title: plotting with black background in octave: keeping background color in print file
body: <p>I am using octave (4.2.2) to make a figure with a black background.</p>
  
  <pre><code>clear;clf
  %% circle
  theta=linspace(0,2*pi,91);xc=cos(theta);yc=sin(theta);
  fill(0.3*xc,0.3*yc,[0,0.5,0.5]);hold on
  set(gca,'color',[0 0 0])
  </code></pre>
  
  <p>This script accomplishes that on the terminal, however if I print the figure using</p>
  
  <pre><code>print -dpng black.back.png
  </code></pre>
  
  <p>the image has a white background.  If the set color command is changed to [1,1,1], both the figure displayed on the terminal and the printed image have a white background.  Can anyone suggest a way to save an image with a black background to a file?</p>