This is my own implementation of a FreeDesktop-compliant thumbnail generator for images, including RAW formats.

• Generates PNG thumbnails in standard FreeDesktop sizes (normal, large, x-large, xx-large)
• Uses Pillow for image resizing and drawing labels with original file formats
• Leverages ExifTool (via subprocess) to:
  • Extract previews from RAW files
  • Correct image orientation using EXIF metadata
• Supports multiprocessing for fast, parallel thumbnail generation
• Works with both individual files and directories (recursive)

python3 app.py [-h] [-o OUTPUT] [-j JOBS] [-f|--force] input

Examples

python3 app.py /mnt/sda1/photos/2025/ -o ~/.cache/thumbnails/ -j 16
python3 app.py /mnt/sda1/photos/2025/20250127/2J0A1537.cr3

To increase Nautilus' thumbnail cache size and retention:

gsettings set org.gnome.nautilus.preferences thumbnail-limit 536870912000  # (~500 GB)
gsettings set org.gnome.desktop.thumbnail-cache maximum-age 365            # (365 days)