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https://github.com/fitnr/visvalingamwyatt
Python simplication of geodata
https://github.com/fitnr/visvalingamwyatt
Last synced: 17 days ago
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Python simplication of geodata
- Host: GitHub
- URL: https://github.com/fitnr/visvalingamwyatt
- Owner: fitnr
- License: mit
- Created: 2016-01-21T04:27:55.000Z (almost 9 years ago)
- Default Branch: master
- Last Pushed: 2024-04-14T11:55:47.000Z (7 months ago)
- Last Synced: 2024-10-13T22:30:55.114Z (about 1 month ago)
- Language: Python
- Size: 54.7 KB
- Stars: 42
- Watchers: 3
- Forks: 11
- Open Issues: 3
-
Metadata Files:
- Readme: README.md
- License: LICENSE.txt
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README
# Visvalingam-Wyatt
A Python implementation of the Visvalingam-Wyatt line simplification algorithm.
This implementation is due to [Eliot Hallmark](https://github.com/Permafacture/Py-Visvalingam-Whyatt/). This release simply packages it as a Python module.
## Use
```python
>>> import visvalingamwyatt as vw
>>> points = [(1, 2), (2, 3), (3, 4), ...]
>>> vw.simplify(points)
[(1, 2), (3, 4), ...]
```
Points may be any `Sequence`-like object that (`list`, `tuple`, a custom class that exposes an `__iter__` method).
Test different methods and thresholds:
```python
simplifier = vw.Simplifier(points)
# Simplify by percentage of points to keep
simplifier.simplify(ratio=0.5)
# Simplify by giving number of points to keep
simplifier.simplify(number=1000)
# Simplify by giving an area threshold (in the units of the data)
simplifier.simplify(threshold=0.01)
```
Shorthands for working with geodata:
````python
import visvalingamwyatt as vw
feature = {
"properties": {"foo": "bar"},
"geometry": {
"type": "Polygon",
"coordinates": [...]
}
}
# returns a copy of the geometry, simplified (keeping 90% of points)
vw.simplify_geometry(feature['geometry'], ratio=0.90)
# returns a copy of the feature, simplified (using an area threshold)
vw.simplify_feature(feature, threshold=0.90)
````
The command line tool `vwsimplify` is available to simplify GeoJSON files:
````
# Simplify using a ratio of points
vwsimplify --ratio 0.90 in.geojson -o simple.geojson
# Simplify using the number of points to keep
vwsimplify --number 1000 in.geojson -o simple.geojson
# Simplify using a minimum area
vwsimplify --threshold 0.001 in.geojson -o simple.geojson
````
Install [Fiona](https://github.com/Toblerity/Fiona) for the additional ability to simplify any geodata layer.
## License
MIT