procedure TForm2.Button3Click(Sender: TObject);
var
  ThisBitmap: TBitmap;
  ThisIEBitmap: TIEBitmap;
  OldHeight: Integer;
begin
  ThisBitmap := TBitmap.Create;
  ThisIEBitmap := TIEBitmap.Create;
  try
    OldHeight := ImageEnView1.IEBitmap.Height;
    ThisBitmap := GetMyBitmap;
    ThisBitmap.PixelFormat := pf24bit; // important!
    ThisIEBitmap.CopyFromTBitmap(ThisBitmap);
    ImageEnView1.IEBitmap.Resize(0, 0, 0, ThisBitmap.Height, clWhite);
    ThisIEBitmap.DrawToTIEBitmap(ImageEnView1.IEBitmap, 0, OldHeight);
    ImageEnView1.Height := ImageEnView1.IEBitmap.Height;
    ImageEnView1.Repaint;
    ImageEnView1.IO.SaveToFile('R:\Image.png');
  finally
    ThisIEBitmap.Free;
    ThisBitmap.Free;
  end;
end;