一、IOU函数

def IOU(box1, box2):
    #box2 = [x1,y1,h1,w1]
    #box2 = [x2,y2,h2,w2]
    x1,y1,h1,w1 = box1
    x2,y2,h2,w2 = box2
    # 用四个角坐标计算比较方便
    left1 = x1 - w1/2
    right1 = x1 + w1/2
    top1 = y1 - h1/2
    bottom2 = y1 + h1/2

    left2 = x2 - w2/2
    right2 = x2 + w2/2
    top2 = y2 - h2/2
    bottom2 = y2 + h2/2
    # 相交部分的四个角坐标
    left = max(left1, left2)
    top = max(top1,top2)
    right = min(right1, right2)
    bottom = min(bottom1, bottom2)
    #相交部分的面积
    inter = max(0, right - left) * max(0, bottom - top)
    area1 = h1 * w1
    area2 = h2 * w2
    union = area1 + area2 - inter
    iou = inter / union
    return iou

二、Softmax和Cross Entropy

三、Max Pooling / Average Pooling

四、Focal Loss

五、NMS

六、ResNet的basic block