This tutorial shows how to create a C# Windows Console application that uses the LEADTOOLS SDK to preprocess images for OCR Recognition.
|Summary||This tutorial covers how to use LEADTOOLS Image Processing SDK technology in a C# Windows Console application|
|Completion Time||30 minutes|
|Visual Studio Project||Download tutorial project (3 KB)|
|Platform||C# Windows Console Application|
|IDE||Visual Studio 2017, 2019|
|Development License||Download LEADTOOLS|
|Try it in another language|
Get familiar with the basic steps of creating a project by reviewing the Add References and Set a License tutorial, before working on the Preprocess an Image for OCR - Console C# tutorial.
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
For a complete list of which Codec DLLs are required for specific formats, refer to File Format Support.
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.
With the project created, the references added, and the license set, coding can begin.
In Solution Explorer, open
Program.cs and add the following statements to the
using block at the top:
// Using block at the top
Add a new method called
OCRPreProcessing() and call it inside the
Main method after the
SetLicense() method call. Add the below code to start up the OCR Engine, load a TIFF image as an
IOcrPage, preprocess the TIF image, and then run OCR recognition and export to searchable PDF.
static void OCRPreProcessing()
string tifFileName = @"C:\LEADTOOLS21\Resources\Images\Clean.tif";
string pdfFileName = @"C:\LEADTOOLS21\Resources\Images\Clean.pdf";
using (IOcrEngine ocrEngine = OcrEngineManager.CreateEngine(OcrEngineType.LEAD))
// Start the engine using default parameters
ocrEngine.Startup(null, null, null, @"C:\LEADTOOLS21\Bin\Common\OcrLEADRuntime");
// Create an OCR document
using (IOcrDocument ocrDocument = ocrEngine.DocumentManager.CreateDocument())
// Add this image to the document
IOcrPage ocrPage = ocrDocument.Pages.AddPage(tifFileName, null);
// Auto-preprocess it
// Recognize it and save it as PDF
ocrDocument.Save(pdfFileName, DocumentFormat.Pdf, null);
Run the project by pressing F5, or by selecting Debug -> Start Debugging.
If the steps were followed correctly, the application should OCR the TIFF and provide a cleaned up PDF document.
This tutorial showed how to OCR an image, clean up image, and save to PDF. Also, it covered how to use the