WordPress at a glance
filter is not described

pre_get_avatar_data filter-hook . WP 4.2.0

Filters whether to retrieve the avatar URL early.

Passing a non-null value in the 'url' member of the return array will effectively short circuit get_avatar_data(), passing the value through the 'get_avatar_data' filter and returning early.

Usage

add_filter( 'pre_get_avatar_data', 'filter_function_name_4789', 10, 2 );
function filter_function_name_4789( $args, $id_or_email ){
	// filter...

	return $args;
}
$args(array)
Arguments passed to get_avatar_data(), after processing.
$id_or_email(mixed)
The Gravatar to retrieve. Accepts a user_id, gravatar md5 hash, user email, WP_User object, WP_Post object, or WP_Comment object.

Where the hook is called

get_avatar_data()
wp-includes/link-template.php 3873
$args = apply_filters( 'pre_get_avatar_data', $args, $id_or_email );

Where the hook is used (in WP core)

Does not used.