procedure TForm1.pitSet4CMClick(Sender: TObject);
const
  CM_COUNT = 4;  // How many CM does our selection represent?
var
  dotsperCmX, dotsperCmY: Double;
begin
  // Set Dots per CM
  dotsperCmX := ImageEnView1.SelectedRect.width  / CM_COUNT;
  dotsperCmY := ImageEnView1.SelectedRect.height / CM_COUNT;

  // Set Dots per Inch
  ImageEnView1.IO.Params.DpiX := Round( dotsperCmX * CM_per_Inch );
  ImageEnView1.IO.Params.DpiY := Round( dotsperCmY * CM_per_Inch );

  ImageEnView1.Update();
end;

procedure TForm1.pitSetOneInchClick(Sender: TObject);
const
  INCH_COUNT = 1;  // How many inches does our selection represent?
begin
  // Set Dots per Inch
  ImageEnView1.IO.Params.DpiX := ImageEnView1.SelectedRect.width  div INCH_COUNT;
  ImageEnView1.IO.Params.DpiY := ImageEnView1.SelectedRect.height div INCH_COUNT;
  ImageEnView1.Update();
end;