pdf-stream

pdf-stream

Creates a stream from PDF

Node.js module for streaming PDF text content.

Based on PDF.js library.

Table of Contents

• Install
• Usage
• API
  • text(options)
  • new PDFReadable(options)
  • new PDFStringifyTransform(options)
• Contribute
• License

Install

  npm i pdf-stream --save

Usage

Basic

Text stream from PDF file

  'use strict';
  
  const text = require('pdf-stream').text;
  
  // Load file contents to ArrayBuffer synchronously
  let file = './example.pdf';
  let pdf = new Uint8Array(fs.readFileSync(file));
  
  // Stream PDF text to stdout
  text(pdf)
    .pipe(process.stdout);

Text stream from PDF link

You need the XMLHttpRequest as global variable. Install the xhr2 library locally:

  npm i xhr2 --save

  'use strict';
  
  const text = require('pdf-stream').text;
  global.XMLHttpRequest = require('xhr2'); // for PDFJS
  
  let pdf = 'https://mozilla.github.io/pdf.js/web/compressed.tracemonkey-pldi-09.pdf';
    
  text(pdf)
    .pipe(process.stdout);

Text stream from PDF link with metadata as XML string

If you got error:

  ReferenceError: DOMParser is not defined

You need the DOMParser as global variable, because PDF.js use it for XML metadata parsing. Install the xmldom library locally:

  npm i xmldom --save

  'use strict';
  
  const text = require('pdf-stream').text;
  global.XMLHttpRequest = require('xhr2');        // File download 
  global.DOMParser = require('xmldom').DOMParser; // XML Metadata parsing
  
  let pdf = 'https://mozilla.github.io/pdf.js/web/compressed.tracemonkey-pldi-09.pdf';
    
  text(pdf)
    .pipe(process.stdout);

Advanced

Create transform class for replacing string

  'use strict';
  
  const Transform = require('stream').Transform;
  const pdf_stream = require('pdf-stream');
  const PDFReadable = pdf_stream.PDFReadable;
  const PDFStringifyTransform = pdf_stream.PDFStringifyTransform;
  
  let url = 'https://mozilla.github.io/pdf.js/web/compressed.tracemonkey-pldi-09.pdf';
  
  // Transform class for replacing strings
  class ReplaceTransform extends Transform {
    constructor(options) {
      super({
        writableObjectMode: true,
        readableObjectMode: true
      });
      this.from = options.from;
      this.to = options.to;
    }
  
    // For every object
    _transform(obj, encoding, cb) {
      // Get text content items
      if (typeof obj.textContent !== 'undefined'
        && Array.isArray(obj.textContent.items)) {
        obj.textContent.items.forEach((item, i) => {
          // Working with the PDF.js `textContent` object
          // Replace substring to another
          obj.textContent.items[i].str = item.str.replace(this.from, this.to);
        });
      }
  
      this.push(obj);
      cb();
    }
  
  }
  
  // Pipeline
  new PDFReadable(url)
    .pipe(new ReplaceTransform({
      from: /trace/gi,
      to: ':-)'
    }))
    .pipe(new PDFStringifyTransform()) // Convert stream from object to string 
    .pipe(process.stdout);

API

All methods are streams, use them with .pipe().

text(options)

alternative usage: text(pdf, whitespace)

Gets text stream from PDF.

Convert PDF to text, optionally can replace whitespaces.

Options:

• pdf — URL or ArrayBuffer;
• whitespace — the string that replaces the whitespace ␣. Replacement disabled by default.

In the PDF.js viewer whitespaces is an empty string. For making output comparable with the viewer use: text(pdf, '')

Return: {stream.Readable}

new PDFReadable(options)

alternative usage: new PDFReadable(pdf)

Making the Readable stream in object mode from PDF text content.

Options:

• pdf — URL or ArrayBuffer;
• inherit from stream.Readable options.

Return: {stream.Readable}

new PDFStringifyTransform(options)

alternative usage: new PDFStringifyTransform(whitespace)

Transform PDF text content object to string.

Options:

• whitespace — the string that replaces the whitespace ␣. Replacement disabled by default;
• inherit from stream.Transform options.

Return: {stream.Readable}

Contribute

Contributors are welcome. Open an issue or submit pull request.

Small note: If editing the README, please conform to the standard-readme specification.

License

Apache 2.0

© Sergey N