Compress & optimize PDF files in C#

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

using System;
using System.IO;

using pdftron;
using pdftron.Common;
using pdftron.Filters;
using pdftron.SDF;
using pdftron.PDF;

namespace PDFNetSamples
{
	class Class1
	{
		private static pdftron.PDFNetLoader pdfNetLoader = pdftron.PDFNetLoader.Instance();
		static Class1() {}
		
		/// <summary>
		/// 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).
		/// </summary>
		static void Main(string[] args)
		{
			PDFNet.Initialize(PDFTronLicense.Key);

			string input_path = "../../../../TestFiles/";
			string output_path = "../../../../TestFiles/Output/";
			string input_filename = "newsletter";


			//--------------------------------------------------------------------------------
			// Example 1) Simple optimization of a pdf with default settings. 
			//
			try
			{
				using (PDFDoc doc = new PDFDoc(input_path + input_filename + ".pdf"))
				{
					doc.InitSecurityHandler();
					Optimizer.Optimize(doc);
					doc.Save(output_path + input_filename + "_opt1.pdf", SDFDoc.SaveOptions.e_linearized);
				}
			}
			catch (PDFNetException e)
			{
				Console.WriteLine(e.Message);
			}
				
			//--------------------------------------------------------------------------------
			// Example 2) Reduce image quality and use jpeg compression for
			// non monochrome images.
			try
			{
				using (PDFDoc doc = new PDFDoc(input_path + input_filename + ".pdf"))
				{
					doc.InitSecurityHandler();

					Optimizer.ImageSettings image_settings = new Optimizer.ImageSettings();

					// low quality jpeg compression
					image_settings.SetCompressionMode(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);

					// use the same settings for both color and grayscale images
					Optimizer.OptimizerSettings opt_settings = new Optimizer.OptimizerSettings();
					opt_settings.SetColorImageSettings(image_settings);
					opt_settings.SetGrayscaleImageSettings(image_settings);

					
					Optimizer.Optimize(doc, opt_settings);

					doc.Save(output_path + input_filename + "_opt2.pdf", SDFDoc.SaveOptions.e_linearized);
				}
			}
			catch (PDFNetException e)
			{
				Console.WriteLine(e.Message);
			}


			//--------------------------------------------------------------------------------
			// Example 3) Use monochrome image settings and default settings
			// for color and grayscale images. 
			try
			{
				using (PDFDoc doc = new PDFDoc(input_path + input_filename + ".pdf"))
				{
					doc.InitSecurityHandler();

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

					mono_image_settings.SetCompressionMode(Optimizer.MonoImageSettings.CompressionMode.e_jbig2);
					mono_image_settings.ForceRecompression(true);

					Optimizer.OptimizerSettings opt_settings = new Optimizer.OptimizerSettings();
					opt_settings.SetMonoImageSettings(mono_image_settings);

					Optimizer.Optimize(doc, opt_settings);

					doc.Save(output_path + input_filename + "_opt3.pdf", SDFDoc.SaveOptions.e_linearized);
				}
			}
			catch (PDFNetException e)
			{
				Console.WriteLine(e.Message);
			}

			//-------------------------------------------------------------------------------
			// Example 4) Use Flattener to simplify content in this document
			// using default settings

			try
			{
				using (PDFDoc doc = new PDFDoc(input_path + "TigerText.pdf"))
				{
					doc.InitSecurityHandler();

					Flattener fl = new Flattener();

					// 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(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.
					fl.Process(doc,Flattener.FlattenMode.e_fast);

					doc.Save(output_path + "TigerText_flatten.pdf", SDFDoc.SaveOptions.e_linearized);
				}
			}
			catch (PDFNetException e)
			{
				Console.WriteLine(e.Message);	
			}

			//-------------------------------------------------------------------------------
			// Example 5) Optimize a PDF for viewing using SaveViewerOptimized.

			try
			{
				using (PDFDoc doc = new PDFDoc(input_path + input_filename + ".pdf"))
				{
					doc.InitSecurityHandler();

					ViewerOptimizedOptions opts = new 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); 

					doc.SaveViewerOptimized(output_path + input_filename + "_SaveViewerOptimized.pdf", opts);
				}
			}
			catch (PDFNetException e)
			{
				Console.WriteLine(e.Message);
			}
			PDFNet.Terminate();
		}
	}
}