forked from vercel/next.js
/
image.tsx
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/
image.tsx
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import React, { ReactElement, useEffect, useRef } from 'react'
import Head from '../next-server/lib/head'
const loaders = new Map<LoaderKey, (props: LoaderProps) => string>([
['imgix', imgixLoader],
['cloudinary', cloudinaryLoader],
['akamai', akamaiLoader],
['default', defaultLoader],
])
type LoaderKey = 'imgix' | 'cloudinary' | 'akamai' | 'default'
type ImageData = {
sizes: number[]
loader: LoaderKey
path: string
}
type ImageProps = Omit<
JSX.IntrinsicElements['img'],
'src' | 'srcSet' | 'ref' | 'width' | 'height'
> & {
src: string
quality?: string
priority?: boolean
lazy?: boolean
unoptimized?: boolean
} & (
| { width: number; height: number; unsized?: false }
| { width?: number; height?: number; unsized: true }
)
const imageData: ImageData = process.env.__NEXT_IMAGE_OPTS as any
const { sizes: configSizes, loader: configLoader, path: configPath } = imageData
let cachedObserver: IntersectionObserver
const IntersectionObserver =
typeof window !== 'undefined' ? window.IntersectionObserver : null
function getObserver(): IntersectionObserver | undefined {
// Return shared instance of IntersectionObserver if already created
if (cachedObserver) {
return cachedObserver
}
// Only create shared IntersectionObserver if supported in browser
if (!IntersectionObserver) {
return undefined
}
return (cachedObserver = new IntersectionObserver(
(entries) => {
entries.forEach((entry) => {
if (entry.isIntersecting) {
let lazyImage = entry.target as HTMLImageElement
if (lazyImage.dataset.src) {
lazyImage.src = lazyImage.dataset.src
}
if (lazyImage.dataset.srcset) {
lazyImage.srcset = lazyImage.dataset.srcset
}
lazyImage.classList.remove('__lazy')
cachedObserver.unobserve(lazyImage)
}
})
},
{ rootMargin: '200px' }
))
}
function computeSrc(
src: string,
unoptimized: boolean,
quality?: string
): string {
if (unoptimized) {
return src
}
return callLoader({ src, quality })
}
type CallLoaderProps = {
src: string
width?: number
quality?: string
}
function callLoader(loaderProps: CallLoaderProps) {
let load = loaders.get(configLoader) || defaultLoader
return load({ root: configPath, ...loaderProps })
}
type SrcSetData = {
src: string
widths: number[]
quality?: string
}
function generateSrcSet({ src, widths, quality }: SrcSetData): string {
// At each breakpoint, generate an image url using the loader, such as:
// ' www.example.com/foo.jpg?w=480 480w, '
return widths
.map((width: number) => `${callLoader({ src, width, quality })} ${width}w`)
.join(', ')
}
type PreloadData = {
src: string
widths: number[]
sizes?: string
unoptimized?: boolean
quality?: string
}
function generatePreload({
src,
widths,
unoptimized = false,
sizes,
quality,
}: PreloadData): ReactElement {
// This function generates an image preload that makes use of the "imagesrcset" and "imagesizes"
// attributes for preloading responsive images. They're still experimental, but fully backward
// compatible, as the link tag includes all necessary attributes, even if the final two are ignored.
// See: https://web.dev/preload-responsive-images/
return (
<Head>
<link
rel="preload"
as="image"
href={computeSrc(src, unoptimized, quality)}
// @ts-ignore: imagesrcset and imagesizes not yet in the link element type
imagesrcset={generateSrcSet({ src, widths, quality })}
imagesizes={sizes}
/>
</Head>
)
}
export default function Image({
src,
sizes,
unoptimized = false,
priority = false,
lazy,
className,
quality,
width,
height,
unsized,
...rest
}: ImageProps) {
const thisEl = useRef<HTMLImageElement>(null)
// Sanity Checks:
// If priority and lazy are present, log an error and use priority only.
