iOS - Positioning a custom overlay on camera (vertical alignment). Size of top black bar

Question

I'm searching a programmatic solution to following problem: I want to draw a custom overlay on camera (iOS). And I want it to be vertically central on the camera output view. I've accomplished to draw my custom view centrically relatively to the screen, but not to the camera picture.

To do that, I need to get the size of the top black bar. How can I get it?

The size of top and bottom bars are not equal, that's why the picture I get has this annoying y-offset to the bottom.

Notice the offset of the resulting pic:

Answer 1

OK guys, I ended up using AVFoundation, which in the end was even better solution as it is customizable. I had self.fullScreenImageView and self.previewLayer as class properties. You need to write your own code implementing the buttons and the code of taking a camera shot. Here you can play around with the quality of the photo to get optimal size/quality. I used 0.6, but you can choose whatever you want.

@import MobileCoreServices;
@import AVFoundation;

    - (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.

    [self.view setBackgroundColor:[UIColor blackColor]];

    self.fullScreenImageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height)];
    self.fullScreenImageView.contentMode = UIViewContentModeScaleAspectFit;
    [self.fullScreenImageView setCenter:self.view.center];

        AVCaptureSession *captureSession = [[AVCaptureSession alloc] init];
        captureSession.sessionPreset = AVCaptureSessionPresetHigh;
        AVCaptureDevice *captureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
        if (captureDevice) {
            NSError *error;
            AVCaptureDeviceInput *captureDeviceInput = [[AVCaptureDeviceInput alloc] initWithDevice:captureDevice error:&error];
            if (!error && [captureSession canAddInput:captureDeviceInput]) {
                [captureSession addInput:captureDeviceInput];
            }
        }

        AVCaptureStillImageOutput *stillImageOutput = [AVCaptureStillImageOutput new];
        [stillImageOutput setOutputSettings:@{AVVideoCodecKey : AVVideoCodecJPEG,
                                              AVVideoQualityKey : @(0.6)}];
        [captureSession addOutput:stillImageOutput];

        self.previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:captureSession];
        [self.previewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];
        self.previewLayer.frame = self.fullScreenImageView.bounds;
        self.previewLayer.position = CGPointMake(CGRectGetMidX(self.fullScreenImageView.bounds), CGRectGetMidY(self.fullScreenImageView.bounds));
        [self.fullScreenImageView.layer addSublayer:self.previewLayer];
        [captureSession startRunning];

        CGRect circleRect = CGRectMake(0, (self.fullScreenImageView.bounds.size.height - self.fullScreenImageView.bounds.size.width) / 2, self.fullScreenImageView.bounds.size.width, self.fullScreenImageView.bounds.size.width);
        UIBezierPath *circle = [UIBezierPath bezierPathWithOvalInRect:circleRect];
        CAShapeLayer *ringLayer = [CAShapeLayer layer];
        ringLayer.path = circle.CGPath;
        ringLayer.fillColor = nil;
        ringLayer.strokeColor = [UIColor redColor].CGColor;
        ringLayer.lineWidth = 2.0;
        ringLayer.lineDashPattern = @[@5.0, @10.0];
        [self.fullScreenImageView.layer addSublayer:ringLayer];

        [self.navigationController setToolbarHidden:NO];
        [self.navigationController.toolbar setBarStyle:UIBarStyleBlackOpaque];
        [self.navigationController.toolbar setTintColor:[UIColor whiteColor]];
        // Add here some buttons, which are standard UIBarButtonItems

    [self.view addSubview:self.fullScreenImageView];
}