How to determine OpenCV version

Question

How to determine which version of OpenCV I have installed?

I am most interested in knowing a way of doing it programatically (and cross-platform), but I can

Answer 1

I would like to enhance one of the answers using version.hpp defines.

Please notice the potential problem with that solution:

v. 2.4.13.6 defines:

#define CV_VERSION_EPOCH 2
#define CV_VERSION_MAJOR 4
#define CV_VERSION_MINOR 13
#define CV_VERSION_REVISION 6
#if CV_VERSION_REVISION
#  define CV_VERSION    CVAUX_STR(CV_VERSION_EPOCH) "." CVAUX_STR(CV_VERSION_MAJOR) "." CVAUX_STR(CV_VERSION_MINOR) "." CVAUX_STR(CV_VERSION_REVISION)
#else
#  define CV_VERSION        CVAUX_STR(CV_VERSION_EPOCH) "." CVAUX_STR(CV_VERSION_MAJOR) "." CVAUX_STR(CV_VERSION_MINOR)
#endif

and v. 3.4.2 defines:

#define CV_VERSION_MAJOR 3
#define CV_VERSION_MINOR 4
#define CV_VERSION_REVISION 2
#define CV_VERSION    CVAUX_STR(CV_VERSION_MAJOR) "." CVAUX_STR(CV_VERSION_MINOR) "." CVAUX_STR(CV_VERSION_REVISION) CV_VERSION_STATUS

As a result, CV_VERSION_MAJOR are not comparable. Much safer solution is to parse CV_VERSION and use the first value before a dot.