libptouch: Linux printer driver library for P-Touch label printers
(C) 2009 Philip Pemberton <philpem@philpem.me.uk>.



Table of Contents
=================
  1. What is libptouch?
  2. Supported printers
  3. Building and Installing libptouch
  T. TODO, aka Things That Don't Work Yet.
  R. References


1. What is libptouch?
=====================
libptouch is a library that allows a user-mode application to print labels
using a Brother P-touch series label printer. The goal of the libptouch
project is to create a driver that will allow any Linux application to
print to a P-touch printer, using a common raster image as a source.

Brother only release official Linux drivers for a small number of P-touch
printers, and these all rely on the CUPS printing system to function (not to
mention the fact that the print filter is completely closed-source). On top
of the added complexity of having to feed data through CUPS or LPR, the print
quality was actually pretty poor -- the fonts were covered in jagged edges,
and printed barcodes looked like they'd been fed through a blender (needless
to say my PSC 5281 scanner wouldn't read them).

As a result of this, I started working on a library that could take a number
of Libgd images, and feed them to the P-touch in sequence. On top of that, I
wanted to be able to set printing parameters (that is, turn the auto-cutter
and mirroring options on and off) without having to butcher command lines
and drop to a shell. Finally, I wanted to be able to run my applications as a
(relatively) unprivileged user -- the printing apps should not need to be
'setuid root'.

So I set to work finding out all I could about the P-touch protocol. It turns
out that the standard mode for my PT-2450DX printer was the so-called "PT-CBP"
mode, and that documentation for this printing protocol had been released for
another printer in the P-touch series, the PT-9500PC[1]. Using the protocol
details in the PT-9500PC documentation, and after many long nights of coding,
lots of cups of tea and much wasted label tape, I created a library that would
eventually be released as libptouch.


2. Supported printers
=====================

NOTE: If you don't see your printer on this list, ask me about adding it.

+--------------+--------------------------------------------------------------+
|   Printer    | Features                                                     |
|    Model     +----+----+----------------------------------------------------+
|    Number    | S  | AC | HC | PHW | DPI | MTH  | MPH  |                     |
+--------------+----+----+----+-----+-----+------+------+---------------------+
| PT-2450DX    | Y  | Y  |    | 128 | 180 | 24mm | 18mm |                     |
+--------------+----+----+----+-----+-----+-----------------------------------+

S   = Supported/Tested
        Y = Fully working
        P = Partially working
        ? = Not tested
AC  = Auto Cutter
HC  = Half Cut
MI  = Mirror
PHW = Printhead width (pixels)
DPI = Dots per inch
MTH = Max label tape height (mm)
MPH = Max printing height (mm)

"Y" = Yes
" " = No


3. Building and Installing libptouch
====================================
To build libptouch, you will need:
  GNU gcc    version 3.1 or later  (libptouch is tested with gcc 4.3.3)
  GNU make   version 3.80 or later (libptouch is tested with make 3.81)
  libgd      version 2.0 or later  (libptouch is tested with libgd 2.0.36)

To build the documentation, you will also need:
  doxygen    version 1.5 or later  (libptouch is tested with doxygen 1.5.8)

Briefly, this means any common Linux distribution (Debian or RedHat based)
released in 2006 or later should successfully build libptouch. As for other
Unices, or older versions of Linux.... you're on your own.

On Ubuntu or Debian, the following command will install all the packages
necessary to build libptouch:
  $ sudo apt-get install build-essential libgd2-xpm-dev

Once you have installed the necessary tools and libraries, you can compile
libptouch by using the following command:
  $ tar -zxf libptouch-$VERSION.tgz
  $ cd libptouch-$VERSION
  $ make

This will build the libptouch library and documentation from the source code.

To install libptouch into /usr/local, type:
  $ make install

To install libptouch into another directory, say /opt/libptouch, type:
  $ make install PREFIX=/opt/libptouch


4. Using libptouch
==================
[... TODO ...]


5. Using libptouch-based Applications Without Superuser Privileges
==================================================================
To use a libptouch-based application without superuser (root) privileges, you
must do one of two things:

  1. Set the application's group ID to the user that normally owns printers
     (or serial ports) on your system, then chmod the application to "g+S"
     (turn the Set Group ID bit on). This will only work if all your printers
     use the same interface type, e.g. all serial or all USB.

  2. Add the user who will be running the application to the 'lp' or 'dialout'
     group (for USB or serial printers respectively). Note that a user can be
     a member of more than one group -- see your system documentation for more
     information.


T. TODO, aka Things That Don't Work Yet.
========================================
  * Printers with printheads that don't have 128 dots will not work. This
    basically means you can't use any printer whose maximum label tape width
    is less than 24mm.

  * I'd like to implement graphics inversion. Basically, where there is white,
    the printer will print black. This could be useful for printing
    white-on-black labels when you're out of white-on-black tape, or vice versa
    :)

  * There is no support for serial port printers. At all.

  * The PT-PC is not, and will likely never be supported, as it uses a
    different printing protocol and can only print bit image graphics on the
    central 3.5mm (!) of the label tape.

  * The QL-series label printers aren't supported either. I'd love to add
    support for them, but I don't have a QL-series printer to play with. The
    same applies to the rest of the P-touch (PT-series) printers that aren't
    listed as "Supported" in the list above.

  * Data compression. The later PT-series printers support "Packbits"
    compression of each print line. At the moment, this isn't implemented.
    Instead, a "COPY N BYTES" compression control byte is sent, followed by
    a line of print data. Rinse, repeat.

  * No option to set the feed amount. I'm not even 100% sure if this works
    on most PT-series printers, but it might be worth implementing. See
    <http://www.undocprint.org/formats/page_description_languages/brother_p-touch>.


R. References
=============
1. Brother Industries, Ltd. "PT-9500PC Command Reference, CBP-RASTER Mode
  (PTCBP Mode) Volume" August 29, 2003, version 1.0.
  Available online: http://etc.nkadesign.com/Printers/QL550LabelPrinter