Image resizer in NGINX

nginx.conf

worker_processes  1;

#error_log  logs/error.log;
#error_log  logs/error.log  notice;
#error_log  logs/error.log  info;
#pid        logs/nginx.pid;

events {
  worker_connections  1024;
}

http {
  #include       mime.types;
  #default_type  application/octet-stream;

  #log_format imageresize '$host $arg_width x $arg_height $arg_url';
  #access_log /opt/boxen/homebrew/var/log/nginx/resize.log imageresize;

  resolver        8.8.8.8;
  resolver_timeout 30s;

  sendfile        on;

  keepalive_timeout  65;

  map $arg_width $width {
    default 80;
    ~^[0-9]+$ $arg_width;
  }

  map $arg_height $height {
    default 80;
    ~^[0-9]+$ $arg_height;
  }

  server {
    listen      80;
    server_name localhost;
    root /Users/johnnyt/p/mediaforge/ads_japan;

    location @missing_image {
      try_files /empty.png $uri;
      image_filter resize $width $height;
      add_header Resize-Status fail;
    }

    location /resize {
      expires off;
      set $url $arg_url;
      set_unescape_uri $url;
      proxy_pass $url;
      image_filter resize $width $height;
      add_header Resize-Status success;
      error_page 404 415 = @missing_image;
    }

    location / {
      root /Users/johnnyt/p/mediaforge/ads_japan;
    }
  }
}