Generate and insert Face header from jpg file

[Satoshi Yoshida]

I use Gnus v5.13
I read https://www.gnus.org/manual/gnus_124.html#Face
and set in .gnus.el

(setq message-required-headers
      (nconc message-required-headers
             (list '(Face . (lambda ()
                              (gnus-face-from-file "~/face.jpg"))))))

But I couldn't generate and insert Face header at writing a mail.

I think there is no problem about ~/face.jpg (48x48 pixels, 13.2kB).
When I pasted Face header generated by shell script with face.jpg

http://quimby.gnus.org/circus/face/make-face
(I needed to rewrite "mimencode" to "mmencode" of FreeBSD package)

and send a mail myself, I could see Face image correctly.

Does anyone know the solutions?

-- 
Satoshi Yoshida