PoseCompose

Create realistic group photos by compositing individual people into a background scene using Google Gemini. Upload one background photo and multiple subject photos, remove backgrounds for subjects, arrange them, and generate a final composite image.

Live Production: https://posecompose.com (canonical) and https://www.posecompose.com (content host)

Table of Contents

• Overview
• Features
• Architecture
• Frontend (Vite/React/TS)
• Backend API Proxy (Express)
• Infrastructure (Nginx, TLS, domains)
• Local Development
• Build & Artifacts
• Deployments
• Configuration
• Security
• Caching & Performance
• Operational Runbook
• Troubleshooting
• Directory Structure
• Roadmap / Future Improvements

Overview

PoseCompose is a static, single‑page application (SPA) built with Vite + React + TypeScript and styled with Tailwind + shadcn/ui. It communicates with a small server‑side Node/Express proxy that calls Google’s Generative Language (Gemini) API using a server‑held API key. The server key is never embedded in the browser bundle or exposed to clients.

Features

• Upload a background photo (or choose a sample scene).
• Upload multiple person photos; remove backgrounds per person.
• Arrange (order) selected people for composition.
• Choose output aspect ratios and social formats.
• Generate a final composite image via the Gemini API.
• Download/view generated results.

Architecture

• Frontend: Vite + React + TypeScript SPA compiled to static assets (HTML/CSS/JS) in dist/.
• Backend: Node/Express service running on 127.0.0.1:4005 provides a single endpoint:
  • POST /api/gemini/generate-content → forwards to Google’s Gemini generateContent endpoint using the server‑held API key.
• Nginx:
  • Serves static assets for the site (domain root).
  • Proxies /api/ requests to the backend service.
  • TLS is provided by Let’s Encrypt via Certbot; HSTS is enabled.
  • Apex domain redirects permanently to the www host for canonicalization.

Frontend (Vite/React/TS)

• Entry: index.html, source under src/.
• UI toolkit: Tailwind CSS + shadcn/ui components.
• Key components:
  • GroupPhotoGenerator.tsx – orchestrates steps and generation flow.
  • BackgroundUpload.tsx – background chooser and file uploads.
  • PersonUpload.tsx – person photo uploads; triggers background removal.
  • PersonSelection.tsx – selection and ordering of subjects.
  • ResultDisplay.tsx – shows/completes the generated composite.
  • FormatSelection.tsx – social format presets and aspect ratios.
• Image processing (client‑side):
  • Background removal is done via API calls to Gemini.
  • People images are drawn side‑by‑side on a temporary canvas and then composited into a final canvas sized to the target aspect ratio. The stitched “people strip” is exported as JPEG to ensure compatibility with the upstream API.
  • The final request sends two inline images to Gemini: the background (JPEG) and the stitched people (JPEG).

Backend API Proxy (Express)

• Location on server: /opt/posecompose-api.
• Service file: /etc/systemd/system/posecompose-api.service (enabled at boot).
• Env file (owner root, mode 600): /etc/posecompose-api.env containing:
  • GEMINI_API_KEY=<YOUR_SERVER_SIDE_KEY> (stored securely, never sent to clients)
  • PORT=4005
• Server code: server.js uses Express JSON body parsing and forwards requests to:
  • https://generativelanguage.googleapis.com/v1beta/models/gemini-2.5-flash-image-preview:generateContent
  • API key is supplied via x-goog-api-key header.
• Health endpoint: GET /healthz → { ok: true }.
• JSON body limit: 30 MB (to match Nginx limits and large base64 payloads).

Infrastructure (Nginx, TLS, domains)

• Static site root: /var/www/apps/posecompose (deployed build artifacts).
• Vhost: /etc/nginx/sites-available/posecompose.com (symlinked in sites-enabled).
• Canonical host: www.posecompose.com serves content; apex posecompose.com redirects 301 to https://www.posecompose.com.
• TLS: Let’s Encrypt/Certbot, auto‑renewal timer managed by systemd.
• Security headers: HSTS, X‑Content‑Type‑Options, X‑Frame‑Options, Referrer‑Policy.
• Caching:
  • HTML (root/index.html): Cache-Control: no-store, no-cache, must-revalidate, max-age=0.
  • Assets (.css/.js/.png/.jpg/.jpeg/.gif/.svg/.ico/.webmanifest): Cache-Control: public, max-age=604800, immutable with 7‑day expiry.
• Favicon: explicitly disabled (returns 204 with no-store) to avoid stale icons.

