修改orbslam2代码，加载二进制词典文件，加速词典加载速度

修改orbslam2代码，加载二进制词典文件，加速词典加载速度

0.在ORB_SLAM2下创建tools文件夹，放入bin_vocabulary.cc程序

#include <time.h>

#include "ORBVocabulary.h"
using namespace std;

bool load_as_text(ORB_SLAM2::ORBVocabulary* voc, const std::string infile);

void load_as_xml(ORB_SLAM2::ORBVocabulary* voc, const std::string infile);

void load_as_binary(ORB_SLAM2::ORBVocabulary* voc, const std::string infile);

void save_as_text(ORB_SLAM2::ORBVocabulary* voc, const std::string outfile);

void save_as_xml(ORB_SLAM2::ORBVocabulary* voc, const std::string outfile);

void save_as_binary(ORB_SLAM2::ORBVocabulary* voc, const std::string outfile);


int main(int argc, char **argv) {
  cout << "BoW load/save benchmark" << endl;
  ORB_SLAM2::ORBVocabulary* voc = new ORB_SLAM2::ORBVocabulary();

  load_as_text(voc, "Vocabulary/ORBvoc.txt");
  save_as_binary(voc, "Vocabulary/ORBvoc.bin");

  return 0;
}



bool load_as_text(ORB_SLAM2::ORBVocabulary* voc, const std::string infile) {
  clock_t tStart = clock();
  bool res = voc->loadFromTextFile(infile);
  printf("Loading fom text: %.2fs\n", (double)(clock() - tStart)/CLOCKS_PER_SEC);
  return res;
}

void load_as_xml(ORB_SLAM2::ORBVocabulary* voc, const std::string infile) {
  clock_t tStart = clock();
  voc->load(infile);
  printf("Loading fom xml: %.2fs\n", (double)(clock() - tStart)/CLOCKS_PER_SEC);
}

void load_as_binary(ORB_SLAM2::ORBVocabulary* voc, const std::string infile) {
  clock_t tStart = clock();
  voc->loadFromBinaryFile(infile);
  printf("Loading fom binary: %.2fs\n", (double)(clock() - tStart)/CLOCKS_PER_SEC);
}



void save_as_text(ORB_SLAM2::ORBVocabulary* voc, const std::string outfile) {
  clock_t tStart = clock();
  voc->saveToTextFile(outfile);
  printf("Saving as text: %.2fs\n", (double)(clock() - tStart)/CLOCKS_PER_SEC);
}

void save_as_xml(ORB_SLAM2::ORBVocabulary* voc, const std::string outfile) {
  clock_t tStart = clock();
  voc->save(outfile);
  printf("Saving as xml: %.2fs\n", (double)(clock() - tStart)/CLOCKS_PER_SEC);
}

void save_as_binary(ORB_SLAM2::ORBVocabulary* voc, const std::string outfile) {
  clock_t tStart = clock();
  voc->saveToBinaryFile(outfile);
  printf("Saving as binary: %.2fs\n", (double)(clock() - tStart)/CLOCKS_PER_SEC);
}

1.修改ORB_SLAM2下的CMakelist.txt

在末尾添加可执行文件
# Build tools
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR}/tools)
add_executable(bin_vocabulary tools/bin_vocabulary.cc)
target_link_libraries(bin_vocabulary ${PROJECT_NAME})

2.修改build.sh

在末尾添加

cd ..
echo "Converting vocabulary to binary"
./tools/bin_vocabulary

3.修改System.cc中加载词典的函数
DBow2中TemplatedVocabulary.h中添加词典加载方式
函数声明：

 bool loadFromBinaryFile(const std::string &filename);
 void saveToBinaryFile(const std::string &filename) const;  

函数定义：

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;
}


// --------------------------------------------------------------------------

template<class TDescriptor, class F>
void TemplatedVocabulary<TDescriptor,F>::saveToBinaryFile(const std::string &filename) const {
  fstream f;
  f.open(filename.c_str(), ios_base::out|ios::binary);
  unsigned int nb_nodes = m_nodes.size();
  float _weight;
  unsigned int size_node = sizeof(m_nodes[0].parent) + F::L*sizeof(char) + sizeof(_weight) + sizeof(bool);
  f.write((char*)&nb_nodes, sizeof(nb_nodes));
  f.write((char*)&size_node, sizeof(size_node));
  f.write((char*)&m_k, sizeof(m_k));
  f.write((char*)&m_L, sizeof(m_L));
  f.write((char*)&m_scoring, sizeof(m_scoring));
  f.write((char*)&m_weighting, sizeof(m_weighting));
  for(size_t i=1; i<nb_nodes;i++) {
	const Node& node = m_nodes[i];
	f.write((char*)&node.parent, sizeof(node.parent));
	f.write((char*)node.descriptor.data, F::L);
	_weight = node.weight; f.write((char*)&_weight, sizeof(_weight));
	bool is_leaf = node.isLeaf(); f.write((char*)&is_leaf, sizeof(is_leaf)); // i put this one at the end for alignement....
  }
  f.close();
}
//-----------------------------------------------------------------------

4.修改src下部分代码
src/PnPsolver.cc

  vAvailableIndices[idx] = vAvailableIndices.back();
  修改为
   vAvailableIndices[randi] = vAvailableIndices.back();

src/System.cc

最后一个头文件末添加：
#include <time.h>

bool has_suffix(const std::string &str, const std::string &suffix) {
  std::size_t index = str.find(suffix, str.size() - suffix.size());
  return (index != std::string::npos);
}

在mpVocabulary = new ORBVocabulary();前面添加 clock_t tStart = clock();

     clock_t tStart = clock();//添加时间----------
    // 加载txt文本文件，修改为加载bin二进制文件
    mpVocabulary = new ORBVocabulary();

注释bool bVocLoad = mpVocabulary->loadFromTextFile(strVocFile);这句代码，改为下面代码

bool bVocLoad = false; // chose loading method based on file extension
    if (has_suffix(strVocFile, ".txt"))
	  bVocLoad = mpVocabulary->loadFromTextFile(strVocFile);
	else
	  bVocLoad = mpVocabulary->loadFromBinaryFile(strVocFile);

在cout << “Vocabulary loaded!” << endl << endl;下面添加

    printf("Vocabulary loaded in %.2fs\n", (double)(clock() - tStart)/CLOCKS_PER_SEC);

我使用时自己训练的一个小型词典文件
Loading fom text: 3.47s
Saving as binary: 0.06s

运行数据集加载不同文件时

参考链接：https://blog.csdn.net/weixin_47074246/article/details/109185504