Ios 如何在Swift中按图像大小调整UIImageView的大小

我想使用缩放增加图像。我做了这个，做了那个，会等于图片的字体大小，但我还是用上面的背景像这样改变吗？我怎样才能做到

viewDidLoad中的My imageView

    imageView = UIImageView(frame: CGRect(x: 0, y: 0, width: self.view.frame.width, height: self.view.frame.height))
    imageView.backgroundColor = .greenColor()
    imageView.image = UIImage(contentsOfFile: document.documentImageURL)
    imageView.autoresizingMask = [.FlexibleWidth, .FlexibleHeight] //


   func setZoomScale() {
    let widthRatio = imageView.bounds.size.width / (imageView.image?.size.width)!
    let heightRatio = imageView.bounds.size.height / (imageView.image?.size.height)!
    let scale = min(widthRatio, heightRatio)
    let imageWidth = scale * (imageView.image?.size.width)!
    let imageHeight = scale * (imageView.image?.size.height)!
    imageView.frame = CGRect(x: 0, y: 0, width: imageWidth, height: imageHeight)
}

我就是这样做的

    override func viewDidLoad() {
    super.viewDidLoad()

    let image = UIImage(contentsOfFile: document.documentImageURL)
    imageView = UIImageView(image: image)
    imageView.autoresizingMask = [.FlexibleWidth, .FlexibleHeight]

    scrollView = UIScrollView(frame: view.bounds)
    scrollView.delegate = self
    scrollView.backgroundColor = UIColor(red: 129/255.0, green: 130/255.0, blue: 130/255.0, alpha: 1.0)
    scrollView.autoresizingMask = [.FlexibleWidth, .FlexibleHeight]
    scrollView.showsHorizontalScrollIndicator = false
    scrollView.showsVerticalScrollIndicator = false
    scrollView.addSubview(imageView)
    view.addSubview(scrollView)
    newZoomScale()
    scrollView.setZoomScale(scrollView.minimumZoomScale, animated: false)
    setGesture()
    setNavigationBar()
}

private func newZoomScale() {
    let imageViewSize = imageView.bounds.size
    let scrollViewSize = scrollView.bounds.size
    let widthScale = scrollViewSize.width / imageViewSize.width
    let heightScale = scrollViewSize.height / imageViewSize.height
    scrollView.minimumZoomScale = min(widthScale, heightScale)
    scrollView.zoomScale = 1.0
}

func scrollViewDidZoom(scrollView: UIScrollView) {
        let imageViewSize = imageView.frame.size
        let scrollViewSize = scrollView.bounds.size

        let verticalPadding = imageViewSize.height < scrollViewSize.height ? (scrollViewSize.height - imageViewSize.height) / 2 : 0
        let horizontalPadding = imageViewSize.width < scrollViewSize.width ? (scrollViewSize.width - imageViewSize.width) / 2 : 0

        self.scrollView.contentInset = UIEdgeInsets(top: verticalPadding, left: horizontalPadding, bottom: verticalPadding, right: horizontalPadding)
    }

override func viewDidLoad（）{
super.viewDidLoad（）
让image=UIImage（contentsOfFile:document.documentImageURL）
imageView=UIImageView（图像：图像）
imageView.autoresizingMask=[.FlexibleWidth、.FlexibleHeight]
scrollView=UIScrollView（框架：view.bounds）
scrollView.delegate=self
scrollView.backgroundColor=UIColor（红色：129/255.0，绿色：130/255.0，蓝色：130/255.0，alpha:1.0）
scrollView.autoresizingMask=[.FlexibleWidth、.FlexibleHeight]
scrollView.showsHorizontalScrollIndicator=false
scrollView.showsVerticalScrollIndicator=false
scrollView.addSubview（imageView）
view.addSubview（滚动视图）
newzoomsale（）
scrollView.setZoomScale（scrollView.minimumZoomScale，动画：false）
设置手势（）
setNavigationBar（）
}
私有func newzoomsale（）{
让imageViewSize=imageView.bounds.size
让scrollViewSize=scrollView.bounds.size
让widthScale=scrollViewSize.width/imageViewSize.width
设heightScale=scrollViewSize.height/imageViewSize.height
scrollView.minimumZoomScale=min（宽度刻度、高度刻度）
scrollView.zoomScale=1.0
}
func scrollViewDidZoom（scrollView:UIScrollView）{
让imageViewSize=imageView.frame.size
让scrollViewSize=scrollView.bounds.size
让verticalPadding=imageViewSize.height