Next.js Sanity Image

By Lorenzo de Jong

Utility for using responsive images hosted on the Sanity.io CDN with the Next.js image component.

next-sanity-image

Utility for using images hosted on the Sanity.io CDN with the Next.js image component. This library:

  • Supports all layout options from the next/image component.
  • Implements the loader callback to resolve the corresponding Sanity CDN URL's.
  • Respects the image sizes and device sizes as specified in your Next config.
  • Respects the quality as specified in the next/image props.
  • Allows transforming the image using the @sanity/image-url builder.
  • Automatically sets the width and the height of the Next image component to the corresponding aspect ratio.
  • Supports Webp formats using automatic content negotation.
  • Supports blur-up placeholder images introduced in Next.js 11.0.0 out of the box (with optional image transformations)
  • Is fully typed and exposes relevant types.

Installation

npm install --save next-sanity-image

This library also expects you to pass in a SanityClient instance, if you haven't installed this already:

npm install --save @sanity/client

Finally configure your next.config.js to allow loading images from the Sanity.io CDN

module.exports = {
	images: {
		domains: ['cdn.sanity.io']
	}
};

Usage

All next/image component layouts are supported (https://nextjs.org/docs/api-reference/next/image#layout). Below you can find a usage example for each of the supported layouts.

Responsive layout

It's recommended to use the responsive layout for the best compatibility with different devices and resolutions. It's required to set the sizes attribute using this layout (https://developer.mozilla.org/en-US/docs/Web/HTML/Element/img#attr-sizes).

import sanityClient from '@sanity/client';
import Img from 'next/image';
import { useNextSanityImage } from 'next-sanity-image';

// If you're using a private dataset you probably have to configure a separate write/read client.
// https://www.sanity.io/help/js-client-usecdn-token
const configuredSanityClient = sanityClient({
	projectId: process.env.NEXT_PUBLIC_SANITY_PROJECT_ID,
	dataset: process.env.NEXT_PUBLIC_SANITY_DATASET,
	useCdn: true
});

const Page = ({ mySanityData }) => (
	const imageProps = useNextSanityImage(
		configuredSanityClient,
		mySanityData.image
	);

	return (
		<Img {...imageProps} layout="responsive" sizes="(max-width: 800px) 100vw, 800px" />
	);
);

// Replace this with your logic for fetching data from the Sanity API.
export const getServerSideProps = async function (context) {
	const { slug = '' } = context.query;

	const data = await configuredSanityClient.fetch(
		`{
			"mySanityData": *[_type == "mySanityType" && slug.current == $slug][0] {
				image
			}
		}`,
		{ slug }
	);

	return { props: data };
};

export default Page;

Intrinsic layout

// ... see "Responsive layout"

const Page = ({ mySanityData }) => (
	const imageProps = useNextSanityImage(
		configuredSanityClient,
		mySanityData.image
	);

	return (
		<Img {...imageProps} layout="intrinsic" />
	);
);

// ... see "Responsive layout"

Fixed layout

// ... see "Responsive layout"

const Page = ({ mySanityData }) => (
	const imageProps = useNextSanityImage(
		configuredSanityClient,
		mySanityData.image
	);

	return (
		<Img {...imageProps} layout="fixed" />
	);
);

// ... see "Responsive layout"

Fill layout

Omit the width and height props returned from useNextSanityImage when using a fill layout, as this fills the available space of the parent container. You probably also want to set the objectFit prop to specify how the object resizes inside the container.

// ... see "Responsive layout"

const Page = ({ mySanityData }) => (
	const imageProps = useNextSanityImage(
		configuredSanityClient,
		mySanityData.image
	);

	return (
		<Img src={imageProps.src} loader={imageProps.loader} layout="fill" objectFit="contain" />
	);
);

// ... see "Responsive layout"

Customizing the blur-up placeholder image

Blur-up placeholders are enabled by default as of Next.js 11.0.0. It's possible to customize the blur amount, quality and width of the placeholder image by modifying the options of useNextSanityImage. If you require more advanced image transformations, check out the chapter on Image transformations.

// ... see "Responsive layout"

const Page = ({ mySanityData }) => (
	const imageProps = useNextSanityImage(
		configuredSanityClient,
		mySanityData.image,
		{
			blurUpImageWidth: 124,
			blurUpImageQuality: 40,
			blurUpAmount: 24
		}
	);

	return (
		<Img {...imageProps} layout="responsive" sizes="(max-width: 800px) 100vw, 800px" />
	);
);

// ... see "Responsive layout"

API

useNextSanityImage

React hook which handles generating a URL for each of the defined sizes in the image sizes and device sizes Next.js options.

sanityClient: SanityClient

Pass in a configured instance of the SanityClient, used for building the URL using the @sanity/image-url builder.

image: SanityImageSource | null

A reference to a Sanity image asset, can be retrieved by using the Sanity API. You can pass in any asset that is also supported by the image() method of @sanity/image-url. This parameter can be set to null in order to not load any image.

options: UseNextSanityImageOptions

enableBlurUp: boolean

Enables the blur-up placeholder image. Defaults to true.

blurUpImageQuality: number | null

The quality of the blur-up placeholder image, ranging from 0 - 100. Defaults to 30.

