add spatial rescaler (#414)

* add spatial rescaler

* fix import path

* add unittests

* fix test name

* support size argument

* fix docstring and add more test cases for multiplier

* fix error message

generative/networks/blocks/__init__.py

@@ -11,5 +11,6 @@
 
 from __future__ import annotations
 
+from .encoder_modules import SpatialRescaler
 from .selfattention import SABlock
 from .transformerblock import TransformerBlock

generative/networks/blocks/encoder_modules.py

@@ -0,0 +1,83 @@
+# Copyright (c) MONAI Consortium
+# 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.
+
+from __future__ import annotations
+
+from collections.abc import Sequence
+from functools import partial
+
+import torch
+import torch.nn as nn
+from monai.networks.blocks import Convolution
+
+__all__ = ["SpatialRescaler"]
+
+
+class SpatialRescaler(nn.Module):
+    """
+    SpatialRescaler based on https://github.com/CompVis/latent-diffusion/blob/main/ldm/modules/encoders/modules.py
+
+    Args:
+        spatial_dims: number of spatial dimensions.
+        n_stages: number of interpolation stages.
+        size: output spatial size (int or Tuple[int] or Tuple[int, int] or Tuple[int, int, int]).
+        method: algorithm used for sampling.
+        multiplier: multiplier for spatial size. If `multiplier` is a sequence,
+            its length has to match the number of spatial dimensions; `input.dim() - 2`.
+        in_channels: number of input channels.
+        out_channels: number of output channels.
+        bias: whether to have a bias term.
+    """
+
+    def __init__(
+        self,
+        spatial_dims: int = 2,
+        n_stages: int = 1,
+        size: Sequence[int] | int | None = None,
+        method: str = "bilinear",
+        multiplier: Sequence[float] | float | None = None,
+        in_channels: int = 3,
+        out_channels: int = None,
+        bias: bool = False,
+    ):
+        super().__init__()
+        self.n_stages = n_stages
+        assert self.n_stages >= 0
+        assert method in ["nearest", "linear", "bilinear", "trilinear", "bicubic", "area"]
+        if size is not None and n_stages != 1:
+            raise ValueError("when size is not None, n_stages should be 1.")
+        if size is not None and multiplier is not None:
+            raise ValueError("only one of size or multiplier should be defined.")
+        self.multiplier = multiplier
+        self.interpolator = partial(torch.nn.functional.interpolate, mode=method, size=size)
+        self.remap_output = out_channels is not None
+        if self.remap_output:
+            print(f"Spatial Rescaler mapping from {in_channels} to {out_channels} channels before resizing.")
+            self.channel_mapper = Convolution(
+                spatial_dims=spatial_dims,
+                in_channels=in_channels,
+                out_channels=out_channels,
+                kernel_size=1,
+                conv_only=True,
+                bias=bias,
+            )
+
+    def forward(self, x: torch.Tensor) -> torch.Tensor:
+        if self.remap_output:
+            x = self.channel_mapper(x)
+
+        for stage in range(self.n_stages):
+            x = self.interpolator(x, scale_factor=self.multiplier)
+
+        return x
+
+    def encode(self, x: torch.Tensor) -> torch.Tensor:
+        return self(x)

tests/test_encoder_modules.py

@@ -0,0 +1,130 @@
+# Copyright (c) MONAI Consortium
+# 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.
+
+from __future__ import annotations
+
+import unittest
+
+import torch
+from parameterized import parameterized
+
+from generative.networks.blocks import SpatialRescaler
+
+device = torch.device("cuda:0" if torch.cuda.is_available() else "cpu")
+
+CASES = [
+    [
+        {
+            "spatial_dims": 2,
+            "n_stages": 1,
+            "method": "bilinear",
+            "multiplier": 0.5,
+            "in_channels": None,
+            "out_channels": None,
+        },
+        (1, 1, 16, 16),
+        (1, 1, 8, 8),
+    ],
+    [
+        {
+            "spatial_dims": 2,
+            "n_stages": 1,
+            "method": "bilinear",
+            "multiplier": 0.5,
+            "in_channels": 3,
+            "out_channels": 2,
+        },
+        (1, 3, 16, 16),
+        (1, 2, 8, 8),
+    ],
+    [
+        {
+            "spatial_dims": 3,
+            "n_stages": 1,
+            "method": "trilinear",
+            "multiplier": 0.5,
+            "in_channels": None,
+            "out_channels": None,
+        },
+        (1, 1, 16, 16, 16),
+        (1, 1, 8, 8, 8),
+    ],
+    [
+        {
+            "spatial_dims": 3,
+            "n_stages": 1,
+            "method": "trilinear",
+            "multiplier": 0.5,
+            "in_channels": 3,
+            "out_channels": 2,
+        },
+        (1, 3, 16, 16, 16),
+        (1, 2, 8, 8, 8),
+    ],
+    [
+        {
+            "spatial_dims": 3,
+            "n_stages": 1,
+            "method": "trilinear",
+            "multiplier": (0.25, 0.5, 0.75),
+            "in_channels": 3,
+            "out_channels": 2,
+        },
+        (1, 3, 20, 20, 20),
+        (1, 2, 5, 10, 15),
+    ],
+    [
+        {"spatial_dims": 2, "n_stages": 1, "size": (8, 8), "method": "bilinear", "in_channels": 3, "out_channels": 2},
+        (1, 3, 16, 16),
+        (1, 2, 8, 8),
+    ],
+    [
+        {
+            "spatial_dims": 3,
+            "n_stages": 1,
+            "size": (8, 8, 8),
+            "method": "trilinear",
+            "in_channels": None,
+            "out_channels": None,
+        },
+        (1, 1, 16, 16, 16),
+        (1, 1, 8, 8, 8),
+    ],
+]
+
+
+class TestSpatialRescaler(unittest.TestCase):
+    @parameterized.expand(CASES)
+    def test_shape(self, input_param, input_shape, expected_shape):
+        module = SpatialRescaler(**input_param).to(device)
+
+        result = module(torch.randn(input_shape).to(device))
+        self.assertEqual(result.shape, expected_shape)
+
+    def test_method_not_in_available_options(self):
+        with self.assertRaises(AssertionError):
+            SpatialRescaler(method="none")
+
+    def test_n_stages_is_negative(self):
+        with self.assertRaises(AssertionError):
+            SpatialRescaler(n_stages=-1)
+
+    def test_use_size_but_n_stages_is_not_one(self):
+        with self.assertRaises(ValueError):
+            SpatialRescaler(n_stages=2, size=[8, 8, 8])
+
+    def test_both_size_and_multiplier_defined(self):
+        with self.assertRaises(ValueError):
+            SpatialRescaler(size=[1, 2, 3], multiplier=0.5)
+
+
+if __name__ == "__main__":
+    unittest.main()