Add optional Web Worker support to prevent UI blocking on large images

[tapava]

Hey! I've been using Jimp for some image processing in a web app and ran into the classic problem: processing large images (5MB+) blocks the main thread and freezes the UI.

I built a library called ComputeKit that makes it easy to run CPU-heavy work in Web Workers, and, in my opinion, works great with Jimp:

import { ComputeKit } from '@computekit/core';
import Jimp from 'jimp';

const kit = new ComputeKit();

// Register Jimp operations to run off-thread
kit.register('processImage', async (buffer: ArrayBuffer) => {
  const image = await Jimp.read(Buffer.from(buffer));
  await image.blur(10).greyscale().resize(800, 600);
  return image.getBufferAsync(Jimp.MIME_JPEG);
});

// UI stays responsive during processing
const result = await kit.run('processImage', imageBuffer);

Would there be interest in adding native worker support to Jimp? A few approaches:

1. Optional flag - Jimp.read(image, { useWorker: true })
2. Separate export - import { JimpWorker } from 'jimp/worker'
3. Documentation - Just document how users can do this themselves

I'm happy to help with implementation if this is something you'd consider.

Thanks for reading!