DataFlex Requires Chilkat v11.7.0+

Optimizing a Signed PDF (PreserveSignatures)

See more PDF Optimization Examples

Demonstrates what happens when a signed PDF is optimized. Optimizing rewrites the document, and a rewrite breaks every existing digital signature, so with PreserveSignatures true (the default) Optimize refuses and LastErrorText says why. Setting PreserveSignatures to false allows it, and the signature that was in the file no longer verifies afterwards. "audit" is always allowed, because it changes nothing. DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoPdf
    Variant vJson
    Handle hoJson
    Variant vJsonOut
    Handle hoJsonOut
    Handle hoPdf2
    Variant vSigInfo
    Handle hoSigInfo
    Boolean iVerified
    String sTemp1
    Integer iTemp1

    Move False To iSuccess

    //  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 invoice_signed.pdf

    Get Create (RefClass(cComChilkatPdf)) To hoPdf
    If (Not(IsComObjectCreated(hoPdf))) Begin
        Send CreateComObject of hoPdf
    End
    Get ComLoadFile Of hoPdf "qa_data/pdf/invoice_signed.pdf" To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoPdf To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get ComNumSignatures Of hoPdf To iTemp1
    Showln "signatures: " iTemp1

    Get Create (RefClass(cComChilkatJsonObject)) To hoJson
    If (Not(IsComObjectCreated(hoJson))) Begin
        Send CreateComObject of hoJson
    End
    Get Create (RefClass(cComChilkatJsonObject)) To hoJsonOut
    If (Not(IsComObjectCreated(hoJsonOut))) Begin
        Send CreateComObject of hoJsonOut
    End

    //  An audit changes nothing, so it is allowed on a signed PDF.
    Get pvComObject of hoJson to vJson
    Get pvComObject of hoJsonOut to vJsonOut
    Get ComOptimize Of hoPdf "audit" vJson vJsonOut To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoPdf To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get ComIntOf Of hoJsonOut "estimatedSavings.total" To iTemp1
    Showln "audit ok, estimated savings: " iTemp1

    //  Optimizing is refused while PreserveSignatures is true.
    Get pvComObject of hoJson to vJson
    Get pvComObject of hoJsonOut to vJsonOut
    Get ComOptimize Of hoPdf "optimize" vJson vJsonOut To iSuccess
    If (iSuccess = False) Begin
        Showln "Refused while PreserveSignatures is true."
    End

    //  Allow the rewrite.  Do this only when the signatures no longer matter -- an invoice being
    //  archived, say, where the signed original is kept elsewhere.
    Set ComPreserveSignatures Of hoPdf To False
    Get pvComObject of hoJson to vJson
    Get pvComObject of hoJsonOut to vJsonOut
    Get ComOptimize Of hoPdf "optimize" vJson vJsonOut To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoPdf To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get ComWriteFile Of hoPdf "qa_output/invoice_optimized.pdf" To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoPdf To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get ComIntOf Of hoJsonOut "bytesSaved" To iTemp1
    Showln "optimized, bytesSaved: " iTemp1

    //  The signature is still in the file, but it no longer verifies: the bytes it covered have changed.
    Get Create (RefClass(cComChilkatPdf)) To hoPdf2
    If (Not(IsComObjectCreated(hoPdf2))) Begin
        Send CreateComObject of hoPdf2
    End
    Get ComLoadFile Of hoPdf2 "qa_output/invoice_optimized.pdf" To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoPdf2 To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get ComNumSignatures Of hoPdf2 To iTemp1
    Showln "signatures after: " iTemp1

    Get Create (RefClass(cComChilkatJsonObject)) To hoSigInfo
    If (Not(IsComObjectCreated(hoSigInfo))) Begin
        Send CreateComObject of hoSigInfo
    End
    Get pvComObject of hoSigInfo to vSigInfo
    Get ComVerifySignature Of hoPdf2 0 vSigInfo To iVerified
    Showln "verifies after optimizing: " iVerified


End_Procedure