Private Sub PictureBox1_MouseUp(ByVal sender As Object, ByVal e As _
  System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseUp
        If rubbercancel Then Exit Sub
        ' Rechteck löschen
        RemoveRubberBox()
        ' als Ergebnis Rechteck zeichnen 
        Dim x0, y0, x1, y1, tmp As Integer
        Dim gr As Graphics = Graphics.FromHwnd(PictureBox1.Handle)
        Dim img As Bitmap 'für PictureBox1
        Dim buffer As Bitmap
        img = New Bitmap(PictureBox1.ClientSize.Width, _
          PictureBox1.ClientSize.Height)
        PictureBox1.Image = img
        'img = CType(PictureBox1.Image, Bitmap)
 
        ' Rechteck von (x0,y0) nach (x1,y1)
        x0 = rubberpos_orig.X
        x1 = x0 + rubbersize.Width
        If x0 > x1 Then tmp = x0 : x0 = x1 : x1 = tmp
        y0 = rubberpos_orig.Y
        y1 = y0 + rubbersize.Height
        If y0 > y1 Then tmp = y0 : y0 = y1 : y1 = tmp
        'buffer = img
        buffer = CropBitmap(CType(img, Bitmap), x0, y0, x1, y1)
        img = New Bitmap(rubbersize.Width, rubbersize.Height)
 
        'Kopiere den Inhalt der alten Bitmap
        gr = Graphics.FromImage(img)
        gr.DrawImageUnscaled(buffer, New Point(269, 14))
        PictureBox1.Image = img
 
        PictureBox1.Refresh()
        'PictureBox1.Invalidate()
        'PictureBox1.SizeMode = PictureBoxSizeMode.StretchImage
 
        buffer = Nothing 'verhindert OutOfMemory Exception aber nur 1x-mal
        'buffer.Dispose() 'Exception wird ausgelöst 
        gr.Dispose()
 
    End Sub

Private Function CropBitmap(ByRef bmp As Bitmap, ByVal cropX As Integer, ByVal _
  cropY As Integer, ByVal cropWidth As Integer, ByVal cropHeight As Integer) As _
  Bitmap
        Dim rect As New Rectangle(cropX, cropY, cropWidth, cropHeight)
        Dim cropped As Bitmap = bmp.Clone(rect, bmp.PixelFormat)
        Return cropped
    End Function