Rendering QR Codes¶

Text Based Rendering¶

The pyqrcode module includes a basic text renderer. This will return a string containing the QR code as a string of 1’s and 0’s, with each row of the code on a new line. A data module in the QR Code is represented by a 1. Likewise, 0 is used to represent the background of the code.

The purpose of this renderer is to allow users to create their own renderer if none of the built in renderers are satisfactory.

>>> number = pyqrcode.create(123)
>>> print(number.text())
00000000000000000000000000000
00000000000000000000000000000
00000000000000000000000000000
00000000000000000000000000000
00001111111011110011111110000
00001000001000101010000010000
00001011101001010010111010000
00001011101010011010111010000
00001011101000100010111010000
00001000001001001010000010000
00001111111010101011111110000
00000000000001011000000000000
00000010111011010100010010000
00001011110001111101010010000
00000111111011100101001000000
00001001100011010011110010000
00001111111001101011001110000
00000000000010000000001100000
00001111111000111100100100000
00001000001011010110001100000
00001011101010110000101010000
00001011101001111111010100000
00001011101011101001011010000
00001000001001011001110000000
00001111111000011011011010000
00000000000000000000000000000
00000000000000000000000000000
00000000000000000000000000000
00000000000000000000000000000

Terminal Rendering¶

QR codes can be directly rendered to a compatible terminal in a manner readable by QR code scanners. The rendering is done using ASCII escape codes. Hence, most Linux terminals are supported. The QR code’s colors can even be set.

>>> text = pyqrcode.create('Example')
>>> print(text.terminal())
>>> print(text.terminal(module_color='red', background='yellow'))
>>> print(text.terminal(module_color=5, background=123, quiet_zone=1))

Rendering colors in a terminal is a tricky business. Beyond the eight named colors, compatibility becomes problematic. With this in mind it is best to stick to the eight well known colors: black, red, green, yellow, blue, magenta, and cyan. Although, these colors are also supported on almost every color terminal: light gray, dark gray, light red, light green, light blue, light yellow, light magenta, light cyan, and white.

There are two additional named colors. The first is “default” it corresponds to the default background color of the terminal. The other is “reverse”, this inverts the current background color. These are the default colors used by the terminal method.

The terminal method also support the 256 color scheme. This is the least transportable of the color schemes. To use this color scheme simply supply a number between 0 and 256. This number will act as an index to the terminal’s color palette. What color that index actually corresponds to is system dependent. In other words, while most terminal emulators support 256 colors, the there is no way to tell what color will be actually displayed.

Image Rendering¶

There are three ways to get an image of the generated QR code. All of the renderers have a few things in common.

Each renderer takes a file path or writable stream and draws the QR code there. The methods should auto-detect which is which.

Each renderer takes a scale parameter. This parameter sets the size of a single data module in pixels. Setting this parameter to one, will result in each data module taking up 1 pixel. In other words, the QR code would be too small to scan. What scale to use depends on how you plan to use the QR code. Generally, three, four, or five will result in small but scanable QR codes.

QR codes are also supposed to have a quiet zone around them. This area is four modules wide on each side. The purpose of the quiet zone is to make scanning a printed area more reliable. For electronic usages, this may be unnecessary depending on how the code is being displayed. Each of the renderers allows you to set the size of the quiet zone.

Many of the renderers, also, allow you to set the module and background colors. Although, how the colors are represented are renderer specific.

>>> import pyqrcode
>>> import tkinter
>>> # Create and render the QR code
>>> code = pyqrcode.create('Knights who say ni!')
>>> code_xbm = code.xbm(scale=5)
>>> # Create a tk window
>>> top = tkinter.Tk()
>>> # Make generate the bitmap image from the redered code
>>> code_bmp = tkinter.BitmapImage(data=code_xbm)
>>> # Set the code to have a white background,
>>> # instead of transparent
>>> code_bmp.config(background="white")
>>> # Bitmaps are accepted by lots of Widgets
>>> label = tkinter.Label(image=code_bmp)
>>> # The QR code is now visible
>>> label.pack()

>>> url = pyqrcode.create('http://uca.edu')
>>> url.svg('uca.svg', scale=4)
>>> # in-memory stream is also supported
>>> buffer = io.BytesIO()
>>> url.svg(buffer)
>>> # do whatever you want with buffer.getvalue()
>>> print(list(buffer.getvalue()))

>>> url.svg('uca.svg', scale=4, background="white", module_color="#7D007D")

>>> qr = pyqrcode.create('Hello world')
>>> qr.eps('hello-world.eps', scale=2.5, module_color='#36C')
>>> qr.eps('hello-world2.eps', background='#eee')
>>> out = io.StringIO()
>>> qr.eps(out, module_color=(.4, .4, .4))

>>> url = pyqrcode.create('http://uca.edu')
>>> with open('code.png', 'w') as fstream:
...     url.png(fstream, scale=5)
>>> # same as above
>>> url.png('code.png', scale=5)
>>> # in-memory stream is also supported
>>> buffer = io.BytesIO()
>>> url.png(buffer)
>>> # do whatever you want with buffer.getvalue()
>>> print(list(buffer.getvalue()))

>>> url.png('uca-colors.png', scale=6,
...         module_color=[0, 0, 0, 128],
...         background=[0xff, 0xff, 0xcc])