Comic Book Generator

Production-oriented web app that generates comic books from user prompts, keeps visual consistency with reference images, and exports downloadable PDFs.

Architecture

+-------------------+        HTTPS         +-----------------------------+
| Next.js Frontend  | -------------------> | FastAPI Backend (Railway)   |
| (Vercel + Clerk)  |                      | Auth, API, Validation       |
+-------------------+                      +---------------+-------------+
        |                                                    |
        | Clerk auth session                                 | enqueue jobs
        v                                                    v
+-------------------+                                +---------------------+
| Clerk             |                                | Celery Worker       |
| Identity + JWT    |                                | image/pdf pipeline  |
+-------------------+                                +----------+----------+
                                                               |
                           +----------------------+------------+------------+
                           |                      |                         |
                           v                      v                         v
                    +-------------+       +---------------+          +--------------+
                    | PostgreSQL  |       | Redis/Upstash |          | Cloudflare R2|
                    | users/comics|       | rate/jobs     |          | assets + PDFs |
                    +-------------+       +---------------+          +--------------+
                                                               |
                                                               v
                                                   +-----------------------+
                                                   | Replicate + Claude API|
                                                   | image + story pipeline |
                                                   +-----------------------+

Tech Stack

• Next.js 14 App Router
• FastAPI
• PostgreSQL
• Redis
• Celery
• Replicate
• Anthropic Claude API
• Cloudflare R2
• Clerk

Features

• Auth with Clerk and verified backend tokens
• Prompt sanitization and content blocking
• User-based rate limiting and daily comic quotas
• Async comic generation with Celery workers
• Per-user ownership checks on comic resources
• Signed URLs for protected R2 assets
• PDF export pipeline with Pillow + FPDF2

Quick Start

1. Open the app project folder:
   • cd comic-generator
2. Follow setup guides:
   • Backend: backend/README.md
   • Frontend: frontend/README.md
3. Or use the full app guide:
   • README.md inside comic-generator/

Running All Services (Local)

From comic-generator/, run each in a separate terminal:

• Backend API:
  • cd backend
  • uvicorn app.main:app --reload --port 8000
• Celery worker:
  • cd backend
  • celery -A app.workers.celery_app.celery_app worker --loglevel=info --concurrency=2
• Frontend:
  • cd frontend
  • npm run dev

Screenshots

• public/screenshots/home-placeholder.png
• public/screenshots/generator-placeholder.png
• public/screenshots/library-placeholder.png

Running Tests

• Backend:
  • cd backend
  • pytest
• With coverage:
  • pytest --cov=app --cov-report=term-missing
• Frontend quality checks:
  • cd frontend
  • npm run lint
  • npx tsc --noEmit

Required Environment Variables

• See DEPLOYMENT.md for the full, production-ready variable list and source links.

Known Limitations

• Character visual consistency across long runs is approximately 80% and may require retries for best output.
• Queue latency can increase during high load if worker concurrency is low.

Estimated Usage Cost

Approximate per-comic cost (depends on page count and model settings):

• Replicate image generation: $0.03 - $0.20
• Claude story generation: $0.005 - $0.04
• Cloudflare R2 storage + egress: < $0.01 typical per comic
• Total rough range: $0.04 - $0.25 per comic