[prototype] Optimize Center Crop performance (#6880)

* Reducing unnecessary method calls

* Optimize pad branch.

* Remove unnecessary call to crop_image_tensor

* Fix linter
Co-authored-by: vfdev <vfdev.5@gmail.com>

torchvision/prototype/transforms/functional/_color.py

@@ -2,7 +2,7 @@ import torch
 from torchvision.prototype import features
 from torchvision.transforms import functional_pil as _FP, functional_tensor as _FT
 
-from ._meta import _rgb_to_gray, convert_dtype_image_tensor, get_dimensions_image_tensor, get_num_channels_image_tensor
+from ._meta import _rgb_to_gray, convert_dtype_image_tensor
 
 
 def _blend(image1: torch.Tensor, image2: torch.Tensor, ratio: float) -> torch.Tensor:
@@ -45,7 +45,7 @@ def adjust_saturation_image_tensor(image: torch.Tensor, saturation_factor: float
     if saturation_factor < 0:
         raise ValueError(f"saturation_factor ({saturation_factor}) is not non-negative.")
 
-    c = get_num_channels_image_tensor(image)
+    c = image.shape[-3]
     if c not in [1, 3]:
         raise TypeError(f"Input image tensor permitted channel values are {[1, 3]}, but found {c}")
 
@@ -75,7 +75,7 @@ def adjust_contrast_image_tensor(image: torch.Tensor, contrast_factor: float) ->
     if contrast_factor < 0:
         raise ValueError(f"contrast_factor ({contrast_factor}) is not non-negative.")
 
-    c = get_num_channels_image_tensor(image)
+    c = image.shape[-3]
     if c not in [1, 3]:
         raise TypeError(f"Input image tensor permitted channel values are {[1, 3]}, but found {c}")
     dtype = image.dtype if torch.is_floating_point(image) else torch.float32
@@ -101,7 +101,7 @@ def adjust_contrast(inpt: features.InputTypeJIT, contrast_factor: float) -> feat
 
 
 def adjust_sharpness_image_tensor(image: torch.Tensor, sharpness_factor: float) -> torch.Tensor:
-    num_channels, height, width = get_dimensions_image_tensor(image)
+    num_channels, height, width = image.shape[-3:]
     if num_channels not in (1, 3):
         raise TypeError(f"Input image tensor can have 1 or 3 channels, but found {num_channels}")
 
@@ -210,8 +210,7 @@ def adjust_hue_image_tensor(image: torch.Tensor, hue_factor: float) -> torch.Ten
     if not (-0.5 <= hue_factor <= 0.5):
         raise ValueError(f"hue_factor ({hue_factor}) is not in [-0.5, 0.5].")
 
-    c = get_num_channels_image_tensor(image)
-
+    c = image.shape[-3]
     if c not in [1, 3]:
         raise TypeError(f"Input image tensor permitted channel values are {[1, 3]}, but found {c}")
 
@@ -342,8 +341,7 @@ def solarize(inpt: features.InputTypeJIT, threshold: float) -> features.InputTyp
 
 
 def autocontrast_image_tensor(image: torch.Tensor) -> torch.Tensor:
-    c = get_num_channels_image_tensor(image)
-
+    c = image.shape[-3]
     if c not in [1, 3]:
         raise TypeError(f"Input image tensor permitted channel values are {[1, 3]}, but found {c}")
 

torchvision/prototype/transforms/functional/_geometry.py

@@ -16,12 +16,7 @@ from torchvision.transforms.functional import (
 )
 from torchvision.transforms.functional_tensor import _parse_pad_padding
 
-from ._meta import (
-    convert_format_bounding_box,
-    get_dimensions_image_tensor,
-    get_spatial_size_image_pil,
-    get_spatial_size_image_tensor,
-)
+from ._meta import convert_format_bounding_box, get_spatial_size_image_pil
 
 horizontal_flip_image_tensor = _FT.hflip
 horizontal_flip_image_pil = _FP.hflip
@@ -120,9 +115,9 @@ def resize_image_tensor(
     max_size: Optional[int] = None,
     antialias: bool = False,
 ) -> torch.Tensor:
-    num_channels, old_height, old_width = get_dimensions_image_tensor(image)
+    shape = image.shape
+    num_channels, old_height, old_width = shape[-3:]
     new_height, new_width = _compute_resized_output_size((old_height, old_width), size=size, max_size=max_size)
-    extra_dims = image.shape[:-3]
 
     if image.numel() > 0:
         image = image.reshape(-1, num_channels, old_height, old_width)
@@ -134,7 +129,7 @@ def resize_image_tensor(
             antialias=antialias,
         )
 
-    return image.reshape(extra_dims + (num_channels, new_height, new_width))
+    return image.reshape(shape[:-3] + (num_channels, new_height, new_width))
 
