MotuArt Color Engine

AI portrait grading, skin-tone correction, identity-preserving smoothing, mask export, approved clothing replacement, professional AI Headshots generation, and ID/passport/headshot/avatar production through the MotuArt Color Engine HTTP API. Use for retouching portraits, normalizing skin tone, expor

Motu Color Engine

Use Motu Color Engine to process portrait images through the hosted HTTP API. Prefer the bundled scripts in scripts/ over hand-written curl calls unless the user explicitly needs raw API details.

The engine preserves identity. Do not describe it as slimming, reshaping, face swapping, or changing facial structure. Skin smoothing only softens pores and blemishes inside detected skin regions. Cropping repositions and pads to a spec; it never stretches or compresses the face.

Setup

• Require curl and python3.
• Read MCE_API_BASE from the environment; default is https://mce.motu.art.
• Read MCE_API_KEY from the environment; send it only as X-API-Key.
• If the key is missing, direct the user to https://mce.motu.art/account (English: /en/account) to sign in by email and create one. Ask them to export it securely in their own environment; do not ask them to paste the full key into chat.
• Never hard-code, print, log, commit, or expose API keys in browser/client code. The full key is shown once and can be rotated or revoked from the account page.
• Request only the scopes needed: catalog:read for portrait/ID discovery, portrait:process for grading/smoothing/masks, id-photo:process for ID-photo workflows, outfit:process for outfit replacement, and headshot:process for private AI Headshots projects and generation. An ID package with an outfit needs both id-photo:process and outfit:process.
• Processing calls consume account credits; catalog discovery does not. Surface 402 insufficient_credits instead of retrying.
• Check service health with curl -sS "${MCE_API_BASE:-https://mce.motu.art}/v1/health" when diagnosing connectivity.

Choose The Workflow

• Use scripts/grade.sh when the user wants color grading, skin-tone correction, a film/commercial look, or grading plus optional crop.
• Use scripts/smooth.sh when the user wants smoothing only with no color or white-balance change.
• Use scripts/portrait-lighting.sh when the user wants visibly more dimensional portrait lighting, a brighter facial plane, readable dark clothing, or a focused background without changing identity or geometry.
• Use scripts/mask.sh when the user wants a skin, valid-skin, face, or person mask/matte.
• Use scripts/crop.sh when the user wants crop-only ID/passport/visa/headshot/avatar output, optionally with a solid background color.
• Use scripts/outfit.sh when the user wants clothing replacement only. The outfit id must come from the approved catalog; never accept or invent a custom prompt or outfit id.
• Use scripts/outfits.sh before clothing replacement to discover currently enabled outfit ids. Do not infer an id from a garment name.
• Use scripts/id-pack.sh when the user wants a complete ID/passport photo delivery package: one graded/smoothed master, multiple specs, upload-ready files, compliance report, and optional print sheets.
• Use scripts/id-check.sh when the user wants to validate an ID photo against a spec or understand compliance warnings.
• Use scripts/optimize.sh when the user needs a website/upload-ready file with format, pixel size, DPI, or maximum KB constraints.
• Use scripts/print-sheet.sh when the user wants cropped ID photos laid out on photo paper for printing.
• Use scripts/headshots.sh when the user wants AI-generated professional, business, corporate, LinkedIn, or studio headshots. Keep reference preparation, confirmation, generation, candidate download, post-processing, and export as explicit stages; do not turn them into one automatic operation.
• Use the Headshots person-reference library when the user wants to reuse a previously confirmed person. Distinguish starting a new project from applying that person to an existing project, and never delete existing projects when removing a library entry.
• Use scripts/styles.sh to discover live style ids. Read references/styles.md only when the user needs style-selection guidance or offline context.
• Use scripts/crop-specs.sh to discover live crop specs. Read references/crop-specs.md only when choosing specs or background palettes without live discovery.
• Read references/api.md for endpoint parameters, response fields, headers, limits, and error codes.
• Read references/headshots-api.md before operating the AI Headshots workflow or when the user needs its raw API details.

Grade Portraits

bash

scripts/grade.sh <input-image> <output-image> [style-id] [strength] [smooth-strength] [smooth-texture-retain] [crop-spec] [bg-color] [pad-color] [lighting-style] [lighting-strength]

• Omit style-id for the default skin base, or choose a style from scripts/styles.sh.
• Use strength for look intensity; default is 1.0, 0 disables the look, and values up to about 1.5 are stronger.
• Pass smooth-strength from 0 to 1 only when the user asks for softened pores or blemishes. Omit it, or pass 0, to preserve natural texture.
• Use smooth-texture-retain from 0 to 1 to keep natural texture over smoothing; default is 0.35.
• Pass crop-spec when the same output should be graded and cropped in one API call.
• Pass bg-color only with crop-spec; use an allowed palette name such as white, blue, or red, default, or explicit #RRGGBB.
• Pass pad-color only with crop-spec when a specific padding color is needed; otherwise let the API edge-replicate.
• Pass lighting-style only when the same output should also receive portrait light sculpting; choose natural_dimension, soft_luminous, or studio_definition. Omit it to preserve the existing grading result.
• Use lighting-strength from 0 to 1 to override that preset's calibrated strength.
• Report skin_dE from script output when summarizing quality; lower means closer skin color to the target.

