React Native 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. React Native

import { Formats, JsonArray, JsonObject } from '@chilkat/react-native'

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

  const fmt = new Formats();
  const json = new JsonObject();
  const jsonOut = new JsonObject();
  json.updateString('payload.text', 'https://www.chilkatsoft.com/barcode_overview.asp');

  // Encode the same text at each level.
  const levels = new JsonArray();
  levels.load('["L","M","Q","H"]');
  for (let i = 0; i <= 3; i++) {
    json.updateString('encoding.qr.errorCorrection', levels.stringAt(i));
    try {
      fmt.qrCode('generate', json, jsonOut);
    } catch {
      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.
  const json2 = new JsonObject();
  json2.updateString('payload.text', 'https://chilkatsoft.com');
  json2.updateString('encoding.qr.errorCorrection', 'L');
  try {
    fmt.qrCode('generate', json2, jsonOut);
  } catch {
    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);
  try {
    fmt.qrCode('generate', json2, jsonOut);
  } catch {
    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
}