gatsby-plugin-sanity-image

gatsby-plugin-sanity-image

The well-considered marriage between Sanity’s image assets and Gatsby you’ve been looking for.

• Outputs a single <img> tag, no nested DOM structure to mess with
• Supports low-quality image previews out of the box, without build-time penalties (native lazy loading)
• Generates a srcSet automatically based on the width you specify in your component code (meaning you can change it on the fly!)
• Applies Sanity hotspot data as the object-position in case you need it
• Computes cropped dimensions and drops srcSet entries that are larger than the source dimensions when appropriate (follows Sanity’s image-url parameters)
• Configure image quality, resizing behavior, file format, and more with Sanity’s Image API

At a Glance

You can find the full writeup on getting going below, but in the interest of making it easy to see if this is the thing you are looking for, here’s what using it looks like:

import Image from "gatsby-plugin-sanity-image"

const YourSweetComponent = ({ image }) => (
  <Image
    // pass asset, hotspot, and crop fields
    {...image}
    // tell Sanity how large to make the image (does not set any CSS)
    width={500}
    // style it how you want it
    style={{
      width: "100%",
      height: "100%",
      objectFit: "cover",
    }}
  />
)

export default YourSweetComponent

export const query = graphql`
  {
    sanityDocumentOfSomeKind {
      sweetImage {
        ...ImageWithPreview
      }
    }
  }
`

That’s the gist, folks. Read on for the full scoop!

Getting Started

Install it

yarn add gatsby-plugin-sanity-image

Configure it

ℹ️ Note: If this is your first time adding a Gatsby plugin, be sure to read this guide first—the below is a shorthand notation.

Simple configuration:

{
  resolve: "gatsby-plugin-sanity-image",
  options: {
    // Sanity project info (required)
    projectId: "abcd1234",
    dataset: "production",
  },
}

If you have custom image types in Sanity (e.g. mainImage that is of type image) you’ll need to add one more option before you move on. Check the full example or the Configuration Directives below.

Expand the full configuration example

// Full configuration:
{
  resolve: "gatsby-plugin-sanity-image",
  options: {
    // Sanity project info (required)
    projectId: "abcd1234",
    dataset: "production",

    // Custom image types are also supported. For example, if you have a
    // `mainImage` type in Sanity, it winds up in Gatsby as `SanityMainImage`,
    // and so you would add "SanityMainImage" to the customImageTypes array.
    customImageTypes: [],

    // This config directive allows you to specify the field that should be
    // retrieved and used as alt text when no `alt` prop is passed to the image
    // component. See docs for more detail.
    altFieldName: "alt",

    // SanityImage will warn you if you do not set an alt prop/attribute. If
    // you don't want this behavior, you can disable this here. By default this
    // is only enabled in development.
    warnOnMissingAlt: process.env.NODE_ENV === "development",

    // When no `alt` prop is available, SanityImage can default to setting an
    // empty string value. This can prevent accessibility audits from detecting
    // images that should have an alt value, but enabling it allows you to only
    // set alt text when it is needed.
    emptyAltFallback: false,

    // Additional params to pass to @sanity/image-url for every image. The
    // default is shown here, so you can omit the directive if you are happy
    // with what you see here.
    defaultImageConfig: {
      quality: 75,
      fit: "max",
      auto: "format",
    },

    // ########################################################################
    // Configuration directives below this point are rarely needed. If you    #
    // aren't confident you need them, you probably do not need them.         #
    // ########################################################################

    // If you prefer a different fragment name, such as `MagicImage`, enter it
    // here. This needs to be unique amongst your GraphQL types. `WithPreview`
    // will be appended for the second fragment (e.g. MagicImageWithPreview).
    fragmentName: "Image",

    // By default, image fields are typed as SanityImage, but there are cases
    // where you might want to use a custom schema or where custom image types
    // are not under the SanityImage type. In this case, you
    // can alter the type that the fragment is defined
    // on here without redefining the fragments.
    fragmentTypeName: "SanityImage",

    // If you prefer to retreive data another way or if you want to define the
    // fragment you use separately, you can opt-out of having fragments included
    // entirely.
    includeFragments: true,
  },
}

Don’t forget to restart gatsby develop after you update your gatsby-config.js!

Usage

1. Query for the image fields
2. Pass the retrieved fields as props to the SanityImage component
3. Use it like normal—it's just an img tag! 🤯😇

Querying for image data via GraphQL

This plugin includes two GraphQL fragments that will fetch the fields needed for display from any Sanity image asset. You do not have to use them, but they are convenient and help keep you away from confusing bugs.

In most cases, you'll want to use the ImageWithPreview fragment:

export const query = graphql`
  {
    sanitySomeDocument {
      yourImageField {
        ...ImageWithPreview
      }
    }
  }
`

This will retrieve the asset, hotspot, and crop fields and includes a low-quality image preview that will be shown while the full image is loading.

Opting out of blurry preview images

If you have an image that you do NOT want to use the preview image for, you can opt to use the simpler Image fragment instead. This has all of the same fields with the exception of the preview. This will keep your HTML files a bit lighter, but you may wind up with more cumulative layout shift as the browser fetches the image dimensions and evaluates your styles.

Note: If you are using an SVG image, you probably do not want to fetch the preview since it’ll get thrown away—the SanityImage component aborts early on SVG images to avoid generating meaningless srcSet data that reduces cache efficiency.

