图片翻转：

def random_flip(img, y_random=False, x_random=False,
                return_param=False, copy=False):

    y_flip, x_flip = False, False
    if y_random:
        y_flip = random.choice([True, False])
    if x_random:
        x_flip = random.choice([True, False])

    if y_flip:
        img = img[:, ::-1, :]
    if x_flip:
        img = img[:, :, ::-1]

    if copy:
        img = img.copy()

    if return_param:
        return img, {'y_flip': y_flip, 'x_flip': x_flip}
    else:
        return img

bbox翻转：

def flip_bbox(bbox, size, y_flip=False, x_flip=False):

    H, W = size
    bbox = bbox.copy()
    if y_flip:
        y_max = H - bbox[:, 0]
        y_min = H - bbox[:, 2]
        bbox[:, 0] = y_min
        bbox[:, 2] = y_max
    if x_flip:
        x_max = W - bbox[:, 1]
        x_min = W - bbox[:, 3]
        bbox[:, 1] = x_min
        bbox[:, 3] = x_max
    return bbox