Image Processor Guidelines - Quantum Skincare

Purpose

Quick reference for Quantum Skincare's Python FastAPI image processor microservice, emphasizing FastAPI patterns, Perfect Corp API integration, MediaPipe FaceMesh validation, and structured error handling.

When to Use This Skill

• Creating or modifying image processor routes
• Working with Perfect Corp API integration
• Implementing face validation logic
• Adding validation pipeline checks
• Configuring access control and security
• Handling correlation headers (X-Request-Id, X-Analysis-Session, X-Frame-Seq)
• Writing Pydantic models
• Implementing error handling
• Adding structured logging
• Working with mock mode
• Testing image processor endpoints
• Python/FastAPI best practices

---

Quick Start

New Route Checklist

• Route under /v1 prefix (NEVER unversioned)
• Use Depends(ensure_valid_upload) for file uploads
• Add correlation headers support (X-Request-Id, X-Analysis-Session, X-Frame-Seq)
• Implement proper error handling with AppError or _http_exc()
• Use Pydantic models with response_model_exclude_none=True
• Add structured logging with request_id context
• Test with both mock and real modes
• Verify access control (CIDR + X-Internal-Secret)
• Document in docstring

New Validation Check Checklist

• Add to validation pipeline (validation/pipeline.py)
• Return structured result with success, reason, details
• Add to diagnosis response
• Test with various failure cases
• Document thresholds and behavior

---

Service Architecture

Tech Stack

• Framework: FastAPI (ASGI via uvicorn)
• Models: Pydantic v2 with BaseModel
• Logging: Structured JSON logging with contextual requestId, route, latency
• Face Detection: MediaPipe FaceMesh with concurrency gate
• Provider: Perfect Corp API with mock/real modes
• Image Processing: PIL (Pillow) for JPEG normalization and resize
• Access Control: CIDR allowlist + X-Internal-Secret header
• Deployment: Dockerized with /livez and /readyz probes

Directory Structure

apps/image-processor/src/
├── app_http/
│   ├── routes/              # API route handlers
│   │   ├── analyze.py       # POST /v1/perfect-corp/analyze
│   │   ├── validate.py      # POST /v1/validate/face
│   │   └── health.py        # GET /livez, /readyz
│   ├── middleware_access.py # CIDR + secret validation
│   ├── middleware_request_id.py # X-Request-Id propagation
│   ├── headers.py           # Header extraction utilities
│   └── upload_utils.py      # File upload validation
├── config/
│   └── settings.py          # Pydantic settings (env vars)
├── providers/
│   ├── perfect_corp/        # Perfect Corp API client
│   │   ├── client.py        # Main API client
│   │   ├── auth.py          # RSA token authentication
│   │   ├── files.py         # File upload
│   │   ├── tasks.py         # Task polling
│   │   ├── normalizer.py    # Result normalization
│   │   └── http_client.py   # HTTP client with retries
│   └── storage/             # S3 uploader (optional)
├── validation/
│   ├── pipeline.py          # Main validation pipeline
│   ├── mesh_runtime.py      # FaceMesh singleton
│   ├── geometry.py          # Pose, ratio, centering
│   ├── lighting.py          # Lighting analysis
│   └── serialization.py     # Mesh data serialization
├── main.py                  # FastAPI app factory
├── entrypoint.py            # Uvicorn entrypoint
├── errors.py                # Error models and handlers
├── schemas.py               # Pydantic response models
├── perfect_corp_types.py    # Provider type definitions
└── logging_setup.py         # Logging configuration

---

Key Endpoints

POST /v1/perfect-corp/analyze

Full skin analysis via Perfect Corp API:

@router_v1.post(
    "/perfect-corp/analyze",
    response_model=PerfectCorpAnalysisResponse,
    response_model_exclude_none=True,
)
async def analyze_skin(
    request: Request,
    file: UploadFile = Depends(ensure_valid_upload),
):
    """
    Upload image for full skin analysis.
    Returns: { success, data: { analysisId, skinType, skinAge, programCode, ... }, meta }
    """
    # 1. Extract correlation headers
    request_id = request.state.request_id
    session_id = extract_analysis_session_id(request)

    # 2. Process image (resize to 1024px width JPEG)
    image_bytes = process_image_for_provider(file)

    # 3. Call Perfect Corp API or return mock data
    result = await client.analyze(image_bytes)

    # 4. Attach correlation under `meta`
    return PerfectCorpAnalysisResponse(
        success=True,
        data=result,
        meta=CorrelationMeta(
            requestId=request_id,
            analysisSessionId=session_id
        )
    )

