Face Detection From Photograph

In this tutorial, I am going to write an app to detect face from a photograph.

Create a new XCode Project single-view application called FaceDetectionFromPhoto.

In storyboard, add an UIImageView with the following constraints for the adaptive layout:

The constraints are shown on the Size Inspector above (right of screen). Also, set the View Mode to Aspect Fit as seen in the Attributes Inspector below (right of screen):

Then add a group photo to your SupportingFiles by right-clicking SupportingFiles folder and select Add Files to... :

I added obamafamily.jpg in the above example.

Next download this file

haarcascade_frontalface_alt.xml

Add the xml file to SupportingFolder the same way you did for the jpg file above.

Then, add the following frameworks to your project:

opencv2.framework

UIKit.framework

CoreGraphics.framework

In your Build Settings, under Apple LLVM 8.0, set Compile Sources As: 

Objective-C++

Hookup your storyboard's UIImageView to IBOutlet on ViewController.h and also create a variable called faceDetector and add the opencv2 header files. Your ViewController.h file should look like this:

//

//  ViewController.h

//  FaceDetectionFromPhoto

//

//  Created by Paul Chin on 12/26/14.

//  Copyright (c) 2014 Paul Chin. All rights reserved.

//

#import <UIKit/UIKit.h>

#import <opencv2/opencv.hpp>

#import <opencv2/highgui/ios.h>

@interface ViewController : UIViewController{

    cv::CascadeClassifier faceDetector;

}

@property (weak, nonatomic) IBOutlet UIImageView *imageView;

@end

And your ViewController.m as follows:

//

//  ViewController.m

//  FaceDetectionFromPhoto

//

//  Created by Paul Chin on 12/26/14.

//  Copyright (c) 2014 Paul Chin. All rights reserved.

//

#import "ViewController.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    // Do any additional setup after loading the view, typically from a nib.

    

    NSString *cascadePath = [[NSBundle mainBundle] 
                   pathForResource:@"haarcascade_frontalface_alt"

                            ofType:@"xml"];

    faceDetector.load([cascadePath UTF8String]);

    

    UIImage *image = [UIImage imageNamed:@"obamafamily.jpg"];

    

   

    cv::Mat faceImage;

    UIImageToMat(image, faceImage);

    

    cv::Mat gray;

    cvtColor(faceImage, gray, CV_BGR2GRAY);

    

    std::vector<cv::Rect>faces;

    faceDetector.detectMultiScale(gray, faces,1.1,2,
                        0|CV_HAAR_SCALE_IMAGE,cvSize(30, 30));

    

    

    for(unsigned int i=0; i<faces.size(); i++){

        const cv::Rect face = faces[i];

        cv::Point topLeft(face.x,face.y);

        cv::Point bottomRight= topLeft + cv::Point(face.width,face.height);

        

        // Draw rectangle around the face

        cv::Scalar magenta = cv::Scalar(255, 0, 255);

        cv::rectangle(faceImage, topLeft, bottomRight, magenta, 4, 8, 0);

        

        // Show resulting image

        self.imageView.image = MatToUIImage(faceImage);

    }

}

- (void)didReceiveMemoryWarning {

    [super didReceiveMemoryWarning];

    // Dispose of any resources that can be recreated.

}

@end

Then, run your app in the iOS Simulator:

I've set the ViewController background to green so that it stands out when I post to this blog.