> ## Documentation Index > Fetch the complete documentation index at: https://docs.cyberwave.com/llms.txt > Use this file to discover all available pages before exploring further. # Barcode Reader node > Decode 1D and 2D codes (QR, Data Matrix, Aztec, EAN/UPC, Code 128, PDF417, ITF, …) using zxing-cpp. Runs on edge (per camera frame, Pi-class hardware) and in the cloud workflow runner (on a Data Source / Call Model image). `barcode_reader` is a stateless perception node that decodes barcodes and 2D codes from a frame and emits a structured list of codes plus a `call_model`-shaped `detections` projection — so the existing perception chain (`annotate`, `spatial_filter`, `conditional/detection_event_gate`, `send_alert`) consumes barcodes with no special-casing. The same node compiles into the edge worker (`@cw.on_frame` handler on the device) when the workflow has `Run on edge` enabled and a Camera Frame trigger upstream, **and** runs in the cloud workflow runner otherwise (against an `image_url` or `image_bytes` from `data_source` / `call_model`). The decode helpers live in `src/lib/workflow_utils.py` and are inlined into the generated worker via `inspect.getsource()` so the cloud and edge paths share one decoder implementation. It is backed by [zxing-cpp](https://github.com/zxing-cpp/zxing-cpp) (Apache-2.0), a fast native-C++ decoder with prebuilt Python wheels for `manylinux_x86_64`, `manylinux_aarch64` (Pi 4 / 5 64-bit), macOS, and Windows. No GPU and no system package install — `pip install zxing-cpp` inside the edge worker image is enough. Typical chain for a "scan and alert" warehouse workflow: ``` trigger (camera_frame) → barcode_reader → conditional → send_alert ↘ annotate (overlay boxes for the live preview) ``` ## Symbologies Default is "any symbology zxing-cpp supports". You can narrow it down to the formats you actually expect — this reduces false positives and shortens decode time per frame. | Group | Formats | | ---------------------- | ----------------------------------------------------------------------------- | | Retail | EAN-13, EAN-8, UPC-A, UPC-E | | Logistics / industrial | Code 128, Code 39, Code 93, ITF, Codabar, GS1 DataBar, GS1 DataBar Expanded | | 2D | QR Code, Micro QR, Rectangular Micro QR, Data Matrix, Aztec, PDF417, MaxiCode | ## Inputs | Field | Type | Description | | --------------- | ------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `frame` | image / bytes | Canonical input. On edge, implicitly wired from an upstream `camera_frame` trigger (decoded ndarray). On cloud, typically auto-wired from `Data Source.image_bytes` — Data Source eager-fetches the URL for every `data_type` so the bytes are always populated. | | `image_bytes` | bytes | Legacy alias for callers without input mappings. Cloud-only. Remote URL inputs are no longer accepted — wire a Data Source upstream so it can do the fetch. | | `symbologies` | array | Restrict decoding to these formats. Empty = any format. | | `max_codes` | number | Cap the number of codes returned per frame (default `8`). | | `try_rotate` | boolean | Search for codes rotated 90°/180°/270° as well as upright (default `true`). | | `try_invert` | boolean | Also attempt light-on-dark / inverted codes (default `true`). | | `try_downscale` | boolean | Also attempt scaled-down versions of the frame (default `true`). | | `binarizer` | string | Threshold strategy: `local_average` (default), `global_histogram`, `fixed_threshold`, `bool_cast`. | ## Outputs | Field | Type | Description | | ------------------ | ------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `codes` | array | One entry per decoded code with `symbology`, `text`, `bytes_b64` (raw payload, for binary Data Matrix), `polygon` (4 pixel corners), `bbox` (`{x1, y1, x2, y2}` in pixels), `orientation`, `ec_level`, `content_type`. | | `count` | number | `len(codes)` after the `max_codes` cap. | | `detections` | array | `call_model`-shaped projection — `class` = symbology, `confidence` = `1.0`, pixel `bbox`. Drop-in for `annotate` / `spatial_filter` / `conditional/detection_event_gate`. | | `source_image_url` | string | Cloud-only. Echo of the resolved upstream `image_url` so `annotate` / `send_alert` can reference the exact frame that was decoded. | | `frame` | image | Edge-only. Pass-through of the input camera frame for a downstream `annotate` overlay. | ## Edge implementation The node compiles into the same `@cw.on_frame` worker that the rest of the perception chain uses. Runtime helpers (`_decode_barcodes`, `_barcode_codes_to_detections`, plus the small `_barcode_position_to_polygon` / `_barcode_polygon_bbox` geometry helpers) are inlined at module scope from `src/lib/workflow_utils.py` via `inspect.getsource()` and shared across multiple `barcode_reader` nodes in the same worker. The `zxing-cpp` wheel is lazy-imported on first decode so missing the optional `barcode` SDK extra surfaces in node logs rather than blocking worker startup. The `edge-ml-worker` Docker image ships with `zxing-cpp` baked in (the `barcode` extra is part of the default `CYBERWAVE_SDK_EXTRAS`). For a custom Pi-slim image, include `barcode` alongside `zenoh` and `schedule` and skip the heavier `ml-*` extras. See [Edge Workers](/feature-reference/workflows/workers/overview) for the full lifecycle. ## Companion nodes * `annotate` — draw decoded barcode boxes on the live overlay channel. * [`spatial_filter`](./spatial-filter) — only count codes that fall inside an author-defined ROI (e.g. the conveyor belt zone). * [`conditional`](./timed-condition) — fire on first-seen, on a new payload, or only after a code has been visible for N frames. * `send_alert` — escalate to an operator with the decoded payload attached.