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Improve thresholding example

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Tony S Yu
2011-12-18 09:31:10 -05:00
parent 8ed834a3ab
commit 1e12ca0044
1 changed files with 23 additions and 2 deletions
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doc/examples/plot_otsu.py
+23 -2
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@@ -3,7 +3,14 @@
Thresholding
============
Thresholding is used to create a binary image. This example uses Otsu's method to calculate the threshold value.
Thresholding is used to create a binary image. This example uses Otsu's method
to calculate the threshold value.
Otsu's method calculates an "optimal" threshold by maximizing the variance
between the two classes of pixels, which are separated by the threshold.
Equivalently, the optimal threshold minimizes the intra-class variance.
.. [1] http://en.wikipedia.org/wiki/Otsu's_method
"""
@@ -17,7 +24,21 @@ image = camera()
thresh = threshold_otsu(image)
binary = image > thresh
plt.imshow(binary)
plt.figure(figsize=(10, 3.5))
plt.subplot(1, 3, 1)
plt.imshow(image)
plt.title('original')
plt.axis('off')
plt.subplot(1, 3, 2)
plt.hist(image)
plt.title('histogram')
plt.axvline(thresh, color='r')
plt.subplot(1, 3, 3)
plt.imshow(binary)
plt.title('thresholded')
plt.axis('off')
plt.show()