Use cv2 to replace scipy.misc (fix #592) (#667)

* Converted scipy.misc to cv2

Scipy.misc is being deprecated so we should probably switch to OpenCV to reduce the number of needed dependencies.

* Removed unused import.

* Made Travis happy

* Travis fix

* Added cv2 dummy func and remove grayscale hack

tensorpack/tfutils/summary.py

@@ -5,7 +5,6 @@
 import six
 import tensorflow as tf
 import re
-import io
 from six.moves import range
 from contextlib import contextmanager
 
@@ -71,20 +70,25 @@ def create_image_summary(name, val):
     s = tf.Summary()
     for k in range(n):
         arr = val[k]
-        if arr.shape[2] == 1:   # scipy doesn't accept (h,w,1)
-            arr = arr[:, :, 0]
+        #CV2 will only write correctly in BGR chanel order
+        if c == 3:
+            arr = cv2.cvtColor(arr, cv2.COLOR_RGB2BGR)
+        elif c == 4:
+            arr = cv2.cvtColor(arr, cv2.COLOR_RGBA2BGRA)
         tag = name if n == 1 else '{}/{}'.format(name, k)
 
-        buf = io.BytesIO()
-        # scipy assumes RGB
-        scipy.misc.toimage(arr).save(buf, format='png')
+        retval, img_str = cv2.imencode('.png', arr)
+        if not retval:
+            # Encoding has failed.
+            continue
+        img_str = img_str.tostring()
 
         img = tf.Summary.Image()
         img.height = h
         img.width = w
         # 1 - grayscale 3 - RGB 4 - RGBA
         img.colorspace = c
-        img.encoded_image_string = buf.getvalue()
+        img.encoded_image_string = img_str
         s.value.add(tag=tag, image=img)
     return s
 
@@ -261,7 +265,7 @@ def add_moving_summary(*args, **kwargs):
 
 
 try:
-    import scipy.misc
+    import cv2
 except ImportError:
     from ..utils.develop import create_dummy_func
-    create_image_summary = create_dummy_func('create_image_summary', 'scipy.misc')  # noqa
+    create_image_summary = create_dummy_func('create_image_summary', 'cv2')  # noqa