Face detection with a webcam, using only OpenCV with Java, and not “javacv”

This is adapted from

In class window (yes, lowercase… not standard, but it’s how they did it…)

package edu.udallas.cs;

import javax.swing.JFrame;

import org.opencv.core.Mat;
import org.opencv.highgui.VideoCapture;

public class window {  
    public static void main(String arg[]){  
        // Load the native library.  
        String window_name = "Capture - Face detection";  
        JFrame frame = new JFrame(window_name);  
        processor my_processor=new processor();  
        My_Panel my_panel = new My_Panel();  
        //-- 2. Read the video stream  
        Mat webcam_image=new Mat();  
        VideoCapture capture =new VideoCapture(-1);   
        if( capture.isOpened())  
            while( true )  
                if( !webcam_image.empty() )  
                    //-- 3. Apply the classifier to the captured image  
                    //-- 4. Display the image  
                    my_panel.MatToBufferedImage(webcam_image); // We could look at the error...  
                    System.out.println(" --(!) No captured frame -- Break!");   

In class My_Panel:

package edu.udallas.cs;

 * Captures the camera stream with OpenCV  
 * Search for the faces  
 * Display a circle around the faces using Java
import java.awt.*;  
import java.awt.image.BufferedImage;  
import java.awt.image.DataBufferByte;  
import javax.swing.*;  
import org.opencv.core.Core;  
import org.opencv.core.Mat;  
import org.opencv.core.MatOfRect;  
import org.opencv.core.Point;  
import org.opencv.core.Rect;  
import org.opencv.core.Scalar;  
import org.opencv.core.Size;  
import org.opencv.highgui.VideoCapture;  
import org.opencv.imgproc.Imgproc;  
import org.opencv.objdetect.CascadeClassifier;  
class My_Panel extends JPanel{  
    private static final long serialVersionUID = 1L;  
    private BufferedImage image;  
    // Create a constructor method  

    public My_Panel(){  
     * Converts/writes a Mat into a BufferedImage.  
     * @param matrix Mat of type CV_8UC3 or CV_8UC1  
     * @return BufferedImage of type TYPE_3BYTE_BGR or TYPE_BYTE_GRAY  
    public boolean MatToBufferedImage(Mat matBGR){  
        long startTime = System.nanoTime();  
        int width = matBGR.width(), height = matBGR.height(), channels = matBGR.channels() ;  
        byte[] sourcePixels = new byte[width * height * channels];  
        matBGR.get(0, 0, sourcePixels);  
        // create new image and get reference to backing data  
        image = new BufferedImage(width, height, BufferedImage.TYPE_3BYTE_BGR);  
        final byte[] targetPixels = ((DataBufferByte) image.getRaster().getDataBuffer()).getData();  
        System.arraycopy(sourcePixels, 0, targetPixels, 0, sourcePixels.length);  
        long endTime = System.nanoTime();  
        System.out.println(String.format("Elapsed time: %.2f ms", (float)(endTime - startTime)/1000000));  
        return true;  
    public void paintComponent(Graphics g){  
        if (this.image==null) return;  
        g.drawImage(this.image,10,10,2*this.image.getWidth(),2*this.image.getHeight(), null);  
        //g.drawString("This is my custom Panel!",10,20);  

class processor {  
    private CascadeClassifier face_cascade;  
    // Create a constructor method  
    public processor(){  
        face_cascade=new CascadeClassifier("/home/hochberg/Research/OpenCV/opencv-2.4.8/data/haarcascades/haarcascade_profileface.xml");  
            System.out.println("--(!)Error loading A\n");  
            System.out.println("Face classifier loooaaaaaded up");  
    public Mat detect(Mat inputframe){    
        long startTime = System.nanoTime();  
        Mat mRgba=new Mat();  
        Mat mGrey=new Mat();  
        MatOfRect faces = new MatOfRect();  
        Imgproc.cvtColor( mRgba, mGrey, Imgproc.COLOR_BGR2GRAY);  
        Imgproc.equalizeHist( mGrey, mGrey );  
        face_cascade.detectMultiScale(mGrey, faces);  
        long endTime = System.nanoTime();  
        System.out.println(String.format("Detect time: %.2f ms", (float)(endTime - startTime)/1000000));  
        System.out.println(String.format("Detected %s faces", faces.toArray().length));  
        for(Rect rect:faces.toArray())  
            Point center= new Point(rect.x + rect.width*0.5, rect.y + rect.height*0.5 );  
            Core.ellipse( mRgba, center, new Size( rect.width*0.5, rect.height*0.5), 0, 0, 360, new Scalar( 255, 0, 255 ), 4, 8, 0 );  
        return mRgba;  

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