Libguestfs is ...

#include <guestfs.h>
                    /* link with -lguestfs */
main () {
  guestfs_h *g = guestfs_create ();
  guestfs_add_drive_ro (g,
          "fedora-19.img");
  guestfs_launch (g);
  guestfs_mount (g,
          "/dev/fedora/root");
  guestfs_download (g,
          "/etc/fedora-release",
          "/dev/stdout");
  guestfs_close (g);
}