import  com.sun.media.jai.codec.*;
 import  javax.media.jai.*;
 import  java.awt.image.*;
 import  java.awt.image.renderable.*;
 import  java.io.*;

...
    FileInputStream fis =  new  FileInputStream("c:\\sample.jpg");
    RenderedOp image = JAI.create("stream", SeekableStream.wrapInputStream(fis, false));
     int  height = image.getHeight() /  2 ;
     int  width = image.getWidth() /  2 ;
    
     int  ww = image.getWidth();
     int  hh = image.getHeight();
     float  fattX = ( float ) (width / ww);
     float  fattY = ( float ) (height / hh);

    Interpolation interp = Interpolation.getInstance(Interpolation.INTERP_BICUBIC_2);
    ParameterBlock parSC =  new  ParameterBlock();
    parSC.addSource(image);
    parSC.add(fattX);
    parSC.add(fattY);
    parSC.add( 0 .0f);
    parSC.add( 0 .0f);
    parSC.add(interp);

    RenderedOp newImage = JAI.create("scale", parSC);
    
    JAI.create("filestore", newImage, "c:\\newsample.jpg", "JPEG",  null );
...