ImageEnVect1.RotateObject(hobj, 90, ierImage);

procedure TMainForm.Flip1Click(Sender: TObject);
var
  i: Integer;
  iIEBitmap: TIEBitmap;
begin
  // flip the base IEBitmap in the selected layer
  ImageEnVect1.IEBitmap.Flip(fdVertical);
  // find and flip all iekBITMAP objects in the selected layer
  for i := 0 to ImageEnVect1.SelObjectsCount - 1 do
    if ImageEnVect1.ObjKind[ImageEnVect1.SelObjects[i]] = iekBITMAP then
    begin
      iIEBitmap := ImageEnVect1.ObjBitmap[i];
      iIEBitmap.Flip(fdVertical);
    end;
  ImageEnVect1.Update;
end;