[Frontend] support image embeds (#13955)

Signed-off-by: chaunceyjiang <chaunceyjiang@gmail.com>

docs/source/serving/multimodal_inputs.md

@@ -462,4 +462,69 @@ export VLLM_AUDIO_FETCH_TIMEOUT=<timeout>
 
 ### Embedding Inputs
 
-TBD
+To input pre-computed embeddings belonging to a data type (i.e. image, video, or audio) directly to the language model,
+pass a tensor of shape to the corresponding field of the multi-modal dictionary.
+#### Image Embedding Inputs
+For image embeddings, you can pass the base64-encoded tensor to the `image_embeds` field.
+The following example demonstrates how to pass image embeddings to the OpenAI server:
+
+```python
+image_embedding = torch.load(...)
+grid_thw = torch.load(...) # Required by Qwen/Qwen2-VL-2B-Instruct
+
+buffer = io.BytesIO()
+torch.save(image_embedding, buffer)
+buffer.seek(0)
+binary_data = buffer.read()
+base64_image_embedding = base64.b64encode(binary_data).decode('utf-8')
+
+client = OpenAI(
+    # defaults to os.environ.get("OPENAI_API_KEY")
+    api_key=openai_api_key,
+    base_url=openai_api_base,
+)
+
+# Basic usage - this is equivalent to the LLaVA example for offline inference
+model = "llava-hf/llava-1.5-7b-hf"
+embeds =  {
+    "type": "image_embeds",
+    "image_embeds": f"{base64_image_embedding}" 
+}
+
+# Pass additional parameters (available to Qwen2-VL and MiniCPM-V)
+model = "Qwen/Qwen2-VL-2B-Instruct"
+embeds =  {
+    "type": "image_embeds",
+    "image_embeds": {
+        "image_embeds": f"{base64_image_embedding}" , # Required
+        "image_grid_thw": f"{base64_image_grid_thw}"  # Required by Qwen/Qwen2-VL-2B-Instruct
+    },
+}
+model = "openbmb/MiniCPM-V-2_6"
+embeds =  {
+    "type": "image_embeds",
+    "image_embeds": {
+        "image_embeds": f"{base64_image_embedding}" , # Required
+        "image_sizes": f"{base64_image_sizes}"  # Required by openbmb/MiniCPM-V-2_6
+    },
+}
+chat_completion = client.chat.completions.create(
+    messages=[
+    {"role": "system", "content": "You are a helpful assistant."},
+    {"role": "user", "content": [
+        {
+            "type": "text",
+            "text": "What's in this image?",
+        },
+        embeds,
+        ],
+    },
+],
+    model=model,
+)
+```
+
+:::{note}
+Only one message can contain `{"type": "image_embeds"}`.
+If used with a model that requires additional parameters, you must also provide a tensor for each of them, e.g. `image_grid_thw`, `image_sizes`, etc.
+:::

vllm/entrypoints/chat_utils.py

@@ -56,6 +56,17 @@ class ChatCompletionContentPartAudioParam(TypedDict, total=False):
     """The type of the content part."""
 
 
+class ChatCompletionContentPartImageEmbedsParam(TypedDict, total=False):
+    image_embeds: Required[Union[str, dict[str, str]]]
+    """
+    The image embeddings. It can be either:
+    - A single base64 string.
+    - A dictionary where each value is a base64 string.
+    """
+    type: Required[Literal["image_embeds"]]
+    """The type of the content part."""
+
+
 class VideoURL(TypedDict, total=False):
     url: Required[str]
     """
@@ -109,6 +120,7 @@ ChatCompletionContentPartParam: TypeAlias = Union[
     ChatCompletionContentPartInputAudioParam,
     ChatCompletionContentPartVideoParam, ChatCompletionContentPartRefusalParam,
     CustomChatCompletionContentSimpleImageParam,
+    ChatCompletionContentPartImageEmbedsParam,
     CustomChatCompletionContentSimpleAudioParam,
     CustomChatCompletionContentSimpleVideoParam, str]
 
@@ -350,7 +362,7 @@ def resolve_chat_template_content_format(
     return detected_format
 
 
-ModalityStr = Literal["image", "audio", "video"]
+ModalityStr = Literal["image", "audio", "video", "image_embeds"]
 _T = TypeVar("_T")
 
 
@@ -391,7 +403,7 @@ class BaseMultiModalItemTracker(ABC, Generic[_T]):
         hf_config = self._model_config.hf_config
         model_type = hf_config.model_type
 
