Start a task in scengraph , set up a roBitmap and draw what you need. use getPng(..) and save the result to device filesystem. use that path for a poster image in scenegraph.
Function SaveTestPng()
w = 200 : h = 100
bm = CreateObject("roBitmap", {width: w, height: h, AlphaEnable: true})
bm.DrawRect(10, 10, w-20, h-20, &hFF0000FF)
bm.Finish()
ba = bm.GetPng(0, 0, w, h)
ba.WriteFile("tmp:/test.png")
End Function