Fix rotation with resizing and custom center

skimage/transform/_warps.py

@@ -251,16 +251,21 @@ def rotate(image, angle, resize=False, center=None, order=1, mode='constant',
         center = np.array((cols, rows)) / 2. - 0.5
     else:
         center = np.asarray(center)
-    tform1 = SimilarityTransform(translation=-center)
+    tform1 = SimilarityTransform(translation=center)
     tform2 = SimilarityTransform(rotation=np.deg2rad(angle))
-    tform3 = SimilarityTransform(translation=center)
-    tform = tform1 + tform2 + tform3
+    tform3 = SimilarityTransform(translation=-center)
+    tform = tform3 + tform2 + tform1
 
     output_shape = None
     if resize:
         # determine shape of output image
-        corners = np.array([[1, 1], [1, rows], [cols, rows], [cols, 1]])
-        corners = tform(corners - 1)
+        corners = np.array([
+            [0, 0],
+            [0, rows - 1],
+            [cols - 1, rows - 1],
+            [cols - 1, 0]
+        ])
+        corners = tform.inverse(corners)
         minc = corners[:, 0].min()
         minr = corners[:, 1].min()
         maxc = corners[:, 0].max()
@@ -270,7 +275,7 @@ def rotate(image, angle, resize=False, center=None, order=1, mode='constant',
         output_shape = np.ceil((out_rows, out_cols))
 
         # fit output image in new shape
-        translation = ((cols - out_cols) / 2., (rows - out_rows) / 2.)
+        translation = (minc, minr)
         tform4 = SimilarityTransform(translation=translation)
         tform = tform4 + tform
 

skimage/transform/tests/test_warps.py

@@ -132,6 +132,20 @@ def test_rotate_center():
     assert_almost_equal(x0, x)
 
 
+def test_rotate_resize_center():
+    x = np.zeros((10, 10), dtype=np.double)
+    x[0, 0] = 1
+
+    ref_x45 = np.zeros((14, 14), dtype=np.double)
+    ref_x45[6, 0] = 1
+    ref_x45[7, 0] = 1
+
+    x45 = rotate(x, 45, resize=True, center=(3, 3), order=0)
+    # new dimension should be d = sqrt(2 * (10/2)^2)
+    assert x45.shape == (14, 14)
+    assert_equal(x45, ref_x45)
+
+
 def test_rescale():
     # same scale factor
     x = np.zeros((5, 5), dtype=np.double)