Swift 3.x和Swift 4.1（下面看Swift 4.2或主要..）

Question

如何获得包含给定CGPoint（CGPath）中包含的所有CGMutablePathRef的数组？

Answer 1

使用 Swift 2.x （对于 Swift 3.x ， Swift 4.x 和 Swift 5.x 在下面阅读..），我发现这篇关于C Callbacks in Swift的精彩文章。

如Kevin Ballard所述，试图获得所有CGPoint（s）＆＃34;，正如他所说的那样，这可能是一个坏主意。

所以，我认为最好的方法是获取用于创建特定CGPath的路径元素点：

//MARK: - CGPath extensions
extension CGPath {
    func forEach(@noescape body: @convention(block) (CGPathElement) -> Void) {
        typealias Body = @convention(block) (CGPathElement) -> Void
        func callback(info: UnsafeMutablePointer<Void>, element: UnsafePointer<CGPathElement>) {
            let body = unsafeBitCast(info, Body.self)
            body(element.memory)
        }
        print(sizeofValue(body))
        let unsafeBody = unsafeBitCast(body, UnsafeMutablePointer<Void>.self)
        CGPathApply(self, unsafeBody, callback)
    }

    func getPathElementsPoints() -> [CGPoint] {
        var arrayPoints : [CGPoint]! = [CGPoint]()
        self.forEach { element in
            switch (element.type) {
            case CGPathElementType.MoveToPoint:
                arrayPoints.append(element.points[0])
            case .AddLineToPoint:
                arrayPoints.append(element.points[0])
            case .AddQuadCurveToPoint:
                arrayPoints.append(element.points[0])
                arrayPoints.append(element.points[1])
            case .AddCurveToPoint:
                arrayPoints.append(element.points[0])
                arrayPoints.append(element.points[1])
                arrayPoints.append(element.points[2])
            default: break
            }
        }
        return arrayPoints
    }
}

使用此扩展程序，您可以执行以下操作：

var bezier = UIBezierPath(ovalInRect: CGRectMake(0, 0, 400, 300))
let myOval = bezier.CGPath
let junctionPoints = myOval.getPathElementsPoints()
print("junction points are: \(junctionPoints)")

Swift 3.x和Swift 4.1（下面看Swift 4.2或主要..）

（由于语法重新引入@convention(c)而有一些更正）：

extension CGPath {

    func forEach( body: @convention(block) (CGPathElement) -> Void) {
        typealias Body = @convention(block) (CGPathElement) -> Void
        let callback: @convention(c) (UnsafeMutableRawPointer, UnsafePointer<CGPathElement>) -> Void = { (info, element) in
            let body = unsafeBitCast(info, to: Body.self)
            body(element.pointee)
        }
        print(MemoryLayout.size(ofValue: body))
        let unsafeBody = unsafeBitCast(body, to: UnsafeMutableRawPointer.self)
        self.apply(info: unsafeBody, function: unsafeBitCast(callback, to: CGPathApplierFunction.self))
    }


    func getPathElementsPoints() -> [CGPoint] {
        var arrayPoints : [CGPoint]! = [CGPoint]()
        self.forEach { element in
            switch (element.type) {
            case CGPathElementType.moveToPoint:
                arrayPoints.append(element.points[0])
            case .addLineToPoint:
                arrayPoints.append(element.points[0])
            case .addQuadCurveToPoint:
                arrayPoints.append(element.points[0])
                arrayPoints.append(element.points[1])
            case .addCurveToPoint:
                arrayPoints.append(element.points[0])
                arrayPoints.append(element.points[1])
                arrayPoints.append(element.points[2])
            default: break
            }
        }
        return arrayPoints
    }

    func getPathElementsPointsAndTypes() -> ([CGPoint],[CGPathElementType]) {
        var arrayPoints : [CGPoint]! = [CGPoint]()
        var arrayTypes : [CGPathElementType]! = [CGPathElementType]()
        self.forEach { element in
            switch (element.type) {
            case CGPathElementType.moveToPoint:
                arrayPoints.append(element.points[0])
                arrayTypes.append(element.type)
            case .addLineToPoint:
                arrayPoints.append(element.points[0])
                arrayTypes.append(element.type)
            case .addQuadCurveToPoint:
                arrayPoints.append(element.points[0])
                arrayPoints.append(element.points[1])
                arrayTypes.append(element.type)
                arrayTypes.append(element.type)
            case .addCurveToPoint:
                arrayPoints.append(element.points[0])
                arrayPoints.append(element.points[1])
                arrayPoints.append(element.points[2])
                arrayTypes.append(element.type)
                arrayTypes.append(element.type)
                arrayTypes.append(element.type)
            default: break
            }
        }
        return (arrayPoints,arrayTypes)
    }
}