 
 @torch.jit.unused
@@ -270,8 +265,8 @@ def affine_image_tensor(
     if image.numel() == 0:
         return image
 
-    num_channels, height, width = image.shape[-3:]
-    extra_dims = image.shape[:-3]
+    shape = image.shape
+    num_channels, height, width = shape[-3:]
     image = image.reshape(-1, num_channels, height, width)
 
     angle, translate, shear, center = _affine_parse_args(angle, translate, scale, shear, interpolation, center)
@@ -285,7 +280,7 @@ def affine_image_tensor(
     matrix = _get_inverse_affine_matrix(center_f, angle, translate_f, scale, shear)
 
     output = _FT.affine(image, matrix, interpolation=interpolation.value, fill=fill)
-    return output.reshape(extra_dims + (num_channels, height, width))
+    return output.reshape(shape)
 
 
 @torch.jit.unused
@@ -511,8 +506,8 @@ def rotate_image_tensor(
     fill: features.FillTypeJIT = None,
     center: Optional[List[float]] = None,
 ) -> torch.Tensor:
-    num_channels, height, width = image.shape[-3:]
-    extra_dims = image.shape[:-3]
+    shape = image.shape
+    num_channels, height, width = shape[-3:]
 
     center_f = [0.0, 0.0]
     if center is not None:
@@ -538,7 +533,7 @@ def rotate_image_tensor(
     else:
         new_width, new_height = _FT._compute_affine_output_size(matrix, width, height) if expand else (width, height)
 
-    return image.reshape(extra_dims + (num_channels, new_height, new_width))
+    return image.reshape(shape[:-3] + (num_channels, new_height, new_width))
 
 
 @torch.jit.unused
@@ -675,8 +670,8 @@ def _pad_with_scalar_fill(
     fill: Union[int, float, None],
     padding_mode: str = "constant",
 ) -> torch.Tensor:
-    num_channels, height, width = image.shape[-3:]
-    extra_dims = image.shape[:-3]
+    shape = image.shape
+    num_channels, height, width = shape[-3:]
 
     if image.numel() > 0:
         image = _FT.pad(
@@ -688,7 +683,7 @@ def _pad_with_scalar_fill(
         new_height = height + top + bottom
         new_width = width + left + right
 
-    return image.reshape(extra_dims + (num_channels, new_height, new_width))
+    return image.reshape(shape[:-3] + (num_channels, new_height, new_width))
 
 
 # TODO: This should be removed once pytorch pad supports non-scalar padding values
@@ -1130,7 +1125,8 @@ elastic_transform = elastic
 
 def _center_crop_parse_output_size(output_size: List[int]) -> List[int]:
     if isinstance(output_size, numbers.Number):
-        return [int(output_size), int(output_size)]
+        s = int(output_size)
+        return [s, s]
     elif isinstance(output_size, (tuple, list)) and len(output_size) == 1:
         return [output_size[0], output_size[0]]
     else:
@@ -1156,18 +1152,21 @@ def _center_crop_compute_crop_anchor(
 
 def center_crop_image_tensor(image: torch.Tensor, output_size: List[int]) -> torch.Tensor:
     crop_height, crop_width = _center_crop_parse_output_size(output_size)
-    image_height, image_width = get_spatial_size_image_tensor(image)
+    shape = image.shape
+    if image.numel() == 0:
+        return image.reshape(shape[:-2] + (crop_height, crop_width))
+    image_height, image_width = shape[-2:]
 
     if crop_height > image_height or crop_width > image_width:
         padding_ltrb = _center_crop_compute_padding(crop_height, crop_width, image_height, image_width)
-        image = pad_image_tensor(image, padding_ltrb, fill=0)
+        image = _FT.torch_pad(image, _FT._parse_pad_padding(padding_ltrb), value=0.0)
 
-        image_height, image_width = get_spatial_size_image_tensor(image)
+        image_height, image_width = image.shape[-2:]
         if crop_width == image_width and crop_height == image_height:
             return image
 
     crop_top, crop_left = _center_crop_compute_crop_anchor(crop_height, crop_width, image_height, image_width)
-    return crop_image_tensor(image, crop_top, crop_left, crop_height, crop_width)
+    return image[..., crop_top : (crop_top + crop_height), crop_left : (crop_left + crop_width)]
 
 
 @torch.jit.unused
@@ -1332,7 +1331,7 @@ def five_crop_image_tensor(
     image: torch.Tensor, size: List[int]
 ) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor, torch.Tensor, torch.Tensor]:
     crop_height, crop_width = _parse_five_crop_size(size)
-    image_height, image_width = get_spatial_size_image_tensor(image)
+    image_height, image_width = image.shape[-2:]
 
     if crop_width > image_width or crop_height > image_height:
         msg = "Requested crop size {} is bigger than input size {}"