next.js/packages/next/src/shared/lib/image-loader.ts

import type { ImageLoaderPropsWithConfig } from './image-config'

const DEFAULT_Q = 75

function defaultLoader({
  config,
  src,
  width,
  quality,
}: ImageLoaderPropsWithConfig): string {
  if (process.env.NODE_ENV !== 'production') {
    const missingValues = []

    // these should always be provided but make sure they are
    if (!src) missingValues.push('src')
    if (!width) missingValues.push('width')

    if (missingValues.length > 0) {
      throw new Error(
        `Next Image Optimization requires ${missingValues.join(
          ', '
        )} to be provided. Make sure you pass them as props to the \`next/image\` component. Received: ${JSON.stringify(
          { src, width, quality }
        )}`
      )
    }

    if (src.startsWith('//')) {
      throw new Error(
        `Failed to parse src "${src}" on \`next/image\`, protocol-relative URL (//) must be changed to an absolute URL (http:// or https://)`
      )
    }

    if (src.startsWith('/') && config.localPatterns) {
      if (
        process.env.NODE_ENV !== 'test' &&
        // micromatch isn't compatible with edge runtime
        process.env.NEXT_RUNTIME !== 'edge'
      ) {
        // We use dynamic require because this should only error in development
        const { hasLocalMatch } =
          require('./match-local-pattern') as typeof import('./match-local-pattern')
        if (!hasLocalMatch(config.localPatterns, src)) {
          throw new Error(
            `Invalid src prop (${src}) on \`next/image\` does not match \`images.localPatterns\` configured in your \`next.config.js\`\n` +
              `See more info: https://nextjs.org/docs/messages/next-image-unconfigured-localpatterns`
          )
        }
      }
    }

    if (!src.startsWith('/') && (config.domains || config.remotePatterns)) {
      let parsedSrc: URL
      try {
        parsedSrc = new URL(src)
      } catch (err) {
        console.error(err)
        throw new Error(
          `Failed to parse src "${src}" on \`next/image\`, if using relative image it must start with a leading slash "/" or be an absolute URL (http:// or https://)`
        )
      }

      if (
        process.env.NODE_ENV !== 'test' &&
        // micromatch isn't compatible with edge runtime
        process.env.NEXT_RUNTIME !== 'edge'
      ) {
        // We use dynamic require because this should only error in development
        const { hasRemoteMatch } =
          require('./match-remote-pattern') as typeof import('./match-remote-pattern')
        if (
          !hasRemoteMatch(config.domains!, config.remotePatterns!, parsedSrc)
        ) {
          throw new Error(
            `Invalid src prop (${src}) on \`next/image\`, hostname "${parsedSrc.hostname}" is not configured under images in your \`next.config.js\`\n` +
              `See more info: https://nextjs.org/docs/messages/next-image-unconfigured-host`
          )
        }
      }
    }

    if (quality && config.qualities && !config.qualities.includes(quality)) {
      throw new Error(
        `Invalid quality prop (${quality}) on \`next/image\` does not match \`images.qualities\` configured in your \`next.config.js\`\n` +
          `See more info: https://nextjs.org/docs/messages/next-image-unconfigured-qualities`
      )
    }
  }

  const q =
    quality ||
    config.qualities?.reduce((prev, cur) =>
      Math.abs(cur - DEFAULT_Q) < Math.abs(prev - DEFAULT_Q) ? cur : prev
    ) ||
    DEFAULT_Q

  return `${config.path}?url=${encodeURIComponent(src)}&w=${width}&q=${q}${
    src.startsWith('/_next/static/media/') && process.env.NEXT_DEPLOYMENT_ID
      ? `&dpl=${process.env.NEXT_DEPLOYMENT_ID}`
      : ''
  }`
}

// We use this to determine if the import is the default loader
// or a custom loader defined by the user in next.config.js
defaultLoader.__next_img_default = true

export default defaultLoader