Desktop : RoiForRectangleRoi For Rectangle

<h5>Goal</h5>
Test OpenCV roi for rectangle.

```OpenCV_RoiForRectangle.java
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Panel;

import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JLabel;
import javax.swing.JLayeredPane;
import java.awt.Color;
import java.awt.image.BufferedImage;

import org.opencv.core.Core;
import org.opencv.core.CvType;
import org.opencv.core.Mat;
import org.opencv.core.Point;
import org.opencv.core.Rect;
import org.opencv.core.Scalar;
import org.opencv.imgcodecs.Imgcodecs;
import org.opencv.imgproc.Imgproc;

import javax.swing.JSlider;
import javax.swing.event.ChangeListener;
import javax.swing.event.ChangeEvent;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

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

    public int srcX=0;
    public int srcY=0;

    public int secondX=0;
    public int secondY=0;

    public Mat matWantToSave;

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

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

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

    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {
        final Mat source = Imgcodecs.imread("D:\\projects\\Java\\OpenCV_Samples\\resource\\imgs\\DSC_0625.jpg");

        BufferedImage image=matToBufferedImage(source);

        frmjavaSwing = new JFrame();
        frmjavaSwing.setTitle("擷取ROI(區塊)練習");
        frmjavaSwing.setBounds(100, 100, 763, 425);
        frmjavaSwing.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frmjavaSwing.getContentPane().setLayout(null);

        final JLabel lblLocation = new JLabel("");
        lblLocation.setBounds(10, 10, 112, 25);
        frmjavaSwing.getContentPane().add(lblLocation);

        final JLabel lblLocation2 = new JLabel("");
        lblLocation2.setBounds(158, 10, 112, 25);
        frmjavaSwing.getContentPane().add(lblLocation2);

        JPanel panel = new JPanel();
        panel.setBounds(10, 45, 429, 348);
        frmjavaSwing.getContentPane().add(panel);

        final JLabel lblNewLabel = new JLabel("");
        panel.add(lblNewLabel);
        lblNewLabel.addMouseMotionListener(new MouseMotionAdapter() {
            @Override
            public void mouseDragged(MouseEvent arg0) {
                lblLocation2.setText("X:"+arg0.getX()+",Y:"+arg0.getY());

                BufferedImage newImage=matToBufferedImage(paintRectangle(arg0.getX(),arg0.getY()));
                lblNewLabel.setIcon(new ImageIcon(newImage));


            }
        });

        final JLabel lblRoi = new JLabel("");
        lblRoi.setBounds(444, 45, 288, 348);
        frmjavaSwing.getContentPane().add(lblRoi);


        lblNewLabel.setIcon(new ImageIcon(image));

        JButton btnNewButton = new JButton("擷取ROI");
        btnNewButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                Mat RoiMat=getRoi();
                if (RoiMat!=null){
                    BufferedImage newImage=matToBufferedImage(RoiMat);
                    lblRoi.setText("");
                    lblRoi.setIcon(new ImageIcon(newImage));
                }else{
                    lblRoi.setText("未規劃ROI區塊!");
                }

            }
        });
        btnNewButton.setBounds(278, 10, 97, 25);
        frmjavaSwing.getContentPane().add(btnNewButton);

        JButton btnNewButton_1 = new JButton("Save");
        btnNewButton_1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {

                if(getMatWantToSave()!=null){
                    Imgcodecs.imwrite("D:\\projects\\Java\\OpenCV_Samples\\resource\\imgs\\DSC_0625_sub.jpg",getMatWantToSave());
                }else{
                    System.out.println("未擷取ROI區塊!");
                }


            }
        });
        btnNewButton_1.setBounds(398, 10, 89, 25);
        frmjavaSwing.getContentPane().add(btnNewButton_1);



        lblNewLabel.addMouseListener(new MouseAdapter() {
            @Override
            public void mouseClicked(MouseEvent arg0) {
                lblLocation2.setText("");
                lblLocation.setText("初始點:X:"+arg0.getX()+",Y:"+arg0.getY());
                setSrcX(arg0.getX());
                setSrcY(arg0.getY());
                BufferedImage newImage=matToBufferedImage(paintPoint(arg0.getX(),arg0.getY()));
                lblNewLabel.setIcon(new ImageIcon(newImage));
            }
        });



    }

    public Mat paintPoint(int x,int y){
        Mat src = Imgcodecs.imread("D:\\projects\\Java\\OpenCV_Samples\\resource\\imgs\\DSC_0625.jpg");
        Imgproc.circle(src, new Point(x,y), 2, new Scalar(0,55,255),2);
        return src;

    }

    public Mat paintRectangle(int x,int y){
        Mat src = Imgcodecs.imread("D:\\projects\\Java\\OpenCV_Samples\\resource\\imgs\\DSC_0625.jpg");
        Point srcPoint=new Point(getSrcX(),getSrcY());
        Imgproc.rectangle(src, srcPoint, new Point(x,y), new Scalar(0,0,255),2);
        setSecondX(x);
        setSecondY(y);
        return src;

    }

    public Mat getRoi(){
        Mat RoiMat;
        if(getSecondX()>0 && getSecondY()>0){
            Mat source=
                    Imgcodecs.imread("D:\\projects\\Java\\OpenCV_Samples\\resource\\imgs\\DSC_0625.jpg");
            Rect roi=new Rect(new Point(getSrcX(),getSrcY()),new Point(getSecondX(),getSecondY()));

            RoiMat=source.submat(roi);
            setMatWantToSave(RoiMat);
        }else{
            RoiMat=null;
        }


        return RoiMat;

    }




    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;
    }

    public int getSrcX() {
        return srcX;
    }

    public void setSrcX(int srcX) {
        this.srcX = srcX;
    }

    public int getSrcY() {
        return srcY;
    }

    public void setSrcY(int srcY) {
        this.srcY = srcY;
    }

    public int getSecondX() {
        return secondX;
    }

    public void setSecondX(int secondX) {
        this.secondX = secondX;
    }

    public int getSecondY() {
        return secondY;
    }

    public void setSecondY(int secondY) {
        this.secondY = secondY;
    }

    public Mat getMatWantToSave() {
        return matWantToSave;
    }

    public void setMatWantToSave(Mat matWantToSave) {
        this.matWantToSave = matWantToSave;
    }
}
```
<h5>Result</h5>
![DSC_0625_sub.jpg](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/276243/16d54ec3-e627-7d8c-7fbb-05a5d59f7e50.jpeg)