Merge pull request #5646 from radarhere/expand

Tests/test_image_rotate.py

@@ -33,6 +33,9 @@ def test_angle():
         with Image.open("Tests/images/test-card.png") as im:
             rotate(im, im.mode, angle)
 
+        im = hopper()
+        assert_image_equal(im.rotate(angle), im.rotate(angle, expand=1))
+
 
 def test_zero():
     for angle in (0, 45, 90, 180, 270):

docs/releasenotes/8.4.0.rst

@@ -35,7 +35,13 @@ TODO
 Other Changes
 =============
 
-TODO
-^^^^
+Speed improvement when rotating square images
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-TODO
+Starting with Pillow 3.3.0, the speed of rotating images by 90 or 270 degrees was
+improved by quickly returning :py:meth:`~PIL.Image.Image.transpose` instead, if the
+rotate operation allowed for expansion and did not specify a center or post-rotate
+translation.
+
+Since the ``expand`` flag makes no difference for square images though, Pillow now
+uses this faster method for square images without the ``expand`` flag as well.

src/PIL/Image.py

@@ -2074,10 +2074,8 @@ class Image:
                 return self.copy()
             if angle == 180:
                 return self.transpose(ROTATE_180)
-            if angle == 90 and expand:
-                return self.transpose(ROTATE_90)
-            if angle == 270 and expand:
-                return self.transpose(ROTATE_270)
+            if angle in (90, 270) and (expand or self.width == self.height):
+                return self.transpose(ROTATE_90 if angle == 90 else ROTATE_270)
 
         # Calculate the affine matrix.  Note that this is the reverse
         # transformation (from destination image to source) because we