From: "Philipp Pammler" <tschaosu@exhausts.de>
Newsgroups: borland.public.delphi.graphics
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Subject: Re: Gamma
Date: Sat, 14 Sep 2002 17:58:46 +0200
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hi kim

this should help u a bit

type
  TGammaRamp = packed record
    R : array[0..255] of word;
    G : array[0..255] of word;
    B : array[0..255] of word;
  end;

var
  SYS_OldGamma : TGammaRamp;

// storeoldgamma
//
procedure StoreOldGamma;
var
  DC : HDC;

begin
  DC := GetDC(0);
  GetDeviceGammaRamp(DC, SYS_OldGamma);
  ReleaseDC(0, DC);
end;

// restoreoldgamma
//
procedure RestoreOldGamma;
var
  DC : HDC;

begin
  DC := GetDC(0);
  SetDeviceGammaRamp(DC, SYS_OldGamma);
  ReleaseDC(0, DC);
end;

// setgamma
// to 0 = brighter, to 255 = more normal gamma
function SetGamma(Value : byte) : TGammaRamp;
var
  I  : integer;
  DC : HDC;
  V  : integer;

begin
  for I := 0 to 255 do begin
    V := Round(255 * Power(I / 255, Abs(Value) / 255));
    if V > 255 then
      V := 255;
      Result.R[I] := V shl 8;
      Result.G[I] := V shl 8;
      Result.B[I] := V shl 8;
  end;
  DC := GetDC(0);
  SetDeviceGammaRamp(DC, Result);
  ReleaseDC(0, DC);
end;


- first backup the original gammaramp via "StoreOldGamma"
- modify the ramp e.g.
  var
    MyGamma : TGammaRamp;
  begin
    MyGamma := SetGamma(ScrollBar1.Position);
  end;
- when finishing u should restore the original gammaramp via
"RestoreOldGamma"

HTH, philipp.