motu-color-engine

name

motu-color-engine

description

AI portrait color grading, skin-tone correction, identity-preserving skin smoothing, skin/person/face mask export, approved clothing replacement, and ID/passport/headshot/avatar production through the MotuArt Color Engine HTTP API. Use for grading or retouching portraits, normalizing skin tone, exporting mattes, batch-processing portraits, replacing clothing with a server-approved outfit, cropping to ID/passport/visa/headshot specs, replacing an ID-photo background, validating compliance, optimizing upload files, or creating print sheets. Trigger examples include portrait grading, skin tone, retouch, skin mask, outfit replacement, change clothes, ID photo, passport photo, visa photo, headshot, crop to size, background swap, print sheet, 调色, 肤色, 磨皮, 蒙版, 人像调色, 换装, 换衣, 服装替换, 证件照, 裁剪, 换底, 合规检查, 排版, 一寸, 二寸.

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 when auth is enabled; send it only as X-API-Key.
• Never hard-code API keys. If a key is missing and the service requires one, ask the user for it or ask them to export it.
• 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/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/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.

Grade Portraits

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

• 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.
• 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

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.

Export Masks

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

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

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

• 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.
• 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:

scripts/outfits.sh

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

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.

Check ID Photo Compliance

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

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

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.
• Processing is synchronous; batch jobs are repeated one-image calls.
• 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.