VB实现贝塞尔曲线绘制

Public Class frmBezier
    Private PtAry As New List(Of PointF)
    Private SelState As Boolean     '是否是选择控制多边形状态
    Private g As Graphics

    Private Sub CmdSelPoints_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CmdSelPoints.Click
        SelState = True
        PtAry.Clear()
        PictureBox1.Refresh()
        g = PictureBox1.CreateGraphics
    End Sub

    Private Sub PictureBox1_MouseDown(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseDown
        If SelState = True And e.Button = Windows.Forms.MouseButtons.Left Then PtAry.Add(New PointF(e.X, e.Y))
        If e.Button = Windows.Forms.MouseButtons.Right Then SelState = False
        If SelState = True And PtAry.Count >= 2 Then
            g.DrawLine(Pens.Brown, PtAry(PtAry.Count - 2), New PointF(e.X, e.Y))
        End If
    End Sub

    Private Sub CmdDrawBezier_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CmdDrawBezier.Click
        If (PtAry.Count - 4) Mod 3 <> 0 Then
            MsgBox("库函数只提供了4个控制点组成的贝塞尔曲线绘制方法,你选择的点数可为4，7，10，13，16,..." & vbCrLf & "其它数字不可以！", MsgBoxStyle.Critical, "提示")
            Exit Sub
        Else
            g.DrawBeziers(Pens.BlueViolet, PtAry.ToArray)        '只能绘制4个点的倍数组成的贝塞尔曲线
        End If

    End Sub