Bitmap Save

void CCatchScreenDlg::SaveScreenToFile(LPCTSTR szFileName)
{
	HDC hScrDC = ::GetDC(NULL);
	HDC hMemDC = NULL;

	BYTE *lpBitmapBits = NULL; 

	int nWidth = GetSystemMetrics(SM_CXSCREEN);
	int nHeight = GetSystemMetrics(SM_CYSCREEN); 

	hMemDC = ::CreateCompatibleDC(hScrDC); 

	BITMAPINFO bi; 
	ZeroMemory(&bi, sizeof(BITMAPINFO));
	bi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
	bi.bmiHeader.biWidth = nWidth;
	bi.bmiHeader.biHeight = nHeight;
	bi.bmiHeader.biPlanes = 1;
	bi.bmiHeader.biBitCount = 24;

	HBITMAP bitmap = ::CreateDIBSection(hMemDC, &bi, DIB_RGB_COLORS, (LPVOID*)&lpBitmapBits, NULL, 0);
	HGDIOBJ oldbmp = ::SelectObject(hMemDC, bitmap); 

	::BitBlt(hMemDC, 0, 0, nWidth, nHeight, hScrDC, 0, 0, SRCCOPY);

	BITMAPFILEHEADER bh;
	ZeroMemory(&bh, sizeof(BITMAPFILEHEADER));
	bh.bfType = 0x4d42; //bitmap 
	bh.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
	bh.bfSize = bh.bfOffBits + ((nWidth*nHeight)*3);

	CFile file;
	if(file.Open(szFileName, CFile::modeCreate | CFile::modeWrite))
	{ 
		file.Write(&bh, sizeof(BITMAPFILEHEADER));
		file.Write(&(bi.bmiHeader), sizeof(BITMAPINFOHEADER));
		file.Write(lpBitmapBits, 3 * nWidth * nHeight);
		file.Close();
	}

	::SelectObject(hMemDC, oldbmp);
	::DeleteObject(bitmap);
	::DeleteObject(hMemDC);
	::ReleaseDC(NULL, hScrDC);
}