office pdf 文本提取

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Text;

namespace IFilter
{
[Flags]
public enum IFILTER_INIT : uint
{
   NONE = 0,
   CANON_PARAGRAPHS = 1,
   HARD_LINE_BREAKS = 2,
   CANON_HYPHENS = 4,
   CANON_SPACES = 8,
   APPLY_INDEX_ATTRIBUTES = 16,
   APPLY_CRAWL_ATTRIBUTES = 256,
   APPLY_OTHER_ATTRIBUTES = 32,
   INDEXING_ONLY = 64,
   SEARCH_LINKS = 128,
   FILTER_OWNED_VALUE_OK = 512
}

public enum CHUNK_BREAKTYPE
{
   CHUNK_NO_BREAK = 0,
   CHUNK_EOW = 1,
   CHUNK_EOS = 2,
   CHUNK_EOP = 3,
   CHUNK_EOC = 4
}

[Flags]
public enum CHUNKSTATE
{
   CHUNK_TEXT = 0x1,
   CHUNK_VALUE = 0x2,
   CHUNK_FILTER_OWNED_VALUE = 0x4
}

[StructLayout(LayoutKind.Sequential)]
public struct PROPSPEC
{
   public uint ulKind;
   public uint propid;
   public IntPtr lpwstr;
}

[StructLayout(LayoutKind.Sequential)]
public struct FULLPROPSPEC
{
   public Guid guidPropSet;
   public PROPSPEC psProperty;
}

[StructLayout(LayoutKind.Sequential)]
public struct STAT_CHUNK
{
   public uint idChunk;
   [MarshalAs(UnmanagedType.U4)] public CHUNK_BREAKTYPE breakType;
   [MarshalAs(UnmanagedType.U4)] public CHUNKSTATE flags;
   public uint locale;
   [MarshalAs(UnmanagedType.Struct)] public FULLPROPSPEC attribute;
   public uint idChunkSource;
   public uint cwcStartSource;
   public uint cwcLenSource;
}

[StructLayout(LayoutKind.Sequential)]
public struct FILTERREGION
{
   public uint idChunk;
   public uint cwcStart;
   public uint cwcExtent;
}

[ComImport]
[Guid("89BCB740-6119-101A-BCB7-00DD010655AF")]
[InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
public interface IFilter
{
   [PreserveSig]
   int Init([MarshalAs(UnmanagedType.U4)] IFILTER_INIT grfFlags, uint cAttributes, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex=1)] FULLPROPSPEC[] aAttributes, ref uint pdwFlags);

   [PreserveSig]
   int GetChunk(out STAT_CHUNK pStat);

   [PreserveSig]
   int GetText(ref uint pcwcBuffer, [MarshalAs(UnmanagedType.LPWStr)] StringBuilder buffer);

   void GetValue(ref UIntPtr ppPropValue);
   void BindRegion([MarshalAs(UnmanagedType.Struct)] FILTERREGION origPos, ref Guid riid, ref UIntPtr ppunk);
}

[ComImport]
[Guid("f07f3920-7b8c-11cf-9be8-00aa004b9986")]
public class CFilter
{
}

public class IFilterConstants
{
   public const uint PID_STG_DIRECTORY = 0x00000002;
   public const uint PID_STG_CLASSID = 0x00000003;
   public const uint PID_STG_STORAGETYPE = 0x00000004;
   public const uint PID_STG_VOLUME_ID = 0x00000005;
   public const uint PID_STG_PARENT_WORKID = 0x00000006;
   public const uint PID_STG_SECONDARYSTORE = 0x00000007;
   public const uint PID_STG_FILEINDEX = 0x00000008;
   public const uint PID_STG_LASTCHANGEUSN = 0x00000009;
   public const uint PID_STG_NAME = 0x0000000a;
   public const uint PID_STG_PATH = 0x0000000b;
   public const uint PID_STG_SIZE = 0x0000000c;
   public const uint PID_STG_ATTRIBUTES = 0x0000000d;
   public const uint PID_STG_WRITETIME = 0x0000000e;
   public const uint PID_STG_CREATETIME = 0x0000000f;
   public const uint PID_STG_ACCESSTIME = 0x00000010;
   public const uint PID_STG_CHANGETIME = 0x00000011;
   public const uint PID_STG_CONTENTS = 0x00000013;
   public const uint PID_STG_SHORTNAME = 0x00000014;
   public const int FILTER_E_END_OF_CHUNKS = (unchecked((int) 0x80041700));
   public const int FILTER_E_NO_MORE_TEXT = (unchecked((int) 0x80041701));
   public const int FILTER_E_NO_MORE_VALUES = (unchecked((int) 0x80041702));
   public const int FILTER_E_NO_TEXT = (unchecked((int) 0x80041705));
   public const int FILTER_E_NO_VALUES = (unchecked((int) 0x80041706));
   public const int FILTER_S_LAST_TEXT = (unchecked((int) 0x00041709));
}

