Swift - 截取当前屏幕

    func takeScreenshot() -> UIImage
    {
        var imageSize = CGSize.zero
        let screenSize = UIScreen.main.bounds.size
        let orientation = UIApplication.shared.statusBarOrientation
        if UIInterfaceOrientationIsPortrait(orientation)
        {
            imageSize = screenSize
        }
        else
        {
            imageSize = CGSize(width: screenSize.height, height: screenSize.width)
        }
        
        UIGraphicsBeginImageContextWithOptions(imageSize, false, 0)
        
        if let context = UIGraphicsGetCurrentContext()
        {
            for window in UIApplication.shared.windows
            {
                context.saveGState()
                context.translateBy(x: window.center.x, y: window.center.y)
                context.concatenate(window.transform)
                context.translateBy(x: -window.bounds.size.width * window.layer.anchorPoint.x, y: -window.bounds.size.height * window.layer.anchorPoint.y)
                
                if orientation == UIInterfaceOrientation.landscapeLeft {
                    context.rotate(by: .pi / 2)
                    context.translateBy(x: 0, y: -imageSize.width)
                }
                else if orientation == UIInterfaceOrientation.landscapeRight
                {
                    context.rotate(by: -.pi / 2)
                    context.translateBy(x: -imageSize.height, y: 0)
                }
                else if orientation == UIInterfaceOrientation.portraitUpsideDown
                {
                    context.rotate(by: .pi)
                    context.translateBy(x: -imageSize.width, y: -imageSize.height)
                }
                if window.responds(to: #selector(UIView.drawHierarchy(in:afterScreenUpdates:)))
                {
                    window.drawHierarchy(in: window.bounds, afterScreenUpdates: true)
                }
                else
                {
                    window.layer.render(in: context)
                }
                context.restoreGState()
            }
        }
        
        let image = UIGraphicsGetImageFromCurrentImageContext()
        
        UIGraphicsEndImageContext()
        
        if let image = image
        {
            return image
        }
        else
        {
            return UIImage()
        }
    }