Introduce a filter that short-circuits the avatar URL generation.

includes/class-simple-local-avatars.php

@@ -353,6 +353,27 @@ public function get_simple_local_avatar_url( $id_or_email, $size ) {
 			}
 		}
 
+		/**
+		 * Filter the URL of an avatar for the given user and size.
+		 *
+		 * This filters is applied before Simple Local Avatars validates the value of the
+		 * `$local_avatars` array which comes from the user meta field. This allows the URL
+		 * to be short-circuited, for example by a dynamic image resizing service.
+		 *
+		 * @param string|null $url           The URL of the avatar. If null, the URL will be
+		 *                                   generated by Simple Local Avatars.
+		 * @param int         $user_id       The user ID.
+		 * @param int         $size          Requested avatar size.
+		 * @param array       $local_avatars The local avatars for the user.
+		 * @return string|null The URL of the avatar, or null to allow Simple Local Avatars to
+		 *                     generate the URL.
+		 */
+		$url = apply_filters( 'pre_simple_local_avatar_url', null, $user_id, $size, $local_avatars );
+
+		if ( is_string( $url ) ) {
+			return $url;
+		}
+
 		// handle "real" media
 		if ( ! empty( $local_avatars['media_id'] ) ) {
 			// If using shared avatars, make sure we validate the URL on the main site.