Local Development

Requirements

• Node.js 18+ and npm

Install and run

npm ci
npm run dev

Open http://localhost:8080

Build & Artifacts

Build for production

npm run build

Outputs to dist/ with hashed assets and index.html for static hosting at a domain root. If hosting under a subpath (e.g., /apps/posecompose/), build with a base path:

npm run build -- --base=/apps/posecompose/

Deployments

Static files

• Deployed to: /var/www/apps/posecompose
• Helper command on the server:

/usr/local/bin/deploy_static /root/Projects/apps/posecompose-repo/dist posecompose

Nginx vhost (summary)

• Content host (HTTPS): www.posecompose.com serves from /var/www/apps/posecompose and proxies /api/.
• Apex redirect (HTTPS): posecompose.com → https://www.posecompose.com$request_uri.
• HTTP: both apex and www redirect to HTTPS www.

Backend service management

# Check status
systemctl status posecompose-api.service

# View logs
journalctl -u posecompose-api -n 200 -f

# Restart after changes
sudo systemctl restart posecompose-api.service

Nginx operations

sudo nginx -t && sudo systemctl reload nginx

Configuration

Environment / Secrets

• Google Gemini API key is stored server‑side in /etc/posecompose-api.env and read by the backend service.
• Do not embed keys in the frontend; the app calls the server proxy at /api/gemini/generate-content.

Body/Request Sizes

• Nginx client_max_body_size = 30 MB on the vhost.
• Express JSON limit = 30 MB.

Domains & Canonicalization

• Canonical content domain: www.posecompose.com.
• Apex posecompose.com always 301 redirects to the www host to avoid split caching and ensure consistent linking.

Security

• API key protection: Key exists only in /etc/posecompose-api.env, never sent to the client or stored in static assets.
• TLS + HSTS: Enforced via Nginx configuration; renewals handled by Certbot.
• Favicon disabled: Prevents stale browser caching of icons when branding changes.
• Optional hardening not yet enabled (candidates):
  • Content Security Policy (CSP) tuned for the current stack.
  • Nginx rate‑limiting on /api/ to mitigate abuse.

Caching & Performance

• HTML is marked as no‑store/no‑cache to prevent stale app shells.
• Static assets are long‑cached and content‑hashed, safe to cache for 7 days.
• Client uses canvas compositing and exports JPEG (quality 0.9) to reduce payload size and maximize API compatibility.

Operational Runbook

Deploy a new build

cd /root/Projects/apps/posecompose-repo
npm ci
npm run build
/usr/local/bin/deploy_static dist posecompose
sudo nginx -t && sudo systemctl reload nginx

Rotate the API key

sudo editor /etc/posecompose-api.env   # update GEMINI_API_KEY
sudo systemctl restart posecompose-api.service

Check backend health

curl -s http://127.0.0.1:4005/healthz

Troubleshooting

Symptoms and remedies:

• 404 on /api/gemini/generate-content:

  • Ensure Nginx keeps the /api/ prefix intact: proxy_pass http://127.0.0.1:4005; (no trailing slash).
  • Confirm backend is running: systemctl status posecompose-api.service.

• 413 Request Entity Too Large:

  • Increase Nginx client_max_body_size and Express JSON limit (both set to 30 MB here).

• 400 INVALID_ARGUMENT from Gemini:

  • Ensure images are sent as JPEG (no alpha) and sizes are reasonable. The app exports stitched people as JPEG.
  • Retry with smaller images or fewer subjects if bandwidth‑constrained.

• Apex shows old version while www is fresh:

  • This app enforces apex → www redirect to avoid split cache. If you ever disable the redirect, keep HTML no‑store headers.

Directory Structure

apps/posecompose-repo/
├─ index.html
├─ package.json
├─ vite.config.ts
├─ public/
│  ├─ placeholder.svg
│  └─ robots.txt
├─ src/
│  ├─ components/
│  │  ├─ GroupPhotoGenerator.tsx
│  │  ├─ BackgroundUpload.tsx
│  │  ├─ PersonUpload.tsx
│  │  ├─ PersonSelection.tsx
│  │  ├─ ResultDisplay.tsx
│  │  ├─ FormatSelection.tsx
│  │  └─ ui/*
│  └─ main.tsx …
└─ dist/ (build output)

Roadmap / Future Improvements

• Add CSP and strict security headers tailored to current external resources (Google Fonts, etc.).
• Implement Nginx rate limiting for /api/ to throttle abusive traffic.
• Add GitHub Actions workflow for automated build/deploy over SSH.
• Add client‑side downscaling of very large uploads to reduce latency.
• Optional branding (favicon/social image) pipeline.