Private Enum MausButtonStatus
        NichBetätigt
        Gedrückt
        Losgelassen
    End Enum
 
    Dim PIC As Bitmap
    Dim Maus As MausButtonStatus
    Dim POS As Rectangle
 
    Private Sub PictureBox1_ContextMenuChanged(ByVal sender As Object, ByVal e _
      As System.EventArgs) Handles PictureBox1.ContextMenuChanged
 
    End Sub
 
    Private Sub PictureBox1_MouseDown(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseDown
        Maus = MausButtonStatus.Gedrückt
        With POS
            .X = e.X
            .Y = e.Y
        End With
    End Sub
    Private Sub PictureBox1_MouseMove(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseMove
        If Maus = MausButtonStatus.Gedrückt Then
            With POS
                .Width = e.X - .X
                .Height = e.Y - .Y
            End With
        End If
        PictureBox1.Refresh()
    End Sub
    Private Sub PictureBox1_MouseUp(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.MouseEventArgs) Handles PictureBox1.MouseUp
        Maus = MausButtonStatus.Losgelassen
    End Sub
 
    Private Sub PictureBox1_Paint(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.PaintEventArgs) Handles PictureBox1.Paint
        Dim pe As New Pen(Color.Black, 1)
        pe.DashStyle = Drawing2D.DashStyle.Dot
        e.Graphics.DrawImage(PIC, 0, 0)
 
        If Maus = MausButtonStatus.Gedrückt Then
            e.Graphics.DrawRectangle(pe, POS)
        End If
        If Maus = MausButtonStatus.Losgelassen Then
            PIC = New Bitmap(PIC.Clone(POS, Imaging.PixelFormat.Undefined), _
              PictureBox1.Width, PictureBox1.Height)
            e.Graphics.DrawImage(PIC, 0, 0)
            Maus = MausButtonStatus.NichBetätigt
        End If
    End Sub
 
    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) _
      Handles Me.Load
        PIC = New Bitmap(Bitmap.FromFile("c:\Testpic.jpg"), PictureBox1.Width, _
        PictureBox1.Height)
    End Sub