Enhance image.py for gray image.

Author: qingqing01

python/paddle/v2/image.py

@@ -176,7 +176,6 @@ def resize_short(im, size):
     :param size: the shorter edge size of image after resizing.
     :type size: int
     """
-    assert im.shape[-1] == 1 or im.shape[-1] == 3
     h, w = im.shape[:2]
     h_new, w_new = size, size
     if h > w:
@@ -267,7 +266,7 @@ def random_crop(im, size, is_color=True):
     return im
 
 
-def left_right_flip(im):
+def left_right_flip(im, is_color=True):
     """
     Flip an image along the horizontal direction.
     Return the flipped image.
@@ -278,13 +277,16 @@ def left_right_flip(im):
 
         im = left_right_flip(im)
     
-    :paam im: input image with HWC layout
+    :paam im: input image with HWC layout or HW layout for gray image
+
     :type im: ndarray
+    :paam is_color: whether color input image or not
+    :type is_color: bool
     """
-    if len(im.shape) == 3:
+    if len(im.shape) == 3 and is_color:
         return im[:, ::-1, :]
     else:
-        return im[:, ::-1, :]
+        return im[:, ::-1]
 
 
 def simple_transform(im,
@@ -319,20 +321,22 @@ def simple_transform(im,
     """
     im = resize_short(im, resize_size)
     if is_train:
-        im = random_crop(im, crop_size)
+        im = random_crop(im, crop_size, is_color)
         if np.random.randint(2) == 0:
-            im = left_right_flip(im)
+            im = left_right_flip(im, is_color)
     else:
-        im = center_crop(im, crop_size)
+        im = center_crop(im, crop_size, is_color)
     if len(im.shape) == 3:
         im = to_chw(im)
 
     im = im.astype('float32')
     if mean is not None:
         mean = np.array(mean, dtype=np.float32)
         # mean value, may be one value per channel 
-        if mean.ndim == 1:
+        if mean.ndim == 1 and is_color:
             mean = mean[:, np.newaxis, np.newaxis]
+        elif mean.ndim == 1:
+            mean = mean
         else:
             # elementwise mean
             assert len(mean.shape) == len(im)
@@ -372,6 +376,6 @@ def load_and_transform(filename,
                  mean values per channel.
     :type mean: numpy array | list
     """
-    im = load_image(filename)
+    im = load_image(filename, is_color)
     im = simple_transform(im, resize_size, crop_size, is_train, is_color, mean)
     return im