procedure TForm1.Button1Click(Sender: TObject);
begin
 { Layer 0 is the background and is always present 
   so if LayersCount = 2 then there is a background
   layer (0) and a "true" layer (1) }
 if ImageEnView1.LayersCount = 2 then
   ImageEnView1.LayersRemove(1)
 else
   Close;
end;