Please take me advise or help =)

i'm newbe in work with nginx
and first problem change htaccess rules for Nginx

would you help me please rewrite this htaccess rules for Nginx

<FilesMatch "\.(gif|jpg|png)$">
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} -f
RewriteRule ^(.*)$ /watermark/watermark.php [T=application/x-httpd-php,L,QSA]
</FilesMatch>