OCR C# Open Source (List For Developers)

OCR (Optical Character Recognition) is a game-changing technology that completely transforms how scanned documents can be used in today's digital world. It enables computers to recognize and extract text from a variety of sources, including scanned PDF documents, allowing us to effectively edit and interact with PDF documents. One of the optical character recognition (OCR) programs is Adobe Acrobat, which allows you to swiftly extract text from scanned documents and convert them into editable PDFs and searchable picture PDFs.

Developers can access robust tools and APIs that make use of cutting-edge algorithms and machine learning approaches by utilizing OCR libraries like Tesseract and IronOCR. These libraries enable accurate text recognition, making it simpler to manage and retrieve useful information from both previously scanned documents and brand-new documents. OCR enables seamless content analysis and helps businesses and individuals maximize their productivity by making the most of their scanned documents and page images. OCR is a vital tool in current technology, whether it's used to digitize paper-based records, extract data from invoices, or simply enhance document accessibility.


The most renowned open-source OCR engine is called Tesseract, and it was initially created by Hewlett-Packard. Since 2006, Google has been supporting this free software project, which is released under the Apache license.

One of the most accurate open-source and free systems available is the Tesseract OCR engine. Tesseract now supports 116 languages with its most recent stable version, 4.1.1, which is based on LSTM.

Tesseract requires support from a separate GUI (graphical user interface) when running from a command-line interface because it does not have its own built-in interface. It can learn new information using its neural networks and has an advanced image preprocessing pipeline. The most effective technique to add OCR capabilities to your .NET application is the Tesseract .NET SDK, which is one of the best solutions for providing text recognition capabilities. Even though Tesseract is undoubtedly the best OCR library currently on the market.


The GNU Public License was used to create the OCR (Optical Character Recognition) program known as GOCR. It transforms text files back into scanned images of documents. After starting the program and managing the development team on SF, Joerg Schulenburg continues to handle the package at a (very) low time base today.

Since GOCR can be used with several front-ends, it is relatively simple to port it to other operating systems, network applications, and architectures. It can read a wide range of picture file types, and until 2010, its quality consistently improved.

According to GOCR, it can handle single-column sans-serif fonts with a height of 20–60 pixels. It reports difficulties with text written in alphabets other than Latin, serif fonts, overlapping letters, handwritten text, various typefaces, noisy photos, and excessive angles of skew. GOCR is also capable of translating barcodes.


CuneiForm, a free and open-source technology, is now also known as "Cognitive OpenOCR." It has built-in output and a database. It covers 23 distinct languages and also performs tasks such as text format scanning, document layout analysis, and identification.

Cognitive Technologies developed the licenses for OpenOCR, which are freeware and BSD. While it supports cross-platform use, Linux users are not provided with a graphical interface.

To simplify character recognition work in any Dot NET Framework 2.0 or later applications, the wrapper library Puma Dot NET is used. It runs a dictionary check while processing data to enhance the quality of recognition.

CuneiForm is a technology designed to automatically or semi-automatically convert electronic copies of paper documents and image files into an editable form without affecting the structure and original document fonts. The system consists of two parts for processing electronic documents in batches and one document at a time. Furthermore, the system supports a combination of Russian and English. Only the branch created by Andrei Borovsky in 2009 supports the recognition of other hybrid languages. Teaching the system to recognize other languages is challenging since each language is associated with a dat-file, the structure and creation process of which are not disclosed by the developers.


Kraken was developed to address the issues with Ocropus without impacting its other features. It utilizes its CLSTM neural network library and leverages the valuable experience gained from prior projects with fresh data. It requires the use of certain external libraries to function effectively across different platforms. With the help of the stored information, it can make more accurate predictions regarding potential data validation problems. Furthermore, its working methodology facilitates the easy deployment and training of new models.


A9T9 is a free OCR software that can be used to extract text from picture files and convert images and PDF documents. It provides a graphical user interface (GUI) for the Tesseract OCR engine.

The program is easy to set up. Most importantly, it is completely free and open-source. It has no spyware and adware.

