How to handle premultiplied images in JS

[skycoop]

I'm using sharp to resize the images for use with thumbhash with user uploaded images like so

const { data, info } = await sharp(image)
  .resize({ width: 100, height: 100, fit: "inside" })
  .ensureAlpha()
  .raw()
  .toBuffer({ resolveWithObject: true });

console.log(info)
/*
  {
    format: 'raw',
    width: 100,
    height: 100,
    channels: 4,
    depth: 'uchar',
    premultiplied: true,
    size: 40000
  }
*/

const thumbhash = rgbaToThumbHash(info.width, info.height, data);

I noticed that sharp is outputting premultiplied images depending on the import format (PNG always seems to be premultiplied, webp isn't, etc.). I can't figure out a way to disable premultiplication or unpremultiply using sharp, so I was wondering if there was a way to handle premultiplied images within rgbaToThumbHash or process it myself before passing it to rgbaToThumbHash?