///
/// IFilter return codes
///
public enum IFilterReturnCodes : uint
{
   ///
   /// Success
   ///
   S_OK = 0,
   ///
   /// The function was denied access to the filter file.
   ///
   E_ACCESSDENIED = 0x80070005,
   ///
   /// The function encountered an invalid handle, probably due to a low-memory situation.
   ///
   E_HANDLE = 0x80070006,
   ///
   /// The function received an invalid parameter.
   ///
   E_INVALIDARG = 0x80070057,
   ///
   /// Out of memory
   ///
   E_OUTOFMEMORY = 0x8007000E,
   ///
   /// Not implemented
   ///
   E_NOTIMPL = 0x80004001,
   ///
   /// Unknown error
   ///
   E_FAIL = 0x80000008,
   ///
   /// File not filtered due to password protection
   ///
   FILTER_E_PASSWORD = 0x8004170B,
   ///
   /// The document format is not recognised by the filter
   ///
   FILTER_E_UNKNOWNFORMAT = 0x8004170C,
   ///
   /// No text in current chunk
   ///
   FILTER_E_NO_TEXT = 0x80041705,
   ///
   /// No more chunks of text available in object
   ///
   FILTER_E_END_OF_CHUNKS = 0x80041700,
   ///
   /// No more text available in chunk
   ///
   FILTER_E_NO_MORE_TEXT = 0x80041701,
   ///
   /// No more property values available in chunk
   ///
   FILTER_E_NO_MORE_VALUES = 0x80041702,
   ///
   /// Unable to access object
   ///
   FILTER_E_ACCESS = 0x80041703,
   ///
   /// Moniker doesn't cover entire region
   ///
   FILTER_W_MONIKER_CLIPPED = 0x00041704,
   ///
   /// Unable to bind IFilter for embedded object
   ///
   FILTER_E_EMBEDDING_UNAVAILABLE = 0x80041707,
   ///
   /// Unable to bind IFilter for linked object
   ///
   FILTER_E_LINK_UNAVAILABLE = 0x80041708,
   ///
   /// This is the last text in the current chunk
   ///
   FILTER_S_LAST_TEXT = 0x00041709,
   ///
   /// This is the last value in the current chunk
   ///
   FILTER_S_LAST_VALUES = 0x0004170A
}

///
/// Convenience class which provides static methods to extract text from files using installed IFilters
///
public class DefaultParser
{
   public DefaultParser()
   {
   }

   [DllImport("query.dll", CharSet = CharSet.Unicode)]
   private extern static int LoadIFilter(string pwcsPath, [MarshalAs(UnmanagedType.IUnknown)] object pUnkOuter, ref IFilter ppIUnk);

   private static IFilter loadIFilter(string filename)
   {
    object outer = null;
    IFilter filter = null;

    // Try to load the corresponding IFilter
    int resultLoad = LoadIFilter(filename,   outer, ref filter);
    if (resultLoad != (int) IFilterReturnCodes.S_OK)
    {
     return null;
    }
    return filter;
   }

   public static bool IsParseable(string filename)
   {
    return loadIFilter(filename) != null;
   }

   public static string Extract(string path)
   {
    StringBuilder sb = new StringBuilder();
    IFilter filter = null;

    try
    {
     filter = loadIFilter(path);

     if (filter == null)
      return String.Empty;

     uint i = 0;
     STAT_CHUNK ps = new STAT_CHUNK();

     IFILTER_INIT iflags =
      IFILTER_INIT.CANON_HYPHENS |
      IFILTER_INIT.CANON_PARAGRAPHS |
      IFILTER_INIT.CANON_SPACES |
      IFILTER_INIT.APPLY_CRAWL_ATTRIBUTES |
      IFILTER_INIT.APPLY_INDEX_ATTRIBUTES |
      IFILTER_INIT.APPLY_OTHER_ATTRIBUTES |
      IFILTER_INIT.HARD_LINE_BREAKS |
      IFILTER_INIT.SEARCH_LINKS |
      IFILTER_INIT.FILTER_OWNED_VALUE_OK;

     if (filter.Init(iflags, 0, null, ref i) != (int) IFilterReturnCodes.S_OK)
      throw new Exception("Problem initializing an IFilter for:\n" + path + " \n\n");

     while (filter.GetChunk(out ps) == (int) (IFilterReturnCodes.S_OK))
     {
      if (ps.flags == CHUNKSTATE.CHUNK_TEXT)
      {
       IFilterReturnCodes scode = 0;
       while (scode == IFilterReturnCodes.S_OK || scode == IFilterReturnCodes.FILTER_S_LAST_TEXT)
       {
        uint pcwcBuffer = 65536;
        System.Text.StringBuilder sbBuffer = new System.Text.StringBuilder((int)pcwcBuffer);

        scode = (IFilterReturnCodes) filter.GetText(ref pcwcBuffer, sbBuffer);

        if (pcwcBuffer > 0 && sbBuffer.Length > 0)
        {
         if (sbBuffer.Length < pcwcBuffer) // Should never happen, but it happens !
          pcwcBuffer = (uint)sbBuffer.Length;

         sb.Append(sbBuffer.ToString(0, (int) pcwcBuffer));
         sb.Append(" "); // "\r\n"
        }

       }
      }

     }
    }
    finally
    {
     if (filter != null)
      Marshal.ReleaseComObject(filter);
    }

    return sb.ToString();
   }
}