GdPicture.NET OCR vs IronOCR: .NET OCR Library

The Image ID Lifecycle

The defining architectural characteristic of GdPicture is integer image ID management. Loading any image allocates memory inside the GdPicture runtime and returns an int handle. You use that integer to reference the image in all subsequent calls. When you are done, you call ReleaseGdPictureImage with that integer. If you do not, the memory is not released until the process ends.

using GdPicture14;

// Every image load returns an integer handle
int imageId = _imaging.CreateGdPictureImageFromFile(imagePath);

if (imageId == 0)
{
    throw new Exception($"Failed to load image: {_imaging.GetStat()}");
}

try
{
    _ocr.SetImage(imageId);
    _ocr.Language = "eng";

    string resultId = _ocr.RunOCR();

    if (string.IsNullOrEmpty(resultId))
    {
        throw new Exception($"OCR failed: {_ocr.GetStat()}");
    }

    return _ocr.GetOCRResultText(resultId);
}
finally
{
    // CRITICAL: omitting this line causes a memory leak
    _imaging.ReleaseGdPictureImage(imageId);
}

using GdPicture14;

// Every image load returns an integer handle
int imageId = _imaging.CreateGdPictureImageFromFile(imagePath);

if (imageId == 0)
{
    throw new Exception($"Failed to load image: {_imaging.GetStat()}");
}

try
{
    _ocr.SetImage(imageId);
    _ocr.Language = "eng";

    string resultId = _ocr.RunOCR();

    if (string.IsNullOrEmpty(resultId))
    {
        throw new Exception($"OCR failed: {_ocr.GetStat()}");
    }

    return _ocr.GetOCRResultText(resultId);
}
finally
{
    // CRITICAL: omitting this line causes a memory leak
    _imaging.ReleaseGdPictureImage(imageId);
}

Imports GdPicture14

' Every image load returns an integer handle
Dim imageId As Integer = _imaging.CreateGdPictureImageFromFile(imagePath)

If imageId = 0 Then
    Throw New Exception($"Failed to load image: {_imaging.GetStat()}")
End If

Try
    _ocr.SetImage(imageId)
    _ocr.Language = "eng"

    Dim resultId As String = _ocr.RunOCR()

    If String.IsNullOrEmpty(resultId) Then
        Throw New Exception($"OCR failed: {_ocr.GetStat()}")
    End If

    Return _ocr.GetOCRResultText(resultId)
Finally
    ' CRITICAL: omitting this line causes a memory leak
    _imaging.ReleaseGdPictureImage(imageId)
End Try

When processing multi-page PDFs, each rendered page produces a separate image ID. A 100-page document at 200 DPI can allocate 1–5 GB of memory if cleanup is missed. The correct pattern requires collecting all IDs and releasing them in a finally block — but that discipline is entirely the developer's responsibility.

Detailed Feature Comparison

GdPicture Approach

Every image in GdPicture exists as an integer handle in a runtime-managed pool. You acquire the handle by loading an image, pass that integer to OCR and other operations, then release it when done. The pattern is explicit and correct when followed. The problem is that it is easy to get wrong, and the consequence is unbounded memory growth.

The PDF OCR workflow demonstrates the risk most clearly. Each call to pdf.RenderPageToGdPictureImage() allocates a new raster image in memory and returns a new integer ID. A 100-page document creates 100 separate allocations. Miss one ReleaseGdPictureImage call and the process accumulates leaked memory:

using GdPicture14;

public string ExtractTextFromPdf(string pdfPath)
{
    var text = new StringBuilder();

    using var pdf = new GdPicturePDF();

    GdPictureStatus status = pdf.LoadFromFile(pdfPath, false);
    if (status != GdPictureStatus.OK)
        throw new Exception($"Failed to load PDF: {status}");

    int pageCount = pdf.GetPageCount();

    for (int i = 1; i <= pageCount; i++)
    {
        pdf.SelectPage(i);

