43 lines
940 B
JavaScript
43 lines
940 B
JavaScript
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'use strict'
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/*!
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* Canvas - PNGStream
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* Copyright (c) 2010 LearnBoost <tj@learnboost.com>
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* MIT Licensed
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*/
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const { Readable } = require('stream')
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function noop () {}
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class PNGStream extends Readable {
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constructor (canvas, options) {
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super()
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if (options &&
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options.palette instanceof Uint8ClampedArray &&
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options.palette.length % 4 !== 0) {
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throw new Error('Palette length must be a multiple of 4.')
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}
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this.canvas = canvas
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this.options = options || {}
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}
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_read () {
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// For now we're not controlling the c++ code's data emission, so we only
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// call canvas.streamPNGSync once and let it emit data at will.
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this._read = noop
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this.canvas.streamPNGSync((err, chunk, len) => {
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if (err) {
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this.emit('error', err)
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} else if (len) {
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this.push(chunk)
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} else {
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this.push(null)
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}
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}, this.options)
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}
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}
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module.exports = PNGStream
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