Dart Requires Chilkat v11.7.0+

Get the Modules of a QR Code (Bit Matrix)

See more QR Code Examples

Demonstrates getting the QR code itself, as a grid of dark and light modules, to draw with something other than the built-in PNG and SVG output: on a canvas, in a PDF, on a display, or with a label printer language. With output.includeModuleData the response has symbols[0].moduleData, a bit matrix with one bit per module, each row starting on a new byte, most significant bit first, 1 for dark. The quiet zone is not part of the matrix. The example prints the symbol using two characters per module. Dart

import 'package:chilkat/chilkat.dart';

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

  final json = CkJsonObject();
  json.updateString('payload.text', 'CHILKAT');
  json.updateBool('output.includeModuleData', true);

  final fmt = CkFormats();
  final jsonOut = CkJsonObject();
  try {
    fmt.qrCode('generate', json, jsonOut);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final width = jsonOut.intOf('symbols[0].moduleData.width');
  final height = jsonOut.intOf('symbols[0].moduleData.height');
  final rowBytes = jsonOut.intOf('symbols[0].moduleData.rowBytes');
  print('kind: ${jsonOut.stringOf('symbols[0].moduleData.kind')}');
  print('modules: $width x $height, $rowBytes bytes per row');

  // The matrix is height rows of rowBytes bytes.
  final bd = CkBinData();
  try {
    bd.appendEncoded(jsonOut.stringOf('symbols[0].moduleData.bytesBase64'), 'base64');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final sbRow = CkStringBuilder();
  var b = 0;
  var mask = 128;
  for (var row = 0; row < height; row++) {
    sbRow.clear();
    for (var col = 0; col < width; col++) {
      // The module at (col,row) is a bit of the byte at (row * rowBytes) + (col / 8).
      // The leftmost module of each byte is its most significant bit.
      if ((col % 8) == 0) {
        mask = 128;
      }

      b = bd.getByte((row * rowBytes) + (col ~/ 8));
      if (((b ~/ mask) % 2) == 1) {
        sbRow.append('##');
      } else {
        sbRow.append('  ');
      }

      mask = mask ~/ 2;
    }

    print(sbRow.getAsString());
  }

  // The same symbol as the PNG that the call also returned:

  // 

  // Sample output:

  // kind: bitMatrix
  // modules: 21 x 21, 3 bytes per row
  // ##############              ##############
  // ##          ##      ####    ##          ##
  // ##  ######  ##  ##  ####    ##  ######  ##
  // ##  ######  ##  ##          ##  ######  ##
  // ##  ######  ##  ##  ##  ##  ##  ######  ##
  // ##          ##  ####  ##    ##          ##
  // ##############  ##  ##  ##  ##############
  //                 ####
  // ##  ##########      ####    ##########
  //     ####          ##  ########    ######
  // ####  ########    ####  ##  ####      ####
  //       ##  ##      ############    ####  ##
  //   ######  ####  ######  ##    ##  ##
  //                 ##  ##  ##    ##  ##    ##
  // ##############        ##  ##    ##      ##
  // ##          ##  ##  ##        ######  ####
  // ##  ######  ##  ####  ##  ##    ##
  // ##  ######  ##  ##  ############    ##
  // ##  ######  ##  ##      ##  ####  ##
  // ##          ##    ##  ########          ##
  // ##############  ##      ##      ######
}