流中的位图:Bug

我有一个非常奇怪的错误。我需要缩小图像，缩小质量并转换为JPEG。当我把文件保存在磁盘上时，这一切都有效，但当我把它保存到流中时，它就不起作用了。

System.Drawing.Bitmap bitmap = // valid Bitmap from Disk
System.IO.Stream stream = new MemoryStream();
// JPEG Encoding
System.Drawing.Imaging.ImageCodecInfo jpgEncoder = GetEncoder( System.Drawing.Imaging.ImageFormat.Jpeg );
System.Drawing.Imaging.Encoder encoder2 = System.Drawing.Imaging.Encoder.Quality;
System.Drawing.Imaging.EncoderParameters parameters = new System.Drawing.Imaging.EncoderParameters( 1 );
System.Drawing.Imaging.EncoderParameter parameter = new System.Drawing.Imaging.EncoderParameter( encoder2, qualityLevel );
parameters.Param[0] = parameter;
// Save downscaled on Disk and stream
bitmap.Save( stream, jpgEncoder, parameters );
bitmap.Save( @"C:'TestJPEG.jpg", jpgEncoder, parameters );
// some stream stuff
var bytes = ((MemoryStream)stream).ToArray();
System.IO.Stream inputStream = new MemoryStream( bytes );
// Load from disk and stream
Bitmap fromDisk = new Bitmap( @"C:'TestJPEG.jpg" ); // works
Bitmap fromStream = new Bitmap( inputStream ); // crash invalid parameter no inner message or description
Bitmap fromStream2 = (Bitmap)Bitmap.FromStream( inputStream ); // same error here
// also crashes if I load the "stream" named Stream

我也可以使用Paint打开转换后的文件。有什么建议吗？

编辑：我在Windows7专业版上使用.Net Framework 4.0

第2版：尝试过寻找的东西（答案被删除）

stream.Seek( 0, SeekOrigin.Begin );

它与"旧"流一起工作。但我需要从字节数组中加载它。仍然相同的崩溃

var bitmap = new Bitmap(@"c:'Dokumente und Einstellungen'daniel.hilgarth'Desktop'Unbenannt.bmp");
ImageCodecInfo jpgEncoder = ImageCodecInfo.GetImageEncoders().Single(x => x.FormatDescription == "JPEG");
Encoder encoder2 = System.Drawing.Imaging.Encoder.Quality;
EncoderParameters parameters = new System.Drawing.Imaging.EncoderParameters( 1 );
EncoderParameter parameter = new EncoderParameter( encoder2, 50L );
parameters.Param[0] = parameter;
System.IO.Stream stream = new MemoryStream();
bitmap.Save( stream, jpgEncoder, parameters );
bitmap.Save(@"C:'Temp'TestJPEG.jpg", jpgEncoder, parameters);
var bytes = ((MemoryStream)stream).ToArray();
System.IO.Stream inputStream = new MemoryStream(bytes);
Bitmap fromDisk = new Bitmap(@"C:'Temp'TestJPEG.jpg");
Bitmap fromStream = new Bitmap(inputStream);