Set the transparency for the background colour or graphic of a frame, where 100% is completely transparent and 0% is opaque. When you increase the transparency of the background, the underlying text or objects become visible through the background of the frame.
设置背景颜色或框图形的透明度：100% 表示完全透明，0% 表示不透明。随着背景透明度的增加，被覆盖的文字或对象会透过框背景逐渐显现出来。