Creating and Reading QR Code in Python: A Simple Python Class using qrcode and opencv module

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We often read QR codes from different products. One of the closest example is reading QR code on top of walmart products to find out the exact price.

In this post, we will create a python class that features creating and reading QR codes.

Import Modules

Let’s first import two modules

  1. qrcode $\rightarrow$ for creating QR code from input data and then saving to an image file
  2. cv2 $\rightarrow$ for reading a QR code from image
    import qrcode
    import cv2
    

Creating a Class

Now let’s create a class like the following:

class myQRCode:
    def __init__(self):
        self.qr = qrcode.QRCode(
                        version=2,
                        error_correction=qrcode.constants.ERROR_CORRECT_L,
                        box_size=10,
                        border=5,
                    )

Because we are not passing anything while calling the class, we don’t include any parameter in the initializer method. We only create an object of the qrcode.QRCode() class.

Here,

  1. Version $\rightarrow$ size of the QR code. Typically ranges from $1-40$.
  2. box_size $\rightarrow$ size of pixel box
  3. border $\rightarrow$ thickness of the border around the code

Other Methods

Method for creating QR code

Now, we create a method that requires primarily two input data

  1. data $\rightarrow$ The data we are gonna convert to a QR code
  2. filename $\rightarrow$ The filename where we are going to save the QR code

Apart from that, for styling, we can provide two more inputs:

  1. fill_color $\rightarrow$ filling the QR code with a target color
  2. background_color $\rightarrow$ the background color of the QR code

Now, we add data to our early created object using the command self.qr.add_data(data) and then make image using self.qr.make_image(). Then finally, we save the image using <object>.save(filename).

	def create_QR_Code(self, data, filename, fill_color=None, background_color=None):
	        self.qr.add_data(data)
	        self.qr.make(fit=True)
	        if fill_color is not None and background_color is not None:
	            img = self.qr.make_image(fill=fill_color, back_color=background_color)
	        else:
	            img = self.qr.make_image()
	        img.save(filename)

Method for reading a QR code

We use cv2.imread(filename) to read the file where filename is the input for this method. Then we create an object of cv2.QRCodeDetector() class and decode using detectAndDecode() method.

	def read_QR_Code(self, filename):
	        img = cv2.imread(filename)
	        det = cv2.QRCodeDetector()
	        data, bbox, straight_qrcode = det.detectAndDecode(img)
	        return data

Full Code

Here is the full code:

class myQRCode:
    def __init__(self):
        self.qr = qrcode.QRCode(
                        version=2,
                        error_correction=qrcode.constants.ERROR_CORRECT_L,
                        box_size=10,
                        border=5,
                    )
    
    def create_QR_Code(self, data, filename, fill_color=None, background_color=None):
        self.qr.add_data(data)
        self.qr.make(fit=True)
        if fill_color is not None and background_color is not None:
            img = self.qr.make_image(fill=fill_color, back_color=background_color)
        else:
            img = self.qr.make_image()
        img.save(filename)
        
    def read_QR_Code(self, filename):
        img = cv2.imread(filename)
        det = cv2.QRCodeDetector()
        data, bbox, straight_qrcode = det.detectAndDecode(img)
        return data

Testing

Let’s create two objects of our own created myQRCode() class and try different inputs. Then we read the files to check if the outputs are correct.

obj1 = myQRCode()
obj2 = myQRCode()
obj1.create_QR_Code("This is my data", "test2.png")
print(obj1.read_QR_Code("test2.png"))
obj2.create_QR_Code("This is another data", "test3.png", 'black', 'white')
print(obj2.read_QR_Code("test3.png"))

Here, we see the following output on the terminal.

This is my data
This is another data

That’s it for today. Until next post, Cheers!!!

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