mirror of
https://github.com/wassname/scikit-image.git
synced 2026-06-27 21:08:24 +08:00
Stefan van der Walt
62 lines
1.5 KiB
Python
62 lines
1.5 KiB
Python
"""
|
|
====================
|
|
Local Otsu Threshold
|
|
====================
|
|
|
|
This example shows how Otsu's threshold [1]_ method can be applied locally. For
|
|
each pixel, an "optimal" threshold is determined by maximizing the variance
|
|
between two classes of pixels of the local neighborhood defined by a structuring
|
|
element.
|
|
|
|
The example compares the local threshold with the global threshold.
|
|
|
|
.. note: local is much slower than global thresholding
|
|
|
|
.. [1] http://en.wikipedia.org/wiki/Otsu's_method
|
|
|
|
"""
|
|
import matplotlib
|
|
import matplotlib.pyplot as plt
|
|
|
|
from skimage import data
|
|
from skimage.morphology import disk
|
|
from skimage.filters import threshold_otsu, rank
|
|
from skimage.util import img_as_ubyte
|
|
|
|
|
|
matplotlib.rcParams['font.size'] = 9
|
|
|
|
|
|
img = img_as_ubyte(data.page())
|
|
|
|
radius = 15
|
|
selem = disk(radius)
|
|
|
|
local_otsu = rank.otsu(img, selem)
|
|
threshold_global_otsu = threshold_otsu(img)
|
|
global_otsu = img >= threshold_global_otsu
|
|
|
|
|
|
fig, ax = plt.subplots(2, 2, figsize=(8, 5))
|
|
ax1, ax2, ax3, ax4 = ax.ravel()
|
|
|
|
fig.colorbar(ax1.imshow(img, cmap=plt.cm.gray),
|
|
ax=ax1, orientation='horizontal')
|
|
ax1.set_title('Original')
|
|
ax1.axis('off')
|
|
|
|
fig.colorbar(ax2.imshow(local_otsu, cmap=plt.cm.gray),
|
|
ax=ax2, orientation='horizontal')
|
|
ax2.set_title('Local Otsu (radius=%d)' % radius)
|
|
ax2.axis('off')
|
|
|
|
ax3.imshow(img >= local_otsu, cmap=plt.cm.gray)
|
|
ax3.set_title('Original >= Local Otsu' % threshold_global_otsu)
|
|
ax3.axis('off')
|
|
|
|
ax4.imshow(global_otsu, cmap=plt.cm.gray)
|
|
ax4.set_title('Global Otsu (threshold = %d)' % threshold_global_otsu)
|
|
ax4.axis('off')
|
|
|
|
plt.show()
|