请教一个分层窗口的截不出来的问题

[tghgffdgd]

之前一直是少了个参数然后不行，可是后来参数加了也不行，后面误打误撞换了写法发现可以。 不知道是哪里出了问题，代码差别在哪里。

void CPrintScr::Print()
{
	HDC hScrDC = CreateDCW(L"DISPLAY", NULL, NULL, NULL);
	const int nWidth = GetDeviceCaps(hScrDC, HORZRES);
	const int nHeight = GetDeviceCaps(hScrDC, VERTRES);
	m_hMemDC = CreateCompatibleDC(hScrDC);
	HBITMAP hBitmap = CreateCompatibleBitmap(hScrDC, nWidth, nHeight);
	HBITMAP hBmpOld = (HBITMAP)SelectObject(m_hMemDC, hBitmap);
	BitBlt(m_hMemDC, 0, 0, nWidth, nHeight, hScrDC, 0, 0, SRCCOPY | CAPTUREBLT);
	SelectObject(m_hMemDC, hBmpOld);
	DeleteDC(m_hMemDC);
	DeleteDC(hScrDC);
	SetSavePath(L"c:\\tt.jpg");
	SaveBitmapToFile(hBitmap, JPG);//获取分层窗口失败，分层窗口都是透明
...
}

HBITMAP CaptureScreen()
{
	HDC hScrDC = CreateDCW(L"DISPLAY", NULL, NULL, NULL);
	const int nWidth = GetDeviceCaps(hScrDC, HORZRES);
	const int nHeight = GetDeviceCaps(hScrDC, VERTRES);
	HDC m_hMemDC = CreateCompatibleDC(hScrDC);
	HBITMAP hBitmap = CreateCompatibleBitmap(hScrDC, nWidth, nHeight);
	HBITMAP hBmpOld = (HBITMAP)SelectObject(m_hMemDC, hBitmap);
	BitBlt(m_hMemDC, 0, 0, nWidth, nHeight, hScrDC, 0, 0, SRCCOPY | CAPTUREBLT);
	SelectObject(m_hMemDC, hBmpOld);
	DeleteDC(m_hMemDC);
	DeleteDC(hScrDC);
	return hBitmap;
}
{
...
	g_PrintScr.SetSavePath(L"c:\\tt2.jpg");
	g_PrintScr.SaveBitmapToFile(CaptureScreen(), JPG);//获取分层窗口成功
...
}