feat(datasets): improve image transform support (#2885)

* improve image transform support

* add tests

* Add stricter transform check and extra test

* improve subclass check

src/lerobot/datasets/transforms.py

@@ -216,16 +216,17 @@ class ImageTransformsConfig:
 
 
 def make_transform_from_config(cfg: ImageTransformConfig):
-    if cfg.type == "Identity":
-        return v2.Identity(**cfg.kwargs)
-    elif cfg.type == "ColorJitter":
-        return v2.ColorJitter(**cfg.kwargs)
-    elif cfg.type == "SharpnessJitter":
+    if cfg.type == "SharpnessJitter":
         return SharpnessJitter(**cfg.kwargs)
-    elif cfg.type == "RandomAffine":
-        return v2.RandomAffine(**cfg.kwargs)
-    else:
-        raise ValueError(f"Transform '{cfg.type}' is not valid.")
+
+    transform_cls = getattr(v2, cfg.type, None)
+    if isinstance(transform_cls, type) and issubclass(transform_cls, Transform):
+        return transform_cls(**cfg.kwargs)
+
+    raise ValueError(
+        f"Transform '{cfg.type}' is not valid. It must be a class in "
+        f"torchvision.transforms.v2 or 'SharpnessJitter'."
+    )
 
 
 class ImageTransforms(Transform):

tests/datasets/test_image_transforms.py

@@ -390,6 +390,30 @@ def test_sharpness_jitter_invalid_range_max_smaller():
         SharpnessJitter((2.0, 0.1))
 
 
+def test_make_transform_from_config_with_v2_resize(img_tensor_factory):
+    img_tensor = img_tensor_factory()
+    tf_cfg = ImageTransformConfig(type="Resize", kwargs={"size": (32, 32)})
+    tf = make_transform_from_config(tf_cfg)
+    assert isinstance(tf, v2.Resize)
+    output = tf(img_tensor)
+    assert output.shape[-2:] == (32, 32)
+
+
+def test_make_transform_from_config_with_v2_identity(img_tensor_factory):
+    img_tensor = img_tensor_factory()
+    tf_cfg = ImageTransformConfig(type="Identity", kwargs={})
+    tf = make_transform_from_config(tf_cfg)
+    assert isinstance(tf, v2.Identity)
+    output = tf(img_tensor)
+    assert output.shape == img_tensor.shape
+
+
+def test_make_transform_from_config_invalid_type():
+    tf_cfg = ImageTransformConfig(type="NotARealTransform", kwargs={})
+    with pytest.raises(ValueError, match="not valid"):
+        make_transform_from_config(tf_cfg)
+
+
 def test_save_all_transforms(img_tensor_factory, tmp_path):
     img_tensor = img_tensor_factory()
     tf_cfg = ImageTransformsConfig(enable=True)