[VLM] Support pan-and-scan for Gemma3 multi-modal processor (#14672)

Signed-off-by: Woosuk Kwon <woosuk.kwon@berkeley.edu>
Signed-off-by: DarkLight1337 <tlleungac@connect.ust.hk>
Signed-off-by: Roger Wang <ywang@roblox.com>
Co-authored-by: Woosuk Kwon <woosuk.kwon@berkeley.edu>
Co-authored-by: Roger Wang <ywang@roblox.com>

Author: 3 people

docs/source/models/supported_models.md

@@ -763,7 +763,7 @@ See [this page](#generative-models) for more information on how to use generativ
   * `google/gemma-3-4b-it`, `google/gemma-3-27b-it`, etc.
   * ✅︎
   * ✅︎
-  * ✅︎\*
+  * ⚠️
 - * `GLM4VForCausalLM`<sup>^</sup>
   * GLM-4V
   * T + I
@@ -856,12 +856,12 @@ See [this page](#generative-models) for more information on how to use generativ
   * ✅︎
   * ✅︎
 - * `PaliGemmaForConditionalGeneration`
-  * PaliGemma ⚠️, PaliGemma 2 ⚠️
+  * PaliGemma, PaliGemma 2
   * T + I<sup>E</sup>
   * `google/paligemma-3b-pt-224`, `google/paligemma-3b-mix-224`, `google/paligemma2-3b-ft-docci-448`, etc.
   *
   * ✅︎
-  * ✅︎
+  * ⚠️
 - * `Phi3VForCausalLM`
   * Phi-3-Vision, Phi-3.5-Vision
   * T + I<sup>E+</sup>
@@ -926,34 +926,15 @@ See [this page](#generative-models) for more information on how to use generativ
 <sup>E</sup> Pre-computed embeddings can be inputted for this modality.  
 <sup>+</sup> Multiple items can be inputted per text prompt for this modality.
 
-:::{warning}
-vLLM does not currently support PrefixLM attention mask, so our PaliGemma implementation uses regular causal attention, which causes the model output to be unstable.
-
-We may deprecate this model series in a future release.
-:::
-
-:::{note}
-`h2oai/h2ovl-mississippi-2b` will be available in V1 once we support backends other than FlashAttention.
-:::
-
-:::{note}
-To use `TIGER-Lab/Mantis-8B-siglip-llama3`, you have to pass `--hf_overrides '{"architectures": ["MantisForConditionalGeneration"]}'` when running vLLM.
-:::
-
-:::{note}
-The official `openbmb/MiniCPM-V-2` doesn't work yet, so we need to use a fork (`HwwwH/MiniCPM-V-2`) for now.
-For more details, please see: <gh-pr:4087#issuecomment-2250397630>
-:::
-
-:::{note}
-To use Qwen2.5-VL series models, you have to install Hugging Face Transformers library from source via `pip install git+https://github.com/huggingface/transformers`.
-:::
-
-:::{note}
+:::{important}
 To use Gemma3 series models, you have to install Hugging Face Transformers library from source via
 `pip install git+https://github.com/huggingface/transformers`.
-The earliest commit that supports this is [`50d3530aa04e7a7d003e6b255a98f79fd0447357`](https://github.com/huggingface/transformers/commit/50d3530aa04e7a7d003e6b255a98f79fd0447357).
 
+Pan-and-scan image pre-processing is currently supported on V0 (but not V1).
+You can enable it by passing `--mm-processor-kwargs '{"do_pan_and_scan": True}'`.
+:::
+
+:::{warning}
 Both V0 and V1 support `Gemma3ForConditionalGeneration` for text-only inputs.
 However, there are differences in how they handle text + image inputs:
 
@@ -969,9 +950,23 @@ V1 currently uses a simplified attention pattern:
 - Will be updated in the future to support the correct behavior
 
 This limitation exists because the model's mixed attention pattern (bidirectional for images, causal otherwise) is not yet supported by vLLM's attention backends.
+:::
+
+:::{note}
+`h2oai/h2ovl-mississippi-2b` will be available in V1 once we support backends other than FlashAttention.
+:::
 
-Additionally, vLLM's current Gemma 3 implementation does not support the pan-and-scan image pre-processing algorithm, which helps handle images with skewed aspect ratios by intelligently cropping them into multiple views.
-Without this feature, model performance may degrade when processing images that deviate significantly from square dimensions.
+:::{note}
+To use `TIGER-Lab/Mantis-8B-siglip-llama3`, you have to pass `--hf_overrides '{"architectures": ["MantisForConditionalGeneration"]}'` when running vLLM.
+:::
+
+:::{note}
+The official `openbmb/MiniCPM-V-2` doesn't work yet, so we need to use a fork (`HwwwH/MiniCPM-V-2`) for now.
+For more details, please see: <gh-pr:4087#issuecomment-2250397630>
+:::
+
+:::{warning}
+Our PaliGemma implementations have the same problem as Gemma 3 (see above) for both V0 and V1.
 :::
 
 ### Pooling Models

examples/offline_inference/vision_language.py

@@ -123,10 +123,14 @@ def run_gemma3(questions: list[str], modality: str):
     assert modality == "image"
     model_name = "google/gemma-3-4b-it"
 
