sanity-image

A well-considered React component for displaying images from Sanity. At a glance:

• Outputs a single <img> tag, no nested DOM structure to mess with
• Zero styling included so you can style it however you want…it's just an img tag!
• 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
• Dynamic srcSet factor based on image output width
• Knows exactly what size the image will be and sets width and height attributes accordingly
• Supports crop and hotspot values from the Sanity Studio
• Automatically crops to the most “interesting” part of the image if the aspect ratio changes and no hotspot is provided
• Images are never scaled up
• Tiny 4kb bundle size (2kb gzipped)
• No dependencies
• TypeScript support
• Works with Gatsby, Next.js, and any other React-based framework
• Polymorphic component (supports as prop to render as a custom component)

Quick Start

Install it:

yarn add sanity-image
# or
npm install sanity-image

Use it:

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 a quick example of most of what you’ll need to know:

Simplest Case:

This will render the image out assuming it will be displayed at half its original width with a srcSet included (multiplies vary based on original image size):

import { SanityImage } from "sanity-image"

const YourSweetComponent = ({ image }: ComponentProps) => (
  <SanityImage
    // Pass the Sanity Image ID (`_id`) (e.g., `image-abcde12345-1200x800-jpg`)
    id={image._id}
    baseUrl="https://cdn.sanity.io/images/abcd1234/production/"
    alt="Demo image"
  />
)

More full-featured example:

import { SanityImage } from "sanity-image"

const YourSweetComponent = ({ image }: ComponentProps) => (
  <SanityImage
    // Pass the Sanity Image ID (`_id`) (e.g., `image-abcde12345-1200x800-jpg`)
    id={image._id}
    //
    // You can set the base URL manually, or let it be constructed by passing
    // `projectId` and `dataset` props.
    baseUrl="https://cdn.sanity.io/images/abcd1234/production/"
    //
    // Specify how big it is expected to render so a reasonable srcSet can be
    // generated using `width`, `height`, or both
    width={500}
    height={250}
    //
    // Choose whether you want it to act like `object-fit: cover` or
    // `object-fit: contain`, or leave it out to use the default (contain)
    mode="cover"
    //
    // Have hotspot or crop data from Sanity? Pass it in!
    hotspot={image.hotspot}
    crop={image.crop}
    //
    // Want low-quality image previews? Fetch them from Sanity and pass them in too.
    preview={image.asset.metadata.lqip}
    //
    // Have a burning desire to have Sanity change the format or something?
    // Most of the visual effects from the Sanity Image API are available:
    queryParams={{ sharpen: 30, q: 80 }}
    //
    // Anything else you want to pass through to the img tag? Go for it!
    alt="Sweet Christmas!"
    className="big-ol-image"
    sizes="(min-width: 500px) 500px, 100vw"
  />
)

export default YourSweetComponent

That’s the gist. Read on for more. 👇

Details

How it works at a glance:

• The image ID is parsed to determine the source image dimensions and format
• SVG images get special treatment from the Sanity Image API (they don't support params), so they're handled a bit differently (check SanityImage.ts for details)
• All other images have src and srcSet props generated based on the width and height props you pass in (or the image dimensions if you don't pass in a width or height)
• The srcSet widths depend on the size of the output image and the original image; there's some logic to avoid wasteful tiny images or giant jumps in size between large entries (see dynamicMultipliers in urlBuilder.ts)
• Values in the srcSet are never duplicated and never upscale the image
• Since we can compute the output dimensions of the image in all cases, the width and height attributes are set automatically to avoid layout shifts
• A few image params are applied by default:
  • auto=format - Sanity will use WebP images if they're supported by the browser (note: if you specify fm manually, this won't be set)
  • fit - if the image aspect ratio isn't changed, this will be set to max; if the aspect ratio will change it's set to crop; you don't really need to worry about this though
  • q - the quality is set to 75 by default, but you can override it with the queryParams prop
• The loading attribute will be set to lazy if it isn't supplied; use loading="eager" for images above the fold
• The alt attribute will be set to an empty string if it isn't supplied; set it if it isn't a decorative image!
• By default it renders an img tag (two if you pass in a preview), but you can pass in a custom component to render as using the as prop (see the SanityImage.test.tsx file for an example of this)
• If you wanna get weird you can also import the buildSrc and buildSrcSet exports to do your own thing with. You get a lot of the magic still this way with a skosh more control.
• Similarly, the parseImageId function is available as a named export; it takes an image ID and returns an object with the image id, dimensions, and format.
• Query params passed to Sanity are all sorted and minimized like heck for improved caching and smaller URLs. Pass in a height only? Don't be alarmed, but it'll be converted to a w param without altering what you're asking Sanity for. Ask for mode="cover" but the aspect ratio matches the source? It'll be ignored and fall back to fit=max with just a w param. You get the idea (I hope, or at least, I'm pretending, but no judgement if you don't, it's definitely 11:09pm and I'm on fumes)

Props

This is mostly copied and reformatted from the types.ts file; if you're comfortable with TypeScript, that might give you more detail.

