procedure TForm1.FormCreate(Sender: TObject);
begin
  ImageEnView1.Proc.UndoLimit := 99;
  ImageEnView1.Proc.AutoUndo := True;
end;

procedure TForm1.UndoAll1Click(Sender: TObject);
var
  i: Integer;
begin
   if ImageEnView1.CurrentLayer is TIEImageLayer then
   begin
      for i := 0 to ImageEnView1.Proc.UndoCount - 1 do
        ImageEnView1.Proc.Undo(True);
    end;
end;

// Undo All
ImageEnView1.Proc.UndoAt( ImageEnView1.Proc.UndoCount, True );