lvi_sam中ubuntu18与ubuntu20代码修改的部分

其实主要是opencv部分的区别，主要是opencv3与opencv4的区别。

1.opencv报错没有opencv2，是因为在usr/include中只有opencv4文件夹，需要把opencv4文件夹中的opencv2复制到usr/include中，或者建立一个软链接。

2.opencv/cv.h: No such file or directory

//#include <opencv/cv.h>
#include <opencv2/opencv.hpp>

3.编译包含Opencv和flann的头文件时，会报错

    /usr/include/flann/util/serialization.h:34:14: error: ‘class std::unordered_map<unsigned int, std::vector<unsigned int> >’ has no member named ‘serialize’
       34 |         type.serialize(ar);
          |         ~~~~~^~~~~~~~~
     

原因是依赖关系：pcl/kdtree/kdtree_flann.h 可能依赖于某些 OpenCV 的类型或功能。如果 opencv2/opencv.hpp 在 pcl/kdtree/kdtree_flann.h 之前被包含，OpenCV 的相关定义可能尚未被处理，导致编译器无法正确识别或解析 pcl/kdtree/kdtree_flann.h 中使用的 OpenCV 类型或功能。

所以需要将opencv头文件放在pcl头文件之后，主要是utility.h

#pragma once
#ifndef _UTILITY_LIDAR_ODOMETRY_H_
#define _UTILITY_LIDAR_ODOMETRY_H_
#define PCL_NO_PRECOMPILE 
 
#include <ros/ros.h>
 
#include <std_msgs/Header.h>
#include <std_msgs/Float64MultiArray.h>
#include <sensor_msgs/Imu.h>
#include <sensor_msgs/PointCloud2.h>
#include <sensor_msgs/NavSatFix.h>
#include <nav_msgs/Odometry.h>
#include <nav_msgs/Path.h>
#include <visualization_msgs/Marker.h>
#include <visualization_msgs/MarkerArray.h>
 
#include <pcl/point_cloud.h>
#include <pcl/point_types.h>
#include <pcl/search/impl/search.hpp>
#include <pcl/range_image/range_image.h>
#include <pcl/kdtree/kdtree_flann.h>
#include <pcl/common/common.h>
#include <pcl/common/transforms.h>
#include <pcl/registration/icp.h>
#include <pcl/io/pcd_io.h>
#include <pcl/filters/filter.h>
#include <pcl/filters/voxel_grid.h>
#include <pcl/filters/crop_box.h> 
#include <pcl_conversions/pcl_conversions.h>
 
#include <tf/LinearMath/Quaternion.h>
#include <tf/transform_listener.h>
#include <tf/transform_datatypes.h>
#include <tf/transform_broadcaster.h>
 
#include <opencv2/opencv.hpp>
 
#include <vector>
#include <cmath>
#include <algorithm>
#include <queue>
#include <deque>
#include <iostream>
#include <fstream>
#include <ctime>
#include <cfloat>
#include <iterator>
#include <sstream>
#include <string>
#include <limits>
#include <iomanip>
#include <array>
#include <thread>
#include <mutex>

4.需要修改cmakelists中的C++版本

#set(CMAKE_CXX_FLAGS "-std=c++11")
set(CMAKE_CXX_STANDARD 14)

5.error: ‘CV_RGB2GRAY’ was not declared in this scope 的解决方法

在头文件里添加
#include <opencv2/imgproc/types_c.h>

 6.‘CV_FONT_HERSHEY_SIMPLEX’ was not declared in this scope

//CV_FONT_HERSHEY_SIMPLEX
//注意是小写
cv::FONT_HERSHEY_SIMPLEX

5.