System.Drawing.Image to stream C#

Try the following:

public static Stream ToStream(this Image image, ImageFormat format) {
  var stream = new System.IO.MemoryStream();
  image.Save(stream, format);
  stream.Position = 0;
  return stream;
}

Then you can use the following:

var stream = myImage.ToStream(ImageFormat.Gif);

Replace GIF with whatever format is appropriate for your scenario.

Use a memory stream

using(MemoryStream ms = new MemoryStream())
{
    image.Save(ms, ...);
    return ms.ToArray();
}