gatsby-plugin-sanity-image-alt v0.1.12

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
• 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
• Adds in width and height elements to fix any Cumulative Layout Shift on the page load.

Getting Started

Install it

yarn add gatsby-plugin-sanity-image

Configure it

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

Know what y’er doin’? Here’s the copy pasta:

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

    // Additional params to include with every image.
    // This is optional and the default is shown
    // below—if you like what you see, don’t set it.
    defaultImageConfig: {
      quality: 75,
      fit: "max",
      auto: "format",
    },
  },
}

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! 🤯😇

Quering 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 the following:

<!--
  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;

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

This project is licensed under the Mozilla Public License 2.0, which is a copyleft license with a share-alike provision. Please contribute meaningful improvements back to the open-source community, either via direct contribution or by releasing a separate library!