IOU rotated rect openCV

gistfile1.txt

  // compute intersection area
  std::vector<cv::Point2f> intersections_unsorted;
  std::vector<cv::Point2f> intersections;
  cv::rotatedRectangleIntersection(bounding_rect, detection_bbox, intersections_unsorted);
  if (intersections_unsorted.size() < 3) {
    return GT_score{};
  }
  // need to sort the vertices CW or CCW
  cv::convexHull(intersections_unsorted, intersections);

  // Shoelace formula
  float intersection_area = 0;
  for (unsigned int i = 0; i < intersections.size(); ++i) {
    const auto& pt = intersections[i];
    const unsigned int i_next = (i + 1) == intersections.size() ? 0 : (i + 1);
    const auto& pt_next = intersections[i_next];
    intersection_area += (pt.x * pt_next.y - pt_next.x * pt.y);
  }
  intersection_area = std::abs(intersection_area) / 2;

  // compute union area
  const float area_GT = bounding_rect.size.area();
  const float area_detection = detection_bbox.size.area();
  const float union_area = area_GT + area_detection - intersection_area;
  
  // intersection over union
  const float overlap_score = intersection_area / union_area;