nginx image resizer with size parameters in query string

nginx.conf

# Example: test.com/images/cats.jpeg?w=100&h=100

location ~* ^/images/(.+\.(?:jpe?g|png|gif))$ {
  set $image_name $1;
  set $demins "${arg_w}x${arg_h}";
  set $check_str "${demins}";

  # check that original size file exists
  if ( -f $request_filename ) {
    set $check_str "${check_str}F1";
  }

  # check that width and height contain only digits and that string has file-exist flag 
  if ( $check_str ~ ^([0-9]+)x([0-9]+)F1$ ) {
    rewrite "^/images/.+$" "/image_resize_server/${demins}/${image_name}";
  }
}

location ~* ^/image_resize_server/([0-9]+)x([0-9]+)/(.+)$ {
  internal;
  set $width  $1;
  set $height $2;
  set $image_path $3;
  set $demins "${width}x${height}";
  set $image_resized 0;

  alias /tmp/nginx/resize/$demins/$image_path;

  set $image_uri image_resize_process/$image_path?width=$width&height=$height;
  if (!-f $request_filename) {
    set $image_resized 1;
    proxy_pass http://127.0.0.1:80/$image_uri;
    break;
  }

  add_header X-debug-message "Resized: ${image_resized}";

  proxy_store          /tmp/nginx/resize/$demins/$image_path;
  proxy_store_access   user:rw  group:rw  all:r;
  proxy_temp_path      /tmp/images;
  proxy_set_header     Host $host;
}

location /image_resize_process {
  # place dir with original size images here
  alias /var/www/site/public/images;

  image_filter resize $arg_width $arg_height;
  image_filter_jpeg_quality 75;
  image_filter_buffer 10M;
  allow 127.0.0.0/8;
  deny all;
}