CODEWITHSUNDEEP
c#bitmapstreamjpeg
Arndt Bieberstein
Arndt Bieberstein

Reputation: 1128

Bitmap from Stream: Bug?

I have a pretty strange Error. I need to scale down images, scale down the quality and convert to JPEG. This all works when I save the File on disk, but it doesn't work when I save it to a Stream.

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

I can also open the converted file with Paint. Any suggestions?

Edit: I'm using .Net Framework 4.0 on Windows 7 Professional

Edit2: Tried that Seek thing (Answer was deleted)

stream.Seek( 0, SeekOrigin.Begin );

It workes with the "old" stream. But i need to load it from a byte Array. Still same crash

Upvotes: 4

Views: 11883

Answers (1)

Daniel Hilgarth
Daniel Hilgarth

Reputation: 174299

The following code works for me:

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);

There are a few differences to your code. Which one causes your problem is up to you to find out, I guess:

  • I used 50L as qualityLevel. When using 1, 2, 50 or 100, I was getting an ArgumentException "Parameter is not valid". As I don't know the type or value of your qualityLevel variable that can very well be the problem.
  • I replaced your GetEncoder method. I don't know what your method does exactly, so it could be the problem, but I doubt it.

Upvotes: 2

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