Dart Requires Chilkat v11.7.0+

Get Every Occurrence of a Label in a PDF

See more PDF Text Extraction Examples

Demonstrates the "labelOccurrence" option. When the same label appears more than once (for example "Total:" on each of several receipts), "first" (the default) uses the first occurrence, "all" returns every occurrence with its page, and a number selects one occurrence. 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.

  // The PDF used in this example (three receipts, one per page) is available at three_receipts.pdf

  final pdf = CkPdf();
  try {
    pdf.loadFile('qa_data/pdf/three_receipts.pdf');
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  final json = CkJsonObject();
  final jsonOut = CkJsonObject();

  // Each of the three pages is a receipt with a "Total:" line.
  json.updateString('label', 'Total');
  json.updateString('labelValue', 'right');

  // By default only the first occurrence (in reading order) is used.
  try {
    pdf.extractText('text', json, jsonOut);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('First total: ${jsonOut.stringOf('text')}');

  // labelOccurrence "all" returns every occurrence.  The "text" member holds the values joined
  // by line breaks, and labelMatches has one entry per occurrence with its page.
  json.updateString('labelOccurrence', 'all');
  try {
    pdf.extractText('text', json, jsonOut);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  var i = 0;
  final countI = jsonOut.sizeOfArray('labelMatches');
  while (i < countI) {
    jsonOut.i = i;
    print('Page ${jsonOut.intOf('labelMatches[i].page')} total: ${jsonOut.stringOf('labelMatches[i].text')}');
    i++;
  }

  // A number selects one occurrence: 2 is the second.
  json.updateInt('labelOccurrence', 2);
  try {
    pdf.extractText('text', json, jsonOut);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('Second total: ${jsonOut.stringOf('text')}');

  // The occurrences are counted over the selected pages, so combining "pages" with the label
  // is another way to pick one receipt:
  json.updateString('labelOccurrence', 'first');
  json.updateString('pages', '3');
  json.updateString('label', 'Receipt No.');
  try {
    pdf.extractText('text', json, jsonOut);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('Receipt number on page 3: ${jsonOut.stringOf('text')}');

  // Sample output:

  // First total: $19.86
  // Page 1 total: $19.86
  // Page 2 total: $17.34
  // Page 3 total: $23.62
  // Second total: $17.34
  // Receipt number on page 3: 1003
}