JPEG Optimization

The two JPEG adapters have different semantics: mozjpeg() re-encodes pixels and supports lossy quality control, while jpegtran() transforms JPEG coefficients losslessly but removes marker metadata to match upstream.

MozJPEG

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

const output = await imagemin.buffer(input, {
  plugins: [
    mozjpeg({
      quality: 80,
      progressive: true,
      tune: "ssim",
    }),
  ],
});

mozjpeg() targets imagemin-mozjpeg@10.0.0:

interface MozjpegOptions {
  quality?: number; // 0..100
  progressive?: boolean;
  targa?: boolean;
  revert?: boolean;
  fastCrush?: boolean;
  dcScanOpt?: number; // integer 0..2
  trellis?: boolean;
  trellisDC?: boolean;
  tune?: "psnr" | "hvs-psnr" | "ssim" | "ms-ssim";
  overshoot?: boolean;
  arithmetic?: boolean;
  dct?: "int" | "fast" | "float";
  quantBaseline?: boolean;
  quantTable?: number; // integer 0..5
  smooth?: number; // integer 1..100
  maxMemory?: number; // positive safe integer
  sample?: string[]; // for example ["2x2", "1x1", "1x1"]
}

Progressive JPEG is the default. Fixed fixtures match imagemin-mozjpeg@10.0.0 byte-for-byte across default and advanced option matrices. One upstream bug is intentionally fixed: quantBaseline: true emits the correct valueless flag instead of an extra true filename.

jpegtran

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

const output = await imagemin.buffer(input, {
  plugins: [jpegtran({ progressive: true })],
});

interface JpegtranOptions {
  progressive?: boolean;
  arithmetic?: boolean;
}

Like imagemin-jpegtran@8.0.0, this adapter always uses -copy none. Pixels and DCT coefficients remain lossless, but EXIF orientation, ICC profiles, and comments are removed. Do not use this compatibility entry point when those metadata are required for correct display.

Isolation and release boundary

Both adapters execute constrained sidecars rather than linking their codec into the MIT native addon. Limits cover input, output, stderr, execution time, and decoded dimensions. Non-JPEG input passes through; malformed JPEG-signature input returns a codec error.

Production packages contain project-built MozJPEG 4.1.1 cjpeg and jpegtran, binary hashes, source provenance, and complete licenses. Byte parity is promised only within the pinned encoder version.