Need help with a custom camera (swift)

How would I code a custom camera in Swift, with a preview of an image, a button to take a photo of that image, and then kind of freezing the image on the screen, while giving the user options to save the image, or retake the photo, etcetera.

I tried searching this up online and I realise that I need to need to create a UIView and set it as a CameraOverlay to the UIImagePicker, or use AVCamera.

However, my code so far only shows a black screen with an image preview taking up about the top half of the screen. The button I created to launch the photo library is not shown or clickable.

class SecondViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate{

@IBOutlet var imageView: UIImageView! weak var picker: UIImagePickerController!

@IBOutlet var cameraOverlay: UIView!

override func viewDidLoad() { super.viewDidLoad() self.view.addSubview(imageView)

var camera = UIImagePickerController()
camera.delegate = self
camera.allowsEditing = false
camera.sourceType = UIImagePickerControllerSourceType.Camera
camera.showsCameraControls = false

imageView.layer.frame = camera.cameraOverlayView!.frame
camera.cameraOverlayView = imageView
imageView = nil

self.presentViewController(camera, animated: false, completion: nil)

}

override func didReceiveMemoryWarning() { super.didReceiveMemoryWarning() }

override func viewWillAppear(animated: Bool){ self.navigationController?.navigationBarHidden = true }

@IBAction func openPhotoLibrary(sender: UIButton) {

var photoPicker = UIImagePickerController()
photoPicker.delegate = self
photoPicker.sourceType = .PhotoLibrary
self.presentViewController(photoPicker, animated: true, completion: nil)

}

func imagePickerController(picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [NSObject : AnyObject]){
    imageView.image = info[UIImagePickerControllerOriginalImage] as? UIImage
    self.dismissViewControllerAnimated(false, completion: nil)

}

@IBAction func takePhoto(sender: UIButton) { } }