Using the SanityImage component

The data you fetched from GraphQL should be an object that you can expand straight into the SanityImage component and just work. If you used the ImageWithPreview fragment, SanityImage will do the right thing automatically.

import SanityImage from "gatsby-plugin-sanity-image"

const YourComponent = ({ yourImageFieldData }) =>
  <SanityImage {...yourImageFieldData} width={300} alt="Sweet Christmas!">

This renders an image tag like this:

<!--
  Using {baseUrl} below to refer to a string with this format:
  https://cdn.sanity.io/images/{projectId}/{dataset}/{imageId}?w=300&amp;h=600&amp;q=75&amp;fit=max&amp;auto=format
-->
<img
  src="{baseUrl}"
  srcset="
    {baseUrl}&amp;dpr=0.5  150w,
    {baseUrl}&amp;dpr=0.75 225w,
    {baseUrl}&amp;dpr=1    300w,
    {baseUrl}&amp;dpr=1.5  450w,
    {baseUrl}&amp;dpr=2    600w
  "
  loading="lazy"
  alt="Sweet Christmas!"
  class="css-1jku2jm-SanityImage"
/>

Note that SanityImage is not doing anything to style your image based on the width or height you provide (aside from setting a class with object-position set, should you choose to use it). In practice, it's rare that these values align consistently with a particular layout, and library control of this makes it difficult to predict the output given a particular input.

Instead you can style the resulting img tag just like any other element. SanityImage will pass through className and style props, and it makes no assumptions about your image presentation.

⚠️ Minor gotchas with deferred loading

SanityImage is relying on browser-native deferred image loading. This generally works fine in browsers that support it, but there are situations where the unloaded image is hidden or covered, resulting in the full image never loading.

If this happens, you can override the styles set on the full-size image using the img[data-loading] selector. This image sits immediately adjacent to the spaceball image and has the following default styles while loading:

position: absolute;
width: 10px !important; /* must be > 4px to be lazy loaded */
height: 10px !important; /* must be > 4px to be lazy loaded */
opacity: 0;
zindex: -10;
pointerevents: none;
userselect: none;

Component Props

For convenience, __typename, _type, and _key props will be ignored. Other props will be passed through to the final img element (e.g. native HTML attributes).

_{*️⃣ = Required}

Prop	Type	Description
asset *️⃣	Object	The asset object fetched from GraphQL. Should have an _id property on it, and possibly metadata (if you're using low-quality image previews).
crop	Object	The crop values fetched from GraphQL (top, right, bottom, and left)
hotspot	Object	The hotspot values fetched from GraphQL (width, height, x, and y)
width *️⃣	Number	This will be used as a target value to generate a srcSet of images both smaller and larger.
height	Number	Used to further constrain the image. Note: due to a bug in the @sanity/image-url library, setting this will cause fit modes to be largely ignored.
config	Object	Parameters for @sanity/image-url. Full list here.
options	Object	See below.

Options

__experimentalAspectRatio (Boolean)

If enabled, SanityImage will attempt to compute the final aspect ratio and use it to set width and height attributes on both the low-quality preview image as well as the final image. This does not currently take into account any config options, including fit modes or transforming options like rect or orientation.

Configuration Directives

_{*️⃣ = Required}

Option	Type	Default	Description
projectId *️⃣	String		Sanity Project ID
dataset *️⃣	String		Sanity Dataset ID
customImageTypes	Array	[]	If you would like to use the Image and ImageWithPreview fragments on custom image types, specify all custom type names in the customImageTypes array. For more detail, follow this guide.
altFieldName	String	null	If you are adding alt text directly to image assets in your Sanity Studio (e.g. via a plugin like sanity-plugin-media), this plugin can include that field in the Image and ImageWithPreview fragments and utilize it as the default/fallback alt attribute value when no alt prop is passed to the SanityImage component.
warnOnMissingAlt	Boolean	See note 👉	SanityImage will warn you if you do not set an alt prop/attribute. If you don't want this behavior, you can disable this here. By default this is only enabled in development.
emptyAltFallback	Boolean	false	When no alt prop is available, SanityImage can default to setting an empty string value. This can prevent accessibility audits from detecting images that should have an alt value, but enabling it allows you to only set alt text when it is needed.
defaultImageConfig	Object	See below.	Additional params to pass to the Sanity image URL builder. These will be converted into function calls against @sanity/image-url. Here is the full list of methods available.
Less common directives ⬇️			It is unlikely you will need to use these. Proceed with caution.
fragmentName	String	"Image"	If you prefer a different fragment name, such as MagicImage, enter it here. This needs to be unique amongst your GraphQL types. WithPreview will be appended for the second fragment (e.g. MagicImageWithPreview).
fragmentTypeName	String	"SanityImage"	By default, image fields are typed as SanityImage, but there are cases where you might want to use a custom schema or where custom image types are not under the SanityImage type. In this case, you can alter the type that the fragment is defined on without redefining the fragments.
includeFragments	Boolean	true	If you prefer to retreive data another way or if you want to define the fragment you use separately, you can opt-out of having fragments included entirely.

The default value for defaultImageConfig is as follows:

{
  quality: 75,   // use reasonable lossy compression level
  fit: "max",    // like `object-fit: contain`, but never scaling up
  auto: "format" // automatically select next-gen image formats on supporting browsers
}

More things to know

• If you don't specify width the uploaded image width is used.
• You are encouraged to use the sizes attribute to steer browsers to select the most appropriate image from the srcSet based on the viewport width
• You can target the low-quality image preview element via img[data-lqip] should you want to style it differently

License

Copyright ©2022 Corey Ward. Available under the MIT License.