node_modules/@jimp/plugin-dither/src/index.ts

import { JimpClass } from "@jimp/types";

export const methods = {
  /**
   * Apply a ordered dithering effect.
   * @example
   * ```ts
   * import { Jimp } from "jimp";
   *
   * const image = await Jimp.read("test/image.png");
   *
   * image.dither();
   * ```
   */
  dither<I extends JimpClass>(image: I) {
    const rgb565Matrix = [
      1, 9, 3, 11, 13, 5, 15, 7, 4, 12, 2, 10, 16, 8, 14, 6,
    ];

    image.scan((x, y, idx) => {
      const thresholdId = ((y & 3) << 2) + (x % 4);
      const dither = rgb565Matrix[thresholdId]!;

      image.bitmap.data[idx] = Math.min(image.bitmap.data[idx]! + dither, 0xff);
      image.bitmap.data[idx + 1] = Math.min(
        image.bitmap.data[idx + 1]! + dither,
        0xff,
      );
      image.bitmap.data[idx + 2] = Math.min(
        image.bitmap.data[idx + 2]! + dither,
        0xff,
      );
    });

    return image;
  },
};