' Required assemblies to run this code:
' Vintasoft.Imaging.dll, Vintasoft.Imaging.Ocr.dll, Vintasoft.Imaging.Ocr.Tesseract.dll,
' Vintasoft.Imaging.Pdf.dll, Vintasoft.Imaging.Pdf.Ocr.dll, Vintasoft.Imaging.Pdf.Mrc.dll,
' Vintasoft.Imaging.Jbig2.dll, Vintasoft.Imaging.Jpeg2000.dll
Public Shared Sub ConvertToSearchablePdfWithMrcCompression(language As Vintasoft.Imaging.Ocr.OcrLanguage, images As Vintasoft.Imaging.ImageCollection, mrcResolution As Vintasoft.Imaging.Resolution, ocrResolution As Vintasoft.Imaging.Resolution, pdfFilename As String)
    ' create PDF MRC encoder
    Dim encoder As New Vintasoft.Imaging.Codecs.Encoders.PdfMrcEncoder()

    ' set MRC compression settings
    SetSetting_DocumentWithImagesHiQuality(encoder.MrcCompressionSettings)

    ' set MRC resolution (if source is PDF document)
    images.SetRenderingSettings(New Vintasoft.Imaging.Codecs.Decoders.RenderingSettings(mrcResolution))

    ' handle ImageSaving event to set JBIG2 compression for black-white images
    AddHandler encoder.ImageSaving, New System.EventHandler(Of Vintasoft.Imaging.ImageSavingEventArgs)(AddressOf images_ImageSaving)

    ' save images to PDF use MRC compression
    System.Console.WriteLine("Encoding using PDF MRC compression...")
    images.SaveSync(pdfFilename, encoder)

    ' open PDF document with MRC compression
    Using document As New Vintasoft.Imaging.Pdf.PdfDocument(pdfFilename, False)
        System.Console.WriteLine("Create Tesseract OCR engine...")
        Using tesseractOcr As New Vintasoft.Imaging.Ocr.Tesseract.TesseractOcr()
            System.Console.WriteLine("Initialize OCR engine...")
            tesseractOcr.Init(New Vintasoft.Imaging.Ocr.OcrEngineSettings(language))

            ' create PDF document builder
            Dim documentBuilder As New Vintasoft.Imaging.Pdf.Ocr.PdfDocumentBuilder(document)

            ' set OCR resolution (if source is PDF document)
            images.SetRenderingSettings(New Vintasoft.Imaging.Codecs.Decoders.RenderingSettings(ocrResolution))

            ' foreach image
            For i As Integer = 0 To images.Count - 1
                System.Console.WriteLine("Recognize image...")
                Dim page As Vintasoft.Imaging.Ocr.Results.OcrPage = tesseractOcr.Recognize(images(i))

                System.Console.WriteLine("Set PDF page background...")
                documentBuilder.SetAsBackground(i, page)
            Next

            ' shutdown OCR engine
            tesseractOcr.Shutdown()

            System.Console.WriteLine("Pack PDF document...")
            document.Pack()
            System.Console.WriteLine("OK.")
        End Using
    End Using
End Sub

''' <summary>
''' Handles the ImageSaving event of the image collection.
''' </summary>
Private Shared Sub images_ImageSaving(sender As Object, e As Vintasoft.Imaging.ImageSavingEventArgs)
    Dim encoder As Vintasoft.Imaging.Codecs.Encoders.PdfMrcEncoder = TryCast(sender, Vintasoft.Imaging.Codecs.Encoders.PdfMrcEncoder)
    ' set JBIG2 compression for black-white images
    Dim isBlackWhiteImage As Boolean = e.Image.PixelFormat = Vintasoft.Imaging.PixelFormat.BlackWhite
    If Not isBlackWhiteImage Then
        Dim page As Vintasoft.Imaging.Pdf.Tree.PdfPage = Vintasoft.Imaging.Pdf.PdfDocumentController.GetPageAssociatedWithImage(e.Image)
        If page IsNot Nothing AndAlso page.BackgroundImage IsNot Nothing Then
            isBlackWhiteImage = page.BackgroundImage.PixelFormat = Vintasoft.Imaging.PixelFormat.BlackWhite
        End If
        If isBlackWhiteImage Then
            e.Image.RenderingSettings.Resolution = page.DefaultResolution
        End If
    End If
    If isBlackWhiteImage Then
        encoder.MrcCompressionSettings.EnableMrcCompression = False
        encoder.Settings.Compression = Vintasoft.Imaging.Codecs.Encoders.PdfImageCompression.Jbig2
        System.Console.WriteLine(String.Format("Encoding image {0} using JBIG2 compression...", e.Image.SourceInfo.PageIndex))
    Else
        encoder.MrcCompressionSettings.EnableMrcCompression = True
        System.Console.WriteLine(String.Format("Encoding image {0} using MRC compression...", e.Image.SourceInfo.PageIndex))
    End If
End Sub

