Compress & optimize PDF files in JavaScript

//---------------------------------------------------------------------------------------
// Copyright (c) 2001-2023 by Apryse Software Inc. All Rights Reserved.
// Consult legal.txt regarding legal and license information.
//---------------------------------------------------------------------------------------

//---------------------------------------------------------------------------------------
// The following sample illustrates how to reduce PDF file size using 'pdftron.PDF.Optimizer'.
// The sample also shows how to simplify and optimize PDF documents for viewing on mobile devices 
// and on the Web using 'pdftron.PDF.Flattener'.
//
// @note Both 'Optimizer' and 'Flattener' are separately licensable add-on options to the core PDFNet license.
//
// ----
//
// 'pdftron.PDF.Optimizer' can be used to optimize PDF documents by reducing the file size, removing 
// redundant information, and compressing data streams using the latest in image compression technology. 
//
// PDF Optimizer can compress and shrink PDF file size with the following operations:
// - Remove duplicated fonts, images, ICC profiles, and any other data stream. 
// - Optionally convert high-quality or print-ready PDF files to small, efficient and web-ready PDF. 
// - Optionally down-sample large images to a given resolution. 
// - Optionally compress or recompress PDF images using JBIG2 and JPEG2000 compression formats. 
// - Compress uncompressed streams and remove unused PDF objects. 
//
// ----
//
// 'pdftron.PDF.Flattener' can be used to speed-up PDF rendering on mobile devices and on the Web by 
// simplifying page content (e.g. flattening complex graphics into images) while maintaining vector text 
// whenever possible.
//
// Flattener can also be used to simplify process of writing custom converters from PDF to other formats. 
// In this case, Flattener can be used as first step in the conversion pipeline to reduce any PDF to a 
// very simple representation (e.g. vector text on top of a background image).
//---------------------------------------------------------------------------------------

const { PDFNet } = require('@pdftron/pdfnet-node');
const PDFTronLicense = require('../LicenseKey/LicenseKey');

((exports) => {
  'use strict';

  exports.runOptimizerTest = () => {
    const main = async () => {
      const inputPath = '../TestFiles/';
      const outputPath = inputPath + 'Output/';
      const inputFilename = 'newsletter';

      // The first step in every application using PDFNet is to initialize the 
      // library and set the path to common PDF resources. The library is usually 
      // initialized only once, but calling Initialize() multiple times is also fine.

      //--------------------------------------------------------------------------------
      // Example 1) Simple optimization of a pdf with default settings. 
      //
      try {
        const doc = await PDFNet.PDFDoc.createFromFilePath(inputPath + inputFilename + '.pdf');
        await doc.initSecurityHandler();
        await PDFNet.Optimizer.optimize(doc);
        doc.save(outputPath + inputFilename + '_opt1.pdf', PDFNet.SDFDoc.SaveOptions.e_linearized);
      }
      catch (err) {
        console.log(err);
      }

      //--------------------------------------------------------------------------------
      // Example 2) Reduce image quality and use jpeg compression for
      // non monochrome images.
      try {
        const doc = await PDFNet.PDFDoc.createFromFilePath(inputPath + inputFilename + '.pdf');
        await doc.initSecurityHandler();
        const image_settings = new PDFNet.Optimizer.ImageSettings();

        // low quality jpeg compression
        image_settings.setCompressionMode(PDFNet.Optimizer.ImageSettings.CompressionMode.e_jpeg);
        image_settings.setQuality(1);

        // Set the output dpi to be standard screen resolution
        image_settings.setImageDPI(144, 96);

        // this option will recompress images not compressed with
        // jpeg compression and use the result if the new image
        // is smaller.
        image_settings.forceRecompression(true);

        // this option is not commonly used since it can 
        // potentially lead to larger files.  It should be enabled
        // only if the output compression specified should be applied
        // to every image of a given type regardless of the output image size
        //image_settings.forceChanges(true);

        const opt_settings = new PDFNet.Optimizer.OptimizerSettings();
        opt_settings.setColorImageSettings(image_settings);
        opt_settings.setGrayscaleImageSettings(image_settings);