Contract:

• Correlation in meta (not top-level)
• Resize to 1024px width, max height 1920, min width 480
• Re-encode if > 10MB after resize

POST /v1/validate/face

Face detection and validation:

@router_v1.post(
    "/validate/face",
    response_model=ValidateFaceResponse,
    response_model_exclude_none=True,
)
async def validate_face(
    request: Request,
    file: UploadFile = Depends(ensure_valid_upload),
    yaw_deg: float = Query(...),
    pitch_deg: float = Query(...),
    # ... other thresholds
    include_mesh: bool = Query(False),
):
    """
    Validate face geometry and lighting.
    Returns: { ok, reason?, diagnosis, mesh?, requestId, analysisSessionId }
    """
    # 1. Extract correlation headers
    request_id = request.state.request_id
    session_id = extract_analysis_session_id(request)

    # 2. Downscale to 512px for performance
    image = downscale_image(file, max_size=512)

    # 3. Run validation pipeline
    result = await validate_face_pipeline(image, thresholds)

    # 4. Attach correlation at TOP LEVEL (not meta)
    return ValidateFaceResponse(
        ok=result.ok,
        reason=result.reason,
        diagnosis=result.diagnosis,
        mesh=result.mesh if include_mesh else None,
        requestId=request_id,
        analysisSessionId=session_id,
    )

Contract:

• Correlation at TOP LEVEL (different from analyze endpoint)
• Downscale to 512px max
• All 8 threshold params required

GET /livez, /readyz

Health probes:

@router.get("/livez")
async def liveness():
    """Always returns 200 if process is running."""
    return {"status": "ok"}

@router.get("/readyz")
async def readiness():
    """Returns 200 after FaceMesh warmup, else 503."""
    if not is_ready():
        raise _http_exc(503, "SERVICE_UNAVAILABLE", "Service not ready")
    return {"status": "ready"}

---

Core Patterns

1. Correlation Headers

Extract and propagate correlation headers:

from app_http.headers import (
    extract_request_id,
    extract_analysis_session_id,
    extract_frame_seq,
)

# In route handler
request_id = request.state.request_id  # Set by middleware
session_id = extract_analysis_session_id(request)
frame_seq = extract_frame_seq(request)

# Log with correlation
logger.info({
    "event": "processing_image",
    "requestId": request_id,
    "analysisSessionId": session_id,
    "frameSeq": frame_seq,
})

# Return in response (placement depends on endpoint)
# For /v1/validate/face: top-level
return ValidateFaceResponse(
    ok=True,
    requestId=request_id,
    analysisSessionId=session_id,
)

# For /v1/perfect-corp/analyze: under meta
return PerfectCorpAnalysisResponse(
    success=True,
    data=result,
    meta=CorrelationMeta(
        requestId=request_id,
        analysisSessionId=session_id,
    )
)

2. Error Handling

Use standardized error models:

from errors import AppError, _http_exc, ERROR_CODES

# Option 1: Raise HTTPException with error envelope
if not valid_format:
    raise _http_exc(
        status_code=400,
        error_code="VALIDATION_ERROR",
        message="Invalid image format",
        request_id=request_id,
        frame_seq=frame_seq,
    )

# Option 2: Raise AppError (will be caught by error handler)
if timeout:
    raise AppError(
        error_code="TIMEOUT_ERROR",
        message="Request timed out",
        status_code=408,
        request_id=request_id,
    )

# All errors return:
# { "detail": { "errorCode": "...", "message": "...", "requestId": "...", "frameSeq": "..." } }

Common error codes:

• VALIDATION_ERROR (400)
• UNAUTHORIZED (401)
• FORBIDDEN (403)
• TIMEOUT_ERROR (408)
• IMAGE_PROCESSING_ERROR (500)
• SKIN_ANALYSIS_FAILED (500)
• SERVICE_UNAVAILABLE (503)

3. Access Control

Middleware validates CIDR and shared secret:

# Automatic via middleware_access.py
# Validates:
# 1. Client IP against IMAGE_PROCESSOR_ALLOWED_CIDRS
# 2. X-Internal-Secret header matches IMAGE_PROCESSOR_SHARED_SECRET

# In production, both are required
# In dev/test with mock mode, can be relaxed

Configuration:

