在缩放过程中防止图像尺寸减小小于100％

Question

我的UIImageView包含在UIScrollView中。

scrollView.minimumZoomScale = 1.0

当我尝试缩小图像时，图像的大小等于50％。 当我移开手指时，图像的大小再次等于100％。

如何在缩放过程中防止缩小小于100％？

override func awakeFromNib() {
    super.awakeFromNib()
    scrollView.delegate = self
    scrollView.addSubview(imgView)
    scrollView.minimumZoomScale = 1.0
    scrollView.maximumZoomScale = 5.0
    scrollView.zoomScale = 1.0        
    centerScrollViewContents()
}

func centerScrollViewContents() {
    let boundsSize = scrollView.bounds.size
    var contentsFrame = imgView.frame

    if contentsFrame.size.width < boundsSize.width {
        contentsFrame.origin.x = (boundsSize.width - contentsFrame.size.width) / 2.0
    } else {
        contentsFrame.origin.x = 0.0
    }

    if contentsFrame.size.height < boundsSize.height {
        contentsFrame.origin.y = (boundsSize.height - contentsFrame.size.height) / 2.0
    } else {
        contentsFrame.origin.y = 0.0
    }

    imgView.frame = contentsFrame
}