title: Gnuplot: how to set pm3d map transparent?
body: <p>I have really simple question: I would like to know how to make the contour figure (pm3d map) transparent in Gnuplot (gnuplot version 5.2).</p>
  
  <p>I could find ways to make transparent plots or filled curve,
  (such as this website - <a href="http://gnuplot.sourceforge.net/demo/transparent.html" rel="nofollow noreferrer">http://gnuplot.sourceforge.net/demo/transparent.html</a>)
  but not for the contour plots.</p>
  
  <p>What I am trying to do is, to overlay image and contour plot and would like to make the contour transparent.</p>
  
  <p>Thank you for your help!</p>
  
  <p><a href="https://i.stack.imgur.com/1SfCA.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/1SfCA.png" alt="enter image description here"></a></p>
  
  <p><strong>Added:</strong>
  When I try to do</p>
  
  <pre><code>set style fill transparent solid 0.5
  </code></pre>
  
  <p>the contour region changed to gray.. why is this?</p>
  
  <p><a href="https://i.stack.imgur.com/cAewI.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cAewI.png" alt="enter image description here"></a></p>