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Tony S Yu
46 lines
997 B
Python
46 lines
997 B
Python
"""
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============
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Thresholding
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============
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Thresholding is used to create a binary image. This example uses Otsu's method
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to calculate the threshold value.
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Otsu's method calculates an "optimal" threshold (marked by a red line in the
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histogram below) by maximizing the variance between two classes of pixels,
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which are separated by the threshold. Equivalently, this threshold minimizes
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the intra-class variance.
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.. [1] http://en.wikipedia.org/wiki/Otsu's_method
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"""
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import matplotlib.pyplot as plt
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from skimage.data import camera
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from skimage.filter import threshold_otsu
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image = camera()
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thresh = threshold_otsu(image)
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binary = image > thresh
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plt.figure(figsize=(8, 2.5))
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plt.subplot(1, 3, 1)
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plt.imshow(image, cmap=plt.cm.gray)
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plt.title('Original')
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plt.axis('off')
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plt.subplot(1, 3, 2, aspect='equal')
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plt.hist(image)
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plt.title('Histogram')
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plt.axvline(thresh, color='r')
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plt.subplot(1, 3, 3)
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plt.imshow(binary, cmap=plt.cm.gray)
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plt.title('Thresholded')
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plt.axis('off')
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plt.show()
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