| __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]))) |
|
|
