在 cgPath 上的两个坐标之间添加中点

Question

我们有一个函数基于 CLLocationCoordinate2D 数组创建路径，这个数组包含 4 个坐标，将创建一个正方形的路径：

func createPath(coordinates: [CLLocationCoordinate2D]) {
    for (index, coordinate) in coordinates.enumerated() {
        if index == 0 {
            path.move(to: CGPoint(x: coordinate.latitude, y:coordinate.longitude))
        } else {
            path.addLine(to: CGPoint(x: coordinate.latitude, y: coordinate.longitude))
        }
    }
}

我们还有一个函数可以计算两个 CGPoints 之间的中点：

   func getMiddlePoint(firstPoint: CGPoint, secondPoint: CGPoint) -> CGPoint {
        
        var middlePoint = CGPoint()
        
        middlePoint.x = (firstPoint.x + secondPoint.x)/2
        middlePoint.y = (firstPoint.y + secondPoint.y)/2
        return middlePoint
    }

我们想要的是每边得到四分，然后移动到下边。我尝试组合这样的函数，但它返回大约 90 分：

func createPath(coordinates: [CLLocationCoordinate2D]) {
    for (index, coordinate) in coordinates.enumerated() {
        if index == 0 {
            path.move(to: CGPoint(x: coordinate.latitude, y:coordinate.longitude))
        } else {
            path.addLine(to: CGPoint(x: coordinate.latitude, y: coordinate.longitude))//get the first point
            path.addLine(to:  getMiddlePoint(firstPoint: CGPoint(x: coordinate.latitude, y: coordinate.longitude), secondPoint: CGPoint(x: coordinate.latitude, y: coordinate.longitude))) // get the middle point
        }
    }
}

如果坐标是硬编码的，这就是它的样子，每边返回 2 个点：

func createPath(){
    path.move(to: CGPoint(x: 32.7915055, y: -96.8028408))//1
    path.addLine(to: CGPoint(x: 32.79174845, y: -96.80252195))//midpoint between 1 and 2
    path.addLine(to: CGPoint(x: 32.7919914, y: -96.8022031))//2
    path.addLine(to: CGPoint(x: 32.791501100000005, y: -96.80235195))////midpoint between 2 and 3
    path.addLine(to: CGPoint(x: 32.7910108, y: -96.8025008))//3
    path.addLine(to: CGPoint(x: 32.791301700000005, y: -96.8020985))//midpoint between 3 and 4
    path.addLine(to: CGPoint(x: 32.7915926, y: -96.8016962))//4
    path.addLine(to: CGPoint(x: 32.79154905, y: -96.8022685))//midpoint between 4 and 1
    
}

知道如何每边只得到 4 分吗？

Answer 1

您的path.addLine 语句被颠倒了。首先，您必须添加中点，然后添加下一个点。你的getMiddlePoint 也被调用了两次。

写法不同：

var prevPoint: CGPoint?

for coordinate in coordinates {
    let point = CGPoint(x: coordinate.latitude, y: coordinate.longitude)

    if let prevPoint = prevPoint {
       path.addLine(to: getMiddlePoint(firstPoint: prevPoint, secondPoint: point))
       path.addLine(to: point)
    } else {
       path.move(to: point)
    }

    prevPoint = point
}

另请注意，GPS 坐标是球面坐标，通常中点的计算方式不应与平面上的相同。