Re-enable plots in doc strings and generate PDF images for them

doc/source/conf.py

@@ -246,7 +246,7 @@ matplotlib.rcParams.update({
 
 """
 plot_include_source = True
-plot_formats = [('png', 100)]
+plot_formats = [('png', 100), ('pdf', 100)]
 
 plot2rst_index_name = 'README'
 plot2rst_rcparams = {'image.cmap' : 'gray',

skimage/io/collection.py

@@ -102,6 +102,10 @@ class MultiImage(object):
     (15, 10)
     (15, 10)
 
+    The two frames in this image can be shown with matplotlib:
+
+    .. plot:: show_collection.py
+
     """
     def __init__(self, filename, conserve_memory=True, dtype=None):
         """Load a multi-img."""

skimage/transform/hough_transform.py

@@ -140,6 +140,8 @@ def hough_line(img, theta=None):
 
     >>> out, angles, d = hough(img)
 
+    .. plot:: hough_tf.py
+
     """
     return _hough(img, theta)