Click here for knowledge
Now, let's actually output the concatenated QR code.

--As I wrote in the knowledge section, this time I will generate a concatenated QR code in the 8bit_byte mode used in the QR code of the prescription. --The actual data to be written in the prescription is a CSV data file with Shift JIS encoding. (Line break = CR / LF / EOF available) (Defined at here)

Modify rqrcode

About the library structure of rqrcode

rqrcode is a library configuration split from v1.0.0, with rqrcode and QR code generation, which has a generation function call and an output class to an image file. It was divided into two parts, rqrcode_core in the core part.
In the project where I actually used the split QR code output, I did not fork the rqrcode or issue a Pull Request, and incorporated the above two libraries into my project code as SUBSET. (I also added tests with RSpec myself)
If you want to practice it, create a fork repository or incorporate it into your project as a SUBSET.

Add a method to write the header part of the concatenated QR code

First, add a header writing method for the concatenated QR code to QRBitBuffer, which writes the header part.

`rqrcode_core/qrcode/qr_bit_buffer.rb`


module RQRCodeCore
  class QRBitBuffer
    #Omission
    def byte_with_connected_encoding_start(length, page_number, last_page_number, parity)
      put(3, 4) #MODE indicating the concatenated QR code= 0b0011
      put(page_number, 4) #Sequence number(0〜15)
      put(last_page_number, 4) #Last sequence number(0〜15)
      put(parity, 8) #Parity value(XOR value of all data)
      put(QRMODE[:mode_8bit_byte], 4) # 8bit_byte mode value
      put(length, QRUtil.get_length_in_bits(QRMODE[:mode_8bit_byte], @version)) #Data length
    end

Create a class for concatenated QR code

There is a QR8bitByte class for 8byte_byte mode, but create a QR8BitByteWithConnected class that uses this for the concatenated QR code.

`rqrcode_core/qrcode/qr_8bit_byte_with_connected.rb`


# frozen_string_literal: true

module RQRCodeCore
  class QR8BitByteWithConnected
    attr_reader :mode, :page_number, :last_page_number, :parity

    def initialize(data, page_number, last_page_number, parity)
      @mode = QRMODE[:mode_8bit_byte]
      @data = data
      @page_number = page_number
      @last_page_number = last_page_number
      @parity = parity
    end

    def get_length
      @data.bytesize
    end

    def write(buffer)
      buffer.byte_with_connected_encoding_start(get_length, @page_number, @last_page_number, @parity)
      @data.each_byte do |b|
        buffer.put(b, 8)
      end
    end
  end
end

Add concatenated QR code option to QRCode class

As an option of the QRCode class that generates a QR code, add a function that can output a concatenated QR code. --In the case of a concatenated QR code, the capacity of the data that can be stored in one QR code is shortened by 2 bytes, but this point is not taken into consideration. (Since the original code also has a size check, you can easily implement it by adding the condition judgment in the case of the concatenated QR code.) --Please note that the QR code version (= size) is the parameter name size: xx of ʻoption`.

`rqrcode_core/qrcode/qr_code.rb`


module RQRCodeCore
  #Omission
  class QRCode
    attr_reader :modules, :module_count, :version
    #Omission
    def initialize( string, *args )
      if !string.is_a? String
        raise QRCodeArgumentError, "The passed data is #{string.class}, not String"
      end

      options               = extract_options!(args)
      level                 = (options[:level] || :h).to_sym
      #Added option judgment for concatenated QR code
      with_connected = options[:connected] || false

      #Omission

      # :byte_Error if a concatenated QR code is specified other than 8bit(Implementation is optional)
      if with_connected && mode != QRMODE_NAME[:byte_8bit]
        raise QRCodeArgumentError, 'Argument error.(Connected QRCode is byte_8bit mode only)'
      end

      max_size_array        = QRMAXDIGITS[level][mode]
      size                  = options[:size] || smallest_size_for(string, max_size_array)

      if size > QRUtil.max_size
        raise QRCodeArgumentError, "Given size greater than maximum possible size of #{QRUtil.max_size}"
      end

      #Omission
      @data_list =
        case mode
        when :mode_number
          QRNumeric.new( @data )
        when :mode_alpha_numk
          QRAlphanumeric.new( @data )
        else
          #If it is a concatenated QR code, change the generated class
          if with_connected
            page_number = options[:page_number]
            last_page_number = options[:last_page_number]
            parity = options[:parity]
            QR8BitByteWithConnected.new(@data, page_number, last_page_number, parity)
          else
            QR8bitByte.new(@data)
          end
        end

      @data_cache           = nil
      self.make
    end

Output the concatenated QR code

This time, let's output this sample in the size of version 16. --The actual data is Shift JIS encoding (line feed = with CR / LF EOF).

JAHIS7
1,1,1234567,13,Kita Internal Medicine Clinic
2,999-9999,9F, 99-999 Test Building, Kitashinagawa, Shinagawa-ku, Tokyo
3,03-9999-9991,03-9999-9992,
4,1,,Internal medicine
5,,,Physician Taro
11,,Patient Hanako,Kanja Hanako
12,2
13,20000103
21,1
22,01010016
23,symbol,number,2,
51,20200818
81,1,,
81,2,,This is a remarks column for prescriptions.
101,1,3,,1
111,1,1,,On the feet,
201,1,1,1,7,2619803XAZZZ,[General] External liquid containing alcohol for disinfection,4,1,ｍＬ
101,2,1,,5
111,2,1,,Once a day after dinner,
201,2,1,1,7,1124022F2ZZZ,[General] Lorazepam Tablets 1 mg,1,1,Lock
101,3,1,,28
111,3,1,,3 times a day after every meal,
201,3,1,1,7,3136004F2ZZZ,[General] Mecobalamin Tablets 0.5 mg,3,1,Lock
201,3,2,1,7,2171017F2ZZZ,[General] Nicorandil Tablets 5 mg,3,1,Lock
201,3,3,1,7,3962001F1ZZZ,[General] Buformin Hydrochloride Tablets 50 mg,3,1,Lock
201,3,4,1,7,1124022F1ZZZ,[General] Lorazepam Tablets 0.5 mg,3,1,Lock
201,3,5,1,7,1124026F1ZZZ,[General] Tofisopam Tablets 50 mg,3,1,Lock
201,3,6,1,2,612140503,,3,1,Lock
101,4,1,,28
111,4,1,,3 times a day after every meal,
201,4,1,1,7,2344009F2ZZZ,[General] Magnesium oxide tablets 330 mg,6,1,Lock
101,5,3,,1
111,5,1,,On the feet,
201,5,1,1,7,2619803XAZZZ,[General] External liquid containing alcohol for disinfection,4,1,ｍＬ
101,6,1,,28
111,6,1,,3 times a day after every meal,
201,6,1,1,7,3136004F2ZZZ,[General] Mecobalamin Tablets 0.5 mg,3,1,Lock
201,6,2,1,7,2171017F2ZZZ,[General] Nicorandil Tablets 5 mg,3,1,Lock
201,6,3,1,7,3962001F1ZZZ,[General] Buformin Hydrochloride Tablets 50 mg,3,1,Lock
201,6,4,1,7,1124022F1ZZZ,[General] Lorazepam Tablets 0.5 mg,3,1,Lock
201,6,5,1,7,1124026F1ZZZ,[General] Tofisopam Tablets 50 mg,3,1,Lock
201,6,6,1,2,612140503,,3,1,Lock

Method to calculate parity

Calculate the XOR value of all data.

    def create_total_text_parity(data)
      data.each_byte.inject(0) { |parity, b| parity ^ b }
    end

Method to split data

Use the slice_data_for_connected_qrcode method to divide the data into the required number.
The contents specified by option are as follows. --size = QR code version (size)-> Same as QR Code option --level = Error correction level-> Same as QRCode option --When adjust_for_sjis = true is specified, ShiftJIS double-byte characters are not split in the middle. --As explained in the Knowledge section, when read by some apps, if the ShiftJIS double-byte characters are split in the middle, the characters will be garbled. In this sample, we are trying to prevent splitting.

