OpenCV图像翻转和旋转

QString appPath = QCoreApplication::applicationDirPath();
  imagePath = appPath + "/A.jpg";
  img = cv::imread(imagePath.toStdString());
  if (img.empty())
    return;
  Mat dst;
  flip(img, dst, 0);//上下翻转
  imshow("flip0", dst);
  flip(img, dst, 1);//左右翻转
  imshow("flip1", dst);
  flip(img, dst, -1);//180°旋转
  imshow("flip-1", dst);
  int h = img.rows;
  int w = img.cols;
  Mat M = getRotationMatrix2D(Point2f(w / 2, h / 2), 45, 1.0);
  double cos = abs(M.at<double>(0, 0));
  double sin = abs(M.at<double>(0, 1));
  int nw = cos * w + sin * h;
  int nh = sin * w + cos * h;
  M.at<double>(0, 2) = M.at<double>(0, 2) + (nw / 2 - w / 2);
  M.at<double>(1, 2) = M.at<double>(1, 2) + (nh / 2 - h / 2);
  warpAffine(img, dst, M, Size(nw,nh),INTER_LINEAR,0,Scalar(255,0,0));
  imshow("rotate", dst);