cartographer源码分析(37)-io-pcd_writing_points_processor.h

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

文件:pcd_writing_points_processor.h#include <fstream>#include "cartographer/common/lua_parameter_dictionary.h"#include "cartographer/io/file_writer.h"#include "cartographer/io/points_processor.h"/*点云是目标表面特性的海量点集合。根据激光测量原理得到的点云，包括三维坐标（XYZ）和激光反射强度（Intensity）。根据摄影测量原理得到的点云，包括三维坐标（XYZ）和颜色信息（RGB）。结合激光测量和摄影测量原理得到点云，包括三维坐标（XYZ）、激光反射强度（Intensity）和颜色信息（RGB）。在获取物体表面每个采样点的空间坐标后，得到的是一个点的集合，称之为“点云”(Point Cloud)。pcd文件存储了每个点的x,y,z坐标以及r,g,b,a颜色信息*/namespace cartographer {namespace io {/*PcdWritingPointsProcessor是PointsProcessor的第九个子类(9).PcdWritingPointsProcessor类将点云按照pcd格式存储在pcd文件中.1,构造函数初始化一个文件类名,2,成员函数FromDictionary 从配置文件读取 文件名3,Process()和Flush()负责写入文件4,数据成员next_指向 下一阶段的PointsProcessor点云处理类*/// Streams a PCD file to disk. The header is written in 'Flush'.class PcdWritingPointsProcessor : public PointsProcessor { public:  constexpr static const char* kConfigurationFileActionName = "write_pcd";  PcdWritingPointsProcessor(std::unique_ptr<FileWriter> file_writer,                            PointsProcessor* next);  static std::unique_ptr<PcdWritingPointsProcessor> FromDictionary(      FileWriterFactory file_writer_factory,      common::LuaParameterDictionary* dictionary, PointsProcessor* next);  ~PcdWritingPointsProcessor() override {}  PcdWritingPointsProcessor(const PcdWritingPointsProcessor&) = delete;  PcdWritingPointsProcessor& operator=(const PcdWritingPointsProcessor&) =      delete;  void Process(std::unique_ptr<PointsBatch> batch) override;  FlushResult Flush() override; private:  PointsProcessor* const next_;  int64 num_points_;  bool has_colors_;  std::unique_ptr<FileWriter> file_writer_;};}  // namespace io}  // namespace cartographer

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pcd_writing_points_processor.cc#include "cartographer/io/pcd_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 {/*PCD文件由文件头和数据域组成，文件头存储了点云数据的字段格式信息，如： ======================================== # .PCD v0.7 - Point Cloud Data file format VERSION 0.7 FIELDS x y z rgba SIZE 4 4 4 4 TYPE F F F U COUNT 1 1 1 1 WIDTH 640 HEIGHT 480 VIEWPOINT 0 0 0 0 1 0 0 POINTS 307200 DATA binary //下面是点云数据段 123.1 21.1 64.0...======================================== */// Writes the PCD header claiming 'num_points' will follow it into// 'output_file'.void WriteBinaryPcdHeader(const bool has_color, const int64 num_points,                          FileWriter* const file_writer) {  string color_header_field = !has_color ? "" : " rgb";  string color_header_type = !has_color ? "" : " U";  string color_header_size = !has_color ? "" : " 4";  string color_header_count = !has_color ? "" : " 1";  std::ostringstream stream;  stream << "# generated by Cartographer\n"         << "VERSION .7\n"         << "FIELDS x y z" << color_header_field << "\n"         << "SIZE 4 4 4" << color_header_size << "\n"         << "TYPE F F F" << color_header_type << "\n"         << "COUNT 1 1 1" << color_header_count << "\n"         << "WIDTH " << std::setw(15) << std::setfill('0') << num_points << "\n"         << "HEIGHT 1\n"         << "VIEWPOINT 0 0 0 1 0 0 0\n"         << "POINTS " << std::setw(15) << std::setfill('0') << num_points         << "\n"         << "DATA binary\n";  const string out = stream.str();  file_writer->WriteHeader(out.data(), out.size());}//{x,y,z}写入文件void WriteBinaryPcdPointCoordinate(const Eigen::Vector3f& point,                                   FileWriter* const file_writer) {  char buffer[12];  memcpy(buffer, &point[0], sizeof(float));  memcpy(buffer + 4, &point[1], sizeof(float)); //64机,float:4位  memcpy(buffer + 8, &point[2], sizeof(float));  CHECK(file_writer->Write(buffer, 12));}void WriteBinaryPcdPointColor(const Color& color,                              FileWriter* const file_writer) {  char buffer[4];  buffer[0] = color[2];  buffer[1] = color[1];  buffer[2] = color[0];  buffer[3] = 0;  CHECK(file_writer->Write(buffer, 4));}}  // namespacestd::unique_ptr<PcdWritingPointsProcessor>PcdWritingPointsProcessor::FromDictionary(    FileWriterFactory file_writer_factory,    common::LuaParameterDictionary* const dictionary,    PointsProcessor* const next) {  return common::make_unique<PcdWritingPointsProcessor>(      file_writer_factory(dictionary->GetString("filename")), next);}PcdWritingPointsProcessor::PcdWritingPointsProcessor(    std::unique_ptr<FileWriter> file_writer, PointsProcessor* const next)    : next_(next),      num_points_(0),      has_colors_(false),      file_writer_(std::move(file_writer)) {}PointsProcessor::FlushResult PcdWritingPointsProcessor::Flush() {  WriteBinaryPcdHeader(has_colors_, num_points_, file_writer_.get());  //调用Flush()才写入head信息:此时才知道num_points_的值  CHECK(file_writer_->Close());  switch (next_->Flush()) {    case FlushResult::kFinished:      return FlushResult::kFinished;    case FlushResult::kRestartStream://不能多次传递同一数据.      LOG(FATAL) << "PCD generation must be configured to occur after any "                    "stages that require multiple passes.";  }  LOG(FATAL);}/*核心函数,按照{x,y,z}写入文件*/void PcdWritingPointsProcessor::Process(std::unique_ptr<PointsBatch> batch) {  if (batch->points.empty()) {    next_->Process(std::move(batch));    return;  }  if (num_points_ == 0) {    has_colors_ = !batch->colors.empty();    WriteBinaryPcdHeader(has_colors_, 0, file_writer_.get());  }  for (size_t i = 0; i < batch->points.size(); ++i) {    WriteBinaryPcdPointCoordinate(batch->points[i], file_writer_.get());    if (!batch->colors.empty()) {      WriteBinaryPcdPointColor(batch->colors[i], file_writer_.get());    }    ++num_points_;//统计处理了多少points  }  next_->Process(std::move(batch));}}  // namespace io}  // namespace cartographer

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