JPEG File Format

What is JPEG?

JPEG (Joint Photographic Experts Group) is a digital image compression standard that uses lossy compression. Standardized in 1992, it remains one of the most widely used image formats today.

Key Features

• Lossy compression: Significantly reduces file size but loses some image information
• Adjustable compression: Balance between quality and file size can be controlled
• 24-bit color: Can display up to 16.7 million colors
• Progressive encoding: Images load gradually from blurry to sharp
• EXIF data: Can store metadata like camera settings and date

Advantages of JPEG

• Optimized for photographic images with small file sizes
• Supported by virtually all devices and software
• Fast loading speeds
• Compression ratio can be adjusted for different uses
• Suitable for images with rich colors

Disadvantages of JPEG

• No transparency (alpha channel) support
• Quality degrades with repeated editing
• Not suitable for images with text or sharp edges
• Compression artifacts (blocking) may occur

Compression Process

JPEG compression involves the following steps:

1. Color space conversion: Convert RGB to YCbCr
2. Downsampling: Reduce chrominance information
3. DCT transformation: Apply Discrete Cosine Transform
4. Quantization: Remove high-frequency components
5. Entropy coding: Final compression with Huffman coding

JPEG Variants

• JPEG 2000: Better compression and quality, but limited support
• JPEG XR: Microsoft-developed format with HDR support
• JPEG XL: Next-generation image format, supports lossless compression too

Use Cases

• Digital photography
• Web images (backgrounds, product photos, etc.)
• Social media images
• Email attachments
• Default format for digital cameras

Quality Settings Guide

• 100-95%: Highest quality, large file size
• 94-85%: High quality, reasonable file size
• 84-75%: Standard quality for web
• 74-65%: Acceptable quality, small files
• Below 64%: Low quality, visible compression artifacts