Strapi 4 Blurhash

blurhash.js

// ./src/extensions/blurhash.js
const plaiceholder = require('plaiceholder')
const _ = require('lodash')

module.exports = {
  generatePlaceholder (strapi) {
    strapi.contentType('plugin::upload.file').attributes.placeholder = {
      type: 'text'
    }

    strapi.plugin('upload').services.upload.uploadFileAndPersist = async function (fileData, { user } = {}) {
      const config = strapi.config.get('plugin.upload')

      const {
        getDimensions,
        generateThumbnail,
        generateResponsiveFormats,
        isSupportedImage
      } = strapi.plugin('upload').service('image-manipulation')

      await strapi.plugin('upload').service('provider').upload(fileData)

      if (await isSupportedImage(fileData)) {
        const thumbnailFile = await generateThumbnail(fileData)

        if (thumbnailFile) {
          await strapi.plugin('upload').service('provider').upload(thumbnailFile)

          try {
            await plaiceholder
              .getPlaiceholder(thumbnailFile.url)
              .then(({ base64 }) => { fileData.placeholder = base64 })
          } catch (e) {
            fileData.placeholder = ''
          }

          delete thumbnailFile.buffer
          _.set(fileData, 'formats.thumbnail', thumbnailFile)
        }

        const formats = await generateResponsiveFormats(fileData)

        if (Array.isArray(formats) && formats.length > 0) {
          for (const format of formats) {
            if (!format) { continue }

            const { key, file } = format

            strapi.plugin('upload').service('provider').upload(file)

            _.set(fileData, ['formats', key], file)
          }
        }

        const { width, height } = await getDimensions(fileData)

        _.assign(fileData, {
          provider: config.provider,
          width,
          height
        })
      }

      return this.add(fileData, { user })
    }
  }
}

index.js

// ./src/index.js
const blurhash = require('./extensions/blurhash');

register({ strapi }) {
    blurhash.generatePlaceholder(strapi);
},

This Plugin was written for Strapi v4 anyways. So the code here should be all you need. However, I'm no longer using Strapi, but I'm sure, that there are alternatives to this here already.