        // Each page render = new memory allocation + new integer ID
        int imageId = pdf.RenderPageToGdPictureImage(200, false);

        if (imageId == 0) continue;

        try
        {
            _ocr.SetImage(imageId);
            _ocr.Language = "eng";
            string resultId = _ocr.RunOCR();

            if (!string.IsNullOrEmpty(resultId))
                text.AppendLine(_ocr.GetOCRResultText(resultId));
        }
        finally
        {
            // Without this: ~10–50MB leaked per page
            _imaging.ReleaseGdPictureImage(imageId);
        }
    }

    return text.ToString();
}

using GdPicture14;

public string ExtractTextFromPdf(string pdfPath)
{
    var text = new StringBuilder();

    using var pdf = new GdPicturePDF();

    GdPictureStatus status = pdf.LoadFromFile(pdfPath, false);
    if (status != GdPictureStatus.OK)
        throw new Exception($"Failed to load PDF: {status}");

    int pageCount = pdf.GetPageCount();

    for (int i = 1; i <= pageCount; i++)
    {
        pdf.SelectPage(i);

        // Each page render = new memory allocation + new integer ID
        int imageId = pdf.RenderPageToGdPictureImage(200, false);

        if (imageId == 0) continue;

        try
        {
            _ocr.SetImage(imageId);
            _ocr.Language = "eng";
            string resultId = _ocr.RunOCR();

            if (!string.IsNullOrEmpty(resultId))
                text.AppendLine(_ocr.GetOCRResultText(resultId));
        }
        finally
        {
            // Without this: ~10–50MB leaked per page
            _imaging.ReleaseGdPictureImage(imageId);
        }
    }

    return text.ToString();
}

Imports GdPicture14
Imports System.Text

Public Function ExtractTextFromPdf(ByVal pdfPath As String) As String
    Dim text As New StringBuilder()

    Using pdf As New GdPicturePDF()
        Dim status As GdPictureStatus = pdf.LoadFromFile(pdfPath, False)
        If status <> GdPictureStatus.OK Then
            Throw New Exception($"Failed to load PDF: {status}")
        End If

        Dim pageCount As Integer = pdf.GetPageCount()

        For i As Integer = 1 To pageCount
            pdf.SelectPage(i)

            ' Each page render = new memory allocation + new integer ID
            Dim imageId As Integer = pdf.RenderPageToGdPictureImage(200, False)

            If imageId = 0 Then Continue For

            Try
                _ocr.SetImage(imageId)
                _ocr.Language = "eng"
                Dim resultId As String = _ocr.RunOCR()

                If Not String.IsNullOrEmpty(resultId) Then
                    text.AppendLine(_ocr.GetOCRResultText(resultId))
                End If
            Finally
                ' Without this: ~10–50MB leaked per page
                _imaging.ReleaseGdPictureImage(imageId)
            End Try
        Next
    End Using

    Return text.ToString()
End Function

Batch processing across multiple PDFs compounds this. The documentation for each for loop must carry a note reminding maintainers to collect IDs in a List<int> and release them all in finally. That is infrastructure work, not OCR work.

IronOCR Approach

OcrInput is a standard IDisposable. A using statement guarantees cleanup whether the method returns normally or throws. There are no integer IDs to track, no separate imaging component to initialize, and no external DPI rendering step for PDF pages.

using IronOcr;

public string ExtractTextFromPdf(string pdfPath)
{
    // LoadPdf handles page rendering internally
    using var input = new OcrInput();
    input.LoadPdf(pdfPath);

    var result = new IronTesseract().Read(input);

    foreach (var page in result.Pages)
        Console.WriteLine($"Page {page.PageNumber}: {page.Text}");

    return result.Text;
    // using block exits — all internal resources released automatically
}

using IronOcr;

public string ExtractTextFromPdf(string pdfPath)
{
    // LoadPdf handles page rendering internally
    using var input = new OcrInput();
    input.LoadPdf(pdfPath);

    var result = new IronTesseract().Read(input);

    foreach (var page in result.Pages)
        Console.WriteLine($"Page {page.PageNumber}: {page.Text}");

    return result.Text;
    // using block exits — all internal resources released automatically
}

Imports IronOcr

Public Function ExtractTextFromPdf(pdfPath As String) As String
    ' LoadPdf handles page rendering internally
    Using input As New OcrInput()
        input.LoadPdf(pdfPath)

        Dim result = New IronTesseract().Read(input)

        For Each page In result.Pages
            Console.WriteLine($"Page {page.PageNumber}: {page.Text}")
        Next

        Return result.Text
        ' using block exits — all internal resources released automatically
    End Using
End Function

