This article originally appeared on Medium.com
Building the React Image Optimization Component for Tueri.io
Let’s face it, image optimization is hard. We want to make it effortless.
Full source code can be found on GitHub
When we set out to build our React Component there were a few problems we wanted to solve:
Automatically decide image width for any device based on the parent container.
Use the best possible image format the user’s browser supports.
Automatic image lazy loading.
Automatic low-quality image placeholders (LQIP).
Oh, and it had to be effortless for React Developers to use.
This is what we came up with:
<Img src={ tueriImageId } alt='Alt Text' /> Easy right? Let’s dive in.
Calculating the image size:
Create a <figure /> element, detect the width and build an image URL:
class Img extends React.Component { constructor(props) { super(props) this.state = { width: 0 } this.imgRef = React.createRef() } componentDidMount() { const width = this.imgRef.current.clientWidth this.setState({ width }) } render() { // Destructure props and state const { src, alt, options = {}, ext = 'jpg' } = this.props const { width } = this.state // Create an empty query string let queryString = '' // If width is specified, otherwise use auto-detected width options['w'] = options['w'] || width // Loop through option object and build queryString Object.keys(options).map((option, i) => { return queryString += `${i < 1 ? '?' : '&'}${option}=${options[option]}` }) return( <figure ref={this.imgRef}> { // If the container width has been set, display the image else null width > 0 ? ( <img src={`https://cdn.tueri.io/${ src }/${ kebabCase(alt) }.${ ext }${ queryString }`} alt={ alt } /> ) : null } </figure> ) } } export default Img This returns the following HTML:
<figure> <img src="https://cdn.tueri.io/tueriImageId/alt-text.jpg?w=autoCalculatedWidth" alt="Alt Text" /> </figure> Use the best possible image format:
Next, we needed to add support for detecting WebP images and having the Tueri service return the image in the WebP format:
class Img extends React.Component { constructor(props) { // ... this.window = typeof window !== 'undefined' && window this.isWebpSupported = this.isWebpSupported.bind(this) } // ... isWebpSupported() { if (!this.window.createImageBitmap) { return false; } return true; } render() { // ... // If a format has not been specified, detect webp support // Set the fm (format) option in the image URL if (!options['fm'] && this.isWebpSupported) { options['fm'] = 'webp' } // ... return ( // ... ) } } // ... This returns the following HTML:
<figure> <img src="https://cdn.tueri.io/tueriImageId/alt-text.jpg?w=autoCalculatedWidth&fm=webp" alt="Alt Text" /> </figure> Automatic image lazy loading:
Now, we need to find out if the <figure /> element is in the viewport, plus we add a little buffer area so the images load just before being scrolled into view.
class Img extends React.Component { constructor(props) { // ... this.state = { // ... isInViewport: false lqipLoaded: false } // ... this.handleViewport = this.handleViewport.bind(this) } componentDidMount() { // ... this.handleViewport() this.window.addEventListener('scroll', this.handleViewport) } handleViewport() { // Only run if the image has not already been loaded if (this.imgRef.current && !this.state.lqipLoaded) { // Get the viewport height const windowHeight = this.window.innerHeight // Get the top position of the <figure /> element const imageTopPosition = this.imgRef.current.getBoundingClientRect().top // Multiply the viewport * buffer (default buffer: 1.5) const buffer = typeof this.props.buffer === 'number' && this.props.buffer > 1 && this.props.buffer < 10 ? this.props.buffer : 1.5 // If <figure /> is in viewport if (windowHeight * buffer > imageTopPosition) { this.setState({ isInViewport: true }) } } } // ... componentWillUnmount() { this.window.removeEventListener('scroll', this.handleViewport) } render() { // Destructure props and state // ... const { isInViewport, width } = this.state // ... return ( <figure ref={this.imgRef}> { // If the container width has been set, display the image else null isInViewport && width > 0 ? ( <img onLoad={ () => { this.setState({ lqipLoaded: true }) } } // ... /> ) : null } </figure> ) } } export default Img Automatic low-quality image placeholders (LQIP):
Finally, when an image is in the viewport, we want to load a 1/10 size blurred image, then fade out the placeholder image when the full-size image is loaded:
class Img extends React.Component { constructor(props) { // ... this.state = { // ... fullsizeLoaded: false } // ... } // ... render() { // Destructure props and state // ... const { isInViewport, width, fullsizeLoaded } = this.state // ... // Modify the queryString for the LQIP image: replace the width param with a value 1/10 the fullsize const lqipQueryString = queryString.replace(`w=${ width }`, `w=${ Math.round(width * 0.1) }`) // Set the default styles. The full size image should be absolutely positioned within the <figure /> element const styles = { figure: { position: 'relative', margin: 0 }, lqip: { width: '100%', filter: 'blur(5px)', opacity: 1, transition: 'all 0.5s ease-in' }, fullsize: { position: 'absolute', top: '0px', left: '0px', transition: 'all 0.5s ease-in' } } // When the fullsize image is loaded, fade out the LQIP if (fullsizeLoaded) { styles.lqip.opacity = 0 } return( <figure style={ styles.figure } // ... > { isInViewport && width > 0 ? ( <React.Fragment> {/* Load fullsize image in background */} <img onLoad={ () => { this.setState({ fullsizeLoaded: true }) } } style={ styles.fullsize } src={`https://cdn.tueri.io/${ src }/${ kebabCase(alt) }.${ ext }${ queryString }`} alt={ alt } /> {/* Load LQIP in foreground */} <img onLoad={ () => { this.setState({ lqipLoaded: true }) } } style={ styles.lqip } src={`https://cdn.tueri.io/${ src }/${ kebabCase(alt) }.${ ext }${ lqipQueryString }`} alt={ alt } /> </React.Fragment> ) : null } </figure> ) } } // ... Putting it all together:
Image optimization made effortless. Just swap out your regular <img /> elements for the Tueri <Img /> and never worry about optimization again.
