134 lines
4.5 KiB
Markdown
134 lines
4.5 KiB
Markdown
# PNGer Development & Technical Instructions
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## Project Overview
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PNGer is a single-container web application for PNG editing and resizing, designed for deployment on Unraid with Gitea version control. It features a modern Svelte frontend and a high-performance Node.js/Sharp backend.
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## Technical Architecture
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### Architecture Overview
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PNGer uses a multi-layered architecture designed for responsiveness and efficiency:
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```mermaid
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graph TD
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A[User Browser] --> B[Svelte Frontend]
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B --> C[Canvas API (Live Preview)]
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B --> D[Express API (Backend)]
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D --> E[Sharp Image Library]
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D --> F[Runtime Environment (Docker)]
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```
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### Backend (Express + Sharp)
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The backend is built with Node.js and TypeScript, using Express for the API and Sharp for high-performance image processing.
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**Key Endpoints:**
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- `POST /api/transform` - Transform image (resize, crop, compress, convert)
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- `GET /api/health` - Health check
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**Key Dependencies:**
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- `sharp`: High-performance image processing (handles resizing, cropping, and format conversion).
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- `multer`: Middleware for handling `multipart/form-data`, used for file uploads.
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- `express`: Web framework for the API.
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### Frontend (Svelte + Vite)
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The frontend is a reactive Svelte application that prioritizes real-time feedback and UX.
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**Core Components & Modules:**
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- `App.svelte`: Main application container managing state and UI.
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- `lib/api.ts`: API client for backend communication.
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- `lib/preview.ts`: Client-side preview logic using the Canvas API for instant feedback.
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- `lib/theme.ts`: Dark/light theme management with persistent storage.
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- `lib/presets.ts`: Configuration for smart image presets.
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### Design System (Dark/Light Modes)
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The UI uses a modern design system with CSS custom properties for theming:
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- **Light Mode**: Clean white background with dark gold (`#b8860b`) accents.
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- **Dark Mode**: Deep black (`#0a0a0a`) background with light gold (`#daa520`) accents.
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- **Transparencies**: Dark/Light toggling allows users to inspect PNG transparency against different backgrounds.
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## Implementation Details
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### Live Preview System
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Live preview is implemented using a client-side Canvas-based approach to provide instant feedback (< 100ms) without server round-trips.
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**How it works:**
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1. User uploads an image.
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2. The browser loads the image into an HTML5 Canvas.
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3. On any parameter change (width, quality, etc.), a debounced (300ms) update applies transformations to the canvas.
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4. The canvas content is displayed side-by-side with the original for comparison.
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5. File sizes are estimated from the Canvas data URL to provide immediate feedback on optimization savings.
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### Docker Strategy & Fixes
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PNGer uses a multi-stage Docker build to minimize image size and maximize security.
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**Optimization Fixes applied:**
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- **Dependency Installation**: Uses `npm install` instead of `npm ci` to handle missing lockfiles gracefully while maintaining stability via caret ranges in `package.json`.
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- **Security**: Runs as a non-root `node` user in the final Alpine-based image.
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- **Multer Upgrade**: Upgraded to `v2.1.0` for improved security and performance.
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## Local Development Setup
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### Prerequisites
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- Node.js 20+
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- npm or pnpm
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- Docker (optional)
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### Setup Steps
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```bash
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# Clone repository
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git clone https://git.alwisp.com/jason/pnger.git
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cd pnger
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# Setup backend
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cd backend
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npm install
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npm run dev
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# Setup frontend (separate terminal)
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cd frontend
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npm install
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npm run dev
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```
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### Environment Variables
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**Backend (.env):**
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- `PORT`: 3000 (internal)
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- `MAX_FILE_SIZE`: 10485760 (10MB default)
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- `CORS_ORIGIN`: http://localhost:5173
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**Frontend (.env):**
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- `VITE_API_URL`: http://localhost:3000/api
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## Development Workflow & Standards
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### Workflow
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1. **Feature Branch**: Create from `main`.
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2. **Develop**: Use hot-reload (`npm run dev`).
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3. **Test**: Perform manual testing of image operations and presets.
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4. **Commit**: Use `type: description` format (e.g., `feat: add rotation`).
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5. **Merge**: Merge into `main` after review.
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### Code Standards
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- **TypeScript**: Use strict types where possible.
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- **Svelte**: Keep components modular and under 300 lines.
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- **Async/Await**: Use for all asynchronous operations.
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- **Semantic HTML**: Ensure accessibility and proper structure.
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## Troubleshooting
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- **Port in use**: `lsof -ti:3000 | xargs kill -9`
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- **Sharp issues**: `npm rebuild sharp`
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- **Docker Cache**: `docker builder prune` if builds fail unexpectedly.
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- **Preview Glitches**: Check browser console for Canvas API errors.
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---
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**Last Updated**: March 12, 2026 |