Fix and improve example

doc/source/plots/hough_tf.py

@@ -2,13 +2,14 @@ import numpy as np
 import matplotlib.pyplot as plt
 
 from skimage.transform import hough_line
+from skimage.draw import line
 
 img = np.zeros((100, 150), dtype=bool)
 img[30, :] = 1
 img[:, 65] = 1
 img[35:45, 35:50] = 1
-for i in range(90):
-    img[i, i] = 1
+rr, cc = line(60, 130, 80, 10)
+img[rr, cc] = 1
 img += np.random.random(img.shape) > 0.95
 
 out, angles, d = hough_line(img)
@@ -20,8 +21,8 @@ plt.title('Input image')
 
 plt.subplot(1, 2, 2)
 plt.imshow(out, cmap=plt.cm.bone,
-           extent=(np.rad2deg(angles[0]), np.rad2deg(angles[-1]),
-                   d[0], d[-1]))
+           extent=(np.rad2deg(angles[-1]), np.rad2deg(angles[0]),
+                   d[-1], d[0]))
 plt.title('Hough transform')
 plt.xlabel('Angle (degree)')
 plt.ylabel('Distance (pixel)')