[diffusion] feat: allows quality adjustment of generated images/videos (#17937)

docs/diffusion/api/openai_api.md

@@ -393,3 +393,26 @@ Notes:
     curl -X POST http://localhost:30010/v1/set_lora -d '{"lora_nickname": "lora_b", "lora_path": "path/to/B"}'
     ```
 5.  Generate with LoRA B...
+
+### Adjust Output Quality
+
+The server supports adjusting output quality and compression levels for both image and video generation through the `output-quality` and `output-compression` parameters.
+
+#### Parameters
+
+- **`output-quality`** (string, optional): Preset quality level that automatically sets compression. **Default is `"default"`**. Valid values:
+  - `"maximum"`: Highest quality (100)
+  - `"high"`: High quality (90)
+  - `"medium"`: Medium quality (55)
+  - `"low"`: Lower quality (35)
+  - `"default"`: Auto-adjust based on media type (50 for video, 75 for image)
+
+- **`output-compression`** (integer, optional): Direct compression level override (0-100). **Default is `None`**. When provided (not `None`), takes precedence over `output-quality`.
+  - `0`: Lowest quality, smallest file size
+  - `100`: Highest quality, largest file size
+
+#### Notes
+
+- **Precedence**: When both `output-quality` and `output-compression` are provided, `output-compression` takes precedence
+- **Format Support**: Quality settings apply to JPEG, and video formats. PNG uses lossless compression and ignores these settings
+- **File Size vs Quality**: Lower compression values (or "low" quality preset) produce smaller files but may show visible artifacts

python/sglang/multimodal_gen/configs/sample/sampling_params.py

@@ -97,6 +97,8 @@ class SamplingParams:
     prompt_path: str | None = None
     output_path: str | None = None
     output_file_name: str | None = None
+    output_quality: str | None = "default"
+    output_compression: int | None = None
 
     # Batch info
     num_outputs_per_prompt: int = 1
@@ -207,6 +209,12 @@ class SamplingParams:
         if self.height is None:
             self.height_not_provided = True
 
+        # Handle output_quality to output_compression conversion
+        if self.output_compression is None and self.output_quality is not None:
+            self.output_compression = self._adjust_output_quality(
+                self.output_quality, self.data_type
+            )
+
         self._validate()
 
         # Allow env var to override num_inference_steps (for faster CI testing on AMD)
@@ -214,6 +222,13 @@ class SamplingParams:
         if env_steps is not None and self.num_inference_steps is not None:
             self.num_inference_steps = int(env_steps)
 
+    def _adjust_output_quality(self, output_quality: str, data_type: DataType) -> int:
+        """Convert output_quality string to compression level."""
+        output_quality_mapper = {"maximum": 100, "high": 90, "medium": 55, "low": 35}
+        if output_quality == "default":
+            return 50 if data_type == DataType.VIDEO else 75
+        return output_quality_mapper.get(output_quality)
+
     def _validate(self):
         """
         check if the sampling params is correct by itself
@@ -567,6 +582,18 @@ class SamplingParams:
             default=SamplingParams.output_file_name,
             help="Name of the output file",
         )
+        parser.add_argument(
+            "--output-quality",
+            type=str,
+            default=SamplingParams.output_quality,
+            help="Output quality setting (default, low, medium, high, maximum)",
+        )
+        parser.add_argument(
+            "--output-compression",
+            type=int,
+            default=SamplingParams.output_compression,
+            help="Output compression level (0-100, higher means better quality but larger file size)",
+        )
         parser.add_argument(
             "--num-outputs-per-prompt",
             type=int,

python/sglang/multimodal_gen/runtime/entrypoints/diffusion_generator.py

@@ -277,6 +277,7 @@ class DiffGenerator:
                         samples_out=samples_out,
                         audios_out=audios_out,
                         frames_out=frames_out,
+                        output_compression=req.output_compression,
                     )
 
                     for output_idx in range(len(samples_out)):

