无法在视图层中捕获蒙版 [英] Can't capture masks within view layer

问题描述

因此，我使用以下代码将图像蒙版应用于UIView层：

So I'm applying an image mask to a UIView layer with the following code:

CALayer *maskLayer = [CALayer layer];
UIImage *maskImage = self.image.image;
maskLayer.contents = (id)maskImage.CGImage;
maskLayer.frame = CGRectMake(0.0, 0.0,1235, 935);
self.bgView.layer.mask = maskLayer;

一切都很好，花哨的东西，遮罩覆盖了视图的内容并起作用。但是，我正在尝试截屏以使用户保存图像。我正在使用以下代码：

Everything is fine and dandy, the mask covers the view content and works. However, I am trying to take a screenshot to let the user save the image. I'm using the following code:

UIGraphicsBeginImageContext(captureFrame.size);
[self.bgView.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageWriteToSavedPhotosAlbum(viewImage, nil, nil, nil);

相框很好，可以保存到照片库中。唯一的问题是应用于该图层的蒙版没有显示在JPG中。我还尝试将bgView嵌套到另一个UIView中，然后尝试 renderInContext：，但这是相同的。看起来好像没有在最终的JPG中应用蒙版。

The frame is fine, and its saving to the photo library. The only problem is that the mask applied to the layer does not show up in the JPG. I have also tried nesting my bgView into another UIView, and then trying to renderInContext: that, but its the same thing. It simply appears as if the mask is not being applied in the final JPG.

有什么想法吗？谢谢。

推荐答案

很不幸，但这就是它的工作原理。 -[CALayer renderInContext：] 的文档说：

It's unfortunate, but that's just how it works. The documentation for -[CALayer renderInContext:] says:

...不会渲染使用3D变换的图层，也不会渲染指定backgroundFilters，filters，compositingFilter或mask值的图层。

... layers that use 3D transforms are not rendered, nor are layers that specify backgroundFilters, filters, compositingFilter, or a mask values.

CoreAnimation用于屏幕上的动画绘图；它不是通用图形框架。改为尝试使用CoreGraphics-没那么困难，您将拥有更多控制权，并且您可以获得更高质量的输出。

CoreAnimation is intended for on-screen, animated drawing; it isn't a general-purpose graphics framework. Try using CoreGraphics instead -- it isn't that difficult, you'll have more control, and you'll get higher-quality output.

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