rsnext/packages/next/build/webpack/loaders/next-image-loader.js

import loaderUtils from 'next/dist/compiled/loader-utils'
import { resizeImage, getImageSize } from '../../../server/image-optimizer'

const BLUR_IMG_SIZE = 8
const BLUR_QUALITY = 70
const VALID_BLUR_EXT = ['jpeg', 'png', 'webp', 'avif'] // should match next/client/image.tsx

function nextImageLoader(content) {
  const imageLoaderSpan = this.currentTraceSpan.traceChild('next-image-loader')
  return imageLoaderSpan.traceAsyncFn(async () => {
    const { isServer, isDev, assetPrefix, basePath } =
      loaderUtils.getOptions(this)
    const context = this.rootContext
    const opts = { context, content }
    const interpolatedName = loaderUtils.interpolateName(
      this,
      '/static/media/[name].[hash:8].[ext]',
      opts
    )
    const outputPath = assetPrefix + '/_next' + interpolatedName

    let extension = loaderUtils.interpolateName(this, '[ext]', opts)
    if (extension === 'jpg') {
      extension = 'jpeg'
    }

    const imageSizeSpan = imageLoaderSpan.traceChild('image-size-calculation')
    const imageSize = await imageSizeSpan.traceAsyncFn(() =>
      getImageSize(content, extension)
    )
    let blurDataURL

    if (VALID_BLUR_EXT.includes(extension)) {
      if (isDev) {
        const prefix = 'http://localhost'
        const url = new URL(`${basePath || ''}/_next/image`, prefix)
        url.searchParams.set('url', outputPath)
        url.searchParams.set('w', BLUR_IMG_SIZE)
        url.searchParams.set('q', BLUR_QUALITY)
        blurDataURL = url.href.slice(prefix.length)
      } else {
        // Shrink the image's largest dimension
        const dimension =
          imageSize.width >= imageSize.height ? 'width' : 'height'

        const resizeImageSpan = imageLoaderSpan.traceChild('image-resize')
        const resizedImage = await resizeImageSpan.traceAsyncFn(() =>
          resizeImage(
            content,
            dimension,
            BLUR_IMG_SIZE,
            extension,
            BLUR_QUALITY
          )
        )
        const blurDataURLSpan = imageLoaderSpan.traceChild(
          'image-base64-tostring'
        )
        blurDataURL = blurDataURLSpan.traceFn(
          () =>
            `data:image/${extension};base64,${resizedImage.toString('base64')}`
        )
      }
    }

    const stringifiedData = imageLoaderSpan
      .traceChild('image-data-stringify')
      .traceFn(() =>
        JSON.stringify({
          src: outputPath,
          height: imageSize.height,
          width: imageSize.width,
          blurDataURL,
        })
      )

    if (!isServer) {
      this.emitFile(interpolatedName, content, null)
    }

    return `export default ${stringifiedData};`
  })
}
export const raw = true
export default nextImageLoader