[proto] Fixed issue with `F.pad` from RandomZoomOut (#6386)

* [proto] Fixed issue with `F.pad` from RandomZoomOut

* Fixed failing tests

* Fixed wrong type hint

* Fixed fill=None in pad_image_pil

* Try to support fill=None in functional

* Code formatting

test/test_prototype_transforms.py

@@ -377,12 +377,11 @@ class TestRandomZoomOut:
         transform = transforms.RandomZoomOut(fill=fill, side_range=side_range)
 
         image = mocker.MagicMock(spec=features.Image)
-        c = image.num_channels = 3
         h, w = image.image_size = (24, 32)
 
         params = transform._get_params(image)
 
-        assert params["fill"] == (fill if not isinstance(fill, int) else [fill] * c)
+        assert params["fill"] == fill
         assert len(params["padding"]) == 4
         assert 0 <= params["padding"][0] <= (side_range[1] - 1) * w
         assert 0 <= params["padding"][1] <= (side_range[1] - 1) * h

test/test_prototype_transforms_functional.py

@@ -464,7 +464,7 @@ def pad_image_tensor():
     for image, padding, fill, padding_mode in itertools.product(
         make_images(),
         [[1], [1, 1], [1, 1, 2, 2]],  # padding
-        [12, 12.0],  # fill
+        [None, 12, 12.0],  # fill
         ["constant", "symmetric", "edge", "reflect"],  # padding mode,
     ):
         yield SampleInput(image, padding=padding, fill=fill, padding_mode=padding_mode)

torchvision/prototype/features/_image.py

@@ -174,11 +174,8 @@ class Image(_Feature):
         if not isinstance(padding, int):
             padding = list(padding)
 
-        if fill is None:
-            fill = 0
-
         # PyTorch's pad supports only scalars on fill. So we need to overwrite the colour
-        if isinstance(fill, (int, float)):
+        if isinstance(fill, (int, float)) or fill is None:
             output = _F.pad_image_tensor(self, padding, fill=fill, padding_mode=padding_mode)
         else:
             from torchvision.prototype.transforms.functional._geometry import _pad_with_vector_fill

torchvision/prototype/transforms/_geometry.py

@@ -294,12 +294,7 @@ class RandomZoomOut(_RandomApplyTransform):
         bottom = canvas_height - (top + orig_h)
         padding = [left, top, right, bottom]
 
-        # vfdev-5: Can we put that into pad_image_tensor ?
-        fill = self.fill
-        if not isinstance(fill, collections.abc.Sequence):
-            fill = [fill] * orig_c
-
-        return dict(padding=padding, fill=fill)
+        return dict(padding=padding, fill=self.fill)
 
     def _transform(self, inpt: Any, params: Dict[str, Any]) -> Any:
         return F.pad(inpt, **params)

torchvision/prototype/transforms/functional/_geometry.py

@@ -531,7 +531,10 @@ pad_image_pil = _FP.pad
 
 
 def pad_image_tensor(
-    img: torch.Tensor, padding: Union[int, List[int]], fill: Union[int, float] = 0, padding_mode: str = "constant"
+    img: torch.Tensor,
+    padding: Union[int, List[int]],
+    fill: Optional[Union[int, float]] = 0,
+    padding_mode: str = "constant",
 ) -> torch.Tensor:
     num_channels, height, width = img.shape[-3:]
     extra_dims = img.shape[:-3]
@@ -555,7 +558,7 @@ def _pad_with_vector_fill(
         raise ValueError(f"Padding mode '{padding_mode}' is not supported if fill is not scalar")
 
     output = pad_image_tensor(img, padding, fill=0, padding_mode="constant")
-    left, top, right, bottom = _FT._parse_pad_padding(padding)
+    left, right, top, bottom = _FT._parse_pad_padding(padding)
     fill = torch.tensor(fill, dtype=img.dtype, device=img.device).view(-1, 1, 1)
 
     if top > 0:
@@ -614,11 +617,8 @@ def pad(
         if not isinstance(padding, int):
             padding = list(padding)
 
-        if fill is None:
-            fill = 0
-
         # TODO: PyTorch's pad supports only scalars on fill. So we need to overwrite the colour
-        if isinstance(fill, (int, float)):
+        if isinstance(fill, (int, float)) or fill is None:
             return pad_image_tensor(inpt, padding, fill=fill, padding_mode=padding_mode)
         return _pad_with_vector_fill(inpt, padding, fill=fill, padding_mode=padding_mode)
 

torchvision/transforms/functional_pil.py

@@ -155,7 +155,7 @@ def pad(
 
     if not isinstance(padding, (numbers.Number, tuple, list)):
         raise TypeError("Got inappropriate padding arg")
-    if not isinstance(fill, (numbers.Number, tuple, list)):
+    if fill is not None and not isinstance(fill, (numbers.Number, tuple, list)):
         raise TypeError("Got inappropriate fill arg")
     if not isinstance(padding_mode, str):
         raise TypeError("Got inappropriate padding_mode arg")

torchvision/transforms/functional_tensor.py

@@ -371,10 +371,13 @@ def _parse_pad_padding(padding: Union[int, List[int]]) -> List[int]:
 
 
 def pad(
-    img: Tensor, padding: Union[int, List[int]], fill: Union[int, float] = 0, padding_mode: str = "constant"
+    img: Tensor, padding: Union[int, List[int]], fill: Optional[Union[int, float]] = 0, padding_mode: str = "constant"
 ) -> Tensor:
     _assert_image_tensor(img)
 
+    if fill is None:
+        fill = 0
+
     if not isinstance(padding, (int, tuple, list)):
         raise TypeError("Got inappropriate padding arg")
     if not isinstance(fill, (int, float)):