fix(image transforms): cleaning up image_transforms implementation in LeRobotDataset

src/lerobot/datasets/dataset_reader.py

@@ -72,6 +72,8 @@ class DatasetReader:
         self.episodes = episodes
         self._tolerance_s = tolerance_s
         self._video_backend = video_backend
+        if image_transforms is not None and not callable(image_transforms):
+            raise TypeError("image_transforms must be callable or None.")
         self._image_transforms = image_transforms
 
         self.hf_dataset: datasets.Dataset | None = None
@@ -83,6 +85,16 @@ class DatasetReader:
             check_delta_timestamps(delta_timestamps, meta.fps, tolerance_s)
             self.delta_indices = get_delta_indices(delta_timestamps, meta.fps)
 
+    def set_image_transforms(self, image_transforms: Callable | None) -> None:
+        """Replace the transform applied to visual observations."""
+        if image_transforms is not None and not callable(image_transforms):
+            raise TypeError("image_transforms must be callable or None.")
+        self._image_transforms = image_transforms
+
+    def clear_image_transforms(self) -> None:
+        """Remove the transform applied to visual observations."""
+        self._image_transforms = None
+
     def try_load(self) -> bool:
         """Attempt to load from local cache. Returns True if data is sufficient."""
         try:

src/lerobot/datasets/lerobot_dataset.py

@@ -194,8 +194,6 @@ class LeRobotDataset(torch.utils.data.Dataset):
         super().__init__()
         self.repo_id = repo_id
         self._requested_root = Path(root) if root else None
-        self.reader = None
-        self.set_image_transforms(image_transforms)
         self.delta_timestamps = delta_timestamps
         self.episodes = episodes
         self.tolerance_s = tolerance_s
@@ -225,6 +223,7 @@ class LeRobotDataset(torch.utils.data.Dataset):
             delta_timestamps=delta_timestamps,
             image_transforms=image_transforms,
         )
+        self.image_transforms = image_transforms
 
         # Load actual data
         if force_cache_sync or not self.reader.try_load():
@@ -480,15 +479,14 @@ class LeRobotDataset(torch.utils.data.Dataset):
 
     def set_image_transforms(self, image_transforms: Callable | None) -> None:
         """Replace the transform applied to visual observations."""
-        if image_transforms is not None and not callable(image_transforms):
+        self._ensure_reader().set_image_transforms(image_transforms)
-            raise TypeError("image_transforms must be callable or None.")
         self.image_transforms = image_transforms
-        if self.reader is not None:
-            self.reader._image_transforms = image_transforms
 
     def clear_image_transforms(self) -> None:
         """Remove the transform applied to visual observations."""
-        self.set_image_transforms(None)
+        if self.reader is not None:
+            self.reader.set_image_transforms(None)
+        self.image_transforms = None
 
     # ── Hub methods (stay on facade) ──────────────────────────────────