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1# Copyright (c) 2014 The Chromium OS 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
5import logging
6import os
7
8from autotest_lib.client.cros.video import method_logger
9from autotest_lib.client.common_lib import error
10
11
12class Verifier(object):
13    """
14    Verifies that received screenshots are same as expected.
15
16    This class relies on a provided image comparer to decide if two images are
17    one and the same.
18
19    Clients who have many images to compare should use this class and pass in
20    a comparer of their choice.
21
22    Comparer are just about comparing two images and this class takes over with
23    test-related things: logging, deciding pass or fail.
24
25    """
26
27
28    @method_logger.log
29    def __init__(self, image_comparer, stop_on_first_failure, threshold=0,
30                 box=None):
31        """
32        @param image_comparer: object, image comparer to use.
33        @param stop_on_first_failure: bool, true if the test should be stopped
34                                      once a test image doesn't match its ref.
35        @param threshold: int, a value which the pixel difference between test
36                          image and golden image has to exceed before the
37                          doublecheck comparer is used.
38        @param box: int tuple, left, upper, right, lower pixel coordinates
39                    defining a box region within which the comparison is made.
40
41        """
42        self.image_comparer = image_comparer
43        self.stop_on_first_failure = stop_on_first_failure
44        self.threshold = threshold
45        self.box = box
46
47
48    @method_logger.log
49    def verify(self, golden_image_paths, test_image_paths):
50        """
51        Verifies that two sets of images are the same using provided comparer.
52
53        @param golden_image_paths: list of complete paths to golden images.
54        @param test_image_paths: list of complete paths to test images.
55
56
57        """
58
59        if type(golden_image_paths) is not list:
60            golden_image_paths = [golden_image_paths]
61
62        if type(test_image_paths) is not list:
63            test_image_paths = [test_image_paths]
64
65        failure_count = 0
66
67        logging.debug("***BEGIN Image Verification***")
68
69        log_msgs = ["Threshold for diff pixel count = %d" % self.threshold]
70
71        test_run_comp_url = ''
72
73        for g_image, t_image in zip(golden_image_paths, test_image_paths):
74
75            with self.image_comparer:
76                comp_res = self.image_comparer.compare(g_image,
77                                                       t_image,
78                                                       self.box)
79                diff_pixels = comp_res.diff_pixel_count
80
81                """
82                If remote comparer was used, compare() returns a comparison
83                url.
84
85                If remote comparer was not invoked (local comparer succeeded)
86                compare() returns '' as comparison url. The first one you get
87                will be the same for all since they are part of the same test
88                run.
89                """
90                if test_run_comp_url == '' and comp_res.comparison_url != '':
91                    test_run_comp_url = os.path.dirname(comp_res.comparison_url)
92
93            if diff_pixels > self.threshold:
94                failure_count += 1
95
96                log_msg = ("Image: %s. Pixel diff: %d." %
97                           (os.path.basename(g_image), diff_pixels))
98
99                logging.debug(log_msg)
100                log_msgs.append(log_msg)
101
102                if self.stop_on_first_failure:
103                    raise error.TestError("%s. Bailing out." % log_msg)
104
105        if failure_count > 0:
106            cnt = len(golden_image_paths)
107            report_mes = ("*** WARNING: UI Based Image Comparison - Test "
108                          "Failure typically needs further investigation ***\t"
109                          "%d / %d test images differed substantially from the "
110                          "golden images. Comparison url: %s. %s "
111                                  % (failure_count,
112                                     cnt,
113                                     test_run_comp_url,
114                                     '\t'.join(log_msgs)))
115
116            raise error.TestFail(report_mes)
117
118        logging.debug("***All Good.***")