| # Copyright 2014 The Chromium OS Authors. All rights reserved. |
| # Use of this source code is governed by a BSD-style license that can be |
| # found in the LICENSE file. |
| |
| """Classes to do screen comparison.""" |
| |
| import logging |
| import os |
| import time |
| |
| from PIL import ImageChops |
| |
| |
| class ScreenComparer(object): |
| """A class to compare two screens. |
| |
| Calling its member method compare() does the comparison. |
| |
| """ |
| |
| def __init__(self, capturer1, capturer2, output_dir, pixel_diff_margin, |
| wrong_pixels_margin, skip_if_diff_sizes=False): |
| """Initializes the ScreenComparer objects. |
| |
| @param capture1: The screen capturer object. |
| @param capture2: The screen capturer object. |
| @param output_dir: The directory for output images. |
| @param pixel_diff_margin: The margin for comparing a pixel. Only |
| if a pixel difference exceeds this margin, will treat as a wrong |
| pixel. Sets None means using default value by detecting |
| connector type. |
| @param wrong_pixels_margin: The percentage of margin for wrong pixels. |
| The value is in a closed interval [0.0, 1.0]. If the total |
| number of wrong pixels exceeds this margin, the check fails. |
| @param skip_if_diff_sizes: Skip the comparison if the image sizes are |
| different. Used in mirrored test as the internal and external |
| screens have different resolutions. |
| """ |
| # TODO(waihong): Support multiple capturers. |
| self._capturer1 = capturer1 |
| self._capturer2 = capturer2 |
| self._output_dir = output_dir |
| self._pixel_diff_margin = pixel_diff_margin |
| assert 0.0 <= wrong_pixels_margin <= 1.0 |
| self._wrong_pixels_margin = wrong_pixels_margin |
| self._skip_if_diff_sizes = skip_if_diff_sizes |
| |
| |
| def compare(self): |
| """Compares the screens. |
| |
| @return: None if the check passes; otherwise, a string of error message. |
| """ |
| tags = [self._capturer1.TAG, self._capturer2.TAG] |
| images = [self._capturer1.capture(), self._capturer2.capture()] |
| |
| if None in images: |
| message = ('Failed to capture the screen of %s.' % |
| tags[images.index(None)]) |
| logging.error(message) |
| return message |
| |
| # Sometimes the format of images got from X is not RGB, |
| # which may lead to ValueError raised by ImageChops.difference(). |
| # So here we check the format before comparing them. |
| for i, image in enumerate(images): |
| if image.mode != 'RGB': |
| images[i] = image.convert('RGB') |
| |
| message = 'Unexpected exception' |
| time_str = time.strftime('%H%M%S') |
| try: |
| # The size property is the resolution of the image. |
| if images[0].size != images[1].size: |
| message = ('Sizes of images %s and %s do not match: ' |
| '%dx%d != %dx%d' % |
| (tuple(tags) + images[0].size + images[1].size)) |
| if self._skip_if_diff_sizes: |
| logging.info(message) |
| return None |
| else: |
| logging.error(message) |
| return message |
| |
| size = images[0].size[0] * images[0].size[1] |
| max_acceptable_wrong_pixels = int(self._wrong_pixels_margin * size) |
| |
| logging.info('Comparing the images between %s and %s...', *tags) |
| diff_image = ImageChops.difference(*images) |
| histogram = diff_image.convert('L').histogram() |
| |
| num_wrong_pixels = sum(histogram[self._pixel_diff_margin + 1:]) |
| max_diff_value = max(filter( |
| lambda x: histogram[x], xrange(len(histogram)))) |
| if num_wrong_pixels > 0: |
| logging.debug('Histogram of difference: %r', histogram) |
| prefix_str = '%s-%dx%d' % ((time_str,) + images[0].size) |
| message = ('Result of %s: total %d wrong pixels ' |
| '(diff up to %d)' % ( |
| prefix_str, num_wrong_pixels, max_diff_value)) |
| if num_wrong_pixels > max_acceptable_wrong_pixels: |
| logging.error(message) |
| return message |
| |
| message += (', within the acceptable range %d' % |
| max_acceptable_wrong_pixels) |
| logging.warning(message) |
| else: |
| logging.info('Result: all pixels match (within +/- %d)', |
| max_diff_value) |
| message = None |
| return None |
| finally: |
| if message is not None: |
| for i in (0, 1): |
| # Use time and image size as the filename prefix. |
| prefix_str = '%s-%dx%d' % ((time_str,) + images[i].size) |
| # TODO(waihong): Save to a better lossless format. |
| file_path = os.path.join( |
| self._output_dir, |
| '%s-%s.png' % (prefix_str, tags[i])) |
| logging.info('Output the image %d to %s', i, file_path) |
| images[i].save(file_path) |
| |
| file_path = os.path.join( |
| self._output_dir, '%s-diff.png' % prefix_str) |
| logging.info('Output the diff image to %s', file_path) |
| diff_image = ImageChops.difference(*images) |
| gray_image = diff_image.convert('L') |
| bw_image = gray_image.point( |
| lambda x: 0 if x <= self._pixel_diff_margin else 255, |
| '1') |
| bw_image.save(file_path) |
