Flattener

Open-source SOTA document scanner.

Turn document photos and open books into flat, upright scans. Flattener detects pages, corrects orientation and curvature, and splits book spreads. Everything runs locally. Inference, training, data preparation and evaluation code are included.

See benchmark results and reproduction instructions.

Scan

uvx flattener-scan -i photo.jpg scan.jpg

Or install it with pip install flattener-scan and run flattener-scan -i photo.jpg scan.jpg. Flattener needs Python 3.12 or newer and is tested on Linux x86_64.

The models run on the CPU with ONNX Runtime, so the install stays small. To use an NVIDIA GPU, add PyTorch: uvx --with torch flattener-scan -i photo.jpg scan.jpg, or pip install "flattener-scan[torch]". With PyTorch installed, a CUDA GPU is used automatically; --device cpu or --backend onnx keeps the CPU.

The first scan downloads the Apache-2.0 models from Hugging Face, version 1.1.0. Later scans reuse the local Hugging Face cache and work offline. Set HF_HOME to choose a different cache directory.

Without an output name, the scan is saved as photo-scan.jpg in the current directory. Repeat -i for a batch and give an output directory: flattener-scan -i a.jpg -i b.jpg scans/. Book spreads produce separate page files, such as scan-p1.jpg and scan-p2.jpg. Existing files are kept unless you pass -y. Use --record to save a JSON record of each scan, or --json to print one. Use --region, --quad, --quarter or --output-size for manual control; run flattener-scan --help for all options.

From Python:

from flattener.scan.io import save_scan_files
from flattener.scan.pipeline import Scanner

scanner = Scanner.load()
result = scanner.scan("photo.jpg")
save_scan_files(result, "scan.jpg")

Use scanner.scan_pages("book.jpg") for automatic spread splitting.

To work from a clone of this repository, run uv sync and uv run flattener-scan. The development environment includes CPU PyTorch for training and evaluation.

Browser app

Scan single pages locally with WebGPU or CPU/WASM, edit the result and save a PNG. See the web app guide for setup, capabilities and static hosting.

Training

All three scanner models are trained from scratch on redistributable data.

• Dewarp
• Page detection
• Orientation

Run the Python tests with uv run pytest -q.

License

Project code is Apache-2.0.