Annotate detections

POST /api/image-annotate-detections2 quota units per call · cache hits free

Render bounding boxes and labels onto an image. Accepts the JSON output of any of the detection tools (faces / barcodes / QR / contours / etc.) and produces a visual overlay.

Draws coloured bounding boxes and text labels onto an image, given a list of detection rectangles. The companion tool for the various detection tools (`image-detect-qr`, `image-face-detect`, `image-detect-barcode`, etc.). Use the JSON output of any detection tool as the `detections` array — each entry needs `{rect: {x,y,width,height}, label?, color?}`.

Inputs

Name	Type	Default	Description
image*	file	—	Input image bytes.
detections*	string	—	JSON-encoded array of `{x, y, width, height, label?, score?, color?}` (or any object with `box: [x,y,w,h]`).
lineWidth	number (1…32)	3	Rectangle stroke width.
defaultColor	string	"#ff3366"	Stroke colour fallback (CSS hex).
fontScale	number (0…4)	0.6	Label font scale (0 = no labels).
format	enum (jpeg \| png)	"jpeg"	Output encoding.
quality	number (1…100)	90	JPEG quality.

Response

Modes: binary, stream, json. Cache: yes (24h TTL).

Large outputs stream: responses over the 4 MiB cache limit are piped through as they are produced instead of buffered. They carry x-cache-skip: size and are never cached — identical follow-up calls recompute.

Every response carries x-cache (HIT / MISS / BYPASS), x-cache-signature (stable across identical inputs), and the rate-limit headers listed below.

Quota & limits

Cost per call	2 units against the 10,000-unit monthly quota. Cache hits are free — only cache misses decrement.
Burst limit	200 requests per rolling minute, shared across all tools.
Max request size	`25 MiB` (base64 inflates file payloads ~33% — the limit applies to the decoded bytes).
Max response size	`25 MiB`
Timeout	15s wall clock.
Rate-limit headers	`X-RateLimit-Limit`, `X-RateLimit-Remaining`, `X-RateLimit-Burst-Limit` on every response; `X-Quota-Warning` once 80% of the monthly quota is spent; `Retry-After` on 429s.

Errors

Errors are JSON with an error string; schema failures add a details object (Zod's flattened field errors).

Status	When	Body
400	Input fails the tool's schema (wrong type, missing required field, malformed base64) or the file bytes can't be parsed as the expected format.	{ "error": "invalid inputs", "details": { "fieldErrors": { … } } }
401	Missing or invalid X-Api-Key / X-Account-Id headers (or no session when called from the browser).	{ "error": "unauthorized" }
404	Unknown tool id, or calling /api/* on the website hostname instead of api.xtract.bot.	{ "error": "not found" }
413	Request body over the tool's max request size, or an image header declaring more megapixels than the tool's pixel budget.	{ "error": "…exceeds maxRequestBytes…" }
415	Content-Type isn't application/json on the json-body transport.	{ "error": "unsupported content-type; expected application/json" }
429	Monthly quota or the 200/min burst limit exhausted. Check Retry-After and the X-RateLimit-* headers.	{ "error": "monthly quota exceeded", "monthRemaining": 0, … }
5xx	Conversion engine failure. Safe to retry; if it persists, the input is hitting a bug — please report it.	{ "error": "…" }

Code samples

Built from the one-box example.

# Download or substitute the example input:
#   curl -O https://xtract.bot/examples/image-align/sample.png
IMAGE=$(base64 -w0 < sample.png)

curl -X POST https://api.xtract.bot/api/image-annotate-detections \
  -H "Content-Type: application/json" \
  -H "Accept: application/octet-stream" \
  -H "X-Account-Id: $XTRACT_ACCOUNT_ID" \
  -H "X-Api-Key: $XTRACT_API_KEY" \
  -d '{
  "detections": "[{\"x\":30,\"y\":80,\"width\":80,\"height\":80,\"label\":\"box\"}]",
  "lineWidth": 2,
  "image": "'"$IMAGE"'"
}'