https://github.com/urschrei/rdp

A library providing FFI access to fast Ramer–Douglas–Peucker and Visvalingam-Whyatt line simplification algorithms
https://github.com/urschrei/rdp

computational-geometry ffi geo geospatial rdp rust-library visvalingam

Last synced: about 1 year ago
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A library providing FFI access to fast Ramer–Douglas–Peucker and Visvalingam-Whyatt line simplification algorithms

• Host: GitHub
• URL: https://github.com/urschrei/rdp
• Owner: urschrei
• License: mit
• Created: 2016-08-03T16:20:05.000Z (almost 10 years ago)
• Default Branch: master
• Last Pushed: 2024-05-04T21:10:38.000Z (about 2 years ago)
• Last Synced: 2025-03-26T02:51:12.356Z (over 1 year ago)
• Topics: computational-geometry, ffi, geo, geospatial, rdp, rust-library, visvalingam
• Language: Rust
• Homepage: https://docs.rs/rdp
• Size: 5.81 MB
• Stars: 24
• Watchers: 2
• Forks: 3
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • License: license.txt

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# RDP

A Rust implementation of the [Ramer–Douglas-Peucker](https://en.wikipedia.org/wiki/Ramer–Douglas–Peucker_algorithm) and [Visvalingam-Whyatt](https://bost.ocks.org/mike/simplify/) line simplification algorithms.

**The algorithms underlying this crate have now migrated to [rust-geo](https://github.com/georust/rust-geo) as the [`Simplify`](https://docs.rs/geo/*/geo/algorithm/simplify/index.html) and [`SimplifyVW`](https://docs.rs/geo/*/geo/algorithm/simplifyvw/index.html) traits.**

# FFI

The shared library exposes a(n) FFI: https://docs.rs/rdp/latest/rdp/#functions.  

Some examples are available in [this Jupyter notebook](examples.ipynb).  

[**Simplification**](https://pypi.python.org/pypi/simplification/), a Python package which uses this shared library, is available from PyPi.

### Example Implementation

A Python 2.7 / 3.5 / 3.6 implementation can be found at [`ffi.py`](ffi.py

)  

Run `cargo build --release`, then `python ffi.py` to test. It's also importable, exposing `simplify_linestring()` – call it with a coordinate list and a precision parameter. Allocated memory is dropped on exit.  

# Performance & Complexity

On an 841-point LineString, RDP runs around 3.5x faster than VW. However, RDP's worst-case time complexity is O(*n*2) – This implementation doesn't use the Convex Hull Speedup, see [Hershberger & Snoeyink](http://dl.acm.org/citation.cfm?id=902273), 1992 – whereas the VW implementation uses a min-heap, and thus has worst-case time-complexity of O(*n* log(*n*)), which may make it a better choice for larger LineStrings under certain conditions; RDP has an *average* time complexity of O(*n* log(*n*)), but LineStrings such as the one seen [here](http://stackoverflow.com/a/31566048/416626) will slow it down significantly.

You can verify these times for yourself by running `cargo bench`.

# License

[MIT](license.txt)

# References

**Douglas, D.H.**, **Peucker, T.K.**, 1973. *Algorithms for the reduction of the number of points required to represent a digitized line or its caricature*. Cartographica: The International Journal for Geographic Information and Geovisualization 10, 112–122. [DOI](http://dx.doi.org/10.3138/FM57-6770-U75U-7727)

**Ramer, U.**, 1972. *An iterative procedure for the polygonal approximation of plane curves*. Computer Graphics and Image Processing 1, 244–256. [DOI](http://dx.doi.org/10.1016/S0146-664X(72)80017-0)

**Visvalingam, M.**, **Whyatt, J.D.**, 1993. *Line generalisation by repeated elimination of points*. The Cartographic Journal 30, 46–51. [DOI](http://dx.doi.org/10.1179/000870493786962263)