@thi.ng/pixel-dither/dither.js

Extensible image dithering w/ various algorithm presets

import { __range } from "@thi.ng/pixel/internal/range";
const ditherWith = (kernel, img, opts = {}) => {
  const { bleed = 1, threshold = 0.5, channels } = opts;
  const { format, width, height } = img;
  const { ox, oy, weights, shift } = kernel;
  let p, err;
  for (let cid of channels || __range(format.channels.length)) {
    const cimg = img.getChannel(cid);
    const chan = format.channels[cid];
    const $thresh = chan.num * threshold;
    const $max = chan.mask0;
    const data = new Int32Array(cimg.data);
    for (let y = 0; y < height; y++) {
      for (let x = 0, i = x + y * width; x < width; x++, i++) {
        p = data[i] < $thresh ? 0 : $max;
        err = (data[i] - p) * bleed;
        data[i] = p;
        if (!err) continue;
        for (let j = ox.length; j-- > 0; ) {
          const xx = x + ox[j];
          const yy = y + oy[j];
          if (yy >= 0 && yy < height && xx >= 0 && xx < width) {
            data[yy * width + xx] += err * weights[j] >> shift;
          }
        }
      }
    }
    cimg.data.set(data);
    img.setChannel(cid, cimg);
  }
  return img;
};
export {
  ditherWith
};