Image Format Comparison Tool

A web-based tool for comparing image compression formats (AVIF, WebP, PNG, JPEG) side-by-side with quality metrics.

Features

• Multiple formats: AVIF, WebP, PNGquant, cjpeg (libjpeg-turbo), OptiPNG
• Quality slider: Adjust compression quality from 10-100
• DSSIM metric: Visual quality difference measurement
• Side-by-side comparison: Original vs compressed with synced zoom/pan
• Hold-to-compare: Quick toggle between original and compressed
• URL persistence: Share specific image/format/quality combinations
• Keyboard shortcuts: Arrow keys for navigation, R for random, Z for zoom reset, Space for compare

Requirements

• PHP 7.4+ with exec() enabled
• Image tools:
  • avifenc / avifdec (libavif)
  • cwebp / dwebp (libwebp)
  • pngquant
  • optipng
  • cjpeg / djpeg (libjpeg-turbo)
  • dssim

Alpine Linux

apk add libavif-apps libwebp-tools pngquant optipng libjpeg-turbo-utils dssim

Ubuntu/Debian

apt install libavif-bin webp pngquant optipng libjpeg-turbo-progs
# dssim needs to be compiled from source or installed via cargo

Installation

1. Clone the repository
2. Copy config.sample.php to config.php
3. Edit config.php to set $uploadsDir to your images directory
4. Ensure the cache/ directory is writable by the web server
5. Access via web browser

Usage

• Use arrow keys or buttons to navigate images
• Select format and adjust quality
• Scroll/pinch to zoom, drag to pan (synced on both sides)
• Hold "Compare" button or spacebar to see original on right side
• Double-click to reset zoom

License

MIT