A great usage of QR codes in the real world

A look at how I built tools for managing my home using QR codes.

#obsidian#projects#webdev

QR codes are quite nifty. You can store around 3 KB in a single QR code, and you can access it with your iPhone camera, which you almost always have with you.

One recent usage of QR codes I like is for managing storage at my home.

This is a Home Depot box:

Home Depot box

Classic, high-quality boxes that are super popular for storage here in the USA.

It’s hard to know what’s in these boxes. And when they go up into storage, it’s hard to remember which thing is in what box.

My solution is to document the box contents in Obsidian. For any file in Obsidian, there’s a URL to access it in app:

obsidian://open?vault=kristian&file=7%20-%20Home%2FOrganization%2FYC-001

This file corresponds to /Home/Organization/YC-001 in my “Kristian” vault - YC-001 is the label for “Yellow Crate #001” :)

I bought some 4x5 label paper and made a quick library* for generating QR codes and printing them onto label paper.

* With ChatGPT… I’m not a Python dev! 
import json
import qrcode
import os
from reportlab.lib.pagesizes import letter
from reportlab.pdfgen import canvas
from reportlab.lib.units import inch
from PIL import Image


def create_qr_code(data, filename):
    qr = qrcode.QRCode(
        version=1,
        error_correction=qrcode.constants.ERROR_CORRECT_L,
        box_size=10,
        border=4,
    )
    qr.add_data(data)
    qr.make(fit=True)


    img = qr.make_image(fill='black', back_color='white')
    img.save(filename)


def create_pdf(config_file, output_file):
    # Create output directory if it doesn't exist
    output_dir = os.path.dirname(output_file)
    if not os.path.exists(output_dir):
        os.makedirs(output_dir)


    with open(config_file, 'r') as file:
        config = json.load(file)


    # 4x5 inches at 72 DPI
    c = canvas.Canvas(output_file, pagesize=(4 * 72, 5 * 72))
    width, height = 4 * 72, 5 * 72


    # Define positions for the stickers
    sticker_width = width / 2
    sticker_height = height / 2
    positions = [
        (0, height - sticker_height),
        (sticker_width, height - sticker_height),
        (0, height - 2 * sticker_height),
        (sticker_width, height - 2 * sticker_height)
    ]


    # Generate QR codes and place them with subtitles
    for i, pos in enumerate(positions):
        qr_filename = os.path.join(output_dir, f"qr_{i}.png")
        create_qr_code(config[f'sticker_{i+1}']['text'], qr_filename)


        qr_image = Image.open(qr_filename)
        qr_width, qr_height = sticker_width - 20, sticker_height - 40
        c.drawImage(
          qr_filename, pos[0] + 10, pos[1] + 30,
          width=qr_width, height=qr_height
        )


        # Center the subtitle text below the QR code
        subtitle_text = config[f'sticker_{i+1}']['subtitle']
        text_width = c.stringWidth(subtitle_text, "Helvetica", 10)
        x_centered = pos[0] + (sticker_width - text_width) / 2
        c.drawString(x_centered, pos[1] + 25, subtitle_text)


    c.save()


create_pdf("config.json", "out/stickers.pdf")

The corresponding config file:

{
  "sticker_1": {"text": "obsidian://open?vault=kristian&file=7%20-%20Home%2FOrganization%2FYC-001", "subtitle": "YC-001"},
  "sticker_2": {"text": "obsidian://open?vault=kristian&file=7%20-%20Home%2FOrganization%2FYC-002", "subtitle": "YC-002"},
  "sticker_3": {"text": "obsidian://open?vault=kristian&file=7%20-%20Home%2FOrganization%2FYC-003", "subtitle": "YC-003"},
  "sticker_4": {"text": "obsidian://open?vault=kristian&file=7%20-%20Home%2FOrganization%2FYC-004", "subtitle": "YC-004"}
}

Each sheet generates four labels. I can slap them on any box before it goes into storage:

QR example

Eventually, it would be cool to document everything in my house - where it is, what I have, etc. - using Obsidian and an LLM. That’s next on my list of things to do.

BTW: a better solution would be to have less stuff :)