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

@@ -22,6 +22,7 @@ from sglang.multimodal_gen.runtime.entrypoints.openai.stores import IMAGE_STORE
 from sglang.multimodal_gen.runtime.entrypoints.openai.utils import (
     _parse_size,
     add_common_data_to_response,
+    adjust_output_quality,
     merge_image_input_list,
     process_generation_batch,
     save_image_to_path,
@@ -63,6 +64,7 @@ def _build_sampling_params_from_request(
     negative_prompt: Optional[str] = None,
     enable_teacache: Optional[bool] = None,
     num_frames: int = 1,
+    output_compression: Optional[int] = None,
 ) -> SamplingParams:
     if size is None:
         width, height = None, None
@@ -90,6 +92,11 @@ def _build_sampling_params_from_request(
         **({"guidance_scale": guidance_scale} if guidance_scale is not None else {}),
         **({"negative_prompt": negative_prompt} if negative_prompt is not None else {}),
         **({"true_cfg_scale": true_cfg_scale} if true_cfg_scale is not None else {}),
+        **(
+            {"output_compression": output_compression}
+            if output_compression is not None
+            else {}
+        ),
     )
 
     if num_inference_steps is not None:
@@ -122,11 +129,16 @@ async def generations(
         true_cfg_scale=request.true_cfg_scale,
         negative_prompt=request.negative_prompt,
         enable_teacache=request.enable_teacache,
+        output_compression=request.output_compression,
     )
     batch = prepare_request(
         server_args=get_global_server_args(),
         sampling_params=sampling,
     )
+    if batch.output_compression is None:
+        batch.output_compression = adjust_output_quality(
+            request.output_quality, batch.data_type
+        )
     # Add diffusers_kwargs if provided
     if request.diffusers_kwargs:
         batch.extra["diffusers_kwargs"] = request.diffusers_kwargs
@@ -217,6 +229,8 @@ async def edits(
     guidance_scale: Optional[float] = Form(None),
     true_cfg_scale: Optional[float] = Form(None),
     num_inference_steps: Optional[int] = Form(None),
+    output_quality: Optional[str] = Form("default"),
+    output_compression: Optional[int] = Form(None),
     enable_teacache: Optional[bool] = Form(False),
     num_frames: int = Form(1),
 ):
@@ -264,12 +278,16 @@ async def edits(
         num_inference_steps=num_inference_steps,
         enable_teacache=enable_teacache,
         num_frames=num_frames,
+        output_compression=output_compression,
     )
     batch = prepare_request(
         server_args=get_global_server_args(),
         sampling_params=sampling,
     )
-
+    if batch.output_compression is None:
+        batch.output_compression = adjust_output_quality(
+            output_quality, batch.data_type
+        )
     save_file_path_list, result = await process_generation_batch(
         async_scheduler_client, batch
     )

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

@@ -43,6 +43,8 @@ class ImageGenerationsRequest(BaseModel):
     seed: Optional[int] = 1024
     generator_device: Optional[str] = "cuda"
     negative_prompt: Optional[str] = None
+    output_quality: Optional[str] = "default"
+    output_compression: Optional[int] = None
     enable_teacache: Optional[bool] = False
     diffusers_kwargs: Optional[Dict[str, Any]] = None  # kwargs for diffusers backend
 
@@ -88,6 +90,8 @@ class VideoGenerationsRequest(BaseModel):
     )
     negative_prompt: Optional[str] = None
     enable_teacache: Optional[bool] = False
+    output_quality: Optional[str] = "default"
+    output_compression: Optional[int] = None
     output_path: Optional[str] = None
     diffusers_kwargs: Optional[Dict[str, Any]] = None  # kwargs for diffusers backend
 

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

@@ -21,6 +21,8 @@ from sglang.multimodal_gen.runtime.utils.logging_utils import (
 
 logger = init_logger(__name__)
 
+OUTPUT_QUALITY_MAPPER = {"maximum": 100, "high": 90, "medium": 55, "low": 35}
+
 
 @dataclasses.dataclass
 class SetLoraReq:
@@ -237,6 +239,7 @@ async def process_generation_batch(
                     ),
                     audio=result.audio,
                     audio_sample_rate=audio_sample_rate,
+                    output_compression=batch.output_compression,
                 )
             else:
                 save_file_path_list = save_outputs(
@@ -251,6 +254,7 @@ async def process_generation_batch(
                         )
                     ),
                     audio_sample_rate=audio_sample_rate,
+                    output_compression=batch.output_compression,
                 )
 
     total_time = time.perf_counter() - total_start_time
@@ -302,3 +306,9 @@ def add_common_data_to_response(
     response["id"] = request_id
 
     return response
+
+
+def adjust_output_quality(output_quality: str, data_type: DataType = None) -> int:
+    if output_quality == "default":
+        return 50 if data_type == DataType.VIDEO else 75
+    return OUTPUT_QUALITY_MAPPER.get(output_quality, None)

