label_printer/documentation/QUICK_REFERENCE.md

Label Printing System - Quick Reference Card

System Specifications ✓

Parameter	Value	Notes
Label Width	11.5 cm	Full width
Label Height	8 cm	Full height
Rows	3	SAP-Nr, Cantitate, Lot Nr
Barcode Height	18 mm (1.8 cm)	Fixed, optimal for scanning
Barcode Format	Code128	Standard barcode format
Character Limit	25 chars max	Per field
DPI	300	Print-ready quality
File Format	PDF	Vector-based, professional
Margin	3 mm	All sides

Quick Start

1. Activate Environment

cd /srv/Label-design
source venv/bin/activate

2. Run GUI

python label_printer_gui.py

3. Enter Data

• SAP-Nr: Up to 25 characters
• Cantitate: Up to 25 characters
• Lot Nr: Up to 25 characters
• Select Printer

4. Print

• Click "PRINT LABEL"
• PDF generates automatically
• Sends to printer

Command Line Usage

# Generate PDF label
python3 -c "from print_label import print_label_standalone; \
print_label_standalone('SAP-123|100|LOT-ABC', 'printer_name')"

# Generate without printing (test)
python3 -c "from print_label import create_label_pdf; \
pdf = create_label_pdf('SAP-123|100|LOT-ABC'); \
print(f'Generated: {pdf}')"

Label Data Format

Input Format: "SAP|CANTITATE|LOT"

Example: "SAP-12345|100|LOT-ABC"
         └─────┬─────┘ └──┬──┘ └──┬──┘
         SAP-Nr   Qty    Lot Nr
         
Each becomes a barcode row in the PDF

Barcode Specifications

Aspect	Specification	Details
Type	Code128	Standard barcode
Height	18 mm	Fixed (1.8 cm)
Width	Auto	Fits within label
Module Width	0.5 mm	Bar thickness
Quiet Zone	2 mm	Auto-applied
Max Length	25 chars	Auto-truncates

File Locations

/srv/Label-design/
├── label_printer_gui.py      ← GUI application
├── print_label.py            ← Main module (PDF/PNG)
├── print_label_pdf.py        ← PDF generation engine
├── requirements_gui.txt      ← Dependencies
└── venv/                     ← Virtual environment

Generated Files

Labels are saved with timestamps:

final_label_20260205_001617.pdf
           └─────────┬─────────┘
           YYYYMMDD_HHMMSS

Files are retained in working directory for reprinting.

Troubleshooting

PDF Won't Generate

# Check dependencies
pip list | grep reportlab

# Reinstall if needed
pip install reportlab

Barcode Won't Scan

• Verify printer DPI (300+ required)
• Check label dimensions (11.5cm × 8cm)
• Use "Borderless" printing
• Test with standard scanner

Text Gets Cut Off

• Max 25 characters per field
• Longer text auto-truncates
• Check for special characters

File Not Found

# Verify virtual environment is active
which python
# Should show: /srv/Label-design/venv/bin/python

Printer Setup (CUPS)

View Available Printers

lpstat -p -d

Configure Printer Size

# Open CUPS web interface
http://localhost:631

Test Print

python3 -c "from print_label import print_label_standalone; \
print_label_standalone('TEST|123|ABC', 'your_printer_name', use_pdf=True)"

Documentation

• Full Guide: PDF_UPGRADE_GUIDE.md
• Setup Guide: QUICK_START.md
• Barcode Details: BARCODE_HEIGHT_CORRECTION.md
• Test Results: TEST_RESULTS_PDF_SYSTEM.md

API Summary

Simple Function

from print_label import print_label_standalone
print_label_standalone(text, printer, use_pdf=True)

PDF Generation

from print_label import create_label_pdf
pdf_file = create_label_pdf("SAP|QTY|LOT")

Advanced (Custom Size)

from print_label_pdf import PDFLabelGenerator
gen = PDFLabelGenerator(label_width=11.5, label_height=8)
pdf = gen.create_label_pdf("SAP", "QTY", "LOT", "output.pdf")

Performance

Task	Time
Single label PDF	200-500ms
Single label PNG	300-600ms
Batch (4 labels)	~1.5 sec
Print submission	~100ms

Quality Levels

Standard (300 DPI)

• Good for most applications
• Barcode easily scannable
• Default setting

High Quality (600 DPI)

gen = PDFLabelGenerator(dpi=600)

• Premium color reproduction
• Extra-high barcode precision

Common Issues & Solutions

Issue	Cause	Solution
Barcode too small	Old config	Update to v2.0+
Text cut off	>25 chars	Values auto-truncate
PDF won't print	Printer config	Check CUPS settings
Module not found	Missing venv	Run source venv/bin/activate
No barcodes	Generation error	Falls back to text

Environment Variables (Optional)

# Set default printer
export CUPS_DEFAULT_PRINTER="your_printer"

# Set temporary directory
export TMPDIR="/tmp/labels"

Support Resources

1. Error Messages - Check console output
2. GUI Issues - Verify Kivy installation
3. Print Issues - Check CUPS configuration
4. Barcode Issues - Test with standard scanner

System Requirements

• Python: 3.10+
• OS: Linux (CUPS required)
• Printer: Any CUPS-compatible printer
• Display: For GUI (optional, can run headless)

Version Info

• System Version: 2.0 (PDF-based)
• Release Date: February 5, 2026
• Status: ✓ Production Ready

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Quick Notes:

• Always activate venv before running
• Label size is 11.5cm × 8cm (fixed)
• Barcode height 18mm (fixed)
• Max 25 characters per field (auto-truncates)
• PDF format for best quality
• Use CUPS for printing