2.6.8.16. 使用中值滤波器对图像进行降噪

此示例显示了原始图像、噪声图像、降噪后的图像（使用中值滤波器）以及两者之间的差异。

import numpy as np
import scipy as sp
import matplotlib.pyplot as plt

rng = np.random.default_rng(27446968)

im = np.zeros((20, 20))
im[5:-5, 5:-5] = 1
im = sp.ndimage.distance_transform_bf(im)
im_noise = im + 0.2 * rng.normal(size=im.shape)

im_med = sp.ndimage.median_filter(im_noise, 3)

plt.figure(figsize=(16, 5))

plt.subplot(141)
plt.imshow(im, interpolation="nearest")
plt.axis("off")
plt.title("Original image", fontsize=20)
plt.subplot(142)
plt.imshow(im_noise, interpolation="nearest", vmin=0, vmax=5)
plt.axis("off")
plt.title("Noisy image", fontsize=20)
plt.subplot(143)
plt.imshow(im_med, interpolation="nearest", vmin=0, vmax=5)
plt.axis("off")
plt.title("Median filter", fontsize=20)
plt.subplot(144)
plt.imshow(np.abs(im - im_med), cmap="hot", interpolation="nearest")
plt.axis("off")
plt.title("Error", fontsize=20)


plt.subplots_adjust(wspace=0.02, hspace=0.02, top=0.9, bottom=0, left=0, right=1)

plt.show()