用vb写某一点到线段的最短距离

以下是使用 VB.NET 实现计算点 P 到线段 AB 的最短距离的代码：

Imports System.Math

Module Module1
    Structure Point
        Dim x As Double
        Dim y As Double
    End Structure

    ' 计算两点间距离
    Function CalcDistance(ByVal a As Point, ByVal b As Point) As Double
        Return Sqrt((a.x - b.x) ^ 2 + (a.y - b.y) ^ 2)
    End Function

    ' 计算点 P 到直线 AB 的垂足点 H
    Function CalcPerpendicular(ByVal p As Point, ByVal a As Point, ByVal b As Point) As Point
        Dim k As Double = ((p.x - a.x) * (b.x - a.x) + (p.y - a.y) * (b.y - a.y)) / (CalcDistance(a, b) ^ 2)
        Dim hx As Double = a.x + k * (b.x - a.x)
        Dim hy As Double = a.y + k * (b.y - a.y)
        Return New Point With {.x = hx, .y = hy}
    End Function

    ' 判断垂足点 H 是否在线段 AB 上
    Function IsOnSegment(ByVal h As Point, ByVal a As Point, ByVal b As Point) As Boolean
        Return Min(a.x, b.x) <= h.x AndAlso h.x <= Max(a.x, b.x) AndAlso Min(a.y, b.y) <= h.y AndAlso h.y <= Max(a.y, b.y)
    End Function

    ' 计算点 P 到线段 AB 的最短距离
    Function CalcShortestDistance(ByVal p As Point, ByVal a As Point, ByVal b As Point) As Double
        Dim h As Point = CalcPerpendicular(p, a, b)
        If IsOnSegment(h, a, b) Then
            Return CalcDistance(p, h)
        Else
            Return Min(CalcDistance(p, a), CalcDistance(p, b))
        End If
    End Function

    Sub Main()
        Dim p As New Point With {.x = 1, .y = 1}
        Dim a As New Point With {.x = 0, .y = 0}
        Dim b As New Point With {.x = 2, .y = 0}
        Console.WriteLine(CalcShortestDistance(p, a, b)) ' 输出 1
        Console.ReadKey()
    End Sub
End Module

以上代码中，假设点 P 为 (1,1)，线段的两端点分别为 A(0,0) 和 B(2,0)，输出结果为 1，表示点 P 到线段 AB 的最短距离为 1。