// Zoom into the selected area of the image
procedure TMainForm.Button1Click(Sender: TObject);
var
  sel: TIERectangle;
begin
  if ImageEnView1.Selected then
  begin
    sel := ImageEnView1.SelectedRect;
    ImageEnView1.VisibleBitmapRect := Rect( sel.x, sel.y, sel.x + sel.width, sel.y + sel.height );
  end;
end;

procedure TMDIChild.ImageEnView1MouseDown(Sender: TObject; Button: TMouseButton;
                                          Shift: TShiftState; X, Y: Integer);
var
  sel: TIERectangle;
begin
  if ImageEnView1.Selected and
     ( ImageEnView1.XScr2Bmp( X ) > ImageEnView1.SelX1 ) and
     ( ImageEnView1.YScr2Bmp( Y ) > ImageEnView1.SelY1 ) and
     ( ImageEnView1.XScr2Bmp( X ) < ImageEnView1.SelX2 ) and
     ( ImageEnView1.YScr2Bmp( Y ) < ImageEnView1.SelY2 ) then
  begin
    sel := ImageEnView1.SelectedRect;
    ImageEnView1.VisibleBitmapRect := Rect( sel.x, sel.y, sel.x + sel.width, sel.y + sel.height );
  end;
end;