How to develop a Face recognition iPhone app?

Check this code.You have to import following:- CoreImage/CoreImage.h CoreImage/CoreImage.h and after that use the code:-

-(void)markFaces:(UIImageView *)facePicture
{
// draw a CI image with the previously loaded face detection picture
CIImage* image = [CIImage imageWithCGImage:facePicture.image.CGImage];

// create a face detector - since speed is not an issue we'll use a high accuracy
// detector
CIDetector* detector = [CIDetector detectorOfType:CIDetectorTypeFace 
                                          context:nil options:[NSDictionary dictionaryWithObject:CIDetectorAccuracyHigh forKey:CIDetectorAccuracy]];

// create an array containing all the detected faces from the detector    
NSArray* features = [detector featuresInImage:image];

// we'll iterate through every detected face.  CIFaceFeature provides us
// with the width for the entire face, and the coordinates of each eye
// and the mouth if detected.  Also provided are BOOL's for the eye's and
// mouth so we can check if they already exist.
for(CIFaceFeature* faceFeature in features)
{
    // get the width of the face
    CGFloat faceWidth = faceFeature.bounds.size.width;

    // create a UIView using the bounds of the face
    UIView* faceView = [[UIView alloc] initWithFrame:faceFeature.bounds];

    // add a border around the newly created UIView
    faceView.layer.borderWidth = 1;
    faceView.layer.borderColor = [[UIColor redColor] CGColor];

    // add the new view to create a box around the face
    [self.window addSubview:faceView];

    if(faceFeature.hasLeftEyePosition)
    {
        // create a UIView with a size based on the width of the face
        UIView* leftEyeView = [[UIView alloc] initWithFrame:CGRectMake(faceFeature.leftEyePosition.x-faceWidth*0.15, faceFeature.leftEyePosition.y-faceWidth*0.15, faceWidth*0.3, faceWidth*0.3)];
        // change the background color of the eye view
        [leftEyeView setBackgroundColor:[[UIColor blueColor] colorWithAlphaComponent:0.