function getImageData(img: HTMLImageElement): ImageData | undefined {
  const canvas = document.createElement('canvas')
  canvas.width = img.width
  canvas.height = img.height
  const ctx = canvas.getContext('2d')

  if (ctx) {
    ctx.drawImage(img, 0, 0)
    return ctx.getImageData(0, 0, canvas.width, canvas.height)
  }
}

export default async function hashImage(img: HTMLImageElement): Promise<string> {
  const imageData = getImageData(img)

  if (imageData) {
    const digest = await crypto.subtle.digest('SHA-256', imageData.data)
    const hashArray = Array.from(new Uint8Array(digest))
    return hashArray.map((b) => ('00' + b.toString(16)).slice(-2)).join('')
  }

  return ''
}