rebaseline_server: add ImagePair class, a step towards new intermediate JSON schema

gm/rebaseline_server/imagepair.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.
+
+ImagePair class (see class docstring for details)
+"""
+
+import posixpath
+
+# Keys used within ImagePair dictionary representations.
+KEY_DIFFERENCE_DATA = 'differenceData'
+KEY_EXPECTATIONS_DATA = 'expectationsData'
+KEY_EXTRA_COLUMN_VALUES = 'extraColumnValues'
+KEY_IMAGE_A_URL = 'imageAUrl'
+KEY_IMAGE_B_URL = 'imageBUrl'
+KEY_IS_DIFFERENT = 'isDifferent'
+
+
+class ImagePair(object):
+  """
+  Describes a pair of images, along with optional metadata (pixel difference
+  metrics, whether to ignore mismatches, etc.)
+  """
+
+  def __init__(self, image_diff_db,
+               base_url, imageA_relative_url, imageB_relative_url,
+               expectations=None, extra_columns=None):
+    """
+    Args:
+      image_diff_db: ImageDiffDB instance we use to generate/store image diffs
+      base_url: base of all image URLs
+      imageA_relative_url: URL pointing at an image, relative to base_url
+      imageB_relative_url: URL pointing at an image, relative to base_url
+      expectations: optional dictionary containing expectations-specific
+          metadata (ignore-failure, bug numbers, etc.)
+      extra_columns: optional dictionary containing more metadata (test name,
+          builder name, etc.)
+    """
+    self.base_url = base_url
+    self.imageA_relative_url = imageA_relative_url
+    self.imageB_relative_url = imageB_relative_url
+    self.expectations_dict = expectations
+    self.extra_columns_dict = extra_columns
+    if imageA_relative_url == imageB_relative_url:
+      self.diff_record = None
+    else:
+      # TODO(epoger): Rather than blocking until image_diff_db can read in
+      # the image pair and generate diffs, it would be better to do it
+      # asynchronously: tell image_diff_db to download a bunch of file pairs,
+      # and only block later if we're still waiting for diff_records to come
+      # back.
+      image_diff_db.add_image_pair(
+          expected_image_locator=imageA_relative_url,
+          expected_image_url=posixpath.join(base_url, imageA_relative_url),
+          actual_image_locator=imageB_relative_url,
+          actual_image_url=posixpath.join(base_url, imageB_relative_url))
+      self.diff_record = image_diff_db.get_diff_record(
+          expected_image_locator=imageA_relative_url,
+          actual_image_locator=imageB_relative_url)
+
+  def as_dict(self):
+    """
+    Return a dictionary describing this ImagePair, as needed when constructing
+    the JSON representation.  Uses the KEY_* constants as keys.
+    """
+    asdict = {
+        KEY_IMAGE_A_URL: self.imageA_relative_url,
+        KEY_IMAGE_B_URL: self.imageB_relative_url,
+    }
+    if self.expectations_dict:
+      asdict[KEY_EXPECTATIONS_DATA] = self.expectations_dict
+    if self.extra_columns_dict:
+      asdict[KEY_EXTRA_COLUMN_VALUES] = self.extra_columns_dict
+    if self.diff_record and (self.diff_record.get_num_pixels_differing() > 0):
+      asdict[KEY_IS_DIFFERENT] = True
+      asdict[KEY_DIFFERENCE_DATA] = self.diff_record.as_dict()
+    else:
+      asdict[KEY_IS_DIFFERENT] = False
+    return asdict