IMAGE_PROCESSOR_ALLOWED_CIDRS="10.0.0.0/8,172.16.0.0/12,192.168.0.0/16,127.0.0.1/32"
IMAGE_PROCESSOR_SHARED_SECRET="your-secret-here"

4. Pydantic Models

Define response models with proper nesting:

from pydantic import BaseModel, Field
from typing import Optional

class DiagnosisData(BaseModel):
    pose: PoseResult
    faceRatio: FaceRatioResult
    centering: CenteringResult
    lighting: LightingResult

class ValidateFaceResponse(BaseModel):
    ok: bool
    reason: Optional[str] = None
    diagnosis: DiagnosisData
    mesh: Optional[MeshData] = None
    # Correlation at top-level for this endpoint
    requestId: Optional[str] = Field(None, alias="requestId")
    analysisSessionId: Optional[str] = Field(None, alias="analysisSessionId")

# Use with response_model_exclude_none=True
@router.post("/validate/face", response_model=ValidateFaceResponse, response_model_exclude_none=True)

5. Structured Logging

Use structured JSON logging with context:

import logging

logger = logging.getLogger("image_processor.routes.validate")

# Always include requestId from request.state
logger.info({
    "event": "validation_started",
    "requestId": request.state.request_id,
    "analysisSessionId": session_id,
    "frameSeq": frame_seq,
    "imageSize": len(image_bytes),
})

# On error
logger.error({
    "event": "validation_failed",
    "requestId": request.state.request_id,
    "error": str(e),
    "errorType": type(e).__name__,
})

# Never log secrets
settings = get_settings()
logger.info({
    "event": "config_loaded",
    "mockMode": settings.image_processor_use_mock,
    # ❌ Don't log: settings.image_processor_shared_secret
})

6. Mock Mode

Support mock mode for development:

from config.settings import get_settings

settings = get_settings()

if settings.image_processor_use_mock:
    # Return normalized mock data
    with open(settings.perfect_corp_mock_score_info_path) as f:
        mock_data = json.load(f)
    return normalize_provider_response(mock_data)
else:
    # Call real Perfect Corp API
    result = await client.analyze(image_bytes)
    return result

Configuration:

IMAGE_PROCESSOR_USE_MOCK=true
PERFECT_CORP_MOCK_SCORE_INFO_PATH=score_info.json

7. Image Processing

Resize and normalize images:

from PIL import Image
import io

def process_image_for_provider(file: UploadFile) -> bytes:
    """
    Resize to 1024px width JPEG, cap height at 1920, min width 480.
    Re-encode if > 10MB.
    """
    image = Image.open(file.file)

    # Resize to 1024px width, maintain aspect ratio
    width, height = image.size
    if width > 1024:
        ratio = 1024 / width
        new_height = int(height * ratio)
        # Cap height at 1920
        if new_height > 1920:
            ratio = 1920 / height
            new_height = 1920
            width = int(width * ratio)
        image = image.resize((1024, new_height), Image.Resampling.LANCZOS)

    # Convert to JPEG
    buffer = io.BytesIO()
    image.save(buffer, format="JPEG", quality=95)
    image_bytes = buffer.getvalue()

    # Re-encode if > 10MB
    if len(image_bytes) > 10 * 1024 * 1024:
        buffer = io.BytesIO()
        image.save(buffer, format="JPEG", quality=85)
        image_bytes = buffer.getvalue()

    return image_bytes

8. Validation Pipeline

Run face validation checks:

from validation.pipeline import validate_face_pipeline
from validation.mesh_runtime import get_face_mesh

async def validate_face(image: Image.Image, thresholds: dict) -> dict:
    """
    1. Downscale to 512px
    2. MediaPipe FaceMesh detection
    3. Pose estimation (PnP solver)
    4. Face ratio check
    5. Centering validation
    6. Lighting analysis
    7. Side-lighting gating
    """
    # Downscale for performance
    image = downscale_to_max(image, 512)

    # Run FaceMesh (with concurrency gate)
    mesh = get_face_mesh(static_mode=True)
    results = mesh.process(np.array(image))

    if not results.multi_face_landmarks:
        return {"ok": False, "reason": "NO_FACE_DETECTED"}

    # Run validation checks
    pose_result = check_pose(results, thresholds)
    ratio_result = check_face_ratio(results, image.size, thresholds)
    centering_result = check_centering(results, image.size, thresholds)
    lighting_result = check_lighting(image, thresholds)

