Desktop : OpenCV Polylines

<H5>Goal</H5>
Test OpenCV Polyline.

```OpenCV_Polylines.java
import org.opencv.core.*;
import org.opencv.core.Point;
import org.opencv.imgproc.Imgproc;

import javax.swing.*;

import java.awt.*;
import java.awt.image.BufferedImage;
import java.util.ArrayList;
import java.util.List;

public class OpenCV_Polylines {
    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_Polylines window = new OpenCV_Polylines();
                    window.frmjavaSwing.setVisible(true);
                }catch (Exception e){
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the application.
     */
    public OpenCV_Polylines() {
        initialize();
    }
    /**
        *  Init the contents of the frame.
        */
    private void initialize() {
        Mat source =  paint();
        BufferedImage image=matToBufferedImage(source);

        frmjavaSwing = new JFrame();
        frmjavaSwing.setTitle("opencv 畫多邊形練習(中空)");
        frmjavaSwing.setBounds(100, 100, 300, 300);
        frmjavaSwing.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frmjavaSwing.getContentPane().setLayout(null);

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

    public Mat paint(){

        Mat source = new Mat(250,250, CvType.CV_8UC3, new Scalar(255,255,255));
        List<MatOfPoint> allMatOfPoint=new ArrayList<MatOfPoint>();
        MatOfPoint mop1=new MatOfPoint();
        List<Point> allPoint1=new ArrayList<Point>();
        allPoint1.add(new Point(38,21));
        allPoint1.add(new Point(13,128));
        allPoint1.add(new Point(13,139));
        allPoint1.add(new Point(155,240));
        allPoint1.add(new Point(148,167));
        allPoint1.add(new Point(203,209));
        allPoint1.add(new Point(233,133));
        allPoint1.add(new Point(154,26));
        mop1.fromList(allPoint1);

        MatOfPoint mop2=new MatOfPoint();
        List<Point> allPoint2=new ArrayList<Point>();
        allPoint2.add(new Point(125,0));
        allPoint2.add(new Point(0,128));
        allPoint2.add(new Point(130,139));

        mop2.fromList(allPoint2);
        allMatOfPoint.add(mop1);
        allMatOfPoint.add(mop2);
        Imgproc.polylines(source, allMatOfPoint,true, new Scalar(0,255,0),3);
        return source;
    }

    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_poly_lines.JPG](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/276243/e787cc3a-637e-9a64-704a-ffacf254e622.jpeg)