ico-codec

Zero-dependency ICO encoder. Combine PNG images into a valid .ico file.
Works in browser and Node.js.

Install

npm install ico-codec

Usage

import { encodeIco } from "ico-codec";

// Each entry is a PNG buffer at a specific icon size
const ico = encodeIco([
  { size: 16, data: png16Buffer },
  { size: 32, data: png32Buffer },
  { size: 48, data: png48Buffer },
]);

// ico is a Uint8Array — write it to a file, create a Blob, etc.
const blob = new Blob([ico], { type: "image/x-icon" });

A convenience encodeIcoBlob() is also exported for browser use:

import { encodeIcoBlob } from "ico-codec";

const blob = encodeIcoBlob([
  { size: 16, data: png16Buffer },
  { size: 32, data: png32Buffer },
]);
// blob is a Blob with type "image/x-icon"

API

encodeIco(images: IcoImage[]): Uint8Array

Encodes an array of PNG images into a single ICO file. Returns a Uint8Array.

encodeIcoBlob(images: IcoImage[]): Blob

Same as encodeIco() but returns a Blob with MIME type image/x-icon.

IcoImage

interface IcoImage {
  size: number; // Icon dimension in pixels (e.g. 16, 32, 48, 256)
  data: ArrayBuffer | Uint8Array; // Raw PNG file data
}

How it works

The ICO format is a container that bundles multiple PNG images at different resolutions into a single file. This encoder writes the ICO header, one directory entry per image, then concatenates the raw PNG data. No image processing or re-encoding — your PNGs are embedded as-is.

License

MIT — extracted from LeanImg.