restored old otsu threshold example script

doc/examples/plot_otsu.py

@@ -0,0 +1,45 @@
+"""
+============
+Thresholding
+============
+
+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 (marked by a red line in the
+histogram below) by maximizing the variance between two classes of pixels,
+which are separated by the threshold. Equivalently, this threshold minimizes
+the intra-class variance.
+
+.. [1] http://en.wikipedia.org/wiki/Otsu's_method
+
+"""
+
+import matplotlib.pyplot as plt
+
+from skimage.data import camera
+from skimage.filter import threshold_otsu
+
+
+image = camera()
+thresh = threshold_otsu(image)
+binary = image > thresh
+
+plt.figure(figsize=(8, 2.5))
+plt.subplot(1, 3, 1)
+plt.imshow(image, cmap=plt.cm.gray)
+plt.title('Original')
+plt.axis('off')
+
+plt.subplot(1, 3, 2, aspect='equal')
+plt.hist(image)
+plt.title('Histogram')
+plt.axvline(thresh, color='r')
+
+plt.subplot(1, 3, 3)
+plt.imshow(binary, cmap=plt.cm.gray)
+plt.title('Thresholded')
+plt.axis('off')
+
+plt.show()
+