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 58
