Mingw-64 will not compile openCV code after building and installing - c++

Question

I built and installed openCV using Cmake and mingw32-make. Afterwards I copied the produced "opencv2" source folder to the "include" folder of my installed mingw-64 compiler. I then copied the produced files from "lib" and "bin" to the corresponding folders of my installed compiler. I finally tried to compiler the following example code to ensure proper installation:
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
using namespace cv;
int main()
{
Mat image;// new blank image
image = cv::imread("test.png", 0);// read the file
namedWindow( "Display window", CV_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;
}
I tried to compile the code with the following command line command:
g++ -o helloWorld helloWorld.cpp
Which produced the following error:
helloWorld.cpp: In function 'int main()':
helloWorld.cpp:10:36: error: 'CV_WINDOW_AUTOSIZE' was not declared in this scope
namedWindow( "Display window", CV_WINDOW_AUTOSIZE );// create a window for display.
I suspect I did not properly install openCV, but when I search tutorials online for solving this issue it only is with respect to using codeblocks with mingw. I only wish to use mingw, not codeblocks.
Are there linker options that I am missing? Did I put the ".dll"s and ".dll.a"s in the wrong location?
Thanks

Answer 1

OpenCV was indeed installed correctly, the problem was that CV_WINDOW_AUTOSIZE is a constant used by the C implementation of openCV. When swapped with WINDOW_AUTOSIZE, the code then notified me that I did not link the proper libraries. For openCV 4.2.0, I needed to append "420" to the end of the needed libraries (for example: "-lopencv_core420").
The command line arguments to compile after these changes were made is:
g++ -o helloWorld helloWorld.cpp -lopencv_core420 -lopencv_highgui420 -lopencv_imgcodecs420