This is working for me

public function lazyimg($content) {
return preg_replace("/<img([^<]+)src=(['\"])([^\"']*)(['\"])([^<]*)>/i","<img$1ref='$3'$5>",$content);
}

to

public function lazyimg($content) {
return preg_replace("/<img([^<]+)src=(['\"])([^\"']*)(['\"])([^<]*)>/i","<img$1src='$3'$5>",$content);
}

in

helpers/ViewHelper.php