我如何复制此图像裁剪器？的iOS

Question

我试图复制这种效果，但是在基于图像大小管理滚动视图插图时遇到了问题。

所需效果： Example 1 Example 2

很明显，代码只能使用在did select和didZoom中被调用的一个函数进行泛化，但是我试图使其工作。

这是我使用的代码：

带有约束的故事板

图像选择

 func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
    let asset = imageDataset[indexPath.item]
    let options = PHImageRequestOptions()
    options.isNetworkAccessAllowed = true
    options.isSynchronous = false
    options.deliveryMode = .highQualityFormat
    options.resizeMode = .exact

    let size = CGSize(width: CGFloat(asset.pixelHeight) , height: CGFloat(asset.pixelHeight))
    imageManager.requestImage(for: asset, targetSize: size , contentMode: .aspectFit, options:  options) { (image, _) in
        print(self.scrollView.zoomScale)
        self.imageView.image = image
        self.resetToOriginalState()
        if let image = self.imageView.image {

            let ratioW = self.imageView.frame.width / image.size.width
            let ratioH = self.imageView.frame.height / image.size.height

            let ratio = ratioW < ratioH ? ratioW : ratioH

            let newWidth = image.size.width * ratio
            let newHeight = image.size.height * ratio

            let left = 0.5 * (newWidth * self.scrollView.zoomScale > self.imageView.frame.width ? (newWidth - self.imageView.frame.width) : (self.scrollView.frame.width - self.scrollView.contentSize.width))
            let top = 0.5 * (newHeight * self.scrollView.zoomScale > self.imageView.frame.height ? (newHeight - self.imageView.frame.height) : (self.scrollView.frame.height - self.scrollView.contentSize.height))

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

        }else {
            self.scrollView.contentInset = UIEdgeInsets.zero
        }
        if !self.isImageShown {
            collectionView.scrollToItem(at: indexPath, at: .top, animated: true)
        }
    }
}

ScrollView委托

 func scrollViewDidZoom(_ scrollView: UIScrollView) {
    print(scrollView.zoomScale)
    if scrollView.zoomScale > 1 {
        if let image = imageView.image {

            let ratioW = imageView.frame.width / image.size.width
            let ratioH = imageView.frame.height / image.size.height

            let ratio = ratioW < ratioH ? ratioW : ratioH

            let newWidth = image.size.width * ratio
            let newHeight = image.size.height * ratio

            var left = 0.5 * (newWidth * scrollView.zoomScale > imageView.frame.width ? (newWidth - imageView.frame.width) : (scrollView.frame.width - scrollView.contentSize.width))
            let top = 0.5 * (newHeight * scrollView.zoomScale > imageView.frame.height ? (newHeight - imageView.frame.height) : (scrollView.frame.height - scrollView.contentSize.height))
            scrollView.contentInset = UIEdgeInsets(top: top, left: left, bottom: top, right:  left)
        }
    }else {
        scrollView.contentInset = UIEdgeInsets.zero
    }
}


   func viewForZooming(in scrollView: UIScrollView) -> UIView? {
    return self.imageView
   }