Merge pull request #2279 from uploadcare/fast-assert_image_similar

Fast assert_image_similar

Tests/helper.py

@@ -7,6 +7,21 @@ import tempfile
 import os
 import unittest
 
+from PIL import Image, ImageMath
+
+
+def convert_to_comparable(a, b):
+    new_a, new_b = a, b
+    if a.mode == 'P':
+        new_a = Image.new('L', a.size)
+        new_b = Image.new('L', b.size)
+        new_a.putdata(a.getdata())
+        new_b.putdata(b.getdata())
+    elif a.mode == 'I;16':
+        new_a = a.convert('I')
+        new_b = b.convert('I')
+    return new_a, new_b
+
 
 class PillowTestCase(unittest.TestCase):
 
@@ -80,14 +95,13 @@ class PillowTestCase(unittest.TestCase):
             a.size, b.size,
             msg or "got size %r, expected %r" % (a.size, b.size))
 
+        a, b = convert_to_comparable(a, b)
+
         diff = 0
-        try:
-            ord(b'0')
-            for abyte, bbyte in zip(a.tobytes(), b.tobytes()):
-                diff += abs(ord(abyte)-ord(bbyte))
-        except:
-            for abyte, bbyte in zip(a.tobytes(), b.tobytes()):
-                diff += abs(abyte-bbyte)
+        for ach, bch in zip(a.split(), b.split()):
+            chdiff = ImageMath.eval("abs(a - b)", a=ach, b=bch).convert('L')
+            diff += sum(i * num for i, num in enumerate(chdiff.histogram()))
+
         ave_diff = float(diff)/(a.size[0]*a.size[1])
         self.assertGreaterEqual(
             epsilon, ave_diff,

Tests/test_file_msp.py

@@ -31,7 +31,7 @@ class TestFileMsp(PillowTestCase):
 
         # Assert
         self.assertEqual(im.size, (128, 128))
-        self.assert_image_similar(im, hopper("1"), 4)
+        self.assert_image_equal(im, hopper("1"), 4)
 
     def test_cannot_save_wrong_mode(self):
         # Arrange

Tests/test_imagecms.py

@@ -205,7 +205,7 @@ class TestImageCms(PillowTestCase):
 
         target = Image.open('Tests/images/hopper.Lab.tif')
 
-        self.assert_image_similar(i, target, 30)
+        self.assert_image_similar(i, target, 3.5)
 
     def test_lab_srgb(self):
         psRGB = ImageCms.createProfile("sRGB")