procedure TForm1.ImageEnView1MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Integer);
{ ImageEnView Mouse Down. }
var
  iZoom: double;
begin
  if Button = mbLeft then
  begin
    iZoom := ImageEnView1.Zoom + 25;
    ImageEnView1.ZoomAt(x, y, iZoom, False);
  end
  else
  begin
    iZoom := ImageEnView1.Zoom - 25;
    ImageEnView1.ZoomAt(x, y, iZoom, False);
  end;
end;