A Class That Converts OpenCV BGR to Java BufferedImage

package org.ski;
import java.awt.image.BufferedImage;
import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.highgui.Highgui;
import org.opencv.imgproc.Imgproc;

public class Mat2Image {
    Mat mat = new Mat();
    BufferedImage img;
    byte[] dat;
    public Mat2Image() {}
    public Mat2Image(Mat mat) {
        getSpace(mat);
    }
    public void getSpace(Mat mat) {
        this.mat = mat;
        int w = mat.cols(), h = mat.rows();
        if (dat == null || dat.length != w * h * 3)
            dat = new byte[w * h * 3];
        if (img == null || img.getWidth() != w ||
                           img.getHeight() != h)
            img = new BufferedImage(w, h,
                    BufferedImage.TYPE_3BYTE_BGR);
    }
    BufferedImage getImage(Mat mat){
        getSpace(mat);
        mat.get(0, 0, dat);
        img.getRaster().setDataElements(0, 0,
               img.getWidth(), img.getHeight(), dat);
        return img;
    }
    static{
        System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
    }
}

cpp & java

#include < iostream >

using namespace std;
class Rect{
  int x, y, width,height;
  int getArea(){ return width*height;}
}