We are currently solving the following issue within our repository. Here is the issue text:
--- BEGIN ISSUE ---
Use pillow to replace opencv in reference evaluator
Caveat: https://github.com/python-pillow/Pillow/issues/6047#issuecomment-1038150443

cc @jcwchen 

--- END ISSUE ---

Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
--- BEGIN FILES ---
Path: `onnx/reference/ops/op_image_decoder.py`
Content:
```
1 # Copyright (c) ONNX Project Contributors
2 
3 # SPDX-License-Identifier: Apache-2.0
4 # pylint: disable=C0123,C3001,R0912,R0913,R0914,R1730,W0221,W0613
5 
6 import numpy as np
7 
8 from onnx.reference.op_run import OpRun
9 
10 
11 class ImageDecoder(OpRun):
12     def _run(  # type: ignore
13         self,
14         encoded,
15         pixel_format="RGB",
16     ):
17         try:
18             # pylint: disable=import-outside-toplevel`
19             import cv2
20         except ImportError as e:
21             raise ImportError(
22                 "opencv-python must be installed to use the reference implementation of the ImageDecoder operator"
23             ) from e
24         decoded = None
25         if pixel_format == "BGR":
26             decoded = cv2.imdecode(encoded, cv2.IMREAD_COLOR)
27         elif pixel_format == "RGB":
28             decoded = cv2.imdecode(encoded, cv2.IMREAD_COLOR)
29             decoded = cv2.cvtColor(decoded, cv2.COLOR_BGR2RGB)
30         elif pixel_format == "Grayscale":
31             decoded = cv2.imdecode(encoded, cv2.IMREAD_GRAYSCALE)
32             decoded = np.expand_dims(decoded, axis=2)  # (H, W) to (H, W, 1)
33         else:
34             raise RuntimeError(f"pixel_format={pixel_format!r} is not supported.")
35         return (decoded,)
36
```
--- END FILES ---

Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.

Here is an example:

```diff
diff --git a/examples/server_async.py b/examples/server_async.py
--- a/examples/server_async.py
+++ b/examples/server_async.py
@@ -313,4 +313,4 @@
 
 
 if __name__ == "__main__":
-    asyncio.run(run_async_server("."), debug=True)
+    asyncio.run(run_async_server(), debug=True)
diff --git a/examples/server_sync.py b/examples/server_sync.py
--- a/examples/server_sync.py
+++ b/examples/server_sync.py
@@ -313,5 +313,5 @@
 
 
 if __name__ == "__main__":
-    server = run_sync_server(".")
+    server = run_sync_server()
     server.shutdown()

```

diff --git a/onnx/reference/ops/op_image_decoder.py b/onnx/reference/ops/op_image_decoder.py
--- a/onnx/reference/ops/op_image_decoder.py
+++ b/onnx/reference/ops/op_image_decoder.py
@@ -1,7 +1,10 @@
 # Copyright (c) ONNX Project Contributors
 
 # SPDX-License-Identifier: Apache-2.0
-# pylint: disable=C0123,C3001,R0912,R0913,R0914,R1730,W0221,W0613
+
+from __future__ import annotations
+
+import io
 
 import numpy as np
 
@@ -9,27 +12,22 @@
 
 
 class ImageDecoder(OpRun):
-    def _run(  # type: ignore
-        self,
-        encoded,
-        pixel_format="RGB",
-    ):
+    def _run(self, encoded: np.ndarray, pixel_format="RGB") -> tuple[np.ndarray]:  # type: ignore
         try:
-            # pylint: disable=import-outside-toplevel`
-            import cv2
+            import PIL.Image  # pylint: disable=import-outside-toplevel
         except ImportError as e:
             raise ImportError(
-                "opencv-python must be installed to use the reference implementation of the ImageDecoder operator"
+                "Pillow must be installed to use the reference implementation of the ImageDecoder operator"
             ) from e
-        decoded = None
+        img = PIL.Image.open(io.BytesIO(encoded.tobytes()))
         if pixel_format == "BGR":
-            decoded = cv2.imdecode(encoded, cv2.IMREAD_COLOR)
+            decoded = np.array(img)[:, :, ::-1]
         elif pixel_format == "RGB":
-            decoded = cv2.imdecode(encoded, cv2.IMREAD_COLOR)
-            decoded = cv2.cvtColor(decoded, cv2.COLOR_BGR2RGB)
+            decoded = np.array(img)
         elif pixel_format == "Grayscale":
-            decoded = cv2.imdecode(encoded, cv2.IMREAD_GRAYSCALE)
+            img = img.convert("L")
+            decoded = np.array(img)
             decoded = np.expand_dims(decoded, axis=2)  # (H, W) to (H, W, 1)
         else:
-            raise RuntimeError(f"pixel_format={pixel_format!r} is not supported.")
+            raise ValueError(f"pixel_format={pixel_format!r} is not supported.")
         return (decoded,)

{"golden_diff": "diff --git a/onnx/reference/ops/op_image_decoder.py b/onnx/reference/ops/op_image_decoder.py\n--- a/onnx/reference/ops/op_image_decoder.py\n+++ b/onnx/reference/ops/op_image_decoder.py\n@@ -1,7 +1,10 @@\n # Copyright (c) ONNX Project Contributors\n \n # SPDX-License-Identifier: Apache-2.0\n-# pylint: disable=C0123,C3001,R0912,R0913,R0914,R1730,W0221,W0613\n+\n+from __future__ import annotations\n+\n+import io\n \n import numpy as np\n \n@@ -9,27 +12,22 @@\n \n \n class ImageDecoder(OpRun):\n-    def _run(  # type: ignore\n-        self,\n-        encoded,\n-        pixel_format=\"RGB\",\n-    ):\n+    def _run(self, encoded: np.ndarray, pixel_format=\"RGB\") -> tuple[np.ndarray]:  # type: ignore\n         try:\n-            # pylint: disable=import-outside-toplevel`\n-            import cv2\n+            import PIL.Image  # pylint: disable=import-outside-toplevel\n         except ImportError as e:\n             raise ImportError(\n-                \"opencv-python must be installed to use the reference implementation of the ImageDecoder operator\"\n+                \"Pillow must be installed to use the reference implementation of the ImageDecoder operator\"\n             ) from e\n-        decoded = None\n+        img = PIL.Image.open(io.BytesIO(encoded.tobytes()))\n         if pixel_format == \"BGR\":\n-            decoded = cv2.imdecode(encoded, cv2.IMREAD_COLOR)\n+            decoded = np.array(img)[:, :, ::-1]\n         elif pixel_format == \"RGB\":\n-            decoded = cv2.imdecode(encoded, cv2.IMREAD_COLOR)\n-            decoded = cv2.cvtColor(decoded, cv2.COLOR_BGR2RGB)\n+            decoded = np.array(img)\n         elif pixel_format == \"Grayscale\":\n-            decoded = cv2.imdecode(encoded, cv2.IMREAD_GRAYSCALE)\n+            img = img.convert(\"L\")\n+            decoded = np.array(img)\n             decoded = np.expand_dims(decoded, axis=2)  # (H, W) to (H, W, 1)\n         else:\n-            raise RuntimeError(f\"pixel_format={pixel_format!r} is not supported.\")\n+            raise ValueError(f\"pixel_format={pixel_format!r} is not supported.\")\n         return (decoded,)\n", "issue": "Use pillow to replace opencv in reference evaluator\nCaveat: https://github.com/python-pillow/Pillow/issues/6047#issuecomment-1038150443\r\n\r\ncc @jcwchen \n", "before_files": [{"content": "# Copyright (c) ONNX Project Contributors\n\n# SPDX-License-Identifier: Apache-2.0\n# pylint: disable=C0123,C3001,R0912,R0913,R0914,R1730,W0221,W0613\n\nimport numpy as np\n\nfrom onnx.reference.op_run import OpRun\n\n\nclass ImageDecoder(OpRun):\n    def _run(  # type: ignore\n        self,\n        encoded,\n        pixel_format=\"RGB\",\n    ):\n        try:\n            # pylint: disable=import-outside-toplevel`\n            import cv2\n        except ImportError as e:\n            raise ImportError(\n                \"opencv-python must be installed to use the reference implementation of the ImageDecoder operator\"\n            ) from e\n        decoded = None\n        if pixel_format == \"BGR\":\n            decoded = cv2.imdecode(encoded, cv2.IMREAD_COLOR)\n        elif pixel_format == \"RGB\":\n            decoded = cv2.imdecode(encoded, cv2.IMREAD_COLOR)\n            decoded = cv2.cvtColor(decoded, cv2.COLOR_BGR2RGB)\n        elif pixel_format == \"Grayscale\":\n            decoded = cv2.imdecode(encoded, cv2.IMREAD_GRAYSCALE)\n            decoded = np.expand_dims(decoded, axis=2)  # (H, W) to (H, W, 1)\n        else:\n            raise RuntimeError(f\"pixel_format={pixel_format!r} is not supported.\")\n        return (decoded,)\n", "path": "onnx/reference/ops/op_image_decoder.py"}], "after_files": [{"content": "# Copyright (c) ONNX Project Contributors\n\n# SPDX-License-Identifier: Apache-2.0\n\nfrom __future__ import annotations\n\nimport io\n\nimport numpy as np\n\nfrom onnx.reference.op_run import OpRun\n\n\nclass ImageDecoder(OpRun):\n    def _run(self, encoded: np.ndarray, pixel_format=\"RGB\") -> tuple[np.ndarray]:  # type: ignore\n        try:\n            import PIL.Image  # pylint: disable=import-outside-toplevel\n        except ImportError as e:\n            raise ImportError(\n                \"Pillow must be installed to use the reference implementation of the ImageDecoder operator\"\n            ) from e\n        img = PIL.Image.open(io.BytesIO(encoded.tobytes()))\n        if pixel_format == \"BGR\":\n            decoded = np.array(img)[:, :, ::-1]\n        elif pixel_format == \"RGB\":\n            decoded = np.array(img)\n        elif pixel_format == \"Grayscale\":\n            img = img.convert(\"L\")\n            decoded = np.array(img)\n            decoded = np.expand_dims(decoded, axis=2)  # (H, W) to (H, W, 1)\n        else:\n            raise ValueError(f\"pixel_format={pixel_format!r} is not supported.\")\n        return (decoded,)\n", "path": "onnx/reference/ops/op_image_decoder.py"}]}