How do you display the avatar for the current post author ?

<?php
// Ensure user is logged in
if( is_user_logged_in() ) {
 // Display current logged in user's avatar (includes  tag)
 echo get_avatar( get_current_user_id(), 96 );
 // Display current logged in user's avatar URL
 echo get_avatar_url( get_current_user_id(), array( 'size' => 96 ) );
}