import numpy as np
from scipy import ndimage
import matplotlib.pyplot as plt


x = np.zeros((30, 30))

x[10, 10] = 1
x[20, 10] = 1
x[10, 20] = 1
x[20, 20] = 1

label, num = ndimage.label(x)

plt.figure(figsize=(8, 5))
plt.suptitle(f"`ndimage.label` return [{num}] features\nIgnoring background.")
im = plt.subplot(121).imshow(x, cmap='gray')
plt.axis('off')
plt.colorbar(im)
plt.title('input')
im = plt.subplot(122).imshow(label, cmap='rainbow')
plt.axis('off')
plt.colorbar(im)
plt.title('label')
plt.tight_layout()
plt.show()