Adding gallery example for plotting censure keypoints

doc/examples/plot_censure_keypoints.py

@@ -0,0 +1,46 @@
+"""
+===========================
+Censure Keypoints Detection
+===========================
+
+In this example, we detect and plot the Censure Keypoints at various scales
+using Difference of Boxes, Octagon and Star shaped bi-level filters.
+
+"""
+from skimage.feature import keypoints_censure
+from skimage.data import lena
+from skimage.color import rgb2gray
+import matplotlib.pyplot as plt
+
+# Initializing the parameters for Censure keypoints
+img = lena()
+gray_img = rgb2gray(img)
+min_scale = 1
+max_scale = 7
+nms_threshold = 0.15
+rpc_threshold = 10
+
+
+# Plotting features for the following modes
+for mode in ['dob', 'octagon', 'star']:
+
+    kp_censure, scale = keypoints_censure(gray_img, min_scale, max_scale,
+                                          mode, nms_threshold,rpc_threshold)
+    f, axarr = plt.subplots((max_scale - min_scale + 1) // 3, 3)
+
+    # Plotting Censure features at all the scales
+    for i in range(max_scale - min_scale - 1):
+        keypoints = kp_censure[scale ==  i + min_scale + 1]
+        num = len(keypoints)
+        x = keypoints[:, 1]
+        y = keypoints[:, 0]
+        s = 5 * 2**(i + min_scale + 1)
+        axarr[i // 3, i - (i // 3) * 3].imshow(img)
+        axarr[i // 3, i - (i // 3) * 3].scatter(x, y, s, facecolors='none',
+                                                edgecolors='g')
+        axarr[i // 3, i - (i // 3) * 3].set_title(' %s %s-Censure features at '
+                                                  'scale %d' % (num, mode, i +
+                                                                min_scale + 1))
+
+    plt.suptitle('NMS threshold = %f, RPC threshold = %d' % (nms_threshold, rpc_threshold))
+plt.show()