How to use the SetLayeredWindowAttributes function, dialog transparent method __ function

This article introduces a way to make the dialog transparent use the following API functions, of course, MFC in the CWnd class also has the function (note: I use the environment for VS2008, you can directly use the function, VC6.0 different use of different methods, the introduction on the Web): The prototype of the function is BOOL SetLayeredWindowAttributes (HWND hwnd,//Handle to the layered window colorref Crkey,//Specifies the color key BYTE bAl PHA,//value for the blend function DWORD dwflags/action);
Where the HWND is the handle of the transparent form,//MFC CWnd class has not changed the Crkey to mask color, you can use RGB (R,G,B) to specify. ColorKey Balpha is transparency, with a value range of (0,255), where 0 represents full transparency and 255 is opaque. dwflags is transparent and can take two values: When the value is Lwa_alpha, the Crkey parameter is invalid, the Balpha parameter is valid, and when the value is Lwa_colorkey, all the colors in the form are Crkey and the Balpha parameter is invalid. Lwa_alpha = 0x2 lwa_colorkey=0x1 can also take a combination of two values: Lwa_alpha or Lwa_colorkey. Such crkey will become fully transparent, while other places are based on the Balpha parameters to determine transparency. SetLayeredWindowAttributes (0, Lwa_alpha);
Note: To make a form transparent, first make the window have ws_ex_layered extended properties by:
Add the following code to the function OnInitDialog ()
SetWindowLong (M_hwnd,gwl_exstyle,getwindowlong (This->getsafehwnd (), Gwl_exstyle) ^WS_EX_LAYERED);