75 lines
2.0 KiB
Python
75 lines
2.0 KiB
Python
"""
|
|
==================
|
|
Hausdorff Distance
|
|
==================
|
|
|
|
This example shows how to calculate the Hausdorff distance between two sets of
|
|
points. The `Hausdorff distance
|
|
<https://en.wikipedia.org/wiki/Hausdorff_distance>`__ is the maximum distance
|
|
between any point on the first set and its nearest point on the second set,
|
|
and vice-versa.
|
|
|
|
"""
|
|
import matplotlib.pyplot as plt
|
|
import numpy as np
|
|
|
|
from skimage import metrics
|
|
|
|
shape = (60, 60)
|
|
image = np.zeros(shape)
|
|
|
|
# Create a diamond-like shape where the four corners form the 1st set of points
|
|
x_diamond = 30
|
|
y_diamond = 30
|
|
r = 10
|
|
|
|
fig, ax = plt.subplots()
|
|
plt_x = [0, 1, 0, -1]
|
|
plt_y = [1, 0, -1, 0]
|
|
|
|
set_ax = [(x_diamond + r * x) for x in plt_x]
|
|
set_ay = [(y_diamond + r * y) for y in plt_y]
|
|
plt.plot(set_ax, set_ay, 'or')
|
|
|
|
# Create a kite-like shape where the four corners form the 2nd set of points
|
|
x_kite = 30
|
|
y_kite = 30
|
|
x_r = 15
|
|
y_r = 20
|
|
|
|
set_bx = [(x_kite + x_r * x) for x in plt_x]
|
|
set_by = [(y_kite + y_r * y) for y in plt_y]
|
|
plt.plot(set_bx, set_by, 'og')
|
|
|
|
# Set up the data to compute the hausdorff distance
|
|
coords_a = np.zeros(shape, dtype=bool)
|
|
coords_b = np.zeros(shape, dtype=bool)
|
|
for x, y in zip(set_ax, set_ay):
|
|
coords_a[(x, y)] = True
|
|
|
|
for x, y in zip(set_bx, set_by):
|
|
coords_b[(x, y)] = True
|
|
|
|
# Call the hausdorff function on the coordinates
|
|
metrics.hausdorff_distance(coords_a, coords_b)
|
|
|
|
# Plot the lines that shows the length of the hausdorff distance
|
|
x_line = [30, 30]
|
|
y_line = [20, 10]
|
|
plt.plot(x_line, y_line, 'y')
|
|
|
|
x_line = [30, 30]
|
|
y_line = [40, 50]
|
|
plt.plot(x_line, y_line, 'y')
|
|
|
|
# Plot circles to show that at this distance, the hausdorff distance can
|
|
# travel to its nearest neighbor (in this case, from the kite to diamond)
|
|
ax.add_artist(plt.Circle((30, 10), 10, color='y', fill=None))
|
|
ax.add_artist(plt.Circle((30, 50), 10, color='y', fill=None))
|
|
ax.add_artist(plt.Circle((15, 30), 10, color='y', fill=None))
|
|
ax.add_artist(plt.Circle((45, 30), 10, color='y', fill=None))
|
|
|
|
ax.imshow(image, cmap=plt.cm.gray)
|
|
ax.axis((0, 60, 60, 0))
|
|
plt.show()
|