Hey there! I’ve run into this exact problem when building a photo app that handles both RAW and JPEG captures, so let me share a complete, working solution using the modern iOS APIs since those old jpegPhotoDataRepresentation and dngPhotoDataRepresentation methods got deprecated in iOS 11.

Step 1: Configure Your AVCapturePhotoOutput for RAW + JPEG Capture #

First, you need to set up your capture settings to enable both RAW and JPEG output. Make sure to check if the device supports RAW capture first (not all iOS devices do):

// Assuming you've already set up your AVCaptureSession and photoOutput
let photoSettings = AVCapturePhotoSettings()

// Enable RAW capture if available
if let rawPixelFormat = photoSettings.availableRawPhotoPixelFormatTypes.first {
    photoSettings.isRawCaptureEnabled = true
    photoSettings.rawPhotoPixelFormatType = rawPixelFormat
}

// Configure JPEG settings
photoSettings.isHighResolutionCaptureEnabled = true
photoSettings.jpegQuality = .high

// Trigger the capture
photoOutput.capturePhoto(with: photoSettings, delegate: self)

Step 2: Process the Photo in the Delegate Method #

In your didFinishProcessingPhoto delegate method, you’ll extract both the JPEG and RAW (DNG) data using the modern dataRepresentation(for:) method instead of the deprecated ones:

func photoOutput(_ output: AVCapturePhotoOutput, didFinishProcessingPhoto photo: AVCapturePhoto, error: Error?) {
    guard error == nil else {
        print("Photo processing error: \(error!.localizedDescription)")
        return
    }

    // Extract and save JPEG data
    if let jpegData = photo.dataRepresentation(for: .jpeg) {
        saveToCameraRoll(imageData: jpegData, isRaw: false)
    }

    // Extract and save RAW (DNG) data
    if let rawData = photo.dataRepresentation(for: .dng) {
        saveToCameraRoll(imageData: rawData, isRaw: true)
    }
}

Step 3: Save to Camera Roll Using PHPhotoLibrary #

You’ll use PHPhotoLibrary to save the data to the user’s camera roll. Don’t forget to request photo library access first:

private func saveToCameraRoll(imageData: Data, isRaw: Bool) {
    // Request photo library access
    PHPhotoLibrary.requestAuthorization { authorizationStatus in
        guard authorizationStatus == .authorized else {
            print("Photo library access denied. Can't save image.")
            return
        }

        // Perform the save operation
        PHPhotoLibrary.shared().performChanges({
            let creationRequest = PHAssetCreationRequest.forAsset()
            creationRequest.addResource(with: .photo, data: imageData, options: nil)
        }, completionHandler: { success, error in
            DispatchQueue.main.async {
                if success {
                    print("\(isRaw ? "RAW (DNG)" : "JPEG") image saved to camera roll successfully!")
                } else {
                    print("Failed to save \(isRaw ? "RAW" : "JPEG") image: \(error?.localizedDescription ?? "Unknown error")")
                }
            }
        })
    }
}

Key Notes to Keep in Mind #

• Device Compatibility: RAW capture is supported on iPhone 6s and later, iPad Pro (all models), and some other newer iOS devices. Always check availableRawPhotoPixelFormatTypes before enabling RAW capture to avoid crashes.
• Permissions: Don’t forget to add the required privacy entries to your Info.plist:
  • NSCameraUsageDescription (explain why you need camera access)
  • NSPhotoLibraryAddUsageDescription (explain why you need to save to the photo library)
• Performance: RAW files are much larger than JPEGs, so make sure to handle memory usage appropriately, especially when capturing multiple RAW shots in a row.

内容的提问来源于stack exchange，提问作者Martin Tarrou