feat(edt): add GPU-accelerated exact Euclidean Distance Transform using PBA+ algorithm

[aymuos15]

I am working on a project where I would really benefit from this. Would it be possible to give this a review @tvercaut @masadcv

I do not have much experience in this space, so relying on AI a tiny bit for this one. I verified everything personally to the best of my abilities. Please do let me know if I missed anything.

Should close #49

[masadcv]

Hi @aymuos15
Many thanks for this, apologies for long delay.
I will review this soon and get back to you

[Copilot]

Pull request overview

Adds a GPU implementation of an (intended) exact Euclidean Distance Transform (EDT) to FastGeodis using the PBA+ algorithm, along with Python bindings, tests, and docs/benchmarks to support the new API.

Changes:

• Add CUDA/C++ implementation for exact (and signed) EDT in 2D/3D and expose it via pybind + Python API.
• Add unit tests for the new EDT functions (including SciPy comparisons) and utility helpers for selecting the new functions.
• Update README and add benchmark script + benchmark artifacts; add DISABLE_CUDA build flag.

Reviewed changes

Copilot reviewed 12 out of 16 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
FastGeodis/geodis_pba.cu	CUDA implementation of PBA+ EDT (2D + 3D) and signed EDT helpers
FastGeodis/geodis_pba.h	CUDA function declarations for PBA+ EDT
FastGeodis/fastgeodis.h	Public C++ API declarations for exact/signed exact EDT
FastGeodis/fastgeodis.cpp	C++ entrypoints + pybind registrations for exact/signed exact EDT
FastGeodis/__init__.py	Python-facing API + docstrings for exact/signed exact EDT
tests/test_pba.py	New test suite for exact/signed exact EDT (incl. SciPy comparison)
tests/utils.py	Adds function selectors/wrappers for the new EDT APIs
setup.py	Adds DISABLE_CUDA env flag to force CPU-only builds
samples/test_speed_benchmark_pba.py	Benchmark script comparing SciPy vs raster vs PBA+
README.md	Documents new PBA+ exact EDT APIs + adds reference [12]
figures/*pba*	Benchmark outputs (plots + JSON timings/errors)

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.