Imports System.Drawing.Drawing2D
Public Class Form1
    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) _
      Handles MyBase.Load
        PictureBox1.Region = MakeTriangle(PictureBox1)
    End Sub
    Function MakeTriangle(c As Control) As Region
        Dim mp As New GraphicsPath
        Dim pts(2) As Point
        pts(0) = New Point(CInt(c.Left + c.Width / 2), c.Top)
        pts(1) = New Point(c.Left, c.Bottom)
        pts(2) = New Point(c.Right, c.Bottom)
        mp.AddPolygon(pts)
        Return New Region(mp)
        mp.Dispose()
    End Function
    Function MakeEllipse(c As Control) As Region
        Dim mp As New GraphicsPath
        mp.AddEllipse(c.DisplayRectangle)
        Return New Region(mp)
        mp.Dispose()
    End Function
    Private Sub PictureBox1_MouseHover(sender As Object, e As System.EventArgs) _
      Handles PictureBox1.MouseHover
        PictureBox1.Region = MakeEllipse(PictureBox1)
    End Sub
    Private Sub PictureBox1_MouseLeave(sender As Object, e As System.EventArgs) _
      Handles PictureBox1.MouseLeave
        PictureBox1.Region = MakeTriangle(PictureBox1)
    End Sub
End Class

Wenn alle Stricke rei?en, dann h?ng ich mich auf. ~ Karl Kraus