For a folder, run the script once per image. Keep batch loops serial unless the user asks for parallelism and accepts API/load implications.

Smooth Skin Only

bash

scripts/smooth.sh <input-image> <output.png> [strength] [texture-retain]

• Use this for pore/blemish softening without style, color, or white-balance changes.
• Default strength is 0.6.
• Default texture-retain is 0.35; raise it to preserve more natural texture.

Sculpt Portrait Lighting

bash

scripts/portrait-lighting.sh <input-image> <output.png> [style] [strength]

• Styles are natural_dimension (default), soft_luminous, and studio_definition.
• Omit strength to use the calibrated default for the selected style; otherwise use 0–1.
• soft_luminous prioritizes a luminous face and open dark midtones; natural_dimension balances face, wardrobe and background; studio_definition adds the strongest background focus and local definition.
• The operation reshapes luminance relationships only. It never moves facial features, changes face/body geometry, or regenerates image content.
• Use it independently after another editor, or as an explicit post-process after the user selects a Headshots candidate once that integration is available.

Export Masks

bash

scripts/mask.sh <input-image> <output.png> [mask-kind]

• Use skin by default.
• Other mask kinds are valid_skin, face, and person.
• Output is an 8-bit grayscale PNG aligned to the input.

Crop ID Or Portrait Photos

bash

scripts/crop.sh <input-image> <output-image> [spec-id] [bg-color] [pad-color]

• Default spec-id is one_inch.
• Use scripts/crop-specs.sh to list supported specs and allowed background colors.
• Use bg-color only when the spec declares a background palette, mostly ID-photo specs.
• Use pad-color only when a source image lacks required margins and the user wants a specific fill.
• Surface crop warnings from script output, especially warnings about margins, resolution, or background limitations.
• Use grade.sh with crop arguments when the user wants grading and crop in one output.

Make ID Photo Packages

bash

scripts/id-pack.sh <input-image> <output-dir> [specs] [style-id] [smooth-strength] [bg-color] [upload] [print-sheet] [outfit-id] [outfit-long-edge]

• Use this for passport/visa/ID-photo deliverables rather than calling grade.sh once per spec. The API generates one graded/smoothed master first, then crops multiple specs from that master so colour and retouching stay consistent.
• specs is comma-separated, e.g. passport_cn,one_inch,us_visa; default is passport_cn. School/enrollment specs include shanghai_compulsory_education_cn, college_graduation_image_cn, and national_k12_student_status_cn.
• Default style is motu_business_neutral; pass smooth-strength from 0 to 1 only when the user asks for smoothing.
• bg-color defaults to default, which applies each spec's standard background palette. Use white, blue, light_blue, red, or #RRGGBB when the user asks and the spec allows it.
• upload defaults to true, writing upload-optimized JPG files using the spec's upload rules from crop_specs.json.
• print-sheet is optional, e.g. 6x4 or a4; when specs have different sizes, separate sheets may be generated.
• outfit-id is optional. When present, it must be an id returned by scripts/outfits.sh; omitted keeps the original clothing.
• outfit-long-edge controls the upstream outfit result size, defaults to 1536, and is bounded by the service to 512–2048px.
• Output folder contains master.png, single/, upload/, print/, and report.json. Surface compliance status and warnings from the report.
• When the user requests a supported outfit, pass its approved catalog id. Outfit replacement runs before the corrected master is generated, so all crop specs share the same clothing result.

Replace Clothing Only

Discover the approved catalog first:

bash

scripts/outfits.sh

Select only an id returned by that command, then replace clothing:

bash

scripts/outfit.sh <input-image> <output.png> <approved-outfit-id> [long-edge]

• Only use ids returned by GET /v1/outfits; the API maps each approved id to its controlled generation prompt and rejects custom prompts or arbitrary ids.
• The catalog groups styles as male, female, kids, or unisex; use the category and localized name/description to help select a suitable style.
• If the requested clothing is absent, explain that only catalog styles are available; do not substitute a custom prompt, URL, or upload.
• The service protects the detected facial oval with the face mask and calls the configured Motu asynchronous workflow.
• Default output long edge is 1536px; the service bounds requests to 512–2048px.
• Clothing generation must preserve the face and identity. Report upstream failures or timeouts instead of silently returning the original image.

Create AI Headshots

Use one work directory for the whole staged workflow. The script stores non-secret ids, responses, and configuration in headshots.json; it never stores MCE_API_KEY.

