Rendering QR Codes¶
There are five possible formats for rendering the QR Code. The first is to render it as a string of 1’s and 0’s. Next, the code can be displayed directly in compatible terminals. There are also three image based renderers. All, but the first, allow you to set the colors used. They also take a scaling factor, that way each module is not rendered as 1 pixel.
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
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.
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.
The XBM file format is a simple black and white image format. The image data
takes the form of a valid C header file. XBM rendering is handled via the
XMB’s are natively supported by Tkinter. This makes displaying QR codes in a Tkinter application very simple.
>>> 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()
Scalable Vector Graphic (SVG)¶
The SVG renderer outputs the QR code as a scalable vector graphic using
The method draws the QR code using a set of paths. By default, no background is drawn, i.e. the resulting code has a transparent background. The default foreground (module) color is black.
>>> 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()))
You can change the colors of the data-modules using the module_color parameter. Likewise, you can specify a background using the background parameter. Each of these parameters take a HTML style color.
>>> url.svg('uca.svg', scale=4, background="white", module_color="#7D007D")
You can also suppress certain parts of the SVG document. In other words you can create a SVG fragment.
Encapsulated PostScript (EPS)¶
The EPS renderer outputs the QR code an encapsulated PostScript document using
pyqrcode.QRCode.eps() method. This renderer does not require any
The method draws the EPS document using lines of contiguous modules. By default, no background is drawn, i.e. the resulting code has a transparent background. The default module color is black. Note, that a scale of 1 equates to a module being drawn at 1 point (1/72 of an inch).
>>> 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))
Portable Network Graphic (PNG)¶
The PNG renderer outputs the QR code as a portable network graphic file using
This renderer requires the pypng module.
>>> 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()))
Colors should be a list or tuple containing numbers between zero an 255. The lists should be of length three (for RGB) or four (for RGBA). The color (0,0,0) represents black and the color (255,255,255) represents white. A value of zero for the fourth element, represents full transparency. Likewise, a value of 255 for the fourth element represents full opacity.
By default, the renderer creates a QR code with the data modules colored black, and the background modules colored white.
>>> url.png('uca-colors.png', scale=6, ... module_color=[0, 0, 0, 128], ... background=[0xff, 0xff, 0xcc])