0x00 前言

rosbag是通过ros记录的数据格式，在使用ros框架的使用方便读写，但如果换了别的框架，就需要进行转换了。

直接用c++的流来读写是很不方便的，借用rosbag模块来读写比较方便

0x01获取rosbag中的topic

首先要知道rosbag里面包含的topic，可是使用ros的工具来查看

• 先启动roscore

roscore

• 然后在另一个terminal里面运行

rqt_bag 你的完整路径.bag

可以看到里面包含的很多topic

0x02 读取rosbag中指定的数据

c++代码

// main.cc
#include "rosbag/bag.h"
#include "rosbag/view.h"
#include "sensor_msgs/Imu.h"
#include "sensor_msgs/PointCloud2.h"
std::string src_bag = "/home/xxx/DataSet/2022-03-17/2022-03-17.bag";
std::string new_bag = "/home/xxx/DataSet/2022-03-17/imu_pcd.bag";
std::string imu_topic = "/imu/data_raw";
std::string pcd2_topic = "/hesai/pandar";

int main(int argc, char **argv) {
  rosbag::Bag i_bag, o_bag;
  i_bag.open(src_bag, rosbag::bagmode::Read);
  o_bag.open(new_bag, rosbag::bagmode::Write);
  std::vector<std::string> topics;
  topics.push_back(std::string(imu_topic));
  topics.push_back(std::string(pcd2_topic));
  rosbag::View view(i_bag, rosbag::TopicQuery(topics));
  // rosbag::View view(i_bag);
  for (auto m : view) {
    sensor_msgs::Imu::ConstPtr imu = m.instantiate<sensor_msgs::Imu>();
    if (imu == nullptr) {
      std::cout << "imu null " << std::endl;
    } else {
      std::cout << "imu stamp:" << imu->header.stamp << std::endl;
      o_bag.write(imu_topic, imu->header.stamp, imu);
    }
    sensor_msgs::PointCloud2::ConstPtr pcd =
        m.instantiate<sensor_msgs::PointCloud2>();
    if (pcd == nullptr) {
      std::cout << "pcd null " << std::endl;
    } else {
      std::cout << "pcd stamp:" << pcd->header.stamp << std::endl;
      o_bag.write(pcd2_topic, pcd->header.stamp, pcd);
    }
  }
  return 0;

CMakeList

cmake_minimum_required(VERSION 3.14)
project(to_rosbag)
set(CMAKE_BUILD_TYPE Debug)
set(CMAKE_CXX_STANDARD 14)

# ros pkg dep
set(ROS_DEP roscpp sensor_msgs rosbag)
# when create new message, build with message_generation
# find_package(catkin REQUIRED COMPONENTS message_generation ${ROS_DEP})
find_package(catkin REQUIRED COMPONENTS ${ROS_DEP})

# catkin_package() 是catkin提供的CMake的宏，这个指令是用来提供一些catkin的信息来创建pkg-config和CMake文件。
# 这个指令必须在 add_library() 或 add_executable()前执行， 这个指令有 5 个可选参数：
# INCLUDE_DIRS - 被这个package导出的include路径 
# LIBRARIES - 被这个package导出的library
# CATKIN_DEPENDS - 这个工程依赖的其他catkin projects 
# DEPENDS - 这个工程依赖的Non-catkin CMake projects 
# CFG_EXTRAS - 其他的构建选项。
# catkin_package(CATKIN_DEPENDS ${ROS_DEP} message_runtime)
catkin_package(CATKIN_DEPENDS ${ROS_DEP})


# file() 
aux_source_directory(convert_to_rosbag ALL_SRC)
add_executable(${PROJECT_NAME} ${ALL_SRC})
target_link_libraries(${PROJECT_NAME} PUBLIC ${catkin_LIBRARIES})
target_include_directories(${PROJECT_NAME} PUBLIC ./convert_to_rosbag ${catkin_INCLUDE_DIRS})

# 
set_target_properties(${PROJECT_NAME} PROPERTIES RUNTIME_OUTPUT_DIRECTORY ./)

package.xml

<?xml version="1.0"?>
<package format="3">
  <name>to_rosbag</name>
  <version>1.0.0</version>
  <description>
    c++ project with ros
  </description>
  <maintainer email="xxx@xxx.com">
  </maintainer>
  <license>Apache 2.0</license>
  
  <buildtool_depend>catkin</buildtool_depend>
  <!-- <build_depend>message_generation</build_depend> -->
  <depend>roscpp</depend>
  <depend>sensor_msgs</depend>
  <depend>rosbag</depend>
  <!-- <exec_depend>message_runtime</exec_depend> -->
</package>