使用 itextsharp 根据大小将 pdf 拆分为较小的 pdf

Question

So we have some really inefficient code that splits a pdf into smaller chunks based on a maximum size allowed. Aka. if the max size is 10megs, an 8 meg file would be skipped, while a 16 meg file would be split based on the number of pages.

This is code that I inherited and feel like there has got to be a more efficient way to do this that requiring only one method and less instantiation of objects.

We use the following code to call the methods:

        List<int> splitPoints = null;
        List<byte[]> documents = null;

        splitPoints = this.GetPDFSplitPoints(currentDocument, maxSize);
        documents = this.SplitPDF(currentDocument, maxSize, splitPoints);

Methods:

    private List<int> GetPDFSplitPoints(IClaimDocument currentDocument, int maxSize)
    {
        List<int> splitPoints = new List<int>();
        PdfReader reader = null;
        Document document = null;
        int pagesRemaining = currentDocument.Pages;

        while (pagesRemaining > 0)
        {
            reader = new PdfReader(currentDocument.Data);
            document = new Document(reader.GetPageSizeWithRotation(1));

            using (MemoryStream ms = new MemoryStream())
            {
                PdfCopy copy = new PdfCopy(document, ms);
                PdfImportedPage page = null;

                document.Open();

                //Add pages until we run out from the original
                for (int i = 0; i < currentDocument.Pages; i++)
                {
                    int currentPage = currentDocument.Pages - (pagesRemaining - 1);

                    if (pagesRemaining == 0)
                    {
                        //The whole document has bee traversed
                        break;
                    }

                    page = copy.GetImportedPage(reader, currentPage);
                    copy.AddPage(page);

                    //If the current collection of pages exceeds the maximum size, we save off the index and start again
                    if (copy.CurrentDocumentSize > maxSize)
                    {
                        if (i == 0)
                        {
                            //One page is greater than the maximum size
                            throw new Exception("one page is greater than the maximum size and cannot be processed");
                        }

                        //We have gone one page too far, save this split index   
                        splitPoints.Add(currentDocument.Pages - (pagesRemaining - 1));
                        break;
                    }
                    else
                    {
                        pagesRemaining--;
                    }
                }

                page = null;

                document.Close();
                document.Dispose();
                copy.Close();
                copy.Dispose();
                copy = null;
            }
        }

        if (reader != null)
        {
            reader.Close();
            reader = null;
        }

        document = null;

        return splitPoints;
    }

    private List<byte[]> SplitPDF(IClaimDocument currentDocument, int maxSize, List<int> splitPoints)
    {
        var documents = new List<byte[]>();
        PdfReader reader = null;
        Document document = null;
        MemoryStream fs = null;
        int pagesRemaining = currentDocument.Pages;

        while (pagesRemaining > 0)
        {
            reader = new PdfReader(currentDocument.Data);
            document = new Document(reader.GetPageSizeWithRotation(1));

            fs = new MemoryStream();
            PdfCopy copy = new PdfCopy(document, fs);
            PdfImportedPage page = null;

            document.Open();

            //Add pages until we run out from the original
            for (int i = 0; i <= currentDocument.Pages; i++)
            {
                int currentPage = currentDocument.Pages - (pagesRemaining - 1);
                if (pagesRemaining == 0)
                {
                    //We have traversed all pages
                    //The call to copy.Close() MUST come before using fs.ToArray() because copy.Close() finalizes the document
                    fs.Flush();
                    copy.Close();
                    documents.Add(fs.ToArray());
                    document.Close();
                    fs.Dispose();
                    break;
                }

                page = copy.GetImportedPage(reader, currentPage);
                copy.AddPage(page);
                pagesRemaining--;

                if (splitPoints.Contains(currentPage + 1) == true)
                {
                    //Need to start a new document
                    //The call to copy.Close() MUST come before using fs.ToArray() because copy.Close() finalizes the document
                    fs.Flush();
                    copy.Close();
                    documents.Add(fs.ToArray());
                    document.Close();
                    fs.Dispose();
                    break;
                }
            }

            copy = null;
            page = null;

            fs.Dispose();
        }

        if (reader != null)
        {
            reader.Close();
            reader = null;
        }

        if (document != null)
        {
            document.Close();
            document.Dispose();
            document = null;
        }

        if (fs != null)
        {
            fs.Close();
            fs.Dispose();
            fs = null;
        }

        return documents;
    }

As far as I can tell, the only code online that I can see is VB and doesn't necessarily address the size issue.

UPDATE :

We're experiencing OutofMemory exceptions and I believe it's an issue with the Large Object Heap. So one thought was to reduce the code footprint and that would possibly reduce the number of large objects on the heap.

Basically this is part of a loop that goes through any number of PDF's, and then splits them and stores them in the database. Right now, we had to change the method from doing all of them at once (last run was 97 pdf's of various sizes), to running 5 pdf's through the system every 5 minutes. This is not ideal and won't scale well when we ramp up the tool to more clients.

(we're dealing with 50 -100 meg pdf's, but they could be larger).

Answer 1

I also inherited this exact code, and there appears to be a major flaw in it. In the GetPDFSplitPoints method, it's checking the total size of the copied pages against maxsize to determine at which page to split the file.
In the SplitPDF method, when it reaches the page where the split occurs, sure enough the MemoryStream at that point is below the maximum size allowed, and one more page would put it over the limit. But after document.Close(); is executed, much more is added to the MemoryStream (in one example PDF I worked with, the Length of the MemoryStream went from 9 MB to 19 MB before and after the document.Close ). My understanding is that all the necessary resources for the copied pages are added upon Close .
I'm guessing I'll have to rewrite this code completely to ensure I don't exceed the max size while retaining the integrity of the original pages.