AtlasToolkit

Spine Atlas Toolkit - Extract, modify, and repack atlas sprites.

A tool for working with Spine atlas files, available as a hosted web app, a desktop app (powered by pywebview), or run directly from source. View atlas regions, extract individual sprites, replace sprites with other images, and repack the atlas — all through the same simple interface everywhere.

Usage

• Web app — use it directly, no installation required: 👉 https://com55.github.io/AtlasToolkit/
• Desktop app — download the pre-built executables from Releases.
  • Windows is distributed as an installer (AtlasToolkit-Setup-x64.exe, per-user, no admin) plus a portable zip. The installed build updates itself silently in-app; the portable build links to the releases page.
  • One-time migration: builds made before the installer switch used the old single-exe auto-update and will report "asset not found" when checking for this release — download and run the new installer once manually.
• From source (in-development / unstable) — clone the repository:

  git clone https://github.com/com55/AtlasToolkit.git
  cd AtlasToolkit

Setup & Run (desktop app, from source)

Once you are inside the project directory, choose your preferred method:

• Using uv (Recommended)

  uv sync
  uv run python main.py

• Using pip

  pip install -r requirements.txt
  python main.py

  or

  pip install pillow pywebview requests
  python main.py

Setup & Run (web app, from source)

cd www
# Open index.html in your browser, or serve it: python3 -m http.server

Features

• Atlas Preview — View the full atlas image with region overlays
• Region Extraction — Extract individual sprites or all regions at once
• Sprite Modification — Replace sprites with mod images; the atlas is automatically repacked into a compact, square-ish layout after every modification
• Smart Repack — Regions are deduplicated and tightly packed, favoring a near-square canvas over the smallest possible one (up to 15% larger, if it makes the sheet noticeably squarer)
• Drag & Drop — Load .atlas files by dragging them into the app; in Modify Mode, drop a .png image directly to apply it as a mod
• Copy to Clipboard — Right-click the preview image to copy it to clipboard (Extract Mode)
• Auto Format Conversion — Automatically converts LibGDX atlas format (xy/orig/offset) to the Spine format on load
• Multi-page Atlas — Supports atlas files that reference multiple page images
• File Association (desktop app) — Can be set as the default app for .atlas files; opening an atlas file directly will launch the app and load it automatically
• Update Notifications (desktop app) — Checks GitHub for new releases on startup and shows an in-app banner when an update is available
• PWA Support (web app) — Install as a Progressive Web App for offline use
• Save Modified Atlas — Export updated .atlas, .png, and also copy .skel file if available

Acknowledgments

• Spine Atlas Format — Atlas format specification reference

Contributing

• Found a bug or have a suggestion? Please open an issue
• Pull requests are welcome!

License

This project is licensed under the MIT License — see the LICENSE file for details.

Disclaimer

This project is not affiliated with, endorsed by, or associated with Esoteric Software or the Spine runtime in any way. It was created for educational and personal use only.