Add crop logic to Potsdam2D datamodule

conf/potsdam2d.yaml

@@ -0,0 +1,21 @@
+experiment:
+  task: "potsdam2d"
+  module:
+    loss: "ce"
+    model: "unet"
+    backbone: "resnet18"
+    weights: null
+    learning_rate: 1e-3
+    learning_rate_schedule_patience: 6
+    verbose: false
+    in_channels: 4
+    num_classes: 6
+    num_filters: 1
+    ignore_index: null
+  datamodule:
+    root: "data/potsdam"
+    num_tiles_per_batch: 16
+    num_patches_per_tile: 16
+    patch_size: 64
+    val_split_pct: 0.5
+    num_workers: 0

tests/conf/potsdam2d.yaml

@@ -0,0 +1,21 @@
+experiment:
+  task: "potsdam2d"
+  module:
+    loss: "ce"
+    model: "unet"
+    backbone: "resnet18"
+    weights: null
+    learning_rate: 1e-3
+    learning_rate_schedule_patience: 6
+    verbose: false
+    in_channels: 4
+    num_classes: 6
+    num_filters: 1
+    ignore_index: null
+  datamodule:
+    root: "tests/data/potsdam"
+    num_tiles_per_batch: 1
+    num_patches_per_tile: 1
+    patch_size: 2
+    val_split_pct: 0.5
+    num_workers: 0

tests/trainers/test_segmentation.py

@@ -19,6 +19,7 @@
     LandCoverAIDataModule,
     LoveDADataModule,
     NAIPChesapeakeDataModule,
+    Potsdam2DDataModule,
     SEN12MSDataModule,
     SpaceNet1DataModule,
     Vaihingen2DDataModule,
@@ -46,6 +47,7 @@ class TestSemanticSegmentationTask:
             ("landcoverai", LandCoverAIDataModule),
             ("loveda", LoveDADataModule),
             ("naipchesapeake", NAIPChesapeakeDataModule),
+            ("potsdam2d", Potsdam2DDataModule),
             ("sen12ms_all", SEN12MSDataModule),
             ("sen12ms_s1", SEN12MSDataModule),
             ("sen12ms_s2_all", SEN12MSDataModule),

torchgeo/datamodules/potsdam.py

@@ -3,14 +3,19 @@
 
 """Potsdam datamodule."""
 
-from typing import Any, Dict, Optional
+from typing import Any, Dict, Optional, Tuple, Union
 
 import matplotlib.pyplot as plt
 import pytorch_lightning as pl
-from torch.utils.data import DataLoader, Dataset
-from torchvision.transforms import Compose
+from einops import rearrange
+from kornia.augmentation import Normalize
+from torch import Tensor
+from torch.utils.data import DataLoader
 
 from ..datasets import Potsdam2D
+from ..samplers.utils import _to_tuple
+from ..transforms import AugmentationSequential
+from ..transforms.transforms import _ExtractTensorPatches, _RandomNCrop
 from .utils import dataset_split
 
 
@@ -24,105 +29,130 @@ class Potsdam2DDataModule(pl.LightningDataModule):
 
     def __init__(
         self,
-        batch_size: int = 64,
-        num_workers: int = 0,
+        num_tiles_per_batch: int = 16,
+        num_patches_per_tile: int = 16,
+        patch_size: Union[Tuple[int, int], int] = 64,
         val_split_pct: float = 0.2,
+        num_workers: int = 0,
         **kwargs: Any,
     ) -> None:
-        """Initialize a LightningDataModule for Potsdam2D based DataLoaders.
+        """Initialize a new LightningDataModule instance.
+
+        The Potsdam2D dataset contains images that are too large to pass
+        directly through a model. Instead, we randomly sample patches from image tiles
+        during training and chop up image tiles into patch grids during evaluation.
+        During training, the effective batch size is equal to
+        ``num_tiles_per_batch`` x ``num_patches_per_tile``.
 
         Args:
-            batch_size: The batch size to use in all created DataLoaders
-            num_workers: The number of workers to use in all created DataLoaders
-            val_split_pct: What percentage of the dataset to use as a validation set
+            num_tiles_per_batch: The number of image tiles to sample from during
+                training
+            num_patches_per_tile: The number of patches to randomly sample from each
+                image tile during training
+            patch_size: The size of each patch, either ``size`` or ``(height, width)``.
+                Should be a multiple of 32 for most segmentation architectures
+            val_split_pct: The percentage of the dataset to use as a validation set
+            num_workers: The number of workers to use for parallel data loading
             **kwargs: Additional keyword arguments passed to
                 :class:`~torchgeo.datasets.Potsdam2D`
+
+        .. versionchanged:: 0.4
+           *batch_size* was replaced by *num_tile_per_batch*, *num_patches_per_tile*,
+           and *patch_size*.
         """
         super().__init__()
-        self.batch_size = batch_size
-        self.num_workers = num_workers
+
+        self.num_tiles_per_batch = num_tiles_per_batch
+        self.num_patches_per_tile = num_patches_per_tile
+        self.patch_size = _to_tuple(patch_size)
         self.val_split_pct = val_split_pct
+        self.num_workers = num_workers
         self.kwargs = kwargs
 
-    def preprocess(self, sample: Dict[str, Any]) -> Dict[str, Any]:
-        """Transform a single sample from the Dataset.
-
-        Args:
-            sample: input image dictionary
-
-        Returns:
-            preprocessed sample
-        """
-        sample["image"] = sample["image"].float()
-        sample["image"] /= 255.0
-        return sample
+        self.train_transform = AugmentationSequential(
+            Normalize(mean=0.0, std=255.0),
+            _RandomNCrop(self.patch_size, self.num_patches_per_tile),
+            data_keys=["image", "mask"],
+        )
+        self.test_transform = AugmentationSequential(
+            Normalize(mean=0.0, std=255.0),
+            _ExtractTensorPatches(self.patch_size),
+            data_keys=["image", "mask"],
+        )
 
     def setup(self, stage: Optional[str] = None) -> None:
-        """Initialize the main ``Dataset`` objects.
+        """Initialize the main Dataset objects.
 
