c# - 替换 PDF 中的特定文档

Question

包括:

using Ghostscript.NET;
using Ghostscript.NET.Processor;
using Ghostscript.NET.Rasterizer;

现在，我正在使用 Ghostscript.Net 将几个单独的 PDF 合并到一个文档中:

/// <summary>
/// Ghostscripts the file specified in parameter 1 as a PDF to the file specified in parameter 2
/// </summary>
/// <param name="fileNames">String[]. Array of Full Paths to a file to convert to a single PDF</param>
/// <param name="outputPath">String. Full Path to where Ghostscript will write the PDF</param>
public static void GhostscriptNetJoin(String[] fileNames, String outputPath)
{
    var sb = new StringBuilder();
    foreach (var fileName in fileNames)
    {
        var source = (fileName.IndexOf(' ') == -1) ? fileName : String.Format("\"{0}\"", fileName);
        sb.Append(source + " ");
    }
    var output_file = (outputPath.IndexOf(' ') == -1) ? outputPath : String.Format("\"{0}\"", outputPath);
    var gsArgs = new List<String>();
    gsArgs.Add("-empty"); // first argument is ignored. REF: http://stackoverflow.com/q/25202577/153923
    gsArgs.Add("-dBATCH");
    gsArgs.Add("-q");
    gsArgs.Add("-dNOPAUSE");
    gsArgs.Add("-dNOPROMPT");
    gsArgs.Add("-sDEVICE=pdfwrite");
    gsArgs.Add("-dPDFSETTINGS=/prepress");
    gsArgs.Add(String.Format(@"-sOutputFile={0}", output_file));
    gsArgs.Add(sb.ToString());
    var version = GhostscriptVersionInfo.GetLastInstalledVersion();
    using (var processor = new GhostscriptProcessor(version, false))
    {
        processor.Process(gsArgs.ToArray());
    }
}

我怎样才能稍后返回REPLACE or UPDATE第N页？

我已经草拟了一个有我计划的例程，但此时我不知道如何完成它。我可以提供 arg 值还是我应该使用其他工具？

/// <summary>
/// Replace Specific Document from source PDF file
/// </summary>
/// <param name="source">String. Full path to the multi-page PDF</param>
/// <param name="documentN">String. Full path to the document to insert</param>
/// <param name="indexN">int. Page Index where the new document should be inserted</param>
public static void GhostscriptNetReplace(String source, String documentN, int indexN)
{
    var list = new List<String>();
    var version = GhostscriptVersionInfo.GetLastInstalledVersion();
    using (var processor = new GhostscriptProcessor(version, false))
    {
        var gsArgs = new List<String>();
        // what arguments are needed?
        throw new NotImplementedException("I don't know how to code for this yet.");
        processor.Process(gsArgs.ToArray());
    }
    list.RemoveAt(indexN);
    list.Insert(indexN, documentN);
    var sb = new StringBuilder();
    foreach (var fileName in list)
    {
        var fmtSource = (fileName.IndexOf(' ') == -1) ? fileName : String.Format("\"{0}\"", fileName);
        sb.Append(fmtSource + " ");
    }
    var output_file = (source.IndexOf(' ') == -1) ? source : String.Format("\"{0}\"", source);
    using (var processor = new GhostscriptProcessor(version, false))
    {
        var gsArgs = new List<String>();
        gsArgs.Add("-empty"); // first argument is ignored. REF: http://stackoverflow.com/q/25202577/153923
        gsArgs.Add("-dBATCH");
        gsArgs.Add("-q");
        gsArgs.Add("-dNOPAUSE");
        gsArgs.Add("-dNOPROMPT");
        gsArgs.Add("-sDEVICE=pdfwrite");
        gsArgs.Add("-dPDFSETTINGS=/prepress");
        gsArgs.Add(String.Format(@"-sOutputFile={0}", output_file));
        gsArgs.Add(sb.ToString());
        processor.Process(gsArgs.ToArray());
    }
}

Answer 1

你也许可以做这样的事情(现在无法测试代码，但它的原理是基于 Ghostscript.NET repo 检查出来的):

var prcPath = "PATH"; //a path to store the temporary files
var pageCount = GetPDFPageCount(source);
var list = SplitPDFatIndex(source, prcPath, indexN);

private static List<String> SplitPDFatIndex(String pathToFile, String tempPath, int index)
{
    var outList = new List<String>();
    outList.Add(SlicePDFatIndex(pathToFile, tempPath, index, true);
    outlist.Add(null); // Alternatively modify method below to permit pulling page N
    outList.Add(SlicePDFatIndex(pathToFile, tempPath, index, false);

    return outList;
}

private static String SlicePDFatIndex(String pathToFile, String tempPath, int index, bool lessThanIndex)
{
    using (var processor = new GhostscriptProcessor(version, false))
    {
        var pageFrom = 1;
        var pageTo = index - 1;
        var name = tempPath + "temp_left.pdf";

        if (!lessThanIndex)
        {
            pageFrom = index + 1;
            pageTo = pageCount;
            name = tempPath + "temp_right.pdf";
        }

        var gsArgs = new List<String>();
        gsArgs.Add("-empty");
        gsArgs.Add("-dBATCH");
        gsArgs.Add("-q");
        gsArgs.Add("-dNOPAUSE");
        gsArgs.Add("-dNOPROMPT");
        gsArgs.Add("-sDEVICE=pdfwrite");
        gsArgs.Add("-dPDFSETTINGS=/prepress");
        gsArgs.Add(String.Format(@"-f{0}", pathToFile);
        gsArgs.Add("-dFirstPage=" + pageFrom.ToString());
        gsArgs.Add("-dLastPage=" + pageTo.ToString());
        gsArgs.Add(String.Format(@"-sOutputFile={0}", name));
        processor.Process(@"-f{0}", pathToFile);

        return name;
}

private static int GetPDFPageCount(String pathToFile)
{
    var count;
    var GhostscriptViewer viewer;

    viewer = new GhostscriptViewer();
    viewer.ShowPageAfterOpen = false;
    viewer.ProgressiveUpdate = false;
    viewer.Open(source); // try (source, version, false) or (source, version, true) if for some reason it hangs up here
    count = viewer.LastPageNumber;
    viewer.Close()

    return count;
}