Swift＆gt; 4.1（也是Swift 5.x）

extension CGPath {
    func forEach( body: @escaping @convention(block) (CGPathElement) -> Void) {
        typealias Body = @convention(block) (CGPathElement) -> Void
        let callback: @convention(c) (UnsafeMutableRawPointer, UnsafePointer<CGPathElement>) -> Void = { (info, element) in
            let body = unsafeBitCast(info, to: Body.self)
            body(element.pointee)
        }
        //print(MemoryLayout.size(ofValue: body))
        let unsafeBody = unsafeBitCast(body, to: UnsafeMutableRawPointer.self)
        self.apply(info: unsafeBody, function: unsafeBitCast(callback, to: CGPathApplierFunction.self))
    }
    func getPathElementsPoints() -> [CGPoint] {
        var arrayPoints : [CGPoint]! = [CGPoint]()
        self.forEach { element in
            switch (element.type) {
            case CGPathElementType.moveToPoint:
                arrayPoints.append(element.points[0])
            case .addLineToPoint:
                arrayPoints.append(element.points[0])
            case .addQuadCurveToPoint:
                arrayPoints.append(element.points[0])
                arrayPoints.append(element.points[1])
            case .addCurveToPoint:
                arrayPoints.append(element.points[0])
                arrayPoints.append(element.points[1])
                arrayPoints.append(element.points[2])
            default: break
            }
        }
        return arrayPoints
    }
    func getPathElementsPointsAndTypes() -> ([CGPoint],[CGPathElementType]) {
        var arrayPoints : [CGPoint]! = [CGPoint]()
        var arrayTypes : [CGPathElementType]! = [CGPathElementType]()
        self.forEach { element in
            switch (element.type) {
            case CGPathElementType.moveToPoint:
                arrayPoints.append(element.points[0])
                arrayTypes.append(element.type)
            case .addLineToPoint:
                arrayPoints.append(element.points[0])
                arrayTypes.append(element.type)
            case .addQuadCurveToPoint:
                arrayPoints.append(element.points[0])
                arrayPoints.append(element.points[1])
                arrayTypes.append(element.type)
                arrayTypes.append(element.type)
            case .addCurveToPoint:
                arrayPoints.append(element.points[0])
                arrayPoints.append(element.points[1])
                arrayPoints.append(element.points[2])
                arrayTypes.append(element.type)
                arrayTypes.append(element.type)
                arrayTypes.append(element.type)
            default: break
            }
        }
        return (arrayPoints,arrayTypes)
    }
}

Answer 2

您可以使用CGPathApply()迭代路径中的每个段，并使用该段运行自定义函数。这将为您提供该路径的所有信息。

然而，如果通过“所有CGPoint（s）”，你意味着每个点都有一个像素渲染它，这是一个无限大小的集合。虽然您当然可以使用apply函数来获取每个段，然后对于每个非移动段，使用段的控制点评估您自己的数学运算，以获得您想要的任何密度的点列表。

Answer 3

Apple添加了 instance方法 CGPath.applyWithBlock，可用于 iOS11.0 +和macOS10.13 +

您仍然可以使用CGPath.apply检查路径的每个元素，如先前答案中所述。 但是，如果要避免使用C风格的指针和unsafeBitCast ，则您应该使用更加方便的实例方法 applyWithBlock。例如，如果要获取CGPath的CGPoints数组，则可以向CGPath添加扩展名 ，在本示例中为 compute属性 （点）收集CGPath的CGPoint ：

extension CGPath {

  ///< this is a computed property
  var points: [CGPoint] {

     ///< this is a local container where we will store our CGPoints
     var arrPoints: [CGPoint] = []

     ///< applyWithBlock lets us examine each element of the CGPath, and decide what to do
     self.applyWithBlock { element in

        switch element.pointee.type
        {
        case .moveToPoint, .addLineToPoint:
          arrPoints.append(element.pointee.points.pointee)

        case .addQuadCurveToPoint:
          arrPoints.append(element.pointee.points.pointee)
          arrPoints.append(element.pointee.points.advance(by: 1).pointee))

        case .addCurveToPoint:
          arrPoints.append(element.pointee.points.pointee)
          arrPoints.append(element.pointee.points.advance(by: 1).pointee))
          arrPoints.append(element.pointee.points.advance(by: 2).pointee))

        default:
          break
        }
     }

    ///< We are now done collecting our CGPoints and so we can return the result
    return arrPoints

  }
}

Answer 4

CGPath是一种不透明的数据类型，并不一定存储所有使用的点。除此之外，路径实际上可能不会绘制用作输入的所有点（例如，考虑Bézier控制点）。

从路径中获取信息的唯一两个documented ways是使用CGPathGetBoundingBox来获取边界框，或使用CGPathApply来调用回调函数的更复杂的方法如果CGPathElement类型，将为您提供序列。

如何获得CGPath的CGPoint

4 个答案:

Swift 3.x和Swift 4.1（下面看Swift 4.2或主要..）

Swift＆gt; 4.1（也是Swift 5.x）