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33d1d58 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 | __all__ = ['polygon_clip', 'polygon_area']
import numpy as np
from .version_requirements import require
@require("matplotlib", ">=3.3")
def polygon_clip(rp, cp, r0, c0, r1, c1):
"""Clip a polygon to the given bounding box.
Parameters
----------
rp, cp : (K,) ndarray of double
Row and column coordinates of the polygon.
(r0, c0), (r1, c1) : double
Top-left and bottom-right coordinates of the bounding box.
Returns
-------
r_clipped, c_clipped : (L,) ndarray of double
Coordinates of clipped polygon.
Notes
-----
This makes use of Sutherland-Hodgman clipping as implemented in
AGG 2.4 and exposed in Matplotlib.
"""
from matplotlib import path, transforms
poly = path.Path(np.vstack((rp, cp)).T, closed=True)
clip_rect = transforms.Bbox([[r0, c0], [r1, c1]])
poly_clipped = poly.clip_to_bbox(clip_rect).to_polygons()[0]
return poly_clipped[:, 0], poly_clipped[:, 1]
def polygon_area(pr, pc):
"""Compute the area of a polygon.
Parameters
----------
pr, pc : (K,) array of float
Polygon row and column coordinates.
Returns
-------
a : float
Area of the polygon.
"""
pr = np.asarray(pr)
pc = np.asarray(pc)
return 0.5 * np.abs(np.sum((pc[:-1] * pr[1:]) - (pc[1:] * pr[:-1])))
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