problem compiling an example

edit

I'm trying to compile this example

https://github.com/opencv/opencv_cont...

I changed the top three lines

#include  "opencv2/text.hpp"
#include  "opencv2/highgui.hpp"
#include  "opencv2/imgproc.hpp"

to

#include  "/home/david/c/opencv-3.2.0/include/opencv2/opencv.hpp"

I get the following compilation error

david@ubuntu:~/c$ gcc opencv.cpp 
In file included from opencv.cpp:1:0:
/home/david/c/opencv-3.2.0/include/opencv2/opencv.hpp:48:38: fatal error: opencv2/opencv_modules.hpp: No such file or directory
compilation terminated.

I've been away from c++ for years, what am I doing wrong?