Various updates

README

@@ -10,17 +10,47 @@ the printer can natively print PDF. That is to say, CUPS needs to already be
 configured with a PDF filter. Debian based distributions ship CUPS pre-configured
 this way.
 
+This script can also discover networked printers via DNS-SD, independent of CUPS,
+and produce exact .service files for them, allowing the printers to be announced
+on different subnets by copying the .service files to /etc/avahi/services/ there.
+This solves the problem of AirPrint printers not being availabe outside the
+local subnet even though routing/NAT exists between subnets.
+
 DNSSD has a limit of 255 Chars for a given txt-record, because of this the list
 of accepted pdl's will be truncated to fit. If you're curious to see which ones
 are trimmed out of the list run with the script with the verbose flag (--verbose)
 
 If python-lxml is installed, .service files will be generated in a human
 readble format, I wasn't able to get minidom's version to work acceptably.
 
+The git repository also contains airprint.convs, airprint.types and apple.types.  These need 
+to be copied to the /usr/share/cups/mime folder.
+
+Copy the .service files generated by this script to /etc/avahi/services.
+
+Then restart both avahi and cups with 
+sudo service avahi-daemon restart
+sudo service cups restart
+
+**Python Requirements:**
+This script requires depends on the python-cups library, and optionally python-lxml to make pretty xml files. 
+
+Debian/Ubuntu:
+sudo apt-get install python-cups python-lxml 
+
+CentOS:
+sudo yum install system-config-printer-libs
+
+
 Usage: airprint-generate.py [options]
 
 Options:
   -h, --help            show this help message and exit
+  -s, --dnssd           Search for network printers using DNS-SD (requires
+                        avahi)
+  -D DNSDOMAIN, --dnsdomain=DNSDOMAIN
+                        DNS domain where printers are located.
+  -c, --cups            Search CUPS for shared printers (requires CUPS)
   -H HOSTNAME, --host=HOSTNAME
                         Hostname of CUPS server (optional)
   -P PORT, --port=PORT  Port number of CUPS server
@@ -29,4 +59,5 @@ Options:
                         Directory to create service files
   -v, --verbose         Print debugging information to STDERR
   -p PREFIX, --prefix=PREFIX
-                        Prefix all files with this string
+                        Prefix all files with this string
+  -a, --admin           Include the printer specified uri as the adminurl