React Progressive Graceful Image

Note: I published this interesting article on medium to explain the idea and motivation behind building this npm package. And a small code snippet to make best use of it.

Update

• [0.7.0] : Allow ^v18 of react and react-dom as peer dependencies, add + fix props types.
• [0.6.14] : Allow ^v17 of react and react-dom as peer dependencies.
• [0.6.13] : onError bug-fix to works as expected.

---

Note: This is a forked repo from https://github.com/FormidableLabs/react-progressive-image. So, all usage are similar to that.

I am adding two new features:

• Graceful loading
• Lazy loading

similar to https://github.com/linasmnew/react-graceful-image, but with a different approach(for better performance and optimization). So, please check usage of 4 newly introduced props (noRetry, noLazyLoad, rootMargin, threshold) from the props table below.

[TODO] :

• Use of Intersection Observer for Lazy Loading (Better Performance)
• Use of navigator.onLine in place of current retry strategy (Optimization)
• Introduce rootMargin and threshold props for Intersection Observer options.
• Add more Code Sandbox example links
• Remove ref from child function.
• Remove dependency of @researchgate/react-intersection-observer

Note: npm i intersection-observer, if polyfill is required, I have removed it to keep the library lightweight.

---

react-progressive-graceful-image React component for progressive image loading

Install

$ npm i react-progressive-graceful-image

Examples

Simple - CodeSandbox

<ProgressiveImage src="large-image.jpg" placeholder="tiny-image.jpg">
  {(src) => <img src={src} alt="an image" />}
</ProgressiveImage>

With Delay - CodeSandbox

<ProgressiveImage
  delay={3000}
  src="large-image.jpg"
  placeholder="tiny-image.jpg"
>
  {(src) => <img src={src} alt="an image" />}
</ProgressiveImage>

With loading argument - CodeSandbox

<ProgressiveImage src="large-image.jpg" placeholder="tiny-image.jpg">
  {(src, loading) => (
    <img style={{ opacity: loading ? 0.5 : 1 }} src={src} alt="an image" />
  )}
</ProgressiveImage>

With srcSet - CodeSandbox

<ProgressiveImage
  src="medium.jpg"
  srcSetData={{
    srcSet: 'small.jpg 320w, medium.jpg 700w, large.jpg 2000w',
    sizes: '(max-width: 2000px) 100vw, 2000px'
  }}
  placeholder="tiny-image.jpg"
>
  {(src, loading, srcSetData) => (
    <img
      src={src}
      srcSet={srcSetData.srcSet}
      sizes={srcSetData.sizes}
      alt="an image"
    />
  )}
</ProgressiveImage>

With Intersection Observer Options - CodeSandbox

<ProgressiveImage
  delay={3000}
  src="large-image.jpg"
  placeholder="tiny-image.jpg"
  rootMargin="0% 0% 0%"
  threshold={[1]}
>
  {(src) => <img src={src} alt="an image" />}
</ProgressiveImage>

Component As Placeholder - CodeSandbox

If you want to use a component, such as a loading spinner, as a placeholder, you can make use of the loading argument in the render callback. It will be true while the main image is loading and false once it has fully loaded. Keep in mind that the placeholder props is required, so you will need to explicitly declare an empty string as it's value if you plan on using a component in the render callback.

const dominantImageColor = '#86356B';
const placeholder = (
  <div
    style={{ backgroundColor: dominantImageColor, height: 300, width: 500 }}
  />
);

<ProgressiveImage src="large-image.jpg" placeholder="" >
  {(src, loading) => {
    return loading ? placeholder : <img src={src} alt="an image" />;
  }}
</ProgressiveImage>;

Progressive Enhancement and No JavaScript

Since this component relies on JavaScript to replace the placeholder src with the full image src, you should use a fallback image if your application supports environments that do not have JavaScript enabled or is progressively enhanced.

You can do this by adding the fallback image inside of a <noscript> tag in the render callback you provide as the ProgressiveImage component's child.

<ProgressiveImage src="large-image.jpg" placeholder="tiny-image.jpg" >
  {(src) => {
    return (
      <div>
        <img className="progressive-image" src={src} />
        <noscript>
          <img className="progressive-image no-script" src="large-image.jpg" />
        </noscript>
      </div>
    );
  }}
</ProgressiveImage>

Props

Name	Type	Required	Description
children	function	true	returns src, loading, and srcSetData
delay	number	false	time in milliseconds before src image is loaded
onError	function	false	returns error event
placeholder	string | React.Node	true	the img src or React Component for the placeholder image
src	string	true	the src of the main image
srcSetData	{srcSet: "string", sizes: "string" }	false	srcset and sizes to be applied to the image
noRetry	boolean	false	flag to turn off re-trying (default: false)
noLazyLoad	boolean	false	flag to turn off lazy loading (default: false)
rootMargin	string	false	Intersection Observer Option (eg: "0% 0% 25%" -default)
threshold	number|Array<number>	false	Intersection Observer Option (eg: [0] -default)

Maintenance Status

Stable: Formidable is not planning to develop any new features for this project. We are still responding to bug reports and security concerns. We are still welcoming PRs for this project, but PRs that include new features should be small and easy to integrate and should not include breaking changes.

License

Licensed under the MIT License, Copyright © 2019-present.

See LICENSE for more information.