import ij.*;
import ij.process.*;
import ij.gui.*;
import java.awt.*;
import ij.plugin.*;

public class Gamma_Adjuster implements PlugIn {

   public void run(String arg) {
      final ImagePlus img = IJ.openImage("http://imagej.nih.gov/ij/images/clown.jpg");
      final ImageProcessor ip = img.getProcessor();
      ip.snapshot();
      DialogListener listener = new DialogListener() {
         public boolean dialogItemChanged(GenericDialog gd, AWTEvent event) {
            double gamma = gd.getNextNumber();
            ip.reset();
            ip.gamma(gamma);
            img.setProcessor(ip);
            gd.repaint();
            return true;
        }
      };
      GenericDialog gd = new GenericDialog("Gamma Adjuster");
      gd.addImage(img);
      gd.addSlider("Gamma:", 0.05, 5.0, 1);
      gd.addDialogListener(listener);
      gd.showDialog();
   }

}