Fix inconsistencies in examples and many more improvements

doc/examples/plot_corner.py

@@ -10,7 +10,6 @@ position of corners.
 .. [2] http://en.wikipedia.org/wiki/Interest_point_detection
 
 """
-
 from matplotlib import pyplot as plt
 
 from skimage import data
@@ -18,6 +17,7 @@ from skimage.feature import corner_harris, corner_subpix, corner_peaks
 from skimage.transform import warp, AffineTransform
 from skimage.draw import ellipse
 
+
 tform = AffineTransform(scale=(1.3, 1.1), rotation=1, shear=0.7,
                         translation=(210, 50))
 image = warp(data.checkerboard(), tform.inverse, output_shape=(350, 350))