I use reflection to get a GIF image that contains a transparency
mask (the white background should be transparent) that is
part of my C# project build.  The problem is that the image's
transparency property disappears when I render it making
it look as if were a JPEG image.

The code I use is:

Assembly assem = this.GetType().Assembly;
Stream streamTransPic =
assem.GetManifestResourceStream("MyProject.images.transPic.gif");
transPic = System.Drawing.Image.FromStream(streamTransPic);

It is rendered with Graphics.DrawImage method in

  gObj.DrawImage (transPic, rect);

where gObj is an instance of Graphics and rect has already been
defined.

If I read the image from a file rather than storing it in the compiled
assembly, its GIF transparency property is present when I render
it.  But I don't want to use separate data files with production code.