Desktop : OpenCV EqualizeHist For YUV

<h5>Goal</h5>
Test OpenCV EqualizeHist with YUV channel.

```OpenCV_ContrastUseEqualizeHistForYUV.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.image.BufferedImage;
import java.util.ArrayList;
import java.util.List;

public class OpenCV_ContrastUseEqualizeHistForYUV {
    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() {
            public void run() {
                try {
                    OpenCV_ContrastUseEqualizeHistForYUV window = new OpenCV_ContrastUseEqualizeHistForYUV();
                    window.frmjavaSwing.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the application.
     */
    public OpenCV_ContrastUseEqualizeHistForYUV() {
        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(equalizeHist(source));

        frmjavaSwing = new JFrame();
        frmjavaSwing.setTitle("opencv彩色影像對比練習3");
        frmjavaSwing.setBounds(100, 100, 520, 550);
        frmjavaSwing.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frmjavaSwing.getContentPane().setLayout(null);

        final JLabel lblNewLabel = new JLabel("");
        lblNewLabel.setBounds(10, 10, 438, 455);
        lblNewLabel.setIcon(new ImageIcon(image));
        frmjavaSwing.getContentPane().add(lblNewLabel);
    }

    public Mat equalizeHist(Mat source){
        Mat destination=new Mat(source.rows(),source.cols(),source.type());
        Mat tempYUV=new Mat(source.rows(),source.cols(),source.type());
        Imgproc.cvtColor(source, tempYUV, Imgproc.COLOR_RGB2YUV);
        List<Mat> yuvList = new ArrayList<Mat>(3);
        Core.split(tempYUV, yuvList);
        Imgproc.equalizeHist(yuvList.get(0), yuvList.get(0));
        //Imgproc.equalizeHist(yuvList.get(1), yuvList.get(1));
        //Imgproc.equalizeHist(yuvList.get(2), yuvList.get(2));
        Core.merge(yuvList, destination);
        Imgproc.cvtColor(destination, destination, Imgproc.COLOR_YUV2RGB);
        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_contrast_use_equalize_hist_for_yuv.JPG](https://qiita-image-store.s3.ap-northeast-1.amazonaws.com/0/276243/d9558c19-c28d-194b-c999-e7b8dfa1c372.jpeg)