Skip to content
Web Image Formats Research Web Image Formats Research

Measure image quality

Quality measurement is integrated into the pipeline — there is no separate measurement step. When you run just pipeline, each encoded image is measured automatically before moving to the next source image.

How it works

Section titled “How it works”

For every encoded variant, the pipeline measures four metrics:

  • SSIMULACRA2 — perceptual quality (higher is better)
  • PSNR — peak signal-to-noise ratio in dB (higher is better)
  • SSIM — structural similarity, 0–1 (higher is better)
  • Butteraugli — perceptual distance (lower is better)

Results are saved to data/metrics/<study-id>/quality.json.

Running measurements

Section titled “Running measurements”
Terminal window
just pipeline format-comparison 30m

This encodes and measures in a single pass. See Run the pipeline for time budgets and advanced options.

Verifying tools

Section titled “Verifying tools”

The measurement tools must be available in the environment:

Terminal window
just verify-tools

All tools (ssimulacra2, butteraugli_main, ffmpeg) are pre-installed in the dev container.

See also

Section titled “See also”