0.前言

因為opencv涉及匯入本地圖片(cv::imread函式),又不想一直使用絕對路徑,使用相對路徑有一直出錯,所以想先看看當前作業目錄在哪.

此外,這里還使用roslaunch啟動程式,使當前作業目錄更難找了.

感謝tjf,ym兩位師兄的幫助.

1.作業空間架構

mkdir -p opencv_ws/src
cd opencv_ws/src
catkin_create_pkg current_directory std_msgs roscpp rospy cv_bridge
cd current_directory/src
gedit current_directory_node.cpp

在打開的current_directory_node.cpp檔案中添加下述代碼,下面cv::imread""中的為本地圖片絕對路徑,你也可以添加自己電腦上的圖片的絕對路徑:

#include <iostream>
#include <opencv2/core.hpp>
#include "opencv2/imgproc.hpp"
#include "opencv2/imgcodecs.hpp"
#include "opencv2/highgui.hpp"
#include "stdlib.h"
#include "unistd.h"

using namespace cv;

#define MAX_PATH 255

int main( int argc, char ** argv )
{   
    //一個正常的讀取本地圖片程式
    Mat src;
    char window_name[] = "current directory Demo";
    namedWindow( window_name, WINDOW_NORMAL );
    src = cv::imread("/home/meng/my_learning/opencv/opencv_ws1/src/smothing_images/src/summer_tea.jpg",1);    
    imshow( window_name, src );
    imwrite("2021_08010.jpg",src);//保存到當前作業目錄,可用于查看程式運行結果

    //獲取當前作業目錄
    char * wd;
    char buffer[MAX_PATH];
    wd=getcwd(buffer,MAX_PATH);
    printf(wd);

    return 0;
}

后退一步到current_directory檔案夾下,修改CMakeLists.txt檔案如下:

cmake_minimum_required(VERSION 3.0.2)
project(current_directory)

find_package(catkin REQUIRED COMPONENTS
  cv_bridge
  roscpp
  rospy
  std_msgs
)
find_package(OpenCV REQUIRED)
catkin_package()

include_directories(
  ${catkin_INCLUDE_DIRS} ${OpenCV_INCLUDE_DIRS}	)
add_executable(current_directory_node src/current_directory_node.cpp)
target_link_libraries(current_directory_node
  ${catkin_LIBRARIES} ${OpenCV_LIBS}	)

回到opencv_ws檔案夾下,創建ws.launch檔案內容如下:

<launch>
    <node pkg="current_directory" type="current_directory_node" name="current_directory1" output="screen" />
</launch>

終端輸入命令tree(sudo apt-get install tree 可安裝),得檔案架構如下:

# meng @ meng in ~/my_learning/opencv_ws [0:31:45] 
$ tree                     
.
└── src
    └── current_directory
        ├── CMakeLists.txt
        ├── include
        │   └── current_directory
        ├── package.xml
        └── src
            └── current_directory_node.cpp

5 directories, 3 files

2.編譯運行程式的當前作業目錄

終端到opencv_ws目錄下,沒有裝zsh則source devel/setup.bash.

catkin_make
source devel/setup.zsh
roslaunch ws.launch

結果如下所示,這里顯示當前作業目錄為:/home/meng/.ros

# meng @ meng in ~/my_learning/opencv_ws [0:40:43] 
$ roslaunch ws.launch
... logging to /home/meng/.ros/log/8ac42fb0-f930-11eb-9795-f8a2d6c541e3/roslaunch-meng-3807.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

started roslaunch server http://meng:40201/

SUMMARY
========

PARAMETERS
 * /rosdistro: kinetic
 * /rosversion: 1.12.17

NODES
  /
    current_directory1 (current_directory/current_directory_node)

auto-starting new master
process[master]: started with pid [3817]
ROS_MASTER_URI=http://localhost:11311

setting /run_id to 8ac42fb0-f930-11eb-9795-f8a2d6c541e3
process[rosout-1]: started with pid [3830]
started core service [/rosout]
process[current_directory1-2]: started with pid [3834]
/home/meng/.ros[current_directory1-2] process has finished cleanly
log file: /home/meng/.ros/log/8ac42fb0-f930-11eb-9795-f8a2d6c541e3/current_directory1-2*.log

去/home/meng/.ros看看,果真有2021_08010.jpg檔案,如下(倒數第四個)