Class: Barcode1DTools::Codabar

Inherits:
Barcode1D show all
Defined in:
lib/barcode1dtools/codabar.rb

Overview

Barcode1DTools::Codabar - Create and decode bar patterns for Codabar. The value encoded is a string which may contain the digits 0-9 and the symbols dash “-”, dollar sign “$”, plus sign “+”, colon “:”, forward slash “/”, and dot “.”. There are four start/stop characters which are A, B, C, and D or T, N, asterisk “*”, and E. Note that A and T are equivalent, as are B and N, C and asterisk, and D and E. Any may be used as start and stop characters giving 16 possible combinations.

Because there is no standard for check digits, we implement neither generation nor checking of one. It is up to the caller to present a check digit if it is part of the payload.

Additionally, the caller must present the start and stop characters as part of the value. When decoding, the start/stop characters will be presented as A, B, C, or D.

Example

val = "A29322930C"
bc = Barcode1DTools::Codabar.new(val)
pattern = bc.bars
rle_pattern = bc.rle
width = bc.width

The object created is immutable.

Barcode1DTools::Codabar creates the patterns that you need to display Codabar barcodes. It can also decode a simple w/n string.

Codabar characters consist of 4 bars and 3 spaces, with a narrow space between them. The main characters (0-9, dash, and dollar sign) each have one wide bar and one wide space (hence the alternate name “code 2 of 7”). The start/stop codes have one wide bar and two adjacent wide spaces. The extended characters (dot, forward slash, colon, and plus sign) each have three wide bars and all narrow spaces.

Formats

There are three formats for the returned pattern:

bars - 1s and 0s specifying black lines and white spaces. Actual characters can be changed from “1” and 0“ with options :line_character and :space_character.

rle - Run-length-encoded version of the pattern. The first number is always a black line, with subsequent digits alternating between spaces and lines. The digits specify the width of each line or space.

wn - The native format for this barcode type. The string consists of a series of “w” and “n” characters. The first item is always a black line, with subsequent characters alternating between spaces and lines. A “wide” item is twice the width of a “narrow” item.

The “width” method will tell you the total end-to-end width, in units, of the entire barcode.

Rendering

The original Codabar specification actually included a varied w/n ratio depending on whether there were two or three wide elements in a character. Those with two wide elements used a 3:1 ratio while those with three wide elements used a 2:1 ratio. In that way, the characters were consistently 10 units wide.

Our default ratio is 3:1 for the entire code, but if you include :varied_wn_ratio => true in the options the rle and bars strings will have variable ratio that shifts between 2:1 and 3:1 and the “wn_ratio” option will be ignored.

Constant Summary collapse

CHAR_SEQUENCE =

Character sequence - 0-based offset in this string is character number

"0123456789-$:/.+ABCD"
PATTERNS =

Patterns for making bar codes

{
  '0'=> {'val'=>0 ,'wn'=>'nnnnnww'},
  '1'=> {'val'=>1 ,'wn'=>'nnnnwwn'},
  '2'=> {'val'=>2 ,'wn'=>'nnnwnnw'},
  '3'=> {'val'=>3 ,'wn'=>'wwnnnnn'},
  '4'=> {'val'=>4 ,'wn'=>'nnwnnwn'},
  '5'=> {'val'=>5 ,'wn'=>'wnnnnwn'},
  '6'=> {'val'=>6 ,'wn'=>'nwnnnnw'},
  '7'=> {'val'=>7 ,'wn'=>'nwnnwnn'},
  '8'=> {'val'=>8 ,'wn'=>'nwwnnnn'},
  '9'=> {'val'=>9 ,'wn'=>'wnnwnnn'},
  '-'=> {'val'=>10 ,'wn'=>'nnnwwnn'},
  '$'=> {'val'=>11 ,'wn'=>'nnwwnnn'},
  ':'=> {'val'=>12 ,'wn'=>'wnnnwnw'},
  '/'=> {'val'=>13 ,'wn'=>'wnwnnnw'},
  '.'=> {'val'=>14 ,'wn'=>'wnwnwnn'},
  '+'=> {'val'=>15 ,'wn'=>'nnwnwnw'},

  'A'=> {'val'=>16 ,'wn'=>'nnwwnwn'},
  'B'=> {'val'=>17 ,'wn'=>'nwnwnnw'},
  'C'=> {'val'=>18 ,'wn'=>'nnnwnww'},
  'D'=> {'val'=>19 ,'wn'=>'nnnwwwn'},

  'T'=> {'val'=>16 ,'wn'=>'nnwwnwn'},
  'N'=> {'val'=>17 ,'wn'=>'nwnwnnw'},
  '*'=> {'val'=>18 ,'wn'=>'nnnwnww'},
  'E'=> {'val'=>19 ,'wn'=>'nnnwwwn'}
}
DEFAULT_OPTIONS = 
{
  :line_character => '1',
  :space_character => '0',
  :w_character => 'w',
  :n_character => 'n',
  :wn_ratio => '3',
  :varied_wn_ratio => false
}

Instance Attribute Summary collapse

Attributes inherited from Barcode1D

#check_digit, #encoded_string, #options, #value

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Barcode1D

bar_pair, bars_to_rle, rle_to_bars, rle_to_wn, wn_pair, wn_to_rle

Constructor Details

#initialize(value, options = {}) ⇒ Codabar

Create a new Codabar object. Options are :line_character, :space_character, :w_character, :n_character, and :varied_wn_ratio.

