Swift 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. Swift

func chilkatTest() {
    var success: Bool = false

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

    let fmt = CkoFormats()!
    let json = CkoJsonObject()!
    let jsonOut = CkoJsonObject()!
    json.updateString(jsonPath: "payload.text", value: "https://www.chilkatsoft.com/barcode_overview.asp")

    //  Encode the same text at each level.
    let levels = CkoJsonArray()!
    levels.load(jsonArray: "[\"L\",\"M\",\"Q\",\"H\"]")
    var i: Int
    for i = 0; i <= 3; i++ {
        json.updateString(jsonPath: "encoding.qr.errorCorrection", value: levels.string(at: i))
        success = fmt.qrCode(op: "generate", jsonIn: json, jsonOut: jsonOut)
        if success == false {
            print("\(fmt.lastErrorText!)")
            return
        }

        print("level \(levels.string(at: i)!): version \(jsonOut.int(of: "symbols[0].selectedEncoding.version").intValue), \(jsonOut.int(of: "symbols[0].dimensions.modulesWide").intValue) modules wide")
    }

    //  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.
    let json2 = CkoJsonObject()!
    json2.updateString(jsonPath: "payload.text", value: "https://chilkatsoft.com")
    json2.updateString(jsonPath: "encoding.qr.errorCorrection", value: "L")
    success = fmt.qrCode(op: "generate", jsonIn: json2, jsonOut: jsonOut)
    if success == false {
        print("\(fmt.lastErrorText!)")
        return
    }

    print("level L requested: version \(jsonOut.int(of: "symbols[0].selectedEncoding.version").intValue), level \(jsonOut.string(of: "symbols[0].selectedEncoding.errorCorrection")!)")

    json2.updateBool(jsonPath: "encoding.qr.boostErrorCorrection", value: true)
    success = fmt.qrCode(op: "generate", jsonIn: json2, jsonOut: jsonOut)
    if success == false {
        print("\(fmt.lastErrorText!)")
        return
    }

    print("level L with boost: version \(jsonOut.int(of: "symbols[0].selectedEncoding.version").intValue), level \(jsonOut.string(of: "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

}