Barcode Hub

Barcode Hub is a Python service for barcode recognition over HTTP and MCP. The recognition backend is zxing-cpp.

The API response body is intentionally minimal:

{
  "barcodes": [
    {
      "text": "4607084351323",
      "data": "NDYwNzA4NDM1MTMyMw==",
      "type": "EAN13",
      "valid": "yes"
    }
  ]
}

Build identity is emitted at runtime as an HTTP Server header on every response, but it is not part of the OpenAPI or MCP contracts.

Endpoints

Single service port, default 8080:

• GET / shows a small HTML server index with build info and resource links

• GET /decode?url=...&types=EAN13,UPCA

• POST /decode with exactly one multipart/form-data image file

• PUT /decode with raw image bytes and an image/* Content-Type

• GET /health checks that zxingcpp is importable and exposes the required API

• GET /metrics exposes Prometheus metrics

• /mcp when MCP is enabled

• /docs, /redoc, /openapi.json

Related MCP server: Scan QRCode MCP Server

Run Locally

python3.12 -m venv .venv
. .venv/bin/activate
pip install -e '.[dev]'
barcode-hub

Decode from a URL:

curl 'http://localhost:8080/decode?url=https://example.com/image.jpg&types=EAN13,UPCA'

Decode an uploaded file:

curl -F 'file=@image.jpg;type=image/jpeg' 'http://localhost:8080/decode?types=EAN13'

Decode raw bytes:

curl -X PUT --data-binary @image.jpg -H 'Content-Type: image/jpeg' \
  'http://localhost:8080/decode?types=EAN13'

Docker

Use the prebuilt image from GitHub Container Registry:

docker pull ghcr.io/yiivgeny/barcode-hub:latest
docker run --rm -p 8080:8080 ghcr.io/yiivgeny/barcode-hub:latest

Or build locally:

docker build -t barcode-hub:local .
docker run --rm -p 8080:8080 barcode-hub:local

Docker Compose builds the local image by default:

docker compose up --build

Configuration

Configuration is loaded from /etc/barcode-hub/config.yaml when it exists. Environment variables override file values. Nested variables use __ and the BARCODE_HUB_ prefix.

Example YAML:

app:
  port: 8080
limits:
  max_request_body_bytes: 16777216
  max_file_bytes: 8388608
  max_image_side_pixels: 4096
decode:
  enabled_methods: ["GET", "POST", "PUT"]
  default_formats: ["EAN13", "EAN8", "UPCA", "UPCE"]
  allowed_formats: ["EAN13", "EAN8", "UPCA", "UPCE", "QRCode", "DataMatrix"]
  request_timeout_seconds: 10
fetch:
  timeout_seconds: 5
  allowed_url_prefixes: ["https://*.example.com/", "data:*"]
media:
  allowed_content_types: ["image/png", "image/jpeg", "image/webp"]
mcp:
  enabled: true
logging:
  format: human
  level: INFO

Common environment variables:

• BARCODE_HUB_LIMITS__MAX_REQUEST_BODY_BYTES

• BARCODE_HUB_LIMITS__MAX_FILE_BYTES

• BARCODE_HUB_LIMITS__MAX_IMAGE_SIDE_PIXELS

• BARCODE_HUB_DECODE__ENABLED_METHODS

• BARCODE_HUB_DECODE__REQUEST_TIMEOUT_SECONDS

• BARCODE_HUB_FETCH__TIMEOUT_SECONDS

• BARCODE_HUB_FETCH__ALLOWED_URL_PREFIXES

• BARCODE_HUB_MEDIA__ALLOWED_CONTENT_TYPES

• BARCODE_HUB_MCP__ENABLED

• BARCODE_HUB_LOGGING__FORMAT

allowed_url_prefixes are matched by parsing URLs. For example, https://*.example.com/ matches https://cdn.example.com/image.jpg, but does not match https://test.tld/example.com/image.jpg.

Metrics

/metrics includes process/platform/gc metrics and service metrics:

• barcode_hub_decode_requests_total{interaction,status}

• barcode_hub_decoded_barcodes_total{interaction,type,valid}

• barcode_hub_decode_request_duration_seconds{interaction,status}

• barcode_hub_recognition_duration_seconds{interaction,status}

• barcode_hub_resource_fetch_duration_seconds{interaction,status}

• barcode_hub_decode_input_bytes{interaction,source}

• barcode_hub_decode_image_max_side_pixels{interaction}

• barcode_hub_build_info

Interaction labels are get_url, post_multipart, put_binary, and mcp_url.

MCP

When enabled, /mcp exposes the decode_url tool:

decode_url(url: string, types?: list[BarcodeType]) -> DecodeResult

data:image/...;base64,... URLs are supported. MCP tool errors use MCP error semantics and stable domain codes in the message, such as invalid_url, disallowed_type, resource_timeout, and request_too_large.

Development

pip install -e '.[dev]'
python scripts/generate_contract.py --check
pytest
ruff check .

The shared response schema is spec/decode-result.schema.json. The OpenAPI contract is spec/openapi.yaml. The MCP contract is spec/mcp.md.

Runtime /openapi.json is loaded from spec/openapi.yaml and then narrowed by the active configuration: disabled /decode methods are removed, BarcodeType is limited to decode.allowed_formats, and request media types reflect media.allowed_content_types. Swagger UI and ReDoc use that runtime schema.

DecodeResult, Barcode, BarcodeType, and BarcodeValidity are generated from the Python models and format enum:

python scripts/generate_contract.py

The generator updates spec/decode-result.schema.json and only the marked components.schemas block in spec/openapi.yaml. Paths, request/response semantics, examples, and MCP documentation remain hand-authored.

License

Barcode Hub is MIT licensed. zxing-cpp is Apache-2.0 licensed; keep upstream notices when redistributing images or derived distributions.