c# – 使用itextsharp根据大小将pdf拆分为较小的pdf

所以我们有一些非常低效的代码,根据允许的最大大小将pdf分成更小的块.阿卡.如果最大大小为10megs,则跳过8兆字节文件,而根据页数分割16兆字节文件.

这是我继承的代码,并且感觉必须有一种更有效的方法来执行此操作,只需要一个方法和较少的对象实例化.

我们使用以下代码来调用方法：

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

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

方法：

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;
    }

据我所知,我能看到的唯一在线代码是VB,并不一定解决大小问题.

更新：

我们遇到了OutofMemory异常,我认为这是大对象堆的问题.因此,一个想法是减少代码占用空间,这可能会减少堆上的大对象数量.

基本上,这是循环的一部分,遍历任意数量的PDF,然后拆分它们并将它们存储在数据库中.现在,我们不得不改变方法,一次完成所有这些(最后一次运行是各种大小的97 pdf),每5分钟通过系统运行5个pdf.当我们将工具增加到更多客户端时,这并不理想,并且不能很好地扩展.

(我们正在处理50 -100兆字节的pdf,但它们可能更大).

解决方法

我也继承了这个确切的代码,似乎存在一个重大缺陷.在GetPDFSplitPoints方法中,它根据maxsize检查复制页面的总大小,以确定在哪个页面拆分文件. 在SplitPDF方法中,当它到达发生拆分的页面时,确定该点上的MemoryStream低于允许的最大大小,并且还有一页将使其超出限制.但是在document.Close()之后;执行后,还有更多内容被添加到MemoryStream中(在我使用过的PDF文件中,MemoryStream的长度从文件前后的9 MB变为19 MB.关闭).我的理解是,复制页面的所有必要资源都会在关闭时添加. 我猜我必须完全重写这段代码,以确保我不会超过最大尺寸,同时保持原始页面的完整性.