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

@@ -32,6 +32,7 @@ from sglang.multimodal_gen.runtime.entrypoints.openai.stores import VIDEO_STORE
 from sglang.multimodal_gen.runtime.entrypoints.openai.utils import (
     _parse_size,
     add_common_data_to_response,
+    adjust_output_quality,
     merge_image_input_list,
     process_generation_batch,
     save_image_to_path,
@@ -88,6 +89,8 @@ def _build_sampling_params_from_request(
         sampling_kwargs["enable_teacache"] = request.enable_teacache
     if request.output_path is not None:
         sampling_kwargs["output_path"] = request.output_path
+    if request.output_compression is not None:
+        sampling_kwargs["output_compression"] = request.output_compression
     sampling_params = SamplingParams.from_user_sampling_params_args(
         model_path=server_args.model_path,
         server_args=server_args,
@@ -173,6 +176,8 @@ async def create_video(
     guidance_scale: Optional[float] = Form(None),
     num_inference_steps: Optional[int] = Form(None),
     enable_teacache: Optional[bool] = Form(False),
+    output_quality: Optional[str] = Form("default"),
+    output_compression: Optional[int] = Form(None),
     extra_body: Optional[str] = Form(None),
 ):
     content_type = request.headers.get("content-type", "").lower()
@@ -232,6 +237,8 @@ async def create_video(
             negative_prompt=negative_prompt,
             num_inference_steps=num_inference_steps,
             enable_teacache=enable_teacache,
+            output_compression=output_compression,
+            output_quality=output_quality,
             **(
                 {"guidance_scale": guidance_scale} if guidance_scale is not None else {}
             ),
@@ -293,6 +300,10 @@ async def create_video(
         server_args=server_args,
         sampling_params=sampling_params,
     )
+    if batch.output_compression is None:
+        batch.output_compression = adjust_output_quality(
+            req.output_quality, batch.data_type
+        )
     # Add diffusers_kwargs if provided
     if req.diffusers_kwargs:
         batch.extra["diffusers_kwargs"] = req.diffusers_kwargs

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

@@ -266,6 +266,7 @@ def save_outputs(
     samples_out: Optional[list[Any]] = None,
     audios_out: Optional[list[Any]] = None,
     frames_out: Optional[list[Any]] = None,
+    output_compression: Optional[int] = None,
 ) -> list[str]:
     """Save outputs to files and return the list of file paths."""
     output_paths: list[str] = []
@@ -281,6 +282,7 @@ def save_outputs(
             save_output,
             save_file_path,
             audio_sample_rate=audio_sample_rate,
+            output_compression=output_compression,
         )
         if samples_out is not None:
             samples_out.append(sample)
@@ -307,6 +309,7 @@ def post_process_sample(
     save_output: bool = True,
     save_file_path: Optional[str] = None,
     audio_sample_rate: Optional[int] = None,
+    output_compression: Optional[int] = None,
 ):
     """
     Process sample output and save video if necessary
@@ -352,8 +355,9 @@ def post_process_sample(
         if save_file_path:
             os.makedirs(os.path.dirname(save_file_path), exist_ok=True)
             if data_type == DataType.VIDEO:
-                # TODO: make this configurable
+                quality = (
-                quality = 5
+                    output_compression / 10 if output_compression is not None else 5
+                )
                 imageio.mimsave(
                     save_file_path,
                     frames,
@@ -372,7 +376,7 @@ def post_process_sample(
                 )
 
             else:
-                quality = 75
+                quality = output_compression if output_compression is not None else 75
                 if len(frames) > 1:
                     for i, image in enumerate(frames):
                         parts = save_file_path.rsplit(".", 1)

python/sglang/multimodal_gen/runtime/managers/gpu_worker.py

@@ -227,6 +227,7 @@ class GPUWorker:
                     lambda idx: req.output_file_path(len(output_batch.output), idx),
                     audio=output_batch.audio,
                     audio_sample_rate=output_batch.audio_sample_rate,
+                    output_compression=req.output_compression,
                 )
                 output_batch.output_file_paths = output_paths
                 output_batch.output = None