def test_distance_all_channels(self):
diff = ImageDiff(self.get_white_image(), self.get_black_image())
self.assertAlmostEqual(diff.get_distance(), 100 * 100, delta=0.001)
def test_nrmsd_one_channel(self):
diff = ImageDiff(self.get_image((255, 0, 0)), self.get_black_image())
self.assertEqual(diff.get_nrmsd(), math.sqrt(1.0 / 3))
def test_nrmsd_half_filled(self):
diff = ImageDiff(self.get_black_image(), self.get_half_filled_image())
self.assertEqual(diff.get_nrmsd(), math.sqrt(0.5))
def compareScreenshot(self, element_or_selector, filename, threshold=0.1):
"""
Assert that a screenshot of an element is the same as a screenshot on disk,
within a given threshold.
:param element_or_selector:
Either a CSS selector as a string or a
:py:class:`~needle.driver.NeedleWebElement` object that represents
the element to capture.
:param name:
A name for the screenshot, which will be appended with ``.png``.
:param threshold:
The threshold for triggering a test failure.
"""
if not isinstance(filename, basestring):
raise NotImplementedError
baseline_file = os.path.join(self.baseline_directory,
'%s.png' % filename)
output_file = os.path.join(self.output_directory, '%s.png' % filename)
if self.capture and os.path.exists(baseline_file):
self.skipTest('Not capturing %s, image already exists. If you '
'want to capture this element again, delete %s' %
(filename, baseline_file))
yield
if not isinstance(element_or_selector, NeedleWebElement):
element = self.driver.find_element_by_css_selector(
element_or_selector)
else:
element = element_or_selector
if self.capture:
element.get_screenshot().save(baseline_file)
return
else:
screenshot = element.get_screenshot()
screenshot.save(output_file)
if self.use_perceptualdiff:
diff_filename = output_file.replace(".png", ".diff.ppm")
try:
# BUG: figure out how best to convert threshold distances to pixel counts
subprocess.check_call([
"perceptualdiff", "-output", diff_filename,
baseline_file, output_file
])
except subprocess.CalledProcessError:
raise AssertionError(
"The saved screenshot for '%s' did not match "
"the screenshot captured: see %s" %
(filename, diff_filename))
else:
baseline_image = Image.open(baseline_file)
diff = ImageDiff(screenshot, baseline_image)
distance = abs(diff.get_distance())
if distance > threshold:
raise AssertionError(
"The saved screenshot for '%s' did not match "
"the screenshot captured (by a distance of %.2f)" %
(filename, distance))