ImageUtils.java

import org.opencv.core.Mat;

import javax.swing.*;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.awt.image.DataBufferByte;

public class ImageUtils {

    public static BufferedImage Mat2BufferedImage(Mat m) {
        int type = BufferedImage.TYPE_BYTE_GRAY;
        if (m.channels() > 1) {
            type = BufferedImage.TYPE_3BYTE_BGR;
        }
        int bufferSize = m.channels() * m.cols() * m.rows();
        byte[] b = new byte[bufferSize];
        m.get(0, 0, b); // get all the pixels
        BufferedImage image = new BufferedImage(m.cols(), m.rows(), type);
        final byte[] targetPixels = ((DataBufferByte) image.getRaster().getDataBuffer()).getData();
        System.arraycopy(b, 0, targetPixels, 0, b.length);
        return image;

    }

    public static void display(Mat m, String title) {
        BufferedImage img = ImageUtils.Mat2BufferedImage(m);
        JFrame f = new JFrame();
        f.setTitle(title);
        ImageIcon icon = new ImageIcon(img);
        f.setLayout(new FlowLayout());
        f.setSize(img.getWidth(null) + 50, img.getHeight(null) + 50);
        JLabel lbl = new JLabel();
        lbl.setIcon(icon);
        f.add(lbl);
        f.setVisible(true);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    }
}