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Thumbnail Conversion to WebP Format

This document describes the thumbnail conversion process that converts existing JPEG thumbnails to the new WebP format for better compression and quality.

Overview

The thumbnail conversion system includes:

  • New thumbnail service with WebP support and max-width-only resizing
  • Conversion script to update existing images
  • Test script to verify functionality
  • Docker integration for automatic conversion on deployment

Changes Made

1. Updated Thumbnail Service (app/services/thumbnail_service.py)

  • Added create_resized_image_max_width() method for max-width-only resizing
  • Added WebP format support for thumbnails
  • Updated create_thumbnail() to use WebP format (300px max width)
  • Updated create_detail_image() to use JPEG format (800px max width)

2. New Image Specifications

Image Type Max Width Format Quality Extension Compression
Thumbnail 300px WebP 80% .webp method=6, optimize=True
Detail 800px WebP 85% .webp method=6, optimize=True

Scripts

1. Production Conversion Script (generate_production_thumbnails.py)

Purpose: Converts all existing JPEG thumbnails to WebP format.

Features:

  • Fetches all images from database
  • Identifies images needing conversion (JPEG thumbnails)
  • Downloads original images from storage
  • Generates new WebP thumbnails using max-width logic
  • Uploads new thumbnails and updates database
  • Deletes old JPEG thumbnails
  • Comprehensive logging and error handling

Usage:

# Run locally (for testing)
cd py_backend
python generate_production_thumbnails.py

# Run in Docker (automatic on deployment)
docker-compose up

2. Test Script (test_thumbnail_conversion.py)

Purpose: Verifies thumbnail conversion works before production deployment.

Features:

  • Tests WebP thumbnail generation
  • Tests JPEG detail image generation
  • Validates file formats
  • Tests database connection
  • Safe for local testing

Usage:

cd py_backend
python test_thumbnail_conversion.py

Docker Integration

The Dockerfile has been updated to:

  1. Make the conversion script executable
  2. Run the script automatically during container startup
  3. Log conversion progress

Startup sequence:

  1. Database migrations
  2. Thumbnail conversion
  3. FastAPI server startup

Conversion Process

What Gets Converted

  • ✅ Images with existing JPEG thumbnails (.jpg, .jpeg) → WebP
  • ✅ Images with existing JPEG detail images (.jpg, .jpeg) → WebP
  • ❌ Images without thumbnails (skipped)
  • ❌ Images with existing WebP thumbnails (skipped)
  • ❌ Images with existing WebP detail images (skipped)

Conversion Steps

  1. Scan Database: Find all images with JPEG thumbnails/details
  2. Fetch Original: Download original image from storage
  3. Generate WebP: Create new WebP thumbnail (300px max width, 80% quality) and detail (800px max width, 85% quality)
  4. Upload: Upload new WebP images to storage
  5. Update Database: Update thumbnail_key, thumbnail_sha256, detail_key, detail_sha256
  6. Cleanup: Delete old JPEG thumbnails and details
  7. Log Progress: Track conversion statistics

Error Handling

  • Failed conversions are logged but don't stop the process
  • Database rollback on errors
  • Graceful handling of missing files
  • Comprehensive error reporting

Monitoring

Log Files

  • Console output: Real-time progress
  • thumbnail_conversion.log: Detailed conversion log
  • Docker logs: Container-level logging

Conversion Statistics 

==================================================
THUMBNAIL CONVERSION SUMMARY
==================================================
Images converted to WebP: 150
Images skipped (already WebP or no thumbnail): 25
Images with errors: 2
Total images processed: 177
==================================================

Rollback Plan

If issues occur, you can:

  1. Stop the container before conversion completes
  2. Restore from backup if database was modified
  3. Manually revert by updating thumbnail_key fields
  4. Check logs for specific error details

Performance Considerations

Storage Impact

  • WebP images are typically 25-35% smaller than JPEG
  • Both thumbnails and detail images use WebP format
  • Old JPEG thumbnails and details are deleted after conversion
  • Temporary storage needed during conversion process

Processing Time

  • Depends on number of images and image sizes
  • Progress logged every 10 images
  • Can be monitored via logs

Memory Usage

  • Processes one image at a time
  • Minimal memory footprint
  • Suitable for containerized environments

Troubleshooting

Common Issues

  1. Database Connection Errors

    • Check database credentials
    • Verify network connectivity
    • Check database server status

  2. Storage Access Errors

    • Verify storage credentials (S3/local)
    • Check file permissions
    • Verify storage paths

  3. Image Processing Errors

    • Check Pillow installation
    • Verify image file integrity
    • Check available disk space

Debug Commands 

# Test thumbnail service
python test_thumbnail_conversion.py

# Check database connection
python -c "from app.database import SessionLocal; db = SessionLocal(); print(db.query(Images).count()); db.close()"

# Check storage access
python -c "from app import storage; print(storage)"

Future Enhancements

Potential improvements:

  • Batch processing for large datasets
  • Parallel conversion for faster processing
  • Incremental conversion for new images only
  • Conversion metrics dashboard
  • Automatic retry for failed conversions