title: im4java compare command giving Command exception
body: <p>Following code gives <strong>org.im4java.core.CommandException: org.im4java.core.CommandException: return code: 1</strong>     I am trying to compare two colors. what is wrong in my code or what is the correct solution to compare colors.</p>
  
  <pre><code>    ImageCommand compare=new ImageCommand();
      compare.setCommand("compare");
      IMOperation op = new IMOperation();
      op.fuzz(30.0);
      op.metric("AE");
      op.addImage();
      op.addImage();
      op.addImage();
  
      compare.run(op,"xc:green","xc:brown","null:");
  </code></pre>