对符号“XGetWindowAttributes”的未定义引用

Question

我正在使用 CMakeLists.txt 从 c++ 快速屏幕截图编译程序，以便与 opencv 一起使用。

cmake

运行良好，但使用

make

时出现此错误：

/usr/bin/ld: CMakeFiles/demoScreenShot.dir/main.cpp.o: undefined reference to symbol 'XGetWindowAttributes'
/usr/bin/ld: /lib/x86_64-linux-gnu/libX11.so.6: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status
make[2]: *** [CMakeFiles/demoScreenShot.dir/build.make:112: demoScreenShot] Error 1
make[1]: *** [CMakeFiles/Makefile2:83: CMakeFiles/demoScreenShot.dir/all] Error 2
make: *** [Makefile:91: all] Error 2

这是我的CMakeLists.txt

# Personal Project (Necesary)
cmake_minimum_required(VERSION 3.18.0)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED True)
set(CMAKE_EXPORT_COMPILE_COMMANDS ON)


project(demoScreenShot)
add_executable(${PROJECT_NAME} main.cpp)
# OpenCV
set(CMAKE_CXX_STANDARD 17)
find_package(OpenCV REQUIRED)
include_directories(${OpenCV_INCLUDE_DIRS})
target_link_libraries(${PROJECT_NAME} ${OpenCV_LIBS})

# X11 dependecies. It throws the same error using this block or not using it
include_directories( /usr/X11/include )  # It fails with this line or without it
link_directories( /usr/X11/lib ) # It fails with this line or without it
set (OPENGL_LIBRARIES GL GLU X11)  # It fails with this line or without it

我的main.cpp

#include <opencv4/opencv2/opencv.hpp>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <cstdint>
#include <cstring>
#include <vector>


void ImageFromDisplay(std::vector<uint8_t>& Pixels, int& Width, int& Height, int& BitsPerPixel)
{
    Display* display = XOpenDisplay(nullptr);
    Window root = DefaultRootWindow(display);

    XWindowAttributes* attributes = {0};
    XGetWindowAttributes(display, root, attributes);
    // XWindowAttributes attributes = {0};
    // XGetWindowAttributes(display, root, &attributes);

    // Width = attributes.width;
    // Height = attributes.height;
    Width = attributes -> width;
    Height = attributes -> height;

    XImage* img = XGetImage(display, root, 0, 0 , Width, Height, AllPlanes, ZPixmap);
    BitsPerPixel = img->bits_per_pixel;
    Pixels.resize(Width * Height * 4);

    memcpy(&Pixels[0], img->data, Pixels.size());

    XDestroyImage(img);
    XCloseDisplay(display);
}


int main()
{
    int Width = 0;
    int Height = 0;
    int Bpp = 0;
    std::vector<std::uint8_t> Pixels;

    ImageFromDisplay(Pixels, Width, Height, Bpp);

    if (Width && Height)
    {
        //Mat(Size(Height, Width), Bpp > 24 ? CV_8UC4 : CV_8UC3, &Pixels[0]); 
        cv::Mat img = cv::Mat(Height, Width, Bpp > 24 ? CV_8UC4 : CV_8UC3, &Pixels[0]);

        namedWindow("WindowTitle", cv::WINDOW_AUTOSIZE);
        imshow("Display window", img);

        cv::waitKey(0);
    }
    return 0;
}

正如你所看到的，我也尝试将变量属性设置为指针，但它不起作用！

我怎样才能成功编译这段代码？

Answer 1

这帮助我成功编译了程序。

cmake_minimum_required(VERSION 3.18.0)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED True)
set(CMAKE_EXPORT_COMPILE_COMMANDS ON)

project(demoScreenShot)
add_executable(${PROJECT_NAME} main.cpp)

# OpenCV
find_package(OpenCV REQUIRED)
include_directories(${OpenCV_INCLUDE_DIRS} /usr/include/X11)

set(X11)
link_directories( /usr/lib/X11 )
target_link_libraries(${PROJECT_NAME} ${OpenCV_LIBS} X11)