Add Swin2SR ImageProcessorFast (#37169)

* Add fast image processor support for Swin2SR

* Add Swin2SR tests of fast image processing

* Update docs and remove unnecessary test func

* Fix docstring formatting

* Skip fast vs slow processing test

---------

Co-authored-by: Yoni Gozlan <74535834+yonigozlan@users.noreply.github.com>

docs/source/en/model_doc/swin2sr.md

@@ -50,6 +50,11 @@ A demo Space for image super-resolution with SwinSR can be found [here](https://
 [[autodoc]] Swin2SRImageProcessor
     - preprocess
 
+## Swin2SRImageProcessorFast
+
+[[autodoc]] Swin2SRImageProcessorFast
+    - preprocess
+
 ## Swin2SRConfig
 
 [[autodoc]] Swin2SRConfig

src/transformers/models/auto/image_processing_auto.py

@@ -150,7 +150,7 @@ else:
             ("superglue", ("SuperGlueImageProcessor",)),
             ("swiftformer", ("ViTImageProcessor", "ViTImageProcessorFast")),
             ("swin", ("ViTImageProcessor", "ViTImageProcessorFast")),
-            ("swin2sr", ("Swin2SRImageProcessor",)),
+            ("swin2sr", ("Swin2SRImageProcessor", "Swin2SRImageProcessorFast")),
             ("swinv2", ("ViTImageProcessor", "ViTImageProcessorFast")),
             ("table-transformer", ("DetrImageProcessor",)),
             ("timesformer", ("VideoMAEImageProcessor",)),

src/transformers/models/swin2sr/__init__.py

@@ -20,6 +20,7 @@ from ...utils.import_utils import define_import_structure
 if TYPE_CHECKING:
     from .configuration_swin2sr import *
     from .image_processing_swin2sr import *
+    from .image_processing_swin2sr_fast import *
     from .modeling_swin2sr import *
 else:
     import sys

src/transformers/models/swin2sr/image_processing_swin2sr_fast.py

@@ -0,0 +1,138 @@
+# coding=utf-8
+# Copyright 2025 The HuggingFace Inc. team. All rights reserved.
+#
+# 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.
+"""Fast Image processor class for Swin2SR."""
+
+from typing import List, Optional, Union
+
+from ...image_processing_utils import (
+    BatchFeature,
+    ChannelDimension,
+    get_image_size,
+)
+from ...image_processing_utils_fast import (
+    BASE_IMAGE_PROCESSOR_FAST_DOCSTRING,
+    BASE_IMAGE_PROCESSOR_FAST_DOCSTRING_PREPROCESS,
+    BaseImageProcessorFast,
+    DefaultFastImageProcessorKwargs,
+    group_images_by_shape,
+    reorder_images,
+)
+from ...image_utils import ImageInput
+from ...processing_utils import Unpack
+from ...utils import (
+    TensorType,
+    add_start_docstrings,
+    is_torch_available,
+    is_torchvision_available,
+    is_torchvision_v2_available,
+)
+
+
+if is_torch_available():
+    import torch
+
+if is_torchvision_available():
+    if is_torchvision_v2_available():
+        from torchvision.transforms.v2 import functional as F
+    else:
+        from torchvision.transforms import functional as F
+
+
+class Swin2SRFastImageProcessorKwargs(DefaultFastImageProcessorKwargs):
+    do_pad: Optional[bool]
+    pad_size: Optional[int]
+
+
+@add_start_docstrings(
+    "Constructs a fast Swin2SR image processor.",
+    BASE_IMAGE_PROCESSOR_FAST_DOCSTRING,
+    """
+        do_pad (`bool`, *optional*, defaults to `True`):
+            Whether to pad the image to make the height and width divisible by `window_size`.
+        pad_size (`int`, *optional*, defaults to `8`):
+            The size of the sliding window for the local attention.
+    """,
+)
+class Swin2SRImageProcessorFast(BaseImageProcessorFast):
+    do_rescale = True
+    rescale_factor = 1 / 255
+    do_pad = True
+    pad_size = 8
+    valid_kwargs = Swin2SRFastImageProcessorKwargs
+
+    def __init__(self, **kwargs: Unpack[Swin2SRFastImageProcessorKwargs]):
+        super().__init__(**kwargs)
+
+    @add_start_docstrings(
+        BASE_IMAGE_PROCESSOR_FAST_DOCSTRING_PREPROCESS,
+        """
+            do_pad (`bool`, *optional*, defaults to `True`):
+                Whether to pad the image to make the height and width divisible by `window_size`.
+            pad_size (`int`, *optional*, defaults to `8`):
+                The size of the sliding window for the local attention.
+        """,
+    )
+    def preprocess(self, images: ImageInput, **kwargs: Unpack[Swin2SRFastImageProcessorKwargs]) -> BatchFeature:
+        return super().preprocess(images, **kwargs)
+
+    def pad(self, images: "torch.Tensor", size: int) -> "torch.Tensor":
+        """
+        Pad an image to make the height and width divisible by `size`.
+
+        Args:
+            images (`torch.Tensor`):
+                Images to pad.
+            size (`int`):
+                The size to make the height and width divisible by.
+
+        Returns:
+            `torch.Tensor`: The padded images.
+        """
+        height, width = get_image_size(images, ChannelDimension.FIRST)
+        pad_height = (height // size + 1) * size - height
+        pad_width = (width // size + 1) * size - width
+
+        return F.pad(
+            images,
+            (0, 0, pad_width, pad_height),
+            padding_mode="symmetric",
+        )
+
+    def _preprocess(
+        self,
+        images: List["torch.Tensor"],
+        do_rescale: bool,
+        rescale_factor: float,
+        do_pad: bool,
+        pad_size: int,
+        return_tensors: Optional[Union[str, TensorType]],
+        interpolation: Optional["F.InterpolationMode"],
+        **kwargs,
+    ) -> BatchFeature:
+        grouped_images, grouped_images_index = group_images_by_shape(images)
+        processed_image_grouped = {}
+        for shape, stacked_images in grouped_images.items():
+            if do_rescale:
+                stacked_images = self.rescale(stacked_images, scale=rescale_factor)
+            if do_pad:
+                stacked_images = self.pad(stacked_images, size=pad_size)
+            processed_image_grouped[shape] = stacked_images
+        processed_images = reorder_images(processed_image_grouped, grouped_images_index)
+        processed_images = torch.stack(processed_images, dim=0) if return_tensors else processed_images
+
+        return BatchFeature(data={"pixel_values": processed_images}, tensor_type=return_tensors)
+
+
+__all__ = ["Swin2SRImageProcessorFast"]

