Record hand torn iou interview code

In this function, boxAand boxBare lists containing four integers representing the four coordinates of the bounding box: [start x, start y, end x, end y].

This function first calculates the intersection area of ​​two bounding boxes, then calculates the area of ​​each bounding box and the union area of ​​the two bounding boxes, and finally divides the intersection area by the union area, and the result is IOU.

def bbox_intersection_over_union(boxA, boxB):
    # 确定每个边界框的 (y, x) 的 (开始，结束) 坐标
    xA = max(boxA[0], boxB[0])
    yA = max(boxA[1], boxB[1])
    xB = min(boxA[2], boxB[2])
    yB = min(boxA[3], boxB[3])

    # 计算交集的面积
    interArea = max(0, xB - xA + 1) * max(0, yB - yA + 1)

    # 计算每个边界框的面积
    boxAArea = (boxA[2] - boxA[0] + 1) * (boxA[3] - boxA[1] + 1)
    boxBArea = (boxB[2] - boxB[0] + 1) * (boxB[3] - boxB[1] + 1)

    # 计算并集的面积
    unionArea = boxAArea + boxBArea - interArea

    # 计算交并比
    iou = interArea / float(unionArea)

    # 返回交并比
    return iou

• xAis the larger of the upper-left x-coordinates of the two bounding boxes, representing the upper-left x-coordinate of the intersection.
• yAis the larger value of the y-coordinates of the upper-left corners of the two bounding boxes, indicating the y-coordinates of the upper-left corner of the intersection.
• xBis the smaller of the lower-right x-coordinates of the two bounding boxes, representing the lower-right x-coordinate of the intersection.
• yBis the smaller value of the lower-right y-coordinates of the two bounding boxes, representing the lower-right y-coordinate of the intersection.

These calculations are to find the coordinate extent of the intersection of two bounding boxes, which will be used to calculate the area of ​​the intersection. If xAgreater than xBor yAgreater than yB, it means that the two bounding boxes do not intersect, and the area of ​​the intersection will be 0 at this time.