         This method is called once per GPU per run.
 
         Args:
             stage: stage to set up
         """
-        transforms = Compose([self.preprocess])
-
-        dataset = Potsdam2D(split="train", transforms=transforms, **self.kwargs)
-
-        self.train_dataset: Dataset[Any]
-        self.val_dataset: Dataset[Any]
-
-        if self.val_split_pct > 0.0:
-            self.train_dataset, self.val_dataset, _ = dataset_split(
-                dataset, val_pct=self.val_split_pct, test_pct=0.0
-            )
-        else:
-            self.train_dataset = dataset
-            self.val_dataset = dataset
-
-        self.test_dataset = Potsdam2D(
-            split="test", transforms=transforms, **self.kwargs
+        train_dataset = Potsdam2D(split="train", **self.kwargs)
+        self.train_dataset, self.val_dataset = dataset_split(
+            train_dataset, self.val_split_pct
         )
+        self.test_dataset = Potsdam2D(split="test", **self.kwargs)
 
-    def train_dataloader(self) -> DataLoader[Any]:
+    def train_dataloader(self) -> DataLoader[Dict[str, Tensor]]:
         """Return a DataLoader for training.
 
         Returns:
             training data loader
         """
         return DataLoader(
             self.train_dataset,
-            batch_size=self.batch_size,
+            batch_size=self.num_tiles_per_batch,
             num_workers=self.num_workers,
             shuffle=True,
         )
 
-    def val_dataloader(self) -> DataLoader[Any]:
+    def val_dataloader(self) -> DataLoader[Dict[str, Tensor]]:
         """Return a DataLoader for validation.
 
         Returns:
             validation data loader
         """
         return DataLoader(
-            self.val_dataset,
-            batch_size=self.batch_size,
-            num_workers=self.num_workers,
-            shuffle=False,
+            self.val_dataset, batch_size=1, num_workers=self.num_workers, shuffle=False
         )
 
-    def test_dataloader(self) -> DataLoader[Any]:
+    def test_dataloader(self) -> DataLoader[Dict[str, Tensor]]:
         """Return a DataLoader for testing.
 
         Returns:
             testing data loader
         """
         return DataLoader(
-            self.test_dataset,
-            batch_size=self.batch_size,
-            num_workers=self.num_workers,
-            shuffle=False,
+            self.test_dataset, batch_size=1, num_workers=self.num_workers, shuffle=False
         )
 
+    def on_after_batch_transfer(
+        self, batch: Dict[str, Tensor], dataloader_idx: int
+    ) -> Dict[str, Tensor]:
+        """Apply augmentations to batch after transferring to GPU.
+
+        Args:
+            batch: A batch of data that needs to be altered or augmented
+            dataloader_idx: The index of the dataloader to which the batch belongs
+
+        Returns:
+            A batch of data
+        """
+        # Kornia requires masks to have a channel dimension
+        batch["mask"] = rearrange(batch["mask"], "b h w -> b () h w")
+
+        if self.trainer:
+            if self.trainer.training:
+                batch = self.train_transform(batch)
+            elif self.trainer.validating or self.trainer.testing:
+                batch = self.test_transform(batch)
+
+        # Torchmetrics does not support masks with a channel dimension
+        batch["mask"] = rearrange(batch["mask"], "b () h w -> b h w")
+
+        return batch
+
     def plot(self, *args: Any, **kwargs: Any) -> plt.Figure:
         """Run :meth:`torchgeo.datasets.Potsdam2D.plot`.
 

torchgeo/datasets/potsdam.py

@@ -187,7 +187,7 @@ def _load_image(self, index: int) -> Tensor:
         path = self.files[index]["image"]
         with rasterio.open(path) as f:
             array = f.read()
-            tensor = torch.from_numpy(array)
+            tensor = torch.from_numpy(array).float()
             return tensor
 
     def _load_target(self, index: int) -> Tensor:

train.py

@@ -25,6 +25,7 @@
     LoveDADataModule,
     NAIPChesapeakeDataModule,
     NASAMarineDebrisDataModule,
+    Potsdam2DDataModule,
     RESISC45DataModule,
     SEN12MSDataModule,
     So2SatDataModule,
@@ -58,6 +59,7 @@
     "loveda": (SemanticSegmentationTask, LoveDADataModule),
     "naipchesapeake": (SemanticSegmentationTask, NAIPChesapeakeDataModule),
     "nasa_marine_debris": (ObjectDetectionTask, NASAMarineDebrisDataModule),
+    "potsdam2d": (SemanticSegmentationTask, Potsdam2DDataModule),
     "resisc45": (ClassificationTask, RESISC45DataModule),
     "sen12ms": (SemanticSegmentationTask, SEN12MSDataModule),
     "so2sat": (ClassificationTask, So2SatDataModule),