For password-protected PDFs, the parameter is a named argument rather than a separate overload that requires additional status checking:

using var input = new OcrInput();
input.LoadPdf("encrypted.pdf", Password: "secret");

var result = new IronTesseract().Read(input);
result.SaveAsSearchablePdf("searchable-output.pdf");

using var input = new OcrInput();
input.LoadPdf("encrypted.pdf", Password: "secret");

var result = new IronTesseract().Read(input);
result.SaveAsSearchablePdf("searchable-output.pdf");

Imports IronOcr

Using input As New OcrInput()
    input.LoadPdf("encrypted.pdf", Password:="secret")

    Dim result = New IronTesseract().Read(input)
    result.SaveAsSearchablePdf("searchable-output.pdf")
End Using

The IronOCR PDF input guide covers additional options including page-range selection. For teams already familiar with IDisposable patterns across Entity Framework, HttpClient, and stream handling, OcrInput requires no new mental model.

GdPicture Approach

The full workflow for a low-quality scanned PDF — load, preprocess, OCR each page, release — spans three component classes and requires careful status checking at each step:

using GdPicture14;

public void CreateSearchablePdf(string inputPdf, string outputPdf)
{
    using var pdf = new GdPicturePDF();

    GdPictureStatus status = pdf.LoadFromFile(inputPdf, false);
    if (status != GdPictureStatus.OK)
        throw new Exception($"Load failed: {status}");

    int pageCount = pdf.GetPageCount();

    for (int i = 1; i <= pageCount; i++)
    {
        pdf.SelectPage(i);

        // OcrPage adds text layer to each page
        // Requires: OCR plugin + PDF plugin + resource folder path
        GdPictureStatus ocrStatus = pdf.OcrPage(
            "eng",
            @"C:\GdPicture\Resources\OCR",  // External resource folder required
            "",
            200
        );

        if (ocrStatus != GdPictureStatus.OK)
            Console.WriteLine($"Warning: Page {i} OCR failed: {ocrStatus}");
    }

    pdf.SaveToFile(outputPdf, true);
}

using GdPicture14;

public void CreateSearchablePdf(string inputPdf, string outputPdf)
{
    using var pdf = new GdPicturePDF();

    GdPictureStatus status = pdf.LoadFromFile(inputPdf, false);
    if (status != GdPictureStatus.OK)
        throw new Exception($"Load failed: {status}");

    int pageCount = pdf.GetPageCount();

    for (int i = 1; i <= pageCount; i++)
    {
        pdf.SelectPage(i);

        // OcrPage adds text layer to each page
        // Requires: OCR plugin + PDF plugin + resource folder path
        GdPictureStatus ocrStatus = pdf.OcrPage(
            "eng",
            @"C:\GdPicture\Resources\OCR",  // External resource folder required
            "",
            200
        );

        if (ocrStatus != GdPictureStatus.OK)
            Console.WriteLine($"Warning: Page {i} OCR failed: {ocrStatus}");
    }

    pdf.SaveToFile(outputPdf, true);
}

Imports GdPicture14

Public Sub CreateSearchablePdf(inputPdf As String, outputPdf As String)
    Using pdf As New GdPicturePDF()

        Dim status As GdPictureStatus = pdf.LoadFromFile(inputPdf, False)
        If status <> GdPictureStatus.OK Then
            Throw New Exception($"Load failed: {status}")
        End If

        Dim pageCount As Integer = pdf.GetPageCount()

        For i As Integer = 1 To pageCount
            pdf.SelectPage(i)

            ' OcrPage adds text layer to each page
            ' Requires: OCR plugin + PDF plugin + resource folder path
            Dim ocrStatus As GdPictureStatus = pdf.OcrPage(
                "eng",
                "C:\GdPicture\Resources\OCR",  ' External resource folder required
                "",
                200
            )

            If ocrStatus <> GdPictureStatus.OK Then
                Console.WriteLine($"Warning: Page {i} OCR failed: {ocrStatus}")
            End If
        Next

        pdf.SaveToFile(outputPdf, True)
    End Using
End Sub

The ResourceFolder path is not optional. It must resolve to a directory containing .traineddata language files at runtime. That path works on the development machine, then fails in production when the service account cannot see C:\GdPicture\Resources\OCR, or when the application is deployed to Linux, or when Docker images do not include that directory structure. Debugging these failures often means chasing generic GdPictureStatus error codes that say little about root cause.

IronOCR Approach

The equivalent workflow in IronOCR — including preprocessing for deskew and noise removal — is five lines:

using IronOcr;

public void CreateSearchablePdf(string inputPdf, string outputPdf)
{
    var ocr = new IronTesseract();

    using var input = new OcrInput();
    input.LoadPdf(inputPdf);
    input.Deskew();   // No separate plugin required
    input.DeNoise();

    var result = ocr.Read(input);
    result.SaveAsSearchablePdf(outputPdf);
}

using IronOcr;

public void CreateSearchablePdf(string inputPdf, string outputPdf)
{
    var ocr = new IronTesseract();

    using var input = new OcrInput();
    input.LoadPdf(inputPdf);
    input.Deskew();   // No separate plugin required
    input.DeNoise();

    var result = ocr.Read(input);
    result.SaveAsSearchablePdf(outputPdf);
}

Imports IronOcr

Public Sub CreateSearchablePdf(inputPdf As String, outputPdf As String)
    Dim ocr As New IronTesseract()

    Using input As New OcrInput()
        input.LoadPdf(inputPdf)
        input.Deskew()   ' No separate plugin required
        input.DeNoise()

        Dim result = ocr.Read(input)
        result.SaveAsSearchablePdf(outputPdf)
    End Using
End Sub

English language support is embedded in the NuGet package. Additional languages install as NuGet packages (IronOcr.Languages.French) rather than .traineddata files in a filesystem path. The image quality correction guide and image orientation correction guide cover the full set of preprocessing options available on OcrInput.

For confidence-aware processing — filtering results below a threshold before writing to a database, for instance — the result object exposes confidence directly:

var result = new IronTesseract().Read("scanned.jpg");
Console.WriteLine($"Confidence: {result.Confidence}%");

// Per-word confidence for fine-grained filtering
var highConfidenceWords = result.Words
    .Where(w => w.Confidence > 85)
    .Select(w => w.Text);

var result = new IronTesseract().Read("scanned.jpg");
Console.WriteLine($"Confidence: {result.Confidence}%");

// Per-word confidence for fine-grained filtering
var highConfidenceWords = result.Words
    .Where(w => w.Confidence > 85)
    .Select(w => w.Text);

Imports System
Imports System.Linq

Dim result = (New IronTesseract()).Read("scanned.jpg")
Console.WriteLine($"Confidence: {result.Confidence}%")

' Per-word confidence for fine-grained filtering
Dim highConfidenceWords = result.Words _
    .Where(Function(w) w.Confidence > 85) _
    .Select(Function(w) w.Text)

GdPicture requires three nested loops — blocks, lines, words — to reach the same data, with index-based method calls at each level (GetOCRResultBlockLineWordConfidence(resultId, b, l, w)). The confidence scores how-to demonstrates the structured access model for common use cases.

GdPicture Approach

GdPicture returns a resultId string from RunOCR(), and all result data is queried through that ID via method calls on the GdPictureOCR instance. Reaching per-word confidence requires iterating through three nested levels:

using GdPicture14;

public List<(string word, float confidence)> GetWordConfidences(int imageId)
{
    var words = new List<(string, float)>();

    _ocr.SetImage(imageId);
    _ocr.Language = "eng";
    string resultId = _ocr.RunOCR();

    int blockCount = _ocr.GetOCRResultBlockCount(resultId);

    for (int b = 0; b < blockCount; b++)
    {
        int lineCount = _ocr.GetOCRResultBlockLineCount(resultId, b);

        for (int l = 0; l < lineCount; l++)
        {
            int wordCount = _ocr.GetOCRResultBlockLineWordCount(resultId, b, l);

            for (int w = 0; w < wordCount; w++)
            {
                string word = _ocr.GetOCRResultBlockLineWordText(resultId, b, l, w);
                float conf = _ocr.GetOCRResultBlockLineWordConfidence(resultId, b, l, w);
                words.Add((word, conf));
            }
        }
    }

    return words;
}

using GdPicture14;

public List<(string word, float confidence)> GetWordConfidences(int imageId)
{
    var words = new List<(string, float)>();

    _ocr.SetImage(imageId);
    _ocr.Language = "eng";
    string resultId = _ocr.RunOCR();

    int blockCount = _ocr.GetOCRResultBlockCount(resultId);

    for (int b = 0; b < blockCount; b++)
    {
        int lineCount = _ocr.GetOCRResultBlockLineCount(resultId, b);

        for (int l = 0; l < lineCount; l++)
        {
            int wordCount = _ocr.GetOCRResultBlockLineWordCount(resultId, b, l);

            for (int w = 0; w < wordCount; w++)
            {
                string word = _ocr.GetOCRResultBlockLineWordText(resultId, b, l, w);
                float conf = _ocr.GetOCRResultBlockLineWordConfidence(resultId, b, l, w);
                words.Add((word, conf));
            }
        }
    }

    return words;
}

Imports GdPicture14

Public Function GetWordConfidences(imageId As Integer) As List(Of (word As String, confidence As Single))
    Dim words As New List(Of (String, Single))()

    _ocr.SetImage(imageId)
    _ocr.Language = "eng"
    Dim resultId As String = _ocr.RunOCR()

    Dim blockCount As Integer = _ocr.GetOCRResultBlockCount(resultId)

    For b As Integer = 0 To blockCount - 1
        Dim lineCount As Integer = _ocr.GetOCRResultBlockLineCount(resultId, b)

        For l As Integer = 0 To lineCount - 1
            Dim wordCount As Integer = _ocr.GetOCRResultBlockLineWordCount(resultId, b, l)

            For w As Integer = 0 To wordCount - 1
                Dim word As String = _ocr.GetOCRResultBlockLineWordText(resultId, b, l, w)
                Dim conf As Single = _ocr.GetOCRResultBlockLineWordConfidence(resultId, b, l, w)
                words.Add((word, conf))
            Next
        Next
    Next

    Return words
End Function

This is not wrong — the data is accessible. But it requires understanding and maintaining a three-dimensional index into the result structure for every project that needs word-level data.

IronOCR Approach

OcrResult exposes .Words as a typed collection. LINQ works directly against it:

using IronOcr;

var result = new IronTesseract().Read("invoice.jpg");

// All words with position and confidence
foreach (var word in result.Words)
{
    Console.WriteLine($"'{word.Text}' at ({word.X},{word.Y}) — {word.Confidence:P0}");
}

// Lines, paragraphs, and pages follow the same pattern
foreach (var line in result.Lines)
    Console.WriteLine(line.Text);

foreach (var page in result.Pages)
    Console.WriteLine($"Page {page.PageNumber}: {page.Text.Length} characters");

using IronOcr;

var result = new IronTesseract().Read("invoice.jpg");

// All words with position and confidence
foreach (var word in result.Words)
{
    Console.WriteLine($"'{word.Text}' at ({word.X},{word.Y}) — {word.Confidence:P0}");
}

// Lines, paragraphs, and pages follow the same pattern
foreach (var line in result.Lines)
    Console.WriteLine(line.Text);

foreach (var page in result.Pages)
    Console.WriteLine($"Page {page.PageNumber}: {page.Text.Length} characters");

Imports IronOcr

Dim result = New IronTesseract().Read("invoice.jpg")

' All words with position and confidence
For Each word In result.Words
    Console.WriteLine($"'{word.Text}' at ({word.X},{word.Y}) — {word.Confidence:P0}")
Next

' Lines, paragraphs, and pages follow the same pattern
For Each line In result.Lines
    Console.WriteLine(line.Text)
Next

For Each page In result.Pages
    Console.WriteLine($"Page {page.PageNumber}: {page.Text.Length} characters")
Next

Region-based OCR — extracting text from a defined rectangle of a document — is similarly direct:

var region = new CropRectangle(0, 0, 600, 100); // header area

using var input = new OcrInput();
input.LoadImage("invoice.jpg", region);

var headerText = new IronTesseract().Read(input).Text;

var region = new CropRectangle(0, 0, 600, 100); // header area

using var input = new OcrInput();
input.LoadImage("invoice.jpg", region);

var headerText = new IronTesseract().Read(input).Text;

Imports IronOcr

Dim region As New CropRectangle(0, 0, 600, 100) ' header area

Using input As New OcrInput()
    input.LoadImage("invoice.jpg", region)

    Dim headerText As String = New IronTesseract().Read(input).Text
End Using

The read results guide and region-based OCR guide show how these patterns extend to multi-page documents and structured field extraction workflows.

OCR Is the Only Requirement

Teams implementing document ingestion pipelines — intake of scanned invoices, processing of medical forms, extraction of contract text — often evaluate GdPicture because it appears in enterprise software directories alongside LEADTOOLS and Kofax. Once the plugin dependency table becomes clear, the picture changes. The PDF Plugin is not optional if PDF input is required. The Document Imaging Plugin is not optional if preprocessing is required. A team that needs OCR from scanned PDFs with deskew correction ends up with three plugin licenses at significant Professional entry cost. When the requirement is text extraction and nothing in the GdPicture feature list beyond that is needed, that pricing represents pure overhead. IronOCR at $2,999 Professional covers the identical workflow — image input, PDF input, preprocessing, searchable PDF output — from a single package with no plugin decisions to make.

Memory Leak Incidents in Production

The integer ID lifecycle becomes a production incident waiting to happen in high-throughput document processing services. A web API endpoint that processes uploaded PDFs under load will eventually have a code path where the image release call is not reached — an early return in an error branch, an unhandled exception before the cleanup block, or simply a new developer unfamiliar with the pattern adding a helper method that takes an integer image handle as a parameter and forgets to release it. The memory grows, the service slows, and the root cause is not obvious in a heap dump. Teams that have debugged one of these incidents typically want a model where the runtime handles cleanup. The standard disposal pattern in IronOCR is that model — structured cleanup enforced by the compiler rather than by developer discipline at every call site.

Version Upgrade Friction

GdPicture embeds the major version number in its namespace. An upgrade from version 14 to version 15 requires updating that namespace directive in every source file that references GdPicture classes. In a large application with OCR, PDF handling, and image processing spread across dozens of services and utility classes, that is a non-trivial migration task — and it provides no functional benefit. Every modern .NET library from Microsoft.EntityFrameworkCore to Newtonsoft.Json uses version-agnostic namespaces, managing versioning through the NuGet package version number instead. IronOCR follows that convention: the same namespace import applies from version 1 to the current release.

Microservice and Container Deployment

GdPicture OCR requires an external resource folder containing language data files to be present at a specific path at runtime. In a containerized deployment, that means either baking those files into the Docker image, mounting a volume, or configuring a startup script to download them. The typical result is a Docker image that is several hundred megabytes larger than necessary, a deployment checklist item that gets missed, and production failures on clean container restarts where the volume is not mounted. IronOCR bundles English support in the package itself; additional languages install as NuGet packages that are part of the build output. The container gets what it needs from the restore step, and there are no paths to configure. The Docker deployment guide and Linux deployment guide cover the specific configuration for each target environment.

Development Teams Without Document Imaging Expertise

GdPicture's surface area is large by necessity — it covers a full document imaging platform. For a developer joining a team to maintain an OCR microservice, understanding the imaging component, the OCR component, the PDF component, the integer ID lifecycle, status return code handling, and the resource folder configuration is a steep initial investment. IronOCR's surface area for OCR is three classes: the engine, the input container, and the result object. That is the entire mental model for 90% of use cases. Onboarding a new developer means pointing them at IronTesseract setup rather than at a multi-module SDK guide.

Replacing Component Initialization

GdPicture requires a four-step initialization sequence: register the license key through LicenseManager, initialize GdPictureImaging, initialize GdPictureOCR, and set the resource folder path. IronOCR reduces this to a single property assignment that belongs in Program.cs or Startup.cs:

// Remove
LicenseManager lm = new LicenseManager();
lm.RegisterKEY("GDPICTURE-LICENSE-KEY");
_imaging = new GdPictureImaging();
_ocr = new GdPictureOCR();
_ocr.ResourceFolder = @"C:\GdPicture\Resources\OCR";

// Replace with
IronOcr.License.LicenseKey = "IRONOCR-LICENSE-KEY";
// IronTesseract instances are instantiated per-use or as a singleton

// Remove
LicenseManager lm = new LicenseManager();
lm.RegisterKEY("GDPICTURE-LICENSE-KEY");
_imaging = new GdPictureImaging();
_ocr = new GdPictureOCR();
_ocr.ResourceFolder = @"C:\GdPicture\Resources\OCR";

