1. GroupDocs Documentation
  2. /
  3. GroupDocs.Parser Product Family
  4. /
  5. GroupDocs.Parser for Node.js
  6. /
  7. Developer Guide
  8. /
  9. Advanced Usage
  10. /
  11. Using OCR to extract a text from images and PDFs
  12. /
  13. OCR Usage Basics

OCR Usage Basics

On this page

GroupDocs.Parser doesn’t contain OCR functionality as a part of its distributable. Instead, an API for integrating any paid or free OCR solution is provided. See Use OCR Connector for details how to create an OCR connector.

The examples below use the com.example.AsposeOcrOnPremise connector from that article. It is a Java class which uses Aspose.OCR for Java, so the connector JAR and the Aspose.OCR JARs must be added to the classpath before the first call to the package:

const path = require('path');
const java = require('java');
// Add the OCR connector and the OCR engine to the classpath before the JVM starts
java.classpath.push(path.join(__dirname, 'ocr-connector.jar'));
java.classpath.push(path.join(__dirname, 'aspose-ocr-22.11.jar'));
java.classpath.push(path.join(__dirname, 'onnxruntime-1.11.0.jar'));
const groupdocs = require('@groupdocs/groupdocs.parser');

To use OCR functionality, the Parser object must be properly initialized:

  • Create an instance of the ParserSettings class with the instance of the OCR connector;
  • Create an instance of the Parser class with the ParserSettings object.
const AsposeOcrOnPremise = java.import('com.example.AsposeOcrOnPremise');

// Create an instance of ParserSettings class with OCR Connector
const settings = new groupdocs.ParserSettings(new AsposeOcrOnPremise());
// Create an instance of Parser class with settings
const parser = new groupdocs.Parser('SampleScan.jpg', settings);

The getText(TextOptions) and getTextAreas(PageTextAreaOptions) methods of the Parser class are used to recognize a text.

Extract a text

To extract a text from non-text PDF documents the getText method is used:

  • Create an instance of the ParserSettings class with the instance of the OCR connector;
  • Create an instance of the Parser class with the ParserSettings object;
  • Create an instance of the TextOptions class with useOcr = true (the second parameter);
  • Call the getText(TextOptions) method and obtain the TextReader object;
  • Check if the reader isn’t null (text extraction is supported for the document);
  • Read a text from the reader.

The following example shows how to extract a text from a scanned PDF document:

const path = require('path');
const java = require('java');
java.classpath.push(path.join(__dirname, 'ocr-connector.jar'));
java.classpath.push(path.join(__dirname, 'aspose-ocr-22.11.jar'));
java.classpath.push(path.join(__dirname, 'onnxruntime-1.11.0.jar'));
const groupdocs = require('@groupdocs/groupdocs.parser');

const AsposeOcrOnPremise = java.import('com.example.AsposeOcrOnPremise');

// Create an instance of ParserSettings class with OCR Connector
const settings = new groupdocs.ParserSettings(new AsposeOcrOnPremise());
// Create an instance of Parser class with settings
const parser = new groupdocs.Parser('scan.pdf', settings);
try {
  // Create an instance of TextOptions to use OCR
  const options = new groupdocs.TextOptions(false, true);
  // Extract a text using OCR
  const reader = parser.getText(options);
  if (reader === null) {
    console.log("Text extraction isn't supported");
  } else {
    try {
      // Print a text
      console.log(reader.readToEnd());
    } finally {
      reader.close();
    }
  }
} finally {
  parser.close();
}
process.exit(0);
Warning
In version 26.9 reading the OCR text of an image file (for example, SampleScan.jpg) with getText(TextOptions) fails with java.lang.IllegalArgumentException: pageIndex after the image is recognized. The same happens in GroupDocs.Parser for Java 26.9. Scanned PDF documents are not affected. To recognize a text of an image file, use getTextAreas as shown below.

Extract text areas

To extract text areas from image files or non-text PDF documents the getTextAreas method is used:

  • Create an instance of the ParserSettings class with the instance of the OCR connector;
  • Create an instance of the Parser class with the ParserSettings object;
  • Create an instance of the PageTextAreaOptions class with useOcr = true;
  • Call the getTextAreas(PageTextAreaOptions) method and obtain the collection of PageTextArea objects;
  • Check if the collection isn’t null (text areas extraction is supported for the document);
  • Iterate through the collection and get rectangles and texts.

The following example shows how to extract text areas from the image file:

const path = require('path');
const java = require('java');
java.classpath.push(path.join(__dirname, 'ocr-connector.jar'));
java.classpath.push(path.join(__dirname, 'aspose-ocr-22.11.jar'));
java.classpath.push(path.join(__dirname, 'onnxruntime-1.11.0.jar'));
const groupdocs = require('@groupdocs/groupdocs.parser');

const AsposeOcrOnPremise = java.import('com.example.AsposeOcrOnPremise');

