Class: Barcode1DTools::UPC_E

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

Overview

Barcode1DTools::UPC_E - Create pattern for UPC-E barcodes. The value encoded is an 6-digit integer, 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.

Example

num = '394932'
bc = Barcode1DTools::UPC_E.new(num)
pattern = bc.bars
rle_pattern = bc.rle
width = bc.width
check_digit = Barcode1DTools::UPC_E.generate_check_digit_for(num)

Other Information

A UPC-E barcode is an abbreviated form of UPC-A, but can encode only a few codes. The checksum is derived from the full UPC-A digit sequence rather than the 6 digits of the UPC-E. The checksum is encoded as the parity, with the bar patterns the same as the left side of a standard UPC-A.

The last digit of the UPC-E determines the pattern used to convert to a UPC-A.

UPC-E      UPC-A equivalent
2 digits for manufacturer code (plus last digit), 3 digits for product
XXNNN0     0XX000-00NNN
XXNNN1     0XX100-00NNN
XXNNN2     0XX200-00NNN
3 digits for manufacturer code, 2 digits for product
XXXNN3     0XXX00-000NN
4 digits for manufacturer code, 1 digit for product
XXXXN4     0XXXX0-0000N
5 digits for manufacturer code, 1 digit for product (5-9)
XXXXX5     0XXXXX-00005
XXXXX6     0XXXXX-00006
XXXXX7     0XXXXX-00007
XXXXX8     0XXXXX-00008
XXXXX9     0XXXXX-00009

Formats

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.

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 “w/n” format for EAN & UPC style barcodes because the bars and spaces are variable width from 1 to 4 units.

Rendering

The UPC-E is made for smaller items. Generally, they are rendered with the number system digit (0) on the left of the bars and the checksum on the right. The 6-digit payload is shown below the bars with the end guard bars extending half-way down the digits. The number system and check digit might be rendered in a slightly smaller font size. The UPC-E uses the same bar patterns as the left half of a regular UPC-A, but there is no middle pattern and the right guard pattern has an extra line/space pair.

Constant Summary collapse

LEFT_PATTERNS =

Using the left patterns from UPC-A

UPC_A::LEFT_PATTERNS
LEFT_PATTERNS_RLE =

Using the left patterns from UPC-A

UPC_A::LEFT_PATTERNS_RLE
PARITY_PATTERNS =

UPC-E uses a different set of parity patterns to encode the check digit.

{
  '0' => 'eeeooo',
  '1' => 'eeoeoo',
  '2' => 'eeooeo',
  '3' => 'eeoooe',
  '4' => 'eoeeoo',
  '5' => 'eooeeo',
  '6' => 'eoooee',
  '7' => 'eoeoeo',
  '8' => 'eoeooe',
  '9' => 'eooeoe',
}
LEFT_GUARD_PATTERN =

Left guard pattern

'101'
RIGHT_GUARD_PATTERN =

Right guard pattern

'010101'
LEFT_GUARD_PATTERN_RLE =

Left guard pattern as RLE

'111'
RIGHT_GUARD_PATTERN_RLE =

Right guard pattern as RLE

'111111'
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

bars_to_rle, rle_to_bars, rle_to_wn, wn_to_rle

Constructor Details

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

Create a new UPC-E object for a given value. Options are :line_character, :space_character, and :checksum_included.

Raises:



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# File 'lib/barcode1dtools/upc_e.rb', line 254

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 = value.to_s
    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 = value.to_s
    @check_digit = self.class.generate_check_digit_for(@value)
    @encoded_string = "#{@value}#{@check_digit}"
  end

  @upca_value = self.class.upce_value_to_upca_value(@value)
  md = @upca_value.match(/^(\d)(\d{5})(\d{5})/)
  @number_system, @manufacturers_code, @product_code = md[1], md[2], md[3]
end

Instance Attribute Details

#manufacturers_code ⇒ Object (readonly)

For UPC-E - the manufacturer’s code part of the item number



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

def manufacturers_code
  @manufacturers_code
end

#number_system ⇒ Object (readonly)

For UPC-E - the number system part of the item number



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# File 'lib/barcode1dtools/upc_e.rb', line 119

def number_system
  @number_system
end

#product_code ⇒ Object (readonly)

For UPC-E - the product code part of the item number



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# File 'lib/barcode1dtools/upc_e.rb', line 123

def product_code
  @product_code
end

#upca_value ⇒ Object (readonly)

For UPC-E - the UPC-A value for this UPC-E value



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# File 'lib/barcode1dtools/upc_e.rb', line 125

def upca_value
  @upca_value
end

Class Method Details

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

Returns true or false - must be 6-8 digits. This also handles the case where the leading 0 is added.

Returns:

  • (Boolean) 


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

def can_encode?(value, options = nil)
  if !options
    value.to_s =~ /^0?[0-9]{6,7}$/
  elsif (options[:checksum_included])
    value.to_s =~ /^0?[0-9]{7}$/
  else
    value.to_s =~ /^0?[0-9]{6}$/
  end
end

.decode(str) ⇒ Object

Decodes a bar pattern or rle string that represents a UPC-E. Returns a UPC_E object.

