Issue #1263 Support for various dtypes in InvertImg. (#1277)

* Issue #1263 Added support for float p in InvertImg and adapted test func accordingly

* Support for various dtypes in invert(). And new test function for it

* Resolved requested changes

Co-authored-by: Mikhail Druzhinin <dipetm@gmail.com>

albumentations/augmentations/functional.py

@@ -795,8 +795,10 @@ def add_shadow(img, vertices_list):
     return image_rgb
 
 
-def invert(img):
-    return 255 - img
+def invert(img: np.ndarray) -> np.ndarray:
+    # Supports all the valid dtypes
+    # clips the img to avoid unexpected behaviour.
+    return MAX_VALUES_BY_DTYPE[img.dtype] - img
 
 
 def channel_shuffle(img, channels_shuffled):

albumentations/augmentations/transforms.py

@@ -1546,7 +1546,7 @@ class InvertImg(ImageOnlyTransform):
         image
 
     Image types:
-        uint8
+        uint8, float32
     """
 
     def apply(self, img, **params):

tests/test_transforms.py

@@ -312,6 +312,17 @@ def test_additional_targets_for_image_only(augmentation_cls, params):
         assert np.array_equal(aug1, aug2)
 
 
+def test_image_invert():
+    for _ in range(10):
+        # test for np.uint8 dtype
+        image1 = np.random.randint(low=0, high=256, size=(100, 100, 3), dtype=np.uint8)
+        image2 = A.to_float(image1)
+        r_int = F.invert(F.invert(image1))
+        r_float = F.invert(F.invert(image2))
+        r_to_float = A.to_float(r_int)
+        assert np.allclose(r_float, r_to_float, atol=0.01)
+
+
 def test_lambda_transform():
     def negate_image(image, **kwargs):
         return -image