CALayer創建透明圓形面具

Question

我想創建一個遮罩層，這是一個圓圈，使圓圈內容透明，並保持周圍的一切。 不幸的是，下面的代碼恰恰相反，它繪制了一個圓圈並使一切變得透明。

CAShapeLayer * shape = [CAShapeLayer layer];
shape.frame          = CGRectMake((CGSSize().width/2.f)-40.f, -40.f, 80.f, 80.f);

CGPathRef pathRef    =
CGPathCreateWithEllipseInRect(CGRectMakeBoundsWithSize(shape.frame.size), NULL);

shape.path            = pathRef;
shape.fillColor       = [UIColor blueColor].CGColor;

self.layer.mask = shape;

Answer 1

是的，kCAFillRuleEvenOdd在沒有首先添加rect的情況下沒有做到這一點，這里有一個工作片段：

CAShapeLayer *shape = [CAShapeLayer layer];

shape.frame = self.bounds;

CGMutablePathRef pathRef = CGPathCreateMutable();
CGPathAddRect(pathRef, NULL, self.bounds);
CGPathAddEllipseInRect(pathRef, NULL, self.bounds);

shape.fillRule = kCAFillRuleEvenOdd;
shape.path = pathRef;

self.layer.mask = shape;