<?php

$html = '<img src="http://s...content-available-to-author-only...k.com/img.jpg"> http://s...content-available-to-author-only...k.com';
$link = preg_replace('%<img src="(.*)/(.*?)">\s*(.*?)\s*$%m', '<img src="$1/$2"> <a href="$1" target="_blank">$3</a>', $html );
echo $link;

