ios - swift UIGraphicsGetImageFromCurrentImageContext 无法释放内存

Question

快速代码

当我们获取一个UIView的截图时，我们通常会使用这段代码:

UIGraphicsBeginImageContextWithOptions(frame.size, false, scale)
drawViewHierarchyInRect(bounds, afterScreenUpdates: true)
var image:UIImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()

问题

drawViewHierarchyInRect && UIGraphicsGetImageFromCurrentImageContext 将在当前 Context 中生成图像，但调用 UIGraphicsEndImageContext 时内存将不会释放>.

内存使用持续增加，直到应用崩溃。

虽然有一句话UIGraphicsEndImageContext会自动调用CGContextRelease”，但它不起作用。

如何释放内存 drawViewHierarchyInRect 或 UIGraphicsGetImageFromCurrentImageContext 使用

或者？

有没有不用drawViewHierarchyInRect生成截图的方法？

已经尝试过

1 Auto release : not work

var image:UIImage?
autoreleasepool{
    UIGraphicsBeginImageContextWithOptions(frame.size, false, scale)
    drawViewHierarchyInRect(bounds, afterScreenUpdates: true)
    image = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()
}
image = nil

2 UnsafeMutablePointer : not work

var image:UnsafeMutablePointer<UIImage> = UnsafeMutablePointer.alloc(1)

autoreleasepool{
   UIGraphicsBeginImageContextWithOptions(frame.size, false, scale)
   drawViewHierarchyInRect(bounds, afterScreenUpdates: true)
   image.initialize(UIGraphicsGetImageFromCurrentImageContext())
   UIGraphicsEndImageContext()
}
image.destroy()
image.delloc(1)

Answer 1

我通过将图像操作放在另一个队列中解决了这个问题!

private func processImage(image: UIImage, size: CGSize, completion: (image: UIImage) -> Void) {
    dispatch_async(dispatch_get_global_queue(Int(QOS_CLASS_USER_INITIATED.rawValue), 0)) {
        UIGraphicsBeginImageContextWithOptions(size, true, 0)
        image.drawInRect(CGRect(origin: CGPoint.zero, size: size))
        let tempImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()

        completion(image: tempImage)
    }
}