CBR to PDF Converter 📚

A fast, easy-to-use web application that converts CBR (Comic Book RAR) and CBZ (Comic Book ZIP) files to beautiful, optimized PDF documents. Perfect for reading comics on any device!

Features ✨

• Multi-format Support: Handles both CBR and CBZ archive formats
• Smart Format Detection: Automatically detects archive type using magic bytes with fallback to file extension
• Preserves Quality: High-quality image processing with adjustable compression settings
  • You can select quality through a drag bar.
• A4 Optimized: Images are automatically scaled and centered for A4 paper size
• Batch Conversion: Convert multiple files at once and download as ZIP
• Customization Options:
  • Adjustable quality settings (1-100)
  • Background color selection (white/black)
  • Page range selection (convert specific pages)
• Drag-and-Drop UI: Clean, intuitive interface with drag-and-drop file upload
• Large File Support: Handles files up to 500MB

Tech Stack 🛠️

• Backend: Node.js with Express.js
• File Processing:
  • RAR extraction: node-unrar-js
  • ZIP extraction: adm-zip
  • Image processing: sharp
  • PDF generation: pdf-lib and pdfkit
• Frontend: HTML5 with vanilla JavaScript
• File Upload: Multer (in-memory storage)

Installation 📦

Prerequisites

• Node.js (v14 or higher)
• npm (comes with Node.js)

Steps

1. Clone the repository

   git clone https://github.com/yourusername/cbr-to-pdf-converter.git
   cd cbr-to-pdf-converter

2. Install dependencies

   npm install

3. Start the server

   npm start

   The server will start at http://localhost:3000

4. Open in browser

   http://localhost:3000
   

Usage 🎯

Single File Conversion

1. Click the drop zone or select files
2. Choose your preferences:
   • Quality: Adjust image quality (1-100)
   • Background: Select white or black background
   • Pages: Specify page range (optional)
3. Click "Convert to PDF"
4. PDF will download automatically

Batch Conversion

1. Select multiple CBR/CBZ files
2. Set your preferences
3. Click "Convert All"
4. All PDFs will be zipped and downloaded together

Improved Editor Screen

1. Preview of images
2. Remove unwanted pages
3. Save

API Endpoints 🔌

GET /

Serves the main HTML interface

POST /api/get-page-count

Get the total number of pages in an archive

• Form Data: file (multipart file upload)
• Response: { totalPages: number }

POST /api/convert

Convert a single file to PDF

• Form Data:
  • file: CBR/CBZ file
  • bgColor: 'white' or 'black'
  • quality: 1-100
  • pageStart: Starting page (optional)
  • pageEnd: Ending page (optional)
• Response: PDF file download

POST /api/batch-convert

Convert multiple files to PDF(s)

• Form Data:
  • files: Multiple CBR/CBZ files (up to 20)
  • bgColor: 'white' or 'black'
  • quality: 1-100
• Response: Single PDF (if 1 file) or ZIP archive (if multiple)

Project Structure 📁

cbr-to-pdf-converter/
├── server.js          # Express server & conversion logic
├── package.json       # Dependencies & scripts
├── index.html         # Frontend UI
└── public/            # Static files (served by Express)

Key Features Explained 🔍

Archive Format Detection

The converter uses magic byte signatures to detect file formats:

• RAR: 52 61 72 21 1A 07 00 (Rar!\x1A\x07\x00)
• ZIP: 50 4B 03 04 (PK\x03\x04)

Falls back to file extension if magic byte detection fails.

Natural Sorting

Images are sorted naturally (1, 2, 3... not 1, 10, 100) to ensure correct page order even with different naming conventions.

PDF Generation

• Images are automatically scaled to fit A4 dimensions (595.28 x 841.89 points)
• Maintains aspect ratio
• Centers images on page
• Supports both PNG and JPEG compression

Configuration 🎛️

Edit server.js to modify:

• PORT: Default is 3000
• MAX_FILE_SIZE: Currently 500MB (limits: { fileSize: 500 * 1024 * 1024 })
• A4_DIMENSIONS: A4_WIDTH = 595.28, A4_HEIGHT = 841.89

Error Handling ✅

The application includes comprehensive error handling:

• File format validation
• Archive integrity checks
• Graceful fallback between RAR and ZIP detection
• Detailed error messages for debugging

Performance Tips 🚀

• Quality setting of 75 (default) offers good balance between file size and quality
• Batch conversion is more efficient than converting files individually
• Large archives (500+ pages) may take a few minutes to process

Development 👨‍💻

Debugging

The server logs detailed information during conversion:

📦 Detected RAR archive format
✅ Found 200 images
✅ Total images extracted: 200
✅ Conversion completed: comic.pdf

Dependencies Overview

Package	Version	Purpose
express	^5.2.1	Web server framework
multer	^2.0.2	File upload handling
pdf-lib	^1.17.1	PDF creation
pdfkit	^0.17.2	PDF toolkit
sharp	^0.34.5	Image processing
adm-zip	^0.5.16	ZIP extraction
node-unrar-js	^2.0.2	RAR extraction
archiver	^7.0.1	ZIP creation for batch downloads

Known Limitations ⚠️

• Maximum file size: 500MB (configurable)
• Maximum batch files: 20 at once
• Requires Node.js runtime
• Some systems may need additional RAR library dependencies

Troubleshooting 🔧

Q: "Cannot determine archive type" error

• Ensure the file is a valid CBR or CBZ file
• Try renaming with correct extension

Q: PDF quality is poor

• Increase the quality setting (try 85-95)
• Note: Higher quality = larger file size

Q: Server crashes with large files

• Increase MAX_FILE_SIZE in server.js
• Try converting in smaller batches

Q: Port 3000 already in use

• Change the PORT variable in server.js
• Or kill the process using port 3000

Future Enhancements 🚀

• Image rotation/correction options
• Watermark support
• Progress tracking for large conversions
• Web socket real-time status updates
• Database for conversion history
• Docker containerization
• CLI version for batch processing

License 📄

This project is licensed under the ISC License.

Contributing 🤝

Contributions are welcome! Please feel free to submit a Pull Request.

Credits 🙏

Created as a practical solution for converting digital comic archives to portable PDF format.

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Made with ❤️ for comic readers everywhere