Reading and Generating QR codes in Python using QRtools

This article aims to introduce the use of the python library: qrtools. This library can be used to both read QR codes and generate them.

What are QR codes?

QR code, or quick response code, is a trademark for a type of 2 dimensional barcode. 2 dimensional barcodes are similar to one dimensional barcodes, but can store more information per unit area.

Installation and Dependencies

1. Debian Linux: qrtools can be installed on debian based linux systems with the following commands

   sudo apt-get update
   sudo apt-get install python-qrtools
   

   The following dependencies must be installed as well

   [sudo] pip install pypng
   [sudo] pip install zbar
   [sudo] pip install pillow
   

2. Windows: qrtools can be installed on windows by downloading the file from here. On downloading and extraction, run the following command from inside the folder

   python setup.py install
   

Generate a QR Code

qrtools contains a class QR (can be viewed in the source code), for which we must initially create an object. The object takes the following arguments

1. data
2. pixel_size
3. level
4. margin_size
5. data_type

To create a QR code with default settings, we must simply specify the data while creating the object. Note that the data must be a unicode object if non-ASCII objects are going to be used. Python3

# Python program to generate QR code
from qrtools
import QR

# creates the QR object
my_QR = QR(data = u"Example")

# encodes to a QR code
my_QR.encode()

If the program runs successfully, it returns a value of 0, and the QR code is stored in the tmp folder. To know the exact location, use the following command

print (my_QR.filename)

Sample output

/tmp/qr-1496334996.385343/7489ebbcc2a00056ddaaaac190bce473e5c03696ea1bd8ed83cf59a174283862.png

This file can now be moved to another folder as per our convenience Python3

# Python program to generate QR code
from qrtools import QR

import os
my_QR = QR(data = u"Example")
my_QR.encode()

# command to move the QR code to the desktop
os.system("sudo mv " + my_QR.filename + " ~/Desktop")

The pixel value of the QR code may also be changed by specifying the value during the creation of the QR object. The default size tends to be a little small for reading using scanners on smartphones, so a size of around 10 would be ideal for such purposes, for example:

my_QR = QR(data = u"example", pixel_size = 10)

The below QR code has pixel size = 10, and has been encoded with a URL We can also add email data, sms data, mms data, bookmarks, etc to the QR code. The following code excerpt is taken from the source code, which specifies the various data types that can be used along with the format of the data that would be required for its usage: Python3

    # use these for custom data formats eg. url, phone number, VCARD
    # data should be an unicode object or a list of unicode objects
    data_encode = {
        'text': lambda data: data,
        'url': encode_url,
        'email': lambda data: 'mailto:' + re.compile(
            r'^mailto:', re.IGNORECASE
        ).sub('', data),
        'emailmessage': lambda data: 'MATMSG:TO:' + data[0] + ';SUB:' + data[1] + 
                               ';BODY:' + data[2] + ';;',
        'telephone': lambda data: 'tel:' + re.compile(
            r'^tel:', re.IGNORECASE
        ).sub('', data),
        'sms': lambda data: 'SMSTO:' + data[0] + ':' + data[1],
        'mms': lambda data: 'MMSTO:' + data[0] + ':' + data[1],
        'geo': lambda data: 'geo:' + data[0] + ', ' + data[1],
        'bookmark': lambda data: "MEBKM:TITLE:" + data[0] + ";URL:" + 
                                        data[1] + ";;",
        # phonebook or meCard should be a list of tuples like this:
        # [('N', 'Name'), ('TEL', '231698890'), ...]
        'phonebook': lambda data: "MECARD:" + ";".join([":".join(i) 
                                            for i in data]) + ";"
    }

From the above code, we observe the various data types that can be assigned and used while creating QR codes. For example, to use a bookmark as data we must provide data as a list, consisting of a title and the url. To accomplish this, we must do the following Python3

# Python program to generate QR code
from qrtools import QR

# creates the QR object
my_QR = QR(data = [u"geeksforgeeks", u"https://www.geeksforgeeks.org/"], 
                                      data_type = 'bookmark')

# encodes to a QR code
my_QR.encode()

Read a QR code

Scanning and reading a QR code is relatively simple. While creating the QR object, we must simply specify the path to the QR code as an argument. Suppose we are trying to decode the QR code created at the beginning of the article. Python3

# Python program to Scan and Read a QR code
from qrtools import QR
my_QR = QR(filename = "home/user/Desktop/qr.png")

# decodes the QR code and returns True if successful
my_QR.decode()

# prints the data
print (my_QR.data)

Output :

Example

We may also print the values of the other parameters passed while creating the QR object to generate the QR code, for example, using the same QR code generated at the beginning of the article, additionally adding these print statements would give the following additional output

print (my_QR.data_type)
print (my_QR.pixel_size)
print (my_QR.margin_size)

Output:

text
3
4