Class: Barcode1DTools::EAN8

Inherits:
Barcode1D show all
Defined in:
lib/barcode1dtools/ean8.rb

Overview

The value encoded is a 7-digit number, and a checksum digit will be added. You can add the option # :checksum_included => true when initializing to specify that you have already included a checksum.

num = ‘96385074’ bc = Barcode1DTools::EAN8.new(num) pattern = bc.bars rle_pattern = bc.rle width = bc.width check_digit = Barcode1DTools::EAN83.generate_check_digit_for(num)

The object created is immutable.

There are two formats for the returned pattern (wn format is not available):

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.  Each character
       in the string renders to a single unit width.

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.

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

Unlike some of the other barcodes, e.g. Code 3 of 9, there is no “wnstr” for EAN & UPC style barcodes because the bars and spaces are variable width from 1 to 4 units.

A EAN-8 barcode has 3 elements:

  1. A 2 or 3 digit “number system” designation

  2. A 4 or 5 digit manufacturer’s code

  3. A single digit checksum

Note than an EAN-8 is not analogous to a UPC-E. In particular, there is no way to create an EAN-13 from and EAN-8 and vice versa. The numbers are assigned within each system by a central authority.

The bar patterns are the same as EAN-13, with nothing encoded in the parity. All bars on the left use the “odd” parity set.

RENDERING

When rendered, two sets of four digits are shown at the bottom of the code, aligned with the bottom of the code, and with the middle guard pattern bars extending down between them. A supplemental 2 or 5 may be used.

Constant Summary collapse

LEFT_PATTERNS =

patterns to create the bar codes:

EAN13::LEFT_PATTERNS
LEFT_PATTERNS_RLE = 
EAN13::LEFT_PATTERNS_RLE
RIGHT_PATTERNS = 
EAN13::RIGHT_PATTERNS
RIGHT_PATTERNS_RLE = 
EAN13::RIGHT_PATTERNS_RLE
SIDE_GUARD_PATTERN = 
EAN13::SIDE_GUARD_PATTERN
MIDDLE_GUARD_PATTERN = 
EAN13::MIDDLE_GUARD_PATTERN
SIDE_GUARD_PATTERN_RLE = 
EAN13::SIDE_GUARD_PATTERN_RLE
MIDDLE_GUARD_PATTERN_RLE = 
EAN13::MIDDLE_GUARD_PATTERN_RLE
DEFAULT_OPTIONS = 
{
  :line_character => '1',
  :space_character => '0'
}

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 = {}) ⇒ EAN8

Options are :line_character, :space_character, and :checksum_included.

Raises:



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# File 'lib/barcode1dtools/ean8.rb', line 197

def initialize(value, options = {})

  @options = DEFAULT_OPTIONS.merge(options)

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

  if @options[:checksum_included]
    @encoded_string = sprintf('%08d', value.to_i)
    raise ChecksumError unless self.class.validate_check_digit_for(@encoded_string)
    md = @encoded_string.match(/^(\d+?)(\d)$/)
    @value, @check_digit = md[1], md[2].to_i
  else
    # need to add a checksum
    @value = sprintf('%07d', value.to_i)
    @check_digit = self.class.generate_check_digit_for(@value)
    @encoded_string = "#{@value}#{@check_digit}"
  end

  md = @value.match(/^(\d{3})(\d{4})/)
  @number_system, @product_code = md[1], md[2]
end

Instance Attribute Details

#number_system ⇒ Object (readonly)

Specific for EAN



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# File 'lib/barcode1dtools/ean8.rb', line 86

def number_system
  @number_system
end

#product_code ⇒ Object (readonly)

Returns the value of attribute product_code.



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# File 'lib/barcode1dtools/ean8.rb', line 87

def product_code
  @product_code
end

Class Method Details

.can_encode?(value, options = nil) ⇒ Boolean

returns true or false - must be 7-8 digits

Returns:

  • (Boolean) 


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# File 'lib/barcode1dtools/ean8.rb', line 91

def can_encode?(value, options = nil)
  if !options
    value.to_s =~ /^\d{7,8}$/
  elsif (options[:checksum_included])
    value.to_s =~ /^\d{8}$/
  else
    value.to_s =~ /^\d{7}$/
  end
end

.decode(str) ⇒ Object

Decode a string representing an rle or bar pattern EAN-13. Note that the string might be backward or forward. This will return an EAN8 object.



