Code with Opencv4 compiles but not links- not finding Mat and imshow - c++

Question

I am trying to create executable of following code taken from here:
#include <iostream>
#include <opencv2/opencv.hpp>
#include <opencv2/imgcodecs.hpp>
using namespace cv;
using namespace std;
// Driver code
int main(int argc, char** argv)
{
// Read the image file as // imread("default.jpg");
Mat image = imread("barchart.png", IMREAD_GRAYSCALE);
// Error Handling
if (image.empty()) {
cout << "Image File Not Found" << endl;
// wait for any key press
cin.get();
return -1;
}
// Show Image inside a window with the name provided
imshow("Window Name", image);
// Wait for any keystroke
waitKey(0);
return 0;
}
It compiles all right with command g++ showimage.cpp -c -I /usr/include/opencv4 and creates an showimage.o file
However, following command to link it gives error:
g++ showimage.o -l:libopencv_imgcodecs.a
...
... (lot of output)
/usr/bin/ld: showimage.o: in function `main':
showimage.cpp:(.text+0x83): undefined reference to `cv::Mat::empty() const'
/usr/bin/ld: showimage.cpp:(.text+0x10e): undefined reference to `cv::imshow(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, cv::_InputArray const&)'
/usr/bin/ld: showimage.cpp:(.text+0x13c): undefined reference to `cv::waitKey(int)'
/usr/bin/ld: showimage.cpp:(.text+0x150): undefined reference to `cv::Mat::~Mat()'
/usr/bin/ld: showimage.cpp:(.text+0x1c2): undefined reference to `cv::Mat::~Mat()'
collect2: error: ld returned 1 exit status
I also tried following option:
g++ showimage.o -L /usr/lib/x86_64-linux-gnu
g++ showimage.o -L libopencv
g++ showimage.o -L opencv
But none is not working.
Where is the problem and how can it be solved?