Desktop : OpenCV Rotate image 

<h5>Goal</h5>


```OpenCV_Rotate_with_Matrix2D.java
import org.opencv.core.Core;
import org.opencv.core.CvType;
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_Rotate_with_Matrix2D {
    static {System.loadLibrary(Core.NATIVE_LIBRARY_NAME);}

    private JFrame frmjavaSwing;
    double alpha =2;
    double beta =50;

    /**
     *  Launch the application.
     */
    public static void main(String[] args){
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try{
                    OpenCV_Rotate_with_Matrix2D window = new OpenCV_Rotate_with_Matrix2D();
                    window.frmjavaSwing.setVisible(true);
                }catch (Exception e){
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     *  Create the application.
     */
    public OpenCV_Rotate_with_Matrix2D(){
        init();
    }

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

        BufferedImage image = matToBufferedImage(src);

        frmjavaSwing = new JFrame();
        frmjavaSwing.setTitle("opencv角度旋轉練習");
        frmjavaSwing.setBounds(100, 100, 520, 550);
        frmjavaSwing.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frmjavaSwing.getContentPane().setLayout(null);

        final JLabel showAlphaValue = new JLabel("0");
        showAlphaValue.setBounds(250, 10, 46, 15);
        frmjavaSwing.getContentPane().add(showAlphaValue);

        final JLabel showBetaValue = new JLabel("0");
        showBetaValue.setBounds(250, 35, 46, 15);
        frmjavaSwing.getContentPane().add(showBetaValue);

        final JLabel lblNewLabel = new JLabel("");
        lblNewLabel.setBounds(10, 68, 438, 438);
        lblNewLabel.setIcon(new ImageIcon(image));
        frmjavaSwing.getContentPane().add(lblNewLabel);

        final JSlider slider_scale = new JSlider();
        slider_scale.setMinimum(1);
        slider_scale.setValue(10);
        slider_scale.setBounds(47, 33, 200, 25);
        frmjavaSwing.getContentPane().add(slider_scale);

        final JSlider slider_Angle = new JSlider();
        slider_Angle.setMaximum(359);
        slider_Angle.setValue(0);
        slider_Angle.addChangeListener(new ChangeListener() {
            public void stateChanged(ChangeEvent arg0) {
                //System.out.println(slider_alpha.getValue());
                showAlphaValue.setText((float)slider_Angle.getValue()/10+"");
                BufferedImage newImage=matToBufferedImage(rotate(src,slider_Angle.getValue(),(float)slider_scale.getValue()/10));
                lblNewLabel.setIcon(new ImageIcon(newImage));
            }
        });
        slider_Angle.setBounds(47, 10, 200, 25);
        frmjavaSwing.getContentPane().add(slider_Angle);

        JLabel lblAlpha = new JLabel("角度");
        lblAlpha.setBounds(10, 20, 46, 15);
        frmjavaSwing.getContentPane().add(lblAlpha);

        JLabel lblBeta = new JLabel("scale");
        lblBeta.setBounds(10, 45, 46, 15);
        frmjavaSwing.getContentPane().add(lblBeta);


        slider_scale.addChangeListener(new ChangeListener() {
            public void stateChanged(ChangeEvent arg0) {
                showBetaValue.setText((float)slider_scale.getValue()/10+"");
                BufferedImage newImage=matToBufferedImage(rotate(src,slider_Angle.getValue(),
                        (float)slider_scale.getValue()/10));
                lblNewLabel.setIcon(new ImageIcon(newImage));
            }
        });
    }

    public Mat rotate(Mat src , double angle, double scale){
        Mat rotMat = new Mat(2,3, CvType.CV_32FC1);
        Mat dst = new Mat(src.rows(),src.cols(),src.type());
        org.opencv.core.Point center = new org.opencv.core.Point(dst.cols()/2,dst.rows()/2);
        rotMat = Imgproc.getRotationMatrix2D(center,angle,scale);
        Imgproc.warpAffine(src,dst,rotMat,dst.size());

        return dst;
    }


    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_rotate_angle.JPG](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/276243/2957220a-2047-3a15-ec6f-41272cf76e62.jpeg)