Manually Recognize and Process a Form - Console C#

This tutorial shows how to create a master set of forms, recognize, and process a form using LEADTOOLS Low-Level Form Interface.

Before any functionality from the SDK can be leveraged, a valid runtime license will have to be set. For instructions on how to obtain a runtime license refer to Obtaining a License.

Summary This tutorial covers how to recognize and process a form in a C# Console application.
Completion Time 30 minutes
Visual Studio Project Download tutorial project (4 KB)
Platform Windows C# 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 Manually Recognize and Process a Form - Console C# tutorial.

Create the Project and Add the 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.

Initialize the FormRecognitionEngine, RasterCodes, OcrEngine, and FormProcessingEngine

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.

// Using block at the top 
using System; 
using System.IO; 
using System.Collections.Generic; 
using Leadtools; 
using Leadtools.Codecs; 
using Leadtools.Forms.Common; 
using Leadtools.Ocr; 
using Leadtools.Forms.Recognition; 
using Leadtools.Forms.Recognition.Ocr; 
using Leadtools.Forms.Processing; 

Add a new method called InitFormsEngines() and call it inside the Main method. Add the below code to initialize the FormRecognitionEngine, RasterCodes, IOcrEngine and FormProcessingEngine.

// Add these global members in the class 
private static FormRecognitionEngine recognitionEngine; 
private static RasterCodecs codecs; 
private static IOcrEngine formsOCREngine; 
private static FormProcessingEngine processingEngine; 
static void Main(string[] args) 
static void InitFormsEngines() 
    Console.WriteLine("Initializing Engines"); 
    codecs = new RasterCodecs(); 
    recognitionEngine = new FormRecognitionEngine(); 
    processingEngine = new FormProcessingEngine(); 
    formsOCREngine = OcrEngineManager.CreateEngine(OcrEngineType.LEAD); 
    formsOCREngine.Startup(codecs, null, null, @"C:\LEADTOOLS21\Bin\Common\OcrLEADRuntime"); 
    OcrObjectsManager ocrObjectsManager = new OcrObjectsManager(formsOCREngine); 
    ocrObjectsManager.Engine = formsOCREngine; 
    Console.WriteLine("Engines initialized successfully"); 

Add the Master Form Attributes Creation Code

In the Program class add two new methods called CreateMasterFormAttributes() and RecognizeForm().

private static void CreateMasterFormAttributes() 
    Console.WriteLine("Processing Master Form"); 
    string[] masterFileNames = Directory.GetFiles(@"C:\LEADTOOLS21\Resources\Images\Forms\MasterForm Sets\OCR", "*.tif", SearchOption.AllDirectories); 
    foreach (string masterFileName in masterFileNames) 
        string formName = Path.GetFileNameWithoutExtension(masterFileName); 
        using (RasterImage image = codecs.Load(masterFileName, 0, CodecsLoadByteOrder.BgrOrGray, 1, -1)) 
            FormRecognitionAttributes masterFormAttributes = recognitionEngine.CreateMasterForm(formName, Guid.Empty, null); 
            for (int i = 0; i < image.PageCount; i++) 
                image.Page = i + 1; 
                recognitionEngine.AddMasterFormPage(masterFormAttributes, image, null); 
            File.WriteAllBytes(formName + ".bin", masterFormAttributes.GetData()); 
    Console.WriteLine("Master Form Processing Complete"); 
private static void RecognizeForm() 
    Console.WriteLine("Recognizing Form\n"); 
    var GetProjectDirectory = Path.GetDirectoryName(System.Reflection.Assembly.GetExecutingAssembly().Location); 
    string formToRecognize = @"C:\LEADTOOLS21\Resources\Images\Forms\Forms to be Recognized\OCR\W9_OCR_Filled.tif"; 
    using (RasterImage image = codecs.Load(formToRecognize, 0, CodecsLoadByteOrder.BgrOrGray, 1, -1)) 
        FormRecognitionAttributes filledFormAttributes = recognitionEngine.CreateForm(null); 
        for (int i = 0; i < image.PageCount; i++) 
            image.Page = i + 1; 
            recognitionEngine.AddFormPage(filledFormAttributes, image, null); 
        string resultMessage = "The form could not be recognized"; 
        string[] masterFileNames = Directory.GetFiles(GetProjectDirectory, "*.bin"); 
        foreach (string masterFileName in masterFileNames) 
            string fieldsfName = Path.GetFileNameWithoutExtension(masterFileName) + ".xml"; 
            string fieldsfullPath = Path.Combine(@"C:\LEADTOOLS21\Resources\Images\Forms\MasterForm Sets\OCR", fieldsfName); 
            FormRecognitionAttributes masterFormAttributes = new FormRecognitionAttributes(); 
            FormRecognitionResult recognitionResult = recognitionEngine.CompareForm(masterFormAttributes, filledFormAttributes, null); 
            if (recognitionResult.Confidence >= 80) 
                List<PageAlignment> alignment = new List<PageAlignment>(); 
                for (int k = 0; k < recognitionResult.PageResults.Count; k++) 
                resultMessage = $"This form has been recognized as a {Path.GetFileNameWithoutExtension(masterFileName)}"; 
                ProcessForm(image, alignment); 
        Console.WriteLine(resultMessage, "Recognition Results"); 

Call both methods in the Main method after the InitFormsEngines() method.

// call these in Main() after InitFormsEngines(); 

Shipped with the LEADTOOLS SDK are sample master form sets and sample filled forms for recognition and processing. This tutorial will utilize these samples. After installation the sample files can be found here: <INSTALL_DIR>\LEADTOOLS21\Resources\Images\Forms

Add the Field Creation and Process Form Code

In the Program class add a new method, ProcessForm(RasterImage image,List<PageAlignment> alignment). This method is called in RecognizeForm() from the previous step.

private static void ProcessForm(RasterImage image, List<PageAlignment> alignment) 
    processingEngine.OcrEngine = formsOCREngine; 
    string resultsMessage = string.Empty; 
    processingEngine.Process(image, alignment); 
    foreach (FormPage formPage in processingEngine.Pages) 
        foreach (FormField field in formPage) 
            if (field != null) 
                resultsMessage = $"{resultsMessage}{field.Name} = {(field.Result as TextFormFieldResult).Text}\n"; 
    if (string.IsNullOrEmpty(resultsMessage)) 
        Console.WriteLine("No fields were processed", "FieldProcessing Results"); 
        Console.WriteLine(resultsMessage, "Field ProcessingResults"); 

Shutdown the OCR Engine

In the Main method add the below code under the RecognizeForm() method to properly shutdown the OCR engine and dispose of the IOcrEngine.

if (formsOCREngine != null && formsOCREngine.IsStarted) 

Run the Project

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

If the steps were followed correctly, the application runs and displays the recognized form.

Recognition result

For this example, a W9 form is used with 6 filled fields: Business Name, Address, City, State, Zip, and Name. All of these fields were correctly detected and labeled, as well as the form being correctly recognized.


This tutorial showed how to create a set of attributes from master forms with FormRecognitionAttributes class and recognize a form using the FormRecognitionEngine class.

See Also

Help Version 21.0.2021.7.27
Products | Support | Contact Us | Intellectual Property Notices
© 1991-2021 LEAD Technologies, Inc. All Rights Reserved.

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