ios - 我如何获得 uibezierPath 的面积和周长，因为 fill() 方法使用了封闭区域

Question

因为 UIBeizerPath 支持 fill() 来填充封闭区域。 我的要求是如何从 UIBeizerPath() 获取封闭区域，与 fill() 方法使用的相同。 如果我能在求 beizerpath 的面积和周长方面得到帮助，我将不胜感激。

假设我想获取字母“A”中的封闭区域，我可以获得所有 beizerPath CGPoints 但无法定义子路径，因为 evenOdd 规则用于获取所需的字段属性，最后得到面积。我很好奇fill()是如何得到封闭区域的。

我得到了字体的beizerPath solution并希望获得由此绘制的任何字体的区域。

我怎样才能做到这一点。

Answer 1

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))
    }
}


extension UIBezierPath{
    var length: CGFloat{
        var pathLength:CGFloat = 0.0
        var current =  CGPoint.zero
        var first   =   CGPoint.zero

        self.cgPath.forEach{ element in
            pathLength += element.distance(to: current, startPoint: first)

            if element.type == .moveToPoint{
                first = element.point
            }
            if element.type != .closeSubpath{
                current = element.point
            }
        }
        return pathLength
    }
}


extension CGPathElement{

    var point: CGPoint{
        switch type {
        case .moveToPoint, .addLineToPoint:
            return self.points[0]
        case .addQuadCurveToPoint:
            return self.points[1]
        case .addCurveToPoint:
            return self.points[2]
        case .closeSubpath:
            return CGRect.null.origin
        }
    }

    func distance(to point: CGPoint, startPoint: CGPoint ) -> CGFloat{
        switch type {
        case .moveToPoint:
            return 0.0
        case .closeSubpath:
            return point.distance(to:startPoint)
        case .addLineToPoint:
            return point.distance(to:self.points[0])
        case .addCurveToPoint:
            return BezierCurveLength(p0: point, c1: self.points[0], c2: self.points[1], p1: self.points[2])
        case .addQuadCurveToPoint:
            return BezierCurveLength(p0: point, c1: self.points[0], p1: self.points[1])
        }
    }
}

extension CGPoint{
    func distance(to:CGPoint) -> CGFloat{
        let dx = pow(to.x - self.x,2)
        let dy = pow(to.y - self.y,2)
        return sqrt(dx+dy)
    }
}



// Helper Functions

func CubicBezierCurveFactors(t:CGFloat) -> (CGFloat,CGFloat,CGFloat,CGFloat){
    let t1 = pow(1.0-t, 3.0)
    let t2 = 3.0*pow(1.0-t,2.0)*t
    let t3 = 3.0*(1.0-t)*pow(t,2.0)
    let t4 = pow(t, 3.0)

    return  (t1,t2,t3,t4)
}


func QuadBezierCurveFactors(t:CGFloat) -> (CGFloat,CGFloat,CGFloat){
    let t1 = pow(1.0-t,2.0)
    let t2 = 2.0*(1-t)*t
    let t3 = pow(t, 2.0)

    return (t1,t2,t3)
}

// Quadratic Bezier Curve

func BezierCurve(t:CGFloat,p0:CGFloat,c1:CGFloat,p1:CGFloat) -> CGFloat{
    let factors = QuadBezierCurveFactors(t: t)
    return (factors.0*p0) + (factors.1*c1) + (factors.2*p1)
}


// Quadratic Bezier Curve

func BezierCurve(t:CGFloat,p0:CGPoint,c1:CGPoint,p1:CGPoint) -> CGPoint{
    let x = BezierCurve(t: t, p0: p0.x, c1: c1.x, p1: p1.x)
    let y = BezierCurve(t: t, p0: p0.y, c1: c1.y, p1: p1.y)
    return CGPoint(x: x, y: y)
}



// Cubic Bezier Curve

func BezierCurve(t:CGFloat,p0:CGFloat, c1:CGFloat, c2:CGFloat, p1:CGFloat) -> CGFloat{
    let factors = CubicBezierCurveFactors(t: t)
    return (factors.0*p0) + (factors.1*c1) + (factors.2*c2) + (factors.3*p1)
}


// Cubic Bezier Curve

func BezierCurve(t: CGFloat, p0:CGPoint, c1:CGPoint, c2: CGPoint, p1: CGPoint) -> CGPoint{
    let x = BezierCurve(t: t, p0: p0.x, c1: c1.x, c2: c2.x, p1: p1.x)
    let y = BezierCurve(t: t, p0: p0.y, c1: c1.y, c2: c2.y, p1: p1.y)
    return CGPoint(x: x, y: y)
}


// Cubic Bezier Curve Length

func BezierCurveLength(p0:CGPoint,c1:CGPoint, c2:CGPoint, p1:CGPoint) -> CGFloat{
    let steps = 12
    var current  = p0
    var previous = p0
    var length:CGFloat = 0.0

    for i in 1...steps{
        let t = CGFloat(i) / CGFloat(steps)
        current = BezierCurve(t: t, p0: p0, c1: c1, c2: c2, p1: p1)
        length += previous.distance(to: current)
        previous = current
    }

    return length
}


// Quadratic Bezier Curve Length

func BezierCurveLength(p0:CGPoint,c1:CGPoint, p1:CGPoint) -> CGFloat{
    let steps = 12

    var current  = p0
    var previous = p0
    var length:CGFloat = 0.0

    for i in 1...steps{
        let t = CGFloat(i) / CGFloat(steps)
        current = BezierCurve(t: t, p0: p0, c1: c1, p1: p1)
        length += previous.distance(to: current)
        previous = current
    }
    return length
}

• 创建贝塞尔曲线路径
• 使用 bezierPath.length 获取封闭贝塞尔路径的周长 (对于 swift 3)
  • https://gist.github.com/xhamr/4e8702d4ba9e88153f39be6b50710d65 ( swift 2)