Private Declare Function GetDeviceGammaRamp Lib "gdi32" (ByVal hdc As _
      IntPtr, ByRef lpv As String) As Boolean
    Private Declare Function SetDeviceGammaRamp Lib "gdi32" (ByVal hdc As _
    IntPtr, ByRef lpv As String) As Boolean
    Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (ByRef _
    Destination As Integer, ByRef Source As Integer, ByVal Length As Integer)

    Private Sub formMain_Paint(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.PaintEventArgs) Handles Me.Paint
        Try
            formHdc = e
 
            GetDeviceGammaRamp(formHdc.Graphics.GetHdc, Ramp1(0, 0))
            a = 2
            b = 2
 
        Catch es As SystemException
            MsgBox("formMain_Paint [gesammt]" & es.ToString)
        End Try
    End Sub

        Dim abdunkeln As Boolean = SetDeviceGammaRamp(formHdc.Graphics.GetHdc, _
          Ramp1(0, 0))
        ListBox1.Items.Add("Abdunkeln: " & abdunkeln)

        Dim iCtr As Short
        Dim lVal As Integer
        For iCtr = 0 To 255
            lVal = Int2Lng(Ramp1(iCtr, 0))
            Ramp2(iCtr, 0) = Lng2Int(Int2Lng(Ramp1(iCtr, 0)) / b)
            Ramp2(iCtr, 1) = Lng2Int(Int2Lng(Ramp1(iCtr, 1)) / b)
            Ramp2(iCtr, 2) = Lng2Int(Int2Lng(Ramp1(iCtr, 2)) / b)
        Next iCtr
        a = a - 2
 
        Dim aufhellen As Boolean = SetDeviceGammaRamp(formHdc.Graphics.GetHdc, _
          Ramp2(0, 0))
        ListBox1.Items.Add("Aufhellen: " & aufhellen)