// Replace with
IronOcr.License.LicenseKey = "IRONOCR-LICENSE-KEY";
// IronTesseract instances are instantiated per-use or as a singleton

' Remove
Dim lm As New LicenseManager()
lm.RegisterKEY("GDPICTURE-LICENSE-KEY")
_imaging = New GdPictureImaging()
_ocr = New GdPictureOCR()
_ocr.ResourceFolder = "C:\GdPicture\Resources\OCR"

' Replace with
IronOcr.License.LicenseKey = "IRONOCR-LICENSE-KEY"
' IronTesseract instances are instantiated per-use or as a singleton

Eliminating Image ID Tracking

Every CreateGdPictureImageFromFile call and every RenderPageToGdPictureImage call has a corresponding ReleaseGdPictureImage call somewhere in the existing codebase. Those cleanup calls are removed entirely in IronOCR — OcrInput handles disposal. The migration is mechanical: find each int imageId = ..., find its paired ReleaseGdPictureImage(imageId), wrap the loading code in using var input = new OcrInput(), and replace the GdPicture method calls with their IronOCR equivalents.

// Remove
int imageId = _imaging.CreateGdPictureImageFromFile(path);
if (imageId == 0) throw new Exception(_imaging.GetStat().ToString());
_ocr.SetImage(imageId);
_ocr.Language = "eng";
string resultId = _ocr.RunOCR();
if (string.IsNullOrEmpty(resultId)) throw new Exception(_ocr.GetStat().ToString());
string text = _ocr.GetOCRResultText(resultId);
_imaging.ReleaseGdPictureImage(imageId);

// Replace with
using var input = new OcrInput();
input.LoadImage(path);
var result = new IronTesseract().Read(input);
string text = result.Text;

// Remove
int imageId = _imaging.CreateGdPictureImageFromFile(path);
if (imageId == 0) throw new Exception(_imaging.GetStat().ToString());
_ocr.SetImage(imageId);
_ocr.Language = "eng";
string resultId = _ocr.RunOCR();
if (string.IsNullOrEmpty(resultId)) throw new Exception(_ocr.GetStat().ToString());
string text = _ocr.GetOCRResultText(resultId);
_imaging.ReleaseGdPictureImage(imageId);

// Replace with
using var input = new OcrInput();
input.LoadImage(path);
var result = new IronTesseract().Read(input);
string text = result.Text;

Imports System

' Remove
Dim imageId As Integer = _imaging.CreateGdPictureImageFromFile(path)
If imageId = 0 Then Throw New Exception(_imaging.GetStat().ToString())
_ocr.SetImage(imageId)
_ocr.Language = "eng"
Dim resultId As String = _ocr.RunOCR()
If String.IsNullOrEmpty(resultId) Then Throw New Exception(_ocr.GetStat().ToString())
Dim text As String = _ocr.GetOCRResultText(resultId)
_imaging.ReleaseGdPictureImage(imageId)

' Replace with
Using input As New OcrInput()
    input.LoadImage(path)
    Dim result = New IronTesseract().Read(input)
    Dim text As String = result.Text
End Using

Adapting Error Handling

GdPicture uses GdPictureStatus return codes checked after every significant operation. IronOCR throws standard .NET exceptions. The migration replaces if (status != GdPictureStatus.OK) guards with try/catch blocks that handle IronOcr.Exceptions.OcrException for OCR-specific failures and standard IOException and FileNotFoundException for input failures. The reading text from images tutorial covers error handling patterns for common scenarios.

Language Pack Deployment

GdPicture language files are .traineddata files in a filesystem folder. IronOCR language packs are NuGet packages. The migration removes the resource folder from the deployment manifest and adds NuGet package references for each required language:

# Remove filesystem dependency for each language
# Add NuGet package instead
dotnet add package IronOcr.Languages.French
dotnet add package IronOcr.Languages.German
dotnet add package IronOcr.Languages.ChineseSimplified

# Remove filesystem dependency for each language
# Add NuGet package instead
dotnet add package IronOcr.Languages.French
dotnet add package IronOcr.Languages.German
dotnet add package IronOcr.Languages.ChineseSimplified

The multiple languages guide covers configuration for multi-language documents where both primary and secondary languages are specified on the IronTesseract instance.