import pickle
import os
import numpy as np


def read_pickle(pkl_path):
    with open(pkl_path, 'rb') as f:
        return pickle.load(f)


def save_pickle(data, pkl_path):
    os.system('mkdir -p {}'.format(os.path.dirname(pkl_path)))
    with open(pkl_path, 'wb') as f:
        pickle.dump(data, f)


def project(xyz, K, RT):
    """
    xyz: [N, 3]
    K: [3, 3]
    RT: [3, 4]
    """
    xyz = np.dot(xyz, RT[:, :3].T) + RT[:, 3:].T
    xyz = np.dot(xyz, K.T)
    xy = xyz[:, :2] / xyz[:, 2:]
    return xy