Objective-C : No Matter what I do CIDetector is always nil

Question

Trying to get a simple Proof of concept going with Apple's face detection API. I've looked at a couple of other examples including Apple's SquareCam, and this one https://github.com/jeroentrappers/FaceDetectionPOC

based on these, it seems like I am following the correct pattern to get the APIs going, but I am stuck. No matter what I do, the CIDetector for my face detector is always nil!!!

I would seriously appreciate any help, clues - hints - suggestions!

-(void)initCamera{
session = [[AVCaptureSession alloc]init];

AVCaptureDevice *device;
/*
if([self frontCameraAvailable]){
    device = [self frontCamera];
}else{
    device = [self backCamera];
}*/

device = [self frontCamera];
isUsingFrontFacingCamera = YES;
NSError *error = nil;

AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];

if(input && [session canAddInput:input]){
    [session addInput:input];
}else{
    NSLog(@"Error %@", error);
    //make this Dlog...
}


videoDataOutput = [[AVCaptureVideoDataOutput alloc]init];
NSDictionary *rgbOutputSettings = [NSDictionary dictionaryWithObject:
                                   [NSNumber numberWithInt:kCMPixelFormat_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey];
[videoDataOutput setVideoSettings:rgbOutputSettings];
[videoDataOutput setAlwaysDiscardsLateVideoFrames:YES];

videoDataOutputQueue = dispatch_queue_create("VideoDataOutputQueue", DISPATCH_QUEUE_SERIAL);
[videoDataOutput setSampleBufferDelegate:self queue:videoDataOutputQueue];
[[videoDataOutput connectionWithMediaType:AVMediaTypeVideo]setEnabled:YES];

if ([session canAddOutput:videoDataOutput]) {
    [session addOutput:videoDataOutput];
}




[self embedPreviewInView:self.theImageView];



[session startRunning];



}



-(void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection{

CVPixelBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
CFDictionaryRef attachments = CMCopyDictionaryOfAttachments(kCFAllocatorDefault, sampleBuffer, kCMAttachmentMode_ShouldPropagate);
CIImage *ciImage = [[CIImage alloc] initWithCVPixelBuffer:pixelBuffer options:(__bridge NSDictionary *)attachments];


if(attachments){
    CFRelease(attachments);
}



UIDeviceOrientation curDeviceOrientation = [[UIDevice currentDevice] orientation];


NSDictionary *imageOptions = @{CIDetectorImageOrientation:[self exifOrientation:curDeviceOrientation] };


NSDictionary *detectorOptions = @{CIDetectorAccuracy: CIDetectorAccuracyLow};

CIDetector *faceDetector = [CIDetector detectorOfType:CIFeatureTypeFace context:nil options:detectorOptions];


NSArray *faceFeatures = [faceDetector featuresInImage:ciImage options:imageOptions];
if([faceFeatures count]>0){
    NSLog(@"GOT a face!");
    NSLog(@"%@", faceFeatures);

}


dispatch_async(dispatch_get_main_queue(), ^(void) {
    //NSLog(@"updating main thread");
});


}

Answer 1

I'm assuming you're using this article, because I was too and had the same problem. There's actually a bug in his code. The CIDetector instantiation should look like:

CIDetector *smileDetector = [CIDetector detectorOfType:CIDetectorTypeFace
                            context:context 
                            options:@{CIDetectorTracking: @YES, 
                                      CIDetectorAccuracy: CIDetectorAccuracyLow}];

Note that the detector type is CIDetectorTypeFace, rather than CIDetectorSmile. CIDetectorSmile is a feature option rather than a detector type, so to extract just the smiles (and not all the faces), use this code:

NSArray *features = [smileDetector featuresInImage:image options:@{CIDetectorSmile: @YES}];

Answer 2

CIDetector *smileDetector = [CIDetector detectorOfType:CIDetectorTypeFace
                            context:context 
                            options:@{CIDetectorTracking: @YES, 
                                      CIDetectorAccuracy: CIDetectorAccuracyLow}];
NSArray *features = [smileDetector featuresInImage:image options:@{CIDetectorSmile:@YES}];
if (([features count] > 0) && (((CIFaceFeature *)features[0]).hasSmile)) {
    UIImageWriteToSavedPhotosAlbum(image, self, @selector(didFinishWritingImage), features);
} else {
    self.label.text = @"Say Cheese!"
}