Lossy PNG Quantization

pngquant() targets the imagemin-pngquant@10.0.0 interface. It runs a separate pngquant sidecar backed by libimagequant for RGBA palettes, semi-transparent edges, and quality-floor behavior.

Usage

import imagemin, { pngquant } from "imagemin-rs";

const output = await imagemin.buffer(input, {
  plugins: [
    pngquant({
      quality: [0.6, 0.8],
      speed: 3,
      dithering: 1,
      strip: true,
    }),
  ],
});

interface PngquantOptions {
  speed?: number; // integer 1..11
  strip?: boolean;
  quality?: [number, number]; // each value 0..1
  dithering?: number | boolean; // 0..1 or false
  posterize?: number;
}

When speed is omitted, the fixed binary chooses its default. false dithering maps to upstream --ordered; numeric values map to --floyd=<value>. If the quality floor cannot be met, pngquant exits with code 99 and the plugin returns the original input.

Safety and compatibility

pngquant 3.0.3 and its pinned libimagequant source are GPL-3.0-or-later executables invoked only through a child process. They are not linked into the MIT native addon. Input, output, stderr, execution time, and decoded dimensions all have hard limits.

Ordinary PNG results are byte-compared with imagemin-pngquant@10.0.0 across the option matrix. imagemin-rs additionally rejects unknown options synchronously and passes APNG through to avoid silently losing animation.

Eight platform packages contain SHA-256 provenance, source references, and the complete GPL license. There are no runtime downloads or installation-time builds.