How Image Compression Works (With Simple Examples)
Published by ImageCompressor | Updated 2025
This article explains the core concepts behind image compression, including color reduction, DCT, quantization, and entropy coding, with clear examples of how these methods reduce file size while maintaining acceptable quality. Ideal for beginners and developers alike.
Types of Compression
Lossless and lossy compression offer different trade-offs. Lossless retains all pixel data (PNG, GIF), while lossy (JPEG, WebP) removes subtle color changes for higher savings.
Key Techniques
- DCT: Converts image blocks into frequency values.
- Quantization: Rounds off less-important frequencies.
- Huffman Coding: Efficiently stores repeating values.
Real-World Example
Uncompressed: 1.2MB → JPEG: 250KB (no visible difference)
Best Practices
- Use lossy for photos (JPEG, WebP)
- Use lossless for graphics, logos (PNG)
- Preview quality vs size when compressing