使用CALayers添加遮罩 [英] Adding a mask with CALayers

问题描述

我似乎很难通过CALayers添加面具。我只是试图掩盖UIImageView。这是我的代码：

I seem to be having difficulties adding a mask via CALayers. I'm simply trying to mask a UIImageView. Here's my code:

 CALayer *maskLayer = [CALayer layer];
 UIImage *mask = [UIImage imageNamed:@"mask.png"];
 maskLayer.contents = mask;

UIImageView *viewToMask = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 1024, 768)];
viewToMask.image = [UIImage imageNamed:@"picture.png"];
viewToMask.layer.mask = maskLayer;
[self.view addSubview:viewToMask];

Mask.png为黑色，透明圆圈穿过它（这是掩盖的正确方法吗？） 。我不知道这个失败的地方，也许在 maskLayer.contents 因为它应该是 CGImageRef 但是我当我将其设置为 mask.CGImage 时，或通过局部变量 CGImageRef = mask.CGImage 时出现错误。无论如何，它的设置现在不会出错，所以我希望它没问题。

Mask.png is black with a transparent circle punched through it (is this correct way to mask?). I'm not sure where this is failing, perhaps at maskLayer.contents since its supposed to be a CGImageRef but I get errors when I set it as mask.CGImage, or through a local variable CGImageRef = mask.CGImage. Anyway, the way its set now doesn't give errors, so I hope its fine.

有谁知道发生了什么，或者如何正确设置CALayers的面具？谢谢

Does anyone know what's going on, or how to properly set masks with CALayers? Thanks

推荐答案

尝试

maskLayer.contents = (id)mask.CGImage;

是的，演员很糟糕，但这是必要的。

Yes, the cast sucks, but it's necessary.

我想你还需要说

maskLayer.bounds = (CGRect){CGPointZero, mask.size};

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