import React from 'react' import PropTypes from 'prop-types' import { TueriContext } from './Provider' import kebabCase from 'lodash.kebabcase' class Img extends React.Component { constructor(props) { super(props) this.state = { isInViewport: false, width: 0, height: 0, lqipLoaded: false, fullsizeLoaded: false } this.imgRef = React.createRef() this.window = typeof window !== 'undefined' && window this.handleViewport = this.handleViewport.bind(this) this.isWebpSupported = this.isWebpSupported.bind(this) } componentDidMount() { const width = this.imgRef.current.clientWidth this.setState({ width }) this.handleViewport() this.window.addEventListener('scroll', this.handleViewport) } handleViewport() { if (this.imgRef.current && !this.state.lqipLoaded) { const windowHeight = this.window.innerHeight const imageTopPosition = this.imgRef.current.getBoundingClientRect().top const buffer = typeof this.props.buffer === 'number' && this.props.buffer > 1 && this.props.buffer < 10 ? this.props.buffer : 1.5 if (windowHeight * buffer > imageTopPosition) { this.setState({ isInViewport: true }) } } } isWebpSupported() { if (!this.window.createImageBitmap) { return false; } return true; } componentWillUnmount() { this.window.removeEventListener('scroll', this.handleViewport) } render() { // Destructure props and state const { src, alt, options = {}, ext = 'jpg' } = this.props const { isInViewport, width, fullsizeLoaded } = this.state // Create an empty query string let queryString = '' // If width is specified, otherwise use auto-detected width options['w'] = options['w'] || width // If a format has not been specified, detect webp support if (!options['fm'] && this.isWebpSupported) { options['fm'] = 'webp' } // Loop through option prop and build queryString Object.keys(options).map((option, i) => { return queryString += `${i < 1 ? '?' : '&'}${option}=${options[option]}` }) // Modify the queryString for the LQIP image: replace the width param with a value 1/10 the fullsize const lqipQueryString = queryString.replace(`w=${ width }`, `w=${ Math.round(width * 0.1) }`) const styles = { figure: { position: 'relative', margin: 0 }, lqip: { width: '100%', filter: 'blur(5px)', opacity: 1, transition: 'all 0.5s ease-in' }, fullsize: { position: 'absolute', top: '0px', left: '0px', transition: 'all 0.5s ease-in' } } // When the fullsize image is loaded, fade out the LQIP if (fullsizeLoaded) { styles.lqip.opacity = 0 } const missingALt = 'ALT TEXT IS REQUIRED' return( // Return the CDN domain from the TueriProvider <TueriContext.Consumer> {({ domain }) => ( <figure style={ styles.figure } ref={this.imgRef} > { // isInViewport && width > 0 ? ( <React.Fragment> {/* Load fullsize image in background */} <img onLoad={ () => { this.setState({ fullsizeLoaded: true }) } } style={ styles.fullsize } src={`${ domain }/${ src }/${ kebabCase(alt || missingALt) }.${ ext }${ queryString }`} alt={ alt || missingALt } /> {/* Load LQIP in foreground */} <img onLoad={ () => { this.setState({ lqipLoaded: true }) } } style={ styles.lqip } src={`${ domain }/${ src }/${ kebabCase(alt || missingALt) }.${ ext }${ lqipQueryString }`} alt={ alt || missingALt } /> </React.Fragment> ) : null } </figure> )} </TueriContext.Consumer> ) } } Img.propTypes = { src: PropTypes.string.isRequired, alt: PropTypes.string.isRequired, options: PropTypes.object, ext: PropTypes.string, buffer: PropTypes.number } export default Img See it in action:
Try out a live demo on CodeSandbox:
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