testbed/matplotlib__matplotlib/galleries/examples/misc/bbox_intersect.py

"""
===========================================
Changing colors of lines intersecting a box
===========================================

The lines intersecting the rectangle are colored in red, while the others
are left as blue lines. This example showcases the `.intersects_bbox` function.

"""

import matplotlib.pyplot as plt
import numpy as np

from matplotlib.path import Path
from matplotlib.transforms import Bbox

# Fixing random state for reproducibility
np.random.seed(19680801)


left, bottom, width, height = (-1, -1, 2, 2)
rect = plt.Rectangle((left, bottom), width, height,
                     facecolor="black", alpha=0.1)

fig, ax = plt.subplots()
ax.add_patch(rect)

bbox = Bbox.from_bounds(left, bottom, width, height)

for i in range(12):
    vertices = (np.random.random((2, 2)) - 0.5) * 6.0
    path = Path(vertices)
    if path.intersects_bbox(bbox):
        color = 'r'
    else:
        color = 'b'
    ax.plot(vertices[:, 0], vertices[:, 1], color=color)

plt.show()