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# File 'lib/barcode1dtools/ean8.rb', line 121

def decode(str)
  if str.length == 67
    # bar pattern
    str = bars_to_rle(str)
  elsif str.length == 43
    # rle
  else
    raise UnencodableCharactersError, "Pattern must be 67 unit bar pattern or 43 character rle."
  end

  # Check the guard patterns
  unless str[0..2] == SIDE_GUARD_PATTERN_RLE && str[40..42] == SIDE_GUARD_PATTERN_RLE && str[19..23] == MIDDLE_GUARD_PATTERN_RLE
    raise UnencodableCharactersError, "Missing or incorrect guard patterns"
  end

  # Now I have an rle pattern, simply need to decode
  # according to the LEFT_PATTERNS_RLE, keeping track
  # of the parity for each position.

  # Set up the decoder
  left_parity_sequence = ''
  left_digits = ''
  right_parity_sequence = ''
  right_digits = ''
  left_initial_offset = SIDE_GUARD_PATTERN_RLE.length
  right_initial_offset = SIDE_GUARD_PATTERN_RLE.length + (4*4) + MIDDLE_GUARD_PATTERN_RLE.length

  # Decode the left side
  (0..3).each do |left_offset|
    found = false
    digit_rle = str[(left_initial_offset + left_offset*4),4]
    ['o','e'].each do |parity|
      ('0'..'9').each do |digit|
        if LEFT_PATTERNS_RLE[digit][parity] == digit_rle
          left_parity_sequence += parity
          left_digits += digit
          found = true
          break
        end
      end
    end
    raise UndecodableCharactersError, "Invalid sequence: #{digit_rle}" unless found
  end

  # Decode the right side
  (0..3).each do |right_offset|
    found = false
    digit_rle = str[(right_initial_offset + right_offset*4),4]
    ['o','e'].each do |parity|
      ('0'..'9').each do |digit|
        if LEFT_PATTERNS_RLE[digit][parity] == digit_rle
          right_parity_sequence += parity
          right_digits += digit
          found = true
          break
        end
      end
    end
    raise UndecodableCharactersError, "Invalid sequence: #{digit_rle}" unless found
  end

  # If left parity sequence is 'eeee', the string is reversed
  if left_parity_sequence == 'eeee'
    left_digits, right_digits, left_parity_sequence = right_digits.reverse, left_digits.reverse, right_parity_sequence.reverse.tr('eo','oe')
  end

  # Debugging
  #puts "Left digits: #{left_digits} Left parity: #{left_parity_sequence}"
  #puts "Right digits: #{right_digits} Right parity: #{right_parity_sequence}"

  EAN8.new(left_digits + right_digits, :checksum_included => true)
end

.generate_check_digit_for(value) ⇒ Object

Generates check digit given a string to encode. It assumes there is no check digit on the “value”.

Raises:



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# File 'lib/barcode1dtools/ean8.rb', line 103

def generate_check_digit_for(value)
  raise UnencodableCharactersError unless self.can_encode?(value, :checksum_included => false)
  mult = 1
  value = value.split('').inject(0) { |a,c| mult = 4 - mult ; a + c.to_i * mult }
  (10 - (value % 10)) % 10
end

.validate_check_digit_for(value) ⇒ Object

validates the check digit given a string - assumes check digit is last digit of string.

Raises:



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# File 'lib/barcode1dtools/ean8.rb', line 112

def validate_check_digit_for(value)
  raise UnencodableCharactersError unless self.can_encode?(value, :checksum_included => true)
  md = value.match(/^(\d{7})(\d)$/)
  self.generate_check_digit_for(md[1]) == md[2].to_i
end

Instance Method Details

#bars ⇒ Object

returns 1s and 0s (for “black” and “white”)



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# File 'lib/barcode1dtools/ean8.rb', line 236

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/ean8.rb', line 226

def rle
  if @rle
    @rle
  else
    md = @encoded_string.match(/^(\d{4})(\d{4})/)
    @rle = gen_rle(md[1], md[2])
  end
end

#width ⇒ Object

returns the total unit width of the bar code



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# File 'lib/barcode1dtools/ean8.rb', line 241

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

#wn ⇒ Object

not usable with EAN codes

Raises:



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# File 'lib/barcode1dtools/ean8.rb', line 221

def wn
  raise NotImplementedError
end