MFC中创建透明窗口

//Set WS_EX_LAYERED on this window
::SetWindowLong(GetSafeHwnd(),
GWL_EXSTYLE,
::GetWindowLongPtr(GetSafeHwnd(),GWL_EXSTYLE)|WS_EX_LAYERED);

//Make this window 70% alpha transparent
this->SetLayeredWindowAttributes(0,(255*70)/100,LWA_ALPHA);

//Remove WS_EX_LAYERED from window style
::SetWindowLong(GetSafeHwnd(),
GWL_EXSTYLE,
::GetWindowLongPtr(GetSafeHwnd(),GWL_EXSTYLE)&~WS_EX_LAYERED);
//Repaint
this->RedrawWindow();

COLORREF maskColor = RGB(255,255,255);

SetWindowLong(this->GetSafeHwnd(),GWL_EXSTYLE,GetWindowLong(this->GetSafeHwnd(),GWL_EXSTYLE)^0x80000);
HINSTANCE hInst=LoadLibrary(_T("User32.DLL"));
if(hInst)
{
typedef BOOL (WINAPI * MYFUNC)(HWND , COLORREF,BYTE,DWORD);
MYFUNC fun=NULL;
fun=(MYFUNC)GetProcAddress(hInst,"SetLayeredWindowAttributes");
if(fun)fun(this->GetSafeHwnd(),maskColor,255,1);
FreeLibrary(hInst);
}

else
{
CRect rect;
CPaintDC dc(this);
GetClientRect(rect);
dc.FillSolidRect(rect,RGB(255,255,255));
//dc.FillSolidRect(rect,RGB(108,108,108));

CBitmap bmp1,bmp2;
//bmp1.LoadBitmap(IDB_B_1);
bmp1.LoadBitmap(IDB_BITMAP6);
bmp2.LoadBitmap(IDB_BITMAP7);

//bmp2.LoadBitmap(IDB_B_2);
//CPaintDC dc(this); // device context for painting
CDC memDC;
memDC.CreateCompatibleDC(&dc);
CBitmap* pbmpOld;

pbmpOld = memDC.SelectObject(&bmp1);
dc.BitBlt(0, 0, 2000, 1500, &memDC, 0, 0, SRCPAINT);  // 注意最后一个参数

memDC.SelectObject(&bmp2);
dc.BitBlt(0, 0, 2000, 1500, &memDC, 0, 0, SRCAND);  // 注意最后一个参数

memDC.SelectObject(pbmpOld);
memDC.DeleteDC();

CDialog::OnPaint();
}