Images

Images#

Volto comes with an Image component that loads images in an optimal way.

Features of the Image component are the following.

  • optimized lazy loading

  • automatic srcset generation, if given a content item or catalog brain

  • optional responsive width

The component can accept all the regular HTML <img> attributes and a few extra for the above features. The following example demonstrates how the code with attributes will render to HTML.

import config from '@plone/volto/registry';

const Image = config.getComponent({ name: 'Image' }).component;

<Image
  src="https://picsum.photos/200/300"
  alt="Alt text for accessibility"
  className="myClass"
  width="200"
  height="300"
/>;

<img
  src="https://picsum.photos/200/300"
  alt="Alt text for accessibility"
  class="myClass"
  width="200"
  height="300"
/>

Setting the loading="lazy" attribute to the Image component also adds the decoding="async" attribute. The async attribute decodes the image asynchronously to reduce delay in presenting other content.

To render an image from a content object, you can use the component as shown in the following code snippet.

<Image item={content} imageField="image" alt="Alt text for accessibility" />

This will generate the src, srcset, width, and height attributes automatically for the given image.

To make the image width responsive, you can add the prop responsive, and the literal responsive will be added to the HTML attribute class.

Serving the right image size#

To serve the proper image size for the viewer's device, you should add a sizes attribute to the Image component while rendering. This responsibility is left to the developer because it depends on where the image is rendered.

For example, if the image is rendered in a container that is always half as wide as the page, the sizes attribute should reflect that to properly inform the browser which image size to request and render.

<Image
  item={content}
  imageField="image"
  alt="Alt text for accessibility"
  sizes="50vw"
/>

If the image is rendered at full viewport width when the viewport is less than 900px wide, though, you can add a media condition to the sizes attribute.

<Image
  item={content}
  imageField="image"
  alt="Alt text for accessibility"
  sizes="(max-width: 900px) 100vw, 50vw"
/>

More information on this subject can be found at the following resources.

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