Xbase++ 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. Xbase++

LOCAL nSuccess
LOCAL oFmt
LOCAL oJson
LOCAL oJsonOut
LOCAL oLevels
LOCAL i
LOCAL oJson2

nSuccess := 0

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

oFmt := CreateObject("Chilkat.Formats")
oJson := CreateObject("Chilkat.JsonObject")
oJsonOut := CreateObject("Chilkat.JsonObject")
oJson:UpdateString("payload.text", "https://www.chilkatsoft.com/barcode_overview.asp")

//  Encode the same text at each level.
oLevels := CreateObject("Chilkat.JsonArray")
oLevels:Load('["L","M","Q","H"]')

FOR i := 0 TO 3
    oJson:UpdateString("encoding.qr.errorCorrection", oLevels:StringAt(i))
    nSuccess := oFmt:QrCode("generate", oJson, oJsonOut)
    IF (nSuccess == 0)
        ? oFmt:LastErrorText
        oFmt:destroy()
        oJson:destroy()
        oJsonOut:destroy()
        oLevels:destroy()
        RETURN
    ENDIF

    ? "level " + oLevels:StringAt(i) + ": version " + Str(oJsonOut:IntOf("symbols[0].selectedEncoding.version")) + ", " + Str(oJsonOut: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.
oJson2 := CreateObject("Chilkat.JsonObject")
oJson2:UpdateString("payload.text", "https://chilkatsoft.com")
oJson2:UpdateString("encoding.qr.errorCorrection", "L")
nSuccess := oFmt:QrCode("generate", oJson2, oJsonOut)
IF (nSuccess == 0)
    ? oFmt:LastErrorText
    oFmt:destroy()
    oJson:destroy()
    oJsonOut:destroy()
    oLevels:destroy()
    oJson2:destroy()
    RETURN
ENDIF

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

oJson2:UpdateBool("encoding.qr.boostErrorCorrection", 1)
nSuccess := oFmt:QrCode("generate", oJson2, oJsonOut)
IF (nSuccess == 0)
    ? oFmt:LastErrorText
    oFmt:destroy()
    oJson:destroy()
    oJsonOut:destroy()
    oLevels:destroy()
    oJson2:destroy()
    RETURN
ENDIF

? "level L with boost: version " + Str(oJsonOut:IntOf("symbols[0].selectedEncoding.version")) + ", level " + oJsonOut: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

oFmt:destroy()
oJson:destroy()
oJsonOut:destroy()
oLevels:destroy()
oJson2:destroy()