屏幕截图的函数

HBITMAP CopyScreenToBitmap(LPRECT lpRect,BOOL bSave)
//lpRect 代表选定区域
{
	HDC       hScrDC, hMemDC;      
	// 屏幕和内存设备描述表
	HBITMAP    hBitmap, hOldBitmap;   
	// 位图句柄
	int       nX, nY, nX2, nY2;      
	// 选定区域坐标
	int       nWidth, nHeight;
	
	// 确保选定区域不为空矩形
	if (IsRectEmpty(lpRect))
		return NULL;
	//为屏幕创建设备描述表
	hScrDC = CreateDC("DISPLAY", NULL, NULL, NULL);

	//为屏幕设备描述表创建兼容的内存设备描述表
	hMemDC = CreateCompatibleDC(hScrDC);
	// 获得选定区域坐标
	nX = lpRect->left;
	nY = lpRect->top;
	nX2 = lpRect->right;
	nY2 = lpRect->bottom;

	//确保选定区域是可见的
	if (nX < 0)
		nX = 0;
	if (nY < 0)
		nY = 0;
	if (nX2 > m_xScreen)
		nX2 = m_xScreen;
	if (nY2 > m_yScreen)
		nY2 = m_yScreen;
	nWidth = nX2 - nX;
	nHeight = nY2 - nY;
	// 创建一个与屏幕设备描述表兼容的位图
	hBitmap = CreateCompatibleBitmap(hScrDC, nWidth, nHeight);
	// 把新位图选到内存设备描述表中
	hOldBitmap = (HBITMAP)SelectObject(hMemDC, hBitmap);
	// 把屏幕设备描述表拷贝到内存设备描述表中
	if(bSave)
	{
		CDC dcCompatible;
		dcCompatible.CreateCompatibleDC(CDC::FromHandle(hMemDC));
		dcCompatible.SelectObject(m_pBitmap);
        
		BitBlt(hMemDC, 0, 0, nWidth, nHeight,dcCompatible, nX, nY, SRCCOPY);

	}
	else
	{
		BitBlt(hMemDC, 0, 0, nWidth, nHeight,hScrDC, nX, nY, SRCCOPY);
	}

	hBitmap = (HBITMAP)SelectObject(hMemDC, hOldBitmap);
	//得到屏幕位图的句柄
	//清除 
	DeleteDC(hScrDC);
	DeleteDC(hMemDC);
	// 返回位图句柄
	if(bSave)
	{
				
		if (OpenClipboard()) 
		{
        //清空剪贴板
        EmptyClipboard();
        //把屏幕内容粘贴到剪贴板上,
        //hBitmap 为刚才的屏幕位图句柄
        SetClipboardData(CF_BITMAP, hBitmap);
        //关闭剪贴板
        CloseClipboard();
      }
	}
	return hBitmap;
}