JPEG Encoder - DSP Image Compression

Educational JPEG encoder demonstrating Digital Signal Processing techniques in image compression.

Live Demo: https://sem1-cercetare.danielwagner.ro
Paper: See referat/ for academic documentation (Romanian)

Features

• Complete ITU-T T.81 baseline JPEG encoder in C++17
• YCbCr 4:2:0 color encoding with DCT-II transform
• Web UI for interactive visualization (React + Node.js)
• Quality vs compression analysis tools

Quick Start

Build C++ Encoder

cd build
cmake ..
cmake --build . --config Release

Run Web UI

# Backend
cd ui/backend && npm install && npm run dev

# Frontend (new terminal)
cd ui/frontend && npm install && npm run dev

Open http://localhost:3000

CLI Usage

./jpegdsp_cli_encode --input image.png --output out.jpg --quality 75

Project Structure

├── include/jpegdsp/    # C++ headers (core, transforms, jpeg)
├── src/                # C++ implementation
├── ui/
│   ├── backend/        # Node.js API server
│   └── frontend/       # React visualization
├── referat/            # Academic paper (Romanian)
└── data/               # Test images

Architecture

The encoder follows the standard JPEG pipeline:

1. RGB → YCbCr color conversion
2. 4:2:0 chroma subsampling
3. 8×8 block DCT transform
4. Quantization with quality scaling
5. Zig-zag scan + RLE + Huffman coding
6. JFIF bitstream generation

References

• ITU-T T.81 (JPEG Standard)
• Ahmed et al., "Discrete Cosine Transform" (1974)
• Wallace, "The JPEG Still Picture Compression Standard" (1991)

Author

Daniel Wagner - Master ETTI, Research Course TCSI 2025-2026