Private Ramp1(0 To 255, 0 To 2) As Integer
Private Ramp2(0 To 255, 0 To 2) As Integer
Private Declare Function GetDeviceGammaRamp Lib "gdi32" (ByVal hdc As Long, lpv _
  As Any) As Long
Private Declare Function SetDeviceGammaRamp Lib "gdi32" (ByVal hdc As Long, lpv _
As Any) As Long
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" ( _
Destination As Any, Source As Any, ByVal Length As Long)
 
Private Sub Form_Load()
Dim lVal As Long
Dim iCtr As Integer
 
GetDeviceGammaRamp Me.hdc, Ramp1(0, 0)
 
For iCtr = 0 To 255
lVal = Int2Lng(Ramp1(iCtr, 0))
Ramp2(iCtr, 0) = Lng2Int(Int2Lng(Ramp1(iCtr, 0)) / 2)
Ramp2(iCtr, 1) = Lng2Int(Int2Lng(Ramp1(iCtr, 1)) / 2)
Ramp2(iCtr, 2) = Lng2Int(Int2Lng(Ramp1(iCtr, 2)) / 2)
Next iCtr
Debug.Print SetDeviceGammaRamp(Me.hdc, Ramp2(0, 0))
 
End Sub
 
Private Sub Form_Unload(Cancel As Integer)
SetDeviceGammaRamp Me.hdc, Ramp1(0, 0)
End Sub
 
Public Function Int2Lng(IntVal As Integer) As Long
    CopyMemory Int2Lng, IntVal, 2
End Function
 
Public Function Lng2Int(Value As Long) As Integer
    CopyMemory Lng2Int, Value, 2
End Function

'wValue = Min&(nIndex * (wBrightness + 128), 65535)

Function SetBrightness(ByVal wBrightness As Long) As Long
' /*
' Changes the brightness of the entire screen.
' This function may not work properly in some video cards.
'
' The wBrightness value should be a number between 0 and 255.
' 128 = Regular brightness
' above 128 = brighter
' below 128 = darker
'
'    If hDC is NULL, SetBrightness automatically load and release
'    the display device context for you.
'
' */
    Dim bReturn As Long, nIndex As Long
    Dim wValue As Long
    bReturn = 0
 
'      //Generate the 256-colors array for the specified wBrightness value.
   Dim GammaArray(0 To 255, 0 To 2) As Integer
 
   For nIndex = 0 To 255
       wValue = Min(nIndex * (wBrightness + 128), 65535)
       GammaArray(nIndex, 0) = Lng2Int(wValue)
       GammaArray(nIndex, 1) = Lng2Int(wValue)
       GammaArray(nIndex, 2) = Lng2Int(wValue)
       List2.AddItem nIndex & ": " & wValue 'GammaArray(nIndex, 0)
   Next
 
'      //Set the GammaArray values into the display device context.
   bReturn = SetDeviceGammaRamp(Me.hDC, GammaArray(0, 0))
 
 
 
    SetBrightness = bReturn
End Function
 
Function Min(ByVal val1 As Long, ByVal val2 As Long) As Long
    If val1 > val2 Then
        Min = val2
    Else
        Min = val1
    End If
End Function