JPG encoding in python sent via socket to C# and decode

Question

I want to sent my processed image from python backend to C# frontend. So i encode it using JPG encoder and sent.

When i receive it and decoding it using jpegdecoder in C#, it throw the exception. Where size of received bytes are equal to the bytes sent after encoding.

Could anyone guide me how i decode this image and display it.

code in Python Server Side encoding Image JPG

while True:
    conn, addr = s.accept()
    print ('connected to : ' + addr[0] +" :"+ str(addr[1])) 

    vidcap = cv2.VideoCapture(videoPath)
    total_frames = int(vidcap.get(cv2.CAP_PROP_FRAME_COUNT))
    conn.setblocking(0)
    for mm in range(0,total_frames ,1):
       try:
           dataClient = str(conn.recv(4096).decode('UTF-8'))
           conn.send(str.encode(dataClient))   
           conn.close()
           kk=2
           break
       except socket.error:

           ret,img= vidcap.read()
           image = cv2.resize(img, (640, 480)) 
           #############################################
           encode_param=[int(cv2.IMWRITE_JPEG_QUALITY),100]
           result,enData=cv2.imencode('.jpg',image,encode_param)
           conn.send(enData)
           #############################################

Code in C# Client side decoding Image JPG

            const int PORT_NO = 6666;
            //const string SERVER_IP = "210.107.232.138"; // 210.107.232.138          127.0.0.1
            string SERVER_IP = IpAddress.Text;
            client = new TcpClient(SERVER_IP, PORT_NO);
            nwStream = client.GetStream();
            bytesToRead = new byte[client.ReceiveBufferSize];
            bytesRead = nwStream.Read(bytesToRead, 0, client.ReceiveBufferSize);
            /////////////////////////////////////
            MemoryStream ms = new MemoryStream(bytesRead);
            JpegBitmapDecoder decoder = new JpegBitmapDecoder(ms, BitmapCreateOptions.PreservePixelFormat, BitmapCacheOption.Default); //line 129
            BitmapSource bitmapSource = decoder.Frames[0];
            ///////////////////////////////////// 
            var src = new System.Windows.Media.Imaging.FormatConvertedBitmap();
            src.BeginInit();
            src.Source = bitmapSource;
            src.DestinationFormat = System.Windows.Media.PixelFormats.Bgra32;
            src.EndInit();

            //copy to bitmap
            Bitmap bitmap = new Bitmap(src.PixelWidth, src.PixelHeight, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
            var data = bitmap.LockBits(new Rectangle(Point.Empty, bitmap.Size), System.Drawing.Imaging.ImageLockMode.WriteOnly, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
            src.CopyPixels(System.Windows.Int32Rect.Empty, data.Scan0, data.Height * data.Stride, data.Stride);
            bitmap.UnlockBits(data);

            pictureBox2.Image = bitmap;

Answer 1

TcpClient.ReceiveBufferSize has a default value 8KB . If your jpeg data has more bytes than that, since your c# code just read the buffer only once, you will not receive the whole data.

You maybe want to use a loop in your c# code to read until reach the end of tcp stream.

try this:

var ms = new MemoryStream();
var buff = new byte[client.ReceiveBufferSize];
while (true) {
    var len = nwStream.Read(buff, 0, buff.Length);
    if (len <= 0) { break; }
    ms.Write(buff, 0, len);
}
ms.Seek(0, SeekOrigin.Begin);

wish helps.

Answer 2

MemoryStream ms = new MemoryStream(bytesRead); // bytesRead = int, number of bytes received

This line creates an empty MemoryStream with an initial capacity of bytesRead bytes. See MemoryStream(int)

You need to use another constructor to also fill it with the received data:

MemoryStream ms = new MemoryStream(bytesToRead); // byte[], received data

See MemoryStream(Byte[])

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Please also mind john's comment on your receiving code:

There's no guarantee you will receive the full buffer of data in a single receive event.