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103 lines
3.8 KiB
JavaScript
103 lines
3.8 KiB
JavaScript
const fs = require('fs')
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const { Image } = require('./js-binding')
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const { Readable } = require('stream')
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let http, https
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const MAX_REDIRECTS = 20,
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REDIRECT_STATUSES = new Set([301, 302]),
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DATA_URI = /^\s*data:/
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/**
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* Loads the given source into canvas Image
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* @param {string|URL|Image|Buffer} source The image source to be loaded
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* @param {object} options Options passed to the loader
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*/
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module.exports = async function loadImage(source, options = {}) {
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// load readable stream as image
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if (source instanceof Readable) return createImage(await consumeStream(source), options.alt)
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// use the same buffer without copying if the source is a buffer
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if (Buffer.isBuffer(source)) return createImage(source, options.alt)
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// construct a buffer if the source is buffer-like
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if (isBufferLike(source)) return createImage(Buffer.from(source), options.alt)
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// if the source is Image instance, copy the image src to new image
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if (source instanceof Image) return createImage(source.src, options.alt)
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// if source is string and in data uri format, construct image using data uri
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if (typeof source === 'string' && DATA_URI.test(source)) {
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const commaIdx = source.indexOf(',')
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const encoding = source.lastIndexOf('base64', commaIdx) < 0 ? 'utf-8' : 'base64'
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const data = Buffer.from(source.slice(commaIdx + 1), encoding)
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return createImage(data, options.alt)
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}
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// if source is a string or URL instance
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if (typeof source === 'string' || source instanceof URL) {
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// if the source exists as a file, construct image from that file
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if (fs.existsSync(source)) {
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return createImage(await fs.promises.readFile(source), options.alt)
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} else {
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// the source is a remote url here
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source = !(source instanceof URL) ? new URL(source) : source
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// attempt to download the remote source and construct image
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const data = await new Promise((resolve, reject) =>
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makeRequest(
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source,
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resolve,
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reject,
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typeof options.maxRedirects === 'number' && options.maxRedirects >= 0 ? options.maxRedirects : MAX_REDIRECTS,
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options.requestOptions,
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),
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)
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return createImage(data, options.alt)
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}
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}
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// throw error as dont support that source
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throw new TypeError('unsupported image source')
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}
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function makeRequest(url, resolve, reject, redirectCount, requestOptions) {
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const isHttps = url.protocol === 'https:'
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// lazy load the lib
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const lib = isHttps ? (!https ? (https = require('https')) : https) : !http ? (http = require('http')) : http
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lib
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.get(url, requestOptions || {}, (res) => {
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const shouldRedirect = REDIRECT_STATUSES.has(res.statusCode) && typeof res.headers.location === 'string'
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if (shouldRedirect && redirectCount > 0)
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return makeRequest(new URL(res.headers.location), resolve, reject, redirectCount - 1, requestOptions)
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if (typeof res.statusCode === 'number' && (res.statusCode < 200 || res.statusCode >= 300)) {
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return reject(new Error(`remote source rejected with status code ${res.statusCode}`))
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}
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consumeStream(res).then(resolve, reject)
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})
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.on('error', reject)
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}
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// use stream/consumers in the future?
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function consumeStream(res) {
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return new Promise((resolve, reject) => {
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const chunks = []
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res.on('data', (chunk) => chunks.push(chunk))
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res.on('end', () => resolve(Buffer.concat(chunks)))
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res.on('error', reject)
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})
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}
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function createImage(src, alt) {
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const image = new Image()
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image.src = src
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if (typeof alt === 'string') image.alt = alt
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return image
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}
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function isBufferLike(src) {
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return (
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(src && src.type === 'Buffer') ||
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Array.isArray(src) ||
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src instanceof ArrayBuffer ||
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src instanceof SharedArrayBuffer ||
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src instanceof Object.getPrototypeOf(Uint8Array)
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)
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}
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