MFC background transparent

one:

typedef BOOL (WINAPI *lpfnSetLayeredWindowAttributes)(HWND hWnd, COLORREF crKey, BYTE bAlpha, DWORD dwFlags);
lpfnSetLayeredWindowAttributes SetLayeredWindowAttributes;   //设置成边缘透明
COLORREF maskColor = RGB(240, 240, 240);
HMODULE hUser32 = GetModuleHandle(_T("user32.dll")); //加载动态链接库
SetLayeredWindowAttributes = (lpfnSetLayeredWindowAttributes)GetProcAddress(hUser32, "SetLayeredWindowAttributes");            //取得SetLayeredWindowAttributes函数指针            //为窗口加入WS_EX_LAYERED扩展属性
SetWindowLong(this->GetSafeHwnd(), GWL_EXSTYLE, GetWindowLong(GetSafeHwnd(), GWL_EXSTYLE)^WS_EX_LAYERED);             //调用SetLayeredWinowAttributes函数
/*SetLayeredWindowAttributes(this->GetSafeHwnd(), maskColor, 192, LWA_COLORKEY);  */
SetLayeredWindowAttributes(this->GetSafeHwnd(), maskColor, 255, LWA_ALPHA | LWA_COLORKEY);
FreeLibrary(hUser32);   //释放动态链
//LWA_ALPHA时：crKey参数无效，bAlpha参数有效；
//LWA_COLORKEY：窗体中的所有颜色为crKey的地方将变为透明，bAlpha参数无效。
//LWA_ALPHA | LWA_COLORKEY：crKey的地方将变为全透明，而其它地方根据bAlpha参数确定透明度。

two:

COLORREF m_bgcolor = RGB(0, 0, 0);
BOOL m_bTransparent = ToggleTransparent(m_bgcolor, 100, LWA_ALPHA);
BOOL ToggleTransparent(COLORREF crKey, BYTE bAlpha, DWORD dwFlags)
{
    BOOL bResult;
    LONG dwExStyle;
    dwExStyle = GetWindowLong(this->GetSafeHwnd(), GWL_EXSTYLE);
    if (dwExStyle & WS_EX_LAYERED)
    {
        dwExStyle &= ~(WS_EX_LAYERED);
        bResult = FALSE;
    }
    else
    {
        dwExStyle |= (WS_EX_LAYERED);
        bResult = TRUE;
    }
    SetWindowLong(this->GetSafeHwnd(), GWL_EXSTYLE, dwExStyle);
    SetLayeredWindowAttributes( crKey, bAlpha, dwFlags);
    return bResult;
}