    # Overall success
    ok = all([
        pose_result["success"],
        ratio_result["success"],
        centering_result["success"],
        lighting_result["success"],
    ])

    return {
        "ok": ok,
        "diagnosis": {
            "pose": pose_result,
            "faceRatio": ratio_result,
            "centering": centering_result,
            "lighting": lighting_result,
        }
    }

---

Perfect Corp Integration

Authentication Flow

# 1. Generate RSA-encrypted token
token = generate_rsa_token(api_key, secret_key, timestamp)

# 2. Cache token and refresh on 401
if response.status_code == 401:
    token = generate_rsa_token(api_key, secret_key, time.time())
    retry_request()

Full Analysis Flow

# 1. Create file
file_id = await client.create_file(image_bytes, metadata)

# 2. Run task (all 14 conditions by default)
task_id = await client.run_task(file_id)

# 3. Poll status (immediate + retry with backoff)
status = await client.poll_task_status(task_id)

# 4. Download ZIP and extract score_info.json
result = await client.download_and_parse_results(task_id)

# 5. Normalize vendor keys to internal format
normalized = normalize_provider_response(result)

# Program code: (acne_decile - 1) + ((wrinkle_decile - 1) * 10) + 1
# Severity: ≥95 none, ≥80 mild, ≥60 moderate, <60 severe

---

Configuration & Environment

All config via config/settings.py using Pydantic BaseSettings:

from pydantic_settings import BaseSettings
from pydantic import SecretStr

class Settings(BaseSettings):
    # Environment
    image_processor_env: str = "dev"

    # Mock mode
    image_processor_use_mock: bool = False
    perfect_corp_mock_score_info_path: str = "score_info.json"

    # Perfect Corp API
    perfect_corp_api_url: str
    perfect_corp_api_key: str
    perfect_corp_api_secret_key: SecretStr

    # Access control
    image_processor_shared_secret: SecretStr | None = None
    image_processor_allowed_cidrs: str = "10.0.0.0/8,172.16.0.0/12,192.168.0.0/16,127.0.0.1/32"

    # Face Mesh
    face_mesh_concurrency: int = 2
    face_mesh_refine: bool = False

    class Config:
        env_file = ".env"

---

Testing Strategy

Unit Tests

# Test upload validation
def test_upload_validation():
    assert validate_file_size(10 * 1024 * 1024) == True  # 10MB OK
    assert validate_file_size(11 * 1024 * 1024) == False  # > 10MB

# Test normalization
def test_normalize_provider_response():
    result = normalize_provider_response(mock_score_info)
    assert result["programCode"] == expected_code
    assert result["conditions"]["acne"]["severity"] == "mild"

Integration Tests

# Test mock mode
async def test_analyze_mock_mode():
    response = await client.post("/v1/perfect-corp/analyze", files={"file": image})
    assert response.status_code == 200
    assert response.json()["success"] == True

# Test access control
async def test_access_control_missing_secret():
    response = await client.post("/v1/validate/face", files={"file": image})
    assert response.status_code == 401

---

Common Contracts (DO NOT BREAK)

1. Versioning: All new routes under /v1 only
2. Correlation placement:
   • /v1/validate/face: TOP LEVEL (requestId, analysisSessionId)
   • /v1/perfect-corp/analyze: Under meta
3. Error envelope: { "detail": { "errorCode", "message", "requestId?", "frameSeq?" } }
4. Upload limits: 10MB max, JPEG/PNG only
5. Shared secret: Mandatory in production
6. Validation params: All 8 threshold params required for /v1/validate/face
7. Image resize: 1024px width for analyze, 512px max for validate

---

Reference Files

For detailed information:

• Comprehensive docs: apps/image-processor/README.md
• Routes: app_http/routes/*.py
• Provider: providers/perfect_corp/*.py
• Validation: validation/*.py
• Cursor rules: .cursor/rules/image-processor.mdc (may be outdated)
• CLAUDE.md: Image Processor Service section

---

Related Skills

• backend-dev-guidelines - Backend integration patterns
• frontend-dev-guidelines - Frontend camera integration

---

Skill Status: Created for Quantum Skincare ✅ Stack: Python 3.11+, FastAPI, Pydantic v2, MediaPipe, PIL Provider: Perfect Corp API with mock mode support Line Count: Under 500 lines (following Anthropic best practices) ✅