port image type conversion transforms to prototype API (#5640)

* port image type conversion transforms to prototype API

* implement proposal for image type conversion

* add deprecation warnings

* appease mypy
Co-authored-by: Vasilis Vryniotis <datumbox@users.noreply.github.com>

test/test_prototype_transforms_functional.py

@@ -330,6 +330,10 @@ def rotate_segmentation_mask():
         and callable(kernel)
         and any(feature_type in name for feature_type in {"image", "segmentation_mask", "bounding_box", "label"})
         and "pil" not in name
+        and name
+        not in {
+            "to_image_tensor",
+        }
     ],
 )
 def test_scriptable(kernel):

torchvision/prototype/transforms/__init__.py

@@ -22,4 +22,4 @@ from ._meta import ConvertBoundingBoxFormat, ConvertImageDtype, ConvertImageColo
 from ._misc import Identity, Normalize, ToDtype, Lambda
 from ._type_conversion import DecodeImage, LabelToOneHot
 
-from ._legacy import Grayscale, RandomGrayscale  # usort: skip
+from ._deprecated import Grayscale, RandomGrayscale, ToTensor, ToPILImage, PILToTensor  # usort: skip

torchvision/prototype/transforms/_legacy.py → torchvision/prototype/transforms/_deprecated.py

-from __future__ import annotations
-
 import warnings
-from typing import Any, Dict
+from typing import Any, Dict, Optional
 
+import numpy as np
+import PIL.Image
+from torchvision.prototype import features
 from torchvision.prototype.features import ColorSpace
 from torchvision.prototype.transforms import Transform
+from torchvision.transforms import functional as _F
 from typing_extensions import Literal
 
 from ._meta import ConvertImageColorSpace
 from ._transform import _RandomApplyTransform
+from ._utils import is_simple_tensor
+
+
+class ToTensor(Transform):
+    def __init__(self) -> None:
+        warnings.warn(
+            "The transform `ToTensor()` is deprecated and will be removed in a future release. "
+            "Instead, please use `transforms.ToImageTensor()`."
+        )
+        super().__init__()
+
+    def _transform(self, input: Any, params: Dict[str, Any]) -> Any:
+        if isinstance(input, (PIL.Image.Image, np.ndarray)):
+            return _F.to_tensor(input)
+        else:
+            return input
+
+
+class PILToTensor(Transform):
+    def __init__(self) -> None:
+        warnings.warn(
+            "The transform `PILToTensor()` is deprecated and will be removed in a future release. "
+            "Instead, please use `transforms.ToImageTensor()`."
+        )
+        super().__init__()
+
+    def _transform(self, input: Any, params: Dict[str, Any]) -> Any:
+        if isinstance(input, PIL.Image.Image):
+            return _F.pil_to_tensor(input)
+        else:
+            return input
+
+
+class ToPILImage(Transform):
+    def __init__(self, mode: Optional[str] = None) -> None:
+        warnings.warn(
+            "The transform `ToPILImage()` is deprecated and will be removed in a future release. "
+            "Instead, please use `transforms.ToImagePIL()`."
+        )
+        super().__init__()
+        self.mode = mode
+
+    def _transform(self, input: Any, params: Dict[str, Any]) -> Any:
+        if is_simple_tensor(input) or isinstance(input, (features.Image, np.ndarray)):
+            return _F.to_pil_image(input, mode=self.mode)
+        else:
+            return input
 
 
 class Grayscale(Transform):

torchvision/prototype/transforms/_type_conversion.py

 from typing import Any, Dict
 
+import numpy as np
+import PIL.Image
 from torchvision.prototype import features
 from torchvision.prototype.transforms import Transform, functional as F
 
+from ._utils import is_simple_tensor
+
 
 class DecodeImage(Transform):
     def _transform(self, input: Any, params: Dict[str, Any]) -> Any:
@@ -33,3 +37,28 @@ class LabelToOneHot(Transform):
             return ""
 
         return f"num_categories={self.num_categories}"
+
+
+class ToImageTensor(Transform):
+    def __init__(self, *, copy: bool = False) -> None:
+        super().__init__()
+        self.copy = copy
+
+    def _transform(self, input: Any, params: Dict[str, Any]) -> Any:
+        if isinstance(input, (features.Image, PIL.Image.Image, np.ndarray)) or is_simple_tensor(input):
+            output = F.to_image_tensor(input, copy=self.copy)
+            return features.Image(output)
+        else:
+            return input
+
+
+class ToImagePIL(Transform):
+    def __init__(self, *, copy: bool = False) -> None:
+        super().__init__()
+        self.copy = copy
+
+    def _transform(self, input: Any, params: Dict[str, Any]) -> Any:
+        if isinstance(input, (features.Image, PIL.Image.Image, np.ndarray)) or is_simple_tensor(input):
+            return F.to_image_pil(input, copy=self.copy)
+        else:
+            return input

torchvision/prototype/transforms/functional/__init__.py

@@ -74,4 +74,10 @@ from ._geometry import (
     ten_crop_image_pil,
 )
 from ._misc import normalize_image_tensor, gaussian_blur_image_tensor
-from ._type_conversion import decode_image_with_pil, decode_video_with_av, label_to_one_hot
+from ._type_conversion import (
+    decode_image_with_pil,
+    decode_video_with_av,
+    label_to_one_hot,
+    to_image_tensor,
+    to_image_pil,
+)

torchvision/prototype/transforms/functional/_type_conversion.py

 import unittest.mock
-from typing import Dict, Any, Tuple
+from typing import Dict, Any, Tuple, Union
 
 import numpy as np
 import PIL.Image
@@ -7,6 +7,7 @@ import torch
 from torch.nn.functional import one_hot
 from torchvision.io.video import read_video
 from torchvision.prototype.utils._internal import ReadOnlyTensorBuffer
+from torchvision.transforms import functional as _F
 
 
 def decode_image_with_pil(encoded_image: torch.Tensor) -> torch.Tensor:
@@ -23,3 +24,23 @@ def decode_video_with_av(encoded_video: torch.Tensor) -> Tuple[torch.Tensor, tor
 
 def label_to_one_hot(label: torch.Tensor, *, num_categories: int) -> torch.Tensor:
     return one_hot(label, num_classes=num_categories)  # type: ignore[no-any-return]
+
+
+def to_image_tensor(image: Union[torch.Tensor, PIL.Image.Image, np.ndarray], copy: bool = False) -> torch.Tensor:
+    if isinstance(image, torch.Tensor):
+        if copy:
+            return image.clone()
+        else:
+            return image
+
+    return _F.to_tensor(image)
+
+
+def to_image_pil(image: Union[torch.Tensor, PIL.Image.Image, np.ndarray], copy: bool = False) -> PIL.Image.Image:
+    if isinstance(image, PIL.Image.Image):
+        if copy:
+            return image.copy()
+        else:
+            return image
+
+    return _F.to_pil_image(to_image_tensor(image, copy=False))

torchvision/transforms/functional.py

@@ -120,7 +120,7 @@ def _is_numpy_image(img: Any) -> bool:
     return img.ndim in {2, 3}
 
 
-def to_tensor(pic):
+def to_tensor(pic) -> Tensor:
     """Convert a ``PIL Image`` or ``numpy.ndarray`` to tensor.
     This function does not support torchscript.