• id (string) — Required - The Sanity Image ID (_id or _ref field value)
• mode ("cover" | "contain") — Optional - Use cover to crop the image to match the requested aspect ratio (based on width and height). Use contain to fit the image to the boundaries provided without altering the aspect ratio. Defaults to "contain".
• width (number) — Optional - The target width of the image in pixels. Only used for determining the dimensions of the generated assets, not for layout. Use CSS to specify how the browser should render the image instead.
• height (number) — Optional - The target height of the image in pixels. Only used for determining the dimensions of the generated assets, not for layout. Use CSS to specify how the browser should render the image instead.
• hotspot ({ x: number, y: number }) — Optional - The hotspot coordinates to use for the image. Note: hotspot width and height are not used.
• crop ({ top: number, bottom: number, left: number, right: number }) — Optional - The crop coordinates to use for the image.
• preview (string) — Optional - A low-quality image preview to use while the full-size image is loading. This should be a base64-encoded image string.
• as (React.ElementType) — Optional - The component to render as. Defaults to "img".
• baseUrl (string) — Optional - The base URL to use for the image. If not specified, the projectId and dataset props will be used to construct the URL.
• projectId (string) — Optional - The Sanity project ID to use for the image. Only used if baseUrl is not specified.
• dataset (string) — Optional - The Sanity dataset to use for the image. Only used if baseUrl is not specified.
• queryParams (object) — Optional - An object of query parameters to pass to the Sanity Image API. See the Sanity Image API documentation for a list of available options.

That's the gist. There's a ton more in the inline comments and types and such, and I'll add more details as I think of them. Feel free to open an issue or start a discussion if you have questions or suggestions, or find me on the Sanity Slack!

⚠️ 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;

Tips

Wrap it internally

I recommend creating a wrapper component internally to pass your baseUrl prop and pass through any props. This keeps the configuration in one place and gives you an entry point to add any other logic you might need. Here's a TypeScript example (for JavaScript, just remove the type annotation after props):

import { SanityImage } from "sanity-image"

const projectId = process.env.SANITY_PROJECT_ID
const dataset = process.env.SANITY_DATASET
const baseUrl = `https://cdn.sanity.io/images/${projectId}/${dataset}/`

export const Image = (
  props: Omit<
    React.ComponentProps<typeof SanityImage>,
    "baseUrl" | "dataset" | "projectId"
  >
) => <SanityImage baseUrl={baseUrl} {...props} />

Styling your images

I recommend setting something like the following CSS for images in your project, then overriding styles as needed. This will ensure images act like block-level elements with infinitely scalable contents even with the width and height attributes set. It also makes it easier to handle responsiveness—if your container gets smaller, the image gets smaller.

img {
  display: block;
  max-width: 100%;
  width: 100%;
  height: auto;
}

Here's an example of how that works when using, for example, a 3-column grid that fills the viewport until it is a maximum of 1,200px wide (plus padding). This produces columns that are 390px at most on desktop:

<div
  css={{
    display: "grid",
    gridTemplateColumns: "repeat(3, 1fr)",
    gap: 15,
    maxWidth: 1240,
    paddingInline: 20,
    marginInline: "auto",
  }}
>
  {["image-a", "image-b", "image-c"].map((imageId) => (
    <div key={imageId}>
      <SanityImage
        id={imageId}
        baseUrl="..."
        width={390}
        sizes="(min-width: 1240px) 390px, calc((100vw - 40px - 30px) / 3)"
      />
    </div>
  ))}
</div>

If you need these images to all match in height, it's a good idea to switch to cover mode. With the height set to 260px and mode="cover", this will produce images with a 3:2 aspect ratio that fill the column width even if the source image is too small:

<SanityImage
  id={imageId}
  baseUrl="..."
  width={390}
  height={260}
  mode="cover"
  sizes="(min-width: 1240px) 390px, calc((100vw - 40px - 30px) / 3)"
/>

In this example we don't pass a hotspot value, so the image will be cropped based on what Sanity thinks is the most interesting part of the image since SanityImage automatically sets crop=entropy in these cases. If you want to override that, you can pass a hotspot value.

Background images

Using SanityImage for background images is easy, you just style the image to match the expectations of your mockup. In most cases that means setting position: relative on the container you want to fill, then using absolute positioning for the image. Here’s an example:

<section
  css={{
    position: "relative",
    paddingBlock: 100,
  }}
>
  <SanityImage
    id="..."
    baseUrl="..."
    width={1440}
    css={{
      position: "absolute",
      top: 0,
      left: 0,
      width: "100%",
      height: "100%",
      objectFit: "cover",
      userSelect: "none",
      zIndex: 1,
    }}
    alt=""
  />

  <div css={{ position: "relative", zIndex: 2 }}>
    <h1>Your big hero copy</h1>
    <LinkButton to="/signup/">Get started</LinkButton>
  </div>
</section>

This will cause the section to be sized based on the content inside of the div, and the image will be sized to fill the entire section. The aspect ratio of the image will be maintained due to the use of object-fit: cover. Note that we are still using mode="contain" for SanityImage here. If you have a rough idea of the height your section, you can set height and mode="cover" which will prevent, for example, a portrait orientation image from being retrieved and cropped by the browser.

Since the z-index is set higher on the div containing the content, it will show above the image. This example also sets user-select: none on the image to prevent the image from being selected when the user clicks and drags on the page to make it behave more like a traditional background image.

Fetching data from Sanity via GROQ

If you're using Sanity's GROQ query language to fetch data, here is how I recommend fetching the fields you need from a typical image with the hotspot, crop, and low-quality image preview included:

"id": asset._ref,
"preview": asset->metadata.lqip,
hotspot { x, y },
crop {
  bottom,
  left,
  right,
  top,
}

License

Copyright ©2023 Corey Ward. Available under the MIT License.