blurUpImageWidth: number | null

The width of the blur-up placeholder image (in pixels). Defaults to 64.

blurUpAmount: number | null

The amount of blur applied to the blur-up placeholder image, ranging from 0 - 100. Defaults to 50.

imageBuilder?: function(/* see below */)

| property | type | description | | ---------------------------------- | ---------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------- | | imageUrlBuilder | ImageUrlBuilder | @sanity/image-url builder to apply image transformations. | | options | UseNextSanityImageBuilderOptions | Options object with relevant context passed to the callback, see properties below. | | options.width | number | null | The width for the current srcSet entry, if set to null this is the entry for the src fallback attribute. | | options.originalImageDimensions | { width: number, height: number, aspectRatio: number } : UseNextSanityImageDimensions | Object containing dimensions of the original image passed to the image parameter. | | options.quality | number | null | The quality of the image as passed to the quality prop of the next/image component. |

An optional function callback which allows you to customize the image using the ImageUrlBuilder. This function is called for every entry in the image sizes and device sizes, and is used to define the URL's outputted in the srcSet attribute of the image.

Defaults to:

(imageUrlBuilder, options) => {
	return imageUrlBuilder
		.width(options.width || Math.min(options.originalImageDimensions.width, 1920))
		.quality(options.quality || 75)
		.fit('clip');
}

For an example on how to use this, read the chapter on Image transformations.

blurUpImageBuilder?: function(/* see below */)

| property | type | description | | ---------------------------------- | ---------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------- | | imageUrlBuilder | ImageUrlBuilder | @sanity/image-url builder to apply image transformations. | | options | UseNextSanityImageBuilderOptions | Options object with relevant context passed to the callback, see properties below. | | options.width | number | null | The width for the current srcSet entry, if set to null this is the entry for the src fallback attribute. | | options.originalImageDimensions | { width: number, height: number, aspectRatio: number } : UseNextSanityImageDimensions | Object containing dimensions of the original image passed to the image parameter. | | options.quality | number | null | The quality of the image as passed to the quality prop of the next/image component. | | options.blurAmount | number | null | The amount of blur applied to the image (ranging from 0 - 100). |

An optional function callback which allows you to customize the blur-up placeholder image using the ImageUrlBuilder. This function is called for every entry in the image sizes and device sizes, and is used to define the URL outputted in the blurDataURL attribute of the image.

It's recommended to use the blurUpImageQuality, blurUpImageWidth and/or blurUpAmount options to modify the blur-up placeholder. Only use this image builder when you also want to apply other transformations to the blur-up placeholder image.

Please note that it's recommended to keep the width and quality of the blur-up placeholder low, as this placeholder image will be replaced directly after load!

Defaults to:

(imageUrlBuilder, options) => {
	return imageUrlBuilder
		.width(options.width || 64)
		.quality(options.quality || 30)
		.blur(options.blurAmount || 50)
		.fit('clip');
};

For more information on how to use this, read the chapter on Image transformations.

Return value: UseNextSanityImageProps | null

If the image parameter is set to null, the return value of this hook will also be null. This allows you to handle any conditional rendering when no image is loaded. If an image is set, to following result (UseNextSanityImageProps) will be returned:

{
	src: string,
	width: number,
	height: number,

	// Properties below change based on the specified 'enableBlurUp' option
	placeholder: 'blur' | 'empty',
	blurDataURL?: string,

	// https://nextjs.org/docs/api-reference/next/image#loader
	loader: ImageLoader
}

Image transformations

Custom transformations to the resulting image can be made by implementing the imageBuilder callback function. Note that it's recommended to implement a memoized callback, either by implementing the function outside of the component function scope or by making use of useCallback. Otherwise the props will be recomputed for every render.

The same can be done for the blur-up placeholder image by using the blurUpImageBuilder option.

//...

const myCustomImageBuilder = (imageUrlBuilder, options) => {
	return imageUrlBuilder
		.width(options.width || Math.min(options.originalImageDimensions.width, 800))
		.blur(20)
		.flipHorizontal()
		.saturation(-100)
		.fit('clip');
};

const Page = ({ mySanityData }) => (
	const imageProps = useNextSanityImage(
		configuredSanityClient,
		mySanityData.image,
		{ imageBuilder: myCustomImageBuilder }
	);

	return (
		<Img {...imageProps} layout="responsive" sizes="(max-width: 800px) 100vw, 800px" />
	);
);

//...

Gotchas

  • Because next/image only renders a single <img /> element with a srcSet attribute, the width and height prop being returned by the React hook is uniform for each size. Cropping an image is possible using the ImageUrlBuilder, however you have to return an image with the same aspect ratio for each of the defined sizes. Art direction is currently not supported (both by next/image and this library).

If the functionality mentioned above is desired, please file an issue stating your specific use case so we can look at the desired behavior and possibilities.

Types

The following types are exposed from the library:

  • ImageUrlBuilder
  • UseNextSanityImageProps
  • UseNextSanityImageOptions
  • UseNextSanityBlurUpImageBuilder
  • UseNextSanityBlurUpImageBuilderOptions
  • UseNextSanityImageBuilder
  • UseNextSanityImageBuilderOptions
  • UseNextSanityImageDimensions

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