python实现IoU

IoU公式

重合程度通过检测评价函数IoU（Intersection over Union）来判断，IoU计算公式如下：

参数说明：

python实现IoU源码：

import numpy as np

# get IoU overlap ratio
def iou(a, b):
	# get area of a
    area_a = (a[2] - a[0]) * (a[3] - a[1])
	# get area of b
    area_b = (b[2] - b[0]) * (b[3] - b[1])

	# get left top x of IoU
    iou_x1 = np.maximum(a[0], b[0])
	# get left top y of IoU
    iou_y1 = np.maximum(a[1], b[1])
	# get right bottom of IoU
    iou_x2 = np.minimum(a[2], b[2])
	# get right bottom of IoU
    iou_y2 = np.minimum(a[3], b[3])

	# get width of IoU
    iou_w = iou_x2 - iou_x1
	# get height of IoU
    iou_h = iou_y2 - iou_y1

	# get area of IoU
    area_iou = iou_w * iou_h
	# get overlap ratio between IoU and all area
    iou = area_iou / (area_a + area_b - area_iou)

    return iou

# [x1, y1, x2, y2]
a = np.array((50, 50, 150, 150), dtype=np.float32)

b = np.array((60, 60, 170, 160), dtype=np.float32)

print(iou(a, b))