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Merge pull request #1920 from uploadcare/resampling-accuracy-tests
Tests for resampling accuracy
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commit
73c81404e6
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@ -1,8 +1,8 @@
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from helper import unittest, PillowTestCase, hopper
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from PIL import Image
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from PIL import Image, ImageDraw
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class TestImagingCoreResize(PillowTestCase):
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class TestImagingResampleVulnerability(PillowTestCase):
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# see https://github.com/python-pillow/Pillow/issues/1710
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def test_overflow(self):
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im = hopper('L')
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@ -33,5 +33,122 @@ class TestImagingCoreResize(PillowTestCase):
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except ValueError:
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self.assertTrue(True, "Should raise ValueError")
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class TestImagingCoreResampleAccuracy(PillowTestCase):
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def make_case(self, size, color):
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"""Makes a sample image with two dark and two bright squares.
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For example:
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e0 e0 1f 1f
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e0 e0 1f 1f
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1f 1f e0 e0
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1f 1f e0 e0
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"""
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dark = (255 - color, 255 - color, 255 - color, 255 - color)
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bright = (color, color, color, color)
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i = Image.new('RGBX', size, dark)
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rectangle = ImageDraw.Draw(i).rectangle
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rectangle((0, 0, size[0] // 2 - 1, size[1] // 2 - 1), bright)
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rectangle((size[0] // 2, size[1] // 2, size[0], size[1]), bright)
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return i
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def make_sample(self, data, size):
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"""Restores a sample image from given data string which contains
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hex-encoded pixels from the top left fourth of a sample.
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"""
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data = data.replace(' ', '')
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sample = Image.new('L', size)
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s_px = sample.load()
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w, h = size[0] // 2, size[1] // 2
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for y in range(h):
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for x in range(w):
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val = int(data[(y * w + x) * 2:(y * w + x + 1) * 2], 16)
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s_px[x, y] = val
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s_px[size[0] - x - 1, size[1] - y - 1] = val
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s_px[x, size[1] - y - 1] = 255 - val
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s_px[size[0] - x - 1, y] = 255 - val
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return sample
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def check_case(self, case, sample):
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for channel in case.split():
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s_px = sample.load()
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c_px = channel.load()
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for y in range(case.size[1]):
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for x in range(case.size[0]):
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if c_px[x, y] != s_px[x, y]:
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message = '\nHave: \n{}\n\nExpected: \n{}'.format(
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self.serialize_image(channel),
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self.serialize_image(sample),
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)
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self.assertEqual(s_px[x, y], c_px[x, y], message)
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def serialize_image(self, image):
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s_px = image.load()
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return '\n'.join(
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' '.join(
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'{:02x}'.format(s_px[x, y])
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for x in range(image.size[0])
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)
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for y in range(image.size[1])
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)
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def test_reduce_bilinear(self):
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case = self.make_case((8, 8), 0xe1)
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data = ('e1 c9'
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'c9 b7')
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self.check_case(
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case.resize((4, 4), Image.BILINEAR),
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self.make_sample(data, (4, 4)))
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def test_reduce_bicubic(self):
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case = self.make_case((12, 12), 0xe1)
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data = ('e1 e3 d4'
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'e3 e5 d6'
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'd4 d6 c9')
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self.check_case(
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case.resize((6, 6), Image.BICUBIC),
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self.make_sample(data, (6, 6)))
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def test_reduce_lanczos(self):
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case = self.make_case((16, 16), 0xe1)
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data = ('e1 e0 e4 d7'
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'e0 df e3 d6'
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'e4 e3 e7 da'
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'd7 d6 d9 ce')
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self.check_case(
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case.resize((8, 8), Image.LANCZOS),
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self.make_sample(data, (8, 8)))
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def test_enlarge_bilinear(self):
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case = self.make_case((2, 2), 0xe1)
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data = ('e1 b0'
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'b0 98')
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self.check_case(
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case.resize((4, 4), Image.BILINEAR),
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self.make_sample(data, (4, 4)))
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def test_enlarge_bicubic(self):
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case = self.make_case((4, 4), 0xe1)
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data = ('e1 e5 ee b9'
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'e5 e9 f3 bc'
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'ee f3 fd c1'
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'b9 bc c1 a2')
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self.check_case(
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case.resize((8, 8), Image.BICUBIC),
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self.make_sample(data, (8, 8)))
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def test_enlarge_lanczos(self):
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case = self.make_case((6, 6), 0xe1)
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data = ('e1 e0 db ed f5 b8'
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'e0 df da ec f3 b7'
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'db db d6 e7 ee b5'
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'ed ec e6 fb ff bf'
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'f5 f4 ee ff ff c4'
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'b8 b7 b4 bf c4 a0')
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self.check_case(
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case.resize((12, 12), Image.LANCZOS),
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self.make_sample(data, (12, 12)))
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if __name__ == '__main__':
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unittest.main()
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