add docs for grayscale + random grayscale transforms (#333)

* add docs for grayscale + random grayscale transforms

docs/source/transforms.rst

@@ -26,6 +26,10 @@ Transforms on PIL Image
 
 .. autoclass:: RandomSizedCrop
 
+.. autoclass:: Grayscale
+
+.. autoclass:: RandomGrayscale
+
 .. autoclass:: FiveCrop
 
 .. autoclass:: TenCrop

torchvision/transforms/transforms.py

@@ -633,13 +633,14 @@ class RandomRotation(object):
 
 class Grayscale(object):
     """Convert image to grayscale.
+
     Args:
         num_output_channels (int): (1 or 3) number of channels desired for output image
 
     Returns:
-        PIL Image: grayscale version of the input
-                   if num_output_channels == 1 : returned image is single channel
-                   if num_output_channels == 3 : returned image is 3 channel with r == g == b
+        PIL Image: Grayscale version of the input.
+        - If num_output_channels == 1 : returned image is single channel
+        - If num_output_channels == 3 : returned image is 3 channel with r == g == b
 
     """
 
@@ -659,16 +660,15 @@ class Grayscale(object):
 
 class RandomGrayscale(object):
     """Randomly convert image to grayscale with a probability of p (default 0.1).
+
     Args:
         p (float): probability that image should be converted to grayscale.
 
     Returns:
-        PIL Image: grayscale version of the input image with probability p
-                   and unchanged with probability (1-p)
-                   - if input image is 1 channel:
-                        grayscale version is 1 channel
-                   - if input image is 3 channel:
-                        grayscale version is 3 channel with r == g == b
+        PIL Image: Grayscale version of the input image with probability p and unchanged
+        with probability (1-p).
+        - If input image is 1 channel: grayscale version is 1 channel
+        - If input image is 3 channel: grayscale version is 3 channel with r == g == b
 
     """