Apache rewrite in Nginx format

[Philip Murray]

Hi,

Is it possible to express the following Apache rewrite rule in Nginx?

     RewriteCond %{QUERY_STRING} !^nobranding$
     RewriteCond %{REQUEST_FILENAME} ^/assets/XL/([^.]+)\.([jpegif]+)$
     RewriteCond /usr/local/www/assets-nz/XL/%1.branded.%2 -f
     RewriteRule ^/([^.]+)\.([jpeg]+)$ /$1.branded.$2

In Nginx, this would be in a location block with an alias, so

location /assets {
     alias /usr/local/www/assets-nz/;

     ... rewrites go here ...
}

But, I understand you can't rewrite with an alias present? So how can  
I implement the above Apache rewrite?

Cheers

Phil Murray