Ruby Semacode Encoder

Introduction

This Ruby extension implements a DataMatrix encoder for Ruby. It is typically used to create semacodes, which are barcodes, that contain URLs. This encoder does not create image files or visual representations of the semacode. This is because it can be used for more than creating images, such as rendering semacodes to HTML, SVG, PDF or even stored in a database or file for later use.

See test.rb for an example of how to create a visual symbol for a semacode, it presents a semacode in HTML and plain text formats, and this can give you an idea of how to start.

Once you have a visual representation of the semacode, you can use a reader, such as those from semacode.org on your camera phone, to capture the URL embedded in the semacode and proceed directly to that web site.

License

This software is released under the terms of the GNU Public License version 2, available from <www.gnu.org>

Contact Information

You can contact me via <guido@sohne.net> if you have patches, bug fixes or improvements.

Copyright (C) 2007, Guido Sohne
Website: http://sohne.net/projects/semafox

Credits

Based on the iec16022ecc200.c encoder by Adrian Kennard, Andrews & Arnold Ltd

Quick Start

Configure the extension to your local system and ruby

<tt>ruby extconf.rb</tt>

Build the extension

<tt>make</tt>

Test that it works

<tt>ruby test.rb</tt>

Install the extension (you may need to become root)

<tt>make install</tt>

You should take a look at tests/test.rb to understand how to use this. It includes some code to generate a semacode using HTML and CSS, so that could end up being useful.

USAGE

Here’s some basic ways in which you can make use of this extension. It tries to show by example, how the semacodes can be created and what can be done with or to a semacode object.

Include this library

<tt>require 'rubygems'</tt>
<tt>require 'semacode'</tt>

Create a semacode

<tt>semacode = Barcode::Semacode.new "http://sohne.net/projects/semafox/"</tt>

Return the semacode as an array of arrays of boolean

The first element of the array is the top row, the last element is the 
bottom row. the array length is the semacode height, and each element is 
an array as wide as the semacode width

<tt>grid = semacode.data</tt> or
<tt>grid = semacode.to_a</tt> or

Return the encoding list used to create the semacode

This encoding list is composed of the 'character set', complete with
shifts from one encoding type to another, that is used for the DataMatrix
algorithm.

<tt>encoding = semacode.encoding</tt>

Return the semacode as a string

The string is a comma separated list of character vectors. Each vector is a row
in the semacode symbol, the top row is first, and the bottom row is last. Inside
each row, the vector reads from left to right.

<tt>semacode.to_s</tt> or
<tt>semacode.to_str</tt>

Encode another string

<tt>semacode.encode "http://sohne.net"</tt>

Get the width of the semacode

<tt>semacode.width</tt>

Get the height of the semacode

<tt>semacode.height</tt>

How long is the semacode? (width * height)

<tt>semacode.length</tt> or
<tt>semacode.size</tt>

Get the raw encoded length (before padding and before ECC)

<tt>semacode.raw_encoded_length</tt>

Get the symbol size

The max number of characters this semacode type 
(specific width x height) can hold is called the
symbol size.

<tt>semacode.symbol_size</tt>

Count the ECC bytes

How many bytes were used for error correction?

<tt>semacode.ecc_bytes</tt>

NOTES

The C code can throw runtime exceptions. Be sure to include a catch block if you want to use this in production. Mostly the exceptions are not recoverable, except for when the data is too long, in which case you can shorten it and try again.

There are two type of exceptions that it will throw. The first is a RangeError exception, which happens when the input is too long or when it just can’t find a fit for the data. The second is a ArgumentError (ArgError?) exception that gets thrown when the input contains data it cannot handle.