Xojo Plugin 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. Xojo Plugin

Dim success As Boolean
success = False

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

Dim fmt As New Chilkat.Formats
Dim json As New Chilkat.JsonObject
Dim jsonOut As New Chilkat.JsonObject
success = json.UpdateString("payload.text","https://www.chilkatsoft.com/barcode_overview.asp")

//  Encode the same text at each level.
Dim levels As New Chilkat.JsonArray
success = levels.Load("[""L"",""M"",""Q"",""H""]")
Dim i As Int32
For i = 0 To 3
    success = json.UpdateString("encoding.qr.errorCorrection",levels.StringAt(i))
    success = fmt.QrCode("generate",json,jsonOut)
    If (success = False) Then
        System.DebugLog(fmt.LastErrorText)
        Return
    End If

    System.DebugLog("level " + levels.StringAt(i) + ": version " + Str(jsonOut.IntOf("symbols[0].selectedEncoding.version")) + ", " + Str(jsonOut.IntOf("symbols[0].dimensions.modulesWide")) _
         + " modules wide")
Next

//  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.
Dim json2 As New Chilkat.JsonObject
success = json2.UpdateString("payload.text","https://chilkatsoft.com")
success = json2.UpdateString("encoding.qr.errorCorrection","L")
success = fmt.QrCode("generate",json2,jsonOut)
If (success = False) Then
    System.DebugLog(fmt.LastErrorText)
    Return
End If

System.DebugLog("level L requested: version " + Str(jsonOut.IntOf("symbols[0].selectedEncoding.version")) + ", level " + jsonOut.StringOf("symbols[0].selectedEncoding.errorCorrection"))

success = json2.UpdateBool("encoding.qr.boostErrorCorrection",True)
success = fmt.QrCode("generate",json2,jsonOut)
If (success = False) Then
    System.DebugLog(fmt.LastErrorText)
    Return
End If

System.DebugLog("level L with boost: version " + Str(jsonOut.IntOf("symbols[0].selectedEncoding.version")) + ", level " + jsonOut.StringOf("symbols[0].selectedEncoding.errorCorrection"))

//  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