Merge pull request #1920 from uploadcare/resampling-accuracy-tests

Tests for resampling accuracy
This commit is contained in:
Alexander Karpinsky 2016-05-26 02:05:15 +03:00
commit 73c81404e6

View File

@ -1,8 +1,8 @@
from helper import unittest, PillowTestCase, hopper
from PIL import Image
from PIL import Image, ImageDraw
class TestImagingCoreResize(PillowTestCase):
class TestImagingResampleVulnerability(PillowTestCase):
# see https://github.com/python-pillow/Pillow/issues/1710
def test_overflow(self):
im = hopper('L')
@ -33,5 +33,122 @@ class TestImagingCoreResize(PillowTestCase):
except ValueError:
self.assertTrue(True, "Should raise ValueError")
class TestImagingCoreResampleAccuracy(PillowTestCase):
def make_case(self, size, color):
"""Makes a sample image with two dark and two bright squares.
For example:
e0 e0 1f 1f
e0 e0 1f 1f
1f 1f e0 e0
1f 1f e0 e0
"""
dark = (255 - color, 255 - color, 255 - color, 255 - color)
bright = (color, color, color, color)
i = Image.new('RGBX', size, dark)
rectangle = ImageDraw.Draw(i).rectangle
rectangle((0, 0, size[0] // 2 - 1, size[1] // 2 - 1), bright)
rectangle((size[0] // 2, size[1] // 2, size[0], size[1]), bright)
return i
def make_sample(self, data, size):
"""Restores a sample image from given data string which contains
hex-encoded pixels from the top left fourth of a sample.
"""
data = data.replace(' ', '')
sample = Image.new('L', size)
s_px = sample.load()
w, h = size[0] // 2, size[1] // 2
for y in range(h):
for x in range(w):
val = int(data[(y * w + x) * 2:(y * w + x + 1) * 2], 16)
s_px[x, y] = val
s_px[size[0] - x - 1, size[1] - y - 1] = val
s_px[x, size[1] - y - 1] = 255 - val
s_px[size[0] - x - 1, y] = 255 - val
return sample
def check_case(self, case, sample):
for channel in case.split():
s_px = sample.load()
c_px = channel.load()
for y in range(case.size[1]):
for x in range(case.size[0]):
if c_px[x, y] != s_px[x, y]:
message = '\nHave: \n{}\n\nExpected: \n{}'.format(
self.serialize_image(channel),
self.serialize_image(sample),
)
self.assertEqual(s_px[x, y], c_px[x, y], message)
def serialize_image(self, image):
s_px = image.load()
return '\n'.join(
' '.join(
'{:02x}'.format(s_px[x, y])
for x in range(image.size[0])
)
for y in range(image.size[1])
)
def test_reduce_bilinear(self):
case = self.make_case((8, 8), 0xe1)
data = ('e1 c9'
'c9 b7')
self.check_case(
case.resize((4, 4), Image.BILINEAR),
self.make_sample(data, (4, 4)))
def test_reduce_bicubic(self):
case = self.make_case((12, 12), 0xe1)
data = ('e1 e3 d4'
'e3 e5 d6'
'd4 d6 c9')
self.check_case(
case.resize((6, 6), Image.BICUBIC),
self.make_sample(data, (6, 6)))
def test_reduce_lanczos(self):
case = self.make_case((16, 16), 0xe1)
data = ('e1 e0 e4 d7'
'e0 df e3 d6'
'e4 e3 e7 da'
'd7 d6 d9 ce')
self.check_case(
case.resize((8, 8), Image.LANCZOS),
self.make_sample(data, (8, 8)))
def test_enlarge_bilinear(self):
case = self.make_case((2, 2), 0xe1)
data = ('e1 b0'
'b0 98')
self.check_case(
case.resize((4, 4), Image.BILINEAR),
self.make_sample(data, (4, 4)))
def test_enlarge_bicubic(self):
case = self.make_case((4, 4), 0xe1)
data = ('e1 e5 ee b9'
'e5 e9 f3 bc'
'ee f3 fd c1'
'b9 bc c1 a2')
self.check_case(
case.resize((8, 8), Image.BICUBIC),
self.make_sample(data, (8, 8)))
def test_enlarge_lanczos(self):
case = self.make_case((6, 6), 0xe1)
data = ('e1 e0 db ed f5 b8'
'e0 df da ec f3 b7'
'db db d6 e7 ee b5'
'ed ec e6 fb ff bf'
'f5 f4 ee ff ff c4'
'b8 b7 b4 bf c4 a0')
self.check_case(
case.resize((12, 12), Image.LANCZOS),
self.make_sample(data, (12, 12)))
if __name__ == '__main__':
unittest.main()