main.cpp:(.text+0x51): undefined reference to `cv::imread(std::__cxx11::basic_string, std::allocator > const&, int)'

This error occurs because the OpenCV library is not properly linked in your C++ program. To resolve this issue, follow these steps:

  1. Include the OpenCV header file in your C++ program:cpp #include <opencv2/opencv.hpp>

  2. Link the OpenCV library during compilation: Add the following compilation flags when compiling your program. g++ -o your_program_name your_program.cpp `pkg-config --cflags --libs opencv`

  3. Make sure your OpenCV installation is correct: Ensure that OpenCV is installed on your system. You can check the installation path and version using the following command: pkg-config --modversion opencv

  4. Use the appropriate namespace in your code: Add the following line after your includes to use the OpenCV namespace: cpp using namespace cv;

  5. Verify the image file path: Double-check that the file path you're passing to the imread function is correct.

Here's an example combining all the steps:

#include <opencv2/opencv.hpp>

using namespace cv;

int main() {
    // Verify the image file path is correct
    std::string imagePath = "path/to/your/image.jpg";

    // Read the image using imread
    Mat image = imread(imagePath, IMREAD_COLOR);

    if (image.empty()) {
        // Handle error if the image cannot be loaded
        return -1;

    // Your further processing goes here

    return 0;

Remember to replace "path/to/your/image.jpg" with the actual path to your image file. Additionally, make sure to adjust the compilation command according to your build system.