合并多个 Pdf 文件时出现 Pdfsharp 内存不足异常

Question

I have to convert into a single pdf a large number (but undefined) pdf into one for this, I'm using the code PDFsharp here.

    // Get some file names
    string[] files = filesToPrint.ToArray();

    // Open the output document
    PdfDocument outputDocument = new PdfDocument();

    PdfPage newPage; 

    int nProcessedFile = 0;
    int nMemoryFile = 5;
    int nStepConverted = 0;
    String sNameLastCombineFile = ""; 


    // Iterate files
    foreach (string file in files)
    {
        // Open the document to import pages from it.
        PdfDocument inputDocument = PdfReader.Open(file, PdfDocumentOpenMode.Import);

        // Iterate pages
        int count = inputDocument.PageCount;
        for (int idx = 0; idx < count; idx++)
        {
            // Get the page from the external document...
            PdfPage page = inputDocument.Pages[idx];
            // ...and add it to the output document.
            outputDocument.AddPage(page);                                
        }

        nProcessedFile++;
        if (nProcessedFile >= nMemoryFile)
        {
            //nProcessedFile = 0;
            //nStepConverted++;
            //sNameLastCombineFile = "ConcatenatedDocument" + nStepConverted.ToString() + " _tempfile.pdf";

            //outputDocument.Save(sNameLastCombineFile);
            //outputDocument.Close();                 
        }
    }
    // Save the document...
    const string filename = "ConcatenatedDocument1_tempfile.pdf";
    outputDocument.Save(filename);
    // ...and start a viewer.
   Process.Start(filename);

For small numbers of files the code works but then at some point generates an exception of out of memory

is there a solution?

ps I was thinking of saving the files in step and then the remaining aggiungingere so liebrare memory but I can not find the way.

UPDATE1:

if (nProcessedFile >= nMemoryFile)
{
nProcessedFile = 0;
//nStepConverted++;
sNameLastCombineFile = "ConcatenatedDocument" + nStepConverted.ToString() + " _tempfile.pdf";

outputDocument.Save(sNameLastCombineFile);
outputDocument.Close();

outputDocument = PdfReader.Open(sNameLastCombineFile,PdfDocumentOpenMode.Modify);
}

UPDATE 2 versione 1.32 Complete example Error on line: PdfDocument inputDocument = PdfReader.Open(file, PdfDocumentOpenMode.Import);

Text error: Cannot handle iref streams. The current implementation of PDFsharp cannot handle this PDF feature introduced with Acrobat 6.

using PdfSharp.Pdf;
using PdfSharp.Pdf.IO;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            List<String> filesToPrint = new List<string>();

            filesToPrint = Directory.GetFiles(@"D:\Downloads\RACCOLTA\FILE PDF", "*.pdf").ToList();

            // Get some file names
            string[] files = filesToPrint.ToArray();

            // Open the output document
            PdfDocument outputDocument = new PdfDocument();

            PdfPage newPage;

            int nProcessedFile = 0;
            int nMemoryFile = 5;
            int nStepConverted = 0;
            String sNameLastCombineFile = "";

            try
            {
                // Iterate files
                foreach (string file in files)
                {
                    // Open the document to import pages from it.
                    PdfDocument inputDocument = PdfReader.Open(file, PdfDocumentOpenMode.Import);

                    // Iterate pages
                    int count = inputDocument.PageCount;
                    for (int idx = 0; idx < count; idx++)
                    {
                        // Get the page from the external document...
                        PdfPage page = inputDocument.Pages[idx];
                        // ...and add it to the output document.
                        outputDocument.AddPage(page);
                    }

                    nProcessedFile++;
                    if (nProcessedFile >= nMemoryFile)
                    {
                        nProcessedFile = 0;
                        //nStepConverted++;
                        sNameLastCombineFile = "ConcatenatedDocument" + nStepConverted.ToString() + " _tempfile.pdf";

                        outputDocument.Save(sNameLastCombineFile);
                        outputDocument.Close();

                        inputDocument = PdfReader.Open(sNameLastCombineFile , PdfDocumentOpenMode.Modify);
                    }
                }
                // Save the document...
                const string filename = "ConcatenatedDocument1_tempfile.pdf";
                outputDocument.Save(filename);
                // ...and start a viewer.
                Process.Start(filename);

            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                Console.ReadKey();

            }
        }
    }
}

UPDATE3 Code that generate exception out of memory

            int count = inputDocument.PageCount;
            for (int idx = 0; idx < count; idx++)
            {
                // Get the page from the external document...
                newPage = inputDocument.Pages[idx];
                // ...and add it to the output document.
                outputDocument.AddPage(newPage);

                newPage.Close();
            }

I can not exactly which row general exception

Answer 1

I had a simular issue, saving, closing and reopening the PdfDocument did not really help.

I am adding al lot (100+) large (upto 5Mb) images (tiff, jpg, etc) to a pdf document where every images has its own page. It crashed around image #50. After the save-close-reopen it did finish the whole document but was still getting close to max memory, around 3Gb. Some more images and it would still crash.

After more refining, I implemented a using for the XGraphics object, it was a little better again but not much.

The big step forward was disposing of the XImage within the loop! After that the application never used more than 100-200Kb, I removed the save-close-reopen for the PdfDocument and it was no problem.

Answer 2

After saving and closing outputDocument (the code is commented out in your snippet), you have to open outputDocument again, using PdfDocumentOpenMode.Modify .

It could help to add using(...) for the inputDocument .

If your code is running as a 32-bit process, then switching to 64 bit will allow your process to use more than 2 GB of RAM (assuming your computer has more than 2 GB RAM).

Update: The message "Cannot handle iref streams" means you have to use PDFsharp 1.50 Prerelease, available on NuGet.