Compress & optimize PDF files in Obj-C

//---------------------------------------------------------------------------------------
// Copyright (c) 2001-2021 by PDFTron Systems Inc. All Rights Reserved.
// Consult legal.txt regarding legal and license information.
//---------------------------------------------------------------------------------------

#import <OBJC/PDFNetOBJC.h>
#import <Foundation/Foundation.h>

//---------------------------------------------------------------------------------------
// 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). 
//---------------------------------------------------------------------------------------
int main(int argc, char * argv[])
{
    @autoreleasepool {

        int ret = 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.
        [PTPDFNet Initialize: 0];

        //--------------------------------------------------------------------------------
        // Example 1) Simple optimization of a pdf with default settings. 
        //
        @try
        {
            PTPDFDoc *doc = [[PTPDFDoc alloc] initWithFilepath: @"../../TestFiles/newsletter.pdf"];
            [doc InitSecurityHandler];

            [PTOptimizer Optimize: doc settings: [[PTOptimizerSettings alloc] init]];

            [doc SaveToFile: @"../../TestFiles/Output/newsletter_opt1.pdf" flags: e_ptlinearized];
        }
        @catch (NSException *e)
        {
            NSLog(@"%@", e.reason);
            ret = 1;
        }

        //--------------------------------------------------------------------------------
        // Example 2) Reduce image quality and use jpeg compression for
        // non monochrome images.
        @try
        {
            PTPDFDoc *doc = [[PTPDFDoc alloc] initWithFilepath: @"../../TestFiles/newsletter.pdf"];
            [doc InitSecurityHandler];

            PTImageSettings *image_settings = [[PTImageSettings alloc] init];

            // 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: YES];

            // 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);


            PTOptimizerSettings *opt_settings = [[PTOptimizerSettings alloc] init];
            [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 SaveToFile: @"../../TestFiles/Output/newsletter_opt2.pdf" flags: e_ptlinearized];
        }
        @catch (NSException *e)
        {
            NSLog(@"%@", e.reason);    
            ret = 1;
        }
    

        //--------------------------------------------------------------------------------
        // Example 3) Use monochrome image settings and default settings
        // for color and grayscale images. 
        @try
        {
            PTPDFDoc *doc = [[PTPDFDoc alloc] initWithFilepath: @"../../TestFiles/newsletter.pdf"];
            [doc InitSecurityHandler];

            PTMonoImageSettings *mono_image_settings = [[PTMonoImageSettings alloc] init];

            [mono_image_settings SetCompressionMode: e_ptmn_jbig2];
            [mono_image_settings ForceRecompression: true];

            PTOptimizerSettings *opt_settings = [[PTOptimizerSettings alloc] init];
            [opt_settings SetMonoImageSettings: mono_image_settings];

            [PTOptimizer Optimize: doc settings: opt_settings];

            [doc SaveToFile: @"../../TestFiles/Output/newsletter_opt3.pdf" flags: e_ptlinearized];
        }
        @catch (NSException *e)
        {
            NSLog(@"%@", e.reason);    
            ret = 1;        
        }
        
        // ----------------------------------------------------------------------
        // Example 4) Use Flattener to simplify content in this document
        // using default settings
        @try
        {
            PTPDFDoc *doc = [[PTPDFDoc alloc] initWithFilepath: @"../../TestFiles/TigerText.pdf"];
            [doc InitSecurityHandler];
            
            PTFlattener *fl = [[PTFlattener alloc] init];
            // 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_threshold_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 SaveToFile: @"../../TestFiles/Output/TigerText_flatten.pdf" flags: e_ptlinearized];
        }
        @catch (NSException *e)
        {
            NSLog(@"%@", e.reason);
            ret = 1;
        }

        // ----------------------------------------------------------------------
        // Example 5) Optimize a PDF for viewing using SaveViewerOptimized.
        @try
        {
            PTPDFDoc *doc = [[PTPDFDoc alloc] initWithFilepath: @"../../TestFiles/newsletter.pdf"];
            [doc InitSecurityHandler];
            
            PTViewerOptimizedOptions *options = [[PTViewerOptimizedOptions alloc] init];

            // set the maximum dimension (width or height) that thumbnails will have.
            [options 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.
            // [options SetThumbnailRenderingThreshold: 0];

            [doc SaveViewerOptimized: @"../../TestFiles/Output/newsletter_SaveViewerOptimized.pdf" opts: options];
        }
        @catch (NSException *e)
        {
            NSLog(@"%@", e.reason);
            ret = 1;
        }

        [PTPDFNet Terminate: 0];        
        //NSLog(@"Done");
        return ret;
    }
}