image decompress timer (#2596)

* image decompress timer

* dont lazy load the image

ml-agents-envs/mlagents/envs/brain.py

 from mlagents.envs.communicator_objects.brain_parameters_proto_pb2 import (
     BrainParametersProto,
 )
+from mlagents.envs.timers import hierarchical_timer, timed
 from typing import Dict, List, Optional
 from PIL import Image
 
         return np.append(m1, m2, axis=0)
 
     @staticmethod
+    @timed
     def process_pixels(image_bytes: bytes, gray_scale: bool) -> np.ndarray:
         """
         Converts byte array observation image into numpy array, re-sizes it,
         :return: processed numpy array of observation from environment
         """
-        image_bytearray = bytearray(image_bytes)
-        image = Image.open(io.BytesIO(image_bytearray))
+        with hierarchical_timer("image_decompress"):
+            image_bytearray = bytearray(image_bytes)
+            image = Image.open(io.BytesIO(image_bytearray))
+            # Normally Image loads lazily, this forces it to do loading in the timer scope.
+            image.load()
         s = np.array(image) / 255.0
         if gray_scale:
             s = np.mean(s, axis=2)