''' <summary>
''' Sets MRC compression settings to compress the document
''' images, which contain text and pictures, using MRC compression
''' algorithm and get the resulting images with high quality.
''' </summary>
Public Shared Sub SetSetting_DocumentWithImagesHiQuality(settings As Vintasoft.Imaging.Codecs.Encoders.PdfMrcCompressionSettings)
    settings.CreateBackgroundLayer = True
    settings.BackgroundLayerCompression = Vintasoft.Imaging.Pdf.PdfCompression.Jpeg Or Vintasoft.Imaging.Pdf.PdfCompression.Zip
    settings.BackgroundLayerCompressionSettings.JpegQuality = 60

    settings.ImageSegmentation = New Vintasoft.Imaging.ImageProcessing.Info.ImageSegmentationCommand()
    settings.CreateImagesLayer = False

    settings.HiQualityMask = True
    settings.MaskCompression = Vintasoft.Imaging.Pdf.PdfCompression.Jbig2
    settings.MaskCompressionSettings.Jbig2Settings.Lossy = True

    settings.CreateFrontLayer = True
    settings.HiQualityFrontLayer = True
    settings.FrontLayerCompression = Vintasoft.Imaging.Pdf.PdfCompression.Jpeg2000
    settings.FrontLayerCompressionSettings.Jpeg2000Settings.CompressionRatio = 300 * 3
    settings.FrontLayerCompressionSettings.Jpeg2000Settings.CompressionType = Vintasoft.Imaging.Codecs.ImageFiles.Jpeg2000.Jpeg2000CompressionType.Lossy
End Sub

// Required assemblies to run this code:
// Vintasoft.Imaging.dll, Vintasoft.Imaging.Ocr.dll, Vintasoft.Imaging.Ocr.Tesseract.dll,
// Vintasoft.Imaging.Pdf.dll, Vintasoft.Imaging.Pdf.Ocr.dll, Vintasoft.Imaging.Pdf.Mrc.dll,
// Vintasoft.Imaging.Jbig2.dll, Vintasoft.Imaging.Jpeg2000.dll
public static void ConvertToSearchablePdfWithMrcCompression(
    Vintasoft.Imaging.Ocr.OcrLanguage language,
    Vintasoft.Imaging.ImageCollection images,
    Vintasoft.Imaging.Resolution mrcResolution,
    Vintasoft.Imaging.Resolution ocrResolution,
    string pdfFilename)
{
    // create PDF MRC encoder
    Vintasoft.Imaging.Codecs.Encoders.PdfMrcEncoder encoder =
        new Vintasoft.Imaging.Codecs.Encoders.PdfMrcEncoder();

    // set MRC compression settings
    SetSetting_DocumentWithImagesHiQuality(encoder.MrcCompressionSettings);

    // set MRC resolution (if source is PDF document)
    images.SetRenderingSettings(new Vintasoft.Imaging.Codecs.Decoders.RenderingSettings(mrcResolution));

    // handle ImageSaving event to set JBIG2 compression for black-white images
    encoder.ImageSaving +=
        new System.EventHandler<Vintasoft.Imaging.ImageSavingEventArgs>(images_ImageSaving);

    // save images to PDF use MRC compression
    System.Console.WriteLine("Encoding using PDF MRC compression...");
    images.SaveSync(pdfFilename, encoder);

    // open PDF document with MRC compression
    using (Vintasoft.Imaging.Pdf.PdfDocument document = new Vintasoft.Imaging.Pdf.PdfDocument(pdfFilename, false))
    {
        System.Console.WriteLine("Create Tesseract OCR engine...");
        using (Vintasoft.Imaging.Ocr.Tesseract.TesseractOcr tesseractOcr =
            new Vintasoft.Imaging.Ocr.Tesseract.TesseractOcr())
        {
            System.Console.WriteLine("Initialize OCR engine...");
            tesseractOcr.Init(new Vintasoft.Imaging.Ocr.OcrEngineSettings(language));

