vb.net 最快速度批量获取坐标点在已知坐标链表里的垂足坐标

为了最快地批量获取坐标点在已知坐标链表里的垂足坐标，你可以使用以下优化：

1. 预先计算每条直线的斜率和截距，以避免在计算垂足坐标时重复计算。

2. 使用向量来计算垂足坐标，而不是使用公式，以避免浮点运算的开销。

3. 使用并行计算来利用多核处理器，加快计算速度。

以下是一种实现方式：

Public Function GetFootPoints(points As List(Of Point), lines As List(Of Line)) As List(Of Point)
    Dim footPoints As New List(Of Point)

    ' 预先计算每条直线的斜率和截距
    Dim slopes As New List(Of Double)
    Dim intercepts As New List(Of Double)
    For Each line In lines
        Dim slope As Double = (line.EndPoint.Y - line.StartPoint.Y) / (line.EndPoint.X - line.StartPoint.X)
        Dim intercept As Double = line.StartPoint.Y - slope * line.StartPoint.X
        slopes.Add(slope)
        intercepts.Add(intercept)
    Next

    ' 并行计算每个点的垂足坐标
    Parallel.ForEach(points, Sub(point)
                                 Dim minDistance As Double = Double.MaxValue
                                 Dim footPoint As Point

                                 For i = 0 To lines.Count - 1
                                     Dim slope As Double = slopes(i)
                                     Dim intercept As Double = intercepts(i)

                                     ' 计算垂足坐标
                                     Dim dx As Double = line.EndPoint.X - line.StartPoint.X
                                     Dim dy As Double = line.EndPoint.Y - line.StartPoint.Y
                                     Dim lengthSq As Double = dx * dx + dy * dy
                                     Dim dot As Double = (point.X - line.StartPoint.X) * dx + (point.Y - line.StartPoint.Y) * dy
                                     Dim t As Double = dot / lengthSq
                                     Dim foot_x As Double = line.StartPoint.X + t * dx
                                     Dim foot_y As Double = line.StartPoint.Y + t * dy

                                     ' 计算到该线段的垂足距离
                                     Dim distance As Double = Math.Sqrt((foot_x - point.X) ^ 2 + (foot_y - point.Y) ^ 2)

                                     If distance < minDistance Then
                                         minDistance = distance
                                         footPoint = New Point(foot_x, foot_y)
                                     End If
                                 Next

                                 footPoints.Add(footPoint)
                             End Sub)

    Return footPoints
End Function

注意，这种实现方式使用了并行计算，可能会对CPU和内存产生较大的负载，因此应根据实际情况进行测试和优化。