Thermal Label Printer

Web app for converting eBay shipping label PDFs to 4x6 thermal labels and printing to a TSPL-compatible thermal printer. Also includes a packing slip generator for BThrifty Online.

Features

• Upload eBay shipping label PDFs via web interface
• Auto-detects label region on any page size using pixel analysis
• Rotates landscape labels 90° for portrait 4×6 printing
• Scales to fit inside 4×6 label (no distortion, no cutoff)
• Live preview of processed label before printing
• Prints to CUPS thermal printer queue
• Packing slip generator (gen_packing_slip.py) for BThrifty Online

Requirements

• Python 3.12+
• CUPS (for printer queue management)
• A TSPL-compatible thermal label printer (tested with YXWL Y42BT)

Python Dependencies

pip3 install flask pymupdf pillow numpy

Setup

1. Clone the repo

git clone https://github.com/zachsplat/Thermalprinter.git
cd Thermalprinter

2. Install Python dependencies

pip3 install flask pymupdf pillow numpy

3. Set up the CUPS printer queue

The app expects a CUPS printer queue named Y42BT_TSPL with a 4×6 inch page size (w288h432).

The driver/ directory contains the required files:

• Y42BT_TSPL.ppd — PPD file for the YXWL Y42BT thermal printer
• xprinter-tspl — CUPS filter (Python) that converts PDF to TSPL commands

Install the filter and create the queue:

# Install the CUPS filter
sudo cp driver/xprinter-tspl /usr/lib/cups/filter/xprinter-tspl
sudo chmod +x /usr/lib/cups/filter/xprinter-tspl

# Create the printer queue (adjust USB URI for your device)
lpadmin -p "Y42BT_TSPL" -E -v "usb:///Y42BT?serial=0000000" -P driver/Y42BT_TSPL.ppd

Verify the printer is detected:

lpinfo -v
lpstat -p Y42BT_TSPL

4. Run the app

python3 app.py

The app listens on 0.0.0.0:5000 (all interfaces).

5. (Optional) Run as a systemd service

Create /etc/systemd/system/label-printer.service:

[Unit]
Description=Label Printer Web App
After=network.target

[Service]
Type=simple
User=YOUR_USERNAME
WorkingDirectory=/path/to/Thermalprinter
ExecStart=/usr/bin/python3 /path/to/Thermalprinter/app.py
Restart=always
RestartSec=5
Environment=PYTHONUNBUFFERED=1

[Install]
WantedBy=multi-user.target

Enable and start:

sudo systemctl daemon-reload
sudo systemctl enable label-printer.service
sudo systemctl start label-printer.service

6. (Optional) Access via Tailscale

The app binds to 0.0.0.0:5000, so if Tailscale is running on the host, you can access it from any device on your tailnet:

http://<tailscale-ip>:5000

Check your Tailscale IP with:

tailscale ip -4

Usage

1. Open the web app in your browser
2. Upload an eBay shipping label PDF
3. Preview the processed 4×6 label
4. Click Print to send to the thermal printer

Files

• app.py — Flask web application
• templates/index.html — Web UI
• gen_packing_slip.py — Packing slip PDF generator for BThrifty Online
• test_app.py — Test suite
• driver/Y42BT_TSPL.ppd — PPD file for the YXWL Y42BT thermal printer
• driver/xprinter-tspl — CUPS filter (PDF → TSPL)

License

Private repository. All rights reserved.