Invoice PNG Preview

Render a realistic image/png preview of an invoice.

Use this when an AI agent, chat UI, or browser client cannot display PDF directly. Use /v1/generate for the final compliant PDF/XML artifact.

Quick start (two steps)

Step 1 — Generate the invoice and save the transaction_id:

TRANSACTION_ID=$(curl -s -X POST https://api.thelawin.dev/v1/generate \
  -H "Content-Type: application/json" \
  -H "X-API-Key: env_sandbox_demo_public" \
  -d '{
    "format": "zugferd",
    "template": "minimal",
    "invoice": {
      "number": "RE-2026-001",
      "date": "2026-01-15",
      "seller": {
        "name": "Acme GmbH",
        "street": "Musterstr. 1",
        "city": "Berlin",
        "postal_code": "10115",
        "country": "DE",
        "vat_id": "DE123456789"
      },
      "buyer": {
        "name": "Customer AG",
        "street": "Kundenweg 5",
        "city": "Munich",
        "postal_code": "80331",
        "country": "DE"
      },
      "items": [{
        "description": "Consulting",
        "quantity": 8,
        "unit": "HUR",
        "unit_price": 150.00,
        "vat_rate": 19
      }]
    }
  }' | jq -r '.transaction_id')

echo "Transaction ID: $TRANSACTION_ID"

Step 2 — Fetch the PNG preview (no API key needed):

curl -s "https://api.thelawin.dev/v1/preview/${TRANSACTION_ID}.png" -o preview.png

The preview is available for 5 minutes after generation.

GET /v1/preview/{transaction_id}.png

Retrieve a cached invoice preview by transaction ID. No authentication required.

GET https://api.thelawin.dev/v1/preview/{transaction_id}.png

Parameter	In	Default	Description
transaction_id	path	required	The transaction_id from /v1/generate response
page	query	1	Page number to render
dpi	query	150	Resolution (72-300)

Example:

GET https://api.thelawin.dev/v1/preview/a1b2c3d4e5f67890.png?page=1&dpi=200

POST /v1/preview

Alternative: render a preview from a transaction ID or invoice JSON body. Requires API key when sending invoice JSON (costs 1 credit).

POST https://api.thelawin.dev/v1/preview

From transaction ID

curl -s -X POST https://api.thelawin.dev/v1/preview \
  -H "Content-Type: application/json" \
  -d '{
    "transaction_id": "a1b2c3d4e5f67890a1b2c3d4e5f67890",
    "page": 1,
    "dpi": 144
  }' -o preview.png

From invoice JSON (costs 1 credit)

curl -s -X POST https://api.thelawin.dev/v1/preview \
  -H "Content-Type: application/json" \
  -H "X-API-Key: env_sandbox_demo_public" \
  -d '{
    "template": "minimal",
    "page": 1,
    "dpi": 144,
    "invoice": {
      "number": "RE-2026-001",
      "date": "2026-01-15",
      "seller": {
        "name": "Acme GmbH",
        "street": "Musterstr. 1",
        "city": "Berlin",
        "postal_code": "10115",
        "country": "DE",
        "vat_id": "DE123456789"
      },
      "buyer": {
        "name": "Customer AG",
        "street": "Kundenweg 5",
        "city": "Munich",
        "postal_code": "80331",
        "country": "DE"
      },
      "items": [{
        "description": "Consulting",
        "quantity": 8,
        "unit": "HUR",
        "unit_price": 150.00,
        "vat_rate": 19
      }]
    }
  }' -o preview.png

Response

The response body is the PNG image directly.

Content-Type: image/png
X-Transaction-Id: a1b2c3d4e5f67890a1b2c3d4e5f67890
X-Preview-Source: cache
X-Preview-Width: 1191
X-Preview-Height: 1684

PNG previews are cached for 5 minutes after generation.