cartographer源码分析(33)-io-ply_writing_points_processor.h

源码可在https://github.com/learnmoreonce/SLAM 下载

文件:ply_writing_points_processor.h#include "cartographer/common/lua_parameter_dictionary.h"#include "cartographer/io/file_writer.h"#include "cartographer/io/points_processor.h"namespace cartographer {namespace io {/*PlyWritingPointsProcessor是PointsProcessor的第五个子类(5).PlyWritingPointsProcessor负责将点云point以PLY的格式写入磁盘.*/// Streams a PLY file to disk. The header is written in 'Flush'.class PlyWritingPointsProcessor : public PointsProcessor { public:  constexpr static const char* kConfigurationFileActionName = "write_ply";  // 指定文件写入的工厂和流水线next指针。  PlyWritingPointsProcessor(std::unique_ptr<FileWriter> file,                            PointsProcessor* next);  static std::unique_ptr<PlyWritingPointsProcessor> FromDictionary(      FileWriterFactory file_writer_factory,      common::LuaParameterDictionary* dictionary, PointsProcessor* next);  ~PlyWritingPointsProcessor() override {}  PlyWritingPointsProcessor(const PlyWritingPointsProcessor&) = delete;  PlyWritingPointsProcessor& operator=(const PlyWritingPointsProcessor&) =      delete;//按照ply格式写点云信息 。然后直接流水线到下一PointsProcessor  void Process(std::unique_ptr<PointsBatch> batch) override;  FlushResult Flush() override; private:  PointsProcessor* const next_;  int64 num_points_;  bool has_colors_;//是否是RGB  std::unique_ptr<FileWriter> file_;};}  // namespace io}  // namespace cartographer

ply_writing_points_processor.cc#include "cartographer/io/ply_writing_points_processor.h"#include <iomanip>#include <sstream>#include <string>#include "cartographer/common/lua_parameter_dictionary.h"#include "cartographer/common/make_unique.h"#include "cartographer/io/points_batch.h"#include "glog/logging.h"namespace cartographer {namespace io {namespace {/*按照ply格式写入ply的head信息.此函数在最后写入.why?num_points_只有最后才知道.之前尚未统计完成.*/// Writes the PLY header claiming 'num_points' will follow it into// 'output_file'.void WriteBinaryPlyHeader(const bool has_color, const int64 num_points,                          FileWriter* const file_writer) {  string color_header = !has_color ? ""                                   : "property uchar red\n"                                     "property uchar green\n"                                     "property uchar blue\n";  std::ostringstream stream;  stream << "ply\n"         << "format binary_little_endian 1.0\n"         << "comment generated by Cartographer\n"         << "element vertex " << std::setw(15) << std::setfill('0')         << num_points << "\n"         << "property float x\n"         << "property float y\n"         << "property float z\n"         << color_header << "end_header\n";  const string out = stream.str();  CHECK(file_writer->WriteHeader(out.data(), out.size()));}/*往file_writer写入某一point对应的{x,y,z}*/void WriteBinaryPlyPointCoordinate(const Eigen::Vector3f& point,                                   FileWriter* const file_writer) {  char buffer[12];  memcpy(buffer, &point[0], sizeof(float));  memcpy(buffer + 4, &point[1], sizeof(float));  memcpy(buffer + 8, &point[2], sizeof(float));  CHECK(file_writer->Write(buffer, 12));}/*往file_writer写入rgb值*/void WriteBinaryPlyPointColor(const Color& color,                              FileWriter* const file_writer) {  CHECK(file_writer->Write(reinterpret_cast<const char*>(color.data()),                           color.size()));}}  // namespace/*根据.lua文件的filename创建file_writer_factory*/std::unique_ptr<PlyWritingPointsProcessor>PlyWritingPointsProcessor::FromDictionary(    FileWriterFactory file_writer_factory,    common::LuaParameterDictionary* const dictionary,    PointsProcessor* const next) {  return common::make_unique<PlyWritingPointsProcessor>(      file_writer_factory(dictionary->GetString("filename")), next);}/*构造函数,默认点云数是0,无rgb值*/PlyWritingPointsProcessor::PlyWritingPointsProcessor(    std::unique_ptr<FileWriter> file_writer, PointsProcessor* const next)    : next_(next),      num_points_(0),      has_colors_(false),      file_(std::move(file_writer)) {}/*在最后阶段才写入head,但不是在文件最后写入head,而是out_.seekp(0); 偏移到0处*/PointsProcessor::FlushResult PlyWritingPointsProcessor::Flush() {  WriteBinaryPlyHeader(has_colors_, num_points_, file_.get());  CHECK(file_->Close()) << "Closing PLY file_writer failed.";  switch (next_->Flush()) {    case FlushResult::kFinished:      return FlushResult::kFinished;    case FlushResult::kRestartStream:      LOG(FATAL) << "PLY generation must be configured to occur after any "                    "stages that require multiple passes.";  }  LOG(FATAL);}/*真正的写入点云PointsBatch,整个类的核心在这个函数.*/void PlyWritingPointsProcessor::Process(std::unique_ptr<PointsBatch> batch) {  if (batch->points.empty()) { //点云为空,则不写入磁盘,直接进行下一Process环节.    next_->Process(std::move(batch));    return;  }  if (num_points_ == 0) {//点云num为0则写入rgb,和head    has_colors_ = !batch->colors.empty();    WriteBinaryPlyHeader(has_colors_, 0, file_.get());    //file_.get()获取指针指针对应的raw指针  }  if (has_colors_) { //rgb的vector长度和point的vecor长度必须一致.    CHECK_EQ(batch->points.size(), batch->colors.size())        << "First PointsBatch had colors, but encountered one without. "           "frame_id: "        << batch->frame_id;  }//函数核心,开始写入每一个point.  for (size_t i = 0; i < batch->points.size(); ++i) {    WriteBinaryPlyPointCoordinate(batch->points[i], file_.get());    if (has_colors_) {      WriteBinaryPlyPointColor(batch->colors[i], file_.get());    }    ++num_points_;  }  next_->Process(std::move(batch)); //继续流水线操作.}}  // namespace io}  // namespace cartographer

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