Face headers are essentially a funkier version of
X-Face ones. They describe a 48x48 pixel colored
image that's supposed to represent the author of the message.
The
contents of a Face header must be a base64 encoded
PNG image. See http://quimby.gnus.org/circus/face/
for the precise specifications.
The gnus-face-properties-alist variable affects
the appearance of displayed Face images. See X-Face.
Viewing an Face header requires an Emacs that is
able to display PNG images.
Gnus provides a few convenience functions and variables to allow easier insertion of Face headers in outgoing messages.
gnus-convert-png-to-face
takes a 48x48 PNG image, no longer than 726 bytes long, and
converts it to a face.
gnus-face-from-file
takes a JPEG file as the parameter, and then converts the file to
Face format by using the
gnus-convert-image-to-face-command shell
command.
Here's how you would typically use this function. Put something like the following in your ~/.gnus.el file:
(setq message-required-news-headers
(nconc message-required-news-headers
(list '(Face . (lambda ()
(gnus-face-from-file "~/face.jpg"))))))