worker.js

import { GIFEncoder, quantize, applyPalette } from "/src/index.js";

let options;

self.addEventListener("message", (ev) => {
  const detail = ev.data;
  if (detail.event === "init") {
    // Upon init, save our options
    options = { ...detail };
    // And send back a ready event
    self.postMessage("ready");
  } else {
    // Get the options for the encoder
    const {
      format = "rgb444",
      width,
      height,
      maxColors = 256,
      repeat = 0,
      delay = 0,
    } = options;

    // Get the data + index for this frame
    const [data, frame] = detail;

    // Get palette from this frame
    const palette = quantize(data, maxColors, { format });

    // Now get an indexed bitmap image
    const index = applyPalette(data, palette, format);

    // Encode into a single GIF frame chunk
    const gif = GIFEncoder({ auto: false });
    gif.writeFrame(index, width, height, {
      first: frame === 0,
      repeat: 0,
      delay,
      palette,
    });

    // Send the result back ot main thread
    const output = gif.bytesView();
    self.postMessage([output, frame], [output.buffer]);
  }
});