-        if modality == "image":
+        if modality in ["image", "image_embeds"]:
             if model_type == "phi3_v":
                 # Workaround since this token is not defined in the tokenizer
                 return f"<|image_{current_count}|>"
@@ -470,10 +482,27 @@ class BaseMultiModalItemTracker(ABC, Generic[_T]):
 class MultiModalItemTracker(BaseMultiModalItemTracker[object]):
 
     def all_mm_data(self) -> Optional[MultiModalDataDict]:
-        if self._items_by_modality:
+        if not self._items_by_modality:
-            return dict(self._items_by_modality)
+            return None
+        mm_inputs = {}
+        items_by_modality = dict(self._items_by_modality)
+        if "image" in items_by_modality and "image_embeds" in items_by_modality:
+            raise ValueError(\
+                "Mixing raw image and embedding inputs is not allowed")
 
-        return None
+        if "image_embeds" in items_by_modality:
+            image_embeds_lst = items_by_modality["image_embeds"]
+            if len(image_embeds_lst) > 1:
+                raise ValueError(\
+                    "Only one message can have {'type': 'image_embeds'}")
+            mm_inputs["image"] = image_embeds_lst[0]
+        elif "image" in items_by_modality:
+            mm_inputs["image"] = items_by_modality["image"] # A list of images
+        elif "audio" in items_by_modality:
+            mm_inputs["audio"] = items_by_modality["audio"] # A list of audios
+        elif "video" in items_by_modality:
+            mm_inputs["video"] = items_by_modality["video"] # A list of videos
+        return mm_inputs
 
     def create_parser(self) -> "BaseMultiModalContentParser":
         return MultiModalContentParser(self)
@@ -482,13 +511,31 @@ class MultiModalItemTracker(BaseMultiModalItemTracker[object]):
 class AsyncMultiModalItemTracker(BaseMultiModalItemTracker[Awaitable[object]]):
 
     async def all_mm_data(self) -> Optional[MultiModalDataDict]:
-        if self._items_by_modality:
+        if not self._items_by_modality:
-            return {
+            return None
+        mm_inputs = {}
+        items_by_modality = {
                 modality: await asyncio.gather(*items)
                 for modality, items in self._items_by_modality.items()
             }
 
-        return None
+        if "image" in items_by_modality and "image_embeds" in items_by_modality:
+            raise ValueError(
+                "Mixing raw image and embedding inputs is not allowed")
+
+        if "image_embeds" in items_by_modality:
+            image_embeds_lst = items_by_modality["image_embeds"]
+            if len(image_embeds_lst) > 1:
+                raise ValueError(
+                    "Only one message can have {'type': 'image_embeds'}")
+            mm_inputs["image"] = image_embeds_lst[0]
+        elif "image" in items_by_modality:
+            mm_inputs["image"] = items_by_modality["image"] # A list of images
+        elif "audio" in items_by_modality:
+            mm_inputs["audio"] = items_by_modality["audio"] # A list of audios
+        elif "video" in items_by_modality:
+            mm_inputs["video"] = items_by_modality["video"] # A list of videos
+        return mm_inputs
 
     def create_parser(self) -> "BaseMultiModalContentParser":
         return AsyncMultiModalContentParser(self)
@@ -513,6 +560,11 @@ class BaseMultiModalContentParser(ABC):
     def parse_image(self, image_url: str) -> None:
         raise NotImplementedError
 
+    @abstractmethod
+    def parse_image_embeds(self,
+                           image_embeds: Union[str, dict[str, str]]) -> None:
+        raise NotImplementedError
+
     @abstractmethod
     def parse_audio(self, audio_url: str) -> None:
         raise NotImplementedError
@@ -543,6 +595,21 @@ class MultiModalContentParser(BaseMultiModalContentParser):
         placeholder = self._tracker.add("image", image)
         self._add_placeholder(placeholder)
 
+    def parse_image_embeds(self,
+                           image_embeds: Union[str, dict[str, str]]) -> None:
+        if isinstance(image_embeds, dict):
+            embeds = {
+                k: self._connector.fetch_image_embedding(v)
+                for k, v in image_embeds.items()
+            }
+            placeholder = self._tracker.add("image_embeds", embeds)
+
+        if isinstance(image_embeds, str):
+            embedding = self._connector.fetch_image_embedding(image_embeds)
+            placeholder = self._tracker.add("image_embeds", embedding)
+
+        self._add_placeholder(placeholder)
+
     def parse_audio(self, audio_url: str) -> None:
         audio = self._connector.fetch_audio(audio_url)
 
@@ -579,6 +646,25 @@ class AsyncMultiModalContentParser(BaseMultiModalContentParser):
         placeholder = self._tracker.add("image", image_coro)
         self._add_placeholder(placeholder)
 
