RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f 
RewriteCond %{REQUEST_URI} ^/thumb/([a-z]+)/([0-9]+)/([0-9]+)/([0-9]+) [NC]
RewriteRule ^(.*)$ /preview.php?id=%2%3%4&size=%1 [L,QSA]
