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SnapOtter/apps/docs/tools/image/smart-crop.md
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description
description
Subject-, face-, and entropy-aware cropping that frames images intelligently using Sharp and AI face detection.

Smart Crop

Smart subject-aware, face-aware, or trim-based cropping. Uses Sharp's attention/entropy strategies and AI face detection for intelligent framing.

API Endpoint

POST /api/v1/tools/image/smart-crop

Processing: Asynchronous (returns 202, poll /api/v1/jobs/{jobId}/progress for status via SSE)

Model bundle: face-detection (200-300 MB) - required only for face mode

Parameters

Parameter Type Required Default Description
file file Yes - Image file (multipart)
mode string No "subject" Crop mode: subject, face, trim. (Legacy values attention and content map to subject and trim)
strategy string No "attention" Strategy for subject mode: attention or entropy
width integer No - Target width in pixels
height integer No - Target height in pixels
padding integer No 0 Padding percentage around subject (0-50)
facePreset string No "head-shoulders" Face framing preset: closeup, head-shoulders, upper-body, half-body
sensitivity number No 0.5 Face detection sensitivity (0-1)
threshold integer No 30 Trim mode threshold for background detection (0-255)
padToSquare boolean No false Pad trimmed result to a square
padColor string No "#ffffff" Background color for padding
targetSize integer No - Target size for padded output (pixels)
quality integer No - Output quality (1-100)

Example Request

curl -X POST http://localhost:1349/api/v1/tools/image/smart-crop \
  -F "file=@portrait.jpg" \
  -F 'settings={"mode":"face","width":1080,"height":1080,"facePreset":"head-shoulders"}'

Response

Initial Response (202 Accepted)

{
  "jobId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "async": true
}

Progress (SSE at /api/v1/jobs/{jobId}/progress)

event: progress
data: {"phase":"processing","percent":50}

Final Result (via SSE)

{
  "phase": "complete",
  "percent": 100,
  "result": {
    "jobId": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
    "downloadUrl": "/api/v1/download/{jobId}/portrait_smartcrop.jpg",
    "originalSize": 500000,
    "processedSize": 320000
  }
}

Modes

Subject Mode

Uses Sharp's attention or entropy strategy to find the most visually interesting region and crops around it.

Face Mode

Detects faces using AI, then frames the crop around detected faces using the specified facePreset. Falls back to subject mode (attention strategy) if no faces are detected.

Trim Mode

Removes uniform borders/background from the image. Optionally pads the result to a square with a specified background color and target size.

Notes

  • This tool uses the createToolRoute factory with executionHint: "long", so it returns 202 with SSE progress.
  • Face mode requires the face-detection model bundle (200-300 MB).
  • Subject and trim modes work without any AI model bundle.
  • The facePreset determines how tightly the crop frames detected faces: closeup is the tightest, half-body is the widest.
  • If no width/height are specified, defaults to 1080x1080.