如何从A中减去UIBezierPath A和B的交点?

让我向你展示我所做的尝试,并告诉我对你有多有用。

首先,我创建了一个自定义视图类,我在其中编写了绘制视图的代码。请参阅以下代码:

class MyCustomView: UIView {

    override init(frame: CGRect) {
        super.init(frame: frame)
        setup()
    }

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        setup()
    }

    func setup() {

        // Create a CAShapeLayer
        let shapeLayer = CAShapeLayer()

        let path1 = self.path1()
        let path2 = self.path2()

        // Append path2 to path1
        path1.append(path2.reversing())

        // Set true of Even Odd Fill Rule
        path1.usesEvenOddFillRule = true

        // Call this method to add clip in path
        path1.addClip()

        shapeLayer.path = path1.cgPath

        // Apply other properties related to the path
        shapeLayer.strokeColor = UIColor.blue.cgColor
        shapeLayer.fillColor = UIColor.black.cgColor
        shapeLayer.lineWidth = 1.0
        shapeLayer.position = CGPoint(x: 0, y: 0)

        // Add the new layer to our custom view
        self.layer.addSublayer(shapeLayer)
    }

    //-----------------------------------------------------
    // This is static code as I have already told you first.
    // Create First UIBezierPath,

    func path1() -> UIBezierPath {
        let path = UIBezierPath()
        path.move(to: CGPoint(x: 0, y: 0))
        path.addLine(to: CGPoint(x: 0, y: 200))
        path.addLine(to: CGPoint(x: 200, y: 200))
        path.addLine(to: CGPoint(x: 200, y: 0))
        path.close()
        return path
    }

    // Create Second UIBezierPath
    func path2() -> UIBezierPath {
        let path = UIBezierPath()
        path.move(to: CGPoint(x: 50, y: -50))
        path.addLine(to: CGPoint(x: 50, y: 150))
        path.addLine(to: CGPoint(x: 250, y: 150))
        path.addLine(to: CGPoint(x: 250, y: -50))
        path.close()
        return path
    }
}

真实的

现在,为了使用这个类,我创建了上述类的固定高度的实例&宽度

override func viewDidLoad() {
    super.viewDidLoad()

    // Create a new UIView and add it to the view controller
    let myView = MyCustomView()

    // Must set clipsToBounds true to remove extra layer which are display out side of view as like your **actual** result in figure 4.
    myView.clipsToBounds = true 
    myView.frame = CGRect(x: 50, y: 100, width: 200, height: 200)
    myView.backgroundColor = UIColor.orange
    view.addSubview(myView)
}

这将显示以下视图,这是您所需的结果。

作为iOS上的新路径,没有直接的方法可以获得UIBezierPath的差异。

测试向量

private func path2() -> UIBezierPath {
    return UIBezierPath(rect: CGRect(x: 100, y: 50, width: 200, height: 200))
}

private func path1() -> UIBezierPath {
    return UIBezierPath(rect: CGRect(x: 50, y: 100, width: 200, height: 200))
}

起点:仅显示哪个路径代表什么:路径1为黄色,路径2为绿色:

可能性1

代码取自此答案(来自您发布的链接) https://stackoverflow.com/a/8860341 -仅转换为Swift:

func fillDifference(path2: UIBezierPath, path1: UIBezierPath) {
    let clipPath = UIBezierPath.init(rect: .infinite)
    clipPath.append(path2)
    clipPath.usesEvenOddFillRule = true

    UIGraphicsGetCurrentContext()?.saveGState()
    clipPath.addClip()
    path1.fill()
    UIGraphicsGetCurrentContext()?.restoreGState()
}

看起来是这样的:

您可以使用第三方库,例如作者Adam Wulf提供的库: https://github.com/adamwulf/ClippingBezier

该库是用Objective-C编写的,但可以从Swift调用。

override func draw(_ rect: CGRect) {
    let result = self.path1().difference(with: self.path2())

    for p in result ?? [] {
        p.stroke()
    }
}

如果您想使用这个库,您必须注意一个小提示:在项目设置中的其他链接器标志中,如自述文件所述,“-ObjC++-lstdc++”必须添加,否则它将毫无怨言地构建,但不会加载框架并最终崩溃,因为找不到UIBEzierPath类别。

结果如下所示:

所以这实际上会给出您想要的结果,但是您必须使用第三方库。