Validate features during add_frame + Add 2D-to-5D + Add string (#720)

lerobot/common/datasets/image_writer.py

@@ -38,22 +38,40 @@ def safe_stop_image_writer(func):
     return wrapper
 
 
-def image_array_to_image(image_array: np.ndarray) -> PIL.Image.Image:
+def image_array_to_pil_image(image_array: np.ndarray, range_check: bool = True) -> PIL.Image.Image:
     # TODO(aliberts): handle 1 channel and 4 for depth images
-    if image_array.ndim == 3 and image_array.shape[0] in [1, 3]:
+    if image_array.ndim != 3:
+        raise ValueError(f"The array has {image_array.ndim} dimensions, but 3 is expected for an image.")
+
+    if image_array.shape[0] == 3:
         # Transpose from pytorch convention (C, H, W) to (H, W, C)
         image_array = image_array.transpose(1, 2, 0)
+
+    elif image_array.shape[-1] != 3:
+        raise NotImplementedError(
+            f"The image has {image_array.shape[-1]} channels, but 3 is required for now."
+        )
+
     if image_array.dtype != np.uint8:
-        # Assume the image is in [0, 1] range for floating-point data
-        image_array = np.clip(image_array, 0, 1)
+        if range_check:
+            max_ = image_array.max().item()
+            min_ = image_array.min().item()
+            if max_ > 1.0 or min_ < 0.0:
+                raise ValueError(
+                    "The image data type is float, which requires values in the range [0.0, 1.0]. "
+                    f"However, the provided range is [{min_}, {max_}]. Please adjust the range or "
+                    "provide a uint8 image with values in the range [0, 255]."
+                )
+
         image_array = (image_array * 255).astype(np.uint8)
+
     return PIL.Image.fromarray(image_array)
 
 
 def write_image(image: np.ndarray | PIL.Image.Image, fpath: Path):
     try:
         if isinstance(image, np.ndarray):
-            img = image_array_to_image(image)
+            img = image_array_to_pil_image(image)
         elif isinstance(image, PIL.Image.Image):
             img = image
         else: