mirror of
https://github.com/wassname/scikit-image.git
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emmanuelle
55f5103dd8
Modified travis_script.sh to account for the new structure of the gallery Added README.txt files in directories of gallery examples Fixed references to gallery images in user guide pages Fixed broken links
62 lines
1.6 KiB
Python
62 lines
1.6 KiB
Python
"""
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====================
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Local Otsu Threshold
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====================
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This example shows how Otsu's threshold [1]_ method can be applied locally. For
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each pixel, an "optimal" threshold is determined by maximizing the variance
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between two classes of pixels of the local neighborhood defined by a
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structuring element.
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The example compares the local threshold with the global threshold.
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.. note: local is much slower than global thresholding
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.. [1] http://en.wikipedia.org/wiki/Otsu's_method
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"""
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import matplotlib
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import matplotlib.pyplot as plt
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from skimage import data
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from skimage.morphology import disk
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from skimage.filters import threshold_otsu, rank
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from skimage.util import img_as_ubyte
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matplotlib.rcParams['font.size'] = 9
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img = img_as_ubyte(data.page())
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radius = 15
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selem = disk(radius)
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local_otsu = rank.otsu(img, selem)
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threshold_global_otsu = threshold_otsu(img)
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global_otsu = img >= threshold_global_otsu
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fig, ax = plt.subplots(2, 2, figsize=(8, 5), sharex=True, sharey=True, subplot_kw={'adjustable':'box-forced'})
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ax1, ax2, ax3, ax4 = ax.ravel()
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fig.colorbar(ax1.imshow(img, cmap=plt.cm.gray),
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ax=ax1, orientation='horizontal')
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ax1.set_title('Original')
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ax1.axis('off')
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fig.colorbar(ax2.imshow(local_otsu, cmap=plt.cm.gray),
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ax=ax2, orientation='horizontal')
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ax2.set_title('Local Otsu (radius=%d)' % radius)
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ax2.axis('off')
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ax3.imshow(img >= local_otsu, cmap=plt.cm.gray)
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ax3.set_title('Original >= Local Otsu' % threshold_global_otsu)
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ax3.axis('off')
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ax4.imshow(global_otsu, cmap=plt.cm.gray)
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ax4.set_title('Global Otsu (threshold = %d)' % threshold_global_otsu)
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ax4.axis('off')
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plt.show()
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