ksize = new JSlider();
        slider_Ksize.setMinimum(1);
        slider_Ksize.setMaximum(31);

        slider_Ksize.setValue(1);
        slider_Ksize.setBounds(50, 0, 200, 25);
        frmjavaSwing.getContentPane().add(slider_Ksize);

        final JLabel lblKsize_Val = new JLabel("1");
        lblKsize_Val.setBounds(253, 10, 46, 15);
        frmjavaSwing.getContentPane().add(lblKsize_Val);

        JLabel lblScale = new JLabel(" Scale:");
        lblScale.setBounds(5, 35, 42, 15);
        frmjavaSwing.getContentPane().add(lblScale);

        final JSlider slider_Scale = new JSlider();
        slider_Scale.setMinimum(1);

        slider_Scale.setValue(1);
        slider_Scale.setBounds(50, 35, 200, 25);
        frmjavaSwing.getContentPane().add(slider_Scale);

        final JLabel lblScale_Val = new JLabel("1");
        lblScale_Val.setBounds(253, 35, 46, 15);
        frmjavaSwing.getContentPane().add(lblScale_Val);

        JLabel lblNewLabel_1 = new JLabel("delta");
        lblNewLabel_1.setBounds(301, 10, 46, 15);
        frmjavaSwing.getContentPane().add(lblNewLabel_1);

        final JSlider slider_Delta = new JSlider();

        slider_Delta.setValue(0);
        slider_Delta.setBounds(283, 35, 180, 25);
        frmjavaSwing.getContentPane().add(slider_Delta);

        final JLabel lblDelta_Val = new JLabel("0");
        lblDelta_Val.setBounds(473, 35, 46, 15);
        frmjavaSwing.getContentPane().add(lblDelta_Val);

        slider_Ksize.addChangeListener(new ChangeListener() {
            public void stateChanged(ChangeEvent arg0) {

                if (slider_Ksize.getValue() % 2 == 0) {
                    slider_Ksize.setValue(slider_Ksize.getValue() + 1);
                }
                lblKsize_Val.setText(slider_Ksize.getValue() + "");
                BufferedImage newImage = matToBufferedImage(Laplacian(temp, slider_Ksize.getValue(), slider_Scale.getValue(), slider_Delta.getValue()));
                lblNewLabel.setIcon(new ImageIcon(newImage));
            }
        });

        slider_Scale.addChangeListener(new ChangeListener() {
            public void stateChanged(ChangeEvent arg0) {
                lblScale_Val.setText(slider_Scale.getValue() + "");
                BufferedImage newImage = matToBufferedImage(Laplacian(temp, slider_Ksize.getValue(), slider_Scale.getValue(), slider_Delta.getValue()));
                lblNewLabel.setIcon(new ImageIcon(newImage));

            }
        });

        slider_Delta.addChangeListener(new ChangeListener() {
            public void stateChanged(ChangeEvent arg0) {
                lblDelta_Val.setText(slider_Delta.getValue() + "");
                BufferedImage newImage = matToBufferedImage(Laplacian(temp, slider_Ksize.getValue(), slider_Scale.getValue(), slider_Delta.getValue()));
                lblNewLabel.setIcon(new ImageIcon(newImage));
            }
        });
    }

    public Mat Laplacian(Mat source,int ksize,double scale,double delta){
        Mat destination=new Mat(source.rows(),source.cols(),source.type());
        Imgproc.Laplacian(source, destination, -1,ksize,scale,delta);
        return destination;

    }

    public BufferedImage matToBufferedImage(Mat matrix) {
        int cols = matrix.cols();
        int rows = matrix.rows();
        int elemSize = (int)matrix.elemSize();
        byte[] data = new byte[cols * rows * elemSize];
        int type;
        matrix.get(0, 0, data);
        switch (matrix.channels()) {
            case 1:
                type = BufferedImage.TYPE_BYTE_GRAY;
                break;
            case 3:
                type = BufferedImage.TYPE_3BYTE_BGR;
                // bgr to rgb
                byte b;
                for(int i=0; i<data.length; i=i+3) {
                    b = data[i];
                    data[i] = data[i+2];
                    data[i+2] = b;
                }
                break;
            default:
                return null;
        }
        BufferedImage image2 = new BufferedImage(cols, rows, type);
        image2.getRaster().setDataElements(0, 0, cols, rows, data);
        return image2;
    }
}
```
<h5>Result</h5>
![opencv_laplacian_filter_gray_scale.JPG](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/276243/fd56f6e2-998f-2614-09f4-df8e8ab519e2.jpeg)