I recently had to use dlib for a class assignment. While there is a package for dlib on most Linux distributions, there is no MacPorts package for dlib. So the only way I could think of globally installing it was copying the headers:

  1. Download dlib from their site.
  2. Extract the archive.
  3. Copy [archive root]/dlib to /usr/include.

The Makefile for whatever you were trying to compile should be happy now.