Adds support for UPC 5-Digit Supplemental barcodes to Barby barcode generator

upc_supplemental_for_barby.rb

require 'barby/barcode'

class UpcSupplementalForBarby < Barby::Barcode1D
  @data = nil
  attr_reader :data

  START = '1011'
  STOP = ''
  INTER_CHAR = '01'

  PARITY_MAPS = {
      0 => [:even, :even, :odd, :odd, :odd],
      1 => [:even, :odd, :even, :odd, :odd],
      2 => [:even, :odd, :odd, :even, :odd],
      3 => [:even, :odd, :odd, :odd, :even],
      4 => [:odd, :even, :even, :odd, :odd],
      5 => [:odd, :odd, :even, :even, :odd],
      6 => [:odd, :odd, :odd, :even, :even],
      7 => [:odd, :even, :odd, :even, :odd],
      8 => [:odd, :even, :odd, :odd, :even],
      9 => [:odd, :odd, :even, :odd, :even]
    }

   ENCODINGS_ODD = {
      0 => '0001101', 1 => '0011001', 2 => '0010011',
      3 => '0111101', 4 => '0100011', 5 => '0110001',
      6 => '0101111', 7 => '0111011', 8 => '0110111',
      9 => '0001011'
    }

    ENCODINGS_EVEN = {
      0 => '0100111', 1 => '0110011', 2 => '0011011',
      3 => '0100001', 4 => '0011101', 5 => '0111001',
      6 => '0000101', 7 => '0010001', 8 => '0001001',
      9 => '0010111'
    }



  def data= data
    @data = data
  end

  def initialize data
    self.data = data
  end

  def encoding
    begin
      data = @data
      return nil if data.length!=5
      sum_odd = data[0].chr.to_i + data[2].chr.to_i + data[4].chr.to_i
      sum_even = data[1].chr.to_i + data[3].chr.to_i
      total = sum_odd * 3 + sum_even * 9
      check_digit = total.modulo(10)
     
      parity_map = PARITY_MAPS[check_digit]

      pos = 0
      e = START
      data_chars = data.split('')
      for digit_char in data_chars
        digit = digit_char.to_i
        parity = parity_map[pos]
        e +=  ENCODINGS_ODD[digit] if parity==:odd
        e +=  ENCODINGS_EVEN[digit] if parity==:even
        e += INTER_CHAR unless pos == 4
        pos += 1
      end


      return e
    
    rescue
    end
  end

  def two_dimensional?
    return false
  end

  def valid?
    return true
  end

  def to_s
    data[0,20]
  end

end

The Barby Ruby gem lets you quickly and easily generate barcode images from simple text data. It allows for simple extension to the barcodes it supports.

This quick project adds support for UPC 5-Digit Supplemental barcodes, the barcodes that you typically see on the back of books alongside the ISBN UPC (Bookland) code, encoding the recommended price. Although the barcode uses some features of EAN-13/UPC encoding, there did not seem to be an available encoder that worked to produce it. In fact, details of the encoding were hard to find. So we ended up resorting to the not entirely definitive, but extremely helpful Barcode Island site at: http://www.barcodeisland.com/upcext.phtml

For more information, see the Labs project at: http://consected.com/labs-barby-upc-5