MFC - 最小化或者最大化图片不显示的解决办法

void CserialcommunicationDlg::OnPaint()
{
	if (IsIconic())
	{
		CPaintDC dc(this); // 用于绘制的设备上下文

		SendMessage(WM_ICONERASEBKGND, reinterpret_cast<WPARAM>(dc.GetSafeHdc()), 0);

		// 使图标在工作区矩形中居中
		int cxIcon = GetSystemMetrics(SM_CXICON);
		int cyIcon = GetSystemMetrics(SM_CYICON);
		CRect rect;
		GetClientRect(&rect);
		int x = (rect.Width() - cxIcon + 1) / 2;
		int y = (rect.Height() - cyIcon + 1) / 2;

		// 绘制图标
		dc.DrawIcon(x, y, m_hIcon);
	}
	else
	{	
		CPaintDC dc(this);
		CRect   myrect;
		GetClientRect(&myrect);
		CDC   dcMem;
		dcMem.CreateCompatibleDC(&dc);
		CBitmap   bmpBackground;
		bmpBackground.LoadBitmap(IDB_BITMAP2);   //IDB_BITMAP3是背景图的ID 
		BITMAP   bitmap;
		bmpBackground.GetBitmap(&bitmap);
		CBitmap   *pbmpOld = dcMem.SelectObject(&bmpBackground);
		dc.StretchBlt(0, 0, myrect.Width(), myrect.Height(), &dcMem, 0, 0,
			bitmap.bmWidth, bitmap.bmHeight, SRCCOPY);

		CDialogEx::OnPaint();

	}
	if (m_display_flag)
	{
		DrawMat(resultimage, IDC_STATIC_PICTURE);
	}
	UpdateWindow();
}

void CserialcommunicationDlg::DrawMat(cv::Mat & img, UINT nID)
{
	cv::Mat imgTmp;
	CRect rect;
	GetDlgItem(nID)->GetClientRect(&rect);  // 获取控件大小
	cv::resize(img, imgTmp, cv::Size(rect.Width(), rect.Height()));// 缩小或放大Mat并备份

	// 转一下格式 ,这段可以放外面,
	switch (imgTmp.channels())
	{
	case 1:
		cv::cvtColor(imgTmp, imgTmp, CV_GRAY2BGRA); // GRAY单通道
		break;
	case 3:
		cv::cvtColor(imgTmp, imgTmp, CV_BGR2BGRA);  // BGR三通道
		break;
	default:
		break;
	}

	int pixelBytes = imgTmp.channels()*(imgTmp.depth() + 1); // 计算一个像素多少个字节
															 // 制作bitmapinfo(数据头)
	BITMAPINFO bitInfo;
	bitInfo.bmiHeader.biBitCount = 8 * pixelBytes;
	bitInfo.bmiHeader.biWidth = imgTmp.cols;
	bitInfo.bmiHeader.biHeight = -imgTmp.rows;
	bitInfo.bmiHeader.biPlanes = 1;
	bitInfo.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
	bitInfo.bmiHeader.biCompression = BI_RGB;
	bitInfo.bmiHeader.biClrImportant = 0;
	bitInfo.bmiHeader.biClrUsed = 0;
	bitInfo.bmiHeader.biSizeImage = 0;
	bitInfo.bmiHeader.biXPelsPerMeter = 0;
	bitInfo.bmiHeader.biYPelsPerMeter = 0;
	// Mat.data + bitmap数据头 -> MFC
	CDC *pDC = GetDlgItem(nID)->GetDC();
	::StretchDIBits(
		pDC->GetSafeHdc(),
		0, 0, rect.Width(), rect.Height(),
		0, 0, rect.Width(), rect.Height(),
		imgTmp.data,
		&bitInfo,
		DIB_RGB_COLORS,
		SRCCOPY
	);
	ReleaseDC(pDC);
}