QR Reader from Byte Array

readqr.md

Read QR from Byte Array

The code below will read byte array saved in a txt file, outputs the qr string and saves the qr image, like so

python readqr.py bytearray_in_text_file.txt

Usage

• Save the python script below
• python -m venv env
• source env/bin/activate
• pip install pillow opencv-python
• If all good, just use it like the example above.

import argparse
import io
import ast
from pathlib import Path
from PIL import Image
import cv2
import numpy as np

def main():
    parser = argparse.ArgumentParser(description="Decode QR from byte array in txt file")
    parser.add_argument("txtfile", help="Path to txt file containing byte array")
    args = parser.parse_args()

    txt_path = Path(args.txtfile)

    with open(txt_path, "r") as f:
        content = f.read().strip()

    byte_array = ast.literal_eval(content)

    byte_data = bytes((b + 256) % 256 for b in byte_array)

    png_path = txt_path.with_suffix(".png")

    image = Image.open(io.BytesIO(byte_data))
    image.save(png_path)
    print(f"Saved as {png_path}")

    img_cv = cv2.cvtColor(np.array(image), cv2.COLOR_RGB2BGR)
    detector = cv2.QRCodeDetector()
    qr_data, _, _ = detector.detectAndDecode(img_cv)

    if qr_data:
        print("QR Payload:", qr_data)
    else:
        print("No QR code")

if __name__ == "__main__":
    main()