        // use the same settings for both color and grayscale images
        await PDFNet.Optimizer.optimize(doc, opt_settings);

        doc.save(outputPath + inputFilename + '_opt2.pdf', PDFNet.SDFDoc.SaveOptions.e_linearized);
      }
      catch (err) {
        console.log(err);
      }

      //--------------------------------------------------------------------------------
      // Example 3) Use monochrome image settings and default settings
      // for color and grayscale images. 
      try {
        const doc = await PDFNet.PDFDoc.createFromFilePath(inputPath + inputFilename + '.pdf');
        await doc.initSecurityHandler();

        const mono_image_settings = new PDFNet.Optimizer.MonoImageSettings();

        mono_image_settings.setCompressionMode(PDFNet.Optimizer.MonoImageSettings.CompressionMode.e_jbig2);
        mono_image_settings.forceRecompression(true);

        const opt_settings = new PDFNet.Optimizer.OptimizerSettings();

        opt_settings.setMonoImageSettings(mono_image_settings);

        await PDFNet.Optimizer.optimize(doc, opt_settings);
        doc.save(outputPath + inputFilename + '_opt3.pdf', PDFNet.SDFDoc.SaveOptions.e_linearized);
      }
      catch (err) {
        console.log(err);
      }

      // ----------------------------------------------------------------------
      // Example 4) Use Flattener to simplify content in this document
      // using default settings
      try {
        const doc = await PDFNet.PDFDoc.createFromFilePath(inputPath + 'TigerText.pdf');
        await doc.initSecurityHandler();

        const fl = await PDFNet.Flattener.create();

        // The following lines can increase the resolution of background
        // images.
        //fl.setDPI(300);
        //fl.setMaximumImagePixels(5000000);

        // This line can be used to output Flate compressed background
        // images rather than DCTDecode compressed images which is the default
        //fl.setPreferJPG(false);

        // In order to adjust thresholds for when text is Flattened
        // the following function can be used.
        //fl.setThreshold(PDFNet.Flattener.Threshold.e_keep_most);

        // We use e_fast option here since it is usually preferable
        // to avoid Flattening simple pages in terms of size and 
        // rendering speed. If the desire is to simplify the 
        // document for processing such that it contains only text and
        // a background image e_simple should be used instead.
        await fl.process(doc, PDFNet.Flattener.Mode.e_fast);

        doc.save(outputPath + 'TigerText_flatten.pdf', PDFNet.SDFDoc.SaveOptions.e_linearized);
      }
      catch (err) {
        console.log(err);
      }

      //--------------------------------------------------------------------------------
      // Example 5) Optimize a PDF for viewing using SaveViewerOptimized.
      try {
        const doc = await PDFNet.PDFDoc.createFromFilePath(inputPath + inputFilename + '.pdf');
        doc.initSecurityHandler();

        const opts = new PDFNet.PDFDoc.ViewerOptimizedOptions();

        // set the maximum dimension (width or height) that thumbnails will have.
        opts.setThumbnailSize(1500);

        // set thumbnail rendering threshold. A number from 0 (include all thumbnails) to 100 (include only the first thumbnail) 
        // representing the complexity at which SaveViewerOptimized would include the thumbnail. 
        // By default it only produces thumbnails on the first and complex pages. 
        // The following line will produce thumbnails on every page.
        // opts.setThumbnailRenderingThreshold(0); 

        await doc.saveViewerOptimized(outputPath + inputFilename + '_SaveViewerOptimized.pdf', opts);
      }
      catch (err) {
        console.log(err);
      }
    };
    PDFNet.runWithCleanup(main, PDFTronLicense.Key).catch(function (error) {
      console.log('Error: ' + JSON.stringify(error));
    }).then(function () { return PDFNet.shutdown(); });
  };
  exports.runOptimizerTest();
})(exports);
// eslint-disable-next-line spaced-comment
//# sourceURL=OptimizerTest.js