generateImageMetadata

You can use generateImageMetadata to generate different versions of one image or return multiple images for one route segment. This is useful for when you want to avoid hard-coding metadata values, such as for icons.

Parameters

generateImageMetadata function accepts the following parameters:

`params` (optional)

An object containing the dynamic route parameters object from the root segment down to the segment generateImageMetadata is called from.

export function generateImageMetadata({
  params,
}: {
  params: { slug: string }
}) {
  // ...
}

Route	URL	`params`
`app/shop/icon.js`	`/shop`	`undefined`
`app/shop/[slug]/icon.js`	`/shop/1`	`{ slug: '1' }`
`app/shop/[tag]/[item]/icon.js`	`/shop/1/2`	`{ tag: '1', item: '2' }`

Returns

The generateImageMetadata function should return an array of objects containing the image's metadata such as alt and size. In addition, each item must include an id value which will be passed to the props of the image generating function.

Image Metadata Object	Type
`id`	`string` (required)
`alt`	`string`
`size`	`{ width: number; height: number }`
`contentType`	`string`

import { ImageResponse } from 'next/og'
 
export function generateImageMetadata() {
  return [
    {
      contentType: 'image/png',
      size: { width: 48, height: 48 },
      id: 'small',
    },
    {
      contentType: 'image/png',
      size: { width: 72, height: 72 },
      id: 'medium',
    },
  ]
}
 
export default function Icon({ id }: { id: string }) {
  return new ImageResponse(
    (
      <div
        style={{
          width: '100%',
          height: '100%',
          display: 'flex',
          alignItems: 'center',
          justifyContent: 'center',
          fontSize: 88,
          background: '#000',
          color: '#fafafa',
        }}
      >
        Icon {id}
      </div>
    )
  )
}

Examples

Using external data

This example uses the params object and external data to generate multiple Open Graph images for a route segment.

import { ImageResponse } from 'next/og'
import { getCaptionForImage, getOGImages } from '@/app/utils/images'
 
export async function generateImageMetadata({
  params,
}: {
  params: { id: string }
}) {
  const images = await getOGImages(params.id)
 
  return images.map((image, idx) => ({
    id: idx,
    size: { width: 1200, height: 600 },
    alt: image.text,
    contentType: 'image/png',
  }))
}
 
export default async function Image({
  params,
  id,
}: {
  params: { id: string }
  id: number
}) {
  const productId = (await params).id
  const imageId = id
  const text = await getCaptionForImage(productId, imageId)
 
  return new ImageResponse(
    (
      <div
        style={
          {
            // ...
          }
        }
      >
        {text}
      </div>
    )
  )
}