使用 itextsharp 从 PDF 中提取图像 [英] Extract image from PDF using itextsharp

问题描述

我正在尝试使用 itextsharp 从 pdf 中提取所有图像，但似乎无法克服这一障碍.

I am trying to extract all the images from a pdf using itextsharp but can't seem to overcome this one hurdle.

错误发生在行 System.Drawing.Image ImgPDF = System.Drawing.Image.FromStream(MS); 给出参数无效"的错误.

The error occures on the line System.Drawing.Image ImgPDF = System.Drawing.Image.FromStream(MS); giving an error of "Parameter is not valid".

我认为当图像是位图而不是任何其他格式时它可以工作.

I think it works when the image is a bitmap but not of any other format.

我有以下代码 - 抱歉长度太长；

I have this following code - sorry for the length;

    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

推荐答案

我过去使用过这个库没有任何问题.

I have used this library in the past without any problems.

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, @"DemoFilesOutput");

    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, @"DemoFilesOutput");
        //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, @"DemoFilesOutput", 
        "pdfimage_" + pageNumber.ToString() + "_" + imageIndex++ + ".png");
    pdfPageImageObj.Save(outputPageImage, ImageFormat.Png);

    args.ExtractedImage.Dispose();
}

这篇关于使用 itextsharp 从 PDF 中提取图像的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！