如何使用扩展功能保存分层图像

Question

我正在使用扩展函数将uiview保存为uiimage。该代码用于保存 uiimage。但是，我正在尝试做的是在要保存到照片库的图像上保存透明图像。所以我正在尝试使用扩展函数保存分层图像。现在只有 uiivew 被保存，而第 2 层没有被保存。

class ViewController: UIViewController,UINavigationControllerDelegate {
@IBAction func press(_ sender: Any) {
let jake = drawingView.takeSnapshotOfView(view: drawingView)
guard let selectedImage = jake else {
print("Image not found!")
return
}
UIImageWriteToSavedPhotosAlbum(selectedImage, self, #selector(image(_:didFinishSavingWithError:contextInfo:)), nil)
}}
func takeSnapshotOfView(view:UIView) -> UIImage? {
UIGraphicsBeginImageContext(CGSize(width: view.frame.size.width, height: view.frame.size.height))
view.drawHierarchy(in: CGRect(x: 0.0, y: 0.0, width: view.frame.size.width, height: view.frame.size.height), afterScreenUpdates: true)

let image = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
let star:UIImage = UIImage(named: "e.png")!
let newSize = CGSize(width: star.size.width, height: star.size.height  )
UIGraphicsBeginImageContextWithOptions(newSize, false, star.scale)
star.draw(in: CGRect(x: newSize.width/12,
y: newSize.height/8,
width: newSize.width/1.2,
height: newSize.height/1.2),
blendMode:CGBlendMode.normal, alpha:1)


UIGraphicsEndImageContext()
return image
}

Answer 1

这是一个UIView扩展，它接受CGRect和UIImage，或者你也可以为它提供另一个CGRect或CGSize，使其对水印放置/大小更加动态。

extension UIView {        
/// Takes a screenshot of a UIView, with an option to clip to view bounds and place a waterwark image 
/// - Parameter rect: offset and size of the screenshot to take
/// - Parameter clipToBounds: Bool to check where self.bounds and rect intersect and adjust size so there is no empty space
/// - Parameter watermark: UIImage of the watermark to place on top
func screenshot(for rect: CGRect, clipToBounds: Bool = true, with watermark: UIImage? = nil) -> UIImage {
var imageRect = rect
if clipToBounds {
imageRect = bounds.intersection(rect)
}
return UIGraphicsImageRenderer(bounds: imageRect).image { _ in
drawHierarchy(in: CGRect(origin: .zero, size: bounds.size), afterScreenUpdates: true)
watermark?.draw(in: CGRect(origin: imageRect.origin, size: CGSize(width: 32, height: 32))) // update origin to place watermark where you want, with this update it will place it in top left or screenshot.
}
}
}

你可以这样称呼它：

let image = self.view.screenshot(for: CGRect(x: 0, y: 0, width: 200, height: 200), with: UIImage(named: "star"))

这将适用于调用屏幕截图的视图的所有子视图(...

对于使用上述扩展的任何人，我在此答案中添加了其他信息