Streamlit is a popular framework for building interactive web applications with Python. In this blog post, we’ll introduce you to a Streamlit toolkit that empowers you to effortlessly create and scan QR codes using Python. With just a few lines of code, you’ll be generating and decoding QR codes like a pro.

But before proceeding let us understand what is QR first. QR stands for Quick Response. In a world where convenience is on the top, QR codes have emerged as a simple yet powerful tool for seamless information exchange whether you want to encode data for marketing campaigns, share contact information, or facilitate mobile payments, QR codes offer a simple and convenient solution.

Let us start with the code

Step 1: Setting Up the Environment (streamlit, pyqrcode, opencv-python, pyzbar)

Before starting the code, we need to set up the environment first. For that we need to download and import the following libraries like streamlit, pyqrcode, opencv, and pyzbar. You can also use pip for that.

import streamlit as st
import pyqrcode
from io import BytesIO
from PIL import Image
import cv2
from pyzbar import pyzbar

Step 2: Generate QR Code

In this step, we will create a function that will generate QR for the data which will be inputted by the user.
The data inputted by the user will be in

def generate_qr_code(data):
    """
    Generates a QR code image from the provided data.

    Parameters:
    data (str): The data to encode in the QR code.

    Returns:
    BytesIO: The QR code image in a BytesIO buffer.
    """
    qr = pyqrcode.create(data)
    buffer = BytesIO()
    qr.png(buffer, scale=6)
    buffer.seek(0)
    return buffer

Step 3: Decode QR Code

Next, we will create a function to decode QR codes from images. This is where OpenCV and pyzbar come into play. We define a function decode_qr_code(frame) that takes an image frame (in the form of a NumPy array) as input. Using OpenCV, we capture frames from the camera and pass them to pyzbar for QR code decoding. The decoded data is returned as a list of strings

def decode_qr_code(frame):
    """
    Decodes QR codes in the given image frame.

    Parameters:
    frame (numpy.ndarray): The image frame to scan for QR codes.

    Returns:
    list: A list of decoded QR code data.
    """
    decoded_objects = pyzbar.decode(frame)
    qr_codes = [obj.data.decode('utf-8') for obj in decoded_objects]
    return qr_codes

You are reading Streamlit app for QR Toolkit in 6 simple steps

Step 4: Creating QR Codes in Real-Time

Here, we will code using streamlit functions and call the function “generate_qr_code” so that a qr code can be created instantly on behalf of the data inputted by the user. This function will create a QR image and also a download button will be active to download the QR in png format.

def create_qr_code():
    st.title("QR Code Generator")
    data = st.text_input("Enter the data to encode in the QR code")  # input by user

    if data:
        qr_image = generate_qr_code(data)    # function generate_qr_code with data as argument
        img = Image.open(qr_image)

        st.image(img, caption="Generated QR Code", use_column_width=False)

        st.download_button(
            label="Download QR Code",
            data=qr_image,
            file_name="qrcode.png",
            mime="image/png"
        )

Step 5: Scanning and Decoding QR Codes in Real-Time

In this function, we will code to decode a QR scanned through your laptop camera. This function will be solely responsible for scanning a QR and also since we are making it a streamlit application we need to create 2 more functions to start and stop scanning which will be called as per requirement.

After scanning a QR frame by frame, we will call the function decode_qr_code which will decode the QR and all of this will happen in a loop which will be stopped after decoding the QR.

def scan_qr_code():
    st.title("QR Code Scanner")
    st.write("Click the button below to start the camera and scan a QR code.")

    # Initialize session state for control buttons and decoded message
    if "scanning" not in st.session_state:
        st.session_state.scanning = False

    if "decoded_message" not in st.session_state:
        st.session_state.decoded_message = None

    def start_scanning():
        st.session_state.scanning = True

    def stop_scanning():
        st.session_state.scanning = False

    if not st.session_state.scanning:
        if st.button('Start Scanning', key='start'):
            start_scanning()

    if st.session_state.scanning:
        cap = cv2.VideoCapture(0)
        stframe = st.empty()

        while st.session_state.scanning:
            ret, frame = cap.read()
            if not ret:
                st.write("Failed to capture image.")
                break

            qr_codes = decode_qr_code(frame)

            # Display the frame
            stframe.image(frame, channels="BGR")

            # Display the decoded QR codes if it's a new message
            if qr_codes:
                if st.session_state.decoded_message != qr_codes[0]:
                    st.session_state.decoded_message = qr_codes[0]
                    st.success(f"Decoded QR Code: {qr_codes[0]}")
                    break

        if st.button('Stop Scanning', key='stop', on_click=stop_scanning):
            cap.release()
            cv2.destroyAllWindows()

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Step 6: Putting It All Together– The Main program

Here we will use radio buttons with name like “Create QR” and “Scan QR” and the user has to choose any one option. As per the user’s choice the functions from above will be called.

st.title("QR Code Toolkit")

option = st.radio(
    "Choose an option:",
    ("Create QR", "Scan QR")
)

if option == "Create QR":
    create_qr_code()
elif option == "Scan QR":
    scan_qr_code()

And there you have it – a simple yet powerful QR code toolkit built with Python and Streamlit whether you’re a pro developer or a noob, you just have to follow the instructions step by step and Bingo! you have created your app.

You were reading Streamlit app for QR Toolkit in 6 simple steps

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