Raises:



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# File 'lib/barcode1dtools/codabar.rb', line 212

def initialize(value, options = {})

  @options = DEFAULT_OPTIONS.merge(options)

  # Can we encode this value?
  raise UnencodableCharactersError unless self.class.can_encode?(value)

  @value = value.to_s
  @check_digit = nil

  @encoded_string = @value
  md = @value.match(/\A([ABCDTNE\*])(.*?)([ABCDTNE\*])\z/)
  @start_character, @payload, @stop_character = md[1], md[2], md[3]
end

Instance Attribute Details

#payload ⇒ Object (readonly)

The actual payload (between start/stop characters)



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# File 'lib/barcode1dtools/codabar.rb', line 132

def payload
  @payload
end

#start_character ⇒ Object (readonly)

Holds the start character



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# File 'lib/barcode1dtools/codabar.rb', line 128

def start_character
  @start_character
end

#stop_character ⇒ Object (readonly)

Holds the stop character



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# File 'lib/barcode1dtools/codabar.rb', line 130

def stop_character
  @stop_character
end

Class Method Details

.can_encode?(value) ⇒ Boolean

Returns true if the value presented can be encoded in a Codabar barcode. Codabar can encode digits, dash, dollar, colon, forward slash, dot, and plus. The string must start and stop with start/stop characters.

Returns:

  • (Boolean) 


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# File 'lib/barcode1dtools/codabar.rb', line 140

def can_encode?(value)
  value.to_s =~ /\A[ABCD][0-9\$:\/\.\+\-]*[ABCD]\z/ || value.to_s =~ /\A[TN\*E][0-9\$:\/\.\+\-]*[TN\*E]\z/
end

.decode(str, options = {}) ⇒ Object

Decode a string in rle format. This will return a Codabar object.



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# File 'lib/barcode1dtools/codabar.rb', line 158

def decode(str, options = {})
  if str =~ /[^1-3]/ && str =~ /[^wn]/
    raise UnencodableCharactersError, "Pattern must be rle or wn"
  end

  # ensure a wn string
  if str =~ /[1-3]/
    str = str.tr('123','nww')
  end

  start_stop_pattern_match = Regexp.new(['A','B','C','D'].collect { |c| PATTERNS[c]['wn'] }.join('|'))

  if str.reverse =~ /\A#{start_stop_pattern_match}n.*?#{start_stop_pattern_match}\z/
    str.reverse!
  end

  unless str =~ /\A(#{start_stop_pattern_match}n.*?#{start_stop_pattern_match})\z/
    raise UnencodableCharactersError, "Start/stop pattern is not detected."
  end

  # Adding an "n" to make it easier to scan
  wn_pattern = $1 + 'n'

  # Each pattern is 4 bars and 3 spaces, with a space between.
  unless wn_pattern.size % 8 == 0
    raise UnencodableCharactersError, "Wrong number of bars."
  end

  decoded_string = ''

  wn_pattern.scan(/(.{7})n/).each do |chunk|

    chunk = chunk.first
    found = false

    PATTERNS.each do |char,hsh|
      if !['T', 'E', '*', 'N'].include?(char) && chunk == hsh['wn']
        decoded_string += char
        found = true
        break;
      end
    end

    raise UndecodableCharactersError, "Invalid sequence: #{chunk}" unless found

  end

  Codabar.new(decoded_string)
end

.generate_check_digit_for(value) ⇒ Object

Generate a check digit. For Codabar, this will raise a NotImplementedError.

Raises:



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# File 'lib/barcode1dtools/codabar.rb', line 146

def generate_check_digit_for(value)
  raise NotImplementedError
end

.validate_check_digit_for(value) ⇒ Object

Validate the check digit. For Codabar, this will raise a NotImplementedError.

Raises:



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# File 'lib/barcode1dtools/codabar.rb', line 152

def validate_check_digit_for(value)
  raise NotImplementedError
end

Instance Method Details

#bars ⇒ Object

Returns the bar pattern



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# File 'lib/barcode1dtools/codabar.rb', line 242

def bars
  @bars ||= self.class.rle_to_bars(self.rle, @options)
end

#rle ⇒ Object

Returns a run-length-encoded string representation



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# File 'lib/barcode1dtools/codabar.rb', line 233

def rle
  if @options[:varied_wn_ratio]
    @rle ||= @encoded_string.split('').collect { |c| PATTERNS[c]['wn'] }.collect { |p| p.tr('wn',(p=~/.*w.*w.*w/ ? '21' : '31')) }.join('1')
  else
    @rle ||= self.class.wn_to_rle(self.wn, @options)
  end
end

#width ⇒ Object

Returns the total unit width of the bar code



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# File 'lib/barcode1dtools/codabar.rb', line 247

def width
  @width ||= rle.split('').inject(0) { |a,c| a + c.to_i }
end

#wn ⇒ Object

Returns a string of “w” or “n” (“wide” and “narrow”)



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# File 'lib/barcode1dtools/codabar.rb', line 228

def wn
  @wn ||= wn_str.tr('wn', @options[:w_character].to_s + @options[:n_character].to_s)
end