Rastermill

Fast, portable image processing for Node agents. Rastermill runs in-process with Photon for the common formats and falls back to native tools (sips, ImageMagick, GraphicsMagick, ffmpeg, or the Windows System.Drawing stack) when a format or operation needs an external codec.

import { createRastermill } from "rastermill";

const rastermill = createRastermill({ limits: { inputPixels: 25_000_000 } });

const info = await rastermill.probe(imageBuffer);
const jpeg = await rastermill.encode(imageBuffer, {
  format: "jpeg",
  resize: { maxSide: 1600 },
  quality: 85,
});
// => { data, format: "jpeg", mimeType: "image/jpeg", width, height, bytes, metadata: "stripped", resized, chosen }

Every method accepts a Buffer, Uint8Array, or ArrayBuffer as input.

#Features

Page	What it covers
Configuration	`createRastermill`, options, pixel budgets, custom command resolution
Backends	Execution modes, backend selection order, and automatic fallback
`probe`	Read format, width/height, alpha, and orientation without decoding
`transparency`	Decode common raster formats and inspect alpha channels/pixels
`encode`	Exact-format encode, auto format choice, byte budgets, dimension limits, metadata policy, and HEIC/AVIF → JPEG
Error handling	`RastermillUnavailableError`, `isRastermillUnavailableError`

#Two ways to call

Create a configured instance with createRastermill(options), or use the default-configured module functions: probe, transparency, and encode are exported directly and lazily create a default Rastermill instance on first use.

#Safety model

Rastermill refuses to process images it can't size up. It rejects images with unknown dimensions, inputs larger than limits.inputPixels, and resize targets larger than limits.outputPixels. External tools run with a timeout and a bounded output buffer. See Configuration for the knobs.

Encoded outputs strip metadata by default. metadata: "preserve" is a passthrough-only fast path: it preserves metadata only when the original bytes can be returned unchanged. Photon does not expose EXIF/GPS/ICC/XMP metadata APIs, so any real transform reports metadata: "stripped".