Bild aus PDF mit itextsharp extrahieren

Question

Ich versuche, alle Bilder aus einem PDF-Dokument mit itextsharp zu extrahieren, aber ich kann diese eine Hürde nicht überwinden.

Der Fehler tritt in der folgenden Zeile auf System.Drawing.Image ImgPDF = System.Drawing.Image.FromStream(MS); mit der Fehlermeldung "Parameter ist nicht gültig".

Ich glaube, es funktioniert, wenn das Bild ein Bitmap ist, aber nicht in einem anderen Format.

Ich habe den folgenden Code - entschuldigen Sie die Länge;

    private void Form1_Load(object sender, EventArgs e)
    {
        FileStream fs = File.OpenRead(@"reader.pdf");
        byte[] data = new byte[fs.Length];
        fs.Read(data, 0, (int)fs.Length);

        List<System.Drawing.Image> ImgList = new List<System.Drawing.Image>();

        iTextSharp.text.pdf.RandomAccessFileOrArray RAFObj = null;
        iTextSharp.text.pdf.PdfReader PDFReaderObj = null;
        iTextSharp.text.pdf.PdfObject PDFObj = null;
        iTextSharp.text.pdf.PdfStream PDFStremObj = null;

        try
        {
            RAFObj = new iTextSharp.text.pdf.RandomAccessFileOrArray(data);
            PDFReaderObj = new iTextSharp.text.pdf.PdfReader(RAFObj, null);

            for (int i = 0; i <= PDFReaderObj.XrefSize - 1; i++)
            {
                PDFObj = PDFReaderObj.GetPdfObject(i);

                if ((PDFObj != null) && PDFObj.IsStream())
                {
                    PDFStremObj = (iTextSharp.text.pdf.PdfStream)PDFObj;
                    iTextSharp.text.pdf.PdfObject subtype = PDFStremObj.Get(iTextSharp.text.pdf.PdfName.SUBTYPE);

                    if ((subtype != null) && subtype.ToString() == iTextSharp.text.pdf.PdfName.IMAGE.ToString())
                    {
                        byte[] bytes = iTextSharp.text.pdf.PdfReader.GetStreamBytesRaw((iTextSharp.text.pdf.PRStream)PDFStremObj);

                        if ((bytes != null))
                        {
                            try
                            {
                                System.IO.MemoryStream MS = new System.IO.MemoryStream(bytes);

                                MS.Position = 0;
                                System.Drawing.Image ImgPDF = System.Drawing.Image.FromStream(MS);

                                ImgList.Add(ImgPDF);

                            }
                            catch (Exception)
                            {
                            }
                        }
                    }
                }
            }
            PDFReaderObj.Close();
        }
        catch (Exception ex)
        {
            throw new Exception(ex.Message);
        }

    } //Form1_Load

Answer 1

Ich habe eine Bibliothek auf Github hinzugefügt, die Bilder in PDF extrahiert und komprimiert.

Könnte nützlich sein, wenn Sie anfangen, mit der sehr leistungsfähigen Bibliothek ITextSharp zu spielen.

Hier der Link: https://github.com/rock-walker/PdfCompression

Answer 2

Das funktioniert bei mir, und ich denke, es ist eine einfache Lösung:

Schreiben Sie einen benutzerdefinierten RenderListener und implementieren Sie dessen RenderImage-Methode, etwa wie folgt

    public void RenderImage(ImageRenderInfo info)
    {
        PdfImageObject image = info.GetImage();
        Parser.Matrix matrix = info.GetImageCTM();
        var fileType = image.GetFileType();
        ImageFormat format;
        switch (fileType)
        {//you may add more types here
            case "jpg":
            case "jpeg":
                format = ImageFormat.Jpeg;
                break;
            case "pnt":
                format = ImageFormat.Png;
                break;
            case "bmp":
                format = ImageFormat.Bmp;
                break;
            case "tiff":
                format = ImageFormat.Tiff;
                break;
            case "gif":
                format = ImageFormat.Gif;
                break;
            default:
                format = ImageFormat.Jpeg;
                break;
        }

        var pic = image.GetDrawingImage();
        var x = matrix[Parser.Matrix.I31];
        var y = matrix[Parser.Matrix.I32];
        var width = matrix[Parser.Matrix.I11];
        var height = matrix[Parser.Matrix.I22];
        if (x < <some value> && y < <some value>)
        {
            return;//ignore these images
        }

        pic.Save(<path and name>, format);
}

Answer 3

Ich habe diese Bibliothek in der Vergangenheit ohne Probleme verwendet.

