SnapOtter/packages/image-engine/src/operations/sepia.ts

import type { Sharp } from "../types.js";

// Standard sepia tone matrix
const SEPIA_MATRIX: [[number, number, number], [number, number, number], [number, number, number]] =
  [
    [0.393, 0.769, 0.189],
    [0.349, 0.686, 0.168],
    [0.272, 0.534, 0.131],
  ];

export async function sepia(image: Sharp): Promise<Sharp> {
  return image.recomb(SEPIA_MATRIX);
}