Device camera data (not images but actual camera properties) - ios

Question

I need access to my devices camera data (not image data! Already have that). Such as, "pinhole" fx & fy & anything else I can possibly get.
Currently, I'm using AVFoundation's 'AVCaptureSession' with a custom UI. But previously I used 'UIImagePickerController' which has a delegate method called
imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any])
I was able to retrieve the taken photograph from the "info" dictionary. It also gave me very detailed information regarding the camera & its capabilities. As it stands, I don't know how to retrieve this same detailed information during 'AVCaptureSession' photography. Please help

Answer 1

You need to use AVCapturePhotoOutput and not AVCaptureStillImageOutput.
First the code below needs the following variables in your class
private let photoOutput = AVCapturePhotoOutput()
private var inProgressPhotoCaptureDelegates = [Int64 : AVPhotoCaptureDelegate]()
private let sessionQueue = DispatchQueue(label: "session queue", attributes: [], target: nil) // Communicate with the session
private var videoDeviceOrientation : AVCaptureVideoOrientation = .portrait // this needs updated as the device orientation changes
Add photo output at AVSession setup
// Add photo output.
if session.canAddOutput(photoOutput) {
session.addOutput(photoOutput)
self.photoOutput.isHighResolutionCaptureEnabled = true
}
Your capturePhoto() function should be setup as follows
func capturePhoto(aspectRatio : Float, metaData : NSDictionary?) {
sessionQueue.async {
// Update the photo output's connection to match the video orientation of the video preview layer.
if let photoOutputConnection = self.photoOutput.connection(with: AVMediaType.video) {
photoOutputConnection.videoOrientation = self.videoDeviceOrientation
}
// Capture a JPEG photo with flash set to off and high resolution photo enabled.
let photoSettings = AVCapturePhotoSettings()
photoSettings.flashMode = .off
photoSettings.isHighResolutionPhotoEnabled = true
if photoSettings.availablePreviewPhotoPixelFormatTypes.count > 0 {
photoSettings.previewPhotoFormat = [kCVPixelBufferPixelFormatTypeKey as String : photoSettings.availablePreviewPhotoPixelFormatTypes.first!]
}
// Use a separate object for the photo capture delegate to isolate each capture life cycle.
let photoCaptureDelegate = MyAVPhotoCaptureDelegate(completed: { [unowned self] photoCaptureDelegate in
// When the capture is complete, remove a reference to the photo capture delegate so it can be deallocated.
self.sessionQueue.async { [unowned self] in
self.inProgressPhotoCaptureDelegates[photoCaptureDelegate.requestedPhotoSettings.uniqueID] = nil
}
)
/*
The Photo Output keeps a weak reference to the photo capture delegate so
we store it in an array to maintain a strong reference to this object
until the capture is completed.
*/
self.inProgressPhotoCaptureDelegates[photoCaptureDelegate.requestedPhotoSettings.uniqueID] = photoCaptureDelegate
self.photoOutput.capturePhoto(with: photoSettings, delegate: photoCaptureDelegate)
}
}
The MyAVPhotoCaptureDelegate class referenced in the capturePhoto() function above will need to be setup as follows
class MyAVPhotoCaptureDelegate: NSObject, AVCapturePhotoCaptureDelegate {
init(completed: #escaping (AVPhotoCaptureDelegate) -> ()) {
self.completed = completed
}
private func didFinish() {
completed(self)
}
func photoOutput(_ captureOutput: AVCapturePhotoOutput, willCapturePhotoFor resolvedSettings: AVCaptureResolvedPhotoSettings) {
}
func photoOutput(_ captureOutput: AVCapturePhotoOutput, didFinishProcessingPhoto photoSampleBuffer: CMSampleBuffer?, previewPhoto previewPhotoSampleBuffer: CMSampleBuffer?, resolvedSettings: AVCaptureResolvedPhotoSettings, bracketSettings: AVCaptureBracketedStillImageSettings?, error: Error?) {
if let photoSampleBuffer = photoSampleBuffer {
let propertiesDictionary = NSMutableDictionary()
if let exif = CMGetAttachment(photoSampleBuffer, kCGImagePropertyExifDictionary as NSString, nil) {
if let exifDictionary = exif as? NSMutableDictionary {
// view exif data
}
}
photoData = AVCapturePhotoOutput.jpegPhotoDataRepresentation(forJPEGSampleBuffer: photoSampleBuffer, previewPhotoSampleBuffer: previewPhotoSampleBuffer)
}
else {
print("Error capturing photo: \(String(describing:error))")
return
}
}
func photoOutput(_ captureOutput: AVCapturePhotoOutput, didFinishCaptureFor resolvedSettings: AVCaptureResolvedPhotoSettings, error: Error?) {
// Use PHPhotoLibrary to save photoData to photo library
...
}
private let completed : (MyAVPhotoCaptureDelegate) -> ()
}
Most of this code comes from my version of AVCam with the specifics of my implementation removed. I have left out the code for saving to the photo library but you can extract that from the sample code. You can view the exif data at the point I have commented "view exif data"