Dart Requires Chilkat v11.7.0+

Clipped, Off-Page and White-on-White Text in PDF Extraction

See more PDF Text Extraction Examples

Demonstrates the "clippedText", "offPageText" and "obscuredText" filters. Text that a reader never sees - hidden by a clipping path, outside the crop box, or drawn in the same color as the box beneath it - is excluded by default, and the quality report notes what was skipped. Each kind can be included. 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 is available at hidden_text.pdf

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

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

  // The page has a visible paragraph plus three hidden lines: one drawn outside its clipping
  // rectangle, one below the crop box, and one in white on a white box.
  try {
    pdf.extractText('text', json, jsonOut);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('---- default ----');
  print(jsonOut.stringOf('text'));

  // The quality report says what was left out.
  var i = 0;
  final countI = jsonOut.sizeOfArray('quality.pages[0].issues');
  while (i < countI) {
    jsonOut.i = i;
    print('issue: ${jsonOut.stringOf('quality.pages[0].issues[i].code')}');
    i++;
  }

  // Include everything.
  json.updateString('clippedText', 'include');
  json.updateString('offPageText', 'include');
  json.updateString('obscuredText', 'include');
  try {
    pdf.extractText('text', json, jsonOut);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('---- clippedText, offPageText, obscuredText: include ----');
  print(jsonOut.stringOf('text'));

  // Sample output:

  // ---- default ----
  // Visible Text
  // 
  // This paragraph is visible. The page also carries three kinds of text a reader never sees.
  // 
  // End of the visible text.
  // issue: obscuredTextSkipped
  // issue: clippedTextSkipped
  // ---- clippedText, offPageText, obscuredText: include ----
  // Visible Text
  // 
  // This paragraph is visible. The page also carries three kinds of text a reader never sees.
  // 
  // CLIPPED: this line is drawn outside its clipping rectangle.
  // 
  // OBSCURED: this line is white on a white box.
  // 
  // End of the visible text.
  // 
  // OFFPAGE: this line sits below the crop box.
}