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scan_image_service

Serves an already-resolved scan file as a ZIP of scaled WebP frames.

Resolution (scan_id/path → validated file path) is the repository's job; this service takes a resolved path, reads or builds each cache layer the request needs — the frames always, plus the masks and the vectors when those outputs were asked for — and stitches them into one archive. The repository composes it and dispatches to render.

Classes​

ScanImageService​

class ScanImageService(    *,    cache: ScanImageCache,    default_width: int,    quality: int,    cache_getter: Callable[[], CacheProtocol] | None = None,):

Renders a resolved scan file into a ZIP of scaled WebP frames, cached.

Arguments

  • cache: The encrypted on-disk image cache.
  • default_width: Output width used when the request omits one.
  • quality: WebP quality for encoding.
  • cache_getter: A zero-arg callable returning the pod background cache, used to look up segmentation overlays. None (the default) leaves the overlay feature disabled, so requests are served images-only.

Store the cache and conversion parameters used to render scans.

Methods​

render​

def render(    self,    resolved_path: str,    *,    file_id: str,    modality: str | None,    laterality: str | None,    width: int | None,    refresh: bool,    include_masks: bool = False,    include_vectors: bool = False,    segmentation_classes: list[str] | None = None,) ‑> bytes:

Return the ZIP archive of converted frames for a resolved scan file.

With both overlay flags False (the default), no inference fingerprint is read and no overlay work is attempted, so an opt-out request touches neither the background cache nor model-inference storage.

Arguments

  • resolved_path: The already-resolved, allowlisted scan file path.
  • file_id: The scan's raw ingested path, as recorded on its inference rows. Deliberately not the resolved real path: the rows key on the path ingest stored, which differs under a symlinked mount.
  • modality: Optional series selector.
  • laterality: Optional "L"/"R" series selector.
  • width: Requested output width; None uses the configured default.
  • refresh: When True, bypass and overwrite any cached entry.
  • include_masks: Whether the archive should carry a rendered mask PNG per segmentation class.
  • include_vectors: Whether the served index should carry each class's raw drawable instances, in the model's own pixel space. Costs no PNG encode, so it is the cheap way to overlay a scan.
  • segmentation_classes: Optional class-name filter, applied after normalising each name (case/punctuation-insensitive) the same way a model's own class names are normalised. Ignored when neither overlay output was requested. A name that matches no class any model produced yields no output for it, never an error.

Returns The ZIP archive bytes.

Raises

  • ScanRequestError: Non-positive width, or an undecodable file.
  • ScanNotFoundError: The resolved file is missing/unreadable (e.g. deleted or unmounted between resolution and rendering).

ScanNotFoundError​

class ScanNotFoundError(*args, **kwargs):

Raised when a scan_id/path cannot be resolved to an authorised file.

ScanRequestError​

class ScanRequestError(*args, **kwargs):

Raised for malformed requests (bad inputs, undecodable file).