import numpy as np

class BoundBox:

    def __init__(self, classes):

        self.x, self.y = float(), float()

        self.w, self.h = float(), float()

        self.c = float()

        self.class_num = classes

        self.probs = np.zeros((classes,))

def overlap(x1, w1, x2, w2):

    l1 = x1 - w1 / 2.;

    l2 = x2 - w2 / 2.;

    left = max(l1, l2)

    r1 = x1 + w1 / 2.;

    r2 = x2 + w2 / 2.;

    right = min(r1, r2)

    return right - left;

def box_intersection(a, b):

    w = overlap(a.x, a.w, b.x, b.w);

    h = overlap(a.y, a.h, b.y, b.h);

    if w < 0 or h < 0: return 0;

    area = w * h;

    return area;

def box_union(a, b):

    i = box_intersection(a, b);

    u = a.w * a.h + b.w * b.h - i;

    return u;

def box_iou(a, b):

    return box_intersection(a, b) / box_union(a, b);

def prob_compare(box):

    return box.probs[box.class_num]

def prob_compare2(boxa, boxb):

    if (boxa.pi < boxb.pi):

        return 1

    elif (boxa.pi == boxb.pi):

        return 0

    else:

        return -1