// Create an instance of ParserSettings class with OCR Connector
const settings = new groupdocs.ParserSettings(new AsposeOcrOnPremise());
// Create an instance of Parser class with settings
const parser = new groupdocs.Parser('SampleScan.jpg', settings);
try {
  // Create an instance of PageTextAreaOptions to use OCR
  const options = new groupdocs.PageTextAreaOptions(true);
  // Extract text areas
  const areas = parser.getTextAreas(options);
  // Check if text areas extraction is supported
  if (areas === null) {
    console.log("Text areas extraction isn't supported");
  } else {
    // Iterate over text areas
    const it = areas.iterator();
    while (it.hasNext()) {
      const a = it.next();
      // Print a text, position and size for an each text area
      console.log(a.getText());
      console.log(`\tPosition: (${a.getRectangle().getLeft()}; ${a.getRectangle().getTop()})`);
      console.log(`\tSize: (${a.getRectangle().getSize().getWidth()}; ${a.getRectangle().getSize().getHeight()})`);
    }
  }
} finally {
  parser.close();
}
process.exit(0);

The beginning of the output for SampleScan.jpg:

Lorem

	Position: (30; 15)
	Size: (123; 39)
Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Maecenas porttitor congue massa. Fusce posuere,
magna sed pulvinar ultricies, purus lectus malesuada libero, sit amet commodo magna eros quis urna.

	Position: (24; 59)
	Size: (1234; 80)

OCR options

The TextOptions and PageTextAreaOptions classes accept an OcrOptions object. The OcrOptions class has the following members:

MemberDescription
getRectangle(), setRectangle(Rectangle)A rectangular area which restricts the area of the text recognition.
getHandler(), setHandler(OcrEventHandler)An instance of the OcrEventHandler class to handle warnings which occur while the text recognition.

The OCR connector receives these options and must apply them. The following sections describe how to use them.

How to restrict the area of the text recognition

To restrict an area of the image for the text recognition, set the rectangle in the OcrOptions constructor.

The following example shows how to restrict the text recognition by the rectangular area:

const path = require('path');
const java = require('java');
java.classpath.push(path.join(__dirname, 'ocr-connector.jar'));
java.classpath.push(path.join(__dirname, 'aspose-ocr-22.11.jar'));
java.classpath.push(path.join(__dirname, 'onnxruntime-1.11.0.jar'));
const groupdocs = require('@groupdocs/groupdocs.parser');

const AsposeOcrOnPremise = java.import('com.example.AsposeOcrOnPremise');

// Create an instance of ParserSettings class with OCR Connector
const settings = new groupdocs.ParserSettings(new AsposeOcrOnPremise());
// Create an instance of Parser class with settings
const parser = new groupdocs.Parser('scan.pdf', settings);
try {
  // Create an instance of OcrOptions to set a rectangle
  const ocrOptions = new groupdocs.OcrOptions(new groupdocs.Rectangle(0, 0, 400, 200));
  // Create an instance of TextOptions to use OCR
  const options = new groupdocs.TextOptions(false, true, ocrOptions);
  // Extract a text using OCR
  const reader = parser.getText(options);
  if (reader === null) {
    console.log("Text extraction isn't supported");
  } else {
    try {
      console.log(reader.readToEnd());
    } finally {
      reader.close();
    }
  }
} finally {
  parser.close();
}
process.exit(0);

How to handle warnings

To handle warning messages, pass an OcrEventHandler object to the OcrOptions constructor. The hasWarnings method of the OcrEventHandler class indicates if any warnings occur. Use the getWarnings() method to get all warnings or the getWarnings(int) method to get warnings for the page. An empty list is returned if no warning occurs during the text recognition.

The following example shows how to handle warning messages:

const path = require('path');
const java = require('java');
java.classpath.push(path.join(__dirname, 'ocr-connector.jar'));
java.classpath.push(path.join(__dirname, 'aspose-ocr-22.11.jar'));
java.classpath.push(path.join(__dirname, 'onnxruntime-1.11.0.jar'));
const groupdocs = require('@groupdocs/groupdocs.parser');

const AsposeOcrOnPremise = java.import('com.example.AsposeOcrOnPremise');

// Create an instance of ParserSettings class with OCR Connector
const settings = new groupdocs.ParserSettings(new AsposeOcrOnPremise());
// Create an instance of Parser class with settings
const parser = new groupdocs.Parser('scan.pdf', settings);
try {
  // Create an instance of OcrEventHandler to handle warnings
  const handler = new groupdocs.OcrEventHandler();
  // Create an instance of OcrOptions to set a handler
  const ocrOptions = new groupdocs.OcrOptions(null, handler);
  // Create an instance of TextOptions to use OCR
  const options = new groupdocs.TextOptions(false, true, ocrOptions);
  // Extract a text using OCR
  const reader = parser.getText(options);
  if (reader === null) {
    console.log("Text extraction isn't supported");
  } else {
    try {
      console.log(reader.readToEnd());
    } finally {
      reader.close();
    }
  }
  if (handler.hasWarnings()) {
    console.log('The following warnings occur while text recognition:');
    const it = handler.getWarnings().iterator();
    while (it.hasNext()) {
      console.log('\t* ' + it.next());
    }
  } else {
    console.log('Text recognition was performed without any warning.');
  }
} finally {
  parser.close();
}
process.exit(0);

More resources

Free online document parser App

Along with the full-featured library we provide simple but powerful free Apps.

You are welcome to parse documents and extract data from PDF, DOC, DOCX, PPT, PPTX, XLS, XLSX, Emails and more with our Free Online Document Parser App.

On this page

Close
Loading

Analyzing your prompt, please hold on...

An error occurred while retrieving the results. Please refresh the page and try again.

© Groupdocs 2001-2026. All Rights Reserved.