Compress & optimize PDF files in Swift

//---------------------------------------------------------------------------------------
// Copyright (c) 2001-2019 by PDFTron Systems Inc. All Rights Reserved.
// Consult legal.txt regarding legal and license information.
//---------------------------------------------------------------------------------------

import PDFNet
import Foundation

//---------------------------------------------------------------------------------------
// 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).
//---------------------------------------------------------------------------------------

func runOptimizerTest() -> Int {
    return autoreleasepool {
        var ret: Int = 0

        // 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.
        //
        do {
            try PTPDFNet.catchException {
                let doc: PTPDFDoc = PTPDFDoc(filepath: Bundle.main.path(forResource: "newsletter", ofType: "pdf"))
                doc.initSecurityHandler()
                
                PTOptimizer.optimize(doc, settings: PTOptimizerSettings())
                
                doc.save(toFile: URL(fileURLWithPath: NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]).appendingPathComponent("newsletter_opt1.pdf").path, flags: e_ptlinearized.rawValue)
            }
        } catch let e as NSError {
            print("\(e)")
            ret = 1
        }
        
        //--------------------------------------------------------------------------------
        // Example 2) Reduce image quality and use jpeg compression for
        // non monochrome images.
        do {
            try PTPDFNet.catchException {
                let doc: PTPDFDoc = PTPDFDoc(filepath: Bundle.main.path(forResource: "newsletter", ofType: "pdf"))
                doc.initSecurityHandler()
                
                let image_settings: PTImageSettings = PTImageSettings()
                
                // low quality jpeg compression
                image_settings.setCompressionMode(e_ptjpeg)
                image_settings.setQuality(1)
                
                // Set the output dpi to be standard screen resolution
                image_settings.setImageDPI(144, resampling: 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);
                
                let opt_settings: PTOptimizerSettings = PTOptimizerSettings()
                opt_settings.setColorImageSettings(image_settings)
                opt_settings.setGrayscaleImageSettings(image_settings)
                
                // use the same settings for both color and grayscale images
                PTOptimizer.optimize(doc, settings: opt_settings)
                
                doc.save(toFile: URL(fileURLWithPath: NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]).appendingPathComponent("newsletter_opt2.pdf").path, flags: e_ptlinearized.rawValue)
            }
        } catch let e as NSError {
            print("\(e)")
            ret = 1
        }
        
        //--------------------------------------------------------------------------------
        // Example 3) Use monochrome image settings and default settings
        // for color and grayscale images.
        do {
            try PTPDFNet.catchException {
                let doc: PTPDFDoc = PTPDFDoc(filepath: Bundle.main.path(forResource: "newsletter", ofType: "pdf"))
                doc.initSecurityHandler()
                
                let mono_image_settings: PTMonoImageSettings = PTMonoImageSettings()
                
                mono_image_settings.setCompressionMode(e_ptmn_jbig2)
                mono_image_settings.forceRecompression(true)
                
                let opt_settings: PTOptimizerSettings = PTOptimizerSettings()
                opt_settings.setMonoImageSettings(mono_image_settings)
                
                PTOptimizer.optimize(doc, settings: opt_settings)
                
                doc.save(toFile: URL(fileURLWithPath: NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]).appendingPathComponent("newsletter_opt3.pdf").path, flags: e_ptlinearized.rawValue)
            }
        } catch let e as NSError {
            print("\(e)")
            ret = 1
        }
        
        // ----------------------------------------------------------------------
        // Example 4) Use Flattener to simplify content in this document
        // using default settings
        do {
            try PTPDFNet.catchException {
                let doc: PTPDFDoc = PTPDFDoc(filepath: Bundle.main.path(forResource: "TigerText", ofType: "pdf"))
                doc.initSecurityHandler()
                
                let fl: PTFlattener = PTFlattener()
                // 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(e_ptthreshold_keep_most)
                
                // We use e_ptfast 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.
                fl.process(doc, mode: e_ptfast)
                doc.save(toFile: URL(fileURLWithPath: NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]).appendingPathComponent("TigerText_flatten.pdf").path, flags: e_ptlinearized.rawValue)
            }
        } catch let e as NSError {
            print("\(e)")
            ret = 1
        }
        
        print("Done")
        return ret
    }
}