text: # Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  import numpy as np
  from shapely.geometry import Polygon
  """
  :param det_x: [1, N] Xs of detection's vertices 
  :param det_y: [1, N] Ys of detection's vertices
  :param gt_x: [1, N] Xs of groundtruth's vertices
  :param gt_y: [1, N] Ys of groundtruth's vertices
  
  ##############
  All the calculation of 'AREA' in this script is handled by:
  1) First generating a binary mask with the polygon area filled up with 1's
  2) Summing up all the 1's
  """
  
  
  def area(x, y):
      polygon = Polygon(np.stack([x, y], axis=1))
      return float(polygon.area)
  
  
  def approx_area_of_intersection(det_x, det_y, gt_x, gt_y):
      """
      This helper determine if both polygons are intersecting with each others with an approximation method.
      Area of intersection represented by the minimum bounding rectangular [xmin, ymin, xmax, ymax]
      """
      det_ymax = np.max(det_y)
      det_xmax = np.max(det_x)
      det_ymin = np.min(det_y)
      det_xmin = np.min(det_x)
  
      gt_ymax = np.max(gt_y)
      gt_xmax = np.max(gt_x)
      gt_ymin = np.min(gt_y)
      gt_xmin = np.min(gt_x)
  
      all_min_ymax = np.minimum(det_ymax, gt_ymax)
      all_max_ymin = np.maximum(det_ymin, gt_ymin)
  
      intersect_heights = np.maximum(0.0, (all_min_ymax - all_max_ymin))
  
      all_min_xmax = np.minimum(det_xmax, gt_xmax)
      all_max_xmin = np.maximum(det_xmin, gt_xmin)
      intersect_widths = np.maximum(0.0, (all_min_xmax - all_max_xmin))
  
      return intersect_heights * intersect_widths
  
  
  def area_of_intersection(det_x, det_y, gt_x, gt_y):
      p1 = Polygon(np.stack([det_x, det_y], axis=1)).buffer(0)
      p2 = Polygon(np.stack([gt_x, gt_y], axis=1)).buffer(0)
      return float(p1.intersection(p2).area)
  
  
  def area_of_union(det_x, det_y, gt_x, gt_y):
      p1 = Polygon(np.stack([det_x, det_y], axis=1)).buffer(0)
      p2 = Polygon(np.stack([gt_x, gt_y], axis=1)).buffer(0)
      return float(p1.union(p2).area)
  
  
  def iou(det_x, det_y, gt_x, gt_y):
      return area_of_intersection(det_x, det_y, gt_x, gt_y) / (
          area_of_union(det_x, det_y, gt_x, gt_y) + 1.0)
  
  
  def iod(det_x, det_y, gt_x, gt_y):
      """
      This helper determine the fraction of intersection area over detection area
      """
      return area_of_intersection(det_x, det_y, gt_x, gt_y) / (
          area(det_x, det_y) + 1.0)
  