[diffusion]: add width/height passthrough for OpenAI image API (#19970)

python/sglang/multimodal_gen/runtime/entrypoints/openai/image_api.py

@@ -119,6 +119,8 @@ async def generations(
             request_id,
             prompt=request.prompt,
             size=request.size,
+            width=request.width,
+            height=request.height,
             num_outputs_per_prompt=max(1, min(int(request.n or 1), 10)),
             output_file_name=f"{request_id}.{ext}",
             output_path=output_dir,

python/sglang/multimodal_gen/runtime/entrypoints/openai/protocol.py

@@ -35,6 +35,8 @@ class ImageGenerationsRequest(BaseModel):
     output_format: Optional[str] = None  # png | jpeg | webp
     user: Optional[str] = None
     # SGLang extensions
+    width: Optional[int] = None
+    height: Optional[int] = None
     num_inference_steps: Optional[int] = None
     guidance_scale: Optional[float] = None
     true_cfg_scale: Optional[float] = (

python/sglang/multimodal_gen/runtime/entrypoints/openai/utils.py

@@ -109,8 +109,11 @@ def build_sampling_params(request_id: str, **kwargs) -> SamplingParams:
     if size:
         w, h = _parse_size(size)
         if w is not None:
-            kwargs.setdefault("width", w)
-            kwargs.setdefault("height", h)
+            # treat None dimensions as unset so parsed size can fill them
+            if kwargs.get("width") is None:
+                kwargs["width"] = w
+            if kwargs.get("height") is None:
+                kwargs["height"] = h
 
     # filter out None values to let SamplingParams defaults apply
     kwargs = {k: v for k, v in kwargs.items() if v is not None}