螢幕截圖

void CMainFormDlg::GetScreenPic(Rect area, OUT Mat &img, float rate, bool gray) {

	CDC *pDC = GetDesktopWindow()->GetDC();//螢幕DC
	int BitPerPixel = pDC->GetDeviceCaps(BITSPIXEL);//獲得顏色模式
	int Width = MIN(pDC->GetDeviceCaps(HORZRES), area.width);
	int Height = MIN(pDC->GetDeviceCaps(VERTRES), area.height);


	CDC memDC;//記憶體DC
	memDC.CreateCompatibleDC(pDC);

	CBitmap memBitmap, *oldmemBitmap;//建立和螢幕相容的bitmap
	memBitmap.CreateCompatibleBitmap(pDC, Width, Height);

	oldmemBitmap = memDC.SelectObject(&memBitmap);//將memBitmap選入記憶體DC
	memDC.BitBlt(0, 0, Width, Height, pDC, area.x, area.y, SRCCOPY);//複製螢幕影象到記憶體DC

	BITMAP bmp;
	memBitmap.GetBitmap(&bmp);//獲得點陣圖資訊
	BITMAPINFOHEADER bih = { 0 };//點陣圖資訊頭
	bih.biBitCount = bmp.bmBitsPixel;//每個畫素位元組大小
	bih.biCompression = BI_RGB;
	bih.biHeight = bmp.bmHeight;//高度
	bih.biPlanes = 1;
	bih.biSize = sizeof(BITMAPINFOHEADER);
	bih.biSizeImage = bmp.bmWidthBytes * bmp.bmHeight;//影象資料大小
	bih.biWidth = bmp.bmWidth;//寬度

	BITMAPFILEHEADER bfh = { 0 };//點陣圖檔案頭
	bfh.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);//到點陣圖資料的偏移量
	bfh.bfSize = bfh.bfOffBits + bmp.bmWidthBytes * bmp.bmHeight;//檔案總的大小
	bfh.bfType = (WORD)0x4d42;

	//Mat(nHeight, nWidth, CV_8UC1, pImageData).copyTo(CCDImage[0]);
	byte * p = new byte[bmp.bmWidthBytes * bmp.bmHeight];//申請記憶體儲存點陣圖資料
	GetDIBits(memDC.m_hDC, (HBITMAP)memBitmap.m_hObject, 0, Height, p, (LPBITMAPINFO)&bih, DIB_RGB_COLORS);//獲取點陣圖資料

	Mat temp;
	flip(Mat(Height, Width, CV_8UC4, p), temp, 0);
	delete[] p;

	memDC.SelectObject(oldmemBitmap);
	memDC.DeleteDC();
	ReleaseDC(pDC);

	if (gray) {
		cvtColor(temp, temp, CV_BGRA2GRAY);
		resize(temp, img, Size(), rate, rate);
	} else {
		cvtColor(temp, temp, CV_BGRA2BGR);
		resize(temp, img, Size(), rate, rate);
	}
}