rebaseline_server: multithreaded loading/diffing of images

gm/rebaseline_server/imagepairset.py

 #!/usr/bin/python
 
 """
 Copyright 2014 Google Inc.
 
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file.
 
 ImagePairSet class; see its docstring below.
 """
@@ skipping 32 matching lines @@
     """
     Args:
       diff_base_url: base URL indicating where diff images can be loaded from
       descriptions: a (string, string) tuple describing the two image sets.
           If not specified, DEFAULT_DESCRIPTIONS will be used.
     """
     self._column_header_factories = {}
     self._descriptions = descriptions or DEFAULT_DESCRIPTIONS
     self._extra_column_tallies = {}  # maps column_id -> values
                                      #                -> instances_per_value
-    self._image_pair_dicts = []
+    self._image_pairs = []
     self._image_base_url = None
     self._diff_base_url = diff_base_url
 
   def add_image_pair(self, image_pair):
     """Adds an ImagePair; this may be repeated any number of times."""
     # Special handling when we add the first ImagePair...
-    if not self._image_pair_dicts:
+    if not self._image_pairs:
       self._image_base_url = image_pair.base_url
 
     if image_pair.base_url != self._image_base_url:
       raise Exception('added ImagePair with base_url "%s" instead of "%s"' % (
           image_pair.base_url, self._image_base_url))
-    self._image_pair_dicts.append(image_pair.as_dict())
+    self._image_pairs.append(image_pair)
     extra_columns_dict = image_pair.extra_columns_dict
     if extra_columns_dict:
       for column_id, value in extra_columns_dict.iteritems():
         self._add_extra_column_value_to_summary(column_id, value)
 
   def set_column_header_factory(self, column_id, column_header_factory):
     """Overrides the default settings for one of the extraColumn headers.
 
     Args:
       column_id: string; unique ID of this column (must match a key within
@@ skipping 58 matching lines @@
 
   def as_dict(self):
     """Returns a dictionary describing this package of ImagePairs.
 
     Uses the KEY__* constants as keys.
     """
     key_description = KEY__IMAGESETS__FIELD__DESCRIPTION
     key_base_url = KEY__IMAGESETS__FIELD__BASE_URL
     return {
         KEY__EXTRACOLUMNHEADERS: self._column_headers_as_dict(),
-        KEY__IMAGEPAIRS: self._image_pair_dicts,
+        KEY__IMAGEPAIRS: [pair.as_dict() for pair in self._image_pairs],
         KEY__IMAGESETS: {
             KEY__IMAGESETS__SET__IMAGE_A: {
                 key_description: self._descriptions[0],
                 key_base_url: self._image_base_url,
             },
             KEY__IMAGESETS__SET__IMAGE_B: {
                 key_description: self._descriptions[1],
                 key_base_url: self._image_base_url,
             },
             KEY__IMAGESETS__SET__DIFFS: {
                 key_description: 'color difference per channel',
                 key_base_url: posixpath.join(
                     self._diff_base_url, 'diffs'),
             },
             KEY__IMAGESETS__SET__WHITEDIFFS: {
                 key_description: 'differing pixels in white',
                 key_base_url: posixpath.join(
                     self._diff_base_url, 'whitediffs'),
             },
         },
     }