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# Luna OCR Backend
Real OCR processing backend using Gemini AI for intelligent text extraction and formatting.
## 🚀 Quick Start
### 1. Install Dependencies
```bash
cd server
npm install
```
### 2. Start the Server
```bash
npm start
# or for development with auto-reload:
npm run dev
```
### 3. Test the API
```bash
curl http://localhost:3001/api/health
```
## 📡 API Endpoints
### Health Check
```
GET /api/health
```
### OCR Processing
```
POST /api/ocr
Content-Type: multipart/form-data
Parameters:
- file: Image file (PNG, JPG, WebP) or PDF
- apiKey: Google Gemini API key
- mode: "standard" or "structured"
```
## 🔧 Configuration
### Environment Variables
Create a `.env` file (optional):
```
PORT=3001
MAX_FILE_SIZE=10485760
```
### Supported File Types
- **Images**: PNG, JPG, JPEG, WebP
- **Documents**: PDF (converted to images)
- **Max Size**: 10MB per file
## 🎯 Processing Modes
### Standard Mode
- Uses Gemini 1.5 Flash (faster)
- Returns clean plain text
- Good for simple text extraction
### Structured Mode
- Uses Gemini 1.5 Pro (more intelligent)
- Returns formatted Markdown
- Creates tables, headers, lists automatically
- Perfect for complex documents
## 📊 Response Format
```json
{
"success": true,
"data": {
"fileName": "document.png",
"fileSize": 1234567,
"processingMode": "structured",
"extractedText": "# Document Title\n\n...",
"formats": {
"txt": "plain text version",
"md": "markdown version",
"json": { "metadata": {...}, "content": {...} }
},
"metadata": {
"characterCount": 1500,
"wordCount": 250,
"lineCount": 45,
"processedAt": "2024-01-01T12:00:00.000Z"
}
}
}
```
## 🛠️ Development
### Project Structure
```
server/
├── server.js # Main server file
├── package.json # Dependencies
├── uploads/ # Temporary file storage
└── README.md # This file
```
### Key Features
- **Image Enhancement**: Automatic image preprocessing for better OCR
- **Smart Formatting**: Gemini AI creates beautiful Markdown output
- **Multiple Formats**: Returns TXT, MD, and JSON formats
- **Error Handling**: Comprehensive error handling and cleanup
- **File Cleanup**: Automatic temporary file cleanup
## 🔑 Getting Gemini API Key
1. Go to [Google AI Studio](https://makersuite.google.com/app/apikey)
2. Create a new API key
3. Copy the key and use it in the frontend
## 🚨 Troubleshooting
### Common Issues
**"Cannot connect to OCR backend"**
- Make sure server is running: `npm start`
- Check port 3001 is not in use
- Verify no firewall blocking
**"Invalid API key"**
- Check your Gemini API key is correct
- Ensure API key has proper permissions
- Try creating a new API key
**"File too large"**
- Maximum file size is 10MB
- Compress images before uploading
- For PDFs, try splitting into smaller files
**"Processing failed"**
- Check image quality (not too blurry)
- Ensure text is clearly visible
- Try different processing mode
### Debug Mode
Set `NODE_ENV=development` for detailed logging:
```bash
NODE_ENV=development npm start
```
## 📝 Notes
- Server runs on port 3001 by default
- Temporary files are automatically cleaned up
- CORS is enabled for frontend integration
- Image enhancement improves OCR accuracy
- Gemini AI provides intelligent text formatting
## 🔗 Integration
The backend integrates seamlessly with the Luna OCR React frontend. Make sure both are running:
1. **Backend**: `cd server && npm start` (port 3001)
2. **Frontend**: `npm start` (port 3000)
The frontend will automatically call the backend API for real OCR processing! |