迅速UIGraphicsGetImageFromCurrentImageContext不能釋放內存

Question

Swift代碼

當我們拿到一個UIView的截圖中，我們使用此代碼通常是：

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

問題

drawViewHierarchyInRect & & UIGraphicsGetImageFromCurrentImageContext將產生圖像在當前上下文中，但內存將而不是發佈時稱爲UIGraphicsEndImageContext。

內存使用持續增加，直到應用程序崩潰。

雖然有一句話UIGraphicsEndImageContext會自動調用CGContextRelease」，這是行不通的。

我如何可以釋放drawViewHierarchyInRect或UIGraphicsGetImageFromCurrentImageContext使用

還是？

有反正產生記憶屏幕截圖沒有drawViewHierarchyInRect？

已經嘗試

1自動釋放：不行

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

2 UnsafeMutablePointer：不行

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

我通過把圖像操作在另一個隊列解決了這個問題！

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) 
    } 
} 

Answer 2

private extension UIImage 
{ 
func resized() -> UIImage { 
let height: CGFloat = 800.0 
let ratio = self.size.width/self.size.height 
let width = height * ratio 

let newSize = CGSize(width: width, height: height) 
let newRectangle = CGRect(x: 0, y: 0, width: width, height: height) 

UIGraphicsBeginImageContext(newSize) 
self.draw(in: newRectangle) 

let resizedImage = UIGraphicsGetImageFromCurrentImageContext() 
UIGraphicsEndImageContext() 

return resizedImage! 
} 
}