Transparent Button with an Icon

To create a button that is wide enough to press, but transparent, with the icon inside:     

 <ImageButton

                android:id="@+id/save"

                android:layout_width="100dip"

                android:layout_height="wrap_content"

                android:background="@null"

                android:contentDescription="@string/save_text"

                android:src="@drawable/save" />