109-spatial-flip

monai/transforms/transforms.py

@@ -62,6 +62,24 @@ def __call__(self, img):
         return rescale_array(img, self.minv, self.maxv, self.dtype)
 
 
+@export
+class Flip:
+    """Reverses the order of elements along the given axis. Preserves shape.
+    Uses np.flip in practice. See numpy.flip for additional details.
+
+    Args:
+        axes (None, int or tuple of ints): Axes along which to flip over. Default is None.
+    """
+
+    def __init__(self, axis=None):
+        assert axis is None or isinstance(axis, (int, list, tuple)), \
+            "axis must be None, int or tuple of ints."
+        self.axis = axis
+
+    def __call__(self, img):
+        return np.flip(img, self.axis)
+
+
 @export
 class ToTensor:
     """

tests/test_flip.py

@@ -0,0 +1,44 @@
+# Copyright 2020 MONAI Consortium
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#     http://www.apache.org/licenses/LICENSE-2.0
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import unittest
+
+import numpy as np
+from parameterized import parameterized
+
+from monai.transforms import Flip
+from tests.utils import NumpyImageTestCase2D
+
+
+class FlipTest(NumpyImageTestCase2D):
+
+    @parameterized.expand([
+        ("wrong_axis", ['s', 1], TypeError),
+        ("not_numbers", 's', AssertionError)
+    ])
+    def test_invalid_inputs(self, _, axis, raises):
+        with self.assertRaises(raises):
+            flip = Flip(axis)
+            flip(self.imt)
+
+    @parameterized.expand([
+        ("no_axis", None),
+        ("one_axis", 1),
+        ("many_axis", [0, 1, 2])
+    ])
+    def test_correct_results(self, _, axis):
+        flip = Flip(axis=axis)
+        expected = np.flip(self.imt, axis)
+        self.assertTrue(np.allclose(expected, flip(self.imt)))
+
+
+if __name__ == '__main__':
+    unittest.main()