You can open a PDF file or an image, and the contents of the source file will be displayed in the left window. If your document has multiple pages or is a multipage document, you can use the arrows at the bottom of the page to navigate between pages.

To initiate the OCR process, simply click the green OCR button, and the output will appear in the second right pane. You have the option to save the output text as both text files and Word documents.


In contrast to the standard Tesseract library, IronOCR expands Tesseract and provides a native C# OCR library with higher accuracy, improved performance, and enhanced stability. IronOCR can be used in .NET programs and websites to extract text from PDFs and images. It supports a wide range of foreign languages and can generate plain text or structured data output. It is capable of scanning barcodes and images with embedded text. The library can be utilized in applications developed in .NET for the console, web, MVC, and desktop. The development team offers direct assistance with the licensing process for commercial deployments. IronOCR is compatible with the latest versions of Visual Studio.

Advantage of IronOCR

  • Using the latest Tesseract 5 engine, IronOCR is capable of reading paper documents, barcodes, and QR codes from various picture or PDF files. This package simplifies the incorporation of OCR into desktop, console, and web applications.
  • IronOCR enables us to perform OCR, which allows us to convert scanned PDFs into searchable PDFs.
  • In addition to word lists and custom languages, IronOCR supports 127 different languages worldwide.
  • IronOCR can scan over 20 different types of barcodes and QR codes.
  • IronOCR can provide output in plain text as well as barcode data. Developers can retrieve all content for direct entry into a system using an alternative structured data object paradigm. This includes structured headings, paragraphs, lines, words, and characters in web applications.

Below is the sample code that we will use to recognize the text content from the given image and convert it into text.

var Ocr = new IronTesseract();   
Ocr.Language = OcrLanguage.EnglishBest;
Ocr.Configuration.TesseractVersion = TesseractVersion.Tesseract5;
using (var Input = new OcrInput())      
    var R = Ocr.Read(Input);       
var Ocr = new IronTesseract();   
Ocr.Language = OcrLanguage.EnglishBest;
Ocr.Configuration.TesseractVersion = TesseractVersion.Tesseract5;
using (var Input = new OcrInput())      
    var R = Ocr.Read(Input);       
Dim Ocr = New IronTesseract()
Ocr.Language = OcrLanguage.EnglishBest
Ocr.Configuration.TesseractVersion = TesseractVersion.Tesseract5
Using Input = New OcrInput()
	Dim R = Ocr.Read(Input)
End Using
VB   C#

In the code snippet above, we are developing a feature using IronTesseract. First, we instantiate a new OcrInput object to enable the addition of one or more image files. When using the Add method of the OcrInput object, we may need to specify the image's path within the code. You can add as many images as desired. By parsing the image documents and extracting the results into the OCR result, we can utilize the Read functionality on the object that we previously created to access the images. It has the capability to extract text from images and convert it into a string.

The output below shows the text extracted from the previously provided image, demonstrating that the text was successfully extracted from the image.

OCR C# Open Source (List For Developers) Figure 1 - Output

See this post for a thorough IronOCR instruction.


OCR open-source tools allow us to build our own programs using their source code. However, some tools do not have an official library or dedicated team to provide support in case of coding issues. Tesseract's documentation also lacks sample code or tutorials for common use scenarios, making it challenging for beginners to understand the code and libraries.

IronOCR supports various .NET projects such as .NET Framework Standard 2, .NET Framework 4.5, and .NET Core 2, 3, and 5. It also works with newer technologies like Mono, Xamarin, and Azure. By leveraging IronOCR technologies, we can enhance Tesseract's results and correct inaccurately scanned documents or images. The complex Tesseract dictionary system is managed through the NuGet Package. We utilize the Iron OCR Library to develop an OCR tool.

With IronOCR, we can use the program without any additional configuration, and it supports PDF files, multi-frame TIFF, and all common image formats. It also offers barcode recognition capabilities, allowing us to extract barcode data and read barcode values from images. IronOCR provides a cost-effective development edition with a free trial, and the lifetime license is included in the IronOCR bundle at no extra cost. The IronOCR bundle provides coverage for multiple platforms with a single payment. For more information on IronOCR's pricing, please refer to this page.