adaptronic_label-printer/old_code/PAPER_SIZE_ISSUE_ANALYSIS.md

Label Printing Workflow Analysis - Paper Size Issue

🔍 Problem Identified

Issue: Labels printing on 90cm continuous roll instead of 35mm x 25mm label

• PDF is created with correct size (35mm x 25mm)
• Printer receives PDF but ignores the page dimensions
• Printer defaults to continuous roll mode
• Label content prints at the end of a long paper strip

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📊 Current Workflow Analysis

Step 1: PDF Generation ✅ (Working)

print_label_pdf.py creates PDF:
- Page size: 3.5cm x 2.5cm (35mm x 25mm)
- Layout: 1/3 image + 2/3 text area
- Quality: 1200 DPI, no compression

Status: PDF dimensions are CORRECT

Step 2: Printing via SumatraPDF ❌ (Problem)

SumatraPDF command:
-print-to <printer>
-silent
-print-settings noscale,landscape,fit
<pdf_file>

Problem: SumatraPDF doesn't communicate page size to printer driver

• Printer uses its default paper size setting
• If printer is set to "Continuous" or "Roll" mode → prints on long paper
• No explicit paper size passed to printer driver

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🛠️ Root Cause

Thermal label printers need EXPLICIT paper size configuration:

1. Windows Printing System Issue:

   • PDF page size ≠ Printer paper size
   • Printer driver must be told: "USE THIS EXACT SIZE"
   • SumatraPDF: Generic PDF viewer, doesn't set printer DEVMODE

2. Printer Default Settings:

   • Most thermal printers default to continuous roll
   • Without explicit size, they print entire "page" length
   • Result: 90cm of paper with label at the end

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✅ Proposed Solutions

Solution 1: Configure Printer Paper Size (Recommended)

Manual Configuration:

1. Open Printer Preferences for "Labels" printer
2. Go to Page Setup or Paper/Quality tab
3. Set paper size to Custom: 35mm x 25mm
4. Set orientation to Landscape
5. Save as default

PowerShell Script:

# Run the printer configuration script
.\configure_label_size.ps1

Pros:

• ✅ One-time setup
• ✅ Works with any PDF viewer
• ✅ Simplest solution

Cons:

• ❌ Needs manual configuration per computer
• ❌ Settings can be reset by driver updates

---

Solution 2: Use Win32 Print API with Explicit Size (Best Control)

Use print_with_size.py module that:

• Opens printer with Win32 API
• Sets DEVMODE structure with exact dimensions:

  devmode.PaperSize = 256  # Custom
  devmode.PaperLength = 250  # 25mm in 0.1mm units
  devmode.PaperWidth = 350   # 35mm in 0.1mm units
  devmode.Orientation = 2    # Landscape
  

• Prints with guaranteed size

Implementation:

# In print_label.py, replace SumatraPDF call with:
from print_with_size import set_printer_paper_size, print_with_custom_size

# Configure printer once
set_printer_paper_size(printer_name, 35, 25)

# Then print normally
print_to_printer(printer_name, pdf_file)

Pros:

• ✅ Programmatic control
• ✅ Always sets correct size
• ✅ No manual configuration needed

Cons:

• ❌ More complex code
• ❌ Windows-only
• ❌ Requires pywin32

---

Solution 3: Use Label Template PDF (Most Reliable)

Create a proper label template that printers recognize:

1. Design in Label Software:

   • Use manufacturer's label design software (e.g., Zebra Designer, BarTender)
   • Or use professional tool like Adobe Illustrator
   • Export as PDF with embedded printer settings

2. Template Features:

   • Embedded page size metadata
   • Printer-specific settings
   • Registration marks (optional)

3. Dynamic Field Replacement:

   • Template has placeholder text: {COMANDA}, {ARTICLE}, {SERIAL}
   • Python replaces placeholders before printing
   • Or use PDF form fields

Implementation:

# Create template with proper settings
from PyPDF2 import PdfReader, PdfWriter
from reportlab.pdfgen import canvas
from reportlab.lib.units import mm

def fill_label_template(template_path, data, output_path):
    """
    Fill label template with data.
    Template has proper printer settings embedded.
    """
    # Read template
    template = PdfReader(template_path)
    
