Question

[[[globalSingleton paintingView] drawingView] setOpaque:NO];
[[[[globalSingleton paintingView] drawingView] layer] setOpaque:NO];    
[[[globalSingleton paintingView] drawingView] setBackgroundColor:[UIColor clearColor]];
[[[[globalSingleton paintingView] drawingView] layer] setBackgroundColor:[UIColor clearColor].CGColor];

[[[[globalSingleton paintingView] drawingView] layer] renderInContext:ctx];

UIImage *image1 = UIGraphicsGetImageFromCurrentImageContext();

上面的代码就是我用来将'drawingView'保存到png文件中的代码。我发现了几个问题和答案，所以我应用了它们。我将'drawingView'和drawingView.layer的不透明设置为NO，并将我的'drawingView'的背景颜色设置为[UIColor clearColor]。我想我应用了stackoverflow的所有答案。然而，没有任何改变。 png fil的背景仍然是黑色的。我需要透明的背景，而不是黑色!!

我试过UIImage * image1是否有任何问题。我使用image1在屏幕上显示，然后我可以从该image1找到黑色背景。所以我猜可能在创建image1时有任何问题。

这就是我发现的全部内容。是否有任何可能的解决方案来保存我的透明背景图像的png图像？在此先感谢!!

Answer 1

哦，天啊！我做的！！我添加了[[UIColor clearColor] set]; 。就是这样。

UIGraphicsBeginImageContextWithOptions(screenRect.size, NO, [[UIScreen mainScreen] scale]);

CGContextRef ctx = UIGraphicsGetCurrentContext();
[[UIColor clearColor] set];
CGContextFillRect(ctx, screenRect);

[[[globalSingleton paintingView] drawingView] setOpaque:NO];
[[[[globalSingleton paintingView] drawingView] layer] setOpaque:NO];    
[[[globalSingleton paintingView] drawingView] setBackgroundColor:[UIColor clearColor]];
[[[[globalSingleton paintingView] drawingView] layer] setBackgroundColor:[UIColor clearColor].CGColor];

[[[[globalSingleton paintingView] drawingView] layer] renderInContext:ctx]; 

UIImage *image1 = UIGraphicsGetImageFromCurrentImageContext();

Answer 2

Swift 4.2版本：

extension UIView {

func saveAsImage()-> UIImage? {
    UIGraphicsBeginImageContext(self.bounds.size)
    guard let context = UIGraphicsGetCurrentContext() else { return nil }

    UIColor.clear.set()
    context.fill(self.bounds)

    self.isOpaque = false
    self.layer.isOpaque = false
    self.backgroundColor = UIColor.clear
    self.layer.backgroundColor = UIColor.clear.cgColor

    self.layer.render(in: context)
    let image = UIGraphicsGetImageFromCurrentImageContext()

    return image
}
}

将UIView保存为透明背景的png文件

2 个答案: