MODI OCR C# vs. IronOCR: Choosing the Right Optical Character Recognition Library in C#

How Does the Comparison Break Down at a Glance?

How Does Microsoft Office Document Imaging Perform OCR in C#?

MODI performs optical character recognition (OCR) through a COM-based object model. The process starts by creating a MODI.Document object, loading an image file path, and invoking the OCR method to analyze images and identify characters. After the OCR process completes, text and layout information are accessible through each page's Image and Layout objects.

To use MODI in a Visual Studio project, a reference to the Microsoft Office Document Imaging Type Library must be added. In Solution Explorer, right-click on the References folder, select the COM tab, and choose the appropriate MODI version (11.0 for Office 2003 or 12.0 for Office 2007).

// MODI OCR: Extracting text from a scanned TIFF document
private string ExtractTextFromImage(string path)
{
    string extractedText = "";
    MODI.Document doc = new MODI.Document();
    try
    {
        // Create the document object from the image file path
        doc.Create(path);
        // Run optical character recognition with English language
        doc.OCR(MODI.MiLANGUAGES.miLANG_ENGLISH, true, true);
        // Access the first page image and retrieve recognized text
        MODI.Image modiImage = (MODI.Image)doc.Images[0];
        extractedText = modiImage.Layout.Text;
    }
    catch (Exception ex)
    {
        // Handle OCR exceptions for unsupported or corrupted image files
        string message = ex.Message;
        Console.WriteLine(message);
    }
    finally
    {
        doc.Close(false);
        System.Runtime.InteropServices.Marshal.ReleaseComObject(doc);
    }
    return extractedText;
}

// MODI OCR: Extracting text from a scanned TIFF document
private string ExtractTextFromImage(string path)
{
    string extractedText = "";
    MODI.Document doc = new MODI.Document();
    try
    {
        // Create the document object from the image file path
        doc.Create(path);
        // Run optical character recognition with English language
        doc.OCR(MODI.MiLANGUAGES.miLANG_ENGLISH, true, true);
        // Access the first page image and retrieve recognized text
        MODI.Image modiImage = (MODI.Image)doc.Images[0];
        extractedText = modiImage.Layout.Text;
    }
    catch (Exception ex)
    {
        // Handle OCR exceptions for unsupported or corrupted image files
        string message = ex.Message;
        Console.WriteLine(message);
    }
    finally
    {
        doc.Close(false);
        System.Runtime.InteropServices.Marshal.ReleaseComObject(doc);
    }
    return extractedText;
}

' MODI OCR: Extracting text from a scanned TIFF document
Private Function ExtractTextFromImage(ByVal path As String) As String
    Dim extractedText As String = ""
    Dim doc As New MODI.Document()
    Try
        ' Create the document object from the image file path
        doc.Create(path)
        ' Run optical character recognition with English language
        doc.OCR(MODI.MiLANGUAGES.miLANG_ENGLISH, True, True)
        ' Access the first page image and retrieve recognized text
        Dim modiImage As MODI.Image = CType(doc.Images(0), MODI.Image)
        extractedText = modiImage.Layout.Text
    Catch ex As Exception
        ' Handle OCR exceptions for unsupported or corrupted image files
        Dim message As String = ex.Message
        Console.WriteLine(message)
    Finally
        doc.Close(False)
        System.Runtime.InteropServices.Marshal.ReleaseComObject(doc)
    End Try
    Return extractedText
End Function

This function demonstrates the standard MODI workflow: the Create method loads the file, the OCR method performs recognition using a specified language, and Layout.Text provides the extracted string. The return extractedText statement delivers the output to the caller.

While MODI offers decent accuracy for crisp, high-resolution document images, it has notable limitations. It only supports TIFF, MDI, and BMP formats. It requires a Microsoft Office installation on every computer that runs the application, including production servers. There is no built-in support for scanning low-quality images, correcting skew, or reducing digital noise. Additionally, because MODI relies on COM Interop, it cannot be used in .NET Core, .NET 5+, or any cross-platform scenario, making it unsuitable for modern deployment targets like Docker containers or Azure App Services.

How Does a Modern .NET Library Handle OCR Functionality?

IronOCR replaces the COM Interop approach with a pure .NET API that installs via a single NuGet package. The IronTesseract class wraps a heavily optimized Tesseract 5 engine, and the OcrInput class handles image loading, preprocessing, and multi-format support, all without requiring Microsoft Office or any external dependency on the target computer.

using IronOcr;
// Create the IronTesseract OCR engine object
var ocr = new IronTesseract();
using var input = new OcrInput();
// Load images in any common format — PNG, JPEG, TIFF, BMP, GIF, or PDF
input.LoadImage("scanned-document.tiff");
// Apply filters to correct low-quality scans automatically
input.Deskew();   // Straighten skewed page images
input.DeNoise();  // Remove digital noise from scanning artifacts
// Read text from the processed document
var result = ocr.Read(input);
// Output plain text
Console.WriteLine(result.Text);
// Save as a searchable PDF for document management system integration
result.SaveAsSearchablePdf("output-searchable.pdf");

using IronOcr;
// Create the IronTesseract OCR engine object
var ocr = new IronTesseract();
using var input = new OcrInput();
// Load images in any common format — PNG, JPEG, TIFF, BMP, GIF, or PDF
input.LoadImage("scanned-document.tiff");
// Apply filters to correct low-quality scans automatically
input.Deskew();   // Straighten skewed page images
input.DeNoise();  // Remove digital noise from scanning artifacts
// Read text from the processed document
var result = ocr.Read(input);
// Output plain text
Console.WriteLine(result.Text);
// Save as a searchable PDF for document management system integration
result.SaveAsSearchablePdf("output-searchable.pdf");

Imports IronOcr

' Create the IronTesseract OCR engine object
Dim ocr As New IronTesseract()
Using input As New OcrInput()
    ' Load images in any common format — PNG, JPEG, TIFF, BMP, GIF, or PDF
    input.LoadImage("scanned-document.tiff")
    ' Apply filters to correct low-quality scans automatically
    input.Deskew()   ' Straighten skewed page images
    input.DeNoise()  ' Remove digital noise from scanning artifacts
    ' Read text from the processed document
    Dim result = ocr.Read(input)
    ' Output plain text
    Console.WriteLine(result.Text)
    ' Save as a searchable PDF for document management system integration
    result.SaveAsSearchablePdf("output-searchable.pdf")
End Using

What Are the Key Differences When Extracting Text from Images?

The real gap between these two options shows up the second you stop using "perfect" sample files and start dealing with real-world documents. We're talking about those messy scans with coffee stains, tilted pages, or low-res photos from a smartphone.

MODI was built for a different era, specifically for clean, high-contrast office documents. If you've got a crisp TIFF file from a high-end scanner, it'll do just fine. But if your image is even slightly rotated or has some digital "noise," MODI's accuracy falls off a cliff. Since it doesn't have any built-in filters to fix these issues, you're stuck preprocessing images yourself using a second library like GDI+ or System.Drawing before you even start the OCR process. It's also a bit of a pain to manage memory; if you don't manually call Marshal.ReleaseComObject, you'll likely run into memory leaks in production.

IronOCR handles this heavy lifting for you right out of the box. Instead of writing custom code to clean up an image, you just call input.Deskew() or input.DeNoise(). These filters prep the image so the engine hits that 99.8% accuracy mark, even on "ugly" documents.

Pro-Tip: If you're migrating from MODI, don't just swap the code, take advantage of the layout data. Unlike MODI, which mostly gives you a giant "blob" of text, IronOCR breaks things down into paragraphs and lines with confidence scores. This is a lifesaver if you're building an automated invoice processor and need to flag documents that might need a human's eyes for verification.

It's also worth noting that IronOCR handles multi-page TIFFs and PDFs as a single object. You don't have to loop through images manually like you did with the old MODI.Images collection. It's just faster, cleaner, and honestly, a lot less fragile.

How Can Developers Migrate from the Legacy Approach?

Replacing MODI in an existing project is straightforward. The core migration involves swapping the COM reference for a NuGet package and updating the OCR method calls. Here's how the MODI pattern translates to the modern equivalent:

using IronOcr;
// Replace: MODI.Document doc = new MODI.Document();
var ocr = new IronTesseract();
// Replace: doc.Create(filePath); with OcrInput
using var input = new OcrInput();
input.LoadImage("document.tiff");  // Accepts the same TIFF files MODI used
// Replace: doc.OCR(MODI.MiLANGUAGES.miLANG_ENGLISH, true, true);
ocr.Language = OcrLanguage.English;
// Replace: modiImage.Layout.Text
var result = ocr.Read(input);
string text = result.Text;
Console.WriteLine(text);

using IronOcr;
// Replace: MODI.Document doc = new MODI.Document();
var ocr = new IronTesseract();
// Replace: doc.Create(filePath); with OcrInput
using var input = new OcrInput();
input.LoadImage("document.tiff");  // Accepts the same TIFF files MODI used
// Replace: doc.OCR(MODI.MiLANGUAGES.miLANG_ENGLISH, true, true);
ocr.Language = OcrLanguage.English;
// Replace: modiImage.Layout.Text
var result = ocr.Read(input);
string text = result.Text;
Console.WriteLine(text);

Imports IronOcr

Dim ocr As New IronTesseract()

Using input As New OcrInput()
    input.LoadImage("document.tiff") ' Accepts the same TIFF files MODI used
    ocr.Language = OcrLanguage.English
    Dim result = ocr.Read(input)
    Dim text As String = result.Text
    Console.WriteLine(text)
End Using

The mapping is nearly one-to-one: MODI.Document.Create becomes OcrInput.LoadImage, the OCR method with language parameters becomes ocr.Language plus ocr.Read, and Layout.Text becomes result.Text. No COM reference, no Office dependency, no Marshal.ReleaseComObject to manage memory manually.

Beyond the direct replacement, migration also unlocks features that simply don't exist in MODI: cross-platform deployment to Linux and macOS, cloud and container deployment, searchable PDF output, and the complete Tesseract 5 engine with custom font training capabilities.

Which Solution Best Fits Modern OCR Needs?

MODI served its purpose in an era when Microsoft Office was a standard fixture on every Windows computer. For teams maintaining legacy systems that already depend on Office 2003 or 2007, it may still function, but it represents a fragile dependency on discontinued software with no path forward.

For any new project, or any legacy system facing modernization, IronOCR provides a complete, actively maintained solution. It eliminates the Office dependency entirely, runs on every major platform, handles poor-quality images that would stump the older approach, and delivers structured OCR output far beyond plain text. With extensive documentation, direct engineering support, and perpetual licensing from $749, it's built for production-grade document processing at scale.

Get stated with IronOCR now.

Start for Free

Ready to deploy OCR in production? Explore IronOCR licensing options to find the right fit for your team.