tests/models/swin2sr/test_image_processing_swin2sr.py

@@ -18,7 +18,7 @@ import unittest
 import numpy as np
 
 from transformers.testing_utils import require_torch, require_vision
-from transformers.utils import is_torch_available, is_vision_available
+from transformers.utils import is_torch_available, is_torchvision_available, is_vision_available
 
 from ...test_image_processing_common import ImageProcessingTestMixin, prepare_image_inputs
 
@@ -30,6 +30,9 @@ if is_vision_available():
     from PIL import Image
 
     from transformers import Swin2SRImageProcessor
+
+    if is_torchvision_available():
+        from transformers import Swin2SRImageProcessorFast
     from transformers.image_transforms import get_image_size
 
 
@@ -97,6 +100,7 @@ class Swin2SRImageProcessingTester:
 @require_vision
 class Swin2SRImageProcessingTest(ImageProcessingTestMixin, unittest.TestCase):
     image_processing_class = Swin2SRImageProcessor if is_vision_available() else None
+    fast_image_processing_class = Swin2SRImageProcessorFast if is_torchvision_available() else None
 
     def setUp(self):
         super().setUp()
@@ -107,11 +111,12 @@ class Swin2SRImageProcessingTest(ImageProcessingTestMixin, unittest.TestCase):
         return self.image_processor_tester.prepare_image_processor_dict()
 
     def test_image_processor_properties(self):
-        image_processor = self.image_processing_class(**self.image_processor_dict)
+        for image_processing_class in self.image_processor_list:
-        self.assertTrue(hasattr(image_processor, "do_rescale"))
+            image_processing = image_processing_class(**self.image_processor_dict)
-        self.assertTrue(hasattr(image_processor, "rescale_factor"))
+            self.assertTrue(hasattr(image_processing, "do_rescale"))
-        self.assertTrue(hasattr(image_processor, "do_pad"))
+            self.assertTrue(hasattr(image_processing, "rescale_factor"))
-        self.assertTrue(hasattr(image_processor, "pad_size"))
+            self.assertTrue(hasattr(image_processing, "do_pad"))
+            self.assertTrue(hasattr(image_processing, "pad_size"))
 
     def calculate_expected_size(self, image):
         old_height, old_width = get_image_size(image)
@@ -181,3 +186,18 @@ class Swin2SRImageProcessingTest(ImageProcessingTestMixin, unittest.TestCase):
         encoded_images = image_processing(image_inputs[0], return_tensors="pt").pixel_values
         expected_output_image_shape = self.image_processor_tester.expected_output_image_shape([image_inputs[0]])
         self.assertEqual(tuple(encoded_images.shape), (1, *expected_output_image_shape))
+
+    @unittest.skip(reason="No speed gain on CPU due to minimal processing.")
+    def test_fast_is_faster_than_slow(self):
+        pass
+
+    def test_slow_fast_equivalence_batched(self):
+        image_inputs = self.image_processor_tester.prepare_image_inputs(equal_resolution=True, torchify=True)
+
+        image_processor_slow = self.image_processing_class(**self.image_processor_dict)
+        image_processor_fast = self.fast_image_processing_class(**self.image_processor_dict)
+
+        encoded_slow = image_processor_slow(image_inputs, return_tensors="pt").pixel_values
+        encoded_fast = image_processor_fast(image_inputs, return_tensors="pt").pixel_values
+
+        self.assertTrue(torch.allclose(encoded_slow, encoded_fast, atol=1e-1))