dlib is a C++ library by David E. King that contains (amongst other things) image processing and machine learning tools, under the Boost Public License. This package makes it accessible within R, in the same way that the BH package makes the boost header files accessible
devtools::install_github("ironholds/dlib")
//Example: including dlib arrays and making them available.
#include <Rcpp.h>
using namespace Rcpp;
//[[Rcpp::depends(dlib)]]
#include <dlib/array.h>