step9

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        "# Basing my code on Chapter07/Calculating_intersection_over_union.ipynb and pages 237-238\n",
        "\n",
        "def obtain_iou(box1, box2):\n",
        "    \"\"\"Calculate the Intersection over Union (IoU) between two bounding boxes.\"\"\"\n",
        "    x1_intersection = max(box1[0], box2[0])\n",
        "    y1_intersection = max(box1[1], box2[1])       # These four lines simply get the top left and bottom right of the intersection rectangle\n",
        "    x2_intersection = min(box1[2], box2[2])\n",
        "    y2_intersection = min(box1[3], box2[3])\n",
        "\n",
        "    intersection_width = max(0, x2_intersection - x1_intersection)\n",
        "    intersection_height = max(0, y2_intersection - y1_intersection)    # getting height and width of the intersecting rectangle while using max to avoid overlap\n",
        "    intersection_area = intersection_width * intersection_height              # and then getting its area\n",
        "\n",
        "    box1_area = (box1[2] - box1[0]) * (box1[3] - box1[1])\n",
        "    box2_area = (box2[2] - box2[0]) * (box2[3] - box2[1])\n",
        "\n",
        "    union_area = box1_area + box2_area - intersection_area      # avoid including intersecting area\n",
        "\n",
        "    iou = intersection_area / union_area if union_area > 0 else 0 # This is a slight change to the textbook way -- I'm guarding against an undefined value\n",
        "    return iou"
      ]
    }
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