This tutorial shows how to preprocess an image for OCR in a C# .NET Core application using the LEADTOOLS SDK.
|Summary||This tutorial covers how to preprocess and image for OCR using the
|Completion Time||30 minutes|
|Visual Studio Project||Download tutorial project (1 KB)|
|Platform||C# .NET Core 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 - C# .NET Core tutorial.
Start with a copy of the project created in the Add References and Set a License tutorial. If you do not have that project, follow the steps in that tutorial to create it.
The references needed depend upon the purpose of the project. References can be added via NuGet packages.
This tutorial requires the following NuGet package:
For a complete list of which DLL files are required for your application, refer to Files to be Included With Your Application.
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 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 the Solution Explorer, open
Program.cs. Add the following statements to the
using block at the top of
Add a new method to the
Program class named
OCRPreProcessing(). Call the
OCRPreProcessing() method inside the
Main() method below the set license code, as shown below.
static void Main(string args)
Console.WriteLine("Error setting license");
Console.WriteLine("License file set successfully");
Add the code below to the
OCRPreProcessing() method to initialize the
IOcrEngine, preprocess the loaded image, and run OCR exporting to a 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 console appears and the application will "clean-up" the loaded image and export it as a searchable PDF.
This tutorial showed how to preprocess an image for OCR using the
AutoPreprocess method inside the
IOcrPage interface, and save it as a searchable PDF. Also, we covered how to use the