Go Requires Chilkat v11.7.0+

Remove a PDF's Old Revisions

See more PDF Optimization Examples

Demonstrates dropOldRevisions. A PDF that has been edited and saved several times carries every earlier revision: the superseded objects are still in the file, reachable through the older cross-reference sections. The audit reports them as "oldRevisions", and dropping them is often the single largest saving in a real document. Dropping them requires a full rewrite, which is why it invalidates existing digital signatures. Go

    success := false

    //  This example requires the Chilkat API to have been previously unlocked.
    //  See Global Unlock Sample for sample code.

    //  The PDF used in this example is available at grand_canyon_hiking_guide.pdf

    pdf := chilkat.NewPdf()
    success = pdf.LoadFile("qa_data/pdf/grand_canyon_hiking_guide.pdf")
    if success == false {
        fmt.Println(pdf.LastErrorText())
        pdf.DisposePdf()
        return
    }

    //  How much of this file is superseded revisions?
    json := chilkat.NewJsonObject()
    jsonOut := chilkat.NewJsonObject()
    success = pdf.Optimize("audit",json,jsonOut)
    if success == false {
        fmt.Println(pdf.LastErrorText())
        pdf.DisposePdf()
        json.DisposeJsonObject()
        jsonOut.DisposeJsonObject()
        return
    }

    fmt.Println("fileSize:     ", jsonOut.IntOf("fileSize"))
    fmt.Println("oldRevisions: ", jsonOut.IntOf("usage.oldRevisions.bytes"))

    //  Drop them, and nothing else, so that the saving is attributable.
    json.UpdateBool("compressUncompressed",false)
    json.UpdateBool("recompressFlate",false)
    json.UpdateBool("replaceLegacyFilters",false)
    json.UpdateBool("imagePredictors",false)
    json.UpdateBool("dedupeStreams",false)
    json.UpdateBool("dedupeObjects",false)
    json.UpdateBool("removeUnreferenced",false)
    json.UpdateBool("removeUnusedResources",false)
    json.UpdateBool("removeUnusedLayers",false)
    json.UpdateBool("coalesceContent",false)
    json.UpdateBool("tidyContent",false)
    json.UpdateBool("subsetFonts",false)
    json.UpdateBool("dropOldRevisions",true)

    success = pdf.Optimize("optimize",json,jsonOut)
    if success == false {
        fmt.Println(pdf.LastErrorText())
        pdf.DisposePdf()
        json.DisposeJsonObject()
        jsonOut.DisposeJsonObject()
        return
    }

    success = pdf.WriteFile("qa_output/grand_canyon_one_revision.pdf")
    if success == false {
        fmt.Println(pdf.LastErrorText())
        pdf.DisposePdf()
        json.DisposeJsonObject()
        jsonOut.DisposeJsonObject()
        return
    }

    //  The saving is an estimate: what the old revisions occupied is known exactly, but the writer
    //  decides the final layout.  Measure the written file for the real number.
    fac := chilkat.NewFileAccess()
    fmt.Println("bytesSaved (reported): ", jsonOut.IntOf("bytesSaved"))
    fmt.Println("written file:          ", fac.FileSize("qa_output/grand_canyon_one_revision.pdf"))

    pdf.DisposePdf()
    json.DisposeJsonObject()
    jsonOut.DisposeJsonObject()
    fac.DisposeFileAccess()