sgl-project/sglang · error · ValueError

No base64 image data found

Error message

No base64 image data found

What it means

ValueError from decode_image_from_response: the selected image entry exists but its 'b64_json' field is missing or empty, so the client cannot decode pixel data. Some servers return a URL instead of inline base64.

Source

Thrown at python/sglang/multimodal_gen/apps/ComfyUI_SGLDiffusion/core/server_api.py:440

        """
        Decode base64 image from API response.

        Args:
            response_data: API response dictionary
            index: Index of the image in the response (default: 0)

        Returns:
            PIL Image object
        """
        if "data" not in response_data or not response_data["data"]:
            raise ValueError("No image data in response")

        if index >= len(response_data["data"]):
            raise IndexError(f"Image index {index} out of range")

        image_data = response_data["data"][index]
        if "b64_json" not in image_data or not image_data["b64_json"]:
            raise ValueError("No base64 image data found")

        image_bytes = base64.b64decode(image_data["b64_json"])
        image = Image.open(io.BytesIO(image_bytes))

        # Convert to RGB if needed
        if image.mode != "RGB":
            image = image.convert("RGB")

        return image

    def set_lora(
        self,
        lora_nickname: str,
        lora_path: Optional[str] = None,
        target: str = "all",
    ) -> Dict[str, Any]:
        """
        Set a LoRA adapter for the specified transformer(s).

View on GitHub (pinned to 0132848349)

Solutions

1. Log the image entry keys to see the actual schema (url vs b64_json).
2. If URLs are returned, download the image from the URL instead of decoding base64.
3. Ensure the request asked for response_format b64 (if supported).
4. Upgrade client and server to matching versions.

Example fix

// before
image_data = response["data"][0]  # then decode_image_from_response fails
// after
entry = response["data"][0]
if not entry.get("b64_json") and entry.get("url"):
    import requests as rq, io
    from PIL import Image
    image = Image.open(io.BytesIO(rq.get(entry["url"]).content))

entry = response['data'][index]
assert entry.get('b64_json'), f'keys={list(entry)}'

def has_b64(entry: dict) -> bool:
    return bool(entry.get('b64_json'))

if not entry.get('b64_json'):
    if entry.get('url'):
        img = fetch(entry['url'])
    else:
        raise ValueError(f'no image payload: {entry}')

When it happens

Trigger: Server returns images as 'url' references instead of 'b64_json', or returns an entry with an empty b64 string (failed per-image generation).

Common situations: Server configured for URL-response mode; partial failure where one of n images failed; API version mismatch changing the response schema.

Related errors

• No image data in response
• Image index {index} out of range
• lora_nickname cannot be empty
• material URI has data after base64 padding
• Failed to decode base64 image. Expected format: `data:[<medi

AI-assisted analysis of sgl-project/sglang@0132848349 (2026-08-28). Data as JSON: /api/errors/4f5804592065b50e. Report an issue: GitHub.