Merge pull request #874 from emmanuelle/nlm_denoise

FEAT: NL-means denoising

doc/examples/plot_nonlocal_means.py

@@ -0,0 +1,41 @@
+"""
+=================================================
+Non-local means denoising for preserving textures
+=================================================
+
+In this example, we denoise a detail of the astronaut image using the non-local
+means filter. The non-local means algorithm replaces the value of a pixel by an
+average of a selection of other pixels values: small patches centered on the
+other pixels are compared to the patch centered on the pixel of interest, and
+the average is performed only for pixels that have patches close to the current
+patch. As a result, this algorithm can restore well textures, that would be
+blurred by other denoising algoritm.
+"""
+import numpy as np
+import matplotlib.pyplot as plt
+
+from skimage import data, img_as_float
+from skimage.restoration import nl_means_denoising
+
+
+astro = img_as_float(data.astronaut())
+astro = astro[30:180, 150:300]
+
+noisy = astro + 0.3 * np.random.random(astro.shape)
+noisy = np.clip(noisy, 0, 1)
+
+denoise = nl_means_denoising(noisy, 7, 9, 0.08)
+
+fig, ax = plt.subplots(ncols=2, figsize=(8, 4))
+
+ax[0].imshow(noisy)
+ax[0].axis('off')
+ax[0].set_title('noisy')
+ax[1].imshow(denoise)
+ax[1].axis('off')
+ax[1].set_title('non-local means')
+
+fig.subplots_adjust(wspace=0.02, hspace=0.2,
+                    top=0.9, bottom=0.05, left=0, right=1)
+
+plt.show()