/// <summary>
/// Converts an image file to a searchable PDF document.
/// </summary>
/// <param name="sourceFilePath">A filename of source image file.</param>
/// <param name="pageCreationMode">The PDF page creation mode.</param>
/// <param name="ocrLanguage">An OCR language that should be used for text recognition.</param>
/// <param name="pdfFilename">A filename of destination PDF file.</param>
public static void ConvertImagesToSearchablePdf(
    string sourceFilePath,
    Vintasoft.Imaging.Pdf.Ocr.PdfPageCreationMode pageCreationMode,
    Vintasoft.Imaging.Ocr.OcrLanguage ocrLanguage,
    string pdfFilename)
{
    // create image collection
    using (Vintasoft.Imaging.ImageCollection images = new Vintasoft.Imaging.ImageCollection())
    {
        // add images to the image collection
        images.Add(sourceFilePath);

        try
        {
            // create Tesseract OCR engine
            using (Vintasoft.Imaging.Ocr.Tesseract.TesseractOcr tesseractOcrEngine = new Vintasoft.Imaging.Ocr.Tesseract.TesseractOcr())
            {
                // create OCR engine manager
                Vintasoft.Imaging.Ocr.OcrEngineManager ocrEngineManager = new Vintasoft.Imaging.Ocr.OcrEngineManager(tesseractOcrEngine);

                // create PDF generator
                Vintasoft.Imaging.Pdf.Ocr.SearchablePdfGenerator pdfGenerator = new Vintasoft.Imaging.Pdf.Ocr.SearchablePdfGenerator(ocrEngineManager);

                // set source images in PDF generator
                pdfGenerator.SourceImages = images;
                // set PDF page creation mode in PDF generator
                pdfGenerator.PageCreationMode = pageCreationMode;

                // create Tesseract OCR settings
                Vintasoft.Imaging.Ocr.Tesseract.TesseractOcrSettings tesseractOcrSettings = new Vintasoft.Imaging.Ocr.Tesseract.TesseractOcrSettings(ocrLanguage);
                tesseractOcrSettings.RecognitionRegionType =
                    Vintasoft.Imaging.Ocr.RecognitionRegionType.RecognizePageWithPageSegmentationAndOrientationDetection;

                // if PDF pages must be created in "TextOverImage" mode
                if (pageCreationMode == Vintasoft.Imaging.Pdf.Ocr.PdfPageCreationMode.TextOverImage)
                    tesseractOcrSettings.UseSymbolRegionsCorrection = true;
                else
                    tesseractOcrSettings.UseSymbolRegionsCorrection = false;

                // set Tesseract OCR settings
                pdfGenerator.OcrEngineSettings = tesseractOcrSettings;

                // if PDF pages must be created in "Text" mode
                if (pageCreationMode == Vintasoft.Imaging.Pdf.Ocr.PdfPageCreationMode.Text)
                {
                    // set text color
                    pdfGenerator.TextColor = System.Drawing.Color.Black;
                    // text text font name
                    pdfGenerator.TextOnlyFontName = "Arial";
                }

                // subscribe to the PDF page added event for saving changes to PDF document
                pdfGenerator.PdfPageAdded += Command_PdfPageAdded;
                // subscribe to the image processing started event for preprocessing image
                pdfGenerator.ImageProcessingStarted += PdfGenerator_ImageProcessingStarted;

                // create PDF document
                using (Vintasoft.Imaging.Pdf.PdfDocument document = new Vintasoft.Imaging.Pdf.PdfDocument(
                    pdfFilename, System.IO.FileMode.Create, Vintasoft.Imaging.Pdf.PdfFormat.Pdf_16))
                {
                    // generate PDF document pages
                    pdfGenerator.Execute(document);

                    // save PDF document
                    document.SaveChanges();
                }
            }
        }
        finally
        {
            // remove images
            images.ClearAndDisposeItems();
        }
    }
}

/// <summary>
/// Handles the <see cref="Vintasoft.Imaging.Pdf.Ocr.SearchablePdfGenerator.ImageProcessingStarted"/> event.
/// </summary>
private static void PdfGenerator_ImageProcessingStarted(object sender, Vintasoft.Imaging.Pdf.Ocr.OcrImageProcessingEventArgs e)
{
    // create image copy
    Vintasoft.Imaging.VintasoftImage image = (Vintasoft.Imaging.VintasoftImage)e.Image.Clone();

    try
    {
        // preprocess image

        Vintasoft.Imaging.ImageProcessing.Document.DeskewCommand deskewCommand =
            new Vintasoft.Imaging.ImageProcessing.Document.DeskewCommand();
        deskewCommand.ExecuteInPlace(image);

        Vintasoft.Imaging.ImageProcessing.Document.AutoTextOrientationCommand autoTextOrientationCommand =
            new Vintasoft.Imaging.ImageProcessing.Document.AutoTextOrientationCommand();
        autoTextOrientationCommand.ExecuteInPlace(image);

        // change the processing image (the processing command will dispose image after use)
        e.Image = image;
    }
    catch
    {
        image.Dispose();

