Untitled

Prevent Click-thru on transparent form
Bitmap.Canvas.Brush.Color := clFuchsia;
   Bitmap.Canvas.FillRect (Rect (0, 0, Bitmap.Width, Bitmap.Height));

procedure TForm1.Button1Click(Sender: TObject);
var
  Color: DWORD;
  DC: HDC;
begin
  Color := $00FFFFFF;
  SetWindowLong(Handle, GWL_EXSTYLE,
      GetWindowLong(Handle, GWL_EXSTYLE) or WS_EX_LAYERED );
  SetLayeredWindowAttributes(Handle, Color, 255, LWA_COLORKEY);

  DC := GetWindowDC(Handle);
  SetDCBrushColor(DC, Color);
  FillRect(DC, Rect(10, 10, 100, 80), GetStockObject(DC_BRUSH));
  ReleaseDC(Handle, DC);
end;