Get transparent form

you want to create form with transparent background, then you should override Create and Resize methods of your Form. CombineRgn function is basic function for realisation of this idea.

constructor TForm1.Create(AOwner: TComponent);
begin
  inherited;
  HorzScrollBar.Visible:=False;
  VertScrollBar.Visible:=False;
  NewWindowRgn;
end;

procedure TForm1.NewWindowRgn;
var
  i, CoordX, CoordY: Integer;
  FormRgn, NewRgn: THandle;
begin
  CoordX:=(Width-ClientWidth) div 2;
  CoordY:=Height-ClientHeight-4;

  FormRgn:=CreateRectRgn(0, 0, Width, Height);

  NewRgn:= CreateRectRgn(
    CoordX,
    CoordY,
    CoordX+ClientWidth,
    CoordY+ClientHeight);
  CombineRgn(FormRgn, FormRgn, NewRgn, RGN_DIFF);

  for i:= 0 to ControlCount -1 do
    with Controls[i] do
    begin
      NewRgn:= CreateRectRgn(
        CoordX + Left,
        CoordY + Top,
        CoordX + Left + Width,
        CoordY + Top + Height);
      CombineRgn(FormRgn, FormRgn, NewRgn, RGN_OR);
    end;

  SetWindowRgn(Handle, FormRgn, True);
end;

procedure TForm1.Resize;
begin
  inherited;
  NewWindowRgn;
end;