    # Create overlay with data
    packet = io.BytesIO()
    c = canvas.Canvas(packet, pagesize=(35*mm, 25*mm))
    
    # Add text at specific coordinates
    c.setFont("Helvetica-Bold", 8)
    c.drawString(15*mm, 18*mm, f"Nr. Comanda: {data['comanda']}")
    c.drawString(15*mm, 12*mm, f"Nr. Art.: {data['article']}")
    c.drawString(15*mm, 6*mm, f"Serial No.: {data['serial']}")
    c.save()
    
    # Merge with template
    overlay = PdfReader(packet)
    page = template.pages[0]
    page.merge_page(overlay.pages[0])
    
    # Write output
    writer = PdfWriter()
    writer.add_page(page)
    
    with open(output_path, 'wb') as f:
        writer.write(f)
    
    return output_path

Pros:

• ✅ Most reliable across different systems
• ✅ Printer recognizes format immediately
• ✅ Professional appearance
• ✅ Can include printer-specific optimizations

Cons:

• ❌ Requires template creation/design
• ❌ Changes need template update

---

🎯 Recommended Approach

Immediate Fix (5 minutes):

# 1. Configure printer paper size
.\configure_label_size.ps1

# OR manually:
# - Open Printer Preferences
# - Set paper size to 35mm x 25mm
# - Set orientation to Landscape

Long-term Solution (30 minutes):

1. Create proper label template in label design software
2. Export as PDF with embedded settings
3. Use template-based printing in application

Alternative (if above doesn't work):

1. Integrate print_with_size.py module
2. Modify print_label.py to use Win32 API printing
3. Explicit paper size on every print job

---

📝 Implementation Priority

Priority 1 (DO NOW):

1. ✅ Configure printer manually
2. ✅ Test with current code
3. ✅ Verify label prints at correct size

Priority 2 (THIS WEEK):

1. 🔄 Create label template with proper settings
2. 🔄 Test template-based printing
3. 🔄 Update application to use template

Priority 3 (IF NEEDED):

1. ⏳ Implement Win32 API printing
2. ⏳ Add automatic paper size detection
3. ⏳ Create printer setup wizard

---

🧪 Testing Steps

After implementing any solution:

1. Test print:

   python test_quality.py
   

2. Verify:

   • ✓ Paper stops at 35mm (not 90cm)
   • ✓ Label fills entire label area
   • ✓ No blank space before/after label
   • ✓ Text is readable and properly positioned

3. Check printer:

   • ✓ Paper advance is correct
   • ✓ No paper waste
   • ✓ Multiple labels print consecutively

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📞 Quick Fix Script

Create and run this PowerShell script to configure your printer now:

File: configure_label_size.ps1

$printerName = "Labels"

Write-Host "Configuring printer for 35mm x 25mm labels..." -ForegroundColor Cyan

# Open printer preferences dialog for manual config
rundll32 printui.dll,PrintUIEntry /e /n "$printerName"

Write-Host ""
Write-Host "In the printer preferences window:" -ForegroundColor Yellow
Write-Host "1. Find 'Paper Size' or 'Media' settings" -ForegroundColor White
Write-Host "2. Select 'Custom' or create new size: 35mm x 25mm" -ForegroundColor White
Write-Host "3. Set orientation to: Landscape" -ForegroundColor White
Write-Host "4. Click OK to save" -ForegroundColor White
Write-Host ""
Write-Host "After configuration, test with: python test_quality.py" -ForegroundColor Green

Run: .\configure_label_size.ps1

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🎓 Why This Happens

Technical Explanation:

Thermal label printers have two modes:

1. Label Mode: Prints on predefined label sizes (35mm, 50mm, etc.)
2. Continuous Mode: Prints on continuous roll (any length)

When you send a PDF:

• PDF says: "I'm 35mm x 25mm"
• Printer says: "I don't see a label size command, using default (continuous)"
• Result: Prints on continuous roll

Solution: Tell printer explicitly to use Label Mode with 35mm x 25mm size.

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Last Updated: February 13, 2026
Status: Solution pending - user must configure printer paper size