Saving file in android using Xamarin native. Pieced together from https://forums.xamarin.com/discussion/5409/photo-being-saved-in-landscape-not-portrait

DisplayImage

//usage
int height = Resources.DisplayMetrics.HeightPixels;
int width = _imageView.Height;

Bitmap bitmap = _file.Path.ResizeAndRotate(width, height);

ResizeAndRotate

public static Bitmap ResizeAndRotate(this string filePath, int width, int height)
{

  // First we get the the dimensions of the file on disk
  BitmapFactory.Options options = new BitmapFactory.Options { InJustDecodeBounds = true };
  
  
  // Next we calculate the ratio that we need to resize the image by
  // in order to fit the requested dimensions.
  int outHeight = options.OutHeight;
  int outWidth = options.OutWidth;
  int inSampleSize = 1;
  
  if (outHeight > height || outWidth > width)
  {
      inSampleSize = outWidth > outHeight
          ? outHeight / height
              : outWidth / width;
  }
  
  // Now we will load the image and have BitmapFactory resize it for us.
  options.InSampleSize = inSampleSize;
  options.InJustDecodeBounds = false;
  Bitmap resizedBitmap = BitmapFactory.DecodeFile(filePath, options);
  
  
  // Images are being saved in landscape, so rotate them back to portrait if they were taken in portrait
  Matrix mtx = new Matrix();
  ExifInterface exif = new ExifInterface(filePath);
  var orientation = (Android.Media.Orientation)exif.GetAttributeInt(ExifInterface.TagOrientation, (int)Android.Media.Orientation.Undefined);
  
  switch (orientation)
  {
      case Android.Media.Orientation.Undefined: // Nexus 7 landscape...
          break;
      case Android.Media.Orientation.Normal: // landscape
          break;
      case Android.Media.Orientation.FlipHorizontal:
          break;
      case Android.Media.Orientation.Rotate180:
          mtx.PreRotate(180);
          resizedBitmap = Bitmap.CreateBitmap(resizedBitmap, 0, 0, resizedBitmap.Width, resizedBitmap.Height, mtx, false);
          mtx.Dispose();
          mtx = null;
          break;
      case Android.Media.Orientation.FlipVertical:
          break;
      case Android.Media.Orientation.Transpose:
          break;
      case Android.Media.Orientation.Rotate90: // portrait
          mtx.PreRotate(90);
          resizedBitmap = Bitmap.CreateBitmap(resizedBitmap, 0, 0, resizedBitmap.Width, resizedBitmap.Height, mtx, false);
          mtx.Dispose();
          mtx = null;
          break;
      case Android.Media.Orientation.Transverse:
          break;
      case Android.Media.Orientation.Rotate270: // might need to flip horizontally too...
          mtx.PreRotate(270);
          resizedBitmap = Bitmap.CreateBitmap(resizedBitmap, 0, 0, resizedBitmap.Width, resizedBitmap.Height, mtx, false);
          mtx.Dispose();
          mtx = null;
          break;
      default:
          mtx.PreRotate(90);
          resizedBitmap = Bitmap.CreateBitmap(resizedBitmap, 0, 0, resizedBitmap.Width, resizedBitmap.Height, mtx, false);
          mtx.Dispose();
          mtx = null;
          break;
  }
  
  
  return resizedBitmap;
}