Raises:



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# File 'lib/barcode1dtools/upc_e.rb', line 156

def decode(str)
  if str.length == 51
    # bar pattern
    str = bars_to_rle(str)
  elsif str.length == 33 && str =~ /^[1-9]+$/
    # rle
  else
    raise UnencodableCharactersError, "Pattern must be 51 unit bar pattern or 33 character rle."
  end

  # See if the string is reversed
  if str[0..5] == RIGHT_GUARD_PATTERN_RLE && str[30..32] == LEFT_GUARD_PATTERN_RLE
    str.reverse!
  end

  # Check the guard patterns
  unless (str[0..2] == LEFT_GUARD_PATTERN_RLE && str[27..32] == RIGHT_GUARD_PATTERN_RLE)
    raise UnencodableCharactersError, "Missing or incorrect guard patterns"
  end

  parity_sequence = ''
  digits = ''
  initial_offset = LEFT_GUARD_PATTERN_RLE.length

  # Decode
  (0..5).each do |offset|
    found = false
    digit_rle = str[(initial_offset + offset*4),4]
    ['o','e'].each do |parity|
      ('0'..'9').each do |digit|
        if LEFT_PATTERNS_RLE[digit][parity] == digit_rle
          parity_sequence += parity
          digits += digit
          found = true
          break
        end
      end
    end
    raise UndecodableCharactersError, "Invalid sequence: #{digit_rle}" unless found
  end

  # Now, find the parity digit
  parity_digit = nil
  ('0'..'9').each do |x|
    if PARITY_PATTERNS[x] == parity_sequence
      parity_digit = x
      break
    end
  end

  raise UndecodableCharactersError, "Weird parity: #{parity_sequence}" unless parity_digit

  UPC_E.new('0' + digits + parity_digit, :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”.



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# File 'lib/barcode1dtools/upc_e.rb', line 142

def generate_check_digit_for(value)
  UPC_A.generate_check_digit_for(self.upce_value_to_upca_value(value))
end

.upca_value_to_upce_value(value, options = {}) ⇒ Object

Converts the given UPC-A value to a UPC-E value.

Raises:



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# File 'lib/barcode1dtools/upc_e.rb', line 232

def upca_value_to_upce_value(value, options = {})
  raise UnencodableCharactersError unless UPC_A.can_encode?(value, options)
  value = value % 10 if options[:checksum_included]
  value = sprintf('%011d', value.to_i)
  if value =~ /^0(\d\d\d\d[1-9])0000([5-9])/
    upce_value = "0#{$1}#{$2}"
  elsif value =~ /^0(\d\d\d[1-9])00000(\d)/
    upce_value = "0#{$1}#{$2}4"
  elsif value =~ /^0(\d\d)([012])0000(\d\d\d)/
    upce_value = "0#{$1}#{$3}#{$2}"
  elsif value =~ /^0(\d\d[3-9])00000(\d\d)/
    upce_value = "0#{$1}#{$2}3"
  else
    raise UnencodableCharactersError, "Cannot change UPC-A #{value} to UPC-E"
  end
  upce_value
end

.upce_value_to_upca_value(value, options = {}) ⇒ Object

Converts the given UPC-E value to a UPC-A value.

Raises:



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

def upce_value_to_upca_value(value, options = {})
  raise UnencodableCharactersError unless self.can_encode?(value, options)
  # remove the check digit if it was included
  value = value.to_i % 10 if options[:checksum_included]
  value = sprintf('%06d', value.to_i)
  if value =~ /(\d\d)(\d\d\d)([012])/
    upca_value = "0#{$1}#{$3}0000#{$2}"
  elsif value =~ /(\d\d\d)(\d\d)(3)/
    upca_value = "0#{$1}00000#{$2}"
  elsif value =~ /(\d\d\d\d)(\d)(4)/
    upca_value = "0#{$1}00000#{$2}"
  elsif value =~ /(\d\d\d\d\d)([5-9])/
    upca_value = "0#{$1}0000#{$2}"
  else
    raise UnencodableCharactersError, "Cannot change UPC-E #{value} to UPC-A"
  end
  upca_value
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/upc_e.rb', line 148

def validate_check_digit_for(value)
  raise UnencodableCharactersError unless self.can_encode?(value, :checksum_included => true)
  md = value.match(/^(0?\d{6})(\d)$/)
  self.generate_check_digit_for(md[1]) == md[2].to_i
end

Instance Method Details

#bars ⇒ Object

Returns a bar pattern.



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# File 'lib/barcode1dtools/upc_e.rb', line 294

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/upc_e.rb', line 284

def rle
  if @rle
    @rle
  else
    md = @encoded_string.match(/(\d{6})(\d)$/)
    @rle = gen_rle(md[1], md[2])
  end
end

#to_upc_a ⇒ Object

Returns a UPC_A object with the same value.



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# File 'lib/barcode1dtools/upc_e.rb', line 304

def to_upc_a
  UPC_A.new(self.class.upce_value_to_upca_value(@value), options.merge(:checksum_included => false))
end

#width ⇒ Object

Returns the total unit width of the bar code.



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# File 'lib/barcode1dtools/upc_e.rb', line 299

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

#wn ⇒ Object

W/N strings are not usable with EAN-style codes.

Raises:



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# File 'lib/barcode1dtools/upc_e.rb', line 279

def wn
  raise NotImplementedError
end