Discover current options:

bash

scripts/headshots.sh catalog [locale]

List reusable confirmed people:

bash

scripts/headshots.sh people [limit]

Prepare a graded, optionally smoothed, purpose-cropped identity reference:

bash

scripts/headshots.sh prepare <input-image> <work-dir> \
  [--scene ID] [--garment male|female] [--skin-base ID] [--smoothing 0..1] \
  [--crop-spec ID] [--crop-anchor auto|center|manual] \
  [--crop-rect X,Y,W,H] [--rotation DEG]

• Inspect source-check.json and reference-preview.png before continuing.
• Surface ineligible reasons and warnings. Do not submit generation for an ineligible source.
• skin-base performs colour/skin-tone preparation; smoothing=0 preserves natural texture.
• Use an automatic crop unless the user provides a complete normalized manual rectangle.
• Never confirm the reference without the user approving the preview.

After approval, freeze that preview as the identity reference:

bash

scripts/headshots.sh confirm <work-dir>

Confirmation automatically adds the approved person to the account library, deduplicated by the confirmed reference image. To start a separate project from a saved person, or switch the active person inside an existing project while preserving its history:

bash

scripts/headshots.sh start-person <person-reference-id> <new-work-dir> [--scene ID]
scripts/headshots.sh use-person <existing-work-dir> <person-reference-id>

use-person appends a new immutable reference to the same project. Existing jobs, candidates, favorites, and prior references remain available. Removing a person is a library-only soft delete:

bash

scripts/headshots.sh remove-person <person-reference-id>

Submit a compatible generation plan without waiting for the asynchronous worker:

bash

scripts/headshots.sh generate <work-dir> [--scene ID] [--batch-size 1|2|4] \
  [--style ID] [--pose ID] [--outfit ID] [--background ID] \
  [--ratio 1:1|4:5|3:4] [--framing auto|close_up|half_body|three_quarter]

• Let the recommendation endpoint fill omitted options and correct incompatible defaults.
• Use only ids returned by the live Headshots catalog. Never send custom generation prompts.
• Generation consumes credits per requested image. Surface 402 and do not retry unchanged.
• The command submits one job and returns; it does not hide asynchronous work behind a long synchronous call.

Check and download results explicitly:

bash

scripts/headshots.sh status <work-dir>
scripts/headshots.sh download <work-dir>

Download after the job is completed or partially_completed. For a partial result, surface the failure reason and download every ready candidate rather than discarding successful outputs.

Post-process a user-selected candidate and optionally export that render:

bash

scripts/headshots.sh render <work-dir> --candidate ID-or-ordinal --style ID [--locale LOCALE]
scripts/headshots.sh light <work-dir> --candidate ID-or-ordinal [--style ID] [--strength 0..1] [--render]
scripts/headshots.sh export <work-dir> --candidate ID-or-ordinal [--render] \
  [--crop SPEC] [--format jpeg|png|webp] [--quality 70..100]

• Require an explicit candidate id or ordinal.
• light without --render creates an immutable lighting Render from the Candidate master. With --render, it uses the latest saved Render as its source, allowing an explicit grade → light chain without overwriting either version.
• Without --render, export the generated master candidate. With --render, use the latest explicit render saved in the work directory.
• Keep project_id, reference_id, job_id, and derivative ids so an interrupted workflow can resume.

Check ID Photo Compliance

bash

scripts/id-check.sh <input-image> [spec-id] [report-json]

• Without report-json, the input is treated as a source portrait: the API crop-checks it against the spec and reports practical compliance.
• With report-json, the input is treated as the already-cropped ID photo and the supplied crop metrics are checked.
• Report failures and warnings plainly; this is a practical QA check, not a government guarantee.

Optimize Upload Files

bash

scripts/optimize.sh <input-image> <output-image> [format] [max-kb] [quality] [resize] [dpi]

• Use for official website upload limits such as JPG under a maximum KB, exact pixel dimensions, or DPI metadata.
• format is jpg, png, or webp; resize is WIDTHxHEIGHT; lossy formats search quality down to the server default floor when max-kb is set.

Make Print Sheets

bash

scripts/print-sheet.sh <output-image> <paper> <input1> [input2 ...]

• Use after generating cropped ID photos when the user wants a printable sheet.
• paper supports common values such as 6x4, 4x6, 5x7, and a4. Inputs on a single sheet must have the same pixel size; use id-pack.sh for automatic grouping by size.

Constraints To Surface

• Upload limit is about 15 MB per image.
• Supported upload formats are JPG, PNG, and WebP.
• Portrait, crop, and ID-photo processing calls are synchronous. Headshots generation is asynchronous and must be polled by job id.
• Background replacement is limited to specs that declare bg_colors.
• If a script fails, read its HTTP status and error detail before deciding whether to retry, change arguments, or ask the user for configuration.