title: Gnuplot: how to get better symbol alpha in pdf terminal
body: <p>Here is the test code:</p>
  
  <pre><code>set terminal pdf enhanced;
  set output "test.pdf"
  plot 1 title "{/Symbol a} {/Symbol b} {/Symbol c}";
  </code></pre>
  
  <p>That gives:</p>
  
  <p><img src="https://i.stack.imgur.com/BJUju.png" alt="enter image description here"></p>
  
  <p>The alpha produced is very strange. I want a normal alpha like this:</p>
  
  <p><img src="https://i.stack.imgur.com/bT7X5.png" alt="enter image description here"></p>
  
  <p>Is there anyway I can do it?</p>