使用Swift在iOS上本地保存和检索照片及其所有元数据

Question

I am currently taking photos from the users iPhone making them jpegs, then saving them using file Manager and then saving their paths with core data.

The way I do it I can't show live images or later export the image with its previous meta data.

My question is what is the correct way to save an image locally with all its meta data and live status so it can be displayed and exported later but only inside the app. I don't want the images to be viable outside the application.

Answer 1

Taking The image:

Take a look at the UIImagePickerController class and use it to take pictures. Taking pictures with this, will NOT save the images automatically to the iOS gallery.

The mentioned UIImagePickerController will notify a delegate UIImagePickerControllerDelegate and call the function func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String: Any]) .

From the second parameter, the info dictionary, you can request most of the images metadata, livePhoto and so on. The necessary keys can be found inside the extension of UIImagePickerController called UIImagePickerController.InfoKey .

For example, here is how I then retrieve the images coordinate if available:

if let imageURL = info[UIImagePickerControllerReferenceURL] as? URL {
      let result = PHAsset.fetchAssets(withALAssetURLs: [imageURL], options: nil)
      if let asset = result.firstObject, let location = asset.location {
          let lat = location.coordinate.latitude
          let lon = location.coordinate.longitude
          print("Here's the lat and lon \(lat) + \(lon)")
      }
}

Saving the image onto the phone within your app?:

I use JSONEncoder . You can use this class to encode and then decode your custom image class again.

Your custom image class, which has the UIImage and all the other properties must then implement the Codable protocol. Afterwards, use the JSONEncoder to create Data of the object via its encode() method and save it to an app private location with the help of a FileManager . Later on, you may read all files from that location again with the FileManager , decode() with the JSONEncoder and voila you have all your images again in the form of your custom image class.

Saving the image to the users gallery "Exporting":

Here's an example of how I again save that image to the users gallery as a way of exporting it:

private static func saveImageToGallery(picture: UIImage, lat: Double?, lon: Double?) {
            PHPhotoLibrary.shared().performChanges({
                let request = PHAssetCreationRequest.creationRequestForAsset(from: picture)
                if let _lat = lat, let _lon = lon {
                    request.location = CLLocation(latitude: _lat, longitude: _lon)
                }
            })
        }

I hope this will be enough to guide you to the correct way.