# -*- coding: utf-8 -*-
"""1705.159.252

Automatically generated by Colab.

Original file is located at
    https://colab.research.google.com/drive/1SzDicEXWRqpiPKW8HkGdpUFIT-SbS8Xd
"""

import torch

def intersection_over_union(boxes_preds, boxes_labels, box_format="midpoint"):

  if box_format == "midpoint":
    box1_x1 = boxes_preds[..., 0:1] - boxes_preds[..., 2:3] / 2
    box1_y1 = boxes_preds[..., 1:2] - boxes_preds[..., 3:4] / 2
    box1_x2 = boxes_preds[..., 0:1] + boxes_preds[..., 2:3] / 2
    box1_y2 = boxes_preds[..., 1:2] + boxes_preds[..., 3:4] / 2
    box2_x1 = boxes_labels[..., 0:1] - boxes_labels[..., 2:3] / 2
    box2_y1 = boxes_labels[..., 1:2] - boxes_labels[..., 3:4] / 2
    box2_x2 = boxes_labels[..., 0:1] + boxes_labels[..., 2:3] / 2
    box2_y2 = boxes_labels[..., 1:2] + boxes_labels[..., 3:4] / 2

  elif box_format == "corners":
    box1_x1 = boxes_preds[..., 0:1]
    box_y1 = boxes_preds[..., 1:2]
    box1_x2 = boxes_preds[..., 2:3]
    box1_y2 = boxes_preds[..., 3:4]
    box2_x1 = boxes_labels[...,0:1]
    box2_y1 = boxes_labels[...,1:2]
    box2_x2 = boxes_labels[...,2:3]
    box2_y2 = boxes_labels[...,3:4]

  x1 = torch.max(box1_x1, box2_x1)
  y1 = torch.max(box1_y1, box2_y1)
  x2 = torch.min(box1_x2, box2_x2)
  y2 = torch.min(box1_y2, box2_y2)

  intersection = (x2 - x1).clamp(0) * (y2- y1).clamp(0)

  box1_area = abs((box1_x2 - box1_x1) * (box1_y1 - box1_y2))
  box2_area = abs((box2_x2 - box2_x1) * (box2_y1 - box2_y2))

  return intersection / (box1_area + box2_area - intersection + 1e-6)