B4J Question convert PNG from staticmap Google to Base64

Sub Handle(req As ServletRequest, resp As ServletResponse)
   GetPNG (resp)
   StartMessageLoop
End Sub

Sub GetPNG(resp As ServletResponse)
   Dim job As HttpJob
   job.Initialize("",Me)
   job.Download2($"http://maps.googleapis.com/maps/api/staticmap"$ , Array As String("center","merlion+stue"  ,"size","640x480") )
   Wait For (job) JobDone(job As HttpJob)
   If job.Success Then
     resp.Write(  job.GetString  )  '<-- how to convert return to base64 string ??
   End If
   StopMessageLoop
End Sub