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const
  WM_CAP_DRIVER_CONNECT = WM_USER + 10;
  WM_CAP_EDIT_COPY = WM_USER + 30;
  WM_CAP_SET_PREVIEW = WM_USER + 50;
  WM_CAP_SET_OVERLAY = WM_USER + 51;
  WM_CAP_SET_PREVIEWRATE = WM_USER + 52;


  WM_CAP_DLG_VIDEOFORMAT          = WM_USER+41;
  WM_CAP_DLG_VIDEOSOURCE          = WM_USER+42;
  WM_CAP_DLG_VIDEOCOMPRESSION     = WM_USER+46;

function capCreateCaptureWindow(lpszWindowName: LPCSTR;
  dwStyle: DWORD;
  x, y,
  nWidth,
  nHeight: integer;
  hwndParent: HWND;
  nID: integer): HWND; stdcall;
  external 'AVICAP32.DLL' name 'capCreateCaptureWindowA';

procedure TForm1.Button1Click(Sender: TObject);
var handle:THandle;
begin
  handle := capCreateCaptureWindow('Video',ws_child+ws_visible, 0,
  0, 320, 240, Button1.Handle, 1);
  SendMessage(handle, WM_CAP_DRIVER_CONNECT, 0, 0);  
  SendMessage(handle, WM_CAP_SET_PREVIEWRATE, 30, 0);
  sendMessage(handle, WM_CAP_SET_OVERLAY, 1, 0);
  SendMessage(handle, wm_cap_set_preview, 1, 0);
  Application.ProcessMessages;
end;                    

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type
  TForm1 = class(TForm)
    SBarRed: TScrollBar;
    SBarGreen: TScrollBar;
    SBarBlue: TScrollBar;
    LblRed: TLabel;
    LblGreen: TLabel;
    LblBlue: TLabel;
    PnlRed: TPanel;
    PnlGreen: TPanel;
    PnlBlue: TPanel;
    PnlMix: TPanel;
    Lable1: TLabel;
    procedure SBarRedChange(Sender: TObject);

  procedure TForm1.SBarRedChange(Sender: TObject);
  begin
  PnlMix.Color := 65536*SBarBlue.Position + 256*SBarGreen.Position + SBarRed.Position;
  PnlRed.Color := SBarRed.Position;
  PnlGreen.Color := 256*SBarGreen.Position;
  PnlBlue.Color := 65536*SBarBlue.Position;
  end;                    

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  var c:TCanvas;

  c := TCanvas.create;
  c.handle := GetWindowDC(GetDesktopWindow);
  result := GetGValue(getpixel(c.handle,x,y));