在drawRect中使用iOS反转掩码

Question

使用下面的代码,我成功地屏蔽了我绘图的一部分,但它与我想要屏蔽的相反.这掩盖了绘图的内部,我想掩盖外部.有一种简单的方法来反转这个面具吗？

myPath下面是一个UIBezierPath.

CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];
CGMutablePathRef maskPath = CGPathCreateMutable();
CGPathAddPath(maskPath, nil, myPath.CGPath);
[maskLayer setPath:maskPath];
CGPathRelease(maskPath);
self.layer.mask = maskLayer;

Answer 1

即使在形状图层(maskLayer.fillRule = kCAFillRuleEvenOdd;)上进行奇数填充,您也可以添加一个覆盖整个框架的大矩形,然后添加要遮罩的形状.这实际上会反转掩模.

CAShapeLayer *maskLayer = [[CAShapeLayer alloc] init];
CGMutablePathRef maskPath = CGPathCreateMutable();
CGPathAddRect(maskPath, NULL, someBigRectangle); // this line is new
CGPathAddPath(maskPath, nil, myPath.CGPath);
[maskLayer setPath:maskPath];
maskLayer.fillRule = kCAFillRuleEvenOdd;         // this line is new
CGPathRelease(maskPath);
self.layer.mask = maskLayer;

Answer 2

对于Swift 3.0

func mask(viewToMask: UIView, maskRect: CGRect, invert: Bool = false) {
    let maskLayer = CAShapeLayer()
    let path = CGMutablePath()
    if (invert) {
        path.addRect(viewToMask.bounds)
    }
    path.addRect(maskRect)

    maskLayer.path = path
    if (invert) {
        maskLayer.fillRule = kCAFillRuleEvenOdd
    }

    // Set the mask of the view.
    viewToMask.layer.mask = maskLayer;
}

Answer 3

基于接受的答案,这是Swift中的另一个混搭.我把它变成了一个函数,并使其成为invert可选的

class func mask(viewToMask: UIView, maskRect: CGRect, invert: Bool = false) {
    let maskLayer = CAShapeLayer()
    let path = CGPathCreateMutable()
    if (invert) {
        CGPathAddRect(path, nil, viewToMask.bounds)
    }
    CGPathAddRect(path, nil, maskRect)

    maskLayer.path = path
    if (invert) {
        maskLayer.fillRule = kCAFillRuleEvenOdd
    }

    // Set the mask of the view.
    viewToMask.layer.mask = maskLayer;
}

Answer 4

这是我的 Swift 4.2 解决方案，它允许圆角半径

extension UIView {

    func mask(withRect maskRect: CGRect, cornerRadius: CGFloat, inverse: Bool = false) {
        let maskLayer = CAShapeLayer()
        let path = CGMutablePath()
        if (inverse) {
            path.addPath(UIBezierPath(roundedRect: self.bounds, cornerRadius: cornerRadius).cgPath)
        }
        path.addPath(UIBezierPath(roundedRect: maskRect, cornerRadius: cornerRadius).cgPath)

        maskLayer.path = path
        if (inverse) {
            maskLayer.fillRule = CAShapeLayerFillRule.evenOdd
        }

        self.layer.mask = maskLayer;
    }

}

Answer 5

斯威夫特 5

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        let red = UIView(frame: view.bounds)
        view.addSubview(red)
        view.backgroundColor = UIColor.cyan
        red.backgroundColor = UIColor.red
        red.mask(CGRect(x: 50, y: 50, width: 50, height: 50), invert: true)
    }
}

extension UIView{

    func mask(_ rect: CGRect, invert: Bool = false) {
        let maskLayer = CAShapeLayer()
        let path = CGMutablePath()
        if (invert) {
            path.addRect(bounds)
        }
        path.addRect(rect)
        maskLayer.path = path
        if (invert) {
            maskLayer.fillRule = CAShapeLayerFillRule.evenOdd
        }
        // Set the mask of the view.
        layer.mask = maskLayer
    }
}

谢谢@arvidurs