Utilities for basic computational geometry directly with numpy arrays.
There are a number of computational geometry libraries available. But most of them create a whole framework of objects: points, polygons, MultiPolygons, etc.
But if you simply need to something simple: e.g. check whether a point is in a polygon, it's nice to have a set of functions to do the basic stuff on numpy arrays, without all the overhead of a full set of geometry objects.
These functions all depend on numpy.
Some of the functions a pure (numpy) python, and some are written in Cython, or C wrapped in Cython.
Most are vectorized, for fast results. e.g. polygon_inside will check whether multiple points are in a single polygon all in C.
This is a start, but it will likely never be very comprehensive.
NOTE: this is all 2D euclidean geometry
Basic polygon manipulation
Some rectangle (bounding box) functionality
The goal is not to have specialized data structures, but to use "normal" numpy arrays (usually float64) to represent geometrical objects.
Most functions will (like numpy itself) take standard Python data structures (such as lists) and convert to numpy arrays as needed (np.asarray()).
Points are represented by a shape: (2,) array (or 2-tuple):
(x, y) of type float64
Multiple points are represented by a shape: (N,2) array: [(x, y), )x,y),...] of type float64 (or equivalent nested list).
Polygons are represented by their vertixes as a shape: (N,2) array: [(x, y), )x,y),...] of type float64
(or equivalent nested list).
(Note that this is exactly the same as multiple points)
Rectangles are axis-aligned rectangles -- suitable for use as bounding boxes, etc.
A rectangle is defined by two points: lower-left, upper-right.
Any python sequence that can be turned into a 2x2 numpy array of float64s:
[[min_x, min_y], [max_x, max_y]]
Determine if points are inside a polygon.
Calculate the area of a polygon
Return a int/bool flag indicating the "winding order" of the polygon
i.e. clockwise or anti-clockwise
Return the (x, y) location of the polygon centroid
Calculate the area of a polygon
This code includes Cython code -- so to work on it, you need Cython and a compiler set up to compile Python extensions. Consult the internet to see how to do that.
ONce your compiler is set up and dependencies in place:
pip install .
Should build and install the package.
NOte that if you do an editable install:
pip isntall -e .
The python code will be editable, but you need to rebuild if you chance the Cython code.
All the dependencies to build and use this package are available on conda-forge.
This package includes a pixi setup to aid in development and building -- see the pixi.toml file.
To use:
pixi run shell
Will get you a pixi shell with the dependencies installed, but not the package. You can then pip install the package.
This is helpful if you are working on the Cython code, so that you can control the install
pixi run -e dev shell
will create a pixi shell with the package built and installed. YOu can then run the tests, change the code, etc.
pixi run build
Will build adn install the package.
pixi run test
will build, and test the package.
pixi run -e py310 test
will build and test the package with python 3.10
py311, py312, py313 are also available.