.Net下压缩图片文件，该如何做呢？请问各位大虾。

[fengyunhongri]

DeflateStream 提供用于使用 Deflate 算法压缩和解压缩流的方法和属性。
GZipStream 提供用于压缩和解压缩流的方法和属性。
为何用它们压缩，越压缩越大呢？请高手支招。

[homejiji]

学习

[cppfaq]

C# 批量压缩图片（转载以收藏）
http://adxlong.blog.163.com/blog/static/22830932009263341526/

[cppfaq]

PS
你怎么压的？贴出来看看

[fengyunhongri]

public static void GZipCompressDecompress(string filename)
	{
	Console.WriteLine("Test compression and decompression on file {0}", filename);
	FileStream infile;
		try
		{
		// Open the file as a FileStream object.
		infile = new FileStream(filename, FileMode.Open, FileAccess.Read, FileShare.Read);
		byte[] buffer = new byte[infile.Length];
		// Read the file to ensure it is readable.
		int count = infile.Read(buffer, 0, buffer.Length);
			if ( count != buffer.Length) 
			{
			infile.Close();
			Console.WriteLine("Test Failed: Unable to read data from file"); 
			return;
			}
		infile.Close();
		MemoryStream ms = new MemoryStream();
		// Use the newly created memory stream for the compressed data.
		GZipStream compressedzipStream = new GZipStream(ms , CompressionMode.Compress, true);
		Console.WriteLine("Compression");
		compressedzipStream.Write(buffer, 0, buffer.Length);
		// Close the stream.
		compressedzipStream.Close();
		Console.WriteLine("Original size: {0}, Compressed size: {1}", buffer.Length, ms.Length);

		// Reset the memory stream position to begin decompression.
		ms.Position = 0;
		GZipStream zipStream = new GZipStream(ms, CompressionMode.Decompress);
		Console.WriteLine("Decompression");
		byte[] decompressedBuffer = new byte[buffer.Length + 100];
		// Use the ReadAllBytesFromStream to read the stream.
		int totalCount = GZipTest.ReadAllBytesFromStream(zipStream, decompressedBuffer);
		Console.WriteLine("Decompressed {0} bytes", totalCount);

		if( !GZipTest.CompareData(buffer, buffer.Length, decompressedBuffer, totalCount) ) 
		{
		Console.WriteLine("Error. The two buffers did not compare.");
		}
	zipStream.Close(); 
		} // end try
		catch (InvalidDataException)
		{
			Console.WriteLine("Error: The file being read contains invalid data.");
		}
		catch (FileNotFoundException)
		{
			Console.WriteLine("Error:The file specified was not found.");
		}
		catch (ArgumentException)
		{
			Console.WriteLine("Error: path is a zero-length string, contains only white space, or contains one or more invalid characters");
		}
		catch (PathTooLongException)
		{
			Console.WriteLine("Error: The specified path, file name, or both exceed the system-defined maximum length. For example, on Windows-based platforms, paths must be less than 248 characters, and file names must be less than 260 characters.");
		}
		catch (DirectoryNotFoundException)
		{
			Console.WriteLine("Error: The specified path is invalid, such as being on an unmapped drive.");
		}
		catch (IOException)
		{
			Console.WriteLine("Error: An I/O error occurred while opening the file.");
		}
		catch (UnauthorizedAccessException)
		{
			Console.WriteLine("Error: path specified a file that is read-only, the path is a directory, or caller does not have the required permissions.");
		}
		catch (IndexOutOfRangeException)
		{
			Console.WriteLine("Error: You must provide parameters for MyGZIP.");
		}
	}

[fengyunhongri]

CSDN上的实例。

[cppfaq]

果然越压越大

有人说
GZip对文本压缩比较好，
对视频，MP3，JPG图片这些已经经过压缩的文件再次压缩可能会越压越大
对可执行文件 exe , dll这些，压缩比也是很小的

楼主试一下SharpZipLib
http://www.icsharpcode.net/OpenSource/SharpZipLib/

[wuyq11]

通过ICSharpCode.SharpZipLib.dll 压缩
http://www.cnblogs.com/answercard/archive/2008/11/24/1339867.html

[fengyunhongri]

谢谢cppfaq的支持！