How to detect a face in an image using Java

Problem Description

How to detect a face in an image using Java.

Solution

Following is the program to detect a face in an image using java.

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.imgcodecs.Imgcodecs;  
import org.opencv.imgproc.Imgproc; 
import org.opencv.objdetect.CascadeClassifier;  
  
public class DetectingFaceInAnImage {  
   public static void main (String[] args) {     
      
      //Loading the OpenCV core library  
      System.loadLibrary( Core.NATIVE_LIBRARY_NAME ); 

      //Reading the Image from the file and storing it in to a Matrix object 
      String file = "C:/opencv/facedetection_input.jpg";
      Mat src = Imgcodecs.imread(file);  
      
      //Instantiating the CascadeClassifier 
      String xmlFile = "C:/EXAMPLES/OpenCV/facedetect/lbpcascade_frontalface.xml"; 
      CascadeClassifier classifier = new CascadeClassifier(xmlFile); 

      //Detecting the face in the snap 
      MatOfRect faceDetections = new MatOfRect(); 
      classifier.detectMultiScale(src, faceDetections);  
      System.out.println(String.format("Detected %s faces", 
         faceDetections.toArray().length));  
      
      //Drawing boxes  
      for (Rect rect : faceDetections.toArray()) { 
         Imgproc.rectangle(src,       //where to draw the box 
         new Point(rect.x, rect.y),   //bottom left 
         new Point(rect.x + rect.width, rect.y + rect.height),  //top right  
         new Scalar(0, 0, 255), 
         3);    //RGB color 
      } 
      //Writing the image     
      Imgcodecs.imwrite("C:/opencv/facedetect_output1.jpg", src); 
      
      System.out.println("Image Processed");  
   }     
}

Input

Output