http://www.winnovative-software.com/PdfImgExtractor.aspx

private void btnExtractImages_Click(object sender, EventArgs e)
{
    if (pdfFileTextBox.Text.Trim().Equals(String.Empty))
    {
        MessageBox.Show("Please choose a source PDF file", "Choose PDF file", MessageBoxButtons.OK);
        return;
    }

    // the source pdf file
    string pdfFileName = pdfFileTextBox.Text.Trim();

    // start page number
    int startPageNumber = int.Parse(textBoxStartPage.Text.Trim());
    // end page number
    // when it is 0 the extraction will continue up to the end of document
    int endPageNumber = 0;
    if (textBoxEndPage.Text.Trim() != String.Empty)
        endPageNumber = int.Parse(textBoxEndPage.Text.Trim());

    // create the PDF images extractor object
    PdfImagesExtractor pdfImagesExtractor = new PdfImagesExtractor();

    pdfImagesExtractor.LicenseKey = "31FAUEJHUEBQRl5AUENBXkFCXklJSUlQQA==";

    // the demo output directory
    string outputDirectory = Path.Combine(Application.StartupPath, @"DemoFiles\Output");

    Cursor = Cursors.WaitCursor;

    // set the handler to be called when an image was extracted
    pdfImagesExtractor.ImageExtractedEvent += pdfImagesExtractor_ImageExtractedEvent;

    try
    {
        // start images counting
        imageIndex = 0;

        // call the images extractor to raise the ImageExtractedEvent event when an images is extracted from a PDF page
        // the pdfImagesExtractor_ImageExtractedEvent handler below will be executed for each extracted image
        pdfImagesExtractor.ExtractImagesInEvent(pdfFileName, startPageNumber, endPageNumber);

        // Alternatively you can use the ExtractImages() and ExtractImagesToFile() methods
        // to extracted the images from a PDF document in memory or to image files in a directory

        // uncomment the line below to extract the images to an array of ExtractedImage objects
        //ExtractedImage[] pdfPageImages = pdfImagesExtractor.ExtractImages(pdfFileName, startPageNumber, endPageNumber);

        // uncomment the lines below to extract the images to image files in a directory
        //string outputDirectory = System.IO.Path.Combine(Application.StartupPath, @"DemoFiles\Output");
        //pdfImagesExtractor.ExtractImagesToFile(pdfFileName, startPageNumber, endPageNumber, outputDirectory, "pdfimage");
    }
    catch (Exception ex)
    {
        // The extraction failed
        MessageBox.Show(String.Format("An error occurred. {0}", ex.Message), "Error");
        return;
    }
    finally
    {
        // uninstall the event handler
        pdfImagesExtractor.ImageExtractedEvent -= pdfImagesExtractor_ImageExtractedEvent;

        Cursor = Cursors.Arrow;
    }

    try
    {
        System.Diagnostics.Process.Start(outputDirectory);
    }
    catch (Exception ex)
    {
        MessageBox.Show(string.Format("Cannot open output folder. {0}", ex.Message));
        return;
    }
}

/// <summary>
/// The ImageExtractedEvent event handler called after an image was extracted from a PDF page.
/// The event is raised when the ExtractImagesInEvent() method is used
/// </summary>
/// <param name="args">The handler argument containing the extracted image and the PDF page number</param>
void pdfImagesExtractor_ImageExtractedEvent(ImageExtractedEventArgs args)
{
    // get the image object and page number from even handler argument
    Image pdfPageImageObj = args.ExtractedImage.ImageObject;
    int pageNumber = args.ExtractedImage.PageNumber;

    // save the extracted image to a PNG file
    string outputPageImage = Path.Combine(Application.StartupPath, @"DemoFiles\Output", 
        "pdfimage_" + pageNumber.ToString() + "_" + imageIndex++ + ".png");
    pdfPageImageObj.Save(outputPageImage, ImageFormat.Png);

    args.ExtractedImage.Dispose();
}