DataFlex Requires Chilkat v11.7.0+

QR Code Error Correction Levels

See more QR Code Examples

Demonstrates the four QR error-correction levels. L, M, Q and H allow a reader to recover the data when about 7%, 15%, 25% and 30% of the symbol is damaged or covered. More error correction leaves less room for data, so the same text needs a larger symbol at a higher level. The default is M. The example also shows boostErrorCorrection, which raises the level for free when the chosen version has room to spare. DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoFmt
    Variant vJson
    Handle hoJson
    Variant vJsonOut
    Handle hoJsonOut
    Handle hoLevels
    Integer i
    Variant vJson2
    Handle hoJson2
    String sTemp1
    Integer iTemp1
    Integer iTemp2

    Move False To iSuccess

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

    Get Create (RefClass(cComChilkatFormats)) To hoFmt
    If (Not(IsComObjectCreated(hoFmt))) Begin
        Send CreateComObject of hoFmt
    End
    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
    Get ComUpdateString Of hoJson "payload.text" "https://www.chilkatsoft.com/barcode_overview.asp" To iSuccess

    //  Encode the same text at each level.
    Get Create (RefClass(cComChilkatJsonArray)) To hoLevels
    If (Not(IsComObjectCreated(hoLevels))) Begin
        Send CreateComObject of hoLevels
    End
    Get ComLoad Of hoLevels '["L","M","Q","H"]' To iSuccess

    For i From 0 To 3
        Get ComStringAt Of hoLevels i To sTemp1
        Get ComUpdateString Of hoJson "encoding.qr.errorCorrection" sTemp1 To iSuccess
        Get pvComObject of hoJson to vJson
        Get pvComObject of hoJsonOut to vJsonOut
        Get ComQrCode Of hoFmt "generate" vJson vJsonOut To iSuccess
        If (iSuccess = False) Begin
            Get ComLastErrorText Of hoFmt To sTemp1
            Showln sTemp1
            Procedure_Return
        End

        Get ComStringAt Of hoLevels i To sTemp1
        Get ComIntOf Of hoJsonOut "symbols[0].selectedEncoding.version" To iTemp1
        Get ComIntOf Of hoJsonOut "symbols[0].dimensions.modulesWide" To iTemp2
        Showln "level " sTemp1 ": version " iTemp1 ", " iTemp2 " modules wide"
    Loop

    //  The four symbols.  They hold the same text, and the higher the level, the larger the symbol:

    //  

    //  A symbol often has room left over.  boostErrorCorrection uses it: the level is raised
    //  as far as the same version allows, so the symbol is no larger but is more robust.
    Get Create (RefClass(cComChilkatJsonObject)) To hoJson2
    If (Not(IsComObjectCreated(hoJson2))) Begin
        Send CreateComObject of hoJson2
    End
    Get ComUpdateString Of hoJson2 "payload.text" "https://chilkatsoft.com" To iSuccess
    Get ComUpdateString Of hoJson2 "encoding.qr.errorCorrection" "L" To iSuccess
    Get pvComObject of hoJson2 to vJson2
    Get pvComObject of hoJsonOut to vJsonOut
    Get ComQrCode Of hoFmt "generate" vJson2 vJsonOut To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoFmt To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get ComIntOf Of hoJsonOut "symbols[0].selectedEncoding.version" To iTemp1
    Get ComStringOf Of hoJsonOut "symbols[0].selectedEncoding.errorCorrection" To sTemp1
    Showln "level L requested: version " iTemp1 ", level " sTemp1

    Get ComUpdateBool Of hoJson2 "encoding.qr.boostErrorCorrection" True To iSuccess
    Get pvComObject of hoJson2 to vJson2
    Get pvComObject of hoJsonOut to vJsonOut
    Get ComQrCode Of hoFmt "generate" vJson2 vJsonOut To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoFmt To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get ComIntOf Of hoJsonOut "symbols[0].selectedEncoding.version" To iTemp1
    Get ComStringOf Of hoJsonOut "symbols[0].selectedEncoding.errorCorrection" To sTemp1
    Showln "level L with boost: version " iTemp1 ", level " sTemp1

    //  Level L, and level M reached by the boost.  The two symbols are the same size:

    //  

    //  Sample output:

    //  level L: version 3, 29 modules wide
    //  level M: version 4, 33 modules wide
    //  level Q: version 5, 37 modules wide
    //  level H: version 6, 41 modules wide
    //  level L requested: version 2, level L
    //  level L with boost: version 2, level M


End_Procedure