fix: normalize NumPy image outputs

Signed-off-by: Hongsheng Liu <liuhongsheng4@huawei.com>

tests/diffusion/test_image_output.py

@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+
+import numpy as np
+import pytest
+from PIL import Image
+
+from vllm_omni.diffusion.utils.image_output import extract_images_from_outputs
+from vllm_omni.outputs import OmniRequestOutput
+
+pytestmark = [pytest.mark.diffusion, pytest.mark.core_model, pytest.mark.cpu]
+
+
+@pytest.mark.parametrize(
+    ("payload", "expected_pixel"),
+    [
+        (np.array([[[-1.0, 0.0, 1.0]]], dtype=np.float32), (0, 127, 255)),
+        (np.array([[[0, 128, 255]]], dtype=np.uint8), (0, 128, 255)),
+    ],
+)
+def test_extract_images_normalizes_numpy_payload(
+    payload: np.ndarray,
+    expected_pixel: tuple[int, int, int],
+    tmp_path,
+) -> None:
+    output = OmniRequestOutput(images=[payload])
+
+    [image] = extract_images_from_outputs(output)
+
+    assert isinstance(image, Image.Image)
+    assert image.mode == "RGB"
+    assert image.size == (1, 1)
+    assert image.getpixel((0, 0)) == expected_pixel
+
+    output_path = tmp_path / "image.png"
+    image.save(output_path)
+    assert output_path.is_file()