-    llm = LLM(model=model_name,
-              max_model_len=2048,
-              max_num_seqs=2,
-              disable_mm_preprocessor_cache=args.disable_mm_preprocessor_cache)
+    llm = LLM(
+        model=model_name,
+        max_model_len=2048,
+        max_num_seqs=2,
+        # Default is False; setting it to True is not supported in V1 yet
+        mm_processor_kwargs={"do_pan_and_scan": True},
+        disable_mm_preprocessor_cache=args.disable_mm_preprocessor_cache,
+    )
 
     prompts = [("<bos><start_of_turn>user\n"
                 f"<start_of_image>{question}<end_of_turn>\n"

examples/offline_inference/vision_language_multi_image.py

@@ -83,10 +83,14 @@ def load_deepseek_vl2(question: str, image_urls: list[str]):
 def load_gemma3(question, image_urls: list[str]) -> ModelRequestData:
     model_name = "google/gemma-3-4b-it"
 
-    llm = LLM(model=model_name,
-              max_model_len=8192,
-              max_num_seqs=2,
-              limit_mm_per_prompt={"image": len(image_urls)})
+    llm = LLM(
+        model=model_name,
+        max_model_len=8192,
+        max_num_seqs=2,
+        # Default is False; setting it to True is not supported in V1 yet
+        mm_processor_kwargs={"do_pan_and_scan": True},
+        limit_mm_per_prompt={"image": len(image_urls)},
+    )
 
     placeholders = [{"type": "image", "image": url} for url in image_urls]
     messages = [{

tests/models/decoder_only/vision_language/test_models.py

@@ -9,7 +9,7 @@
 
 import pytest
 from packaging.version import Version
-from transformers import AutoModelForVision2Seq
+from transformers import AutoModelForPreTraining, AutoModelForVision2Seq
 from transformers import __version__ as TRANSFORMERS_VERSION
 
 from vllm.platforms import current_platform
@@ -234,6 +234,23 @@
         num_logprobs=10,
         image_size_factors=[(), (0.25,), (0.25, 0.25, 0.25), (0.25, 0.2, 0.15)],
     ),
+    "gemma3": VLMTestInfo(
+        models=["google/gemma-3-4b-it"],
+        test_type=(VLMTestType.IMAGE, VLMTestType.MULTI_IMAGE),
+        prompt_formatter=lambda img_prompt: f"<bos><start_of_turn>user\n{img_prompt}<end_of_turn>\n<start_of_turn>model\n", # noqa: E501
+        single_image_prompts=IMAGE_ASSETS.prompts({
+            "stop_sign": "<start_of_image>What's the content in the center of the image?",  # noqa: E501
+            "cherry_blossom": "<start_of_image>What is the season?",  # noqa: E501
+        }),
+        multi_image_prompt="<start_of_image><start_of_image>Describe the two images in detail.",  # noqa: E501
+        max_model_len=4096,
+        max_num_seqs=2,
+        # TODO: Use AutoModelForVision2Seq once transformers supports this
+        auto_cls=AutoModelForPreTraining,
+        dtype="bfloat16",
+        vllm_runner_kwargs={"mm_processor_kwargs": {"do_pan_and_scan": True}},
+        patch_hf_runner=model_utils.gemma3_patch_hf_runner,
+    ),
     "glm4v": VLMTestInfo(
         models=["THUDM/glm-4v-9b"],
         test_type=VLMTestType.IMAGE,

tests/models/decoder_only/vision_language/vlm_utils/model_utils.py

@@ -304,6 +304,18 @@ def processor(*args, text="", images=None, **kwargs):
     return hf_model
 
 
+def gemma3_patch_hf_runner(hf_model: HfRunner) -> HfRunner:
+    """Patches and returns an instance of the HfRunner to use for Gemma 3."""
+    hf_processor = hf_model.processor
+
+    def processor(*args, **kwargs):
+        return hf_processor(*args, do_pan_and_scan=True, **kwargs)
+
+    hf_model.processor = processor
+
+    return hf_model
+
+
 def glm_patch_hf_runner(hf_model: HfRunner) -> HfRunner:
     """Patches and returns an instance of the HfRunner to use for GLM4."""
     hf_processor = hf_model.processor

vllm/inputs/registry.py

@@ -348,7 +348,11 @@ def dummy_data_for_profiling(
                 dummy_factory = self._get_dummy_data_factory(model_cls)
             mm_counts = mm_registry.get_mm_limits_per_prompt(model_config)
             mm_processor_kwargs = get_allowed_kwarg_only_overrides(
-                dummy_factory, overrides=model_config.mm_processor_kwargs)
+                dummy_factory,
+                overrides=model_config.mm_processor_kwargs,
+                requires_kw_only=False,
+                allow_var_kwargs=True,
+            )
 
             dummy_data = dummy_factory(InputContext(model_config), seq_len,
                                        _MultiModalCounts(mm_counts),
@@ -381,6 +385,7 @@ def _default_input_processor(
         self,
         ctx: InputContext,
         inputs: ProcessorInputs,
+        **kwargs: object,
     ) -> ProcessorInputs:
         """The default input processor is a no-op."""
         return inputs
@@ -447,6 +452,8 @@ def process_input(self, model_config: "ModelConfig",
             model_config.mm_processor_kwargs,
             inputs.get("mm_processor_kwargs", {}),  # type: ignore
             processor,
+            requires_kw_only=False,
+            allow_var_kwargs=True,
         )
 
         processed_inputs = processor(