I have many, many WordPress authors. For each, I have used the custom wp_usermeta profile field "photo_url" to store URLs for different remotely-hosted avatar images.
I am currently displaying these image avatars on author.php by echoing the strings through the img HTML tag. But I'd like to more closely integrate them with WordPress, by making them available through get_avatar, as though they were standard avatars.
I have looked at several threads here, including on disabling Gravatar. That's good, but how do I then make sure the URLs can be accessed through all standard WordPress avatar hooks in places I want to - ie. on author profiles, posts and loops?
(I also want to default to
get_template_directory_uri() . '/images/avatar_default.png' whenever the "photo_url" has no value.