58 lines
1.6 KiB
Python
58 lines
1.6 KiB
Python
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# Copyright (c) 2011 The Chromium Authors. All rights reserved.
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# Use of this source code is governed by a BSD-style license that can be
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# found in the LICENSE file.
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"""Compare two images for equality, subject to a mask."""
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from PIL import Image
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from PIL import ImageChops
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import os.path
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def Compare(file1, file2, **kwargs):
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"""Compares two images to see if they're identical subject to a mask.
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An optional directory containing masks is supplied. If a mask exists
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which matches file1's name, areas under the mask where it's black
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are ignored.
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Args:
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file1: path to first image to compare
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file2: path to second image to compare
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kwargs: ["maskdir"] contains the directory holding the masks
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Returns:
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None if the images are identical
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A tuple of (errorstring, image) if they're not
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"""
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maskdir = None
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if "maskdir" in kwargs:
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maskdir = kwargs["maskdir"]
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im1 = Image.open(file1)
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im2 = Image.open(file2)
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if im1.size != im2.size:
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return ("The images are of different size (%r vs %r)" %
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(im1.size, im2.size), im1)
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diff = ImageChops.difference(im1, im2)
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if maskdir:
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maskfile = os.path.join(maskdir, os.path.basename(file1))
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if os.path.exists(maskfile):
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mask = Image.open(maskfile)
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if mask.size != im1.size:
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return ("The mask is of a different size than the images (%r vs %r)" %
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(mask.size, im1.size), mask)
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diff = ImageChops.multiply(diff, mask.convert(diff.mode))
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if max(diff.getextrema()) != (0, 0):
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return ("The images differ", diff)
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else:
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return None
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