Perform OCR in ASP.NET Core

17 Jul 202611 minutes to read

The .NET OCR library is used to extract text from scanned PDFs and images in ASP.NET Core applications with the help of Google’s Tesseract Optical Character Recognition engine.

Prerequisites

Version Compatibility

Syncfusion.PDF.OCR.Net.Core supports .NET 8.0 and later versions.

Supported Inputs

The OCR processor supports the following input formats:

Single-page and multi-page PDF documents
Scanned images in common formats (JPEG, PNG, TIFF)
Recommended DPI: 200 DPI or higher for optimal OCR accuracy

Required Software

.NET 8 SDK or later
Visual Studio, Visual Studio Code, or JetBrains Rider

Register the License Key

NOTE

Starting with v16.2.0.x, if you reference Syncfusion® assemblies from trial setup or from the NuGet feed, you must add the Syncfusion.Licensing assembly reference and register a license key in your application. For more information, see the licensing documentation.

Include the following code in the Program.cs file to register the license key:

C#
using Syncfusion.Licensing;

// Register Syncfusion license at application startup
SyncfusionLicenseProvider.RegisterLicense("YOUR LICENSE KEY");

NOTE

Beginning from version 21.1.x, the TesseractBinaries and Tesseract language data folders are now included by default; you no longer have to set these paths explicitly.

The current NuGet package includes Tesseract 5.0, which provides support for 100+ languages.

Steps to perform OCR on an entire PDF document in ASP.NET Core application

Step 1: Create a new C# ASP.NET Core Web Application project. Create ASP.NET Core Web application

Step 2: In the configuration window, select your target framework (.NET 8.0 or later), name your project, and click Next. ASP.NET Core project configuration1

ASP.NET Core project configuration2

Step 3: Install the Syncfusion.PDF.OCR.Net.Core NuGet package into your ASP.NET Core application from NuGet.org. PDF OCR ASP.NET Core NuGet package

Step 4: A default controller with the name HomeController.cs is added to the ASP.NET Core MVC project. Include the following namespaces in that HomeController.cs file.

C#
using Syncfusion.OCRProcessor;
using Syncfusion.Pdf.Parsing;

Step 5: Add a new button in index.cshtml as follows.

CSHTML
@{Html.BeginForm("PerformOCR", "Home", FormMethod.Post);
   {
      <div>
         <input type="submit" value="Perform OCR" style="width:150px;height:27px" />
      </div>
   }
   Html.EndForm();
}

Step 6: Add a new action method named PerformOCR in the HomeController.cs and use the following code sample to perform OCR on the entire PDF document using PerformOCR method of the OCRProcessor class.

C#
public IActionResult PerformOCR()
{
   //Initialize the OCR processor.
   using (OCRProcessor processor = new OCRProcessor())
   {
      FileStream fileStream = new FileStream("Input.pdf", FileMode.Open, FileAccess.Read);
      //Load a PDF document.
      PdfLoadedDocument lDoc = new PdfLoadedDocument(fileStream);
      //Set OCR language to process.
      processor.Settings.Language = Languages.English;
      //Process OCR by providing the PDF document.
      processor.PerformOCR(lDoc);
      //Create memory stream.
      MemoryStream stream = new MemoryStream();
      //Save the document to memory stream.
      lDoc.Save(stream);
      lDoc.Close();
      //Set the position as '0'.
      stream.Position = 0;
      //Download the PDF document in the browser.
      FileStreamResult fileStreamResult = new FileStreamResult(stream, "application/pdf");
      fileStreamResult.FileDownloadName = "Sample.pdf";
      return fileStreamResult;
   }
}

Step 7: Build the project.

Click the Build button in the toolbar or press Ctrl+Shift+B to build the project.

Step 8: Run the project.

Click the Run button (green arrow) in the toolbar or press F5 to run the app.

Step 1: Open the terminal (Ctrl+`) and run the following command to create a new C# ASP.NET Core Web Application project:

dotnet new mvc -n CreatePdfASPNETCoreAPP

Step 2: Replace CreatePdfASPNETCoreAPP with your desired project name.

Step 3: Navigate to the project directory using the following command:

cd CreatePdfASPNETCoreAPP

Step 4: Use the following command in the terminal to add the Syncfusion.PDF.OCR.Net.Core package to your project:

dotnet add package Syncfusion.PDF.OCR.NET

Step 5: A default controller with the name HomeController.cs is added to the ASP.NET Core MVC project. Include the following namespaces in that HomeController.cs file.

C#
using Syncfusion.OCRProcessor;
using Syncfusion.Pdf.Parsing;

Step 6: Add a new button in index.cshtml as follows.

