Desktop : OpenCV Threshold

<h5>Goal</h5>
Test OpenCV test threshold.

```OpenCV_Threshold.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;
import java.nio.Buffer;

public class OpenCV_Threshold {

    static{System.loadLibrary(Core.NATIVE_LIBRARY_NAME);}

    private JFrame frmjavaSwing;
    double thresh = 0;
    double maxval = 0;
    int type =0;

    public static void main(String[] argv){

        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try{
                    OpenCV_Threshold window = new OpenCV_Threshold();
                    window.frmjavaSwing.setVisible(true);

                }catch(Exception e){
                    e.printStackTrace();
                }
            }
        });
    }

    public OpenCV_Threshold(){
        initialize();
        System.out.println("THRESH_BINARY="+ Imgproc.THRESH_BINARY);
        System.out.println("THRESH_BINARY_INV="+Imgproc.THRESH_BINARY_INV);
        System.out.println("TTHRESH_TRUNC="+Imgproc.THRESH_TRUNC);
        System.out.println("THRESH_TOZERO="+Imgproc.THRESH_TOZERO);
        System.out.println("THRESH_TOZERO_INV="+Imgproc.THRESH_TOZERO_INV);
    }

    /**
     * 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(threshold(source,thresh,maxval,type));

        frmjavaSwing = new JFrame();
        frmjavaSwing.setTitle("opencv Threshold�m��");
        frmjavaSwing.setBounds(100, 100, 520, 550);
        frmjavaSwing.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frmjavaSwing.getContentPane().setLayout(null);

        final JLabel showAlphaValue = new JLabel("2");
        showAlphaValue.setBounds(260, 10, 29, 15);
        frmjavaSwing.getContentPane().add(showAlphaValue);

        final JLabel showBetaValue = new JLabel("50");
        showBetaValue.setBounds(259, 35, 29, 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_Maxval = new JSlider();
        slider_Maxval.setValue(0);
        slider_Maxval.setMaximum(600);
        slider_Maxval.setBounds(57, 35, 200, 25);
        frmjavaSwing.getContentPane().add(slider_Maxval);

        final JSlider slider_type = new JSlider();
        slider_type.setMaximum(4);
        slider_type.setValue(0);
        slider_type.setBounds(314, 10, 115, 25);
        frmjavaSwing.getContentPane().add(slider_type);


        final JSlider slider_Threshold = new JSlider();
        slider_Threshold.setMaximum(600);
        slider_Threshold.setValue(0);
        slider_Threshold.addChangeListener(new ChangeListener() {
            public void stateChanged(ChangeEvent arg0) {
                //System.out.println(slider_alpha.getValue());
                showAlphaValue.setText(slider_Threshold.getValue()+"");
                BufferedImage newImage=matToBufferedImage(threshold(source,
                        slider_Threshold.getValue(),slider_Maxval.getValue(),slider_type.getValue()));
                lblNewLabel.setIcon(new ImageIcon(newImage));
            }
        });
        slider_Threshold.setBounds(57, 10, 200, 25);
        frmjavaSwing.getContentPane().add(slider_Threshold);

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

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

        JLabel lblType = new JLabel("type");
        lblType.setBounds(290, 10, 46, 15);
        frmjavaSwing.getContentPane().add(lblType);

        final JLabel showTypeValue = new JLabel("0");
        showTypeValue.setBounds(435, 10, 19, 15);
        frmjavaSwing.getContentPane().add(showTypeValue);

        slider_type.addChangeListener(new ChangeListener() {
            public void stateChanged(ChangeEvent arg0) {
                showTypeValue.setText(slider_type.getValue()+"");
                BufferedImage newImage=matToBufferedImage(threshold(source,
                        slider_Threshold.getValue(),slider_Maxval.getValue(),slider_type.getValue()));
                lblNewLabel.setIcon(new ImageIcon(newImage));

            }
        });

        slider_Maxval.addChangeListener(new ChangeListener() {
            public void stateChanged(ChangeEvent arg0) {
                showBetaValue.setText(slider_Maxval.getValue()+"");
                BufferedImage newImage=matToBufferedImage(threshold(source,
                        slider_Threshold.getValue(),slider_Maxval.getValue(),slider_type.getValue()));
                lblNewLabel.setIcon(new ImageIcon(newImage));
            }
        });
    }

    public Mat threshold(Mat source,double thresh,double maxval,int type){

        Mat destination=new Mat(source.rows(),source.cols(),source.type());
        Imgproc.threshold(source,destination, thresh, maxval, type);
        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>
![gui_threshold.JPG](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/276243/7f3109cd-3936-b460-f6fb-5d9d39bfa1d8.jpeg)