function rw_get_post_thumb_url($post, $width = 160, $height = 100)
{
    $img = ratingwidget()->GetPostImage($post, WP_RW__CACHE_TIMEOUT_POST_THUMB_EXTRACT);
    return rw_get_img_thumb_url(false !== $img ? $img : get_permalink($post->ID), $width, $height);
}
function rw_get_thumb_url($img, $width = 160, $height = 100, $permalink = '')
{
    return rw_get_img_thumb_url(is_string($img) && 0 < count($img) ? $img : $permalink, $width, $height);
}