Public Class Form1
 
    Dim new_line As Boolean = True
    Dim current_line As Integer = 0
    Dim Lines As New List(Of LineClass.Line)
 
    Private Sub PictureBox1_MouseDown(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseDown
        If e.Button = Windows.Forms.MouseButtons.Left Then
            If new_line = True Then
                Lines(current_line).Basepoints = New LineClass.Basepoints(Lines( _
                  current_line))
                new_line = False
            End If
            Lines(current_line).Basepoints.Items.Add(New LineClass.Basepoint( _
              Lines(current_line).Basepoints, e.Location, _
              LineClass.Basepoint.PointType.corner, PictureBox1))
        ElseIf e.Button = Windows.Forms.MouseButtons.Right Then
            Lines.Add(New LineClass.Line)
            current_line += 1
        End If
        For i = 0 To Lines.Count - 1
            Lines(i).draw(PictureBox1)
        Next i
    End Sub
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        Lines.Add(New LineClass.Line)
    End Sub
End Class

Private _Items As New List(Of Basepoint)

    Private Sub Calculate_Spline(ByVal index As Integer)
        Dim i As Double
        Dim Temp As Point
        Dim Temp_inv As Point
        Dim P0 As Point = points(index).Loc
        Dim P1 As Point = points(index + 1).Loc
        Dim T0 As Point = points(index).Tangente_after
        Dim T1 As Point = points(index + 1).Tangente_before
        points(index).Line_Points.Clear()
        points(index).Line_Points_inv.Clear()
        If points(index).Line_Type = 2 Then                                 _
          'Hermite Spline                            'Beziere Spline
            For i = 0 To 1 Step STEPWIDTH
                Temp.X = B0(i) * P0.X + B1(i) * T0.X + B2(i) * P1.X + B3(i) * _
                  T1.X
                Temp.Y = B0(i) * P0.Y + B1(i) * T0.Y + B2(i) * P1.Y + B3(i) * _
                T1.Y
                Temp_inv.X = Temp.X
                Temp_inv.Y = PictureBox1.Height - Temp.Y
                points(index).Line_Points.Add(Temp)
                points(index).Line_Points_inv.Add(Temp_inv)
            Next i
        End If
    End Sub
 
    Private Function B0(ByVal u As Double)
        B0 = (1 - u) ^ 3
    End Function
 
    Private Function B1(ByVal u As Double)
        B1 = 3 * u * (1 - u) ^ 2
    End Function
 
    Private Function B2(ByVal u As Double)
        B2 = u ^ 3
    End Function
 
    Private Function B3(ByVal u As Double)
        B3 = 3 * u ^ 2 * (1 - u)
    End Function