tools/site_compare/operators/equals_with_mask.py

   1 # Copyright (c) 2011 The Chromium Authors. All rights reserved.
   2 # Use of this source code is governed by a BSD-style license that can be
   3 # found in the LICENSE file.
   4
   5 """Compare two images for equality, subject to a mask."""
   6
   7 from PIL import Image
   8 from PIL import ImageChops
   9
  10 import os.path
  11
  12
  13 def Compare(file1, file2, **kwargs):
  14   """Compares two images to see if they're identical subject to a mask.
  15
  16   An optional directory containing masks is supplied. If a mask exists
  17   which matches file1's name, areas under the mask where it's black
  18   are ignored.
  19
  20   Args:
  21     file1: path to first image to compare
  22     file2: path to second image to compare
  23     kwargs: ["maskdir"] contains the directory holding the masks
  24
  25   Returns:
  26     None if the images are identical
  27     A tuple of (errorstring, image) if they're not
  28   """
  29
  30   maskdir = None
  31   if "maskdir" in kwargs:
  32     maskdir = kwargs["maskdir"]
  33
  34   im1 = Image.open(file1)
  35   im2 = Image.open(file2)
  36
  37   if im1.size != im2.size:
  38     return ("The images are of different size (%r vs %r)" %
  39             (im1.size, im2.size), im1)
  40
  41   diff = ImageChops.difference(im1, im2)
  42
  43   if maskdir:
  44     maskfile = os.path.join(maskdir, os.path.basename(file1))
  45     if os.path.exists(maskfile):
  46       mask = Image.open(maskfile)
  47
  48       if mask.size != im1.size:
  49         return ("The mask is of a different size than the images (%r vs %r)" %
  50                 (mask.size, im1.size), mask)
  51
  52       diff = ImageChops.multiply(diff, mask.convert(diff.mode))
  53
  54   if max(diff.getextrema()) != (0, 0):
  55     return ("The images differ", diff)
  56   else:
  57     return None