title: Transparent background in gnuplot multiplot
body: <p>I'd like to get a transparent background in my gnuplot figure. 
  What I coded till now is: </p>
  
  <pre><code>#! /usr/bin/python
  
  from numpy import *
  import Gnuplot as gp
  import Gnuplot.funcutils
  
  x = (1,2,3)
  y=(2,4,5)
  x1 = (3,6,8)
  g = gp.Gnuplot()
  g("set terminal svg size 200,400")
  g("set output 'filename.svg'")
  g("unset xtics")
  g("unset ytics")
  g("set multiplot layout 3,1 title 'Title here'")
  g("set object 1 rectangle from screen 0,0 to screen 1,1 fillcolor rgb '#ff0000'      behind")
  #First
  g("set tmargin 2")
  g("set title 'Plot'")
  g("unset key")
  d = gp.Data(x,y,with_="lines")
  g.plot(d)
  #Secon
  g("set title 'Plot2'")
  g("unset key")
  d1 = gp.Data(x1,y,with_="lines")
  g.plot(d1)
  #Third
  g("set title 'Plot3'")
  g("unset key")
  d2 = gp.Data(y,x,with_="lines")
  g.plot(d2)
  g("unset multiplot")
  </code></pre>
  
  <p>I got a red screen but just the third plot. 
  (Yeah, I have to change the rgb combo to get transparent background color. But, what's it?)</p>
  
  <p>Thanks in advance, 
  FB</p>