I only get the thumbnail from a DNG/TIFF file

I am able to read the DNG-file as a PHAssetResource and getting the NSData through PHAssetResourceManager.requestDataForAssetResource.

The NSData holds the same amount of bytes as the filesize indicates.

However, when I do UIImage(data:myLoadedData) only a very low rez thumb is loaded.

I have tried the following :

- using CGImageSourceCreateWithData and converting it back into an UIImage via CGImageSourceCreateImageAtIndex

- the CGImageSourceGetCount( imageSource) returns 1 so there is only one image in there, not counting the thumb

- saving the NSData to the documents folderand reading it witn NSImage(contentsOfFile) (the saved file is a valid DNG and TIFF when I download the app package to my mac through the Device Manager)

The PHAssetResource.uniformTypeIdentifier reports the file as "com.adobe.raw-image"

I get the same result with DNG-files from two different cameras, both the Leica M typ240, and the Leica Monochrom (first edition)

There is a difference in thumbnail size, but I am not able to view the full resolution image.

Loading large jpeg's or PNGs works fine.

The "app" is running on an iPad Pro iOS 9.3

What am I missing here?

Any tips would be greatly appreciated.

Below is the code, from the UIImagePickerController returns with a selected image URL

    func imagePickerController(picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : AnyObject]) {
      
        dismissViewControllerAnimated(true, completion: nil)
      
        let url = info[UIImagePickerControllerReferenceURL] as! NSURL
        getUIImagefromAsseturl(url)
      
    }
  
  
    func getUIImagefromAsseturl (url: NSURL) {
      
        let resourceManager = PHAssetResourceManager.defaultManager()
      
        let asset = PHAsset.fetchAssetsWithALAssetURLs([url], options: nil)[0]
      
        let assetResource = PHAssetResource.assetResourcesForAsset(asset as! PHAsset)[0]
      
      
        let totalData = NSMutableData()
      
        resourceManager.requestDataForAssetResource(assetResource, options: nil, dataReceivedHandler:
            { (data) in
              
                totalData.appendData( data )
                print( "data.length \(data.length) \(totalData.length)" )
              
            }, completionHandler: { (error) in
                if error != nil {
                    print( "error: \(error)" )
                }
                else {
                  
                    /* totalData contains the entire byte buffer from the file */
                    let image = UIImage(data: totalData)
                    /* image contains puny thumbnail */
                  
                    dispatch_async(dispatch_get_main_queue(), {
                        self.imageView.contentMode = .ScaleAspectFit
                        self.imageView.image = image
                    })
                }
        })
      
      
    }