ORB SLAM3加载Vocabulary更快ORBvoc.bin

ORBSLAM3_1.0版本词袋还是ORBvoc.txt，加载时间比较慢，这里教你修改成ORBvoc.bin加载，1秒内完成加载。

• 将ORBvoc.bin拷贝到Vocabulary文件夹下，ORBvoc.bin百度云盘下载地址 密码idr0,记得解压缩。

• 修改ORB_SLAM3/src的System.cc的82行：

  mpVocabulary = new ORBVocabulary();
  //bool bVocLoad = mpVocabulary->loadFromTextFile(strVocFile); //txt加载
  bool bVocLoad = mpVocabulary->loadFromBinaryFile(strVocFile);   //bin加载

• ORB_SLAM3/Thirdparty/DBoW2/DBoW2/的TemplatedVocabulary.h里增加函数：

/**函数声明 * Loads the vocabulary from a binary file * @param filename */
  bool loadFromBinaryFile(const std::string &filename);
 

// --------------------------------------------------------------------------
  //函数定义，可以放在对应的loadFromTextFile函数下面
 template<class TDescriptor, class F>
    bool TemplatedVocabulary<TDescriptor,F>::loadFromBinaryFile(const std::string &filename) {
    
      fstream f;
      f.open(filename.c_str(), ios_base::in|ios::binary);
      unsigned int nb_nodes, size_node;
      f.read((char*)&nb_nodes, sizeof(nb_nodes));
      f.read((char*)&size_node, sizeof(size_node));
      f.read((char*)&m_k, sizeof(m_k));
      f.read((char*)&m_L, sizeof(m_L));
      f.read((char*)&m_scoring, sizeof(m_scoring));
      f.read((char*)&m_weighting, sizeof(m_weighting));
      createScoringObject();
      
      m_words.clear();
      m_words.reserve(pow((double)m_k, (double)m_L + 1));
      m_nodes.clear();
      m_nodes.resize(nb_nodes+1);
      m_nodes[0].id = 0;
      char buf[size_node]; int nid = 1;
      while (!f.eof()) {
    
    	f.read(buf, size_node);
    	m_nodes[nid].id = nid;
    	// FIXME
    	const int* ptr=(int*)buf;
    	m_nodes[nid].parent = *ptr;
    	//m_nodes[nid].parent = *(const int*)buf;
    	m_nodes[m_nodes[nid].parent].children.push_back(nid);
    	m_nodes[nid].descriptor = cv::Mat(1, F::L, CV_8U);
    	memcpy(m_nodes[nid].descriptor.data, buf+4, F::L);
    	m_nodes[nid].weight = *(float*)(buf+4+F::L);
    	if (buf[8+F::L]) {
     // is leaf
    	  int wid = m_words.size();
    	  m_words.resize(wid+1);
    	  m_nodes[nid].word_id = wid;
    	  m_words[wid] = &m_nodes[nid];
    	}
    	else
    	  m_nodes[nid].children.reserve(m_k);
    	nid+=1;
      }
      f.close();
      return true;
    }

• 之后重新编译DBoW2和整个ORBSLAM3程序需要注意的是只编译ros模块不行。