JavaScript 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. JavaScript

var success = false;

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

var fmt = new CkFormats();
var json = new CkJsonObject();
var jsonOut = new CkJsonObject();
json.UpdateString("payload.text","https://www.chilkatsoft.com/barcode_overview.asp");

//  Encode the same text at each level.
var levels = new CkJsonArray();
levels.Load("[\"L\",\"M\",\"Q\",\"H\"]");
var i;
for (i = 0; i <= 3; i++) {
    json.UpdateString("encoding.qr.errorCorrection",levels.StringAt(i));
    success = fmt.QrCode("generate",json,jsonOut);
    if (success == false) {
        console.log(fmt.LastErrorText);
        return;
    }

    console.log("level " + levels.StringAt(i) + ": version " + jsonOut.IntOf("symbols[0].selectedEncoding.version") + ", " + jsonOut.IntOf("symbols[0].dimensions.modulesWide")
         + " 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.
var json2 = new CkJsonObject();
json2.UpdateString("payload.text","https://chilkatsoft.com");
json2.UpdateString("encoding.qr.errorCorrection","L");
success = fmt.QrCode("generate",json2,jsonOut);
if (success == false) {
    console.log(fmt.LastErrorText);
    return;
}

console.log("level L requested: version " + jsonOut.IntOf("symbols[0].selectedEncoding.version") + ", level " + jsonOut.StringOf("symbols[0].selectedEncoding.errorCorrection"));

json2.UpdateBool("encoding.qr.boostErrorCorrection",true);
success = fmt.QrCode("generate",json2,jsonOut);
if (success == false) {
    console.log(fmt.LastErrorText);
    return;
}

console.log("level L with boost: version " + 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