Desktop : OpenCV color space

<h5>Goal</h5>
Test OpenCV change color space.

```OpenCV_ChangeColorSpace.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 java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;

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

    /**
     *  Launch the application.
     */
    public static void main(String[] args) {

        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    OpenCV_ChangeColorSpace window = new OpenCV_ChangeColorSpace();
                    window.frmjavaSwing.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the application.
     */
    public OpenCV_ChangeColorSpace() {
        initialize();
    }

    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {
        final Mat source = Imgcodecs.imread(
                "D:\\projects\\Java\\OpenCV_Samples\\resource\\imgs\\clean.jpg");

        BufferedImage image=matToBufferedImage(source);

        frmjavaSwing = new JFrame();
        frmjavaSwing.setTitle("opencv 顏色空間轉換練習");
        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);

        JButton btnRK0 = new JButton("RGB2HLS");
        btnRK0.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                BufferedImage newImage=matToBufferedImage(colorSpaceConversion(source,0));
                lblNewLabel.setIcon(new ImageIcon(newImage));
            }
        });
        btnRK0.setBounds(5, 10, 110, 23);
        frmjavaSwing.getContentPane().add(btnRK0);

        JButton btnK1 = new JButton("RGB2BGR");
        btnK1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                BufferedImage newImage=matToBufferedImage(colorSpaceConversion(source,1));
                lblNewLabel.setIcon(new ImageIcon(newImage));
            }
        });
        btnK1.setBounds(5, 43, 110, 23);
        frmjavaSwing.getContentPane().add(btnK1);

        JButton btnK2 = new JButton("RGB2HSV");
        btnK2.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                BufferedImage newImage=matToBufferedImage(colorSpaceConversion(source,2));
                lblNewLabel.setIcon(new ImageIcon(newImage));
            }
        });
        btnK2.setBounds(118, 10, 98, 23);
        frmjavaSwing.getContentPane().add(btnK2);

        JButton btnK3 = new JButton("RGB2Lab");
        btnK3.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                BufferedImage newImage=matToBufferedImage(colorSpaceConversion(source,3));
                lblNewLabel.setIcon(new ImageIcon(newImage));
            }
        });
        btnK3.setBounds(118, 43, 98, 23);
        frmjavaSwing.getContentPane().add(btnK3);

        JButton btnK4 = new JButton("RGB2Luv");
        btnK4.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                BufferedImage newImage=matToBufferedImage(colorSpaceConversion(source,4));
                lblNewLabel.setIcon(new ImageIcon(newImage));
            }
        });
        btnK4.setBounds(226, 10, 100, 23);
        frmjavaSwing.getContentPane().add(btnK4);

        JButton btnK5 = new JButton("RGB2YUV");
        btnK5.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                BufferedImage newImage=matToBufferedImage(colorSpaceConversion(source,5));
                lblNewLabel.setIcon(new ImageIcon(newImage));
            }
        });
        btnK5.setBounds(226, 43, 100, 23);
        frmjavaSwing.getContentPane().add(btnK5);

        JButton btnK6 = new JButton("RGB2YCrCb");
        btnK6.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                BufferedImage newImage=matToBufferedImage(colorSpaceConversion(source,6));
                lblNewLabel.setIcon(new ImageIcon(newImage));
            }
        });
        btnK6.setBounds(336, 10, 110, 23);
        frmjavaSwing.getContentPane().add(btnK6);

        JButton btnK7 = new JButton("RGB2XYZ");
        btnK7.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                BufferedImage newImage=matToBufferedImage(colorSpaceConversion(source,7));
                lblNewLabel.setIcon(new ImageIcon(newImage));
            }
        });
        btnK7.setBounds(336, 43, 98, 23);
        frmjavaSwing.getContentPane().add(btnK7);
    }

    public Mat colorSpaceConversion(Mat source,int type){

        Mat destination=new Mat(source.rows(),source.cols(),source.type());
        if (type==0){
            Imgproc.cvtColor(source, destination, Imgproc.COLOR_RGB2HLS);
        }else  if (type==1){
            Imgproc.cvtColor(source, destination, Imgproc.COLOR_RGB2BGR);
        }else  if (type==2){
            Imgproc.cvtColor(source, destination, Imgproc.COLOR_RGB2HSV);
        }else  if (type==3){
            Imgproc.cvtColor(source, destination, Imgproc.COLOR_RGB2Lab);
        }else  if (type==4){
            Imgproc.cvtColor(source, destination, Imgproc.COLOR_RGB2Luv);
        }else  if (type==5){
            Imgproc.cvtColor(source, destination, Imgproc.COLOR_RGB2YUV);
        }else  if (type==6){
            Imgproc.cvtColor(source, destination, Imgproc.COLOR_RGB2YCrCb);
        }else  if (type==7){
            Imgproc.cvtColor(source, destination, Imgproc.COLOR_RGB2XYZ);
        }
        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_color_space.JPG](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/276243/66947827-2652-c06b-131a-34e6e8ddb378.jpeg)