CSHTML
@{Html.BeginForm("PerformOCR", "Home", FormMethod.Post);
   {
      <div>
         <input type="submit" value="Perform OCR" style="width:150px;height:27px" />
      </div>
   }
   Html.EndForm();
}

Step 7: Add a new action method named PerformOCR in the HomeController.cs and use the following code sample to perform OCR on the entire PDF document using the PerformOCR method of the OCRProcessor class.

C#
public IActionResult PerformOCR()
{
   //Initialize the OCR processor.
   using (OCRProcessor processor = new OCRProcessor())
   {
      FileStream fileStream = new FileStream("Input.pdf", FileMode.Open, FileAccess.Read);
      //Load a PDF document.
      PdfLoadedDocument lDoc = new PdfLoadedDocument(fileStream);
      //Set the Tesseract version (Version5_0 is included in the current NuGet package).
      processor.Settings.TesseractVersion = TesseractVersion.Version5_0;
      //Set OCR language to process.
      processor.Settings.Language = Languages.English;
      //Process OCR by providing the PDF document.
      processor.PerformOCR(lDoc);
      //Create memory stream.
      MemoryStream stream = new MemoryStream();
      //Save the document to memory stream.
      lDoc.Save(stream);
      lDoc.Close();
      fileStream.Dispose();
      //Set the position as '0'.
      stream.Position = 0;
      //Download the PDF document in the browser.
      FileStreamResult fileStreamResult = new FileStreamResult(stream, "application/pdf");
      fileStreamResult.FileDownloadName = "Sample.pdf";
      return fileStreamResult;
   }
}

Step 8: Build the project.

Run the following command in the terminal to build the project:

dotnet build

Step 9: Run the project.

Run the following command in the terminal to run the project:

dotnet run

Step 1: Open JetBrains Rider and create a new ASP.NET Core Web application project.

Launch JetBrains Rider.
Click New Solution on the welcome screen.

Launch JetBrains Rider

In the new Solution dialog, select Project Type as Web.
Select the target framework (.NET 8.0 or later) and template as Web App (Model-View-Controller).
Enter a project name and specify the location.
Click Create.

Creating a new .NET Core console application in JetBrains Rider

Step 2: Install the NuGet package from NuGet.org.

Click the NuGet icon in the Rider toolbar and type Syncfusion.PDF.OCR.Net.Core in the search bar.
Ensure that “nuget.org” is selected as the package source.
Select the latest Syncfusion.PDF.OCR.NET NuGet package from the list.
Click the + (Add) button to add the package.

Select the Syncfusion.PDF.OCR.NET package

Click the Install button to complete the installation.

Install the package

Step 3: A default controller with the name HomeController.cs is added to the ASP.NET Core MVC project. Include the following namespaces in that HomeController.cs file.

C#
using Syncfusion.OCRProcessor;
using Syncfusion.Pdf.Parsing;

Step 4: Add a new button in index.cshtml as follows.

CSHTML
@{Html.BeginForm("PerformOCR", "Home", FormMethod.Post);
   {
      <div>
         <input type="submit" value="Perform OCR" style="width:150px;height:27px" />
      </div>
   }
   Html.EndForm();
}

Step 5: Add a new action method named PerformOCR in the HomeController.cs and use the following code sample to perform OCR on the entire PDF document using the PerformOCR method of the OCRProcessor class.

C#
public IActionResult PerformOCR()
{
   //Initialize the OCR processor.
   using (OCRProcessor processor = new OCRProcessor())
   {
      FileStream fileStream = new FileStream("Input.pdf", FileMode.Open, FileAccess.Read);
      //Load a PDF document.
      PdfLoadedDocument lDoc = new PdfLoadedDocument(fileStream);
      //Set the Tesseract version (Version5_0 is included in the current NuGet package).
      processor.Settings.TesseractVersion = TesseractVersion.Version5_0;
      //Set OCR language to process.
      processor.Settings.Language = Languages.English;
      //Process OCR by providing the PDF document.
      processor.PerformOCR(lDoc);
      //Create memory stream.
      MemoryStream stream = new MemoryStream();
      //Save the document to memory stream.
      lDoc.Save(stream);
      lDoc.Close();
      fileStream.Dispose();
      //Set the position as '0'.
      stream.Position = 0;
      //Download the PDF document in the browser.
      FileStreamResult fileStreamResult = new FileStreamResult(stream, "application/pdf");
      fileStreamResult.FileDownloadName = "Sample.pdf";
      return fileStreamResult;
   }
}

Step 6: Build the project.

Click the Build button in the toolbar or press Ctrl+Shift+B to build the project.

Step 7: Run the project.

Click the Run button (green arrow) in the toolbar or press F5 to run the app.

By executing the program, you will get a PDF document as follows.
OCR ASP.NET_Core Output

A complete working sample can be downloaded from the Github.

Click here to explore the rich set of Syncfusion^® PDF library features.

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Perform OCR in ASP.NET Core

Prerequisites

Steps to perform OCR on an entire PDF document in ASP.NET Core application