title: marvin image color difference plugin error
body: <p>I am getting a null pointer exception whenever i am trying to process two images for color difference. The code is </p>
  
  <pre><code>MarvinImageIO.saveImage(currentFrame, "check1.jpg");
                  MarvinImageIO.saveImage(template, "check2.jpg");
  
                  currentFrame=MarvinImageIO.loadImage("check1.jpg");
                  template=MarvinImageIO.loadImage("check2.jpg");
   //                 System.out.println(currentFrame.getWidth()+"        "+currentFrame.getHeight()+"      "+template.getWidth()+"   "+template.getHeight());
  
                  scale(currentFrame, template, template.getWidth(),    template.getHeight());
  
                  MarvinImagePlugin diff =       MarvinPluginLoader.loadImagePlugin("org.marvinproject.image.difference.differenc     eColor.jar");
                  MarvinAttributes attr = new MarvinAttributes();
                  attr.set("total", 0);
  
  
                  System.out.println(attr.get("total"));
                  diff.process(currentFrame, template,attr);
  </code></pre>
  
  <p>The error is on the diff.process statement. The images are not null and so is the attr.</p>
  
  <p>Error statement is</p>
  
  <pre><code>Exception in thread "Thread-3" java.lang.NullPointerException
  at org.marvinproject.image.difference.differenceColor.DifferenceColor.process(DifferenceColor.java:67)
  at marvin.plugin.MarvinAbstractImagePlugin.process(MarvinAbstractImagePlugin.java:65)
  at censor_player.player$MyThread.run(player.java:142)
  </code></pre>