Sends the PNG image to an HTTP stream.
SaveHttp can only be
called in an ASP or ASP.NET environment as it internally uses
ASP's Response.BinaryWrite method.
DispHeader specifies the Content-Disposition header
to be included in the HTTP stream. This header
carries the file name information to be presented to the user
when the file is saved to disk on the client machine. This argument has
to be in the following two formats:
"filename=somename.png"
or
"attachment; filename=somename.png"
The latter prompts the user to save the file
to disk instead of opening it in-place in the browser.