Retroactively add Blurhash strings to image assets in your Sanity Content Lake.

blurhash.js

/**
 * Retroactively add Blurhash strings to image assets in your Sanity Content Lake.
 * 1. yarn add got sharp blurhash
 * 2. run sanity exec blurhash --with-user-token
 * 3. repeat (patches 100 assets in 1 transaction pr run)
 * 
 * Some images might take a while to process.
 */
import client from 'part:@sanity/base/client'
import got from 'got'
import sharp from 'sharp'
import { encode } from "blurhash";

const versionedClient = client.withConfig({ apiVersion: '2021-10-22' })
const BASE_COMPONENT = 5

const loadImage = async src => {
  try {
    const response = await got(src, { responseType: 'buffer' })
    const arr = new Uint8Array(response.body)
    return arr
  }
  catch (error) {
    console.log(error)
    return undefined
  }
}


const encodeImageToBlurhash = async ({ url, metadata }) => {
  const { dimensions } = metadata
  const dimensionedUrl = url
  const imageBuffer = await loadImage(dimensionedUrl);
  const { data, info } = await sharp(imageBuffer).raw().ensureAlpha().toBuffer({ resolveWithObject: true })
  const { height, width } = info

  let componentX = BASE_COMPONENT
  let componentY = BASE_COMPONENT

  if (width > height) {
    componentY = Math.ceil(BASE_COMPONENT * (height / width))
  } else {
    componentX = Math.ceil(BASE_COMPONENT * (width / height))
  }

  try {
    return encode(data, width, height, componentX, componentY);
  } catch (err) {
    console.error(err)
    return undefined
  }
};

async function run() {
  // Fetch assets without blurhash, 100 at a time
  const assets = await versionedClient
    .fetch(`*[_type == "sanity.imageAsset" && metadata.blurHash == null][0...100]`)
  if (!assets.length) {
    return 'No assets to blurhash'
  }
  const createTransaction = patches =>
    patches.reduce((tx, patch) => tx.patch(patch.id, patch.patch), versionedClient.transaction())

  // build transaction, one by one
  let patches = []
  for (const asset of assets) {
    const hash = await encodeImageToBlurhash(asset)
    console.log(`Created hash for ${asset._id}: ${hash}`)
    if (hash) {
      patches = [...patches, {
        id: asset._id,
        patch: {
          set: {
            'metadata.blurHash': hash
          }
        }
      }]
    }
  }
  console.log(`Creating ${patches.length} transactions…`)
  const transaction = createTransaction(patches)
  const result = await transaction.commit()
  return JSON.stringify(result, null, 2)
}

run().then(result => console.log(result))

thanks for this @kmelve, i got a linting error when running this because of a missing const in your
for (asset of assets) {...}
should be
for (const asset of assets) {...}

also i was running a script with sanity exec for the first time so i found this article useful.

After changing this it works like a charm! Thanks again for your great work!

Worth mentioning that got is now a pure ES6 package and will throw errors if you use got@latest. You probably want to do:

yarn add got@11.8.3 sharp blurhash