+    def parse_image_embeds(self,
+                           image_embeds: Union[str, dict[str, str]]) -> None:
+        future: asyncio.Future[Union[str, dict[str, str]]] = asyncio.Future()
+
+        if isinstance(image_embeds, dict):
+            embeds = {
+                k: self._connector.fetch_image_embedding(v)
+                for k, v in image_embeds.items()
+            }
+            future.set_result(embeds)
+
+        if isinstance(image_embeds, str):
+            embedding = self._connector.\
+                fetch_image_embedding(image_embeds)
+            future.set_result(embedding)
+
+        placeholder = self._tracker.add("image_embeds", future)
+        self._add_placeholder(placeholder)
+
     def parse_audio(self, audio_url: str) -> None:
         audio_coro = self._connector.fetch_audio_async(audio_url)
 
@@ -684,6 +770,7 @@ def _get_full_multimodal_text_prompt(placeholder_counts: dict[str, int],
 # No need to validate using Pydantic again
 _TextParser = partial(cast, ChatCompletionContentPartTextParam)
 _ImageParser = partial(cast, ChatCompletionContentPartImageParam)
+_ImageEmbedsParser = partial(cast, ChatCompletionContentPartImageEmbedsParam)
 _AudioParser = partial(cast, ChatCompletionContentPartAudioParam)
 _InputAudioParser = partial(cast, ChatCompletionContentPartInputAudioParam)
 _RefusalParser = partial(cast, ChatCompletionContentPartRefusalParam)
@@ -700,6 +787,8 @@ MM_PARSER_MAP: dict[
     lambda part: _TextParser(part).get("text", ""),
     "image_url":
     lambda part: _ImageParser(part).get("image_url", {}).get("url", ""),
+    "image_embeds":
+    lambda part: _ImageEmbedsParser(part).get("image_embeds", {}),
     "audio_url":
     lambda part: _AudioParser(part).get("audio_url", {}).get("url", ""),
     "input_audio":
@@ -769,6 +858,7 @@ def _parse_chat_message_content_mm_part(
 
 
 VALID_MESSAGE_CONTENT_MM_PART_TYPES = ("text", "refusal", "image_url",
+                                       "image_embeds",
                                        "audio_url", "input_audio", "video_url")
 
 
@@ -843,7 +933,10 @@ def _parse_chat_message_content_part(
         str_content = cast(str, content)
         mm_parser.parse_image(str_content)
         return {'type': 'image'} if wrap_dicts else None
-
+    if part_type == "image_embeds":
+        content = cast(Union[str, dict[str, str]], content)
+        mm_parser.parse_image_embeds(content)
+        return {'type': 'image'} if wrap_dicts else None
     if part_type == "audio_url":
         str_content = cast(str, content)
         mm_parser.parse_audio(str_content)

vllm/multimodal/image.py

@@ -134,3 +134,22 @@ class ImageMediaIO(MediaIO[Image.Image]):
             data = buffer.getvalue()
 
         return base64.b64encode(data).decode('utf-8')
+
+
+class ImageEmbeddingMediaIO(MediaIO[torch.Tensor]):
+
+    def __init__(self) -> None:
+        super().__init__()
+
+    def load_bytes(self, data: bytes) -> torch.Tensor:
+        buffer = BytesIO(data)
+        return torch.load(buffer, weights_only=True)
+
+    def load_base64(self, media_type: str, data: str) -> torch.Tensor:
+        return self.load_bytes(base64.b64decode(data))
+
+    def load_file(self, filepath: Path) -> torch.Tensor:
+        return torch.load(filepath)
+
+    def encode_base64(self, media: torch.Tensor) -> str:
+        return base64.b64encode(media.numpy()).decode('utf-8')

vllm/multimodal/utils.py

@@ -7,6 +7,7 @@ from urllib.parse import ParseResult, urlparse
 
 import numpy as np
 import numpy.typing as npt
+import torch
 from PIL import Image
 
 import vllm.envs as envs
@@ -16,7 +17,7 @@ from vllm.transformers_utils.tokenizer import AnyTokenizer
 
 from .audio import AudioMediaIO
 from .base import MediaIO
-from .image import ImageMediaIO
+from .image import ImageEmbeddingMediaIO, ImageMediaIO
 from .inputs import PlaceholderRange
 from .video import VideoMediaIO
 
@@ -245,6 +246,17 @@ class MediaConnector:
             fetch_timeout=envs.VLLM_VIDEO_FETCH_TIMEOUT,
         )
 
+    def fetch_image_embedding(
+        self,
+        data: str,
+    ) -> torch.Tensor:
+        """
+        Load image embedding from a URL.
+        """
+        image_embedding_io = ImageEmbeddingMediaIO()
+
+        return image_embedding_io.load_base64("", data)
+
 
 global_media_connector = MediaConnector()
 """The global :class:`MediaConnector` instance used by vLLM."""