TestReducingGapResize

Tests/test_image_resize.py

@@ -136,6 +136,93 @@ class TestImagingCoreResize(PillowTestCase):
         self.assertRaises(ValueError, self.resize, hopper(), (10, 10), 9)
 
 
+class TestReducingGapResize(PillowTestCase):
+    @classmethod
+    def setUpClass(cls):
+        cls.gradients_image = Image.open("Tests/images/radial_gradients.png")
+        cls.gradients_image.load()
+
+    def test_reducing_gap_values(self):
+        ref = self.gradients_image.resize((52, 34), Image.BICUBIC, reducing_gap=None)
+        im = self.gradients_image.resize((52, 34), Image.BICUBIC)
+        self.assert_image_equal(ref, im)
+
+        with self.assertRaises(ValueError):
+            self.gradients_image.resize((52, 34), Image.BICUBIC, reducing_gap=0)
+
+        with self.assertRaises(ValueError):
+            self.gradients_image.resize((52, 34), Image.BICUBIC, reducing_gap=0.99)
+
+    def test_reducing_gap_1(self):
+        for box, epsilon in [
+            (None, 4),
+            ((1.1, 2.2, 510.8, 510.9), 4),
+            ((3, 10, 410, 256), 10),
+        ]:
+            ref = self.gradients_image.resize((52, 34), Image.BICUBIC, box=box)
+            im = self.gradients_image.resize(
+                (52, 34), Image.BICUBIC, box=box, reducing_gap=1.0
+            )
+
+            with self.assertRaises(AssertionError):
+                self.assert_image_equal(ref, im)
+
+            self.assert_image_similar(ref, im, epsilon)
+
+    def test_reducing_gap_2(self):
+        for box, epsilon in [
+            (None, 1.5),
+            ((1.1, 2.2, 510.8, 510.9), 1.5),
+            ((3, 10, 410, 256), 1),
+        ]:
+            ref = self.gradients_image.resize((52, 34), Image.BICUBIC, box=box)
+            im = self.gradients_image.resize(
+                (52, 34), Image.BICUBIC, box=box, reducing_gap=2.0
+            )
+
+            with self.assertRaises(AssertionError):
+                self.assert_image_equal(ref, im)
+
+            self.assert_image_similar(ref, im, epsilon)
+
+    def test_reducing_gap_3(self):
+        for box, epsilon in [
+            (None, 1),
+            ((1.1, 2.2, 510.8, 510.9), 1),
+            ((3, 10, 410, 256), .5),
+        ]:
+            ref = self.gradients_image.resize((52, 34), Image.BICUBIC, box=box)
+            im = self.gradients_image.resize(
+                (52, 34), Image.BICUBIC, box=box, reducing_gap=3.0
+            )
+
+            with self.assertRaises(AssertionError):
+                self.assert_image_equal(ref, im)
+
+            self.assert_image_similar(ref, im, epsilon)
+
+    def test_reducing_gap_8(self):
+        for box in [None, (1.1, 2.2, 510.8, 510.9), (3, 10, 410, 256)]:
+            ref = self.gradients_image.resize((52, 34), Image.BICUBIC, box=box)
+            im = self.gradients_image.resize(
+                (52, 34), Image.BICUBIC, box=box, reducing_gap=8.0
+            )
+
+            self.assert_image_equal(ref, im)
+    
+    def test_box_filter(self):
+        for box, epsilon in [
+            ((0, 0, 512, 512), 5.5),
+            ((0.9, 1.7, 128, 128), 9.5),
+        ]:
+            ref = self.gradients_image.resize((52, 34), Image.BOX, box=box)
+            im = self.gradients_image.resize(
+                (52, 34), Image.BOX, box=box, reducing_gap=1.0
+            )
+
+            self.assert_image_similar(ref, im, epsilon)
+
+
 class TestImageResize(PillowTestCase):
     def test_resize(self):
         def resize(mode, size):

Tests/test_image_thumbnail.py

@@ -66,3 +66,30 @@ class TestImageThumbnail(PillowTestCase):
         ref = im.resize((32, 32), Image.BICUBIC)
         # This is still JPEG, some error is present. Without the fix it is 11.5
         self.assert_image_similar(thumb, ref, 1.5)
+
+    def test_reducing_gap_values(self):
+        im = hopper()
+        im.thumbnail((18, 18), Image.BICUBIC)
+
+        ref = hopper()
+        ref.thumbnail((18, 18), Image.BICUBIC, reducing_gap=2.0)
+        # reducing_gap=2.0 should be the default
+        self.assert_image_equal(ref, im)
+
+        ref = hopper()
+        ref.thumbnail((18, 18), Image.BICUBIC, reducing_gap=None)
+        with self.assertRaises(AssertionError):
+            self.assert_image_equal(ref, im)
+
+        self.assert_image_similar(ref, im, 3.5)
+
+    def test_reducing_gap_for_DCT_scaling(self):
+        with Image.open("Tests/images/hopper.jpg") as ref:
+            # thumbnail should call draft with reducing_gap scale
+            ref.draft(None, (18 * 3, 18 * 3))
+            ref = ref.resize((18, 18), Image.BICUBIC)
+
+            with Image.open("Tests/images/hopper.jpg") as im:
+                im.thumbnail((18, 18), Image.BICUBIC, reducing_gap=3.0)
+
+                self.assert_image_equal(ref, im)