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Compress & optimize PDF files in Go

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Sample Go code for using PDFTron SDK to reduce PDF file size by removing redundant information and compressing data streams using the latest in image compression technology. Learn more about our Go PDF Library.

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

package main
import (
	. "pdftron"

import  "pdftron/Samples/LicenseKey/GO"
// 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 main(){
    // Relative path to the folder containing the test files.
    inputPath := "../../TestFiles/"
    outputPath := "../../TestFiles/Output/"
    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.
    doc := NewPDFDoc(inputPath + inputFileName + ".pdf")
    doc.Save(outputPath + inputFileName + "_opt1.pdf", uint(SDFDocE_linearized))
    // Example 2) Reduce image quality and use jpeg compression for
    // non monochrome images.    
    doc = NewPDFDoc(inputPath + inputFileName + ".pdf")
    imageSettings := NewImageSettings()
    // low quality jpeg compression
    // Set the output dpi to be standard screen resolution
    // this option will recompress images not compressed with
    // jpeg compression and use the result if the new image
    // is smaller.
    // 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

    optSettings := NewOptimizerSettings()

    // use the same settings for both color and grayscale images
    OptimizerOptimize(doc, optSettings)
    doc.Save(outputPath + inputFileName + "_opt2.pdf", uint(SDFDocE_linearized))
    // Example 3) Use monochrome image settings and default settings
    // for color and grayscale images. 
    doc = NewPDFDoc(inputPath + inputFileName + ".pdf")

    monoImageSettings := NewMonoImageSettings()

    optSettings = NewOptimizerSettings()
    OptimizerOptimize(doc, optSettings)
    doc.Save(outputPath + inputFileName + "_opt3.pdf", uint(SDFDocE_linearized))
    // ----------------------------------------------------------------------
    // Example 4) Use Flattener to simplify content in this document
    // using default settings
    doc = NewPDFDoc(inputPath + "TigerText.pdf")
    fl := NewFlattener()
    // The following lines can increase the resolution of background
    // images.

    // This line can be used to output Flate compressed background
    // images rather than DCTDecode compressed images which is the default

    // In order to adjust thresholds for when text is Flattened
    // the following function can be used.

    // 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, FlattenerE_fast)
    doc.Save(outputPath + "TigerText_flatten.pdf", uint(SDFDocE_linearized))

    // ----------------------------------------------------------------------
    // Example 5) Optimize a PDF for viewing using SaveViewerOptimized.
    doc = NewPDFDoc(inputPath + inputFileName + ".pdf")
    opts := NewViewerOptimizedOptions()

    // set the maximum dimension (width or height) that thumbnails will have.

    // 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(outputPath + inputFileName + "_SaveViewerOptimized.pdf", opts)