fix(signle channel squeeze): fixing single channel squeezing

src/lerobot/datasets/depth_utils.py

@@ -36,6 +36,7 @@ from lerobot.configs.video import (
     DEPTH_QMAX,
 )
 
+from .image_writer import squeeze_single_channel
 from .pyav_utils import write_u16_plane
 
 _MM_PER_METRE = 1000.0
@@ -119,8 +120,7 @@ def quantize_depth(
         depth = depth.detach().cpu().numpy()
 
     # Squeeze single-channel dim: (H, W, 1) or (1, H, W) → (H, W)
-    if depth.ndim == 3 and (depth.shape[-1] == 1 or depth.shape[0] == 1):
-        depth = depth.squeeze()
+    depth = squeeze_single_channel(depth)
 
     depth_f, resolved_unit = _depth_input_to_float32_and_unit(depth, input_unit=input_unit)
 

src/lerobot/datasets/image_writer.py

@@ -41,6 +41,19 @@ def safe_stop_image_writer(func):
     return wrapper
 
 
+def squeeze_single_channel(array: np.ndarray) -> np.ndarray:
+    """Drop a leading or trailing singleton channel dim: ``(1, H, W)`` / ``(H, W, 1)`` -> ``(H, W)``.
+
+    Unlike ``array.squeeze()``, this only removes the channel axis, never an ``H`` or ``W`` of size 1.
+    """
+    if array.ndim == 3:
+        if array.shape[0] == 1:
+            return array[0]
+        if array.shape[-1] == 1:
+            return array[..., 0]
+    return array
+
+
 def image_array_to_pil_image(image_array: np.ndarray, range_check: bool = True) -> PIL.Image.Image:
     """Convert a NumPy array to a PIL Image, preserving precision for grayscale.
 
@@ -62,11 +75,7 @@ def image_array_to_pil_image(image_array: np.ndarray, range_check: bool = True)
 
     # Squeeze 3D single-channel inputs to 2D so depth maps work whether the
     # caller emits (H, W), (1, H, W), or (H, W, 1).
-    if image_array.ndim == 3:
-        if image_array.shape[0] == 1:
-            image_array = image_array[0]
-        elif image_array.shape[-1] == 1:
-            image_array = image_array[..., 0]
+    image_array = squeeze_single_channel(image_array)
 
     if image_array.ndim == 2:
         if image_array.dtype not in [np.uint16, np.float32]:
@@ -112,7 +121,8 @@ def save_kwargs_for_path(fpath: Path, compress_level: int) -> dict:
         return {"compress_level": compress_level}
     if suffix in (".tif", ".tiff"):
         return {"compression": "raw"}
-    return {}
+    else:
+        raise ValueError(f"Unsupported image file extension: {suffix}")
 
 
 def write_image(image: np.ndarray | PIL.Image.Image, fpath: Path, compress_level: int = 1):