procedure TForm1.ButtonClick(Sender: TObject);
begin
  var SelRect := ImageEnView1.SelectedRect; // TIERectangle
  if (SelRect.height = ImageEnView1.IEBitmap_Height) and // if whole height of the image is selected
     (SelRect.width < ImageEnView1.IEBitmap_Width)       // if less than whole width of the image is selected
  then
  begin
    var modifiedBitmap := TIEBitmap.Create;
    var leftPart := ImageEnView1.IEBitmap.CreateROIBitmap(System.Classes.Rect(0, 0, SelRect.x - 1, SelRect.height - 1));
    var rightPart := ImageEnView1.IEBitmap.CreateROIBitmap(System.Classes.Rect(SelRect.x + SelRect.width, 0,
      ImageEnView1.IEBitmap_Width - 1, SelRect.height - 1));
    iexHelperFunctions.IEJoinBitmaps(modifiedBitmap, LeftPart, RightPart, False);
    ImageEnView1.Assign(modifiedBitmap);
    ImageEnView1.Update;
    FreeAndNil(RightPart);
    FreeAndNil(LeftPart);
    FreeAndNil(modifiedBitmap);
  end;
end;