Question

我有来自iTextSharp的结果，它可以通过pdf阅读器进行解析，但我希望能够获取二进制内容并手动解析它。我尝试在标记<</Length 256/Filter/FlateDecode>>stream之间使用文字和 endstream并使用.NET DeflateStream类尝试解压缩导致此异常的文本：

System.IO.InvalidDataException: Block length does not match with its complement. at System.IO.Compression.Inflater.DecodeUncompressedBlock(Boolean& end_of_block) at System.IO.Compression.Inflater.Decode() at System.IO.Compression.Inflater.Inflate(Byte[] bytes, Int32 offset, Int32 length) at System.IO.Compression.DeflateStream.Read(Byte[] array, Int32 offset, Int32 count) at System.IO.Stream.InternalCopyTo(Stream destination, Int32 bufferSize) at FlateDecodeTest.Decompress(Byte[] data)

我的代码是：

using System;
using System.Security.Cryptography;
using System.Text;
using System.Diagnostics;
using System.IO;
using System.IO.Compression;

public class FlateDecodeTest
{
    public static void Main() 
    {
        string s = @"xœuÁN!E÷|Å...";

        byte[] b = Decompress(GetBytes(s));

        Console.WriteLine(GetString(b));
    }

    public static byte[] Decompress(byte[] data)
    {
        Console.WriteLine(data.Length);
        byte[] decompressedArray = null;
        try
        {
            using (MemoryStream decompressedStream = new MemoryStream())
            {
                using (MemoryStream compressStream = new MemoryStream(data))
                {
                    using (DeflateStream deflateStream = new DeflateStream(compressStream, CompressionMode.Decompress))
                    {
                        deflateStream.CopyTo(decompressedStream);
                    }
                }
                decompressedArray = decompressedStream.ToArray();
            }
        }
        catch (Exception exception)
        {
            Console.WriteLine(exception);
        }

        return decompressedArray;
    }

    static byte[] GetBytes(string str)
    {
        byte[] bytes = new byte[str.Length * sizeof(char)];
        System.Buffer.BlockCopy(str.ToCharArray(), 0, bytes, 0, bytes.Length);
        return bytes;
    }

    static string GetString(byte[] bytes)
    {
        char[] chars = new char[bytes.Length / sizeof(char)];
        System.Buffer.BlockCopy(bytes, 0, chars, 0, bytes.Length);
        return new string(chars);
    }
}

Answer 1

请勿使用DeflateStream课程。如果您对某个页面的内容流感兴趣（请参阅第1页），您可以使用以下方法：

byte[] streamBytes = reader.GetPageContent(1);

其中reader是PdfReader类的实例。当然，如果页面在其资源字典中具有Form XObjects，这是不够的。在这种情况下，您必须使用PRStream对象。例如：如果Form XObject（或任何其他流对象）的对象编号为23，那么就像这样得到PRStream对象：

PRStream str = (PRStream)reader.GetPdfObject(23);
byte[] bytes = PdfReader.GetStreamBytes(str);

与提供原始压缩字节的GetStreamBytesRaw()方法相反，GetStreamBytes()方法将解压缩流。见iTextSharp: Convert PdfObject to PdfStream

如果您不知道要检查的对象的编号，可以浏览PDF对象树，例如使用GetAsStream()的{{1}}方法，{ {1}}，等等。

FlateDecode PDF解码

1 个答案: