Re-submit: Fix: Proper RGBA -> RGB conversion for PIL images. (#18569)

Signed-off-by: Chenheli Hua <huachenheli@outlook.com>

tests/models/multimodal/generation/test_interleaved.py

@@ -4,6 +4,7 @@ import pytest
 
 from vllm.assets.image import ImageAsset
 from vllm.assets.video import VideoAsset
+from vllm.multimodal.image import convert_image_mode
 
 models = ["llava-hf/llava-onevision-qwen2-0.5b-ov-hf"]
 
@@ -26,8 +27,9 @@ def test_models(vllm_runner, model, dtype: str, max_tokens: int) -> None:
     give the same result.
     """
 
-    image_cherry = ImageAsset("cherry_blossom").pil_image.convert("RGB")
-    image_stop = ImageAsset("stop_sign").pil_image.convert("RGB")
+    image_cherry = convert_image_mode(
+        ImageAsset("cherry_blossom").pil_image, "RGB")
+    image_stop = convert_image_mode(ImageAsset("stop_sign").pil_image, "RGB")
     images = [image_cherry, image_stop]
     video = VideoAsset(name="baby_reading", num_frames=16).np_ndarrays