Getting OpenCV headers to work correctly on install in Linux

Question

I have an OpenCV installation on Ubuntu Linux. From any example the headers are:

#include <opencv2/imgcodecs.hpp>
#include <opencv2/highgui.hpp>

When I compile with these includes I get the error:

fatal error: opencv2/imgcodecs.hpp: No such file or directory

#include <opencv2/imgcodecs.hpp>
#include <opencv2/highgui.hpp>

I can find out where OpenCV is located with

pkg-config --cflags --libs opencv

which outputs as follow:

 "Package opencv was not found"

When I try pkg-config --cflags --libs opencv2

I get:

"Package opencv2 was not found"

Only when I use pkg-config --cflags --libs opencv4 do I get the path:

-I/usr/local/include/opencv4/opencv2 

so I thought that by changing the includes to:

#include <opencv4/imgcodecs.hpp>
#include <opencv4/highgui.hpp>

it would work. But I get:

fatal error: opencv4/imgcodecs.hpp: No such file or directory

#include <opencv4/imgcodecs.hpp>

so when I try the full path:

#include <opencv4/opencv2/imgcodecs.hpp>

I get:

imgcodecs.hpp:46:10: fatal error: opencv2/core.hpp: No such file or directory

#include "opencv2/core.hpp"

and of course in the hpp file in question it is:

#include "opencv2/core.hpp"

Is there a simple way to fix all this?

Answer 1

I actually ran into this issue recently. The issue is that when you build OpenCV it places the header files in /usr/local/include/opencv4/ then underneath that you will see opencv2/opencv.hpp and all the other files you're referencing. To fix your issue you will need to run in bash:

sudo ln -s /usr/local/include/opencv4/opencv2 /usr/local/include/opencv2

This resolved the issue for me, if it works for you please be sure to mark this as the answer.