Best .NET Framework compression class?

7
votes

Yes, I know GZipStream or DeflateStream is the common ones in .NET Framework which handle compression/decompression.

I wish to have compress/decompress functions in my program, but

  1. I wish a .NET Framework C# one, not a 3rd party open source. I can't use because of those copyright restrictions in my program.

  2. GZipStream and DeflateStream are not so good. for e.g., GZipStream compress a file to 480KB while 7Zip compress the same file to the size of 57KB.

Does Microsoft have other good compression methods???

Thanks

5
c#compression
Thanks for all your replies. Can I ask whether DeflateStream is using Huffman coding? – Jack
Both DeflateStream and GZipStream use a combination of the LZ77 algorithm and Huffman coding (see msdn.microsoft.com/en-us/library/… and msdn.microsoft.com/en-us/library/…). Deflate is the pure compression algorithm, while GZipStream includes a CRC checksum and could be extended by writing different compression algorithms (The current .net framework just implements that one compression algorithm). – Philip Daubmeier

5 Answers

6
votes

GZipStream and DeflateStream are specifically intended for compressed streams, not general compression of files for storage.

Other than those classes, compression is not built into .NET. If you want high-quality compression you will have to go to a third party library. Check out http://www.7-zip.org/sdk.html for an open-source 7zip library.

2
votes

There is a managed wrapper for 7zip. The license is LGPL so you can use it in closed source projects. I do not know if this fits your license requirements as you did not state them.

http://sevenzipsharp.codeplex.com/

1
votes

I don't have any statistics regarding compression rates, but I'd been using the SharpZipLib library for years with much success.

1
votes

Well, I try to compress like recursive data, is funny. Check my example:

private byte[] CompressWithLevels(byte[] data)
{
    using(MemoryStream ms = new MemoryStream())
    {
        using(GZipStream gz = new GZipStream(ms, CompressionMode.Compress))
        {
            gz.Write(data, 0, data.Length);
            return ms.ToArray();
        }
    }
}

Now, I try to Compress a file too big, for example:

string path = @"c:\test.bin";
byte[] buffer = File.ReadAllBytes(path);
byte[] level1 = CompressWithLevels(buffer);
byte[] level2 = CompressWithLevels(level1);

Check the size of buffer, level1 and level2.
buffer size is 77683, level1 = 57354 and level2 = 8202...

buffer is 100%, then:
57354 is 73,83%
8202 is 10,55%
so funny.

0
votes

you can also use the open source ZLib (http://www.zlib.net/) with PInvoke, or use a wrapper for it (I've used zlib.net - http://www.componentace.com/zlib_.NET.htm - but I believe it had some bugs). it's less convenient than managed libraries, but more efficient than DeflateStream/GZipStream (which are the same except for an extra CRC in GZipStream).