Write Binary File

Question

I am reading data from an IPhone App that uses http POST to transfer the image to the Server I can read this into a an binary and it does write to a file (See below) the issue I have is when I open the image it fails.

You can see the code from the Iphone on this post: asp http POST Read Data

Code:

byte[] buffer = new byte[Request.ContentLength];
using (BinaryReader br = new BinaryReader(Request.InputStream))
    br.Read(buffer, 0, buffer.Length);

string fileName = @"C:\test\test.jpg";
FileStream fs = new FileStream(fileName, FileMode.Create, 
    FileAccess.ReadWrite);
BinaryWriter bw = new BinaryWriter(fs);
bw.Write(buffer);
bw.Close();

The image Content-Type is application/octet-stream

Can anyone shine any light onto this please.

Are you asking what an application/octet-stream is or how to change it to a different MIME type? — Thomas Owens
– Thomas Owens, Commented Oct 15, 2009 at 13:44
when i have put failed I mean the image will not open, incorrect format. Opened it in Notpad and can see the header and content. — MartGriff
– MartGriff, Commented Oct 15, 2009 at 14:12

Christian Hayter · Accepted Answer · 2009-10-15 13:44:59Z

3

Perhaps the Request.ContentLength was not set correctly? I know from bitter experience that it's not always safe to trust it. :-(

You can read the stream without knowing the length in advance like this:

const int bufferSize = 1024 * 64; // pick any reasonable buffer size
List<byte> buffer = new List<byte>();
using(Stream stream = new BufferedStream(request.InputStream, bufferSize)) {
    int value;
    while((value = stream.ReadByte()) != -1) {
        buffer.Add((byte) value);
    }
}

answered Oct 15, 2009 at 13:44

Christian Hayter

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Comments

SwDevMan81 · Accepted Answer · 2009-10-15 14:29:15Z

1

Does the following work? For this it would probably be better to change the FileStream to a MemoryStream

fs.Position = 0;
Bitmap bit_map = Bitmap.FromStream(fs) as Bitmap;
bit_map.Save(@"C:\test\test.jpg");

Or

fs.Position = 0;
Image image = Image.FromStream(fs); 
image.Save(@"C:\test\test.jpg", ImageFormat.Jpeg);

Full Example (using your example, but if you want to change how the binary data is read from the other post, that is fine too, just confinue from after you have the buffer):

byte[] buffer = new byte[Request.ContentLength];
using (BinaryReader br = new BinaryReader(Request.InputStream))
    br.Read(buffer, 0, buffer.Length);
MemoryStream mem_stream = new MemoryStream (buffer); 
mem_stream.Write(buffer, 0, buffer.Length); 
mem_stream.Position = 0;
Image image = Image.FromStream(mem_stream); 
image.Save(@"C:\test\test.jpg", ImageFormat.Jpeg);
mem_stream.Close();

edited Oct 15, 2009 at 14:29

answered Oct 15, 2009 at 13:55

SwDevMan81

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6 Comments

MartGriff Over a year ago

Can you gibe me an example how I would use the memory stream and how I would write the List<byte> data into this.

SwDevMan81 Over a year ago

I updated the example using your code for reading the data into the buffer. You can change that to what Christain wrote if you want.

MartGriff Over a year ago

That failed on this link: System.Drawing.Image image = System.Drawing.Image.FromStream(mem_stream); With Not a valid parameter

SwDevMan81 Over a year ago

I think this usually means there are some invalid characters in the buffer. How is the image encoded? Can you do a diff on the original image and the saved one to see the differences?

MartGriff Over a year ago

you can see what data is being posted here: stackoverflow.com/questions/1547967/asp-http-post-read-data Would it be due to the image information is bing sent back in the body and when writing to a file its putting all that information in to?

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