user3411226 user3411226 -3 years ago 91
Objective-C Question

Detect a face while my cam is open

i need to build an app with just a cam view, and it should detect my cam is looking at a face, can anyone point me in the right direction?
I have built something that detects a face on an image, but i need to work with a cam, here is what i have done so far:

- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
NSString *path = [[NSBundle mainBundle] pathForResource:@"picture" ofType:@"JPG"];
NSURL *url = [NSURL fileURLWithPath:path];

CIContext *context = [CIContext contextWithOptions:nil];

CIImage *image = [CIImage imageWithContentsOfURL:url];

NSDictionary *options = @{CIDetectorAccuracy: CIDetectorAccuracyHigh};

CIDetector *detector = [CIDetector detectorOfType:CIDetectorTypeFace context:context options:options];

NSArray *features = [detector featuresInImage:image];


i have done the following:

_session = [[AVCaptureSession alloc] init];
[_session setSessionPreset:AVCaptureSessionPresetPhoto];

AVCaptureDevice *inputDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];

NSError *error;
AVCaptureDeviceInput *deviceInput = [AVCaptureDeviceInput deviceInputWithDevice:inputDevice error:&error];

if([_session canAddInput:deviceInput]){
[_session addInput:deviceInput];

AVCaptureVideoPreviewLayer *previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:_session];
[previewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
CALayer *rootLayer = [[self view] layer];
[rootLayer setMasksToBounds:YES];

CGRect frame = self.frameCapture.frame;
[previewLayer setFrame:frame];

[rootLayer insertSublayer:previewLayer atIndex:0];
[_session startRunning];


-(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputMetadataObjects:(NSArray *)metadataObjects fromConnection:(AVCaptureConnection *)connection{
for(AVMetadataObject *metadataObject in metadataObjects) {
if([metadataObject.type isEqualToString:AVMetadataObjectTypeFace]) {

_faceDetectedLabel.text = @"face detected";

but still it is not detecting any faces, am i doing anything wrong?

Answer Source

You should add a metadata output before you'll have some data.

AVCaptureMetadataOutput *metadataOutput = [[AVCaptureMetadataOutput alloc] init];
// create a serial queue to handle metadata output
dispatch_queue_t metadataQueueOutput = dispatch_queue_create("com.YourAppName.metaDataQueue.OutputQueue", DISPATCH_QUEUE_SERIAL);
[metadataOutput setMetadataObjectsDelegate:self queue:metadataQueueOutput];
if ([_session canAddOutput:metadataOutput]) {
    [strongSelf.session addOutput:metadataOutput];
// set object types that you are interested, then you should not check type in output callback
metadataOutput.metadataObjectTypes = @[AVMetadataObjectTypeFace];

That should work. Let me know if it does

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