        // skip image
        e.Image = null;
    }
}

/// <summary>
/// Handles the <see cref="Vintasoft.Imaging.Pdf.Ocr.SearchablePdfGenerator.PdfPageAdded"/> event.
/// </summary>
private static void Command_PdfPageAdded(object sender, Vintasoft.Imaging.Pdf.Ocr.PdfPageAddedEventArgs e)
{
    // save PDF document every 10 pages

    if (e.Document.Pages.Count % 10 == 0)
        e.Document.SaveChanges();
}

''' <summary>
''' Converts an image file to a searchable PDF document.
''' </summary>
''' <param name="sourceFilePath">A filename of source image file.</param>
''' <param name="pageCreationMode">The PDF page creation mode.</param>
''' <param name="ocrLanguage">An OCR language that should be used for text recognition.</param>
''' <param name="pdfFilename">A filename of destination PDF file.</param>
Public Shared Sub ConvertImagesToSearchablePdf(sourceFilePath As String, pageCreationMode As Vintasoft.Imaging.Pdf.Ocr.PdfPageCreationMode, ocrLanguage As Vintasoft.Imaging.Ocr.OcrLanguage, pdfFilename As String)
    ' create image collection
    Using images As New Vintasoft.Imaging.ImageCollection()
        ' add images to the image collection
        images.Add(sourceFilePath)

        Try
            ' create Tesseract OCR engine
            Using tesseractOcrEngine As New Vintasoft.Imaging.Ocr.Tesseract.TesseractOcr()
                ' create OCR engine manager
                Dim ocrEngineManager As New Vintasoft.Imaging.Ocr.OcrEngineManager(tesseractOcrEngine)

                ' create PDF generator
                Dim pdfGenerator As New Vintasoft.Imaging.Pdf.Ocr.SearchablePdfGenerator(ocrEngineManager)

                ' set source images in PDF generator
                pdfGenerator.SourceImages = images
                ' set PDF page creation mode in PDF generator
                pdfGenerator.PageCreationMode = pageCreationMode

                ' create Tesseract OCR settings
                Dim tesseractOcrSettings As New Vintasoft.Imaging.Ocr.Tesseract.TesseractOcrSettings(ocrLanguage)
                tesseractOcrSettings.RecognitionRegionType = Vintasoft.Imaging.Ocr.RecognitionRegionType.RecognizePageWithPageSegmentationAndOrientationDetection

                ' if PDF pages must be created in "TextOverImage" mode
                If pageCreationMode = Vintasoft.Imaging.Pdf.Ocr.PdfPageCreationMode.TextOverImage Then
                    tesseractOcrSettings.UseSymbolRegionsCorrection = True
                Else
                    tesseractOcrSettings.UseSymbolRegionsCorrection = False
                End If

                ' set Tesseract OCR settings
                pdfGenerator.OcrEngineSettings = tesseractOcrSettings

                ' if PDF pages must be created in "Text" mode
                If pageCreationMode = Vintasoft.Imaging.Pdf.Ocr.PdfPageCreationMode.Text Then
                    ' set text color
                    pdfGenerator.TextColor = System.Drawing.Color.Black
                    ' text text font name
                    pdfGenerator.TextOnlyFontName = "Arial"
                End If

                ' subscribe to the PDF page added event for saving changes to PDF document
                AddHandler pdfGenerator.PdfPageAdded, AddressOf Command_PdfPageAdded
                ' subscribe to the image processing started event for preprocessing image
                AddHandler pdfGenerator.ImageProcessingStarted, AddressOf PdfGenerator_ImageProcessingStarted

                ' create PDF document
                Using document As New Vintasoft.Imaging.Pdf.PdfDocument(pdfFilename, System.IO.FileMode.Create, Vintasoft.Imaging.Pdf.PdfFormat.Pdf_16)
                    ' generate PDF document pages
                    pdfGenerator.Execute(document)

                    ' save PDF document
                    document.SaveChanges()
                End Using
            End Using
        Finally
            ' remove images
            images.ClearAndDisposeItems()
        End Try
    End Using
End Sub

''' <summary>
''' Handles the <see cref="Vintasoft.Imaging.Pdf.Ocr.SearchablePdfGenerator.ImageProcessingStarted"/> event.
''' </summary>
Private Shared Sub PdfGenerator_ImageProcessingStarted(sender As Object, e As Vintasoft.Imaging.Pdf.Ocr.OcrImageProcessingEventArgs)
    ' create image copy
    Dim image As Vintasoft.Imaging.VintasoftImage = DirectCast(e.Image.Clone(), Vintasoft.Imaging.VintasoftImage)

    Try
        ' preprocess image

        Dim deskewCommand As New Vintasoft.Imaging.ImageProcessing.Document.DeskewCommand()
        deskewCommand.ExecuteInPlace(image)

        Dim autoTextOrientationCommand As New Vintasoft.Imaging.ImageProcessing.Document.AutoTextOrientationCommand()
        autoTextOrientationCommand.ExecuteInPlace(image)

        ' change the processing image (the processing command will dispose image after use)
        e.Image = image
    Catch
        image.Dispose()

        ' skip image
        e.Image = Nothing
    End Try
End Sub

''' <summary>
''' Handles the <see cref="Vintasoft.Imaging.Pdf.Ocr.SearchablePdfGenerator.PdfPageAdded"/> event.
''' </summary>
Private Shared Sub Command_PdfPageAdded(sender As Object, e As Vintasoft.Imaging.Pdf.Ocr.PdfPageAddedEventArgs)
    ' save PDF document every 10 pages

    If e.Document.Pages.Count Mod 10 = 0 Then
        e.Document.SaveChanges()
    End If
End Sub