OpenCV 未定义对 `cv::imread(cv::String const&, int)' 的引用答案

【问题标题】：OpenCV undefined reference to `cv::imread(cv::String const&, int)'OpenCV 未定义对 `cv::imread(cv::String const&, int)' 的引用
【发布时间】：2020-09-17 18:17:31
【问题描述】：

我无法让 opencv 在 C++ 代码中工作。我已经阅读了所有类似的问题，但还没有编译我的代码。

我从源代码安装了 OpenCV，并包含了 -D OPENCV_GENERATE_PKGCONFIG=ON 选项，我正在尝试让一个简单的 OpenCV 示例正常工作。

代码如下：

    #include <opencv2/core.hpp>
    #include <opencv2/imgcodecs.hpp>
    #include <opencv2/highgui.hpp>
    #include <iostream>
    using namespace cv;
    int main()
    {
        std::string image_path = "/data/000001.jpg";
        Mat img = imread(image_path, IMREAD_COLOR);
        if(img.empty())
        {
            std::cout << "Could not read the image: " << image_path << std::endl;
            return 1;
        }
        imshow("Display window", img);
        int k = waitKey(0); // Wait for a keystroke in the window
        if(k == 's')
        {
            imwrite("starry_night.png", img);
        }
        return 0;
    }

尝试编译：$/usr/bin/g++ -g pkg-config --cflags --libs opencv main.cpp 导致所有 OpenCV 调用出现“未定义的引用”错误： /code/cpp/play/main.cpp:9: 未定义引用 `cv::imread(cv::String const&, int)'

运行 pkg-config --cflags --libs opencv 返回：

pkg-config --cflags --libs opencv -I/usr/local/include/opencv -I/usr/local/include -L/usr/local/lib -lopencv_stitching -vlopencv_superres -lopencv_videostab -lopencv_aruco -lopencv_bgsegm -lopencv_bioinspired -lopencv_ccalib -lopencv_dnn_objdetect -lopencv_dpm -lopencv_face -lopencv_photo -lopencv_freetype -lopencv_fuzzy -lopencv_hdf -lopencv_hfs -lopencv_img_hash -lopencv_line_descriptor -lopencv_optflow -lopencv_reg -lopencv_rgbd -lopencv_saliency -lopencv_stereo -lopencv_structured_light -lopencv_viz -lopencv_phase_unwrapping -lopencv_surface_matching -lopencv_tracking -lopencv_datasets -lopencv_text -lopencv_dnn -lopencv_plot -lopencv_xfeatures2d -lopencv_shape -lopencv_video -lopencv_ml -lopencv_ximgproc -lopencv_xobjdetect -lopencv_objdetect -lopencv_calib3d -lopencv_features2d -lopencv_highgui -lopencv_videoio -lopencv_imgcodecs -lopencv_flann -lopencv_xphoto -lopencv_imgproc -lopencv_core

我还尝试使用此文件通过 cmake 构建代码：

    set(CMAKE_VERBOSE_MAKEFILE ON)
    cmake_minimum_required(VERSION 3.16)
    project(play)
    set(CMAKE_CXX_STANDARD 14)
    find_package(OpenCV REQUIRED)
    message(STATUS "OpenCV_INCLUDE_DIRS = ${OpenCV_INCLUDE_DIRS}")
    message(STATUS "OpenCV_LIBS = ${OpenCV_LIBS}")
    add_executable(play main.cpp)

这就是 OpenCV_LIB 的样子吗？应该有路吗？

-- OpenCV_INCLUDE_DIRS = /usr/include;/usr/include/opencv
-- OpenCV_LIBS = opencv_calib3d;opencv_core;opencv_features2d;opencv_flann;opencv_highgui;opencv_imgcodecs;opencv_imgproc;opencv_ml;opencv_objdetect;opencv_photo;opencv_shape;opencv_stitching;opencv_superres;opencv_video;opencv_videoio;opencv_videostab;opencv_viz;opencv_aruco;opencv_bgsegm;opencv_bioinspired;opencv_ccalib;opencv_datasets;opencv_dpm;opencv_face;opencv_freetype;opencv_fuzzy;opencv_hdf;opencv_line_descriptor;opencv_optflow;opencv_phase_unwrapping;opencv_plot;opencv_reg;opencv_rgbd;opencv_saliency;opencv_stereo;opencv_structured_light;opencv_surface_matching;opencv_text;opencv_ximgproc;opencv_xobjdetect;opencv_xphoto
-- Configuring done

感谢您的帮助。

【问题讨论】：

你试过g++ `pkg-config --cflags opencv` -g main.cpp `pkg-config --libs opencv`吗？我认为链接顺序很重要。
你确定opencv安装正确吗？你能检查一下这个命令输出pkg-config --modversion opencv。您的编译命令似乎没问题

标签： c++ opencv

【解决方案1】：

感谢您的建议。约翰是对的。这解决了它：

g++ -g main.cpp `pkg-config --libs opencv`

pkg-config 需要在源文件之后。

【讨论】：