API reference/POST /outline

Thin colored outline

Subject silhouette traced with a thin colored stroke on transparent background. Useful for highlight overlays, shop badges, and design treatments.

POSThttps://useknockout--api.modal.run/outline

Parameters

Send as multipart/form-data unless noted otherwise.

filerequiredfile—Image to process. JPG, PNG, WebP, HEIC. Up to 10 MB and 4096×4096.
colorstring#57C985Hex stroke color.
widthint 1-203Stroke thickness in pixels.
fillbooleanfalseIf true, fill the silhouette interior with the color.

Request

curl -X POST "https://useknockout--api.modal.run/outline" \
  -H "Authorization: Bearer $TOKEN" \
  -F "file=@cat.jpg" \
  -F "color=#57C985" -F "width=4" \
  -o out.png

Response

HTTP/1.1 200 OK
content-type: image/png
content-length: 254312
x-knockout-latency: 184
x-knockout-model: BiRefNet
x-ratelimit-limit: 60
x-ratelimit-remaining: 59

Errors

401unauthorized—Missing or invalid token.
402payment_required—Free tier exhausted. Add a card to continue.
413payload_too_large—Image exceeds 10 MB or 4096×4096.
422no_subject_detected—Foreground could not be isolated from background.
429rate_limit_exceeded—Slow down. Retry-After header tells you when.
500internal_error—Something broke on our side. Include request_id when reporting.
Every error response also includes a request_id in the JSON body. Quote it when reporting issues.
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