Eclipse CDT undefined reference (package that was downloaded via MYSYS2) - c++

Question

So I basically only coded in Java at College, this time
I want to start my new Project in C++ and want to keep the Eclipse IDE that I have always used. I need the openCV and Tesseract packages (import). I have googled and researched for quite a time and I seem to be doing it right? but maybe some of you can tell me otherwise.
What I did:
Downloaded Eclipse CDT
Downloaded MYSYS2
Followed this instructions (MinGW Compiler)
Open MSYS2 shell from start menu
Run pacman -Sy pacman to update the package database
Re-open the shell, run pacman -Syu to update the package database and core system packages
Re-open the shell, run pacman -Su to update the rest
(Reference)
For 64 bits, run pacman -S mingw-w64-x86_64-toolchain
Select which package to install, default is all
You may also need make, run pacman -S make
Installed the libraries/tools that i need
OpenCV
pacman -S mingw64/mingw-w64-x86_64-opencv
Tesseract
pacman -S mingw64/mingw-w64-x86_64-tesseract-ocr
Included the MinGW to PATH (system environment variables)->restart computer
Started a new Eclipse Project-> C++ -> choose MinGW GCC as Toolchain
Basic Hello World -> Works fine
Basic OpenCV example -> doesnt work
It seems to Resolve the Inclusions correctly.
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
No Errors there.
FullCode:
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <iostream>
using namespace cv;
using namespace std;
int main( int argc, char** argv )
{
if( argc != 2)
{
cout <<" Usage: display_image ImageToLoadAndDisplay" << endl;
return -1;
}
Mat image;
image = imread(argv[1], CV_LOAD_IMAGE_COLOR); // Read the file
if(! image.data ) // Check for invalid input
{
cout << "Could not open or find the image" << std::endl ;
return -1;
}
namedWindow( "Display window", WINDOW_AUTOSIZE );// Create a window for display.
imshow( "Display window", image ); // Show our image inside it.
waitKey(0); // Wait for a keystroke in the window
return 0;
}
What Eclipse says:
16:54:43 **** Incremental Build of configuration Debug for project hello ****
Info: Internal Builder is used for build
g++ -O0 -g3 -Wall -c -fmessage-length=0 -o "src\\hello.o" "..\\src\\hello.cpp"
g++ -o hello.exe "src\\hello.o"
src\hello.o: In function `main':
C:\Users\Vaio\Desktop\EclipseProjekte\hello\Debug/../src/hello.cpp:17: undefined reference to `cv::imread(cv::String const&, int)'
C:\Users\Vaio\Desktop\EclipseProjekte\hello\Debug/../src/hello.cpp:25: undefined reference to `cv::namedWindow(cv::String const&, int)'
C:\Users\Vaio\Desktop\EclipseProjekte\hello\Debug/../src/hello.cpp:26: undefined reference to `cv::imshow(cv::String const&, cv::_InputArray const&)'
C:\Users\Vaio\Desktop\EclipseProjekte\hello\Debug/../src/hello.cpp:28: undefined reference to `cv::waitKey(int)'
src\hello.o: In function `cv::String::String(char const*)':
C:/msys64/mingw64/include/opencv2/core/cvstd.hpp:602: undefined reference to `cv::String::allocate(unsigned long long)'
src\hello.o: In function `cv::String::~String()':
C:/msys64/mingw64/include/opencv2/core/cvstd.hpp:648: undefined reference to `cv::String::deallocate()'
src\hello.o: In function `cv::Mat::~Mat()':
C:/msys64/mingw64/include/opencv2/core/mat.inl.hpp:692: undefined reference to `cv::fastFree(void*)'
src\hello.o: In function `cv::Mat::release()':
C:/msys64/mingw64/include/opencv2/core/mat.inl.hpp:804: undefined reference to `cv::Mat::deallocate()'
src\hello.o: In function `cv::Mat::operator=(cv::Mat&&)':
C:/msys64/mingw64/include/opencv2/core/mat.inl.hpp:1371: undefined reference to `cv::fastFree(void*)'
collect2.exe: error: ld returned 1 exit status
16:54:46 Build Finished (took 2s.908ms)
It can't find the librarys????
Whats the point of downloading it through MSYS2 if it doesnt connect the library like it does with iostream
Do I need to add all the library objects to the linker settings C/C++ Build -> Settings -> Tool Settings -> GCC C++ Linker -> Libraries

Answer 1

Okay so I guess that its obv but for those who have the same mistake, MSYS2 just added all opencv and tesseract files.
If you want to use them you need to specify it to the Linker.
filename: libopencv_core.dll.a
you need to exclude the lib at the beginning and the .dll and .a
linker: opencv_core
all libs can be found on the mingw path: (C:\msys64\mingw64\lib)
in the end you link it with -lopencv_core
or through the Eclipse GUI C/C++ Build -> Settings -> Tool Settings -> GCC C++ Linker -> Libraries -> add library -> opencv_core