下面是一个基于@Dima的答案的Swift 4 UIView扩展。

extension UIView {
   func snapshotImage() -> UIImage? {
       UIGraphicsBeginImageContextWithOptions(bounds.size, isOpaque, 0)
       drawHierarchy(in: bounds, afterScreenUpdates: false)
       let image = UIGraphicsGetImageFromCurrentImageContext()
       UIGraphicsEndImageContext()
       return image
   }
}

插入式Swift 3.0扩展，支持新的iOS 10.0 API和以前的方法。

注意:

iOS版本检查 注意使用defer来简化上下文清理。 还将应用视图的不透明度和当前比例。 没有任何东西只是使用!这可能会导致坠机。

extension UIView
{
    public func renderToImage(afterScreenUpdates: Bool = false) -> UIImage?
    {
        if #available(iOS 10.0, *)
        {
            let rendererFormat = UIGraphicsImageRendererFormat.default()
            rendererFormat.scale = self.layer.contentsScale
            rendererFormat.opaque = self.isOpaque
            let renderer = UIGraphicsImageRenderer(size: self.bounds.size, format: rendererFormat)

            return
                renderer.image
                {
                    _ in

                    self.drawHierarchy(in: self.bounds, afterScreenUpdates: afterScreenUpdates)
                }
        }
        else
        {
            UIGraphicsBeginImageContextWithOptions(self.bounds.size, self.isOpaque, self.layer.contentsScale)
            defer
            {
                UIGraphicsEndImageContext()
            }

            self.drawHierarchy(in: self.bounds, afterScreenUpdates: afterScreenUpdates)

            return UIGraphicsGetImageFromCurrentImageContext()
        }
    }
}

使用现代的uigraphicsimagerender

public extension UIView {
    @available(iOS 10.0, *)
    public func renderToImage(afterScreenUpdates: Bool = false) -> UIImage {
        let rendererFormat = UIGraphicsImageRendererFormat.default()
        rendererFormat.opaque = isOpaque
        let renderer = UIGraphicsImageRenderer(size: bounds.size, format: rendererFormat)

        let snapshotImage = renderer.image { _ in
            drawHierarchy(in: bounds, afterScreenUpdates: afterScreenUpdates)
        }
        return snapshotImage
    }
}

斯威夫特2.0:

使用扩展方法:

extension UIImage{

   class func renderUIViewToImage(viewToBeRendered:UIView?) -> UIImage
   {
       UIGraphicsBeginImageContextWithOptions((viewToBeRendered?.bounds.size)!, false, 0.0)
       viewToBeRendered!.drawViewHierarchyInRect(viewToBeRendered!.bounds, afterScreenUpdates: true)
       viewToBeRendered!.layer.renderInContext(UIGraphicsGetCurrentContext()!)

       let finalImage = UIGraphicsGetImageFromCurrentImageContext()
       UIGraphicsEndImageContext()

       return finalImage
   }

}

用法:

override func viewDidLoad() {
    super.viewDidLoad()

    //Sample View To Self.view
    let sampleView = UIView(frame: CGRectMake(100,100,200,200))
    sampleView.backgroundColor =  UIColor(patternImage: UIImage(named: "ic_120x120")!)
    self.view.addSubview(sampleView)    

    //ImageView With Image
    let sampleImageView = UIImageView(frame: CGRectMake(100,400,200,200))

    //sampleView is rendered to sampleImage
    var sampleImage = UIImage.renderUIViewToImage(sampleView)

    sampleImageView.image = sampleImage
    self.view.addSubview(sampleImageView)

 }

- (UIImage*)screenshotForView:(UIView *)view
{
    UIGraphicsBeginImageContext(view.bounds.size);
    [view.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    // hack, helps w/ our colors when blurring
    NSData *imageData = UIImageJPEGRepresentation(image, 1); // convert to jpeg
    image = [UIImage imageWithData:imageData];

    return image;
}

Swift 3.0实现

extension UIView {
    func getSnapshotImage() -> UIImage {
        UIGraphicsBeginImageContextWithOptions(bounds.size, isOpaque, 0)
        drawHierarchy(in: bounds, afterScreenUpdates: false)
        let snapshotImage = UIGraphicsGetImageFromCurrentImageContext()!
        UIGraphicsEndImageContext()
        return snapshotImage
    }
}