    #Add a require for RQRCodeCore if needed.
    LIMIT_OF_CONNECTED_QRCODE_LENGTH = 16
    CAPACITY_GAP_FOR_CONNECTED = 2

    def slice_data_for_connected_qrcode(data, options)
      capacity = binary_qrcode_capacity_from(options[:level], options[:size]) - CAPACITY_GAP_FOR_CONNECTED

      sliced =
        if options[:adjust_for_sjis]
          slice_sjis_data(data, capacity: capacity)
        else
          slice_data(data, capacity: capacity)
        end

      fail 'data for connect QRCode too many length.' if sliced.length > LIMIT_OF_CONNECTED_QRCODE_LENGTH
      sliced
    end

    def binary_qrcode_capacity_from(level, size)
      RQRCodeCore::QRMAXDIGITS[level][:mode_8bit_byte][size - 1]
    end

    def slice_sjis_data(sjis_data, capacity:)
      is_first_char = ->(char) { (char >= 129 && char <= 159) || (char >= 224 && char <= 239) }

      bytes = sjis_data.each_byte
      sliced_list = []
      while bytes.present?
        next_bytes = bytes.take(capacity)
        if is_first_char.call(next_bytes.last) && next_bytes.length != bytes
          next_bytes = bytes.take(capacity - 1)
        end

        sliced_list << next_bytes.pack('c*')
        bytes = bytes.drop(next_bytes.length)
      end

      sliced_list
    end

    def slice_data(data, capacity:)
      data.each_byte.each_slice(capacity).map { |sliced| sliced.pack('c*') }
    end

Method to automatically divide and generate QR code

    # Generate connected QRCode. (binary mode only)
    #
    #   # data   - the string you wish to encode
    #   # args
    #   #   size   - the size of the qrcode (default 4)
    #   #   level  - the error correction level
    #   #   adjust_for_sjis - true: no split sjis multi byte character
    #
    # qrcode_list = RQRCode::ConnectedQRCodeUtil.generate_binary_connected_qrcodes('hello world', size: 1, level: :m)
    def generate_binary_connected_qrcodes(data, *args)
      options = extract_options!(args)
      #If it fits in one QR code, it will be generated with a normal QR code.
      return [RQRCode::QRCode.new(data, options)] if fits_in_single_qrcode?(data, options)

      #Split data
      sliced_text = slice_data_for_connected_qrcode(data, options)
      #Generate parity
      parity = create_total_text_parity(data)
      #Generate a QR code based on the divided data
      sliced_text.map.with_index do |text, number|
        extend_args = { page_number: number, last_page_number: sliced_text.length - 1, connected: true, parity: parity }
        RQRCode::QRCode.new(text, options.merge(extend_args))
      end
    end

    def extract_options!(arr)
      arr.last.is_a?(::Hash) ? arr.pop : {}
    end

    def fits_in_single_qrcode?(data, options)
      data.each_byte.to_a.length <= binary_qrcode_capacity_from(options[:level], options[:size])
    end

Actual output


  QRCODE_SIZE = 16 # Size of QRCODE
  QRCODE_LEVEL = :l # Error correction level (L = 7%)
  MODULE_PIXEL_SIZE = 2 # Size of Pixel

  def create_qrcode_png_files_from(csv_data)
    qrcodes = RQRCode::ConnectedQRCodeUtil.generate_binary_connected_qrcodes(
      csv_data,
      size: QRCODE_SIZE,
      level: QRCODE_LEVEL,
      adjust_for_sjis: true
    )
    qrcodes.map.with_index do |qrcode, index|
      file_path = File.join('tmp', "qrcode_#{index}.png ")
      qrcode.as_png(module_px_size: MODULE_PIXEL_SIZE, file: file_path)
    end
  end

A QR code divided into three was generated. ――When rendering side by side, it is necessary to secure a clear area (margin around the QR code), so be careful.

Summary

If you record the information about the division in the header part, give the divided data and generate each QR code, you can generate the divided QR code.
Note that some readers may not be able to read if the division is specified but the actual QR code is only one. (See Knowledge)
Behavior may differ depending on the reader, so use actual equipment for operation verification. (See Knowledge)

References

This article was written with reference to the following information.

Change log

2020.08.26 Corrected the value of "MODE indicating connected QR code" written by byte_with_connected_encoding_start from 4 to 3.

[Ruby] Generate a concatenated QR code with rqrcode (Practice)