Dim p1 As System.Drawing.Image = System.Drawing.Image.FromFile( _
          "C:\temp\test.jpg")
        Dim p2 As System.Drawing.Image = PictureBox1.Image
        Dim b1 As New System.Drawing.Bitmap(p1, p1.Size)
        Dim b2 As New System.Drawing.Bitmap(p2, p2.Size)
        Dim h, w, c As Integer
        For h = 1 To b1.Height - 1
            For w = 1 To b1.Width - 1
                If b1.GetPixel(w, h) <> b2.GetPixel(w, h) Then
                    c += 1
                End If
            Next
        Next
        MsgBox(c & " Pixel sind unterschiedlich")