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diff --git a/tools/site_compare/operators/equals.py b/tools/site_compare/operators/equals.py
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+#!/usr/bin/python2.4
+# Copyright 2008, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#    * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#    * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#    * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Compare two images for equality."""
+
+from PIL import Image
+from PIL import ImageChops
+
+
+def Compare(file1, file2, **kwargs):
+  """Compares two images to see if they're identical.
+  
+  Args:
+    file1: path to first image to compare
+    file2: path to second image to compare
+    kwargs: unused for this operator
+    
+  Returns:
+    None if the images are identical
+    A tuple of (errorstring, image) if they're not
+  """
+  kwargs = kwargs  # unused parameter
+  
+  im1 = Image.open(file1)
+  im2 = Image.open(file2)
+  
+  if im1.size != im2.size:
+    return ("The images are of different size (%s vs %s)" %
+            (im1.size, im2.size), im1)
+
+  diff = ImageChops.difference(im1, im2)
+  
+  if max(diff.getextrema()) != (0, 0):
+    return ("The images differ", diff)
+  else:
+    return None
+  
+  
+  
+\ No newline at end of file