Addition of examples in the harris and peak local max function

doc/examples/plot_peak_local_max.py

@@ -0,0 +1,55 @@
+"""
+===============================================================================
+Peak local maximum
+===============================================================================
+
+The peak local maximum return coordinates of peaks in a image. The maximum
+filter is used for finding the maximum peaks in the image. It dilates the 
+original image and is used within peak local max function to find the 
+coordinates of maximum peaks, comparing the dilated image with the original. 
+Then, the peak local max function returns the coordinates of points where 
+image = dilated image. 
+
+"""
+from scipy import ndimage
+import matplotlib.pyplot as plt
+import numpy as np
+from skimage.feature import peak_local_max
+from skimage import data, img_as_float
+
+im = img_as_float(data.coins())
+image = im.copy()
+
+# The image_max is the dilation of im with a 20*20 structuring element
+# It is used within peak_local_max function 
+image_max = ndimage.maximum_filter(image, size=20, mode='constant')
+
+# Comparison between image_max and im to find the coordinates of maximum peaks
+coordinates = peak_local_max(im, min_distance = 20)
+
+# display results
+plt.figure(figsize=(8, 3))
+plt.subplot(131)
+plt.imshow(im, cmap=plt.cm.gray)
+plt.axis('off')
+plt.title('Original')
+
+plt.subplot(132)
+plt.imshow(image_max, cmap=plt.cm.gray)
+plt.axis('off')
+plt.title('Maximum filter')
+
+plt.subplot(133)
+plt.imshow(im, cmap=plt.cm.gray)
+a, b = im.shape
+plt.plot([p[1] for p in coordinates],[p[0] for p in coordinates],'r.')
+plt.xlim(0,b)
+plt.ylim(a,0)
+plt.axis('off')
+plt.title('Peak local max')
+
+plt.subplots_adjust(wspace=0.02, hspace=0.02, top=0.9,
+                    bottom=0.02, left=0.02, right=0.98)
+
+plt.show()
+