本篇是D3D中的Alpha颜色混合（2）(https://www.oschina.net/action/GoToLink?urlhttp%3A%2F%2Fwww.cppblog.com%2Flovedday%2Farchive%2F2007%2F05%2F15%2F24121.html)的后续篇。另一种实现实现背景透明显示的简便方法是直接应