c# - Efficient way to send images via WCF?

Question

I am learning WCF, LINQ and a few other technologies by writing, from scratch, a custom remote control application like VNC. I am creating it with three main goals in mind:

1. The server will provide 'remote control' on an application level (i.e. seamless windows) instead of full desktop access.
2. The client can select any number of applications that are running on the server and receive a stream of images of each of them.
3. A client can connect to more than one server simultaneously.

Right now I am using WCF to send an array of Bytes that represents the window being sent:

using (var ms = new MemoryStream()) {
    window.GetBitmap().Save(ms, ImageFormat.Jpeg);
    frame.Snapshot = ms.ToArray();
}

GetBitmap implementation:

var wRectangle = GetRectangle();
var image = new Bitmap(wRectangle.Width, wRectangle.Height);
var gfx = Graphics.FromImage(image);

gfx.CopyFromScreen(wRectangle.Left, wRectangle.Top, 0, 0, wRectangle.Size, CopyPixelOperation.SourceCopy);

return image;

It is then sent via WCF (TCPBinding and it will always be over LAN) to the client and reconstructed in a blank windows form with no border like this:

using (var ms = new MemoryStream(_currentFrame.Snapshot))
{
    BackgroundImage = Image.FromStream(ms);
}

I would like to make this process as efficient as possible in both CPU and memory usage with bandwidth coming in third place. I am aiming to have the client connect to 5+ servers with 10+ applications per server.

Is my existing method the best approach (while continuing to use these technologies) and is there anything I can do to improve it?

Ideas that I am looking into (but I have no experience with):

• Using an open source graphics library to capture and save the images instead of .Net solution.
• Saving as PNG or another image type rather than JPG.
• Send image deltas instead of a full image every time.
• Try and 'record' the windows and create a compressed video stream instead of picture snapshots (mpeg?).

Answer 1

You should be aware for this points:

• Transport: TCP/binary message encoding will be fastest way to transfer your image data
• Image capture: you can rely on P/Invoke to access your screen data, as this can be faster and more memory consuming. Some examples: Capturing the Screen Image in C# [P/Invoke], How to take a screen shot using .NET [Managed] and Capturing screenshots using C# (Managed)
• You should to reduce your image data before send it;
  • choose your image format wisely, as some formats have native compression (as JPG)
  • an example should be Find differences between images C#
  • sending only diff image, you can crop it and just send non-empty areas
• Try to inspect your WCF messages. This will help you to understand how messages are formatted and will help you to identify how to make that messages smaller.

Just after passing through all this steps and being satisfied with your final code, you can download VncSharp source code. It implements the RFB Protocol (Wikipedia entry), "a simple protocol for remote access to graphical user interfaces. Because it works at the framebuffer level it is applicable to all windowing systems and applications, including X11, Windows and Macintosh. RFB is the protocol used in VNC (Virtual Network Computing)."