How to let gdi/gid+ object (pen\brush\rect\region etc.) semi-transparent?

I want draw multi layer in DC. each 开发者_Go百科layer have some gdi/gdi+ object and semi-transparent with the underlayer.

Using the function SetROP2 with the argument R2_MASKPEN is a very simple way to get a transparent pen effect.

you need to use the ARGB system for coloring. A represents transparency, it takes a value between 0 and 255. a value of 125 is semi transparant