Keep the aspect ratio of your images using GIFs

create-gif.js

function createGif(width, height) {
  const b64wh = btoa(
    String.fromCharCode(width & 0xFF) +
    String.fromCharCode(width >> 8 & 0xFF) +
    String.fromCharCode(height & 0xFF) +
    String.fromCharCode(height >> 8 & 0xFF) +
    String.fromCharCode(0) +
    String.fromCharCode(0)
  )
  return `R0lGODlh${b64wh}ACwAAAAAAQABAAAC`
}