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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,96 @@ | ||
| // based on https://github.com/mozilla/pdf.js/tree/master/examples/node/pdf2png | ||
| /*global Uint8Array*/ | ||
|
|
||
| import { strict as assert } from "assert"; | ||
| import Canvas from "canvas"; | ||
| import fs from "fs"; | ||
| import { getDocument } from "pdfjs-dist/legacy/build/pdf.mjs"; | ||
|
|
||
| class NodeCanvasFactory { | ||
| create(width, height) { | ||
| assert(width > 0 && height > 0, "Invalid canvas size"); | ||
| const canvas = Canvas.createCanvas(width, height); | ||
| const context = canvas.getContext("2d"); | ||
| return { | ||
| canvas, | ||
| context, | ||
| }; | ||
| } | ||
|
|
||
| reset(canvasAndContext, width, height) { | ||
| assert(canvasAndContext.canvas, "Canvas is not specified"); | ||
| assert(width > 0 && height > 0, "Invalid canvas size"); | ||
| canvasAndContext.canvas.width = width; | ||
| canvasAndContext.canvas.height = height; | ||
| } | ||
|
|
||
| destroy(canvasAndContext) { | ||
| assert(canvasAndContext.canvas, "Canvas is not specified"); | ||
|
|
||
| // Zeroing the width and height cause Firefox to release graphics | ||
| // resources immediately, which can greatly reduce memory consumption. | ||
| canvasAndContext.canvas.width = 0; | ||
| canvasAndContext.canvas.height = 0; | ||
| canvasAndContext.canvas = null; | ||
| canvasAndContext.context = null; | ||
| } | ||
| } | ||
|
|
||
| export async function convertToPng(sourceFile, targetPrefix) { | ||
| // Loading file from file system into typed array. | ||
| const data = new Uint8Array(fs.readFileSync(sourceFile)); | ||
|
|
||
| // Some PDFs need external cmaps. | ||
| const CMAP_URL = "../../../node_modules/pdfjs-dist/cmaps/"; | ||
| const CMAP_PACKED = true; | ||
|
|
||
| // Where the standard fonts are located. | ||
| const STANDARD_FONT_DATA_URL = | ||
| "../../../node_modules/pdfjs-dist/standard_fonts/"; | ||
|
|
||
| const canvasFactory = new NodeCanvasFactory(); | ||
|
|
||
| // Loading file from file system into typed array. | ||
| const pdfData = new Uint8Array(fs.readFileSync(sourceFile)); | ||
|
|
||
| // Load the PDF file. | ||
| const loadingTask = getDocument({ | ||
| data: pdfData, | ||
| cMapUrl: CMAP_URL, | ||
| cMapPacked: CMAP_PACKED, | ||
| }); | ||
| const pdfDocument = await loadingTask.promise; | ||
|
|
||
| for (let pageNumber = 1; pageNumber <= pdfDocument.numPages; pageNumber++) { | ||
| await processPage(pageNumber); | ||
| } | ||
| return pdfDocument.numPages; | ||
|
|
||
| async function processPage(pageNumber) { | ||
| console.log("# Processing page:", pageNumber); | ||
| // Get the page. | ||
| const page = await pdfDocument.getPage(pageNumber); | ||
| // Render the page on a Node canvas with 100% scale. | ||
| const viewport = page.getViewport({ scale: 1.0 }); | ||
| const canvasAndContext = canvasFactory.create( | ||
| viewport.width, | ||
| viewport.height | ||
| ); | ||
| const renderContext = { | ||
| canvasContext: canvasAndContext.context, | ||
| viewport, | ||
| }; | ||
|
|
||
| const renderTask = page.render(renderContext); | ||
| await renderTask.promise; | ||
| // Convert the canvas to an image buffer. | ||
| const image = canvasAndContext.canvas.toBuffer(); | ||
| const targetFile = `${targetPrefix}${pageNumber}.png`; | ||
|
|
||
| fs.writeFileSync(targetFile, image); | ||
| console.log("Finished converting page", pageNumber, "to", targetFile); | ||
| // Release page resources. | ||
| page.cleanup(); | ||
| } | ||
| } | ||
|
|
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