Convert Images to Searchable PDF with OCR - Console C#

This tutorial shows how to create a C# Windows Console application that sets up the LEAD OCR Engine to process OCR.

Summary This tutorial covers how to set up the LEAD OCR Engine in a C# Windows Console application.
Completion Time 30 minutes
Visual Studio Project Download tutorial project (2 KB)
Platform C# Windows Console Application
IDE Visual Studio 2017, 2019
Development License Download LEADTOOLS
Try it in another language

Required Knowledge

Get familiar with the basic steps of creating a project by reviewing the Add References and Set a License tutorial, before working on the Convert Images to Searchable PDF With OCR - Console C# tutorial.

Create the Project and Add LEADTOOLS References

In Visual Studio, create a new C# Windows Console project, and add the following necessary LEADTOOLS references.

The references needed depend upon the purpose of the project. References can be added by one or the other of the following two methods (but not both). For this project, the following references are needed:

If using NuGet references, this tutorial requires the following NuGet package:

If local DLL references are used, the following DLLs are needed. The DLLs are located at <INSTALL_DIR>\LEADTOOLS21\Bin\Dotnet4\x64:

For a complete list of which Codec DLLs are required for specific formats, refer to File Format Support.

Set the License File

The License unlocks the features needed for the project. It must be set before any toolkit function is called. For details including tutorials for different platforms, refer to Setting a Runtime License.

There are two types of runtime licenses:


Adding LEADTOOLS NuGet and local references and setting a license are covered in more detail in the Add References and Set a License tutorial.

Add the OCR Code

With the project created, the references added, and the license set, coding can begin.

In Solution Explorer, open Program.cs. To initialize and run the OCR Engine, add a new OCR(string inputFile, string outputFile) method and call it inside the Main method.

Add the following statements to the using block at the top of Program.cs:

// Using block at the top 
using System; 
using System.IO; 
using Leadtools; 
using Leadtools.Document.Writer; 
using Leadtools.Ocr; 
static void OCR(string inputFile, string outputFile) 
    using (IOcrEngine ocrEngine = OcrEngineManager.CreateEngine(OcrEngineType.LEAD)) 
        //Startup the LEADTOOLS OCR Engine 
        ocrEngine.Startup(null, null, null, null); 
        //Run the AutoRecognizeManager and specify PDF format 
        ocrEngine.AutoRecognizeManager.Run(inputFile, outputFile, DocumentFormat.Pdf, null, null); 
        Console.WriteLine($"OCR output saved to {outputFile}"); 
static void Main(string[] args) 
    string input = @"C:\LEADTOOLS21\Resources\Images\OCR1.TIF"; 
    string output = @"C:\LEADTOOLS21\Resources\Images\OCR1.PDF"; 
    OCR(input, output); 

Run the Project

Run the project by pressing F5, or by selecting Debug -> Start Debugging.

If the steps were followed correctly, the console appears and confirms that the license was set correctly. Then the application converts the OCR1.TIF image to PDF format and saves it to the specified location (as a searchable PDF).


This tutorial showed how to create a simple console-based OCR application that initializes the LEAD OCR Engine, takes a specified input file and outputs the recognition results to the specified output file in the specified format.

See Also

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© 1991-2021 LEAD Technologies, Inc. All Rights Reserved.

Products | Support | Contact Us | Intellectual Property Notices
© 1991-2021 LEAD Technologies, Inc. All Rights Reserved.