     fileprivate var __zoomOutTapEnabled: Bool = true
     fileprivate var _centerHorizontally: Bool = true
     fileprivate var _centerVertically: Bool = true
+    fileprivate var _maximumZoomScale: CGFloat = 1
     fileprivate var _doubleTapNextScale: CGFloat?
 
     

            self._scrollView.zoomOut(animated: false)
        } else if currentZoomScale > maxScale {
            self._scrollView.zoomIn(animated: false)
        }
    }
}

        
        let threshold: CGFloat = self._zoomThreshold
        let belowThreshold: Bool = exactMinScale < threshold
        let maxScale: CGFloat = belowThreshold ? 1 : min(exactMinScale, self._maximumZoomScale)
        
        scrollView.minimumZoomScale = exactMinScale
        scrollView.maximumZoomScale = maxScale