            // create PDF document builder
            Vintasoft.Imaging.Pdf.Ocr.PdfDocumentBuilder documentBuilder =
                new Vintasoft.Imaging.Pdf.Ocr.PdfDocumentBuilder(document);

            // set OCR resolution (if source is PDF document)
            images.SetRenderingSettings(new Vintasoft.Imaging.Codecs.Decoders.RenderingSettings(ocrResolution));

            // foreach image
            for (int i = 0; i < images.Count; i++)
            {
                System.Console.WriteLine("Recognize image...");
                Vintasoft.Imaging.Ocr.Results.OcrPage page = tesseractOcr.Recognize(images[i]);

                System.Console.WriteLine("Set PDF page background...");
                documentBuilder.SetAsBackground(i, page);
            }

            // shutdown OCR engine
            tesseractOcr.Shutdown();

            System.Console.WriteLine("Pack PDF document...");
            document.Pack();
            System.Console.WriteLine("OK.");
        }
    }
}

/// <summary>
/// Handles the ImageSaving event of the image collection.
/// </summary>
private static void images_ImageSaving(object sender, Vintasoft.Imaging.ImageSavingEventArgs e)
{
    Vintasoft.Imaging.Codecs.Encoders.PdfMrcEncoder encoder =
        sender as Vintasoft.Imaging.Codecs.Encoders.PdfMrcEncoder;
    // set JBIG2 compression for black-white images
    bool isBlackWhiteImage = e.Image.PixelFormat == Vintasoft.Imaging.PixelFormat.BlackWhite;
    if (!isBlackWhiteImage)
    {
        Vintasoft.Imaging.Pdf.Tree.PdfPage page =
            Vintasoft.Imaging.Pdf.PdfDocumentController.GetPageAssociatedWithImage(e.Image);
        if (page != null && page.BackgroundImage != null)
            isBlackWhiteImage = page.BackgroundImage.PixelFormat == Vintasoft.Imaging.PixelFormat.BlackWhite;
        if (isBlackWhiteImage)
            e.Image.RenderingSettings.Resolution = page.DefaultResolution;
    }
    if (isBlackWhiteImage)
    {
        encoder.MrcCompressionSettings.EnableMrcCompression = false;
        encoder.Settings.Compression = Vintasoft.Imaging.Codecs.Encoders.PdfImageCompression.Jbig2;
        System.Console.WriteLine(string.Format("Encoding image {0} using JBIG2 compression...", e.Image.SourceInfo.PageIndex));
    }
    else
    {
        encoder.MrcCompressionSettings.EnableMrcCompression = true;
        System.Console.WriteLine(string.Format("Encoding image {0} using MRC compression...", e.Image.SourceInfo.PageIndex));
    }
}

/// <summary>
/// Sets MRC compression settings to compress the document
/// images, which contain text and pictures, using MRC compression
/// algorithm and get the resulting images with high quality.
/// </summary>
public static void SetSetting_DocumentWithImagesHiQuality(
    Vintasoft.Imaging.Codecs.Encoders.PdfMrcCompressionSettings settings)
{
    settings.CreateBackgroundLayer = true;
    settings.BackgroundLayerCompression =
        Vintasoft.Imaging.Pdf.PdfCompression.Jpeg |
        Vintasoft.Imaging.Pdf.PdfCompression.Zip;
    settings.BackgroundLayerCompressionSettings.JpegQuality = 60;

    settings.ImageSegmentation =
        new Vintasoft.Imaging.ImageProcessing.Info.ImageSegmentationCommand();
    settings.CreateImagesLayer = false;

    settings.HiQualityMask = true;
    settings.MaskCompression =
        Vintasoft.Imaging.Pdf.PdfCompression.Jbig2;
    settings.MaskCompressionSettings.Jbig2Settings.Lossy = true;

    settings.CreateFrontLayer = true;
    settings.HiQualityFrontLayer = true;
    settings.FrontLayerCompression =
        Vintasoft.Imaging.Pdf.PdfCompression.Jpeg2000;
    settings.FrontLayerCompressionSettings.Jpeg2000Settings.CompressionRatio = 300 * 3;
    settings.FrontLayerCompressionSettings.Jpeg2000Settings.CompressionType =
        Vintasoft.Imaging.Codecs.ImageFiles.Jpeg2000.Jpeg2000CompressionType.Lossy;
}