if (priority && lazy) {
if (process.env.NODE_ENV !== 'production') {
throw new Error(
`Image with src "${src}" has both "priority" and "lazy" properties. Only one should be used.`
)
}
}
if (!priority && typeof lazy === 'undefined') {
lazy = true
}
useEffect(() => {
const target = thisEl.current
if (target && lazy) {
const observer = getObserver()
if (observer) {
observer.observe(target)
return () => {
observer.unobserve(target)
}
}
}
}, [thisEl, lazy])
// Generate attribute values
const imgSrc = computeSrc(src, unoptimized, quality)
const imgSrcSet = !unoptimized
? generateSrcSet({
src,
widths: configSizes,
quality,
})
: undefined
let imgAttributes:
| {
src: string
srcSet?: string
}
| {
'data-src': string
'data-srcset'?: string
}
if (!lazy) {
imgAttributes = {
src: imgSrc,
}
if (imgSrcSet) {
imgAttributes.srcSet = imgSrcSet
}
} else {
imgAttributes = {
'data-src': imgSrc,
}
if (imgSrcSet) {
imgAttributes['data-srcset'] = imgSrcSet
}
className = className ? className + ' __lazy' : '__lazy'
}
// No need to add preloads on the client side--by the time the application is hydrated,
// it's too late for preloads
const shouldPreload = priority && typeof window === 'undefined'
let divStyle: React.CSSProperties | undefined
let imgStyle: React.CSSProperties | undefined
let wrapperStyle: React.CSSProperties | undefined
if (typeof height === 'number' && typeof width === 'number' && !unsized) {
// <Image src="i.png" width=100 height=100 />
const quotient = height / width
const ratio = isNaN(quotient) ? 1 : quotient * 100
wrapperStyle = {
maxWidth: '100%',
width,
}
divStyle = {
position: 'relative',
paddingBottom: `${ratio}%`,
}
imgStyle = {
height: '100%',
left: '0',
position: 'absolute',
top: '0',
width: '100%',
}
} else if (
typeof height === 'undefined' &&
typeof width === 'undefined' &&
unsized
) {
// <Image src="i.png" unsized />
if (process.env.NODE_ENV !== 'production') {
if (priority) {
// <Image src="i.png" unsized priority />
console.warn(
`Image with src "${src}" has both "priority" and "unsized" properties. Only one should be used.`
)
}
}
} else {
// <Image src="i.png" />
if (process.env.NODE_ENV !== 'production') {
throw new Error(
`Image with src "${src}" must use "width" and "height" properties or "unsized" property.`
)
}
}
return (
<div style={wrapperStyle}>
<div style={divStyle}>
{shouldPreload
? generatePreload({
src,
widths: configSizes,
unoptimized,
sizes,
})
: ''}
<img
{...rest}
{...imgAttributes}
className={className}
sizes={sizes}
ref={thisEl}
style={imgStyle}
/>
</div>
</div>
)
}
//BUILT IN LOADERS
type LoaderProps = CallLoaderProps & { root: string }
function normalizeSrc(src: string) {
return src[0] === '/' ? src.slice(1) : src
}
function imgixLoader({ root, src, width, quality }: LoaderProps): string {
const params = ['auto=format']
let paramsString = ''
if (width) {
params.push('w=' + width)
}
if (quality) {
params.push('q=' + quality)
}
if (params.length) {
paramsString = '?' + params.join('&')
}
return `${root}${normalizeSrc(src)}${paramsString}`
}
function akamaiLoader({ root, src, width }: LoaderProps): string {
return `${root}${normalizeSrc(src)}${width ? '?imwidth=' + width : ''}`
}
function cloudinaryLoader({ root, src, width, quality }: LoaderProps): string {
const params = ['f_auto']
let paramsString = ''
if (width) {
params.push('w_' + width)
}
if (quality) {
params.push('q_' + quality)
}
if (params.length) {
paramsString = params.join(',') + '/'
}
return `${root}${paramsString}${normalizeSrc(src)}`
}
function defaultLoader({ root, src, width, quality }: LoaderProps): string {
return `${root}?url=${encodeURIComponent(src)}&${
width ? `w=${width}&` : ''
}q=${quality || '100'}`
}