public   void  createThumbnail(String imageName,
                              String thumbnailName,
                               int  maxSize,
                               boolean  preserveRatio
                              ) {

    PlanarImage image = JAI.create("fileload", imageName);
     if  (image ==  null ) {
       return ;
    }

     float  wScale = ( float ) maxSize / ( float ) image.getWidth();
     float  hScale = ( float ) maxSize / ( float ) image.getHeight();
    // If we want to preserve the aspect ratio, pick the smaller scale.
     if  (preserveRatio) {
       float  scale = Math.min(wScale, hScale);
      // Don't make the image larger than it already is.
       if  (scale >  1 . 0 ) {
        scale =  1 .0F;
      }
      wScale = scale;
      hScale = scale;
    }

    ParameterBlock pb =  new  ParameterBlock();
    pb.addSource(image);                  // The source image
    pb.add(wScale);                       // The xScale
    pb.add(hScale);                       // The yScale
    pb.add( 0 .0F);                         // The x translation
    pb.add( 0 .0F);                         // The y translation
    pb.add( new  InterpolationBilinear());  // The interpolation

    // Create the scaled image.
    PlanarImage thumb = JAI.create("scale", pb,  null );
    // Write out the image as a PNG.
    JAI.create("filestore", thumb, thumbnailName, "PNG",  null );
  }