Make ImageProcessorMixin compatible with subfolder kwarg (#21725)

* Add subfolder support

* Add kwarg docstring

* formatting fix

* Add test

src/transformers/image_processing_utils.py

@@ -128,6 +128,9 @@ class ImageProcessingMixin(PushToHubMixin):
                 functions returns a `Tuple(image_processor, unused_kwargs)` where *unused_kwargs* is a dictionary
                 consisting of the key/value pairs whose keys are not image processor attributes: i.e., the part of
                 `kwargs` which has not been used to update `image_processor` and is otherwise ignored.
+            subfolder (`str`, *optional*, defaults to `""`):
+                In case the relevant files are located inside a subfolder of the model repo on huggingface.co, you can
+                specify the folder name here.
             kwargs (`Dict[str, Any]`, *optional*):
                 The values in kwargs of any keys which are image processor attributes will be used to override the
                 loaded values. Behavior concerning key/value pairs whose keys are *not* image processor attributes is
@@ -221,6 +224,9 @@ class ImageProcessingMixin(PushToHubMixin):
         Parameters:
             pretrained_model_name_or_path (`str` or `os.PathLike`):
                 The identifier of the pre-trained checkpoint from which we want the dictionary of parameters.
+            subfolder (`str`, *optional*, defaults to `""`):
+                In case the relevant files are located inside a subfolder of the model repo on huggingface.co, you can
+                specify the folder name here.
 
         Returns:
             `Tuple[Dict, Dict]`: The dictionary(ies) that will be used to instantiate the image processor object.
@@ -232,6 +238,7 @@ class ImageProcessingMixin(PushToHubMixin):
         use_auth_token = kwargs.pop("use_auth_token", None)
         local_files_only = kwargs.pop("local_files_only", False)
         revision = kwargs.pop("revision", None)
+        subfolder = kwargs.pop("subfolder", "")
 
         from_pipeline = kwargs.pop("_from_pipeline", None)
         from_auto_class = kwargs.pop("_from_auto", False)
@@ -269,6 +276,7 @@ class ImageProcessingMixin(PushToHubMixin):
                     use_auth_token=use_auth_token,
                     user_agent=user_agent,
                     revision=revision,
+                    subfolder=subfolder,
                 )
             except EnvironmentError:
                 # Raise any environment error raise by `cached_file`. It will have a helpful error message adapted to

tests/test_image_processing_common.py

@@ -311,3 +311,14 @@ class ImageProcessorPushToHubTester(unittest.TestCase):
         )
         # Can't make an isinstance check because the new_image_processor is from the CustomImageProcessor class of a dynamic module
         self.assertEqual(new_image_processor.__class__.__name__, "CustomImageProcessor")
+
+    def test_image_processor_from_pretrained_subfolder(self):
+        with self.assertRaises(OSError):
+            # config is in subfolder, the following should not work without specifying the subfolder
+            _ = AutoImageProcessor.from_pretrained("hf-internal-testing/stable-diffusion-all-variants")
+
+        config = AutoImageProcessor.from_pretrained(
+            "hf-internal-testing/stable-diffusion-all-variants", subfolder="feature_extractor"
+        )
+
+        self.assertIsNotNone(config)