@unpic/react

ascorbic/unpic-img

A high-performance, responsive image components for React and Next.js.

Installation and usage

npm install @unpic/react
import { Image } from "@unpic/react";

function MyComponent() {
  return (
    <Image
      src="https://cdn.shopify.com/static/sample-images/bath_grande_crop_center.jpeg"
      layout="constrained"
      width={800}
      height={600}
      alt="A lovely bath"
    />
  );
}

Unpic for Next.js

If you are using Next.js, you can use the @unpic/react/next component. This works the same as the main @unpic/react component, but also supports the Next.js Image Optimizer for images that don’t use a supported CDN. This includes local images, either using a path or an import.

Usage

The component is part of the @unpic/react package, so you install it in the same way:

npm install @unpic/react

Then, in your Next.js project, import the component from @unpic/react/next:

import { Image } from "@unpic/react/next";
import logo from "../public/logo.png";

// You can use both local images, and ones from image CDNs
<>
  <Image src={logo} alt="Logo" layout="constrained" />;
  <Image
    src="https://cdn.shopify.com/static/sample-images/garnished.jpeg"
    layout="constrained"
    width={800}
    height={600}
    alt="Shopify product"
  />
</>;

Differences from next/image

The @unpic/react/next component is similar in concept to next/image, and can use the same image optimizer. However, it has a number of differences that may mean you prefer to use it instead.

When unpic-img detects that you are using a supported CDN it will load the images from there directly, using the CDN’s own image resizing rather than Next.js. This saves the need to process the image twice, and means that you can use the more powerful features of the image CDN.

Unlike next/image, unpic-img will not distort the image to fit the requested size as it uses object-fit: cover by default, and if using a supported CDN it will crop the image to the requested aspect ratio.

There is no need to specify a loader, because unpic-img will automatically detect the CDN and use the correct loader, and supports many more than Next.js.

unpic-img includes three built-in layout modes: fixed, constrained, and fullWidth. These affect how the image resizes, but also allows smarter generation of the srcset and sizes attributes. See below for an example:

image-layouts

Props

The component accepts all the props of an <img> tag, plus the following:

layout

The resizing behaviour of the image.

  • constrained: (default) the image will be rendered at a maximum of width and height, but will scale down automatically if the container is smaller, maintaining the aspect ratio.
  • fullWidth: the image will be rendered at full width of its container. This is optimized for full-width hero images. You can set height to a fixed value, which will mean the image will be rendered at that fixed height and scale horizontally to fill the container.
  • fixed: the image will be rendered at the exact size specified by width and height

priority

By default, images are loaded lazily. If priority is set to true, the image will be loaded eagerly, and will be given high priority by the browser. This is useful for images that are above the fold, particularly large ones such as hero images.

background

Either an image URL, CSS gradient or CSS colour value. If set to auto, a low-resolution version of the image will be rendered as a background image, with a blurred placeholder effect. This is still loaded from the remote server, so if you can instead provide an inline base64-encoded version of the image or background colour, you should do that instead. Look at @unpic/placeholder for a library that can generate these placeholders.

Bear in mind that this is not removed after the image loads, so it will be visible if the image has transparency.

aspectRatio

Instead of specifying both width and height, you can specify can aspectRatio.

cdn

By default the CDN is auto-detected from the src URL. If you want to override this, you can specify a CDN object. See the unpic for supported values.

breakpoints

By default the image breakpoints used in the srcset are generated based on the layout and image size. You can override this by specifying an array of breakpoints. The breakpoints are specified as an array of numbers, representing the width of the image in pixels.

Other props

Any prop supported by <img> tags can be passed in, except srcset which is generated from src. The following props are set automatically, but can be overridden if you need to:

  • sizes
  • role
  • decoding
  • loading
  • fetchpriority